ssh: add aes192-cbc and aes256-cbc cipher modes

Some legacy devices only offer AES-256 in CBC mode, which the package
did not implement. Register both the 192-bit and 256-bit variants of
the existing AES-CBC packet cipher so they can be enabled through a
custom Config. aes.NewCipher already handles 24- and 32-byte keys, so
both registrations reuse the existing implementation.

acme/acme.go

@@ -221,7 +221,7 @@ func (c *Client) directoryURL() string {
 
 // CreateCert was part of the old version of ACME. It is incompatible with RFC 8555.
 //
-// Deprecated: this was for the pre-RFC 8555 version of ACME. Callers should use CreateOrderCert.
+// Deprecated: this was for the pre-RFC 8555 version of ACME. Callers should use CreateCertFromOrder.
 func (c *Client) CreateCert(ctx context.Context, csr []byte, exp time.Duration, bundle bool) (der [][]byte, certURL string, err error) {
 	return nil, "", errPreRFC
 }

acme/acme_test.go

@@ -734,7 +734,7 @@ func TestTLSALPN01ChallengeCert(t *testing.T) {
 	if !acmeExts[0].Critical {
 		t.Errorf("acmeExt.Critical = %v; want true", acmeExts[0].Critical)
 	}
-	if bytes.Compare(acmeExts[0].Value, extValue) != 0 {
+	if !bytes.Equal(acmeExts[0].Value, extValue) {
 		t.Errorf("acmeExt.Value = %v; want %v", acmeExts[0].Value, extValue)
 	}
 

acme/autocert/autocert.go

@@ -248,10 +248,6 @@ func (m *Manager) TLSConfig() *tls.Config {
 // If GetCertificate is used directly, instead of via Manager.TLSConfig, package users will
 // also have to add acme.ALPNProto to NextProtos for tls-alpn-01, or use HTTPHandler for http-01.
 func (m *Manager) GetCertificate(hello *tls.ClientHelloInfo) (*tls.Certificate, error) {
-	if m.Prompt == nil {
-		return nil, errors.New("acme/autocert: Manager.Prompt not set")
-	}
-
 	name := hello.ServerName
 	if name == "" {
 		return nil, errors.New("acme/autocert: missing server name")
@@ -568,24 +564,21 @@ func encodeECDSAKey(w io.Writer, key *ecdsa.PrivateKey) error {
 // If the domain is already being verified, it waits for the existing verification to complete.
 // Either way, createCert blocks for the duration of the whole process.
 func (m *Manager) createCert(ctx context.Context, ck certKey) (*tls.Certificate, error) {
-	// TODO: maybe rewrite this whole piece using sync.Once
-	state, err := m.certState(ck)
+	state, owner, err := m.certState(ck)
 	if err != nil {
 		return nil, err
 	}
-	// state may exist if another goroutine is already working on it
-	// in which case just wait for it to finish
-	if !state.locked {
+	// If another goroutine is already working on this state, wait for it
+	// to finish by taking the read lock
+	if !owner {
 		state.RLock()
 		defer state.RUnlock()
 		return state.tlscert()
 	}
 
-	// We are the first; state is locked.
-	// Unblock the readers when domain ownership is verified
-	// and we got the cert or the process failed.
+	// We are the first to work on this certKey, so state is write-locked.
+	// Unblock the readers when our work is complete.
 	defer state.Unlock()
-	state.locked = false
 
 	der, leaf, err := m.authorizedCert(ctx, state.key, ck)
 	if err != nil {
@@ -615,10 +608,15 @@ func (m *Manager) createCert(ctx context.Context, ck certKey) (*tls.Certificate,
 	return state.tlscert()
 }
 
-// certState returns a new or existing certState.
-// If a new certState is returned, state.exist is false and the state is locked.
+// certState returns a new or existing certState along with a boolean
+// indicating whether the caller is the owner of the state.
+//
+// The owner of the state is responsible for performing the ACME work and
+// must unlock the state's write lock when done. Non-owner callers should
+// wait on the state's read lock for the owner to finish.
+//
 // The returned error is non-nil only in the case where a new state could not be created.
-func (m *Manager) certState(ck certKey) (*certState, error) {
+func (m *Manager) certState(ck certKey) (*certState, bool, error) {
 	m.stateMu.Lock()
 	defer m.stateMu.Unlock()
 	if m.state == nil {
@@ -626,7 +624,7 @@ func (m *Manager) certState(ck certKey) (*certState, error) {
 	}
 	// existing state
 	if state, ok := m.state[ck]; ok {
-		return state, nil
+		return state, false, nil
 	}
 
 	// new locked state
@@ -640,16 +638,13 @@ func (m *Manager) certState(ck certKey) (*certState, error) {
 		key, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
 	}
 	if err != nil {
-		return nil, err
+		return nil, false, err
 	}
 
-	state := &certState{
-		key:    key,
-		locked: true,
-	}
+	state := &certState{key: key}
 	state.Lock() // will be unlocked by m.certState caller
 	m.state[ck] = state
-	return state, nil
+	return state, true, nil
 }
 
 // authorizedCert starts the domain ownership verification process and requests a new cert upon success.
@@ -676,7 +671,7 @@ func (m *Manager) authorizedCert(ctx context.Context, key crypto.Signer, ck cert
 	if err != nil {
 		return nil, nil, err
 	}
-	chain, _, err := client.CreateOrderCert(ctx, o.FinalizeURL, csr, true)
+	chain, _, err := client.CreateCertFromOrder(ctx, o, csr, true)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -1039,10 +1034,9 @@ func (m *Manager) now() time.Time {
 // certState is ready when its mutex is unlocked for reading.
 type certState struct {
 	sync.RWMutex
-	locked bool              // locked for read/write
-	key    crypto.Signer     // private key for cert
-	cert   [][]byte          // DER encoding
-	leaf   *x509.Certificate // parsed cert[0]; always non-nil if cert != nil
+	key  crypto.Signer     // private key for cert
+	cert [][]byte          // DER encoding
+	leaf *x509.Certificate // parsed cert[0]; always non-nil if cert != nil
 }
 
 // tlscert creates a tls.Certificate from s.key and s.cert.

acme/autocert/autocert_test.go

@@ -201,7 +201,7 @@ func TestGetCertificate(t *testing.T) {
 			prepare: func(t *testing.T, man *Manager, s *acmetest.CAServer) {
 				man.Prompt = nil
 			},
-			expectError: "Manager.Prompt not set",
+			expectError: "missing Manager.Prompt",
 		},
 		{
 			name:   "trailingDot",
@@ -513,6 +513,33 @@ func TestGetCertificate_failedAttempt(t *testing.T) {
 	}
 }
 
+// TestGetCertificate_concurrent guards against a data race on certState
+// fields between the goroutine performing the ACME work for a domain and
+// the other goroutines waiting on the result. See golang/go#80119.
+func TestGetCertificate_concurrent(t *testing.T) {
+	// An unreachable directory URL makes the owner goroutine fail
+	// quickly inside createCert, so its writes overlap with the
+	// non-owner goroutines reaching the same code path.
+	m := &Manager{
+		Prompt: AcceptTOS,
+		Client: &acme.Client{DirectoryURL: "http://127.0.0.1:1/"},
+	}
+	defer m.stopRenew()
+
+	start := make(chan struct{})
+	var wg sync.WaitGroup
+	for i := 0; i < 64; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			<-start
+			m.GetCertificate(clientHelloInfo(exampleDomain, algECDSA))
+		}()
+	}
+	close(start)
+	wg.Wait()
+}
+
 func TestRevokeFailedAuthz(t *testing.T) {
 	ca := acmetest.NewCAServer(t)
 	// Make the authz unfulfillable on the client side, so it will be left

acme/autocert/internal/acmetest/ca.go

@@ -239,7 +239,8 @@ type discovery struct {
 }
 
 type discoveryMeta struct {
-	ExternalAccountRequired bool `json:"externalAccountRequired,omitempty"`
+	Terms                   string `json:"termsOfService,omitempty"`
+	ExternalAccountRequired bool   `json:"externalAccountRequired,omitempty"`
 }
 
 type challenge struct {
@@ -281,6 +282,7 @@ func (ca *CAServer) handle(w http.ResponseWriter, r *http.Request) {
 			NewAccount: ca.serverURL("/new-account"),
 			NewOrder:   ca.serverURL("/new-order"),
 			Meta: discoveryMeta{
+				Terms:                   ca.serverURL("/terms"),
 				ExternalAccountRequired: ca.eabRequired,
 			},
 		}

acme/autocert/renewal_test.go

@@ -180,9 +180,6 @@ func TestRenewFromCacheAlreadyRenewed(t *testing.T) {
 
 	// set internal state to an almost expired cert
 	oldCert := ca.LeafCert(exampleDomain, "ECDSA", now.Add(-2*time.Hour), now.Add(time.Minute))
-	if err != nil {
-		t.Fatal(err)
-	}
 	oldLeaf, err := validCert(exampleCertKey, oldCert.Certificate, oldCert.PrivateKey.(crypto.Signer), now)
 	if err != nil {
 		t.Fatal(err)

acme/internal/acmeprobe/prober.go

@@ -182,9 +182,9 @@ func (p *prober) runOrder(ctx context.Context, identifiers []acme.AuthzID) {
 		log.Fatalf("WaitOrder(%q): %v", o.URI, err)
 	}
 	csr, certkey := newCSR(identifiers)
-	der, curl, err := p.client.CreateOrderCert(ctx, o.FinalizeURL, csr, true)
+	der, curl, err := p.client.CreateCertFromOrder(ctx, o, csr, true)
 	if err != nil {
-		log.Fatalf("CreateOrderCert: %v", err)
+		log.Fatalf("CreateCertFromOrder: %v", err)
 	}
 	log.Printf("cert URL: %s", curl)
 	if err := checkCert(der, identifiers); err != nil {
@@ -247,9 +247,9 @@ func (p *prober) runPreauthz(ctx context.Context, identifiers []acme.AuthzID) {
 		log.Fatalf("WaitOrder(%q): %v", o.URI, err)
 	}
 	csr, certkey := newCSR(identifiers)
-	der, curl, err := p.client.CreateOrderCert(ctx, o.FinalizeURL, csr, true)
+	der, curl, err := p.client.CreateCertFromOrder(ctx, o, csr, true)
 	if err != nil {
-		log.Fatalf("CreateOrderCert: %v", err)
+		log.Fatalf("CreateCertFromOrder: %v", err)
 	}
 	log.Printf("cert URL: %s", curl)
 	if err := checkCert(der, identifiers); err != nil {

acme/jws.go

@@ -103,9 +103,7 @@ func jwsEncodeJSON(claimset interface{}, key crypto.Signer, kid KeyID, nonce, ur
 		}
 		payload = base64.RawURLEncoding.EncodeToString(cs)
 	}
-	hash := sha.New()
-	hash.Write([]byte(phead + "." + payload))
-	sig, err := jwsSign(key, sha, hash.Sum(nil))
+	sig, err := jwsSign(key, sha, []byte(phead+"."+payload))
 	if err != nil {
 		return nil, err
 	}
@@ -195,14 +193,13 @@ func jwkEncode(pub crypto.PublicKey) (string, error) {
 	return "", ErrUnsupportedKey
 }
 
-// jwsSign signs the digest using the given key.
-// The hash is unused for ECDSA keys.
-func jwsSign(key crypto.Signer, hash crypto.Hash, digest []byte) ([]byte, error) {
+// jwsSign signs the payload using the given key.
+func jwsSign(key crypto.Signer, hash crypto.Hash, payload []byte) ([]byte, error) {
 	switch pub := key.Public().(type) {
 	case *rsa.PublicKey:
-		return key.Sign(rand.Reader, digest, hash)
+		return crypto.SignMessage(key, rand.Reader, payload, hash)
 	case *ecdsa.PublicKey:
-		sigASN1, err := key.Sign(rand.Reader, digest, hash)
+		sigASN1, err := crypto.SignMessage(key, rand.Reader, payload, hash)
 		if err != nil {
 			return nil, err
 		}

acme/jws_test.go

@@ -14,6 +14,7 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"encoding/pem"
+	"errors"
 	"fmt"
 	"io"
 	"math/big"
@@ -353,6 +354,22 @@ func (s *customTestSigner) Sign(io.Reader, []byte, crypto.SignerOpts) ([]byte, e
 	return s.sig, nil
 }
 
+type customTestMessageSigner struct {
+	customTestSigner
+	msg  []byte
+	opts crypto.SignerOpts
+}
+
+func (s *customTestMessageSigner) Sign(io.Reader, []byte, crypto.SignerOpts) ([]byte, error) {
+	return nil, errors.New("customTestSigner: Sign() called instead of SignMessage()")
+}
+
+func (s *customTestMessageSigner) SignMessage(_ io.Reader, msg []byte, opts crypto.SignerOpts) ([]byte, error) {
+	s.msg = msg
+	s.opts = opts
+	return s.sig, nil
+}
+
 func TestJWSEncodeJSONCustom(t *testing.T) {
 	claims := struct{ Msg string }{"hello"}
 	const (
@@ -391,24 +408,33 @@ func TestJWSEncodeJSONCustom(t *testing.T) {
 	)
 
 	tt := []struct {
-		alg, phead    string
+		name, phead   string
 		pub           crypto.PublicKey
 		stdsig, jwsig string
+		msgSigner     bool
 	}{
-		{"ES256", es256phead, testKeyEC.Public(), es256stdsig, es256jwsig},
-		{"RS256", rs256phead, testKey.Public(), testsig, testsig},
+		{"ES256", es256phead, testKeyEC.Public(), es256stdsig, es256jwsig, false},
+		{"RS256", rs256phead, testKey.Public(), testsig, testsig, false},
+		{"ES256-MessageSigner", es256phead, testKeyEC.Public(), es256stdsig, es256jwsig, true},
+		{"RS256-MessageSigner", rs256phead, testKey.Public(), testsig, testsig, true},
 	}
 	for _, tc := range tt {
 		tc := tc
-		t.Run(tc.alg, func(t *testing.T) {
+		t.Run(tc.name, func(t *testing.T) {
 			stdsig, err := base64.RawStdEncoding.DecodeString(tc.stdsig)
 			if err != nil {
 				t.Errorf("couldn't decode test vector: %v", err)
 			}
-			signer := &customTestSigner{
+			cs := customTestSigner{
 				sig: stdsig,
 				pub: tc.pub,
 			}
+			var signer crypto.Signer = &cs
+			var ms *customTestMessageSigner
+			if tc.msgSigner {
+				ms = &customTestMessageSigner{customTestSigner: cs}
+				signer = ms
+			}
 
 			b, err := jwsEncodeJSON(claims, signer, noKeyID, "nonce", "url")
 			if err != nil {
@@ -427,6 +453,14 @@ func TestJWSEncodeJSONCustom(t *testing.T) {
 			if j.Sig != tc.jwsig {
 				t.Errorf("j.Sig = %q\nwant %q", j.Sig, tc.jwsig)
 			}
+			if ms != nil {
+				if want := tc.phead + "." + payload; string(ms.msg) != want {
+					t.Errorf("msg = %q; want %q", ms.msg, want)
+				}
+				if ms.opts != crypto.SHA256 {
+					t.Errorf("opts = %v; want %v", ms.opts, crypto.SHA256)
+				}
+			}
 		})
 	}
 }

acme/pebble_test.go

@@ -37,7 +37,7 @@ import (
 const (
 	// pebbleModVersion is the module version used for Pebble and Pebble's
 	// challenge test server. It is ignored if `-pebble-local-dir` is provided.
-	pebbleModVersion = "v2.7.0"
+	pebbleModVersion = "v2.10.1"
 	// startingPort is the first port number used for binding interface
 	// addresses. Each call to takeNextPort() will increment a port number
 	// starting at this value.
@@ -383,7 +383,7 @@ func testIssuance(t *testing.T, env *environment, challSrv challengeServer) {
 	order, err = client.WaitOrder(ctx, order.URI)
 	if err != nil {
 		var orderErr *acme.OrderError
-		if errors.Is(err, orderErr) {
+		if errors.As(err, &orderErr) {
 			t.Fatalf("failed to wait for order %s: %s: %s", orderURL, err, orderErr.Problem)
 		} else {
 			t.Fatalf("failed to wait for order %s: %s", orderURL, err)
@@ -420,7 +420,7 @@ func testIssuance(t *testing.T, env *environment, challSrv challengeServer) {
 	}
 
 	// Finalize the order by creating a certificate with our CSR.
-	chain, _, err := client.CreateOrderCert(ctx, order.FinalizeURL, csrDer, true)
+	chain, _, err := client.CreateCertFromOrder(ctx, order, csrDer, true)
 	if err != nil {
 		t.Fatalf("failed to finalize order %s with finalize URL %s: %v",
 			orderURL, order.FinalizeURL, err)
@@ -638,7 +638,7 @@ func startPebbleEnvironment(t *testing.T, config *environmentConfig) environment
 	// Note: we specify -defaultIPv6 "" so that no AAAA records are served.
 	// The LUCI CI runners have issues with IPv6 connectivity on localhost.
 	spawnServerProcess(t, binDir, "pebble-challtestsrv",
-		"-dns01", fmt.Sprintf(":%d", config.dnsPort),
+		"-dnsserver", fmt.Sprintf(":%d", config.dnsPort),
 		"-defaultIPv6", "",
 		"-management", fmt.Sprintf(":%d", takeNextPort()),
 		"-doh", "",

acme/rfc8555.go

@@ -53,6 +53,9 @@ func (c *Client) registerRFC(ctx context.Context, acct *Account, prompt func(tos
 		Contact: acct.Contact,
 	}
 	if c.dir.Terms != "" {
+		if prompt == nil {
+			return nil, errors.New("acme: missing Manager.Prompt to accept server's terms of service")
+		}
 		req.TermsAgreed = prompt(c.dir.Terms)
 	}
 
@@ -194,7 +197,7 @@ func (c *Client) accountKeyRollover(ctx context.Context, newKey crypto.Signer) e
 // identify those with StatusPending status and fulfill a challenge using Accept.
 // Once all authorizations are satisfied, the caller will typically want to poll
 // order status using WaitOrder until it's in StatusReady state.
-// To finalize the order and obtain a certificate, the caller submits a CSR with CreateOrderCert.
+// To finalize the order and obtain a certificate, the caller submits a CSR with CreateCertFromOrder.
 func (c *Client) AuthorizeOrder(ctx context.Context, id []AuthzID, opt ...OrderOption) (*Order, error) {
 	dir, err := c.Discover(ctx)
 	if err != nil {
@@ -247,7 +250,11 @@ func (c *Client) GetOrder(ctx context.Context, url string) (*Order, error) {
 		return nil, err
 	}
 	defer res.Body.Close()
-	return responseOrder(res)
+	o, err := responseOrder(res)
+	if err == nil && o.URI == "" {
+		o.URI = url
+	}
+	return o, err
 }
 
 // WaitOrder polls an order from the given URL until it is in one of the final states,
@@ -268,6 +275,9 @@ func (c *Client) WaitOrder(ctx context.Context, url string) (*Order, error) {
 		}
 		o, err := responseOrder(res)
 		res.Body.Close()
+		if err == nil && o.URI == "" {
+			o.URI = url
+		}
 		switch {
 		case err != nil:
 			// Skip and retry.
@@ -335,11 +345,43 @@ func responseOrder(res *http.Response) (*Order, error) {
 // certificate chain. Otherwise, only a leaf certificate is returned.
 // The returned URL can be used to re-fetch the certificate using FetchCert.
 //
-// This method is only supported by CAs implementing RFC 8555. See CreateCert for pre-RFC CAs.
+// This method is only supported by CAs implementing RFC 8555 that return a
+// Location header for order finalization responses. Most users should prefer
+// CreateCertFromOrder, an alternative that has better interoperation with RFC 8555
+// compliant CAs. See CreateCert for pre-RFC CAs.
 //
 // CreateOrderCert returns an error if the CA's response is unreasonably large.
 // Callers are encouraged to parse the returned value to ensure the certificate is valid and has the expected features.
 func (c *Client) CreateOrderCert(ctx context.Context, url string, csr []byte, bundle bool) (der [][]byte, certURL string, err error) {
+	return c.createOrderCert(ctx, url, "", csr, bundle)
+}
+
+// CreateCertFromOrder submits the CSR (Certificate Signing Request) to a CA for
+// the specified Order created with AuthorizeOrder.
+//
+// If the bundle argument is true, the returned value also contain the CA (issuer)
+// certificate chain. Otherwise, only a leaf certificate is returned.
+// The returned URL can be used to re-fetch the certificate using FetchCert.
+//
+// This method is only supported by CAs implementing RFC 8555.
+// See CreateCert for pre-RFC CAs.
+//
+// CreateCertFromOrder returns an error if the CA's response is unreasonably large.
+// Callers are encouraged to parse the returned value to ensure the certificate is valid and has the expected features.
+func (c *Client) CreateCertFromOrder(ctx context.Context, order *Order, csr []byte, bundle bool) (der [][]byte, certURL string, err error) {
+	if order == nil {
+		return nil, "", errors.New("acme: nil order")
+	}
+	if order.URI == "" {
+		return nil, "", errors.New("acme: order URI is empty")
+	}
+	if order.FinalizeURL == "" {
+		return nil, "", errors.New("acme: order finalize URL is empty")
+	}
+	return c.createOrderCert(ctx, order.FinalizeURL, order.URI, csr, bundle)
+}
+
+func (c *Client) createOrderCert(ctx context.Context, finalizeURL, orderURL string, csr []byte, bundle bool) (der [][]byte, certURL string, err error) {
 	if _, err := c.Discover(ctx); err != nil { // required by c.accountKID
 		return nil, "", err
 	}
@@ -350,7 +392,7 @@ func (c *Client) CreateOrderCert(ctx context.Context, url string, csr []byte, bu
 	}{
 		CSR: base64.RawURLEncoding.EncodeToString(csr),
 	}
-	res, err := c.post(ctx, nil, url, req, wantStatus(http.StatusOK))
+	res, err := c.post(ctx, nil, finalizeURL, req, wantStatus(http.StatusOK))
 	if err != nil {
 		return nil, "", err
 	}
@@ -362,7 +404,10 @@ func (c *Client) CreateOrderCert(ctx context.Context, url string, csr []byte, bu
 
 	// Wait for CA to issue the cert if they haven't.
 	if o.Status != StatusValid {
-		o, err = c.WaitOrder(ctx, o.URI)
+		if orderURL == "" {
+			orderURL = o.URI
+		}
+		o, err = c.WaitOrder(ctx, orderURL)
 	}
 	if err != nil {
 		return nil, "", err

acme/rfc8555_test.go

@@ -979,6 +979,80 @@ func TestRFC_CreateOrderCert(t *testing.T) {
 	}
 }
 
+// TestRFC_CreateCertFromOrder tests that finalization responses work even when
+// they omit a Location header. Such a header isn't required by RFC 8555 in this
+// context and we should be able to complete an order without needing it.
+func TestRFC_CreateCertFromOrder(t *testing.T) {
+	q := &x509.CertificateRequest{
+		Subject: pkix.Name{CommonName: "example.org"},
+	}
+	csr, err := x509.CreateCertificateRequest(rand.Reader, q, testKeyEC)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tmpl := &x509.Certificate{SerialNumber: big.NewInt(1)}
+	leaf, err := x509.CreateCertificate(rand.Reader, tmpl, tmpl, &testKeyEC.PublicKey, testKeyEC)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	s := newACMEServer()
+	s.handle("/acme/new-account", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Location", s.url("/accounts/1"))
+		w.Write([]byte(`{"status": "valid"}`))
+	})
+	s.handle("/finalize", func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprint(w, `{"status":"processing"}`)
+	})
+	s.handle("/orders/1", func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprintf(w, `{"status":"valid", "certificate":%q}`, s.url("/crt"))
+	})
+	s.handle("/crt", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/pem-certificate-chain")
+		pem.Encode(w, &pem.Block{Type: "CERTIFICATE", Bytes: leaf})
+	})
+	s.start()
+	defer s.close()
+
+	cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")}
+	order := &Order{URI: s.url("/orders/1"), FinalizeURL: s.url("/finalize")}
+	cert, curl, err := cl.CreateCertFromOrder(context.Background(), order, csr, true)
+	if err != nil {
+		t.Fatalf("CreateCertFromOrder: %v", err)
+	}
+	if _, err := x509.ParseCertificate(cert[0]); err != nil {
+		t.Errorf("ParseCertificate: %v", err)
+	}
+	if !reflect.DeepEqual(cert[0], leaf) {
+		t.Errorf("cert and leaf bytes don't match")
+	}
+	if u := s.url("/crt"); curl != u {
+		t.Errorf("curl = %q; want %q", curl, u)
+	}
+}
+
+// TestRFC_CreateCertFromOrderInvalidOrder tests that invalid CreateCertFromOrder
+// calls fail before making a request.
+func TestRFC_CreateCertFromOrderInvalidOrder(t *testing.T) {
+	cl := new(Client)
+	tests := []struct {
+		name  string
+		order *Order
+	}{
+		{"nil", nil},
+		{"empty URI", &Order{FinalizeURL: "https://example.com/finalize"}},
+		{"empty finalize URL", &Order{URI: "https://example.com/order/1"}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if _, _, err := cl.CreateCertFromOrder(context.Background(), tt.order, nil, false); err == nil {
+				t.Fatal("CreateCertFromOrder returned nil error")
+			}
+		})
+	}
+}
+
 func TestRFC_AlreadyRevokedCert(t *testing.T) {
 	s := newACMEServer()
 	s.handle("/acme/revoke-cert", func(w http.ResponseWriter, r *http.Request) {

acme/types.go

@@ -114,14 +114,15 @@ type Error struct {
 }
 
 func (e *Error) Error() string {
-	str := fmt.Sprintf("%d %s: %s", e.StatusCode, e.ProblemType, e.Detail)
+	var sb strings.Builder
+	fmt.Fprintf(&sb, "%d %s: %s", e.StatusCode, e.ProblemType, e.Detail)
 	if len(e.Subproblems) > 0 {
-		str += fmt.Sprintf("; subproblems:")
+		sb.WriteString("; subproblems:")
 		for _, sp := range e.Subproblems {
-			str += fmt.Sprintf("\n\t%s", sp)
+			fmt.Fprintf(&sb, "\n\t%s", sp)
 		}
 	}
-	return str
+	return sb.String()
 }
 
 // AuthorizationError indicates that an authorization for an identifier
@@ -167,7 +168,11 @@ type OrderError struct {
 }
 
 func (oe *OrderError) Error() string {
-	return fmt.Sprintf("acme: order %s status: %s", oe.OrderURL, oe.Status)
+	str := fmt.Sprintf("acme: order %s status: %s", oe.OrderURL, oe.Status)
+	if oe.Problem != nil {
+		str += fmt.Sprintf("; problem: %s", oe.Problem)
+	}
+	return str
 }
 
 // RateLimit reports whether err represents a rate limit error and
@@ -325,7 +330,7 @@ type Order struct {
 	// Possible values are StatusPending, StatusReady, StatusProcessing, StatusValid and StatusInvalid.
 	// Pending means the CA does not believe that the client has fulfilled the requirements.
 	// Ready indicates that the client has fulfilled all the requirements and can submit a CSR
-	// to obtain a certificate. This is done with Client's CreateOrderCert.
+	// to obtain a certificate. This is done with Client's CreateCertFromOrder.
 	// Processing means the certificate is being issued.
 	// Valid indicates the CA has issued the certificate. It can be downloaded
 	// from the Order's CertURL. This is done with Client's FetchCert.

acme/types_test.go

@@ -217,3 +217,19 @@ func TestErrorStringerWithSubproblems(t *testing.T) {
 		t.Errorf("Unexpected error string: wanted %q, got %q", expectedStr, err.Error())
 	}
 }
+
+func TestOrderErrorProblem(t *testing.T) {
+	oe := &OrderError{
+		OrderURL: "url",
+		Status:   "invalid",
+		Problem: &Error{
+			StatusCode:  400,
+			ProblemType: "type",
+			Detail:      "detail",
+		},
+	}
+	want := "acme: order url status: invalid; problem: 400 type: detail"
+	if got := oe.Error(); got != want {
+		t.Errorf("oe.Error() = %q, want %q", got, want)
+	}
+}

argon2/argon2.go

@@ -17,8 +17,8 @@
 // It uses data-independent memory access, which is preferred for password
 // hashing and password-based key derivation. Argon2i requires more passes over
 // memory than Argon2id to protect from trade-off attacks. The recommended
-// parameters (taken from [RFC 9106 Section 7.3]) for non-interactive operations are time=3 and to
-// use the maximum available memory.
+// parameters (taken from [RFC 9106 Section 7.3]) for non-interactive
+// operations are time=3 and to use the maximum available memory.
 //
 // # Argon2id
 //
@@ -26,11 +26,14 @@
 // Argon2i and Argon2d. It uses data-independent memory access for the first
 // half of the first iteration over the memory and data-dependent memory access
 // for the rest. Argon2id is side-channel resistant and provides better brute-
-// force cost savings due to time-memory tradeoffs than Argon2i. The recommended
-// parameters for non-interactive operations (taken from [RFC 9106 Section 7.3]) are time=1 and to
-// use the maximum available memory.
+// force cost savings due to time-memory tradeoffs than Argon2i. [RFC 9106
+// Section 4] recommends time=1, memory=2*1024*1024 KiB (2 GiB), and threads=4
+// as the first recommended option. If much less memory is available, it
+// recommends time=3, memory=64*1024 KiB (64 MiB), and threads=4 as the second
+// recommended option.
 //
 // [argon2-specs.pdf]: https://github.com/P-H-C/phc-winner-argon2/blob/master/argon2-specs.pdf
+// [RFC 9106 Section 4]: https://www.rfc-editor.org/rfc/rfc9106.html#section-4
 // [RFC 9106 Section 7.3]: https://www.rfc-editor.org/rfc/rfc9106.html#section-7.3
 package argon2
 
@@ -59,9 +62,9 @@ const (
 //
 //	key := argon2.Key([]byte("some password"), salt, 3, 32*1024, 4, 32)
 //
-// [RFC 9106 Section 7.3] recommends time=3, and memory=32*1024 as a sensible number.
-// If using that amount of memory (32 MB) is not possible in some contexts then
-// the time parameter can be increased to compensate.
+// The example above uses time=3 and memory=32*1024. Argon2i generally
+// requires more passes over memory than Argon2id. If in doubt, prefer IDKey
+// and its Argon2id parameter recommendations.
 //
 // The time parameter specifies the number of passes over the memory and the
 // memory parameter specifies the size of the memory in KiB. For example
@@ -69,8 +72,6 @@ const (
 // adjusted to the number of available CPUs. The cost parameters should be
 // increased as memory latency and CPU parallelism increases. Remember to get a
 // good random salt.
-//
-// [RFC 9106 Section 7.3]: https://www.rfc-editor.org/rfc/rfc9106.html#section-7.3
 func Key(password, salt []byte, time, memory uint32, threads uint8, keyLen uint32) []byte {
 	return deriveKey(argon2i, password, salt, nil, nil, time, memory, threads, keyLen)
 }
@@ -83,20 +84,20 @@ func Key(password, salt []byte, time, memory uint32, threads uint8, keyLen uint3
 // For example, you can get a derived key for e.g. AES-256 (which needs a
 // 32-byte key) by doing:
 //
-//	key := argon2.IDKey([]byte("some password"), salt, 1, 64*1024, 4, 32)
+//	key := argon2.IDKey([]byte("some password"), salt, 1, 2*1024*1024, 4, 32)
 //
-// [RFC 9106 Section 7.3] recommends time=1, and memory=64*1024 as a sensible number.
-// If using that amount of memory (64 MB) is not possible in some contexts then
-// the time parameter can be increased to compensate.
+// The example above uses the first [RFC 9106 Section 4] recommended option.
+// If much less memory is available, the second recommended option is time=3,
+// memory=64*1024 KiB (64 MiB), and threads=4.
 //
 // The time parameter specifies the number of passes over the memory and the
 // memory parameter specifies the size of the memory in KiB. For example
-// memory=64*1024 sets the memory cost to ~64 MB. The number of threads can be
-// adjusted to the numbers of available CPUs. The cost parameters should be
+// memory=2*1024*1024 sets the memory cost to ~2 GiB. The number of threads can
+// be adjusted to the numbers of available CPUs. The cost parameters should be
 // increased as memory latency and CPU parallelism increases. Remember to get a
 // good random salt.
 //
-// [RFC 9106 Section 7.3]: https://www.rfc-editor.org/rfc/rfc9106.html#section-7.3
+// [RFC 9106 Section 4]: https://www.rfc-editor.org/rfc/rfc9106.html#section-4
 func IDKey(password, salt []byte, time, memory uint32, threads uint8, keyLen uint32) []byte {
 	return deriveKey(argon2id, password, salt, nil, nil, time, memory, threads, keyLen)
 }

argon2/argon2_test.go

@@ -24,6 +24,7 @@ var (
 
 func TestArgon2(t *testing.T) {
 	defer func(sse4 bool) { useSSE4 = sse4 }(useSSE4)
+	defer func(lsx bool) { useLSX = lsx }(useLSX)
 
 	if useSSE4 {
 		t.Log("SSE4.1 version")
@@ -32,6 +33,14 @@ func TestArgon2(t *testing.T) {
 		testArgon2id(t)
 		useSSE4 = false
 	}
+
+	if useLSX {
+		t.Log("LSX version")
+		testArgon2i(t)
+		testArgon2d(t)
+		testArgon2id(t)
+		useLSX = false
+	}
 	t.Log("generic version")
 	testArgon2i(t)
 	testArgon2d(t)

argon2/blamka_generic.go

@@ -6,6 +6,10 @@ package argon2
 
 var useSSE4 bool
 
+// useLSX reports whether the loong64 LSX vector implementation should be
+// used. It is set from cpu.Loong64.HasLSX in blamka_loong64.go's init().
+var useLSX bool
+
 func processBlockGeneric(out, in1, in2 *block, xor bool) {
 	var t block
 	for i := range t {

argon2/blamka_loong64.go

@@ -0,0 +1,49 @@
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build loong64 && gc && !purego
+
+package argon2
+
+import "golang.org/x/sys/cpu"
+
+func init() {
+	// useLSX (declared in blamka_generic.go) gates the LSX vector path.
+	// If the running CPU lacks LSX support, processBlockVX falls back
+	// to processBlockGeneric.
+	useLSX = cpu.Loong64.HasLSX
+}
+
+//go:noescape
+func blamkaLOONG64(b *block)
+
+//go:noescape
+func mixBlocksVX(out, a, b, c *block)
+
+//go:noescape
+func xorBlocksVX(out, a, b, c *block)
+
+func processBlock(out, in1, in2 *block) {
+	processBlockVX(out, in1, in2, false)
+}
+
+func processBlockXOR(out, in1, in2 *block) {
+	processBlockVX(out, in1, in2, true)
+}
+
+func processBlockVX(out, in1, in2 *block, xor bool) {
+	if !useLSX {
+		processBlockGeneric(out, in1, in2, xor)
+		return
+	}
+
+	var t block
+	mixBlocksVX(&t, in1, in2, &t)
+	blamkaLOONG64(&t)
+	if xor {
+		xorBlocksVX(out, in1, in2, &t)
+	} else {
+		mixBlocksVX(out, in1, in2, &t)
+	}
+}

argon2/blamka_loong64.s

@@ -0,0 +1,240 @@
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build loong64 && gc && !purego
+
+#include "textflag.h"
+
+// HALF_ROUND applies one BlaMka half-round (mul-add-xor-rotate) to two
+// groups of 4 columns, each packed 2-wide into V registers (v0/v2/v4/v6
+// hold one pair of columns in lane0/lane1, v1/v3/v5/v7 hold the other).
+// t0, t1 are scratch registers, one per independent column group.
+#define HALF_ROUND(v0, v1, v2, v3, v4, v5, v6, v7, t0, t1) \
+	VMULWEVVWU	v0, v2, t0; \
+	VADDV		t0, t0, t0; \
+	VADDV		v0, v2, v0; \
+	VADDV		v0, t0, v0; \
+	VXORV		v6, v0, v6; \
+	VROTRV		$32, v6, v6; \
+	VMULWEVVWU	v1, v3, t1; \
+	VADDV		t1, t1, t1; \
+	VADDV		v1, v3, v1; \
+	VADDV		v1, t1, v1; \
+	VXORV		v7, v1, v7; \
+	VROTRV		$32, v7, v7; \
+	VMULWEVVWU	v4, v6, t0; \
+	VADDV		t0, t0, t0; \
+	VADDV		v4, v6, v4; \
+	VADDV		v4, t0, v4; \
+	VXORV		v2, v4, v2; \
+	VROTRV		$24, v2, v2; \
+	VMULWEVVWU	v5, v7, t1; \
+	VADDV		t1, t1, t1; \
+	VADDV		v5, v7, v5; \
+	VADDV		v5, t1, v5; \
+	VXORV		v3, v5, v3; \
+	VROTRV		$24, v3, v3; \
+	VMULWEVVWU	v0, v2, t0; \
+	VADDV		t0, t0, t0; \
+	VADDV		v0, v2, v0; \
+	VADDV		v0, t0, v0; \
+	VXORV		v6, v0, v6; \
+	VROTRV		$16, v6, v6; \
+	VMULWEVVWU	v1, v3, t1; \
+	VADDV		t1, t1, t1; \
+	VADDV		v1, v3, v1; \
+	VADDV		v1, t1, v1; \
+	VXORV		v7, v1, v7; \
+	VROTRV		$16, v7, v7; \
+	VMULWEVVWU	v4, v6, t0; \
+	VADDV		t0, t0, t0; \
+	VADDV		v4, v6, v4; \
+	VADDV		v4, t0, v4; \
+	VXORV		v2, v4, v2; \
+	VROTRV		$63, v2, v2; \
+	VMULWEVVWU	v5, v7, t1; \
+	VADDV		t1, t1, t1; \
+	VADDV		v5, v7, v5; \
+	VADDV		v5, t1, v5; \
+	VXORV		v3, v5, v3; \
+	VROTRV		$63, v3, v3
+
+// SHUFFLE / SHUFFLE_INV: reused verbatim from blake2b_loong64.s -- amd64
+// avo source confirms argon2's SHUFFLE/SHUFFLE_INV and blake2b's SHUFFLE
+// are byte-for-byte identical macros (diagonalize / undiagonalize),
+// operating only on V2..V7 (V0/V1 untouched), with V13 held at zero.
+#define SHUFFLE \
+	VADDV		V2, V13, V12; \
+	VADDV		V6, V13, V16; \
+	VADDV		V4, V13, V14; \
+	VADDV		V5, V13, V4; \
+	VADDV		V14, V13, V5; \
+	VSHUF4IV	$9, V3, V2; \
+	VSHUF4IV	$9, V12, V3; \
+	VSHUF4IV	$3, V7, V6; \
+	VSHUF4IV	$3, V16, V7
+
+#define SHUFFLE_INV \
+	VADDV		V2, V13, V12; \
+	VADDV		V6, V13, V16; \
+	VADDV		V4, V13, V14; \
+	VADDV		V5, V13, V4; \
+	VADDV		V14, V13, V5; \
+	VSHUF4IV	$3, V3, V2; \
+	VSHUF4IV	$3, V12, V3; \
+	VSHUF4IV	$9, V7, V6; \
+	VSHUF4IV	$9, V16, V7
+
+// LOAD_MSG_0 / STORE_MSG_0: row pass. `off` is the byte offset of the
+// 128-byte (16-uint64) row group; within the macro the 8 loads step by
+// 16B (2 uint64 per V register). Called from blamkaLOONG64 with off
+// stepping by 128B across the 8 row groups -- do not confuse the two
+// strides.
+#define LOAD_MSG_0(off) \
+	VMOVQ	(off+0)(R4), V0; \
+	VMOVQ	(off+16)(R4), V1; \
+	VMOVQ	(off+32)(R4), V2; \
+	VMOVQ	(off+48)(R4), V3; \
+	VMOVQ	(off+64)(R4), V4; \
+	VMOVQ	(off+80)(R4), V5; \
+	VMOVQ	(off+96)(R4), V6; \
+	VMOVQ	(off+112)(R4), V7
+
+#define STORE_MSG_0(off) \
+	VMOVQ	V0, (off+0)(R4); \
+	VMOVQ	V1, (off+16)(R4); \
+	VMOVQ	V2, (off+32)(R4); \
+	VMOVQ	V3, (off+48)(R4); \
+	VMOVQ	V4, (off+64)(R4); \
+	VMOVQ	V5, (off+80)(R4); \
+	VMOVQ	V6, (off+96)(R4); \
+	VMOVQ	V7, (off+112)(R4)
+
+// LOAD_MSG_1 / STORE_MSG_1: diagonal pass. `off` is the byte offset within
+// a 128-byte row group; within the macro the 8 loads step by 128B (one
+// element from each of the 8 row groups, mirroring blamka_generic.go's
+// t[off], t[128+off], t[256+off], ...). Called from blamkaLOONG64 with
+// off stepping by 16B (2 uint64) across the 8 diagonal groups -- the
+// inner/outer strides are swapped relative to LOAD_MSG_0/STORE_MSG_0.
+#define LOAD_MSG_1(off) \
+	VMOVQ	(off+0)(R4), V0; \
+	VMOVQ	(off+128)(R4), V1; \
+	VMOVQ	(off+256)(R4), V2; \
+	VMOVQ	(off+384)(R4), V3; \
+	VMOVQ	(off+512)(R4), V4; \
+	VMOVQ	(off+640)(R4), V5; \
+	VMOVQ	(off+768)(R4), V6; \
+	VMOVQ	(off+896)(R4), V7
+
+#define STORE_MSG_1(off) \
+	VMOVQ	V0, (off+0)(R4); \
+	VMOVQ	V1, (off+128)(R4); \
+	VMOVQ	V2, (off+256)(R4); \
+	VMOVQ	V3, (off+384)(R4); \
+	VMOVQ	V4, (off+512)(R4); \
+	VMOVQ	V5, (off+640)(R4); \
+	VMOVQ	V6, (off+768)(R4); \
+	VMOVQ	V7, (off+896)(R4)
+
+// BLAMKA_ROUND_0(off): one full row pass over the 16-uint64 group at
+// byte offset off -- corresponds to a single call to blamkaGeneric
+// with the "row" argument order (t[off]..t[off+15]).
+#define BLAMKA_ROUND_0(off) \
+	LOAD_MSG_0(off); \
+	HALF_ROUND(V0, V1, V2, V3, V4, V5, V6, V7, V8, V9); \
+	SHUFFLE; \
+	HALF_ROUND(V0, V1, V2, V3, V4, V5, V6, V7, V8, V9); \
+	SHUFFLE_INV; \
+	STORE_MSG_0(off)
+
+// BLAMKA_ROUND_1(off): one full diagonal pass over the 16 uint64s at
+// diagonal offset off -- corresponds to a single call to blamkaGeneric
+// with the "diagonal" argument order (t[off], t[off+1], t[16+off], ...).
+#define BLAMKA_ROUND_1(off) \
+	LOAD_MSG_1(off); \
+	HALF_ROUND(V0, V1, V2, V3, V4, V5, V6, V7, V8, V9); \
+	SHUFFLE; \
+	HALF_ROUND(V0, V1, V2, V3, V4, V5, V6, V7, V8, V9); \
+	SHUFFLE_INV; \
+	STORE_MSG_1(off)
+
+// func blamkaLOONG64(b *block)
+TEXT ·blamkaLOONG64(SB), NOSPLIT, $0-8
+	MOVV	b+0(FP), R4
+
+	VXORV	V13, V13, V13	// V13 = 0, used by SHUFFLE/SHUFFLE_INV
+
+	// Round 0: 8 row passes, stride 128 bytes (16 uint64s).
+	BLAMKA_ROUND_0(0)
+	BLAMKA_ROUND_0(128)
+	BLAMKA_ROUND_0(256)
+	BLAMKA_ROUND_0(384)
+	BLAMKA_ROUND_0(512)
+	BLAMKA_ROUND_0(640)
+	BLAMKA_ROUND_0(768)
+	BLAMKA_ROUND_0(896)
+
+	// Round 1: 8 diagonal passes, stride 16 bytes (2 uint64s).
+	BLAMKA_ROUND_1(0)
+	BLAMKA_ROUND_1(16)
+	BLAMKA_ROUND_1(32)
+	BLAMKA_ROUND_1(48)
+	BLAMKA_ROUND_1(64)
+	BLAMKA_ROUND_1(80)
+	BLAMKA_ROUND_1(96)
+	BLAMKA_ROUND_1(112)
+
+	RET
+
+// func mixBlocksVX(out, a, b, c *block)
+TEXT ·mixBlocksVX(SB), NOSPLIT, $0-32
+	MOVV	out+0(FP), R4
+	MOVV	a+8(FP), R5
+	MOVV	b+16(FP), R6
+	MOVV	c+24(FP), R7
+	MOVV	$1024, R8
+
+	PCALIGN $16
+mixloop:
+	VMOVQ	(R5), V0
+	VMOVQ	(R6), V1
+	VMOVQ	(R7), V2
+	VXORV	V0, V1, V0
+	VXORV	V0, V2, V0
+	VMOVQ	V0, (R4)
+	ADDV	$16, R4
+	ADDV	$16, R5
+	ADDV	$16, R6
+	ADDV	$16, R7
+	SUBV	$16, R8
+	BNE	R8, R0, mixloop
+
+	RET
+
+// func xorBlocksVX(out, a, b, c *block)
+TEXT ·xorBlocksVX(SB), NOSPLIT, $0-32
+	MOVV	out+0(FP), R4
+	MOVV	a+8(FP), R5
+	MOVV	b+16(FP), R6
+	MOVV	c+24(FP), R7
+	MOVV	$1024, R8
+
+	PCALIGN $16
+xorloop:
+	VMOVQ	(R5), V0
+	VMOVQ	(R6), V1
+	VMOVQ	(R7), V2
+	VMOVQ	(R4), V3
+	VXORV	V0, V1, V0
+	VXORV	V0, V2, V0
+	VXORV	V0, V3, V0
+	VMOVQ	V0, (R4)
+	ADDV	$16, R4
+	ADDV	$16, R5
+	ADDV	$16, R6
+	ADDV	$16, R7
+	SUBV	$16, R8
+	BNE	R8, R0, xorloop
+
+	RET

argon2/blamka_ref.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !amd64 || purego || !gc
+//go:build (!amd64 && !loong64) || purego || !gc
 
 package argon2
 

blake2b/blake2b_loong64.go

@@ -0,0 +1,20 @@
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build loong64 && gc && !purego
+
+package blake2b
+
+import "golang.org/x/sys/cpu"
+
+//go:noescape
+func hashBlocksVX(h *[8]uint64, c *[2]uint64, flag uint64, blocks []byte)
+
+func hashBlocks(h *[8]uint64, c *[2]uint64, flag uint64, blocks []byte) {
+	if cpu.Loong64.HasLSX {
+		hashBlocksVX(h, c, flag, blocks)
+	} else {
+		hashBlocksGeneric(h, c, flag, blocks)
+	}
+}

blake2b/blake2b_loong64.s

@@ -0,0 +1,252 @@
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build loong64 && gc && !purego
+
+#include "textflag.h"
+
+DATA ·iv0<>+0(SB)/8, $0x6a09e667f3bcc908
+DATA ·iv0<>+8(SB)/8, $0xbb67ae8584caa73b
+GLOBL ·iv0<>(SB), RODATA|NOPTR, $16
+
+DATA ·iv1<>+0(SB)/8, $0x3c6ef372fe94f82b
+DATA ·iv1<>+8(SB)/8, $0xa54ff53a5f1d36f1
+GLOBL ·iv1<>(SB), RODATA|NOPTR, $16
+
+DATA ·iv2<>+0(SB)/8, $0x510e527fade682d1
+DATA ·iv2<>+8(SB)/8, $0x9b05688c2b3e6c1f
+GLOBL ·iv2<>(SB), RODATA|NOPTR, $16
+
+DATA ·iv3<>+0(SB)/8, $0x1f83d9abfb41bd6b
+DATA ·iv3<>+8(SB)/8, $0x5be0cd19137e2179
+GLOBL ·iv3<>(SB), RODATA|NOPTR, $16
+
+#define SHUFFLE_1 \
+	VADDV		V2, V13, V12; \	// V12 = V2
+	VADDV		V6, V13, V16; \	// V16 = V6
+	VADDV		V4, V13, V14; \	// V14 = V4
+	VADDV		V5, V13, V4; \	// V4 = V5
+	VADDV		V14, V13, V5; \	// V5 = V4
+	VSHUF4IV	$9, V3, V2; \
+	VSHUF4IV	$9, V12, V3; \
+	VSHUF4IV	$3, V7, V6; \
+	VSHUF4IV	$3, V16, V7; \
+
+#define SHUFFLE_2 \
+	VADDV		V2, V13, V12; \	// V12 = V2
+	VADDV		V6, V13, V16; \	// V16 = V6
+	VADDV		V4, V13, V14; \	// V14 = V4
+	VADDV		V5, V13, V4; \	// V4 = V5
+	VADDV		V14, V13, V5; \	// V5 = V4
+	VSHUF4IV	$3, V3, V2; \
+	VSHUF4IV	$3, V12, V3; \
+	VSHUF4IV	$9, V7, V6; \
+	VSHUF4IV	$9, V16, V7; \
+
+#define LOAD_M(a, b, c, d, e, f, g, h) \
+	VMOVQ	a, V8.V[0]; \
+	VMOVQ	b, V8.V[1]; \
+	VMOVQ	c, V9.V[0]; \
+	VMOVQ	d, V9.V[1]; \
+	VMOVQ	e, V10.V[0]; \
+	VMOVQ	f, V10.V[1]; \
+	VMOVQ	g, V11.V[0]; \
+	VMOVQ	h, V11.V[1]; \
+
+#define ROUND_0 \
+	VADDV	V0, V8, V0; \
+	VADDV	V1, V9, V1; \
+	VADDV	V0, V2, V0; \
+	VADDV	V1, V3, V1; \
+	VXORV	V6, V0, V6; \
+	VXORV	V7, V1, V7; \
+	VROTRV	$32, V6, V6; \
+	VROTRV	$32, V7, V7; \
+	VADDV	V4, V6, V4; \
+	VADDV	V5, V7, V5; \
+	VXORV	V2, V4, V2; \
+	VXORV	V3, V5, V3; \
+	VROTRV	$24, V2, V2; \
+	VROTRV	$24, V3, V3; \
+	VADDV	V0, V10, V0; \
+	VADDV	V1, V11, V1; \
+	VADDV	V0, V2, V0; \
+	VADDV	V1, V3, V1; \
+	VXORV	V6, V0, V6; \
+	VXORV	V7, V1, V7; \
+	VROTRV	$16, V6, V6; \
+	VROTRV	$16, V7, V7; \
+	VADDV	V4, V6, V4; \
+	VADDV	V5, V7, V5; \
+	VXORV	V2, V4, V2; \
+	VXORV	V3, V5, V3; \
+	VROTRV	$63, V2, V2; \
+	VROTRV	$63, V3, V3; \
+
+#define ROUND_8	ROUND_0
+
+// func hashBlocksVX(h *[8]uint64, c *[2]uint64, flag uint64, blocks []byte)
+TEXT ·hashBlocksVX(SB), NOSPLIT, $0-48
+	MOVV	h+0(FP), R4
+	MOVV	c+8(FP), R5
+	MOVV	flag+16(FP), R6
+	MOVV	blocks_base+24(FP), R7
+	MOVV	blocks_len+32(FP), R8
+	MOVV	(R5), R9	// c0
+	MOVV	8(R5), R10	// c1
+
+loop:
+	ADDV	$0x80, R9
+	SGTU	$0x80, R9, R11
+	ADDV	R10, R11, R10
+	VMOVQ	R9, V8.V[0]
+	VMOVQ	R10, V8.V[1]
+
+	MOVV	$·iv0<>(SB), R11
+	MOVV	$·iv1<>(SB), R12
+	MOVV	$·iv2<>(SB), R13
+	MOVV	$·iv3<>(SB), R14
+	VMOVQ	(R13), V6
+	VMOVQ	(R11), V4
+	VMOVQ	(R12), V5
+	MOVV	(R14), R15	// v14
+	MOVV	8(R14), R16
+	VXORV	V6, V8, V6
+	XOR	R15, R6, R15
+	VMOVQ	R16, V7.V[1]
+	VMOVQ	R15, V7.V[0]
+
+	VMOVQ	(R4), V0
+	VMOVQ	16(R4), V1
+	VMOVQ	32(R4), V2
+	VMOVQ	48(R4), V3
+
+	MOVV	0(R7), R11
+	MOVV	8(R7), R12
+	MOVV	16(R7), R13
+	MOVV	24(R7), R14
+	MOVV	32(R7), R15
+	MOVV	40(R7), R16
+	MOVV	48(R7), R17
+	MOVV	56(R7), R18
+	MOVV	64(R7), R19
+	MOVV	72(R7), R24
+	MOVV	80(R7), R25
+	MOVV	88(R7), R26
+	MOVV	96(R7), R27
+	MOVV	104(R7), R28
+	MOVV	112(R7), R29
+	MOVV	120(R7), R30
+
+	VXORV	V13, V13, V13	// V13=0
+
+	LOAD_M(R11, R13, R15, R17, R12, R14, R16, R18)
+	ROUND_0
+	SHUFFLE_1
+	LOAD_M(R19, R25, R27, R29, R24, R26, R28, R30)
+	ROUND_8
+	SHUFFLE_2
+
+	LOAD_M(R29, R15, R24, R28, R25, R19, R30, R17)
+	ROUND_0
+	SHUFFLE_1
+	LOAD_M(R12, R11, R26, R16, R27, R13, R18, R14)
+	ROUND_8
+	SHUFFLE_2
+
+	LOAD_M(R26, R27, R16, R30, R19, R11, R13, R28)
+	ROUND_0
+	SHUFFLE_1
+	LOAD_M(R25, R14, R18, R24, R29, R17, R12, R15)
+	ROUND_8
+	SHUFFLE_2
+
+	LOAD_M(R18, R14, R28, R26, R24, R12, R27, R29)
+	ROUND_0
+	SHUFFLE_1
+	LOAD_M(R13, R16, R15, R30, R17, R25, R11, R19)
+	ROUND_8
+	SHUFFLE_2
+
+	LOAD_M(R24, R16, R13, R25, R11, R18, R15, R30)
+	ROUND_0
+	SHUFFLE_1
+	LOAD_M(R29, R26, R17, R14, R12, R27, R19, R28)
+	ROUND_8
+	SHUFFLE_2
+
+	LOAD_M(R13, R17, R11, R19, R27, R25, R26, R14)
+	ROUND_0
+	SHUFFLE_1
+	LOAD_M(R15, R18, R30, R12, R28, R16, R29, R24)
+	ROUND_8
+	SHUFFLE_2
+
+	LOAD_M(R27, R12, R29, R15, R16, R30, R28, R25)
+	ROUND_0
+	SHUFFLE_1
+	LOAD_M(R11, R17, R24, R19, R18, R14, R13, R26)
+	ROUND_8
+	SHUFFLE_2
+
+	LOAD_M(R28, R18, R27, R14, R26, R29, R12, R24)
+	ROUND_0
+	SHUFFLE_1
+	LOAD_M(R16, R30, R19, R13, R11, R15, R17, R25)
+	ROUND_8
+	SHUFFLE_2
+
+	LOAD_M(R17, R29, R26, R11, R30, R24, R14, R19)
+	ROUND_0
+	SHUFFLE_1
+	LOAD_M(R27, R28, R12, R25, R13, R18, R15, R16)
+	ROUND_8
+	SHUFFLE_2
+
+	LOAD_M(R25, R19, R18, R12, R13, R15, R17, R16)
+	ROUND_0
+	SHUFFLE_1
+	LOAD_M(R30, R24, R14, R28, R26, R29, R27, R11)
+	ROUND_8
+	SHUFFLE_2
+
+	LOAD_M(R11, R13, R15, R17, R12, R14, R16, R18)
+	ROUND_0
+	SHUFFLE_1
+	LOAD_M(R19, R25, R27, R29, R24, R26, R28, R30)
+	ROUND_8
+	SHUFFLE_2
+
+	LOAD_M(R29, R15, R24, R28, R25, R19, R30, R17)
+	ROUND_0
+	SHUFFLE_1
+	LOAD_M(R12, R11, R26, R16, R27, R13, R18, R14)
+	ROUND_8
+	SHUFFLE_2
+
+	VMOVQ	(R4), V8
+	VMOVQ	16(R4), V9
+	VMOVQ	32(R4), V10
+	VMOVQ	48(R4), V11
+	VXORV	V0, V4, V0
+	VXORV	V1, V5, V1
+	VXORV	V2, V6, V2
+	VXORV	V3, V7, V3
+	VXORV	V0, V8, V0
+	VXORV	V1, V9, V1
+	VXORV	V2, V10, V2
+	VXORV	V3, V11, V3
+	VMOVQ	V0, (R4)
+	VMOVQ	V1, 16(R4)
+	VMOVQ	V2, 32(R4)
+	VMOVQ	V3, 48(R4)
+
+	SUBV	$128, R8
+	ADDV	$128, R7
+	BNE	R8, R0, loop
+
+	MOVV	R9, (R5)
+	MOVV	R10, 8(R5)
+
+	RET

blake2b/blake2b_ref.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !amd64 || purego || !gc
+//go:build (!amd64 && !loong64) || purego || !gc
 
 package blake2b
 

blake2b/blake2b_test.go

@@ -14,6 +14,8 @@ import (
 	"testing"
 )
 
+var _ hash.XOF = (*xof)(nil)
+
 func fromHex(s string) []byte {
 	b, err := hex.DecodeString(s)
 	if err != nil {

chacha20/chacha_loong64.go

@@ -0,0 +1,22 @@
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build gc && !purego
+
+package chacha20
+
+import "golang.org/x/sys/cpu"
+
+const bufSize = 256
+
+//go:noescape
+func xorKeyStreamVX(dst, src []byte, key *[8]uint32, nonce *[3]uint32, counter *uint32)
+
+func (c *Cipher) xorKeyStreamBlocks(dst, src []byte) {
+	if cpu.Loong64.HasLSX {
+		xorKeyStreamVX(dst, src, &c.key, &c.nonce, &c.counter)
+	} else {
+		c.xorKeyStreamBlocksGeneric(dst, src)
+	}
+}

chacha20/chacha_loong64.s

@@ -0,0 +1,342 @@
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// derived from chacha_arm64.s
+
+//go:build gc && !purego
+
+#include "textflag.h"
+
+DATA	·constants+0x00(SB)/4, $0x61707865
+DATA	·constants+0x04(SB)/4, $0x3320646e
+DATA	·constants+0x08(SB)/4, $0x79622d32
+DATA	·constants+0x0c(SB)/4, $0x6b206574
+GLOBL	·constants(SB), NOPTR|RODATA, $32
+
+DATA	·incRotMatrix+0x00(SB)/4, $0x00000000
+DATA	·incRotMatrix+0x04(SB)/4, $0x00000001
+DATA	·incRotMatrix+0x08(SB)/4, $0x00000002
+DATA	·incRotMatrix+0x0c(SB)/4, $0x00000003
+GLOBL	·incRotMatrix(SB), NOPTR|RODATA, $32
+
+#define NUM_ROUNDS 10
+
+// func xorKeyStreamVX(dst, src []byte, key *[8]uint32, nonce *[3]uint32, counter *uint32)
+TEXT ·xorKeyStreamVX(SB), NOSPLIT, $0
+	MOVV	dst+0(FP), R4
+	MOVV	src+24(FP), R5
+	MOVV	src_len+32(FP), R6
+	MOVV	key+48(FP), R7
+	MOVV	nonce+56(FP), R8
+	MOVV	counter+64(FP), R9
+
+	MOVV	$·constants(SB), R10
+	MOVV	$·incRotMatrix(SB), R11
+
+	MOVW	(R9), R12
+
+loop:
+	MOVV	$NUM_ROUNDS, R15
+	// load 4-32bit data from incRotMatrix added to counter
+	VMOVQ	(R11), V30
+
+	// load contants
+	VMOVQ	(R10), V0.W4
+	VMOVQ	4(R10), V1.W4
+	VMOVQ	8(R10), V2.W4
+	VMOVQ	12(R10), V3.W4
+
+	// load keys
+	VMOVQ	(R7), V4.W4
+	VMOVQ	4(R7), V5.W4
+	VMOVQ	8(R7), V6.W4
+	VMOVQ	12(R7), V7.W4
+	VMOVQ	16(R7), V8.W4
+	VMOVQ	20(R7), V9.W4
+	VMOVQ	24(R7), V10.W4
+	VMOVQ	28(R7), V11.W4
+
+	// load counter + nonce
+	VMOVQ	(R9), V12.W4
+
+	VMOVQ	(R8), V13.W4
+	VMOVQ	4(R8), V14.W4
+	VMOVQ	8(R8), V15.W4
+
+	// update counter
+	VADDW	V30, V12, V12
+
+chacha:
+	// V0..V3 += V4..V7
+	// V12..V15 <<<= ((V12..V15 XOR V0..V3), 16)
+	VADDW	V0, V4, V0
+	VADDW	V1, V5, V1
+	VADDW	V2, V6, V2
+	VADDW	V3, V7, V3
+	VXORV	V12, V0, V12
+	VXORV	V13, V1, V13
+	VXORV	V14, V2, V14
+	VXORV	V15, V3, V15
+	VROTRW	$16, V12, V12
+	VROTRW	$16, V13, V13
+	VROTRW	$16, V14, V14
+	VROTRW	$16, V15, V15
+
+	// V8..V11 += V12..V15
+	// V4..V7 <<<= ((V4..V7 XOR V8..V11), 12)
+	VADDW	V8, V12, V8
+	VADDW	V9, V13, V9
+	VADDW	V10, V14, V10
+	VADDW	V11, V15, V11
+	VXORV	V4, V8, V4
+	VXORV	V5, V9, V5
+	VXORV	V6, V10, V6
+	VXORV	V7, V11, V7
+	VROTRW	$20, V4, V4
+	VROTRW	$20, V5, V5
+	VROTRW	$20, V6, V6
+	VROTRW	$20, V7, V7
+
+	// V0..V3 += V4..V7
+	// V12..V15 <<<= ((V12..V15 XOR V0..V3), 8)
+	VADDW	V0, V4, V0
+	VADDW	V1, V5, V1
+	VADDW	V2, V6, V2
+	VADDW	V3, V7, V3
+	VXORV	V12, V0, V12
+	VXORV	V13, V1, V13
+	VXORV	V14, V2, V14
+	VXORV	V15, V3, V15
+	VROTRW	$24, V12, V12
+	VROTRW	$24, V13, V13
+	VROTRW	$24, V14, V14
+	VROTRW	$24, V15, V15
+
+	// V8..V11 += V12..V15
+	// V4..V7 <<<= ((V4..V7 XOR V8..V11), 7)
+	VADDW	V12, V8, V8
+	VADDW	V13, V9, V9
+	VADDW	V14, V10, V10
+	VADDW	V15, V11, V11
+	VXORV	V4, V8, V4
+	VXORV	V5, V9, V5
+	VXORV	V6, V10, V6
+	VXORV	V7, V11, V7
+	VROTRW	$25, V4, V4
+	VROTRW	$25, V5, V5
+	VROTRW	$25, V6, V6
+	VROTRW	$25, V7, V7
+
+	// V0..V3 += V5..V7, V4
+	// V15,V12-V14 <<<= ((V15,V12-V14 XOR V0..V3), 16)
+	VADDW	V0, V5, V0
+	VADDW	V1, V6, V1
+	VADDW	V2, V7, V2
+	VADDW	V3, V4, V3
+	VXORV	V15, V0, V15
+	VXORV	V12, V1, V12
+	VXORV	V13, V2, V13
+	VXORV	V14, V3, V14
+	VROTRW	$16, V15, V15
+	VROTRW	$16, V12, V12
+	VROTRW	$16, V13, V13
+	VROTRW	$16, V14, V14
+
+	// V10,V11,V8,V9 += V15,V12,V13,V14
+	// V5,V6,V7,V4 <<<= ((V5,V6,V7,V4 XOR V10,V11,V8,V9), 12)
+	VADDW	V10, V15, V10
+	VADDW	V11, V12, V11
+	VADDW	V8, V13, V8
+	VADDW	V9, V14, V9
+	VXORV	V5, V10, V5
+	VXORV	V6, V11, V6
+	VXORV	V7, V8, V7
+	VXORV	V4, V9, V4
+	VROTRW	$20, V5, V5
+	VROTRW	$20, V6, V6
+	VROTRW	$20, V7, V7
+	VROTRW	$20, V4, V4
+
+	// V0..V3 += V5..V7, V4
+	// V15,V12-V14 <<<= ((V15,V12-V14 XOR V0..V3), 8)
+	VADDW	V5, V0, V0
+	VADDW	V6, V1, V1
+	VADDW	V7, V2, V2
+	VADDW	V4, V3, V3
+	VXORV	V15, V0, V15
+	VXORV	V12, V1, V12
+	VXORV	V13, V2, V13
+	VXORV	V14, V3, V14
+	VROTRW	$24, V15, V15
+	VROTRW	$24, V12, V12
+	VROTRW	$24, V13, V13
+	VROTRW	$24, V14, V14
+
+	// V10,V11,V8,V9 += V15,V12,V13,V14
+	// V5,V6,V7,V4 <<<= ((V5,V6,V7,V4 XOR V10,V11,V8,V9), 7)
+	VADDW	V15, V10, V10
+	VADDW	V12, V11, V11
+	VADDW	V13, V8, V8
+	VADDW	V14, V9, V9
+	VXORV	V5, V10, V5
+	VXORV	V6, V11, V6
+	VXORV	V7, V8, V7
+	VXORV	V4, V9, V4
+	VROTRW	$25, V5, V5
+	VROTRW	$25, V6, V6
+	VROTRW	$25, V7, V7
+	VROTRW	$25, V4, V4
+
+	SUBV	$1, R15
+	BNE	R15, R0, chacha
+
+	// load origin contants
+	VMOVQ	(R10), V16.W4
+	VMOVQ	4(R10), V17.W4
+	VMOVQ	8(R10), V18.W4
+	VMOVQ	12(R10), V19.W4
+
+	// load origin keys
+	VMOVQ	(R7), V20.W4
+	VMOVQ	4(R7), V21.W4
+	VMOVQ	8(R7), V22.W4
+	VMOVQ	12(R7), V23.W4
+	VMOVQ	16(R7), V24.W4
+	VMOVQ	20(R7), V25.W4
+	VMOVQ	24(R7), V26.W4
+	VMOVQ	28(R7), V27.W4
+
+	// add back the initial state to generate the key stream
+	VADDW	V30, V12, V12	// update counter in advance to prevent V30 from being overwritten
+	VADDW	V16, V0, V0
+	VADDW	V17, V1, V1
+	VADDW	V18, V2, V2
+	VADDW	V19, V3, V3
+
+	// load origin counter + nonce
+	VMOVQ	(R9), V28.W4
+	VMOVQ	(R8), V29.W4
+	VMOVQ	4(R8), V30.W4
+	VMOVQ	8(R8), V31.W4
+
+	VADDW	V20, V4, V4
+	VADDW	V21, V5, V5
+	VADDW	V22, V6, V6
+	VADDW	V23, V7, V7
+	VADDW	V24, V8, V8
+	VADDW	V25, V9, V9
+	VADDW	V26, V10, V10
+	VADDW	V27, V11, V11
+	VADDW	V28, V12, V12
+	VADDW	V29, V13, V13
+	VADDW	V30, V14, V14
+	VADDW	V31, V15, V15
+
+	// shuffle
+	VILVLW	V0, V1, V16
+	VILVHW	V0, V1, V17
+	VILVLW	V2, V3, V18
+	VILVHW	V2, V3, V19
+	VILVLW	V4, V5 ,V20
+	VILVHW	V4, V5, V21
+	VILVLW	V6, V7, V22
+	VILVHW	V6, V7, V23
+	VILVLW	V8, V9, V24
+	VILVHW	V8, V9, V25
+	VILVLW	V10, V11, V26
+	VILVHW	V10, V11, V27
+	VILVLW	V12, V13, V28
+	VILVHW	V12, V13, V29
+	VILVLW	V14, V15, V30
+	VILVHW	V14, V15, V31
+	VILVLV	V16, V18, V0
+	VILVHV	V16, V18, V4
+	VILVLV	V17, V19, V8
+	VILVHV	V17, V19, V12
+
+	// load src data from R5
+	VMOVQ	0(R5), V16
+	VMOVQ	16(R5), V17
+	VMOVQ	32(R5), V18
+	VMOVQ	48(R5), V19
+
+	VILVLV	V20, V22, V1
+	VILVHV	V20, V22, V5
+	VILVLV	V21, V23, V9
+	VILVHV	V21, V23, V13
+
+	VMOVQ	64(R5), V20
+	VMOVQ	80(R5), V21
+	VMOVQ	96(R5), V22
+	VMOVQ	112(R5), V23
+
+	VILVLV	V24, V26, V2
+	VILVHV	V24, V26, V6
+	VILVLV	V25, V27, V10
+	VILVHV	V25, V27, V14
+
+	VMOVQ	128(R5), V24
+	VMOVQ	144(R5), V25
+	VMOVQ	160(R5), V26
+	VMOVQ	176(R5), V27
+
+	VILVLV	V28, V30, V3
+	VILVHV	V28, V30, V7
+	VILVLV	V29, V31, V11
+	VILVHV	V29, V31, V15
+
+	VMOVQ	192(R5), V28
+	VMOVQ	208(R5), V29
+	VMOVQ	224(R5), V30
+	VMOVQ	240(R5), V31
+
+	VXORV	V0, V16, V16
+	VXORV	V1, V17, V17
+	VXORV	V2, V18, V18
+	VXORV	V3, V19, V19
+
+	VMOVQ	V16, 0(R4)
+	VMOVQ	V17, 16(R4)
+	VMOVQ	V18, 32(R4)
+	VMOVQ	V19, 48(R4)
+
+	VXORV	V4, V20, V20
+	VXORV	V5, V21, V21
+	VXORV	V6, V22, V22
+	VXORV	V7, V23, V23
+
+	VMOVQ	V20, 64(R4)
+	VMOVQ	V21, 80(R4)
+	VMOVQ	V22, 96(R4)
+	VMOVQ	V23, 112(R4)
+
+	VXORV	V8, V24, V24
+	VXORV	V9, V25, V25
+	VXORV	V10, V26, V26
+	VXORV	V11, V27, V27
+
+	VMOVQ	V24, 128(R4)
+	VMOVQ	V25, 144(R4)
+	VMOVQ	V26, 160(R4)
+	VMOVQ	V27, 176(R4)
+
+	VXORV	V12, V28, V28
+	VXORV	V13, V29, V29
+	VXORV	V14, V30, V30
+	VXORV	V15, V31, V31
+
+	VMOVQ	V28, 192(R4)
+	VMOVQ	V29, 208(R4)
+	VMOVQ	V30, 224(R4)
+	VMOVQ	V31, 240(R4)
+
+	ADD	$4, R12, R12
+	MOVW	R12, (R9) // update counter
+
+	ADDV	$256, R4, R4
+	ADDV	$256, R5, R5
+	SUBV    $256, R6, R6
+	BNE     R6, R0, loop
+
+	RET

chacha20/chacha_noasm.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build (!arm64 && !s390x && !ppc64 && !ppc64le) || !gc || purego
+//go:build (!arm64 && !loong64 && !s390x && !ppc64 && !ppc64le) || !gc || purego
 
 package chacha20
 

chacha20poly1305/chacha20poly1305.go

@@ -38,6 +38,9 @@ type chacha20poly1305 struct {
 
 // New returns a ChaCha20-Poly1305 AEAD that uses the given 256-bit key.
 func New(key []byte) (cipher.AEAD, error) {
+	if fips140Enforced() {
+		return nil, errors.New("chacha20poly1305: use of ChaCha20Poly1305 is not allowed in FIPS 140-only mode")
+	}
 	if len(key) != KeySize {
 		return nil, errors.New("chacha20poly1305: bad key length")
 	}

chacha20poly1305/chacha20poly1305_amd64.go

@@ -20,7 +20,7 @@ func chacha20Poly1305Open(dst []byte, key []uint32, src, ad []byte) bool
 func chacha20Poly1305Seal(dst []byte, key []uint32, src, ad []byte)
 
 var (
-	useAVX2 = cpu.X86.HasAVX2 && cpu.X86.HasBMI2
+	useAVX2 = cpu.X86.HasSSSE3 && cpu.X86.HasAVX2 && cpu.X86.HasBMI2
 )
 
 // setupState writes a ChaCha20 input matrix to state. See
@@ -47,7 +47,7 @@ func setupState(state *[16]uint32, key *[32]byte, nonce []byte) {
 }
 
 func (c *chacha20poly1305) seal(dst, nonce, plaintext, additionalData []byte) []byte {
-	if !cpu.X86.HasSSSE3 {
+	if !useAVX2 {
 		return c.sealGeneric(dst, nonce, plaintext, additionalData)
 	}
 
@@ -66,7 +66,7 @@ func (c *chacha20poly1305) seal(dst, nonce, plaintext, additionalData []byte) []
 }
 
 func (c *chacha20poly1305) open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) {
-	if !cpu.X86.HasSSSE3 {
+	if !useAVX2 {
 		return c.openGeneric(dst, nonce, ciphertext, additionalData)
 	}
 

chacha20poly1305/fips140only_compat.go

@@ -2,10 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build go1.25
+//go:build !go1.26
 
-package blake2b
+package chacha20poly1305
 
-import "hash"
-
-var _ hash.XOF = (*xof)(nil)
+func fips140Enforced() bool { return false }

chacha20poly1305/fips140only_go1.26.go

@@ -0,0 +1,11 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.26
+
+package chacha20poly1305
+
+import "crypto/fips140"
+
+func fips140Enforced() bool { return fips140.Enforced() }

chacha20poly1305/xchacha20poly1305.go

@@ -22,6 +22,9 @@ type xchacha20poly1305 struct {
 // preferred when nonce uniqueness cannot be trivially ensured, or whenever
 // nonces are randomly generated.
 func NewX(key []byte) (cipher.AEAD, error) {
+	if fips140Enforced() {
+		return nil, errors.New("chacha20poly1305: use of ChaCha20Poly1305 is not allowed in FIPS 140-only mode")
+	}
 	if len(key) != KeySize {
 		return nil, errors.New("chacha20poly1305: bad key length")
 	}

go.mod

@@ -1,11 +1,11 @@
 module golang.org/x/crypto
 
-go 1.24.0
+go 1.26.0
 
 require (
-	golang.org/x/net v0.47.0 // tagx:ignore
-	golang.org/x/sys v0.38.0
-	golang.org/x/term v0.37.0
+	golang.org/x/net v0.58.0 // tagx:ignore
+	golang.org/x/sys v0.48.0
+	golang.org/x/term v0.46.0
 )
 
-require golang.org/x/text v0.31.0 // indirect
+require golang.org/x/text v0.42.0 // indirect

go.sum

@@ -1,8 +1,8 @@
-golang.org/x/net v0.47.0 h1:Mx+4dIFzqraBXUugkia1OOvlD6LemFo1ALMHjrXDOhY=
-golang.org/x/net v0.47.0/go.mod h1:/jNxtkgq5yWUGYkaZGqo27cfGZ1c5Nen03aYrrKpVRU=
-golang.org/x/sys v0.38.0 h1:3yZWxaJjBmCWXqhN1qh02AkOnCQ1poK6oF+a7xWL6Gc=
-golang.org/x/sys v0.38.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
-golang.org/x/term v0.37.0 h1:8EGAD0qCmHYZg6J17DvsMy9/wJ7/D/4pV/wfnld5lTU=
-golang.org/x/term v0.37.0/go.mod h1:5pB4lxRNYYVZuTLmy8oR2BH8dflOR+IbTYFD8fi3254=
-golang.org/x/text v0.31.0 h1:aC8ghyu4JhP8VojJ2lEHBnochRno1sgL6nEi9WGFGMM=
-golang.org/x/text v0.31.0/go.mod h1:tKRAlv61yKIjGGHX/4tP1LTbc13YSec1pxVEWXzfoeM=
+golang.org/x/net v0.58.0 h1:ynWG7rqYi4ccpTEuPZ2QGWHktVEM9DMCj9yzDE0Q7To=
+golang.org/x/net v0.58.0/go.mod h1:YwCddHnFlT7eLQqVprV19OnhLGtc5xOKgE0RyqgfWAU=
+golang.org/x/sys v0.48.0 h1:bbX/i/6MgT9BVLM9RT1thmxL04yeTAhbEz4SyadbXoo=
+golang.org/x/sys v0.48.0/go.mod h1:hNLxWAXmnKAxqDtdwIYC4bM9oQPEecfsnNMuSxOs3og=
+golang.org/x/term v0.46.0 h1:3+OXuTbaKDgwk8jTi3aSLHRlmWqHEUDUtxnbFigO4YE=
+golang.org/x/term v0.46.0/go.mod h1:+K02xbkittuwc0Am4abfA3Fc+XRGXkvBXNO88NCXPoc=
+golang.org/x/text v0.42.0 h1:JbOZXgfeCPU9gacVtYliJqOhD+zhrEqK4LfdpmlUZqI=
+golang.org/x/text v0.42.0/go.mod h1:ojzP1Z+2QtioaF8DTtO8K5q7JWVVYwZKenzujK0Zd0E=

hkdf/hkdf.go

@@ -11,6 +11,7 @@
 package hkdf
 
 import (
+	"crypto/hkdf"
 	"crypto/hmac"
 	"errors"
 	"hash"
@@ -24,15 +25,19 @@ import (
 // Expand invocations and different context values. Most common scenarios,
 // including the generation of multiple keys, should use New instead.
 func Extract(hash func() hash.Hash, secret, salt []byte) []byte {
-	if salt == nil {
-		salt = make([]byte, hash().Size())
+	// Use the stdlib Extract, which disables FIPS 140 enforcement of the HMAC
+	// key (which in HKDF is the salt). The only possible error is FIPS 140
+	// enforcement of the hash, which had to panic under this API anyway. We
+	// don't use the stdlib Expand, because it switched to returning a []byte
+	// instead of an io.Reader, and Expand uses the HMAC key as a key.
+	out, err := hkdf.Extract(hash, secret, salt)
+	if err != nil {
+		panic(err)
 	}
-	extractor := hmac.New(hash, salt)
-	extractor.Write(secret)
-	return extractor.Sum(nil)
+	return out
 }
 
-type hkdf struct {
+type hkdfReader struct {
 	expander hash.Hash
 	size     int
 
@@ -43,7 +48,7 @@ type hkdf struct {
 	buf  []byte
 }
 
-func (f *hkdf) Read(p []byte) (int, error) {
+func (f *hkdfReader) Read(p []byte) (int, error) {
 	// Check whether enough data can be generated
 	need := len(p)
 	remains := len(f.buf) + int(255-f.counter+1)*f.size
@@ -84,7 +89,7 @@ func (f *hkdf) Read(p []byte) (int, error) {
 // 3.3. Most common scenarios will want to use New instead.
 func Expand(hash func() hash.Hash, pseudorandomKey, info []byte) io.Reader {
 	expander := hmac.New(hash, pseudorandomKey)
-	return &hkdf{expander, expander.Size(), info, 1, nil, nil}
+	return &hkdfReader{expander, expander.Size(), info, 1, nil, nil}
 }
 
 // New returns a Reader, from which keys can be read, using the given hash,

internal/poly1305/mac_noasm.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build (!amd64 && !loong64 && !ppc64le && !ppc64 && !s390x) || !gc || purego
+//go:build (!amd64 && !loong64 && !ppc64le && !ppc64 && !riscv64 && !s390x) || !gc || purego
 
 package poly1305
 

internal/poly1305/sum_asm.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build gc && !purego && (amd64 || loong64 || ppc64 || ppc64le)
+//go:build gc && !purego && (amd64 || loong64 || ppc64 || ppc64le || riscv64)
 
 package poly1305
 

internal/poly1305/sum_riscv64.s

@@ -0,0 +1,158 @@
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build gc && !purego
+
+#define LOAD64U(base, offset, t0, t1, t2, t3, dst) \
+	MOVBU	(offset+0*1)(base), t0; \
+	MOVBU	(offset+1*1)(base), t1; \
+	MOVBU	(offset+2*1)(base), t2; \
+	MOVBU	(offset+3*1)(base), t3; \
+	SLL	$8, t1; \
+	SLL	$16, t2; \
+	SLL	$24, t3; \
+	OR	t1, t0; \
+	OR	t3, t2; \
+	OR	t2, t0, dst; \
+	MOVBU	(offset+4*1)(base), t0; \
+	MOVBU	(offset+5*1)(base), t1; \
+	MOVBU	(offset+6*1)(base), t2; \
+	MOVBU	(offset+7*1)(base), t3; \
+	SLL	$32, t0; \
+	SLL	$40, t1; \
+	SLL	$48, t2; \
+	SLL	$56, t3; \
+	OR	t1, t0; \
+	OR	t3, t2; \
+	OR	t2, t0; \
+	OR	t0, dst
+
+// func update(state *macState, msg []byte)
+TEXT ·update(SB), $0-32
+	MOV	state+0(FP), X5
+	MOV	msg_base+8(FP), X6
+	MOV	msg_len+16(FP), X7
+
+	MOV	$16, X8
+
+	AND	$7, X6, X28
+
+	MOV	(0*8)(X5), X9		// h0
+	MOV	(1*8)(X5), X10		// h1
+	MOV	(2*8)(X5), X11		// h2
+	MOV	(3*8)(X5), X12		// r0
+	MOV	(4*8)(X5), X13		// r1
+
+	BLT	X7, X8, tail
+
+loop:
+	BEQZ	X28, aligned_load
+
+	LOAD64U(X6, 0*8, X16, X18, X19, X20, X15)	// msg[0:8]
+	LOAD64U(X6, 1*8, X16, X18, X19, X20, X17)	// msg[8:16]
+	JMP	block
+
+aligned_load:
+	MOV	(0*8)(X6), X15		// msg[0:8]
+	MOV	(1*8)(X6), X17		// msg[8:16]
+
+block:
+	ADD	X15, X9		// h0 (x1 + y1 = z1', if z1' < x1 then z1' overflow)
+	SLTU	X15, X9, X19	// h0.carry
+	ADD	X17, X10, X22
+	SLTU	X17, X22, X23
+	ADD	X22, X19, X10	// h1
+	SLTU	X22, X10, X19
+	OR	X23, X19	// h1.carry
+	ADD	$1, X19
+	ADD	X19, X11	// h2
+
+	ADD	$16, X6		// msg = msg[16:]
+
+multiply:
+	MULHU	X9, X12, X16	// h0r0.hi
+	MUL	X9, X12, X15	// h0r0.lo
+	MULHU	X10, X12, X17	// h1r0.hi
+	MUL	X10, X12, X14	// h1r0.lo
+	ADD	X14, X16
+	SLTU	X14, X16, X19
+	ADD	X19, X17
+	MUL	X11, X12, X20
+	ADD	X17, X20
+	MULHU	X9, X13, X17	// h0r1.hi
+	MUL	X9, X13, X14	// h0r1.lo
+	ADD	X14, X16
+	SLTU	X14, X16, X19
+	ADD	X19, X17
+	MOV	X17, X9
+	MUL	X11, X13, X21	// h2r1
+	MULHU	X10, X13, X17	// h1r1.hi
+	MUL	X10, X13, X14	// h1r1.lo
+	ADD	X14, X20
+	ADD	X17, X21, X22
+	SLTU	X14, X20, X19
+	ADD	X22, X19, X21
+	ADD	X9, X20
+	SLTU	X9, X20, X19
+	ADD	X19, X21
+	AND	$3, X20, X11
+	AND	$-4, X20, X18
+	ADD	X18, X15, X9
+	ADD	X21, X16, X22
+	SLTU	X18, X9, X19
+	SLTU	X21, X22, X23
+	ADD	X22, X19, X10
+	SLTU	X22, X10, X19
+	OR	X19, X23, X19
+	ADD	X19, X11
+	SLL	$62, X21, X22
+	SRL	$2, X20, X23
+	SRL	$2, X21, X21
+	OR	X22, X23, X20
+	ADD	X20, X9, X9
+	ADD	X21, X10, X22
+	SLTU	X20, X9, X19
+	SLTU	X21, X22, X23
+	ADD	X22, X19, X10
+	SLTU	X22, X10, X19
+	OR	X19, X23, X19
+	ADD	X19, X11, X11
+
+	SUB	$16, X7, X7
+	BGE	X7, X8, loop
+
+tail:
+	BEQ	X7, X0, done
+	MOV	$1, X15
+	MOV $0, X16
+	ADD	X7, X6, X6
+
+flush_buffer:
+	MOVBU	-1(X6), X20
+	SRL	$56, X15, X19
+	SLL	$8, X16, X23
+	SLL	$8, X15, X15
+	OR	X19, X23, X16
+	XOR	X20, X15
+	SUB	$1, X7, X7
+	SUB	$1, X6, X6
+	BNE	X7, X0, flush_buffer
+
+	ADD	X15, X9
+	SLTU	X15, X9, X19
+	ADD	X16, X10, X22
+	SLTU	X16, X22, X23
+	ADD	X22, X19, X10
+	SLTU	X22, X10, X19
+	OR	X23, X19
+	ADD	X19, X11
+
+	MOV	$16, X7
+	JMP	multiply
+
+done:
+	MOV	X9, (0*8)(X5)	// h0
+	MOV	X10, (1*8)(X5)
+	MOV	X11, (2*8)(X5)
+	RET

internal/wycheproof/README.md

@@ -1,12 +0,0 @@
-This package runs a set of the Wycheproof tests provided by
-https://github.com/google/wycheproof.
-
-The JSON test files live in
-https://github.com/google/wycheproof/tree/master/testvectors
-and are being fetched and cached at a pinned version every time
-these tests are run. To change the version of the wycheproof
-repository that is being used for testing, update wycheproofModVer.
-
-The structs for these tests are generated from the
-schemas provided in https://github.com/google/wycheproof/tree/master/schemas
-using https://github.com/a-h/generate.

internal/wycheproof/aead_test.go

@@ -1,176 +0,0 @@
-// Copyright 2020 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package wycheproof
-
-import (
-	"bytes"
-	"crypto/aes"
-	"crypto/cipher"
-	"fmt"
-	"testing"
-
-	"golang.org/x/crypto/chacha20poly1305"
-)
-
-func TestAEAD(t *testing.T) {
-	// AeadTestVector
-	type AeadTestVector struct {
-
-		// additional authenticated data
-		Aad string `json:"aad,omitempty"`
-
-		// A brief description of the test case
-		Comment string `json:"comment,omitempty"`
-
-		// the ciphertext (without iv and tag)
-		Ct string `json:"ct,omitempty"`
-
-		// A list of flags
-		Flags []string `json:"flags,omitempty"`
-
-		// the nonce
-		Iv string `json:"iv,omitempty"`
-
-		// the key
-		Key string `json:"key,omitempty"`
-
-		// the plaintext
-		Msg string `json:"msg,omitempty"`
-
-		// Test result
-		Result string `json:"result,omitempty"`
-
-		// the authentication tag
-		Tag string `json:"tag,omitempty"`
-
-		// Identifier of the test case
-		TcId int `json:"tcId,omitempty"`
-	}
-
-	// Notes a description of the labels used in the test vectors
-	type Notes struct {
-	}
-
-	// AeadTestGroup
-	type AeadTestGroup struct {
-
-		// the IV size in bits
-		IvSize int `json:"ivSize,omitempty"`
-
-		// the keySize in bits
-		KeySize int `json:"keySize,omitempty"`
-
-		// the expected size of the tag in bits
-		TagSize int               `json:"tagSize,omitempty"`
-		Tests   []*AeadTestVector `json:"tests,omitempty"`
-		Type    interface{}       `json:"type,omitempty"`
-	}
-
-	// Root
-	type Root struct {
-
-		// the primitive tested in the test file
-		Algorithm string `json:"algorithm,omitempty"`
-
-		// the version of the test vectors.
-		GeneratorVersion string `json:"generatorVersion,omitempty"`
-
-		// additional documentation
-		Header []string `json:"header,omitempty"`
-
-		// a description of the labels used in the test vectors
-		Notes *Notes `json:"notes,omitempty"`
-
-		// the number of test vectors in this test
-		NumberOfTests int              `json:"numberOfTests,omitempty"`
-		Schema        interface{}      `json:"schema,omitempty"`
-		TestGroups    []*AeadTestGroup `json:"testGroups,omitempty"`
-	}
-
-	testSealOpen := func(t *testing.T, aead cipher.AEAD, tv *AeadTestVector, recoverBadNonce func()) {
-		defer recoverBadNonce()
-
-		iv, tag, ct, msg, aad := decodeHex(tv.Iv), decodeHex(tv.Tag), decodeHex(tv.Ct), decodeHex(tv.Msg), decodeHex(tv.Aad)
-
-		genCT := aead.Seal(nil, iv, msg, aad)
-		genMsg, err := aead.Open(nil, iv, genCT, aad)
-		if err != nil {
-			t.Errorf("failed to decrypt generated ciphertext: %s", err)
-		}
-		if !bytes.Equal(genMsg, msg) {
-			t.Errorf("unexpected roundtripped plaintext: got %x, want %x", genMsg, msg)
-		}
-
-		ctWithTag := append(ct, tag...)
-		msg2, err := aead.Open(nil, iv, ctWithTag, aad)
-		wantPass := shouldPass(tv.Result, tv.Flags, nil)
-		if !wantPass && err == nil {
-			t.Error("decryption succeeded when it should've failed")
-		} else if wantPass {
-			if err != nil {
-				t.Fatalf("decryption failed: %s", err)
-			}
-			if !bytes.Equal(genCT, ctWithTag) {
-				t.Errorf("generated ciphertext doesn't match expected: got %x, want %x", genCT, ctWithTag)
-			}
-			if !bytes.Equal(msg, msg2) {
-				t.Errorf("decrypted ciphertext doesn't match expected: got %x, want %x", msg2, msg)
-			}
-		}
-	}
-
-	vectors := map[string]func(*testing.T, []byte) cipher.AEAD{
-		"aes_gcm_test.json": func(t *testing.T, key []byte) cipher.AEAD {
-			aesCipher, err := aes.NewCipher(key)
-			if err != nil {
-				t.Fatalf("failed to construct cipher: %s", err)
-			}
-			aead, err := cipher.NewGCM(aesCipher)
-			if err != nil {
-				t.Fatalf("failed to construct cipher: %s", err)
-			}
-			return aead
-		},
-		"chacha20_poly1305_test.json": func(t *testing.T, key []byte) cipher.AEAD {
-			aead, err := chacha20poly1305.New(key)
-			if err != nil {
-				t.Fatalf("failed to construct cipher: %s", err)
-			}
-			return aead
-		},
-		"xchacha20_poly1305_test.json": func(t *testing.T, key []byte) cipher.AEAD {
-			aead, err := chacha20poly1305.NewX(key)
-			if err != nil {
-				t.Fatalf("failed to construct cipher: %s", err)
-			}
-			return aead
-		},
-	}
-	for file, cipherInit := range vectors {
-		var root Root
-		readTestVector(t, file, &root)
-		for _, tg := range root.TestGroups {
-			for _, tv := range tg.Tests {
-				testName := fmt.Sprintf("%s #%d", file, tv.TcId)
-				if tv.Comment != "" {
-					testName += fmt.Sprintf(" %s", tv.Comment)
-				}
-				t.Run(testName, func(t *testing.T) {
-					aead := cipherInit(t, decodeHex(tv.Key))
-					testSealOpen(t, aead, tv, func() {
-						// A bad nonce causes a panic in AEAD.Seal and AEAD.Open,
-						// so should be recovered. Fail the test if it broke for
-						// some other reason.
-						if r := recover(); r != nil {
-							if tg.IvSize/8 == aead.NonceSize() {
-								t.Error("unexpected panic")
-							}
-						}
-					})
-				})
-			}
-		}
-	}
-}

internal/wycheproof/aes_cbc_test.go

@@ -1,127 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package wycheproof
-
-import (
-	"crypto/aes"
-	"crypto/cipher"
-	"encoding/hex"
-	"fmt"
-	"testing"
-)
-
-func TestAesCbc(t *testing.T) {
-	// IndCpaTestVector
-	type IndCpaTestVector struct {
-
-		// A brief description of the test case
-		Comment string `json:"comment,omitempty"`
-
-		// the raw ciphertext (without IV)
-		Ct string `json:"ct,omitempty"`
-
-		// A list of flags
-		Flags []string `json:"flags,omitempty"`
-
-		// the initialization vector
-		Iv string `json:"iv,omitempty"`
-
-		// the key
-		Key string `json:"key,omitempty"`
-
-		// the plaintext
-		Msg string `json:"msg,omitempty"`
-
-		// Test result
-		Result string `json:"result,omitempty"`
-
-		// Identifier of the test case
-		TcId int `json:"tcId,omitempty"`
-	}
-
-	// Notes a description of the labels used in the test vectors
-	type Notes struct {
-	}
-
-	// IndCpaTestGroup
-	type IndCpaTestGroup struct {
-
-		// the IV size in bits
-		IvSize int `json:"ivSize,omitempty"`
-
-		// the keySize in bits
-		KeySize int `json:"keySize,omitempty"`
-
-		// the expected size of the tag in bits
-		TagSize int                 `json:"tagSize,omitempty"`
-		Tests   []*IndCpaTestVector `json:"tests,omitempty"`
-		Type    interface{}         `json:"type,omitempty"`
-	}
-
-	// Root
-	type Root struct {
-
-		// the primitive tested in the test file
-		Algorithm string `json:"algorithm,omitempty"`
-
-		// the version of the test vectors.
-		GeneratorVersion string `json:"generatorVersion,omitempty"`
-
-		// additional documentation
-		Header []string `json:"header,omitempty"`
-
-		// a description of the labels used in the test vectors
-		Notes *Notes `json:"notes,omitempty"`
-
-		// the number of test vectors in this test
-		NumberOfTests int                `json:"numberOfTests,omitempty"`
-		Schema        interface{}        `json:"schema,omitempty"`
-		TestGroups    []*IndCpaTestGroup `json:"testGroups,omitempty"`
-	}
-
-	var root Root
-	readTestVector(t, "aes_cbc_pkcs5_test.json", &root)
-	for _, tg := range root.TestGroups {
-	tests:
-		for _, tv := range tg.Tests {
-			block, err := aes.NewCipher(decodeHex(tv.Key))
-			if err != nil {
-				t.Fatalf("#%d: %v", tv.TcId, err)
-			}
-			mode := cipher.NewCBCDecrypter(block, decodeHex(tv.Iv))
-			ct := decodeHex(tv.Ct)
-			if len(ct)%aes.BlockSize != 0 {
-				panic(fmt.Sprintf("#%d: ciphertext is not a multiple of the block size", tv.TcId))
-			}
-			mode.CryptBlocks(ct, ct) // decrypt the block in place
-
-			// Skip the tests that are broken due to bad padding. Panic if there are any
-			// tests left that are invalid for some other reason in the future, to
-			// evaluate what to do with those tests.
-			for _, flag := range tv.Flags {
-				if flag == "BadPadding" {
-					continue tests
-				}
-			}
-			if !shouldPass(tv.Result, tv.Flags, nil) {
-				panic(fmt.Sprintf("#%d: found an invalid test that is broken for some reason other than bad padding", tv.TcId))
-			}
-
-			// Remove the PKCS#5 padding from the given ciphertext to validate it
-			padding := ct[len(ct)-1]
-			paddingNum := int(padding)
-			for i := paddingNum; i > 0; i-- {
-				if ct[len(ct)-i] != padding { // panic if the padding is unexpectedly bad
-					panic(fmt.Sprintf("#%d: bad padding at index=%d of %v", tv.TcId, i, ct))
-				}
-			}
-			ct = ct[:len(ct)-paddingNum]
-
-			if got, want := hex.EncodeToString(ct), tv.Msg; got != want {
-				t.Errorf("#%d, type: %s, comment: %q, decoded ciphertext not equal: %s, want %s", tv.TcId, tv.Result, tv.Comment, got, want)
-			}
-		}
-	}
-}

internal/wycheproof/boring.go

@@ -1,9 +0,0 @@
-// Copyright 2022 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build boringcrypto
-
-package wycheproof
-
-const boringcryptoEnabled = true

internal/wycheproof/dsa_test.go

@@ -1,123 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package wycheproof
-
-import (
-	"crypto/dsa"
-	"testing"
-
-	wdsa "golang.org/x/crypto/internal/wycheproof/internal/dsa"
-)
-
-func TestDsa(t *testing.T) {
-	// AsnSignatureTestVector
-	type AsnSignatureTestVector struct {
-
-		// A brief description of the test case
-		Comment string `json:"comment,omitempty"`
-
-		// A list of flags
-		Flags []string `json:"flags,omitempty"`
-
-		// The message to sign
-		Msg string `json:"msg,omitempty"`
-
-		// Test result
-		Result string `json:"result,omitempty"`
-
-		// An ASN encoded signature for msg
-		Sig string `json:"sig,omitempty"`
-
-		// Identifier of the test case
-		TcId int `json:"tcId,omitempty"`
-	}
-
-	// DsaPublicKey
-	type DsaPublicKey struct {
-
-		// the generator of the multiplicative subgroup
-		G string `json:"g,omitempty"`
-
-		// the key size in bits
-		KeySize int `json:"keySize,omitempty"`
-
-		// the modulus p
-		P string `json:"p,omitempty"`
-
-		// the order of the generator g
-		Q string `json:"q,omitempty"`
-
-		// the key type
-		Type string `json:"type,omitempty"`
-
-		// the public key value
-		Y string `json:"y,omitempty"`
-	}
-
-	// DsaTestGroup
-	type DsaTestGroup struct {
-
-		// unenocded DSA public key
-		Key *DsaPublicKey `json:"key,omitempty"`
-
-		// DER encoded public key
-		KeyDer string `json:"keyDer,omitempty"`
-
-		// Pem encoded public key
-		KeyPem string `json:"keyPem,omitempty"`
-
-		// the hash function used for DSA
-		Sha   string                    `json:"sha,omitempty"`
-		Tests []*AsnSignatureTestVector `json:"tests,omitempty"`
-		Type  interface{}               `json:"type,omitempty"`
-	}
-
-	// Notes a description of the labels used in the test vectors
-	type Notes struct {
-	}
-
-	// Root
-	type Root struct {
-
-		// the primitive tested in the test file
-		Algorithm string `json:"algorithm,omitempty"`
-
-		// the version of the test vectors.
-		GeneratorVersion string `json:"generatorVersion,omitempty"`
-
-		// additional documentation
-		Header []string `json:"header,omitempty"`
-
-		// a description of the labels used in the test vectors
-		Notes *Notes `json:"notes,omitempty"`
-
-		// the number of test vectors in this test
-		NumberOfTests int             `json:"numberOfTests,omitempty"`
-		Schema        interface{}     `json:"schema,omitempty"`
-		TestGroups    []*DsaTestGroup `json:"testGroups,omitempty"`
-	}
-
-	flagsShouldPass := map[string]bool{
-		// An encoded ASN.1 integer missing a leading zero is invalid, but accepted by some implementations.
-		"NoLeadingZero": false,
-	}
-
-	var root Root
-	readTestVector(t, "dsa_test.json", &root)
-	for _, tg := range root.TestGroups {
-		pub := decodePublicKey(tg.KeyDer).(*dsa.PublicKey)
-		h := parseHash(tg.Sha).New()
-		for _, sig := range tg.Tests {
-			h.Reset()
-			h.Write(decodeHex(sig.Msg))
-			hashed := h.Sum(nil)
-			hashed = hashed[:pub.Q.BitLen()/8] // Truncate to the byte-length of the subgroup (Q)
-			got := wdsa.VerifyASN1(pub, hashed, decodeHex(sig.Sig))
-			if want := shouldPass(sig.Result, sig.Flags, flagsShouldPass); got != want {
-				t.Errorf("tcid: %d, type: %s, comment: %q, wanted success: %t", sig.TcId, sig.Result, sig.Comment, want)
-			}
-		}
-	}
-}

internal/wycheproof/ecdh_stdlib_test.go

@@ -1,140 +0,0 @@
-// Copyright 2022 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package wycheproof
-
-import (
-	"bytes"
-	"crypto/ecdh"
-	"fmt"
-	"testing"
-)
-
-func TestECDHStdLib(t *testing.T) {
-	type ECDHTestVector struct {
-		// A brief description of the test case
-		Comment string `json:"comment,omitempty"`
-		// A list of flags
-		Flags []string `json:"flags,omitempty"`
-		// the private key
-		Private string `json:"private,omitempty"`
-		// Encoded public key
-		Public string `json:"public,omitempty"`
-		// Test result
-		Result string `json:"result,omitempty"`
-		// The shared secret key
-		Shared string `json:"shared,omitempty"`
-		// Identifier of the test case
-		TcID int `json:"tcId,omitempty"`
-	}
-
-	type ECDHTestGroup struct {
-		Curve string            `json:"curve,omitempty"`
-		Tests []*ECDHTestVector `json:"tests,omitempty"`
-	}
-
-	type Root struct {
-		TestGroups []*ECDHTestGroup `json:"testGroups,omitempty"`
-	}
-
-	flagsShouldPass := map[string]bool{
-		// We don't support compressed points.
-		"CompressedPoint": false,
-		// We don't support decoding custom curves.
-		"UnnamedCurve": false,
-		// WrongOrder and UnusedParam are only found with UnnamedCurve.
-		"WrongOrder":  false,
-		"UnusedParam": false,
-
-		// X25519 specific flags
-		"Twist":              true,
-		"SmallPublicKey":     false,
-		"LowOrderPublic":     false,
-		"ZeroSharedSecret":   false,
-		"NonCanonicalPublic": true,
-	}
-
-	// curveToCurve is a map of all elliptic curves supported
-	// by crypto/elliptic, which can subsequently be parsed and tested.
-	curveToCurve := map[string]ecdh.Curve{
-		"secp256r1":  ecdh.P256(),
-		"secp384r1":  ecdh.P384(),
-		"secp521r1":  ecdh.P521(),
-		"curve25519": ecdh.X25519(),
-	}
-
-	curveToKeySize := map[string]int{
-		"secp256r1":  32,
-		"secp384r1":  48,
-		"secp521r1":  66,
-		"curve25519": 32,
-	}
-
-	for _, f := range []string{
-		"ecdh_secp256r1_ecpoint_test.json",
-		"ecdh_secp384r1_ecpoint_test.json",
-		"ecdh_secp521r1_ecpoint_test.json",
-		"x25519_test.json",
-	} {
-		var root Root
-		readTestVector(t, f, &root)
-		for _, tg := range root.TestGroups {
-			if _, ok := curveToCurve[tg.Curve]; !ok {
-				continue
-			}
-			for _, tt := range tg.Tests {
-				tg, tt := tg, tt
-				t.Run(fmt.Sprintf("%s/%d", tg.Curve, tt.TcID), func(t *testing.T) {
-					t.Logf("Type: %v", tt.Result)
-					t.Logf("Flags: %q", tt.Flags)
-					t.Log(tt.Comment)
-
-					shouldPass := shouldPass(tt.Result, tt.Flags, flagsShouldPass)
-
-					curve := curveToCurve[tg.Curve]
-					p := decodeHex(tt.Public)
-					pub, err := curve.NewPublicKey(p)
-					if err != nil {
-						if shouldPass {
-							t.Errorf("NewPublicKey: %v", err)
-						}
-						return
-					}
-
-					privBytes := decodeHex(tt.Private)
-					if len(privBytes) != curveToKeySize[tg.Curve] {
-						t.Skipf("non-standard key size %d", len(privBytes))
-					}
-
-					priv, err := curve.NewPrivateKey(privBytes)
-					if err != nil {
-						if shouldPass {
-							t.Errorf("NewPrivateKey: %v", err)
-						}
-						return
-					}
-
-					shared := decodeHex(tt.Shared)
-					x, err := priv.ECDH(pub)
-					if err != nil {
-						if tg.Curve == "curve25519" && !shouldPass {
-							// ECDH is expected to only return an error when using X25519,
-							// in all other cases an error is unexpected.
-							return
-						}
-						t.Fatalf("ECDH: %v", err)
-					}
-
-					if bytes.Equal(shared, x) != shouldPass {
-						if shouldPass {
-							t.Errorf("ECDH = %x, want %x", shared, x)
-						} else {
-							t.Errorf("ECDH = %x, want anything else", shared)
-						}
-					}
-				})
-			}
-		}
-	}
-}

internal/wycheproof/ecdh_test.go

@@ -1,163 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package wycheproof
-
-import (
-	"bytes"
-	"crypto/ecdsa"
-	"crypto/elliptic"
-	"crypto/x509"
-	"encoding/asn1"
-	"errors"
-	"fmt"
-	"testing"
-
-	"golang.org/x/crypto/cryptobyte"
-	casn1 "golang.org/x/crypto/cryptobyte/asn1"
-)
-
-func TestECDH(t *testing.T) {
-	type ECDHTestVector struct {
-		// A brief description of the test case
-		Comment string `json:"comment,omitempty"`
-		// A list of flags
-		Flags []string `json:"flags,omitempty"`
-		// the private key
-		Private string `json:"private,omitempty"`
-		// Encoded public key
-		Public string `json:"public,omitempty"`
-		// Test result
-		Result string `json:"result,omitempty"`
-		// The shared secret key
-		Shared string `json:"shared,omitempty"`
-		// Identifier of the test case
-		TcID int `json:"tcId,omitempty"`
-	}
-
-	type ECDHTestGroup struct {
-		Curve string            `json:"curve,omitempty"`
-		Tests []*ECDHTestVector `json:"tests,omitempty"`
-	}
-
-	type Root struct {
-		TestGroups []*ECDHTestGroup `json:"testGroups,omitempty"`
-	}
-
-	flagsShouldPass := map[string]bool{
-		// ParsePKIXPublicKey doesn't support compressed points, but we test
-		// them against UnmarshalCompressed anyway.
-		"CompressedPoint": true,
-		// We don't support decoding custom curves.
-		"UnnamedCurve": false,
-		// WrongOrder and UnusedParam are only found with UnnamedCurve.
-		"WrongOrder":  false,
-		"UnusedParam": false,
-	}
-
-	// supportedCurves is a map of all elliptic curves supported
-	// by crypto/elliptic, which can subsequently be parsed and tested.
-	supportedCurves := map[string]bool{
-		"secp224r1": true,
-		"secp256r1": true,
-		"secp384r1": true,
-		"secp521r1": true,
-	}
-
-	var root Root
-	readTestVector(t, "ecdh_test.json", &root)
-	for _, tg := range root.TestGroups {
-		if !supportedCurves[tg.Curve] {
-			continue
-		}
-		for _, tt := range tg.Tests {
-			tg, tt := tg, tt
-			t.Run(fmt.Sprintf("%s/%d", tg.Curve, tt.TcID), func(t *testing.T) {
-				t.Logf("Type: %v", tt.Result)
-				t.Logf("Flags: %q", tt.Flags)
-				t.Log(tt.Comment)
-
-				shouldPass := shouldPass(tt.Result, tt.Flags, flagsShouldPass)
-
-				p := decodeHex(tt.Public)
-				pp, err := x509.ParsePKIXPublicKey(p)
-				if err != nil {
-					pp, err = decodeCompressedPKIX(p)
-				}
-				if err != nil {
-					if shouldPass {
-						t.Errorf("unexpected parsing error: %s", err)
-					}
-					return
-				}
-				pub := pp.(*ecdsa.PublicKey)
-
-				priv := decodeHex(tt.Private)
-				shared := decodeHex(tt.Shared)
-
-				x, _ := pub.Curve.ScalarMult(pub.X, pub.Y, priv)
-				xBytes := make([]byte, (pub.Curve.Params().BitSize+7)/8)
-				got := bytes.Equal(shared, x.FillBytes(xBytes))
-
-				if want := shouldPass; got != want {
-					t.Errorf("wanted success %v, got %v", want, got)
-				}
-			})
-		}
-	}
-}
-
-func decodeCompressedPKIX(der []byte) (interface{}, error) {
-	s := cryptobyte.String(der)
-	var s1, s2 cryptobyte.String
-	var algoOID, namedCurveOID asn1.ObjectIdentifier
-	var pointDER []byte
-	if !s.ReadASN1(&s1, casn1.SEQUENCE) || !s.Empty() ||
-		!s1.ReadASN1(&s2, casn1.SEQUENCE) ||
-		!s2.ReadASN1ObjectIdentifier(&algoOID) ||
-		!s2.ReadASN1ObjectIdentifier(&namedCurveOID) || !s2.Empty() ||
-		!s1.ReadASN1BitStringAsBytes(&pointDER) || !s1.Empty() {
-		return nil, errors.New("failed to parse PKIX structure")
-	}
-
-	if !algoOID.Equal(oidPublicKeyECDSA) {
-		return nil, errors.New("wrong algorithm OID")
-	}
-	namedCurve := namedCurveFromOID(namedCurveOID)
-	if namedCurve == nil {
-		return nil, errors.New("unsupported elliptic curve")
-	}
-	x, y := elliptic.UnmarshalCompressed(namedCurve, pointDER)
-	if x == nil {
-		return nil, errors.New("failed to unmarshal elliptic curve point")
-	}
-	pub := &ecdsa.PublicKey{
-		Curve: namedCurve,
-		X:     x,
-		Y:     y,
-	}
-	return pub, nil
-}
-
-var (
-	oidPublicKeyECDSA = asn1.ObjectIdentifier{1, 2, 840, 10045, 2, 1}
-	oidNamedCurveP224 = asn1.ObjectIdentifier{1, 3, 132, 0, 33}
-	oidNamedCurveP256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 3, 1, 7}
-	oidNamedCurveP384 = asn1.ObjectIdentifier{1, 3, 132, 0, 34}
-	oidNamedCurveP521 = asn1.ObjectIdentifier{1, 3, 132, 0, 35}
-)
-
-func namedCurveFromOID(oid asn1.ObjectIdentifier) elliptic.Curve {
-	switch {
-	case oid.Equal(oidNamedCurveP224):
-		return elliptic.P224()
-	case oid.Equal(oidNamedCurveP256):
-		return elliptic.P256()
-	case oid.Equal(oidNamedCurveP384):
-		return elliptic.P384()
-	case oid.Equal(oidNamedCurveP521):
-		return elliptic.P521()
-	}
-	return nil
-}

internal/wycheproof/ecdsa_test.go

@@ -1,105 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package wycheproof
-
-import (
-	"crypto/ecdsa"
-	"math/big"
-	"testing"
-
-	"golang.org/x/crypto/cryptobyte"
-	"golang.org/x/crypto/cryptobyte/asn1"
-)
-
-func TestECDSA(t *testing.T) {
-	type ASNSignatureTestVector struct {
-		// A brief description of the test case
-		Comment string `json:"comment"`
-		// A list of flags
-		Flags []string `json:"flags"`
-		// The message to sign
-		Msg string `json:"msg"`
-		// Test result
-		Result string `json:"result"`
-		// An ASN.1 encoded signature for msg
-		Sig string `json:"sig"`
-		// Identifier of the test case
-		TcID int `json:"tcId"`
-	}
-
-	type ECPublicKey struct {
-		// The EC group used by this public key
-		Curve interface{} `json:"curve"`
-	}
-
-	type ECDSATestGroup struct {
-		// Unencoded EC public key
-		Key *ECPublicKey `json:"key"`
-		// DER encoded public key
-		KeyDER string `json:"keyDer"`
-		// the hash function used for ECDSA
-		SHA   string                    `json:"sha"`
-		Tests []*ASNSignatureTestVector `json:"tests"`
-	}
-
-	type Root struct {
-		TestGroups []*ECDSATestGroup `json:"testGroups"`
-	}
-
-	flagsShouldPass := map[string]bool{
-		// An encoded ASN.1 integer missing a leading zero is invalid, but
-		// accepted by some implementations.
-		"MissingZero": false,
-		// A signature using a weaker hash than the EC params is not a security
-		// risk, as long as the hash is secure.
-		// https://www.imperialviolet.org/2014/05/25/strengthmatching.html
-		"WeakHash": true,
-	}
-
-	// supportedCurves is a map of all elliptic curves supported
-	// by crypto/elliptic, which can subsequently be parsed and tested.
-	supportedCurves := map[string]bool{
-		"secp224r1": true,
-		"secp256r1": true,
-		"secp384r1": true,
-		"secp521r1": true,
-	}
-
-	var root Root
-	readTestVector(t, "ecdsa_test.json", &root)
-	for _, tg := range root.TestGroups {
-		curve := tg.Key.Curve.(string)
-		if !supportedCurves[curve] {
-			continue
-		}
-		pub := decodePublicKey(tg.KeyDER).(*ecdsa.PublicKey)
-		h := parseHash(tg.SHA).New()
-		for _, sig := range tg.Tests {
-			h.Reset()
-			h.Write(decodeHex(sig.Msg))
-			hashed := h.Sum(nil)
-			sigBytes := decodeHex(sig.Sig)
-			got := ecdsa.VerifyASN1(pub, hashed, sigBytes)
-			if want := shouldPass(sig.Result, sig.Flags, flagsShouldPass); got != want {
-				t.Errorf("tcid: %d, type: %s, comment: %q, VerifyASN1 wanted success: %t", sig.TcID, sig.Result, sig.Comment, want)
-			}
-
-			var r, s big.Int
-			var inner cryptobyte.String
-			input := cryptobyte.String(sigBytes)
-			if !input.ReadASN1(&inner, asn1.SEQUENCE) ||
-				!input.Empty() ||
-				!inner.ReadASN1Integer(&r) ||
-				!inner.ReadASN1Integer(&s) ||
-				!inner.Empty() {
-				continue
-			}
-			got = ecdsa.Verify(pub, hashed, &r, &s)
-			if want := shouldPass(sig.Result, sig.Flags, flagsShouldPass); got != want {
-				t.Errorf("tcid: %d, type: %s, comment: %q, Verify wanted success: %t", sig.TcID, sig.Result, sig.Comment, want)
-			}
-		}
-	}
-}

internal/wycheproof/eddsa_test.go

@@ -1,97 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package wycheproof
-
-import (
-	"crypto/ed25519"
-	"testing"
-)
-
-func TestEddsa(t *testing.T) {
-	// Jwk the private key in webcrypto format
-	type Jwk struct {
-	}
-
-	// Key unencoded key pair
-	type Key struct {
-	}
-
-	// Notes a description of the labels used in the test vectors
-	type Notes struct {
-	}
-
-	// SignatureTestVector
-	type SignatureTestVector struct {
-
-		// A brief description of the test case
-		Comment string `json:"comment,omitempty"`
-
-		// A list of flags
-		Flags []string `json:"flags,omitempty"`
-
-		// The message to sign
-		Msg string `json:"msg,omitempty"`
-
-		// Test result
-		Result string `json:"result,omitempty"`
-
-		// A signature for msg
-		Sig string `json:"sig,omitempty"`
-
-		// Identifier of the test case
-		TcId int `json:"tcId,omitempty"`
-	}
-
-	// EddsaTestGroup
-	type EddsaTestGroup struct {
-
-		// the private key in webcrypto format
-		Jwk *Jwk `json:"jwk,omitempty"`
-
-		// unencoded key pair
-		Key *Key `json:"key,omitempty"`
-
-		// Asn encoded public key
-		KeyDer string `json:"keyDer,omitempty"`
-
-		// Pem encoded public key
-		KeyPem string                 `json:"keyPem,omitempty"`
-		Tests  []*SignatureTestVector `json:"tests,omitempty"`
-		Type   interface{}            `json:"type,omitempty"`
-	}
-
-	// Root
-	type Root struct {
-
-		// the primitive tested in the test file
-		Algorithm string `json:"algorithm,omitempty"`
-
-		// the version of the test vectors.
-		GeneratorVersion string `json:"generatorVersion,omitempty"`
-
-		// additional documentation
-		Header []string `json:"header,omitempty"`
-
-		// a description of the labels used in the test vectors
-		Notes *Notes `json:"notes,omitempty"`
-
-		// the number of test vectors in this test
-		NumberOfTests int               `json:"numberOfTests,omitempty"`
-		Schema        interface{}       `json:"schema,omitempty"`
-		TestGroups    []*EddsaTestGroup `json:"testGroups,omitempty"`
-	}
-
-	var root Root
-	readTestVector(t, "eddsa_test.json", &root)
-	for _, tg := range root.TestGroups {
-		pub := decodePublicKey(tg.KeyDer).(ed25519.PublicKey)
-		for _, sig := range tg.Tests {
-			got := ed25519.Verify(pub, decodeHex(sig.Msg), decodeHex(sig.Sig))
-			if want := shouldPass(sig.Result, sig.Flags, nil); got != want {
-				t.Errorf("tcid: %d, type: %s, comment: %q, wanted success: %t", sig.TcId, sig.Result, sig.Comment, want)
-			}
-		}
-	}
-}

internal/wycheproof/hkdf_test.go

@@ -1,111 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package wycheproof
-
-import (
-	"bytes"
-	"io"
-	"testing"
-
-	"golang.org/x/crypto/hkdf"
-)
-
-func TestHkdf(t *testing.T) {
-
-	// HkdfTestVector
-	type HkdfTestVector struct {
-
-		// A brief description of the test case
-		Comment string `json:"comment,omitempty"`
-
-		// A list of flags
-		Flags []string `json:"flags,omitempty"`
-
-		// the key (input key material)
-		Ikm string `json:"ikm,omitempty"`
-
-		// additional information used in the key derivation
-		Info string `json:"info,omitempty"`
-
-		// the generated bytes (output key material)
-		Okm string `json:"okm,omitempty"`
-
-		// Test result
-		Result string `json:"result,omitempty"`
-
-		// the salt for the key derivation
-		Salt string `json:"salt,omitempty"`
-
-		// the size of the output in bytes
-		Size int `json:"size,omitempty"`
-
-		// Identifier of the test case
-		TcId int `json:"tcId,omitempty"`
-	}
-
-	// Notes a description of the labels used in the test vectors
-	type Notes struct {
-	}
-
-	// HkdfTestGroup
-	type HkdfTestGroup struct {
-
-		// the size of the ikm in bits
-		KeySize int               `json:"keySize,omitempty"`
-		Tests   []*HkdfTestVector `json:"tests,omitempty"`
-		Type    interface{}       `json:"type,omitempty"`
-	}
-
-	// Root
-	type Root struct {
-
-		// the primitive tested in the test file
-		Algorithm string `json:"algorithm,omitempty"`
-
-		// the version of the test vectors.
-		GeneratorVersion string `json:"generatorVersion,omitempty"`
-
-		// additional documentation
-		Header []string `json:"header,omitempty"`
-
-		// a description of the labels used in the test vectors
-		Notes *Notes `json:"notes,omitempty"`
-
-		// the number of test vectors in this test
-		NumberOfTests int              `json:"numberOfTests,omitempty"`
-		Schema        interface{}      `json:"schema,omitempty"`
-		TestGroups    []*HkdfTestGroup `json:"testGroups,omitempty"`
-	}
-
-	fileHashAlgorithms := map[string]string{
-		"hkdf_sha1_test.json":   "SHA-1",
-		"hkdf_sha256_test.json": "SHA-256",
-		"hkdf_sha384_test.json": "SHA-384",
-		"hkdf_sha512_test.json": "SHA-512",
-	}
-
-	for f := range fileHashAlgorithms {
-		var root Root
-		readTestVector(t, f, &root)
-		for _, tg := range root.TestGroups {
-			for _, tv := range tg.Tests {
-				h := parseHash(fileHashAlgorithms[f]).New
-				hkdf := hkdf.New(h, decodeHex(tv.Ikm), decodeHex(tv.Salt), decodeHex(tv.Info))
-				key := make([]byte, tv.Size)
-				wantPass := shouldPass(tv.Result, tv.Flags, nil)
-				_, err := io.ReadFull(hkdf, key)
-				if (err == nil) != wantPass {
-					t.Errorf("tcid: %d, type: %s, comment: %q, wanted success: %t, got: %v", tv.TcId, tv.Result, tv.Comment, wantPass, err)
-				}
-				if err != nil {
-					continue // don't validate output text if reading failed
-				}
-				if got, want := key, decodeHex(tv.Okm); !bytes.Equal(got, want) {
-					t.Errorf("tcid: %d, type: %s, comment: %q, output bytes don't match", tv.TcId, tv.Result, tv.Comment)
-				}
-			}
-		}
-	}
-}

internal/wycheproof/hmac_test.go

@@ -1,105 +0,0 @@
-// Copyright 2020 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package wycheproof
-
-import (
-	"crypto/hmac"
-	"testing"
-)
-
-func TestHMAC(t *testing.T) {
-	// MacTestVector
-	type MacTestVector struct {
-
-		// A brief description of the test case
-		Comment string `json:"comment,omitempty"`
-
-		// A list of flags
-		Flags []string `json:"flags,omitempty"`
-
-		// the key
-		Key string `json:"key,omitempty"`
-
-		// the plaintext
-		Msg string `json:"msg,omitempty"`
-
-		// Test result
-		Result string `json:"result,omitempty"`
-
-		// the authentication tag
-		Tag string `json:"tag,omitempty"`
-
-		// Identifier of the test case
-		TcId int `json:"tcId,omitempty"`
-	}
-
-	// MacTestGroup
-	type MacTestGroup struct {
-
-		// the keySize in bits
-		KeySize int `json:"keySize,omitempty"`
-
-		// the expected size of the tag in bits
-		TagSize int              `json:"tagSize,omitempty"`
-		Tests   []*MacTestVector `json:"tests,omitempty"`
-		Type    interface{}      `json:"type,omitempty"`
-	}
-
-	// Notes a description of the labels used in the test vectors
-	type Notes struct {
-	}
-
-	// Root
-	type Root struct {
-
-		// the primitive tested in the test file
-		Algorithm string `json:"algorithm,omitempty"`
-
-		// the version of the test vectors.
-		GeneratorVersion string `json:"generatorVersion,omitempty"`
-
-		// additional documentation
-		Header []string `json:"header,omitempty"`
-
-		// a description of the labels used in the test vectors
-		Notes *Notes `json:"notes,omitempty"`
-
-		// the number of test vectors in this test
-		NumberOfTests int             `json:"numberOfTests,omitempty"`
-		Schema        interface{}     `json:"schema,omitempty"`
-		TestGroups    []*MacTestGroup `json:"testGroups,omitempty"`
-	}
-
-	fileHashAlgs := map[string]string{
-		"hmac_sha1_test.json":   "SHA-1",
-		"hmac_sha224_test.json": "SHA-224",
-		"hmac_sha256_test.json": "SHA-256",
-		"hmac_sha384_test.json": "SHA-384",
-		"hmac_sha512_test.json": "SHA-512",
-	}
-
-	for f := range fileHashAlgs {
-		var root Root
-		readTestVector(t, f, &root)
-		for _, tg := range root.TestGroups {
-			h := parseHash(fileHashAlgs[f])
-			// Skip test vectors where the tag length does not equal the
-			// hash length, since crypto/hmac does not support generating
-			// these truncated tags.
-			if tg.TagSize/8 != h.Size() {
-				continue
-			}
-			for _, tv := range tg.Tests {
-				hm := hmac.New(h.New, decodeHex(tv.Key))
-				hm.Write(decodeHex(tv.Msg))
-				tag := hm.Sum(nil)
-				got := hmac.Equal(decodeHex(tv.Tag), tag)
-				if want := shouldPass(tv.Result, tv.Flags, nil); want != got {
-					t.Errorf("%s, tcid: %d, type: %s, comment: %q, unexpected result", f, tv.TcId, tv.Result, tv.Comment)
-				}
-			}
-		}
-	}
-}

internal/wycheproof/internal/dsa/dsa.go

@@ -1,33 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Package dsa provides an internal version of dsa.Verify
-// that is used for the Wycheproof tests.
-package dsa
-
-import (
-	"crypto/dsa"
-	"math/big"
-
-	"golang.org/x/crypto/cryptobyte"
-	"golang.org/x/crypto/cryptobyte/asn1"
-)
-
-// VerifyASN1 verifies the ASN1 encoded signature, sig, of hash using the
-// public key, pub. Its return value records whether the signature is valid.
-func VerifyASN1(pub *dsa.PublicKey, hash, sig []byte) bool {
-	var (
-		r, s  = &big.Int{}, &big.Int{}
-		inner cryptobyte.String
-	)
-	input := cryptobyte.String(sig)
-	if !input.ReadASN1(&inner, asn1.SEQUENCE) ||
-		!input.Empty() ||
-		!inner.ReadASN1Integer(r) ||
-		!inner.ReadASN1Integer(s) ||
-		!inner.Empty() {
-		return false
-	}
-	return dsa.Verify(pub, hash, r, s)
-}

internal/wycheproof/notboring.go

@@ -1,9 +0,0 @@
-// Copyright 2022 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build !boringcrypto
-
-package wycheproof
-
-const boringcryptoEnabled = false

internal/wycheproof/rsa_oaep_decrypt_test.go

@@ -1,149 +0,0 @@
-// Copyright 2020 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package wycheproof
-
-import (
-	"bytes"
-	"crypto/rsa"
-	"crypto/x509"
-	"fmt"
-	"testing"
-)
-
-func TestRSAOAEPDecrypt(t *testing.T) {
-	// Notes a description of the labels used in the test vectors
-	type Notes struct {
-	}
-
-	// RsaesOaepTestVector
-	type RsaesOaepTestVector struct {
-
-		// A brief description of the test case
-		Comment string `json:"comment,omitempty"`
-
-		// An encryption of msg
-		Ct string `json:"ct,omitempty"`
-
-		// A list of flags
-		Flags []string `json:"flags,omitempty"`
-
-		// The label used for the encryption
-		Label string `json:"label,omitempty"`
-
-		// The encrypted message
-		Msg string `json:"msg,omitempty"`
-
-		// Test result
-		Result string `json:"result,omitempty"`
-
-		// Identifier of the test case
-		TcId int `json:"tcId,omitempty"`
-	}
-
-	// RsaesOaepTestGroup
-	type RsaesOaepTestGroup struct {
-
-		// The private exponent
-		D string `json:"d,omitempty"`
-
-		// The public exponent
-		E string `json:"e,omitempty"`
-
-		// the message generating function (e.g. MGF1)
-		Mgf string `json:"mgf,omitempty"`
-
-		// The hash function used for the message generating function.
-		MgfSha string `json:"mgfSha,omitempty"`
-
-		// The modulus of the key
-		N string `json:"n,omitempty"`
-
-		// Pem encoded private key
-		PrivateKeyPem string `json:"privateKeyPem,omitempty"`
-
-		// Pkcs 8 encoded private key.
-		PrivateKeyPkcs8 string `json:"privateKeyPkcs8,omitempty"`
-
-		// The hash function for hashing the label.
-		Sha   string                 `json:"sha,omitempty"`
-		Tests []*RsaesOaepTestVector `json:"tests,omitempty"`
-		Type  interface{}            `json:"type,omitempty"`
-	}
-
-	// Root
-	type Root struct {
-
-		// the primitive tested in the test file
-		Algorithm string `json:"algorithm,omitempty"`
-
-		// the version of the test vectors.
-		GeneratorVersion string `json:"generatorVersion,omitempty"`
-
-		// additional documentation
-		Header []string `json:"header,omitempty"`
-
-		// a description of the labels used in the test vectors
-		Notes *Notes `json:"notes,omitempty"`
-
-		// the number of test vectors in this test
-		NumberOfTests int                   `json:"numberOfTests,omitempty"`
-		Schema        interface{}           `json:"schema,omitempty"`
-		TestGroups    []*RsaesOaepTestGroup `json:"testGroups,omitempty"`
-	}
-
-	// rsa.DecryptOAEP doesn't support using a different hash for the
-	// MGF and the label, so skip all of the test vectors that use
-	// these unbalanced constructions. rsa_oaep_misc_test.json contains
-	// both balanced and unbalanced constructions so in that case
-	// we just filter out any test groups where MgfSha != Sha
-	files := []string{
-		"rsa_oaep_2048_sha1_mgf1sha1_test.json",
-		"rsa_oaep_2048_sha224_mgf1sha224_test.json",
-		"rsa_oaep_2048_sha256_mgf1sha256_test.json",
-		"rsa_oaep_2048_sha384_mgf1sha384_test.json",
-		"rsa_oaep_2048_sha512_mgf1sha512_test.json",
-		"rsa_oaep_3072_sha256_mgf1sha256_test.json",
-		"rsa_oaep_3072_sha512_mgf1sha512_test.json",
-		"rsa_oaep_4096_sha256_mgf1sha256_test.json",
-		"rsa_oaep_4096_sha512_mgf1sha512_test.json",
-		"rsa_oaep_misc_test.json",
-	}
-
-	flagsShouldPass := map[string]bool{
-		// rsa.DecryptOAEP happily supports small key sizes
-		"SmallModulus": true,
-	}
-
-	for _, f := range files {
-		var root Root
-		readTestVector(t, f, &root)
-		for _, tg := range root.TestGroups {
-			if tg.MgfSha != tg.Sha {
-				continue
-			}
-			priv, err := x509.ParsePKCS8PrivateKey(decodeHex(tg.PrivateKeyPkcs8))
-			if err != nil {
-				t.Fatalf("%s failed to parse PKCS #8 private key: %s", f, err)
-			}
-			hash := parseHash(tg.Sha)
-			for _, tv := range tg.Tests {
-				t.Run(fmt.Sprintf("%s #%d", f, tv.TcId), func(t *testing.T) {
-					wantPass := shouldPass(tv.Result, tv.Flags, flagsShouldPass)
-					plaintext, err := rsa.DecryptOAEP(hash.New(), nil, priv.(*rsa.PrivateKey), decodeHex(tv.Ct), decodeHex(tv.Label))
-					if wantPass {
-						if err != nil {
-							t.Fatalf("comment: %s, expected success: %s", tv.Comment, err)
-						}
-						if !bytes.Equal(plaintext, decodeHex(tv.Msg)) {
-							t.Errorf("comment: %s, unexpected plaintext: got %x, want %s", tv.Comment, plaintext, tv.Msg)
-						}
-					} else if err == nil {
-						t.Errorf("comment: %s, expected failure", tv.Comment)
-					}
-				})
-			}
-		}
-	}
-}

internal/wycheproof/rsa_pss_test.go

@@ -1,169 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package wycheproof
-
-import (
-	"crypto/rsa"
-	"testing"
-)
-
-func TestRsaPss(t *testing.T) {
-	// KeyJwk Public key in JWK format
-	type KeyJwk struct {
-	}
-
-	// Notes a description of the labels used in the test vectors
-	type Notes struct {
-	}
-
-	// SignatureTestVector
-	type SignatureTestVector struct {
-
-		// A brief description of the test case
-		Comment string `json:"comment,omitempty"`
-
-		// A list of flags
-		Flags []string `json:"flags,omitempty"`
-
-		// The message to sign
-		Msg string `json:"msg,omitempty"`
-
-		// Test result
-		Result string `json:"result,omitempty"`
-
-		// A signature for msg
-		Sig string `json:"sig,omitempty"`
-
-		// Identifier of the test case
-		TcId int `json:"tcId,omitempty"`
-	}
-
-	// RsassaPkcs1TestGroup
-	type RsassaPkcs1TestGroup struct {
-
-		// The private exponent
-		D string `json:"d,omitempty"`
-
-		// The public exponent
-		E string `json:"e,omitempty"`
-
-		// ASN encoding of the sequence [n, e]
-		KeyAsn string `json:"keyAsn,omitempty"`
-
-		// ASN encoding of the public key
-		KeyDer string `json:"keyDer,omitempty"`
-
-		// Public key in JWK format
-		KeyJwk *KeyJwk `json:"keyJwk,omitempty"`
-
-		// Pem encoded public key
-		KeyPem string `json:"keyPem,omitempty"`
-
-		// the size of the modulus in bits
-		KeySize int `json:"keySize,omitempty"`
-
-		// The modulus of the key
-		N string `json:"n,omitempty"`
-
-		// The salt length
-		SLen int `json:"sLen,omitempty"`
-
-		// the hash function used for the message
-		Sha   string                 `json:"sha,omitempty"`
-		Tests []*SignatureTestVector `json:"tests,omitempty"`
-		Type  interface{}            `json:"type,omitempty"`
-	}
-
-	// Root
-	type Root struct {
-
-		// the primitive tested in the test file
-		Algorithm string `json:"algorithm,omitempty"`
-
-		// the version of the test vectors.
-		GeneratorVersion string `json:"generatorVersion,omitempty"`
-
-		// additional documentation
-		Header []string `json:"header,omitempty"`
-
-		// a description of the labels used in the test vectors
-		Notes *Notes `json:"notes,omitempty"`
-
-		// the number of test vectors in this test
-		NumberOfTests int                     `json:"numberOfTests,omitempty"`
-		Schema        interface{}             `json:"schema,omitempty"`
-		TestGroups    []*RsassaPkcs1TestGroup `json:"testGroups,omitempty"`
-	}
-
-	flagsShouldPass := map[string]bool{
-		// A signature using a weaker hash than the EC params is not a security risk, as long as the hash is secure.
-		// https://www.imperialviolet.org/2014/05/25/strengthmatching.html
-		"WeakHash": true,
-	}
-
-	// filesOverrideToPassZeroSLen is a map of all test files
-	// and which TcIds that should be overridden to pass if the
-	// rsa.PSSOptions.SaltLength is zero.
-	// These tests expect a failure with a PSSOptions.SaltLength: 0
-	// and a signature that uses a different salt length. However,
-	// a salt length of 0 is defined as rsa.PSSSaltLengthAuto which
-	// works deterministically to auto-detect the length when
-	// verifying, so these tests actually pass as they should.
-	filesOverrideToPassZeroSLen := map[string][]int{
-		"rsa_pss_2048_sha1_mgf1_20_test.json":   []int{46, 47},
-		"rsa_pss_2048_sha256_mgf1_0_test.json":  []int{67, 68},
-		"rsa_pss_2048_sha256_mgf1_32_test.json": []int{67, 68},
-		"rsa_pss_3072_sha256_mgf1_32_test.json": []int{67, 68},
-		"rsa_pss_4096_sha256_mgf1_32_test.json": []int{67, 68},
-		"rsa_pss_4096_sha512_mgf1_32_test.json": []int{136, 137},
-		// "rsa_pss_misc_test.json": nil,  // TODO: This ones seems to be broken right now, but can enable later on.
-	}
-
-	if !boringcryptoEnabled {
-		// boringcrypto doesn't support the truncated SHA-512 hashes, so only
-		// test them if boringcrypto isn't enabled.
-		filesOverrideToPassZeroSLen["rsa_pss_2048_sha512_256_mgf1_28_test.json"] = []int{13, 14, 15}
-		filesOverrideToPassZeroSLen["rsa_pss_2048_sha512_256_mgf1_32_test.json"] = []int{13, 14}
-	}
-
-	for f := range filesOverrideToPassZeroSLen {
-		var root Root
-		readTestVector(t, f, &root)
-		for _, tg := range root.TestGroups {
-			pub := decodePublicKey(tg.KeyDer).(*rsa.PublicKey)
-			ch := parseHash(tg.Sha)
-			h := ch.New()
-			opts := &rsa.PSSOptions{
-				Hash:       ch,
-				SaltLength: rsa.PSSSaltLengthAuto,
-			}
-			// Run all the tests twice: the first time with the salt length
-			// as PSSSaltLengthAuto, and the second time with the salt length
-			// explicitly set to tg.SLen.
-			for i := 0; i < 2; i++ {
-				for _, sig := range tg.Tests {
-					h.Reset()
-					h.Write(decodeHex(sig.Msg))
-					hashed := h.Sum(nil)
-					err := rsa.VerifyPSS(pub, ch, hashed, decodeHex(sig.Sig), opts)
-					want := shouldPass(sig.Result, sig.Flags, flagsShouldPass)
-					if opts.SaltLength == 0 {
-						for _, id := range filesOverrideToPassZeroSLen[f] {
-							if sig.TcId == id {
-								want = true
-								break
-							}
-						}
-					}
-					if (err == nil) != want {
-						t.Errorf("file: %v, tcid: %d, type: %s, opts.SaltLength: %v, comment: %q, wanted success: %t", f, sig.TcId, sig.Result, opts.SaltLength, sig.Comment, want)
-					}
-				}
-				// Update opts.SaltLength for the second run of the tests.
-				opts.SaltLength = tg.SLen
-			}
-		}
-	}
-}

internal/wycheproof/rsa_signature_test.go

@@ -1,123 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package wycheproof
-
-import (
-	"crypto/rsa"
-	"testing"
-)
-
-func TestRsa(t *testing.T) {
-	// KeyJwk Public key in JWK format
-	type KeyJwk struct {
-	}
-
-	// Notes a description of the labels used in the test vectors
-	type Notes struct {
-	}
-
-	// SignatureTestVector
-	type SignatureTestVector struct {
-
-		// A brief description of the test case
-		Comment string `json:"comment,omitempty"`
-
-		// A list of flags
-		Flags []string `json:"flags,omitempty"`
-
-		// The message to sign
-		Msg string `json:"msg,omitempty"`
-
-		// Test result
-		Result string `json:"result,omitempty"`
-
-		// A signature for msg
-		Sig string `json:"sig,omitempty"`
-
-		// Identifier of the test case
-		TcId int `json:"tcId,omitempty"`
-	}
-
-	// RsassaPkcs1TestGroup
-	type RsassaPkcs1TestGroup struct {
-
-		// The private exponent
-		D string `json:"d,omitempty"`
-
-		// The public exponent
-		E string `json:"e,omitempty"`
-
-		// ASN encoding of the sequence [n, e]
-		KeyAsn string `json:"keyAsn,omitempty"`
-
-		// ASN encoding of the public key
-		KeyDer string `json:"keyDer,omitempty"`
-
-		// Public key in JWK format
-		KeyJwk *KeyJwk `json:"keyJwk,omitempty"`
-
-		// Pem encoded public key
-		KeyPem string `json:"keyPem,omitempty"`
-
-		// the size of the modulus in bits
-		KeySize int `json:"keySize,omitempty"`
-
-		// The modulus of the key
-		N string `json:"n,omitempty"`
-
-		// the hash function used for the message
-		Sha   string                 `json:"sha,omitempty"`
-		Tests []*SignatureTestVector `json:"tests,omitempty"`
-		Type  interface{}            `json:"type,omitempty"`
-	}
-
-	// Root
-	type Root struct {
-
-		// the primitive tested in the test file
-		Algorithm string `json:"algorithm,omitempty"`
-
-		// the version of the test vectors.
-		GeneratorVersion string `json:"generatorVersion,omitempty"`
-
-		// additional documentation
-		Header []string `json:"header,omitempty"`
-
-		// a description of the labels used in the test vectors
-		Notes *Notes `json:"notes,omitempty"`
-
-		// the number of test vectors in this test
-		NumberOfTests int                     `json:"numberOfTests,omitempty"`
-		Schema        interface{}             `json:"schema,omitempty"`
-		TestGroups    []*RsassaPkcs1TestGroup `json:"testGroups,omitempty"`
-	}
-
-	flagsShouldPass := map[string]bool{
-		// Omitting the parameter field in an ASN encoded integer is a legacy behavior.
-		"MissingNull": false,
-		// Keys with a modulus less than 2048 bits are supported by crypto/rsa.
-		"SmallModulus": true,
-		// Small public keys are supported by crypto/rsa.
-		"SmallPublicKey": true,
-	}
-
-	var root Root
-	readTestVector(t, "rsa_signature_test.json", &root)
-	for _, tg := range root.TestGroups {
-		pub := decodePublicKey(tg.KeyDer).(*rsa.PublicKey)
-		ch := parseHash(tg.Sha)
-		h := ch.New()
-		for _, sig := range tg.Tests {
-			h.Reset()
-			h.Write(decodeHex(sig.Msg))
-			hashed := h.Sum(nil)
-			err := rsa.VerifyPKCS1v15(pub, ch, hashed, decodeHex(sig.Sig))
-			want := shouldPass(sig.Result, sig.Flags, flagsShouldPass)
-			if (err == nil) != want {
-				t.Errorf("tcid: %d, type: %s, comment: %q, wanted success: %t", sig.TcId, sig.Result, sig.Comment, want)
-			}
-		}
-	}
-}

internal/wycheproof/wycheproof_test.go

@@ -1,141 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Package wycheproof runs a set of the Wycheproof tests
-// provided by https://github.com/google/wycheproof.
-package wycheproof
-
-import (
-	"crypto"
-	"crypto/x509"
-	"encoding/hex"
-	"encoding/json"
-	"flag"
-	"fmt"
-	"log"
-	"os"
-	"os/exec"
-	"path/filepath"
-	"testing"
-
-	_ "crypto/sha1"
-	_ "crypto/sha256"
-	_ "crypto/sha512"
-)
-
-const wycheproofModVer = "v0.0.0-20191219022705-2196000605e4"
-
-var wycheproofTestVectorsDir string
-
-func TestMain(m *testing.M) {
-	flag.Parse()
-	if flag.Lookup("test.short").Value.(flag.Getter).Get().(bool) {
-		log.Println("skipping test that downloads testdata via 'go mod download' in short mode")
-		os.Exit(0)
-	}
-	if _, err := exec.LookPath("go"); err != nil {
-		log.Printf("skipping test because 'go' command is unavailable: %v", err)
-		os.Exit(0)
-	}
-	if os.Getenv("GO_BUILDER_FLAKY_NET") != "" {
-		log.Printf("skipping test because GO_BUILDER_FLAKY_NET is set")
-		os.Exit(0)
-	}
-
-	// Download the JSON test files from github.com/google/wycheproof
-	// using `go mod download -json` so the cached source of the testdata
-	// can be used in the following tests.
-	path := "github.com/google/wycheproof@" + wycheproofModVer
-	cmd := exec.Command("go", "mod", "download", "-json", path)
-	output, err := cmd.Output()
-	if err != nil {
-		log.Fatalf("failed to run `go mod download -json %s`, output: %s", path, output)
-	}
-	var dm struct {
-		Dir string // absolute path to cached source root directory
-	}
-	if err := json.Unmarshal(output, &dm); err != nil {
-		log.Fatal(err)
-	}
-	// Now that the module has been downloaded, use the absolute path of the
-	// cached source as the root directory for all tests going forward.
-	wycheproofTestVectorsDir = filepath.Join(dm.Dir, "testvectors")
-	os.Exit(m.Run())
-}
-
-func readTestVector(t *testing.T, f string, dest interface{}) {
-	b, err := os.ReadFile(filepath.Join(wycheproofTestVectorsDir, f))
-	if err != nil {
-		t.Fatalf("failed to read json file: %v", err)
-	}
-	if err := json.Unmarshal(b, &dest); err != nil {
-		t.Fatalf("failed to unmarshal json file: %v", err)
-	}
-}
-
-func decodeHex(s string) []byte {
-	b, err := hex.DecodeString(s)
-	if err != nil {
-		panic(err)
-	}
-	return b
-}
-
-func decodePublicKey(der string) interface{} {
-	d := decodeHex(der)
-	pub, err := x509.ParsePKIXPublicKey(d)
-	if err != nil {
-		panic(fmt.Sprintf("failed to parse DER encoded public key: %v", err))
-	}
-	return pub
-}
-
-func parseHash(h string) crypto.Hash {
-	switch h {
-	case "SHA-1":
-		return crypto.SHA1
-	case "SHA-256":
-		return crypto.SHA256
-	case "SHA-224":
-		return crypto.SHA224
-	case "SHA-384":
-		return crypto.SHA384
-	case "SHA-512":
-		return crypto.SHA512
-	case "SHA-512/224":
-		return crypto.SHA512_224
-	case "SHA-512/256":
-		return crypto.SHA512_256
-	default:
-		panic(fmt.Sprintf("could not identify SHA hash algorithm: %q", h))
-	}
-}
-
-// shouldPass returns whether or not the test should pass.
-// flagsShouldPass is a map associated with whether or not
-// a flag for an "acceptable" result should pass.
-// Every possible flag value that's associated with an
-// "acceptable" result should be explicitly specified,
-// otherwise the test will panic.
-func shouldPass(result string, flags []string, flagsShouldPass map[string]bool) bool {
-	switch result {
-	case "valid":
-		return true
-	case "invalid":
-		return false
-	case "acceptable":
-		for _, flag := range flags {
-			pass, ok := flagsShouldPass[flag]
-			if !ok {
-				panic(fmt.Sprintf("unspecified flag: %q", flag))
-			}
-			if !pass {
-				return false
-			}
-		}
-		return true // There are no flags, or all are meant to pass.
-	default:
-		panic(fmt.Sprintf("unexpected result: %v", result))
-	}
-}

ocsp/ocsp.go

@@ -85,7 +85,8 @@ type certID struct {
 
 // https://tools.ietf.org/html/rfc2560#section-4.1.1
 type ocspRequest struct {
-	TBSRequest tbsRequest
+	TBSRequest        tbsRequest
+	OptionalSignature asn1.RawValue `asn1:"explicit,tag:0,optional"`
 }
 
 type tbsRequest struct {
@@ -321,10 +322,10 @@ type Request struct {
 func (req *Request) Marshal() ([]byte, error) {
 	hashAlg := getOIDFromHashAlgorithm(req.HashAlgorithm)
 	if hashAlg == nil {
-		return nil, errors.New("Unknown hash algorithm")
+		return nil, errors.New("unknown hash algorithm")
 	}
 	return asn1.Marshal(ocspRequest{
-		tbsRequest{
+		TBSRequest: tbsRequest{
 			Version: 0,
 			RequestList: []request{
 				{
@@ -418,8 +419,10 @@ func (p ParseError) Error() string {
 }
 
 // ParseRequest parses an OCSP request in DER form. It only supports
-// requests for a single certificate. Signed requests are not supported.
-// If a request includes a signature, it will result in a ParseError.
+// requests for a single certificate identifier. If a request includes
+// multiple certificate identifiers, only the first will be included in
+// the parsed Request. Signed requests are not supported. If a request
+// includes a signature, it will result in a ParseError.
 func ParseRequest(bytes []byte) (*Request, error) {
 	var req ocspRequest
 	rest, err := asn1.Unmarshal(bytes, &req)
@@ -430,6 +433,10 @@ func ParseRequest(bytes []byte) (*Request, error) {
 		return nil, ParseError("trailing data in OCSP request")
 	}
 
+	if len(req.OptionalSignature.FullBytes) > 0 {
+		return nil, ParseError("signed OCSP requests are not supported")
+	}
+
 	if len(req.TBSRequest.RequestList) == 0 {
 		return nil, ParseError("OCSP request contains no request body")
 	}

ocsp/ocsp_test.go

@@ -15,10 +15,15 @@ import (
 	"encoding/asn1"
 	"encoding/hex"
 	"encoding/pem"
+	"errors"
 	"math/big"
 	"reflect"
+	"strings"
 	"testing"
 	"time"
+
+	"golang.org/x/crypto/cryptobyte"
+	cbasn1 "golang.org/x/crypto/cryptobyte/asn1"
 )
 
 func TestOCSPDecode(t *testing.T) {
@@ -190,7 +195,7 @@ func TestOCSPRequest(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if bytes.Compare(expectedBytes, marshaledRequest) != 0 {
+	if !bytes.Equal(expectedBytes, marshaledRequest) {
 		t.Errorf(
 			"Marshaled request doesn't match expected: wanted %x, got %x",
 			expectedBytes,
@@ -199,6 +204,127 @@ func TestOCSPRequest(t *testing.T) {
 	}
 }
 
+func TestOCSPRequestErrors(t *testing.T) {
+	tests := []struct {
+		name    string
+		input   []byte
+		wantErr string
+	}{
+		{
+			name:    "signed request",
+			input:   testOCSPRequest(1, true),
+			wantErr: "signed",
+		},
+		{
+			name:    "trailing data",
+			input:   append(testOCSPRequest(1, false), 0x00),
+			wantErr: "trailing",
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			_, err := ParseRequest(tc.input)
+			if err == nil {
+				t.Fatalf(
+					"ParseRequest succeeded, want ParseError containing %q",
+					tc.wantErr,
+				)
+			}
+			var parseError ParseError
+			if !errors.As(err, &parseError) {
+				t.Fatalf("ParseRequest returned %T, want ParseError", err)
+			}
+			if !strings.Contains(parseError.Error(), tc.wantErr) {
+				t.Fatalf(
+					"ParseRequest error = %q, want it to contain %q",
+					parseError.Error(), tc.wantErr,
+				)
+			}
+		})
+	}
+}
+
+func TestOCSPMultipleCertRequest(t *testing.T) {
+	req, err := ParseRequest(testOCSPRequest(2, false))
+	if err != nil {
+		t.Fatalf("ParseRequest errored for multiple request input: %q", err)
+	}
+
+	// testOCSPRequest uses the request cert counter as the issuerNameHash,
+	// issuerKeyHash and serial. We expect the first request cert to be used
+	// (counter=1), not the second (counter=2).
+	wantHash := []byte{0x01}
+	if actual := req.IssuerNameHash; !bytes.Equal(actual, wantHash) {
+		t.Errorf(
+			"ParseRequest.IssuerNameHash returned = %q, wanted %q",
+			actual, wantHash,
+		)
+	}
+	if actual := req.IssuerKeyHash; !bytes.Equal(actual, wantHash) {
+		t.Errorf("ParseRequest.IssuerKeyHash returned = %q, wanted %q",
+			actual, wantHash)
+	}
+	wantSerial := big.NewInt(0x01)
+	if actual := req.SerialNumber; actual.Cmp(wantSerial) != 0 {
+		t.Errorf("ParseRequest.SerialNumber returned = %q, wanted %q",
+			actual, wantHash)
+	}
+}
+
+// testOCSPRequest constructs an unsupported OCSP request in DER form for testing.
+//
+// We build these by hand using cryptobyte to specifically target shapes that are
+// not supported by ParseRequest, and can't be created with CreateRequest.
+//
+// The resulting requestList will contain numCerts RequestList entries. If
+// includeSignature is true, the request will carry a signature field (with an
+// arbitrary signatureAlgorithm and signature).
+//
+// See RFC 6960, §4.1.1.
+func testOCSPRequest(numCerts int, includeSignature bool) []byte {
+	sha1AlgID, err := asn1.Marshal(pkix.AlgorithmIdentifier{
+		Algorithm:  asn1.ObjectIdentifier{1, 3, 14, 3, 2, 26},
+		Parameters: asn1.RawValue{Tag: 5 /* ASN.1 NULL */},
+	})
+	if err != nil {
+		panic(err)
+	}
+
+	var b cryptobyte.Builder
+	b.AddASN1(cbasn1.SEQUENCE, func(b *cryptobyte.Builder) { // OCSPRequest
+		b.AddASN1(cbasn1.SEQUENCE, func(b *cryptobyte.Builder) { // tbsRequest
+			b.AddASN1(cbasn1.SEQUENCE, func(b *cryptobyte.Builder) { // requestList
+				for i := 0; i < numCerts; i++ {
+					b.AddASN1(cbasn1.SEQUENCE, func(b *cryptobyte.Builder) { // Request
+						b.AddASN1(cbasn1.SEQUENCE, func(b *cryptobyte.Builder) { // CertID
+							b.AddBytes(sha1AlgID)                     // hashAlgorithm
+							b.AddASN1OctetString([]byte{byte(i + 1)}) // issuerNameHash
+							b.AddASN1OctetString([]byte{byte(i + 1)}) // issuerKeyHash
+							b.AddASN1Int64(int64(i + 1))              // serialNumber
+						})
+					})
+				}
+			})
+		})
+		if includeSignature {
+			// optionalSignature [0] EXPLICIT Signature
+			b.AddASN1(cbasn1.Tag(0).ContextSpecific().Constructed(), func(b *cryptobyte.Builder) {
+				b.AddASN1(cbasn1.SEQUENCE, func(b *cryptobyte.Builder) { // Signature
+					b.AddBytes(sha1AlgID)                              // signatureAlgorithm
+					b.AddASN1BitString([]byte{0x09, 0x0A, 0x0B, 0x0C}) // signature
+				})
+			})
+		}
+	})
+
+	der, err := b.Bytes()
+	if err != nil {
+		panic(err)
+	}
+
+	return der
+}
+
 func TestOCSPResponse(t *testing.T) {
 	leafCert, _ := hex.DecodeString(leafCertHex)
 	leaf, err := x509.ParseCertificate(leafCert)

openpgp/armor/armor.go

@@ -5,11 +5,12 @@
 // Package armor implements OpenPGP ASCII Armor, see RFC 4880. OpenPGP Armor is
 // very similar to PEM except that it has an additional CRC checksum.
 //
-// Deprecated: this package is unmaintained except for security fixes. New
-// applications should consider a more focused, modern alternative to OpenPGP
-// for their specific task. If you are required to interoperate with OpenPGP
-// systems and need a maintained package, consider a community fork.
-// See https://golang.org/issue/44226.
+// Deprecated: this package is unsafe by design, and has numerous known security
+// issues. It is not maintained, and should not be used. New applications should
+// consider a more focused, modern alternative to OpenPGP for their specific
+// task. If you are required to interoperate with OpenPGP systems and need a
+// maintained package, consider github.com/ProtonMail/go-crypto/openpgp, which
+// is a maintained fork that aims to be a drop-in replacement for this package.
 package armor
 
 import (

openpgp/clearsign/clearsign.go

@@ -8,11 +8,12 @@
 // Clearsigned messages are cryptographically signed, but the contents of the
 // message are kept in plaintext so that it can be read without special tools.
 //
-// Deprecated: this package is unmaintained except for security fixes. New
-// applications should consider a more focused, modern alternative to OpenPGP
-// for their specific task. If you are required to interoperate with OpenPGP
-// systems and need a maintained package, consider a community fork.
-// See https://golang.org/issue/44226.
+// Deprecated: this package is unsafe by design, and has numerous known security
+// issues. It is not maintained, and should not be used. New applications should
+// consider a more focused, modern alternative to OpenPGP for their specific
+// task. If you are required to interoperate with OpenPGP systems and need a
+// maintained package, consider github.com/ProtonMail/go-crypto/openpgp, which
+// is a maintained fork that aims to be a drop-in replacement for this package.
 package clearsign
 
 import (

openpgp/errors/errors.go

@@ -4,11 +4,12 @@
 
 // Package errors contains common error types for the OpenPGP packages.
 //
-// Deprecated: this package is unmaintained except for security fixes. New
-// applications should consider a more focused, modern alternative to OpenPGP
-// for their specific task. If you are required to interoperate with OpenPGP
-// systems and need a maintained package, consider a community fork.
-// See https://golang.org/issue/44226.
+// Deprecated: this package is unsafe by design, and has numerous known security
+// issues. It is not maintained, and should not be used. New applications should
+// consider a more focused, modern alternative to OpenPGP for their specific
+// task. If you are required to interoperate with OpenPGP systems and need a
+// maintained package, consider github.com/ProtonMail/go-crypto/openpgp, which
+// is a maintained fork that aims to be a drop-in replacement for this package.
 package errors
 
 import (

openpgp/packet/packet.go

@@ -5,11 +5,12 @@
 // Package packet implements parsing and serialization of OpenPGP packets, as
 // specified in RFC 4880.
 //
-// Deprecated: this package is unmaintained except for security fixes. New
-// applications should consider a more focused, modern alternative to OpenPGP
-// for their specific task. If you are required to interoperate with OpenPGP
-// systems and need a maintained package, consider a community fork.
-// See https://golang.org/issue/44226.
+// Deprecated: this package is unsafe by design, and has numerous known security
+// issues. It is not maintained, and should not be used. New applications should
+// consider a more focused, modern alternative to OpenPGP for their specific
+// task. If you are required to interoperate with OpenPGP systems and need a
+// maintained package, consider github.com/ProtonMail/go-crypto/openpgp, which
+// is a maintained fork that aims to be a drop-in replacement for this package.
 package packet
 
 import (

openpgp/read.go

@@ -4,11 +4,12 @@
 
 // Package openpgp implements high level operations on OpenPGP messages.
 //
-// Deprecated: this package is unmaintained except for security fixes. New
-// applications should consider a more focused, modern alternative to OpenPGP
-// for their specific task. If you are required to interoperate with OpenPGP
-// systems and need a maintained package, consider a community fork.
-// See https://golang.org/issue/44226.
+// Deprecated: this package is unsafe by design, and has numerous known security
+// issues. It is not maintained, and should not be used. New applications should
+// consider a more focused, modern alternative to OpenPGP for their specific
+// task. If you are required to interoperate with OpenPGP systems and need a
+// maintained package, consider github.com/ProtonMail/go-crypto/openpgp, which
+// is a maintained fork that aims to be a drop-in replacement for this package.
 package openpgp
 
 import (

openpgp/s2k/s2k.go

@@ -5,11 +5,12 @@
 // Package s2k implements the various OpenPGP string-to-key transforms as
 // specified in RFC 4800 section 3.7.1.
 //
-// Deprecated: this package is unmaintained except for security fixes. New
-// applications should consider a more focused, modern alternative to OpenPGP
-// for their specific task. If you are required to interoperate with OpenPGP
-// systems and need a maintained package, consider a community fork.
-// See https://golang.org/issue/44226.
+// Deprecated: this package is unsafe by design, and has numerous known security
+// issues. It is not maintained, and should not be used. New applications should
+// consider a more focused, modern alternative to OpenPGP for their specific
+// task. If you are required to interoperate with OpenPGP systems and need a
+// maintained package, consider github.com/ProtonMail/go-crypto/openpgp, which
+// is a maintained fork that aims to be a drop-in replacement for this package.
 package s2k
 
 import (

pbkdf2/pbkdf2.go

@@ -2,24 +2,17 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-/*
-Package pbkdf2 implements the key derivation function PBKDF2 as defined in RFC
-2898 / PKCS #5 v2.0.
-
-A key derivation function is useful when encrypting data based on a password
-or any other not-fully-random data. It uses a pseudorandom function to derive
-a secure encryption key based on the password.
-
-While v2.0 of the standard defines only one pseudorandom function to use,
-HMAC-SHA1, the drafted v2.1 specification allows use of all five FIPS Approved
-Hash Functions SHA-1, SHA-224, SHA-256, SHA-384 and SHA-512 for HMAC. To
-choose, you can pass the `New` functions from the different SHA packages to
-pbkdf2.Key.
-*/
+// Package pbkdf2 implements the key derivation function PBKDF2 as defined in
+// RFC 8018 (PKCS #5 v2.1).
+//
+// This package is a wrapper for the PBKDF2 implementation in the
+// [crypto/pbkdf2] package. It is [frozen] and is not accepting new features.
+//
+// [frozen]: https://go.dev/wiki/Frozen
 package pbkdf2
 
 import (
-	"crypto/hmac"
+	"crypto/pbkdf2"
 	"hash"
 )
 
@@ -27,51 +20,11 @@ import (
 // []byte of length keylen that can be used as cryptographic key. The key is
 // derived based on the method described as PBKDF2 with the HMAC variant using
 // the supplied hash function.
-//
-// For example, to use a HMAC-SHA-1 based PBKDF2 key derivation function, you
-// can get a derived key for e.g. AES-256 (which needs a 32-byte key) by
-// doing:
-//
-//	dk := pbkdf2.Key([]byte("some password"), salt, 4096, 32, sha1.New)
-//
-// Remember to get a good random salt. At least 8 bytes is recommended by the
-// RFC.
-//
-// Using a higher iteration count will increase the cost of an exhaustive
-// search but will also make derivation proportionally slower.
 func Key(password, salt []byte, iter, keyLen int, h func() hash.Hash) []byte {
-	prf := hmac.New(h, password)
-	hashLen := prf.Size()
-	numBlocks := (keyLen + hashLen - 1) / hashLen
-
-	var buf [4]byte
-	dk := make([]byte, 0, numBlocks*hashLen)
-	U := make([]byte, hashLen)
-	for block := 1; block <= numBlocks; block++ {
-		// N.B.: || means concatenation, ^ means XOR
-		// for each block T_i = U_1 ^ U_2 ^ ... ^ U_iter
-		// U_1 = PRF(password, salt || uint(i))
-		prf.Reset()
-		prf.Write(salt)
-		buf[0] = byte(block >> 24)
-		buf[1] = byte(block >> 16)
-		buf[2] = byte(block >> 8)
-		buf[3] = byte(block)
-		prf.Write(buf[:4])
-		dk = prf.Sum(dk)
-		T := dk[len(dk)-hashLen:]
-		copy(U, T)
-
-		// U_n = PRF(password, U_(n-1))
-		for n := 2; n <= iter; n++ {
-			prf.Reset()
-			prf.Write(U)
-			U = U[:0]
-			U = prf.Sum(U)
-			for x := range U {
-				T[x] ^= U[x]
-			}
-		}
+	out, err := pbkdf2.Key(h, string(password), salt, iter, keyLen)
+	if err != nil {
+		// FIPS 140 enforcement, or an invalid key length.
+		panic(err)
 	}
-	return dk[:keyLen]
+	return out
 }

pkcs12/crypto.go

@@ -80,6 +80,10 @@ func pbDecrypterFor(algorithm pkix.AlgorithmIdentifier, password []byte) (cipher
 		return nil, 0, err
 	}
 
+	if params.Iterations < 0 || params.Iterations > maxIterations {
+		return nil, 0, NotImplementedError("iteration count is invalid or too high")
+	}
+
 	key := cipherType.deriveKey(params.Salt, password, params.Iterations)
 	iv := cipherType.deriveIV(params.Salt, password, params.Iterations)
 

pkcs12/crypto_test.go

@@ -13,6 +13,46 @@ import (
 
 var sha1WithTripleDES = asn1.ObjectIdentifier([]int{1, 2, 840, 113549, 1, 12, 1, 3})
 
+func TestPbDecrypterForIterationLimit(t *testing.T) {
+	pass, _ := bmpString("Sesame open")
+
+	tests := []struct {
+		name       string
+		iterations int
+		wantErr    bool
+	}{
+		{"at limit", maxIterations, false},
+		{"over limit", maxIterations + 1, true},
+		{"negative", -1, true},
+		{"max int", 1<<31 - 1, true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			params, _ := asn1.Marshal(pbeParams{
+				Salt:       []byte{1, 2, 3, 4, 5, 6, 7, 8},
+				Iterations: tt.iterations,
+			})
+			alg := pkix.AlgorithmIdentifier{
+				Algorithm: sha1WithTripleDES,
+				Parameters: asn1.RawValue{
+					FullBytes: params,
+				},
+			}
+			_, _, err := pbDecrypterFor(alg, pass)
+			if tt.wantErr {
+				if _, ok := err.(NotImplementedError); !ok {
+					t.Errorf("iterations=%d: got %v, want NotImplementedError", tt.iterations, err)
+				}
+			} else {
+				if err != nil {
+					t.Errorf("iterations=%d: unexpected error: %v", tt.iterations, err)
+				}
+			}
+		})
+	}
+}
+
 func TestPbDecrypterFor(t *testing.T) {
 	params, _ := asn1.Marshal(pbeParams{
 		Salt:       []byte{1, 2, 3, 4, 5, 6, 7, 8},

pkcs12/mac.go

@@ -27,11 +27,19 @@ var (
 	oidSHA1 = asn1.ObjectIdentifier([]int{1, 3, 14, 3, 2, 26})
 )
 
+// maxIterations is a safety limit to prevent CPU exhaustion from
+// crafted PKCS#12 files with unreasonable iteration counts.
+const maxIterations = 1 << 20 // ~1 million
+
 func verifyMac(macData *macData, message, password []byte) error {
 	if !macData.Mac.Algorithm.Algorithm.Equal(oidSHA1) {
 		return NotImplementedError("unknown digest algorithm: " + macData.Mac.Algorithm.Algorithm.String())
 	}
 
+	if macData.Iterations < 0 || macData.Iterations > maxIterations {
+		return NotImplementedError("iteration count is invalid or too high")
+	}
+
 	key := pbkdf(sha1Sum, 20, 64, macData.MacSalt, password, macData.Iterations, 3, 20)
 
 	mac := hmac.New(sha1.New, key)

pkcs12/mac_test.go

@@ -5,10 +5,52 @@
 package pkcs12
 
 import (
+	"crypto/x509/pkix"
 	"encoding/asn1"
 	"testing"
 )
 
+func TestVerifyMacIterationLimit(t *testing.T) {
+	password, _ := bmpString("Sesame open")
+	message := []byte{11, 12, 13, 14, 15}
+
+	tests := []struct {
+		name       string
+		iterations int
+		wantErr    bool
+	}{
+		{"at limit", maxIterations, false},
+		{"over limit", maxIterations + 1, true},
+		{"negative", -1, true},
+		{"max int", 1<<31 - 1, true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			td := macData{
+				Mac: digestInfo{
+					Algorithm: pkix.AlgorithmIdentifier{
+						Algorithm: oidSHA1,
+					},
+					Digest: nil, // will fail MAC check, but iteration check comes first
+				},
+				MacSalt:    []byte{1, 2, 3, 4, 5, 6, 7, 8},
+				Iterations: tt.iterations,
+			}
+			err := verifyMac(&td, message, password)
+			if tt.wantErr {
+				if _, ok := err.(NotImplementedError); !ok {
+					t.Errorf("iterations=%d: got %v, want NotImplementedError", tt.iterations, err)
+				}
+			} else {
+				if _, ok := err.(NotImplementedError); ok {
+					t.Errorf("iterations=%d: got unexpected NotImplementedError", tt.iterations)
+				}
+			}
+		})
+	}
+}
+
 func TestVerifyMac(t *testing.T) {
 	td := macData{
 		Mac: digestInfo{

salsa20/salsa/salsa20_loong64.go

@@ -0,0 +1,29 @@
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build loong64 && !purego && gc
+
+package salsa
+
+import "golang.org/x/sys/cpu"
+
+// xorKeyStreamVX is implemented in salsa20_loong64.s.
+//
+//go:noescape
+func xorKeyStreamVX(out, in *byte, n uint64, nonce, key *byte)
+
+// XORKeyStream crypts bytes from in to out using the given key and counters.
+// In and out must overlap entirely or not at all. Counter
+// contains the raw salsa20 counter bytes (both nonce and block counter).
+func XORKeyStream(out, in []byte, counter *[16]byte, key *[32]byte) {
+	if len(in) == 0 {
+		return
+	}
+	_ = out[len(in)-1]
+	if cpu.Loong64.HasLSX {
+		xorKeyStreamVX(&out[0], &in[0], uint64(len(in)), &counter[0], &key[0])
+	} else {
+		genericXORKeyStream(out, in, counter, key)
+	}
+}

salsa20/salsa/salsa20_loong64.s

@@ -0,0 +1,454 @@
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !purego && gc
+
+#include "textflag.h"
+
+DATA	·constants+0x00(SB)/4, $0x61707865
+DATA	·constants+0x04(SB)/4, $0x3320646e
+DATA	·constants+0x08(SB)/4, $0x79622d32
+DATA	·constants+0x0c(SB)/4, $0x6b206574
+GLOBL	·constants(SB), NOPTR|RODATA, $32
+
+#define	NUM_ROUNDS 10
+
+// func xorKeyStreamVX(out, in *byte, n uint64, counter, key *byte)
+TEXT ·xorKeyStreamVX(SB), $0-40
+	MOVV	out+0(FP), R4
+	MOVV	in+8(FP), R5
+	MOVV	n+16(FP), R6
+	MOVV	counter+24(FP), R7
+	MOVV	key+32(FP), R8
+	MOVV	$·constants(SB), R10
+
+	BGE	R0, R6, ret
+
+	MOVV	8(R7), R9	// counter[8:16]
+
+loop256:
+	MOVV	$NUM_ROUNDS, R15
+	VXORV	V30, V30, V30	// V30 = 0
+
+	// load contants
+	VMOVQ	(R10), V0.W4
+	VMOVQ	4(R10), V5.W4
+	VMOVQ	8(R10), V10.W4
+	VMOVQ	12(R10), V15.W4
+
+	// load keys
+	VMOVQ	(R8), V1.W4
+	VMOVQ	4(R8), V2.W4
+	VMOVQ	8(R8), V3.W4
+	VMOVQ	12(R8), V4.W4
+	VMOVQ	16(R8), V11.W4
+	VMOVQ	20(R8), V12.W4
+	VMOVQ	24(R8), V13.W4
+	VMOVQ	28(R8), V14.W4
+
+	// load and update counter
+	VMOVQ	(R7), V6.W4
+	VMOVQ	4(R7), V7.W4
+
+	ADDV	$1, R9, R11
+	ADDV	$2, R9, R12
+	ADDV	$3, R9, R13
+	VMOVQ	R9, V8.W[0]
+	VMOVQ	R11, V8.W[1]
+	VMOVQ	R12, V8.W[2]
+	VMOVQ	R13, V8.W[3]
+	SRLV	$32, R9, R14
+	SRLV	$32, R11, R11
+	SRLV	$32, R12, R12
+	SRLV	$32, R13, R13
+	VMOVQ	R14, V9.W[0]
+	VMOVQ	R11, V9.W[1]
+	VMOVQ	R12, V9.W[2]
+	VMOVQ	R13, V9.W[3]
+
+	// backup V8 and V9
+	VADDV	V8, V30, V24	// V21 = V8
+	VADDV	V9, V30, V25	// V22 = V9
+
+salsa20_256:
+	VADDW	V0, V12, V26
+	VADDW	V5, V1, V27
+	VADDW	V10, V6, V28
+	VADDW	V15, V11, V29
+	VROTRW	$25, V26, V26
+	VROTRW	$25, V27, V27
+	VROTRW	$25, V28, V28
+	VROTRW	$25, V29, V29
+	VXORV	V4, V26, V4
+	VXORV	V9, V27, V9
+	VXORV	V14, V28, V14
+	VXORV	V3, V29, V3
+	VADDW	V4, V0, V26
+	VADDW	V9, V5, V27
+	VADDW	V14, V10, V28
+	VADDW	V3, V15, V29
+	VROTRW	$23, V26, V26
+	VROTRW	$23, V27, V27
+	VROTRW	$23, V28, V28
+	VROTRW	$23, V29, V29
+	VXORV	V8, V26, V8
+	VXORV	V13, V27, V13
+	VXORV	V2, V28, V2
+	VXORV	V7, V29, V7
+	VADDW	V8, V4, V26
+	VADDW	V13, V9, V27
+	VADDW	V2, V14, V28
+	VADDW	V7, V3, V29
+	VROTRW	$19, V26, V26
+	VROTRW	$19, V27, V27
+	VROTRW	$19, V28, V28
+	VROTRW	$19, V29, V29
+	VXORV	V12, V26, V12
+	VXORV	V1, V27, V1
+	VXORV	V6, V28, V6
+	VXORV	V11, V29, V11
+	VADDW	V12, V8, V26
+	VADDW	V1, V13, V27
+	VADDW	V6, V2, V28
+	VADDW	V11, V7, V29
+	VROTRW	$14, V26, V26
+	VROTRW	$14, V27, V27
+	VROTRW	$14, V28, V28
+	VROTRW	$14, V29, V29
+	VXORV	V0, V26, V0
+	VXORV	V5, V27, V5
+	VXORV	V10, V28, V10
+	VXORV	V15, V29, V15
+
+	VADDW	V0, V3, V26
+	VADDW	V5, V4, V27
+	VADDW	V10, V9, V28
+	VADDW	V15, V14, V29
+	VROTRW	$25, V26, V26
+	VROTRW	$25, V27, V27
+	VROTRW	$25, V28, V28
+	VROTRW	$25, V29, V29
+	VXORV	V1, V26, V1
+	VXORV	V6, V27, V6
+	VXORV	V11, V28, V11
+	VXORV	V12, V29, V12
+	VADDW	V1, V0, V26
+	VADDW	V6, V5, V27
+	VADDW	V11, V10, V28
+	VADDW	V12, V15, V29
+	VROTRW	$23, V26, V26
+	VROTRW	$23, V27, V27
+	VROTRW	$23, V28, V28
+	VROTRW	$23, V29, V29
+	VXORV	V2, V26, V2
+	VXORV	V7, V27, V7
+	VXORV	V8, V28, V8
+	VXORV	V13, V29, V13
+	VADDW	V2, V1, V26
+	VADDW	V7, V6, V27
+	VADDW	V8, V11, V28
+	VADDW	V13, V12, V29
+	VROTRW	$19, V26, V26
+	VROTRW	$19, V27, V27
+	VROTRW	$19, V28, V28
+	VROTRW	$19, V29, V29
+	VXORV	V3, V26, V3
+	VXORV	V4, V27, V4
+	VXORV	V9, V28, V9
+	VXORV	V14, V29, V14
+	VADDW	V3, V2, V26
+	VADDW	V4, V7, V27
+	VADDW	V9, V8, V28
+	VADDW	V14, V13, V29
+	VROTRW	$14, V26, V26
+	VROTRW	$14, V27, V27
+	VROTRW	$14, V28, V28
+	VROTRW	$14, V29, V29
+	VXORV	V0, V26, V0
+	VXORV	V5, V27, V5
+	VXORV	V10, V28, V10
+	VXORV	V15, V29, V15
+
+	SUBV	$1, R15
+	BNE	R15, R0, salsa20_256
+
+	// load origin contants
+	VMOVQ	(R10), V16.W4
+	VMOVQ	4(R10), V21.W4
+	VMOVQ	8(R10), V26.W4
+	VMOVQ	12(R10), V31.W4
+
+	// load origin keys
+	VMOVQ	(R8), V17.W4
+	VMOVQ	4(R8), V18.W4
+	VMOVQ	8(R8), V19.W4
+	VMOVQ	12(R8), V20.W4
+	VMOVQ	16(R8), V27.W4
+	VMOVQ	20(R8), V28.W4
+	VMOVQ	24(R8), V29.W4
+	VMOVQ	28(R8), V30.W4
+
+	// load origin counter
+	VMOVQ	(R7), V22.W4
+	VMOVQ	4(R7), V23.W4
+
+	// add back the initial state to generate the key stream
+	VADDW	V0, V16, V0
+	VADDW	V1, V17, V1
+	VADDW	V2, V18, V2
+	VADDW	V3, V19, V3
+	VADDW	V4, V20, V4
+	VADDW	V5, V21, V5
+	VADDW	V6, V22, V6
+	VADDW	V7, V23, V7
+	VADDW	V8, V24, V8
+	VADDW	V9, V25, V9
+	VADDW	V10, V26, V10
+	VADDW	V11, V27, V11
+	VADDW	V12, V28, V12
+	VADDW	V13, V29, V13
+	VADDW	V14, V30, V14
+	VADDW	V15, V31, V15
+
+	// shuffle
+	VILVLW	V0, V1, V16
+	VILVHW	V0, V1, V17
+	VILVLW	V2, V3, V18
+	VILVHW	V2, V3, V19
+	VILVLW	V4, V5 ,V20
+	VILVHW	V4, V5, V21
+	VILVLW	V6, V7, V22
+	VILVHW	V6, V7, V23
+	VILVLW	V8, V9, V24
+	VILVHW	V8, V9, V25
+	VILVLW	V10, V11, V26
+	VILVHW	V10, V11, V27
+	VILVLW	V12, V13, V28
+	VILVHW	V12, V13, V29
+	VILVLW	V14, V15, V30
+	VILVHW	V14, V15, V31
+	VILVLV	V16, V18, V0
+	VILVHV	V16, V18, V4
+	VILVLV	V17, V19, V8
+	VILVHV	V17, V19, V12
+	VILVLV	V20, V22, V1
+	VILVHV	V20, V22, V5
+	VILVLV	V21, V23, V9
+	VILVHV	V21, V23, V13
+	VILVLV	V24, V26, V2
+	VILVHV	V24, V26, V6
+	VILVLV	V25, V27, V10
+	VILVHV	V25, V27, V14
+	VILVLV	V28, V30, V3
+	VILVHV	V28, V30, V7
+	VILVLV	V29, V31, V11
+	VILVHV	V29, V31, V15
+
+	SGTU	$256, R6, R11
+	BNE	R11, R0, less_than_256
+
+	// load src data from R5
+	VMOVQ	0(R5), V16
+	VMOVQ	16(R5), V17
+	VMOVQ	32(R5), V18
+	VMOVQ	48(R5), V19
+	VMOVQ	64(R5), V20
+	VMOVQ	80(R5), V21
+	VMOVQ	96(R5), V22
+	VMOVQ	112(R5), V23
+	VMOVQ	128(R5), V24
+	VMOVQ	144(R5), V25
+	VMOVQ	160(R5), V26
+	VMOVQ	176(R5), V27
+	VMOVQ	192(R5), V28
+	VMOVQ	208(R5), V29
+	VMOVQ	224(R5), V30
+	VMOVQ	240(R5), V31
+
+	VXORV	V0, V16, V16
+	VXORV	V1, V17, V17
+	VXORV	V2, V18, V18
+	VXORV	V3, V19, V19
+	VXORV	V4, V20, V20
+	VXORV	V5, V21, V21
+	VXORV	V6, V22, V22
+	VXORV	V7, V23, V23
+	VXORV	V8, V24, V24
+	VXORV	V9, V25, V25
+	VXORV	V10, V26, V26
+	VXORV	V11, V27, V27
+	VXORV	V12, V28, V28
+	VXORV	V13, V29, V29
+	VXORV	V14, V30, V30
+	VXORV	V15, V31, V31
+
+	VMOVQ	V16, 0(R4)
+	VMOVQ	V17, 16(R4)
+	VMOVQ	V18, 32(R4)
+	VMOVQ	V19, 48(R4)
+	VMOVQ	V20, 64(R4)
+	VMOVQ	V21, 80(R4)
+	VMOVQ	V22, 96(R4)
+	VMOVQ	V23, 112(R4)
+	VMOVQ	V24, 128(R4)
+	VMOVQ	V25, 144(R4)
+	VMOVQ	V26, 160(R4)
+	VMOVQ	V27, 176(R4)
+	VMOVQ	V28, 192(R4)
+	VMOVQ	V29, 208(R4)
+	VMOVQ	V30, 224(R4)
+	VMOVQ	V31, 240(R4)
+
+	ADDV	$4, R9, R9	// update counter
+
+	SUBV    $256, R6, R6
+	ADDV	$256, R4, R4
+	ADDV	$256, R5, R5
+	SGTU	$256, R6, R11
+	BEQ     R11, R0, loop256
+	BEQ	R6, R0, ret
+
+less_than_256:
+	VXORV	V30, V30, V30	// V30=0
+	SGTU	$128, R6, R11
+	BNE	R11, R0, less_than_128
+	SUBV	$128, R6
+	VMOVQ	(R5), V16
+	VMOVQ	16(R5), V17
+	VMOVQ	32(R5), V18
+	VMOVQ	48(R5), V19
+	VMOVQ	64(R5), V20
+	VMOVQ	80(R5), V21
+	VMOVQ	96(R5), V22
+	VMOVQ	112(R5), V23
+	VXORV	V0, V16, V16
+	VXORV	V1, V17, V17
+	VXORV	V2, V18, V18
+	VXORV	V3, V19, V19
+	VXORV	V4, V20, V20
+	VXORV	V5, V21, V21
+	VXORV	V6, V22, V22
+	VXORV	V7, V23, V23
+	VMOVQ	V16, (R4)
+	VMOVQ	V17, 16(R4)
+	VMOVQ	V18, 32(R4)
+	VMOVQ	V19, 48(R4)
+	VMOVQ	V20, 64(R4)
+	VMOVQ	V21, 80(R4)
+	VMOVQ	V22, 96(R4)
+	VMOVQ	V23, 112(R4)
+	BEQ	R6, R0, ret
+	ADDV	$128, R5, R5
+	ADDV	$128, R4, R4
+	VADDV	V8, V30, V0
+	VADDV	V9, V30, V1
+	VADDV	V10, V30, V2
+	VADDV	V11, V30, V3
+	VADDV	V12, V30, V4
+	VADDV	V13, V30, V5
+	VADDV	V14, V30, V6
+	VADDV	V15, V30, V7
+
+less_than_128:
+	SGTU	$64, R6, R11
+	BNE	R11, R0, less_than_64
+	SUBV	$64, R6
+	VMOVQ	(R5), V16
+	VMOVQ	16(R5), V17
+	VMOVQ	32(R5), V18
+	VMOVQ	48(R5), V19
+	VXORV	V0, V16, V16
+	VXORV	V1, V17, V17
+	VXORV	V2, V18, V18
+	VXORV	V3, V19, V19
+	VMOVQ	V16, (R4)
+	VMOVQ	V17, 16(R4)
+	VMOVQ	V18, 32(R4)
+	VMOVQ	V19, 48(R4)
+	BEQ	R6, R0, ret
+	ADDV	$64, R5
+	ADDV	$64, R4
+	VADDV	V4, V30, V0
+	VADDV	V5, V30, V1
+	VADDV	V6, V30, V2
+	VADDV	V7, V30, V3
+
+less_than_64:
+	SGTU	$32, R6, R11
+	BNE	R11, R0, less_than_32
+	SUBV	$32, R6
+	VMOVQ	(R5), V16
+	VMOVQ	16(R5), V17
+	VXORV	V0, V16, V16
+	VXORV	V1, V17, V17
+	VMOVQ	V16, (R4)
+	VMOVQ	V17, 16(R4)
+	BEQ	R6, R0, ret
+	ADDV	$32, R5
+	ADDV	$32, R4
+	VADDV	V2, V30, V0
+	VADDV	V3, V30, V1
+
+less_than_32:
+	SGTU	$16, R6, R11
+	BNE	R11, R0, less_than_16
+	SUBV	$16, R6
+	VMOVQ	(R5), V16
+	VXORV	V16, V0, V16
+	VMOVQ	V16, (R4)
+	BEQ	R6, R0, ret
+	ADDV	$16, R5
+	ADDV	$16, R4
+	VADDV	V1, V30, V0
+
+less_than_16:
+	SGTU	$8, R6, R11
+	BNE	R11, R0, less_than_8
+	SUBV	$8, R6
+	VMOVQ	V0.V[0], R11
+	VMOVQ	V0.V[1], R13
+	MOVV	(R5), R12
+	XOR	R11, R12, R12
+	MOVV	R12, (R4)
+	BEQ	R6, R0, ret
+	ADDV	$8, R5
+	ADDV	$8, R4
+	VMOVQ	R13, V0.V[0]
+
+less_than_8:
+	SGTU	$4, R6, R11
+	BNE	R11, R0, less_than_4
+	SUBV	$4, R6
+	VMOVQ	V0.W[0], R11
+	VMOVQ	V0.W[1], R13
+	MOVWU	(R5), R12
+	XOR	R11, R12, R12
+	MOVWU	R12, (R4)
+	BEQ	R6, R0, ret
+	ADDV	$4, R5
+	ADDV	$4, R4
+	VMOVQ	R13, V0.W[0]
+
+less_than_4:
+	SGTU	$2, R6, R11
+	BNE	R11, R0, less_than_2
+	SUBV	$2, R6
+	VMOVQ	V0.H[0], R11
+	VMOVQ	V0.H[1], R13
+	MOVHU	(R5), R12
+	XOR	R11, R12, R12
+	MOVHU	R12, (R4)
+	BEQ	R6, R0, ret
+	ADDV	$2, R5
+	ADDV	$2, R4
+	VMOVQ	R13, V0.H[0]
+
+less_than_2:
+	VMOVQ	V0.B[0], R11
+	MOVBU	(R5), R12
+	XOR	R11, R12, R12
+	MOVBU	R12, (R4)
+
+ret:
+	RET

salsa20/salsa/salsa20_noasm.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !amd64 || purego || !gc
+//go:build (!amd64 && !loong64) || purego || !gc
 
 package salsa
 

salsa20/salsa/salsa20_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build amd64 && !purego && gc
+//go:build (amd64 || loong64) && !purego && gc
 
 package salsa
 

scrypt/scrypt.go

@@ -196,6 +196,9 @@ func Key(password, salt []byte, N, r, p, keyLen int) ([]byte, error) {
 	if N <= 1 || N&(N-1) != 0 {
 		return nil, errors.New("scrypt: N must be > 1 and a power of 2")
 	}
+	if r <= 0 || p <= 0 {
+		return nil, errors.New("scrypt: parameters must be > 0")
+	}
 	if uint64(r)*uint64(p) >= 1<<30 || r > maxInt/128/p || r > maxInt/256 || N > maxInt/128/r {
 		return nil, errors.New("scrypt: parameters are too large")
 	}

scrypt/scrypt_test.go

@@ -133,6 +133,10 @@ var bad = []testVector{
 	{"p", "s", 1, 1, 1, nil},                    // N == 1
 	{"p", "s", 7, 8, 1, nil},                    // N is not power of 2
 	{"p", "s", 16, maxInt / 2, maxInt / 2, nil}, // p * r too large
+	{"p", "s", 2, 0, 1, nil},                    // r too small
+	{"p", "s", 2, 1, 0, nil},                    // p too small
+	{"p", "s", 2, -1, 1, nil},                   // r is negative
+	{"p", "s", 2, 1, -1, nil},                   // p is negative
 }
 
 func TestKey(t *testing.T) {

ssh/agent/client.go

@@ -26,6 +26,7 @@ import (
 	"io"
 	"math/big"
 	"sync"
+	"sync/atomic"
 
 	"golang.org/x/crypto/ssh"
 )
@@ -307,17 +308,50 @@ func parseKey(in []byte) (out *Key, rest []byte, err error) {
 	}, record.Rest, nil
 }
 
+// pipelineMaxInFlight is the maximum number of outstanding requests the
+// client will pipeline to the agent before applying backpressure.
+const pipelineMaxInFlight = 32
+
 // client is a client for an ssh-agent process.
+//
+// Exactly one of pipeline / (mu, conn) is set, chosen by NewClient
+// based on whether the underlying transport implements io.Closer.
 type client struct {
-	// conn is typically a *net.UnixConn
+	// pipeline, if non-nil, dispatches requests over a pipelined
+	// connection: requests are written as soon as the wire is
+	// available and responses are routed back to per-call reply
+	// channels in FIFO order by a background reader goroutine.
+	pipeline *pipeline
+
+	// mu and conn are used in fully-serialized mode, when the
+	// transport does not implement io.Closer. Each call takes mu,
+	// writes its request, reads the matching response, and releases
+	// mu before returning. There is no background goroutine.
+	mu   sync.Mutex
 	conn io.ReadWriter
-	// mu is used to prevent concurrent access to the agent
-	mu sync.Mutex
 }
 
 // NewClient returns an Agent that talks to an ssh-agent process over
 // the given connection.
+//
+// If rw also implements io.Closer (like *net.UnixConn and ssh.Channel
+// do), the returned client pipelines concurrent requests over the
+// connection: callers can issue Sign and other operations from
+// multiple goroutines and they will be written to the agent as soon
+// as the wire is available, rather than waiting for the previous
+// responses. The ssh-agent protocol still requires responses to be
+// returned in request order, so a slow request delays subsequent
+// responses on the same connection (head-of-line blocking).
+//
+// Pipelining requires io.Closer because, on a Write error, the
+// background reader goroutine must be unblocked by closing the
+// underlying connection. When rw does not implement io.Closer
+// this is not possible, so NewClient falls back to fully
+// serializing each request: a single in-flight call at a time.
 func NewClient(rw io.ReadWriter) ExtendedAgent {
+	if rwc, ok := rw.(io.ReadWriteCloser); ok {
+		return &client{pipeline: newPipeline(rwc)}
+	}
 	return &client{conn: rw}
 }
 
@@ -340,6 +374,16 @@ func (c *client) call(req []byte) (reply interface{}, err error) {
 // bytes of the response are returned; no unmarshalling is
 // performed on the response.
 func (c *client) callRaw(req []byte) (reply []byte, err error) {
+	if c.pipeline != nil {
+		return c.pipeline.call(req)
+	}
+	return c.serialCall(req)
+}
+
+// serialCall implements the fully-serialized request/response path
+// used when the transport is not an io.Closer. It writes req under mu
+// and reads the matching response before returning.
+func (c *client) serialCall(req []byte) (reply []byte, err error) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
@@ -577,6 +621,9 @@ func (c *client) insertKey(s interface{}, comment string, constraints []byte) er
 			Constraints: constraints,
 		})
 	case ed25519.PrivateKey:
+		if len(k) != ed25519.PrivateKeySize {
+			return fmt.Errorf("agent: bad ED25519 key size: %d", len(k))
+		}
 		req = ssh.Marshal(ed25519KeyMsg{
 			Type:        ssh.KeyAlgoED25519,
 			Pub:         []byte(k)[32:],
@@ -588,6 +635,9 @@ func (c *client) insertKey(s interface{}, comment string, constraints []byte) er
 	// general idiom is to pass ed25519.PrivateKey by value, not by pointer.
 	// We still support the pointer variant for backwards compatibility.
 	case *ed25519.PrivateKey:
+		if len(*k) != ed25519.PrivateKeySize {
+			return fmt.Errorf("agent: bad ED25519 key size: %d", len(*k))
+		}
 		req = ssh.Marshal(ed25519KeyMsg{
 			Type:        ssh.KeyAlgoED25519,
 			Pub:         []byte(*k)[32:],
@@ -663,6 +713,13 @@ func (c *client) Add(key AddedKey) error {
 		constraints = append(constraints, agentConstrainConfirm)
 	}
 
+	for _, ext := range key.ConstraintExtensions {
+		constraints = append(constraints, ssh.Marshal(constrainExtensionAgentMsg{
+			ExtensionName:    ext.ExtensionName,
+			ExtensionDetails: ext.ExtensionDetails,
+		})...)
+	}
+
 	cert := key.Certificate
 	if cert == nil {
 		return c.insertKey(key.PrivateKey, key.Comment, constraints)
@@ -705,6 +762,9 @@ func (c *client) insertCert(s interface{}, cert *ssh.Certificate, comment string
 			Constraints: constraints,
 		})
 	case ed25519.PrivateKey:
+		if len(k) != ed25519.PrivateKeySize {
+			return fmt.Errorf("agent: bad ED25519 key size: %d", len(k))
+		}
 		req = ssh.Marshal(ed25519CertMsg{
 			Type:        cert.Type(),
 			CertBytes:   cert.Marshal(),
@@ -717,6 +777,9 @@ func (c *client) insertCert(s interface{}, cert *ssh.Certificate, comment string
 	// general idiom is to pass ed25519.PrivateKey by value, not by pointer.
 	// We still support the pointer variant for backwards compatibility.
 	case *ed25519.PrivateKey:
+		if len(*k) != ed25519.PrivateKeySize {
+			return fmt.Errorf("agent: bad ED25519 key size: %d", len(*k))
+		}
 		req = ssh.Marshal(ed25519CertMsg{
 			Type:        cert.Type(),
 			CertBytes:   cert.Marshal(),
@@ -854,3 +917,170 @@ func (c *client) Extension(extensionType string, contents []byte) ([]byte, error
 
 	return buf, nil
 }
+
+// pipelineResult carries either a raw agent reply or an error back to a
+// caller waiting on the response channel.
+type pipelineResult struct {
+	reply []byte
+	err   error
+}
+
+// pipeline implements request pipelining over a single agent connection.
+//
+// Writers serialize on writeMu to both register a reply channel in the
+// pending FIFO queue and write the request bytes on the wire; the two
+// must be atomic so the queue order matches the wire order. A single
+// reader goroutine decodes responses from the connection and dispatches
+// each one to the channel at the head of the queue.
+//
+// pending is a chan-of-chan acting as a FIFO queue with a fixed
+// capacity of pipelineMaxInFlight. The outer channel provides ordering
+// (reads happen in send order) and natural backpressure (a full queue
+// blocks new writers). Each inner channel is buffered with capacity
+// one and is sent to exactly once: either by the reader goroutine
+// with the agent reply, or by shutdown with the terminal error during
+// drain. The cap-one buffer makes the producer's send non-blocking,
+// so the reader and shutdown never have to wait for the caller to be
+// scheduled on the receive.
+//
+// When the reader goroutine exits (on read error or protocol
+// violation), it closes exitCh to wake any writer blocked on the
+// pending queue, then serializes with any in-flight writer to close
+// the pending channel, and finally drains the remaining entries
+// delivering the terminal error to each waiting caller. The
+// pipeline relies on conn implementing io.Closer so a writer that
+// hits a Write error can close the connection to unblock the reader
+// goroutine; NewClient is responsible for only constructing a
+// pipeline when this guarantee holds.
+type pipeline struct {
+	conn io.ReadWriteCloser
+
+	writeMu sync.Mutex
+	// pending is the FIFO queue of reply channels with capacity
+	// pipelineMaxInFlight. See type-level documentation.
+	pending chan chan pipelineResult
+	exitCh  chan struct{}
+
+	// err carries the terminal error to callers blocked on a closed
+	// pipeline. It is stored exactly once by the reader goroutine
+	// before exitCh is closed; every read happens after observing
+	// exitCh closed, so the load synchronises through the close and
+	// is guaranteed to return the stored value (never nil).
+	err atomic.Pointer[error]
+}
+
+func newPipeline(conn io.ReadWriteCloser) *pipeline {
+	p := &pipeline{
+		conn:    conn,
+		pending: make(chan chan pipelineResult, pipelineMaxInFlight),
+		exitCh:  make(chan struct{}),
+	}
+	go p.readLoop()
+	return p
+}
+
+// readLoop decodes responses from conn and dispatches them in FIFO order
+// to reply channels in pending. On any failure it invokes shutdown.
+func (p *pipeline) readLoop() {
+	var finalErr error
+	for {
+		var sizeBuf [4]byte
+		if _, err := io.ReadFull(p.conn, sizeBuf[:]); err != nil {
+			finalErr = err
+			break
+		}
+		respSize := binary.BigEndian.Uint32(sizeBuf[:])
+		if respSize > maxAgentResponseBytes {
+			finalErr = errors.New("response too large")
+			break
+		}
+		buf := make([]byte, respSize)
+		if _, err := io.ReadFull(p.conn, buf); err != nil {
+			finalErr = err
+			break
+		}
+		// Successful writes always enqueue before sending bytes, so
+		// pending has a waiting channel for this response.
+		ch := <-p.pending
+		// The reply channel is buffered with capacity 1 and is only
+		// ever written to once, so this send cannot block.
+		ch <- pipelineResult{reply: buf}
+	}
+	p.shutdown(clientErr(finalErr))
+}
+
+// shutdown is called exactly once, from readLoop, when the reader is
+// terminating. It unblocks pending writers and fails all in-flight
+// requests with finalErr.
+func (p *pipeline) shutdown(finalErr error) {
+	// Publish the terminal error before closing exitCh so any
+	// writer that subsequently observes exitCh closed sees err.
+	p.err.Store(&finalErr)
+
+	// Wake any writer blocked waiting for a slot in the pending queue.
+	close(p.exitCh)
+
+	// Wait for any writer currently inside its critical section to
+	// complete. After this lock, no new writer can reach the send on
+	// pending: they will observe exitCh closed in the select and bail
+	// out before attempting the send.
+	p.writeMu.Lock()
+	close(p.pending)
+	p.writeMu.Unlock()
+
+	// Drain entries that were enqueued but never answered, delivering
+	// the terminal error to their waiting callers. The reply channels
+	// are buffered (cap 1) and written to exactly once, so these sends
+	// cannot block.
+	for ch := range p.pending {
+		ch <- pipelineResult{err: finalErr}
+	}
+}
+
+// call sends req to the agent and returns the matching raw response.
+func (p *pipeline) call(req []byte) ([]byte, error) {
+	replyCh := make(chan pipelineResult, 1)
+
+	p.writeMu.Lock()
+
+	// Priority check: if the reader has already finished shutdown,
+	// pending is closed and sending to it would panic. Bail out now.
+	// Once we pass this check while holding writeMu, shutdown cannot
+	// complete close(pending) until we release writeMu, so the send
+	// below is safe against concurrent closure.
+	select {
+	case <-p.exitCh:
+		p.writeMu.Unlock()
+		return nil, *p.err.Load()
+	default:
+	}
+
+	// Enqueue the reply channel before writing the request, so FIFO
+	// order on the wire matches FIFO order in the pending queue. The
+	// exitCh arm handles the case where the reader errors while we
+	// block on a full queue.
+	select {
+	case p.pending <- replyCh:
+	case <-p.exitCh:
+		p.writeMu.Unlock()
+		return nil, *p.err.Load()
+	}
+
+	msg := make([]byte, 4+len(req))
+	binary.BigEndian.PutUint32(msg, uint32(len(req)))
+	copy(msg[4:], req)
+	_, werr := p.conn.Write(msg)
+	p.writeMu.Unlock()
+
+	if werr != nil {
+		// The connection is in an undefined state. Close it so the
+		// reader unblocks promptly and triggers shutdown for every
+		// other in-flight caller. NewClient guarantees conn is a
+		// real io.Closer when the pipeline is in use.
+		p.conn.Close()
+		return nil, clientErr(werr)
+	}
+
+	res := <-replyCh
+	return res.reply, res.err
+}

ssh/agent/client_pipeline_test.go

@@ -0,0 +1,649 @@
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package agent
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestPipelineParallelSigns(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	keyring := NewKeyring()
+	if err := keyring.Add(AddedKey{PrivateKey: testPrivateKeys["rsa"]}); err != nil {
+		t.Fatal(err)
+	}
+	go ServeAgent(keyring, c2)
+
+	client := NewClient(c1)
+	pubKey := testPublicKeys["rsa"]
+
+	const N = 64
+	var wg sync.WaitGroup
+	errCh := make(chan error, N)
+	for i := range N {
+		wg.Go(func() {
+			data := []byte{byte(i), byte(i >> 8)}
+			sig, err := client.Sign(pubKey, data)
+			if err != nil {
+				errCh <- err
+				return
+			}
+			if err := pubKey.Verify(data, sig); err != nil {
+				errCh <- err
+			}
+		})
+	}
+	wg.Wait()
+	close(errCh)
+	for err := range errCh {
+		t.Error(err)
+	}
+}
+
+func TestPipelineBackpressure(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+
+	const total = pipelineMaxInFlight + 8
+
+	// Fake agent: the reader drains requests from the wire independently
+	// of response production, so the write path is never self-blocked.
+	// The responder only writes a canned success reply once unblocked
+	// via gate.
+	var reqsRead int64
+	gate := make(chan struct{}, total)
+	pending := make(chan struct{}, total+pipelineMaxInFlight)
+	readerDone := make(chan struct{})
+	responderDone := make(chan struct{})
+	go func() {
+		defer close(readerDone)
+		defer close(pending)
+		for {
+			var sizeBuf [4]byte
+			if _, err := io.ReadFull(c2, sizeBuf[:]); err != nil {
+				return
+			}
+			size := binary.BigEndian.Uint32(sizeBuf[:])
+			req := make([]byte, size)
+			if _, err := io.ReadFull(c2, req); err != nil {
+				return
+			}
+			atomic.AddInt64(&reqsRead, 1)
+			pending <- struct{}{}
+		}
+	}()
+	go func() {
+		defer close(responderDone)
+		for range pending {
+			<-gate
+			var out [5]byte
+			binary.BigEndian.PutUint32(out[:4], 1)
+			out[4] = agentSuccess
+			if _, err := c2.Write(out[:]); err != nil {
+				return
+			}
+		}
+	}()
+	defer func() {
+		c1.Close()
+		c2.Close()
+		<-readerDone
+		<-responderDone
+	}()
+
+	client := NewClient(c1)
+
+	var wg sync.WaitGroup
+	errs := make(chan error, total)
+	for range total {
+		wg.Go(func() {
+			// RemoveAll maps to a simpleCall expecting agentSuccess.
+			if err := client.RemoveAll(); err != nil {
+				errs <- err
+			}
+		})
+	}
+
+	// Wait for the client to fill the pipeline.
+	deadline := time.Now().Add(2 * time.Second)
+	for time.Now().Before(deadline) {
+		if atomic.LoadInt64(&reqsRead) >= pipelineMaxInFlight {
+			break
+		}
+		time.Sleep(5 * time.Millisecond)
+	}
+	if got := atomic.LoadInt64(&reqsRead); got != pipelineMaxInFlight {
+		t.Errorf("requests in flight before any response: got %d, want %d", got, pipelineMaxInFlight)
+	}
+
+	// Release all responses; every caller should eventually complete.
+	for range total {
+		gate <- struct{}{}
+	}
+	wg.Wait()
+	close(errs)
+	for err := range errs {
+		t.Error(err)
+	}
+
+	if got := atomic.LoadInt64(&reqsRead); got != total {
+		t.Errorf("total requests received: got %d, want %d", got, total)
+	}
+}
+
+func TestPipelineConnCloseFailsInFlight(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+
+	// Server that reads requests but never replies, so all calls are
+	// parked waiting for responses.
+	serverExit := make(chan struct{})
+	go func() {
+		defer close(serverExit)
+		buf := make([]byte, 4096)
+		for {
+			if _, err := c2.Read(buf); err != nil {
+				return
+			}
+		}
+	}()
+
+	client := NewClient(c1)
+
+	const N = 8
+	var wg sync.WaitGroup
+	errs := make(chan error, N)
+	for range N {
+		wg.Go(func() {
+			errs <- client.RemoveAll()
+		})
+	}
+
+	// Give callers time to enter the pipeline, then tear down the conn.
+	time.Sleep(50 * time.Millisecond)
+	c1.Close()
+	c2.Close()
+
+	// All callers must return promptly with an error.
+	doneCh := make(chan struct{})
+	go func() {
+		wg.Wait()
+		close(doneCh)
+	}()
+	select {
+	case <-doneCh:
+	case <-time.After(5 * time.Second):
+		t.Fatal("pipelined callers did not complete after conn close")
+	}
+
+	close(errs)
+	for err := range errs {
+		if err == nil {
+			t.Error("expected error after conn close, got nil")
+		}
+	}
+
+	// Subsequent calls also fail fast rather than hanging.
+	errCh := make(chan error, 1)
+	go func() { errCh <- client.RemoveAll() }()
+	select {
+	case err := <-errCh:
+		if err == nil {
+			t.Error("expected error on post-close call, got nil")
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("post-close call hung")
+	}
+
+	<-serverExit
+}
+
+// readWriter exposes only io.Reader and io.Writer, hiding any Close
+// method on the wrapped value so NewClient cannot take the pipelined
+// path.
+type readWriter struct {
+	io.Reader
+	io.Writer
+}
+
+func TestNewClientSerialFallback(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	keyring := NewKeyring()
+	if err := keyring.Add(AddedKey{PrivateKey: testPrivateKeys["rsa"]}); err != nil {
+		t.Fatal(err)
+	}
+	go ServeAgent(keyring, c2)
+
+	rw := readWriter{Reader: c1, Writer: c1}
+	ag := NewClient(rw)
+
+	ci, ok := ag.(*client)
+	if !ok {
+		t.Fatalf("NewClient: got %T, want *client", ag)
+	}
+	if ci.pipeline != nil {
+		t.Error("NewClient with non-Closer rw: pipeline must be nil")
+	}
+	if ci.conn == nil {
+		t.Error("NewClient with non-Closer rw: conn must be set")
+	}
+
+	// The serialized path correctly handles a request/response cycle.
+	keys, err := ag.List()
+	if err != nil {
+		t.Fatalf("List: %v", err)
+	}
+	if len(keys) != 1 {
+		t.Errorf("List: got %d keys, want 1", len(keys))
+	}
+}
+
+func TestSerialFallbackParallelSigns(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	keyring := NewKeyring()
+	if err := keyring.Add(AddedKey{PrivateKey: testPrivateKeys["rsa"]}); err != nil {
+		t.Fatal(err)
+	}
+	go ServeAgent(keyring, c2)
+
+	rw := readWriter{Reader: c1, Writer: c1}
+	ag := NewClient(rw)
+
+	if ci, ok := ag.(*client); !ok {
+		t.Fatalf("NewClient: got %T, want *client", ag)
+	} else if ci.pipeline != nil {
+		t.Fatal("pipeline must be nil for non-Closer rw")
+	}
+
+	pubKey := testPublicKeys["rsa"]
+
+	const N = 64
+	var wg sync.WaitGroup
+	errCh := make(chan error, N)
+	for i := range N {
+		wg.Go(func() {
+			data := []byte{byte(i), byte(i >> 8)}
+			sig, err := ag.Sign(pubKey, data)
+			if err != nil {
+				errCh <- err
+				return
+			}
+			if err := pubKey.Verify(data, sig); err != nil {
+				errCh <- err
+			}
+		})
+	}
+	wg.Wait()
+	close(errCh)
+	for err := range errCh {
+		t.Error(err)
+	}
+}
+
+// writeFailConn wraps a net.Conn and forces Write to return an error when
+// the fail flag is set. Close delegates to the underlying conn so the test
+// can observe whether the pipeline closed it.
+type writeFailConn struct {
+	net.Conn
+	fail atomic.Bool
+}
+
+func (c *writeFailConn) Write(p []byte) (int, error) {
+	if c.fail.Load() {
+		return 0, errors.New("synthetic write failure")
+	}
+	return c.Conn.Write(p)
+}
+
+func TestPipelineWriteErrorClosesConn(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c2.Close()
+
+	// Peer that reads and discards, exiting when the conn closes.
+	serverExit := make(chan struct{})
+	go func() {
+		defer close(serverExit)
+		io.Copy(io.Discard, c2)
+	}()
+
+	wrapper := &writeFailConn{Conn: c1}
+	wrapper.fail.Store(true)
+
+	client := NewClient(wrapper)
+
+	errCh := make(chan error, 1)
+	go func() { errCh <- client.RemoveAll() }()
+
+	select {
+	case err := <-errCh:
+		if err == nil {
+			t.Fatal("expected error on forced write failure, got nil")
+		}
+		// The caller whose Write failed must receive the actual
+		// write error, not the reader's "closed connection" error
+		// from the post-shutdown drain.
+		if !strings.Contains(err.Error(), "synthetic write failure") {
+			t.Errorf("got %q, want error containing %q", err, "synthetic write failure")
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("RemoveAll hung after write failure")
+	}
+
+	// The pipeline must have closed the underlying conn, so the peer
+	// goroutine returns from its Read.
+	select {
+	case <-serverExit:
+	case <-time.After(2 * time.Second):
+		t.Fatal("connection was not closed after write failure")
+	}
+
+	// After shutdown, subsequent calls must also fail promptly.
+	errCh2 := make(chan error, 1)
+	go func() { errCh2 <- client.RemoveAll() }()
+	select {
+	case err := <-errCh2:
+		if err == nil {
+			t.Error("expected error on post-shutdown call, got nil")
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("post-shutdown call hung")
+	}
+}
+
+func TestPipelineResponseTooLarge(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	// Server: read the request, then reply with a size header that
+	// exceeds maxAgentResponseBytes. The size check fires before the
+	// body is read, so no body needs to follow.
+	serverDone := make(chan struct{})
+	go func() {
+		defer close(serverDone)
+		var sizeBuf [4]byte
+		if _, err := io.ReadFull(c2, sizeBuf[:]); err != nil {
+			return
+		}
+		size := binary.BigEndian.Uint32(sizeBuf[:])
+		if _, err := io.CopyN(io.Discard, c2, int64(size)); err != nil {
+			return
+		}
+		var out [4]byte
+		binary.BigEndian.PutUint32(out[:], maxAgentResponseBytes+1)
+		c2.Write(out[:])
+	}()
+
+	client := NewClient(c1)
+
+	errCh := make(chan error, 1)
+	go func() { errCh <- client.RemoveAll() }()
+	select {
+	case err := <-errCh:
+		if err == nil {
+			t.Fatal("expected error, got nil")
+		}
+		if !strings.Contains(err.Error(), "response too large") {
+			t.Errorf("got %q, want error containing %q", err, "response too large")
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("call hung")
+	}
+
+	// Subsequent calls must also fail: the pipeline is shut down.
+	errCh2 := make(chan error, 1)
+	go func() { errCh2 <- client.RemoveAll() }()
+	select {
+	case err := <-errCh2:
+		if err == nil {
+			t.Error("expected error on post-shutdown call, got nil")
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("post-shutdown call hung")
+	}
+
+	<-serverDone
+}
+
+func TestPipelineShutdownWithBlockedWriter(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+
+	// Server drains requests off the wire so writes never block on
+	// backpressure from the transport, but never replies. The reader
+	// goroutine therefore stays parked on Read, never dequeues from
+	// pending, and the queue fills up.
+	var reqsRead int64
+	serverExit := make(chan struct{})
+	go func() {
+		defer close(serverExit)
+		for {
+			var sizeBuf [4]byte
+			if _, err := io.ReadFull(c2, sizeBuf[:]); err != nil {
+				return
+			}
+			size := binary.BigEndian.Uint32(sizeBuf[:])
+			if _, err := io.CopyN(io.Discard, c2, int64(size)); err != nil {
+				return
+			}
+			atomic.AddInt64(&reqsRead, 1)
+		}
+	}()
+
+	client := NewClient(c1)
+
+	const total = pipelineMaxInFlight + 4
+	var wg sync.WaitGroup
+	errs := make(chan error, total)
+	for range total {
+		wg.Go(func() {
+			errs <- client.RemoveAll()
+		})
+	}
+
+	// Wait for the queue to fill: once pipelineMaxInFlight requests
+	// are on the wire, pending is at capacity and the +1 writer is
+	// blocked in the second-select arm; the rest are queued behind
+	// writeMu.
+	deadline := time.Now().Add(2 * time.Second)
+	for time.Now().Before(deadline) {
+		if atomic.LoadInt64(&reqsRead) >= pipelineMaxInFlight {
+			break
+		}
+		time.Sleep(5 * time.Millisecond)
+	}
+	if got := atomic.LoadInt64(&reqsRead); got < pipelineMaxInFlight {
+		t.Fatalf("requests on wire: got %d, want >= %d", got, pipelineMaxInFlight)
+	}
+	// Give the +1 writer a moment to actually park in the second
+	// select before we trigger shutdown.
+	time.Sleep(50 * time.Millisecond)
+
+	// Trigger shutdown: closing the server side makes the client's
+	// reader hit EOF, which calls shutdown(...).
+	c2.Close()
+
+	doneCh := make(chan struct{})
+	go func() {
+		wg.Wait()
+		close(doneCh)
+	}()
+	select {
+	case <-doneCh:
+	case <-time.After(5 * time.Second):
+		t.Fatal("blocked callers did not complete after shutdown")
+	}
+
+	close(errs)
+	for err := range errs {
+		if err == nil {
+			t.Error("expected error after shutdown, got nil")
+		}
+	}
+
+	<-serverExit
+}
+
+// multiDeviceAgent simulates an ssh-agent backed by numDevices signing
+// devices, each of which takes latency to process a request. Incoming
+// requests are round-robin dispatched to devices, and responses are
+// serialized back to the wire in request order as the protocol requires.
+//
+// The simulation does not emit a semantically meaningful reply; it just
+// writes a 1-byte SSH_AGENT_SUCCESS after the simulated latency has
+// elapsed. This is enough to exercise callRaw/simpleCall (RemoveAll).
+func multiDeviceAgent(t testing.TB, conn io.ReadWriteCloser, numDevices int, latency time.Duration) (done <-chan struct{}) {
+	t.Helper()
+
+	type job struct {
+		ready chan struct{}
+	}
+
+	devices := make([]chan job, numDevices)
+	var devicesWG sync.WaitGroup
+	for i := range numDevices {
+		devices[i] = make(chan job, 1024)
+		ch := devices[i]
+		devicesWG.Go(func() {
+			for j := range ch {
+				time.Sleep(latency)
+				close(j.ready)
+			}
+		})
+	}
+
+	// Order-preserving responder: responses are written in the same
+	// order the requests were read, regardless of which device finished
+	// first.
+	orderCh := make(chan chan struct{}, 1024)
+	responderDone := make(chan struct{})
+	go func() {
+		defer close(responderDone)
+		for ready := range orderCh {
+			<-ready
+			var out [5]byte
+			binary.BigEndian.PutUint32(out[:4], 1)
+			out[4] = agentSuccess
+			if _, err := conn.Write(out[:]); err != nil {
+				return
+			}
+		}
+	}()
+
+	finished := make(chan struct{})
+	go func() {
+		defer close(finished)
+		defer func() {
+			close(orderCh)
+			<-responderDone
+			for _, d := range devices {
+				close(d)
+			}
+			devicesWG.Wait()
+		}()
+		next := 0
+		for {
+			var sizeBuf [4]byte
+			if _, err := io.ReadFull(conn, sizeBuf[:]); err != nil {
+				return
+			}
+			size := binary.BigEndian.Uint32(sizeBuf[:])
+			if _, err := io.CopyN(io.Discard, conn, int64(size)); err != nil {
+				return
+			}
+			ready := make(chan struct{})
+			devices[next%numDevices] <- job{ready: ready}
+			next++
+			orderCh <- ready
+		}
+	}()
+
+	return finished
+}
+
+// BenchmarkPipelineMultiDevice measures throughput of the pipelined
+// agent client against a simulated multi-device agent, varying the
+// number of backend devices.
+//
+// Setup: each simulated signing device takes 2ms per request. The
+// protocol serializes responses in request order, but pipelining lets
+// the client keep multiple devices busy concurrently; throughput
+// should scale roughly linearly with numDevices up to the pipeline
+// depth (pipelineMaxInFlight).
+//
+// Run with: go test -benchmem -bench BenchmarkPipelineMultiDevice -benchtime=2s ./ssh/agent/
+func BenchmarkPipelineMultiDevice(b *testing.B) {
+	const (
+		deviceLatency = 2 * time.Millisecond
+		parallelism   = 32
+	)
+
+	for _, numDevices := range []int{1, 2, 4, 8, 16} {
+		b.Run(fmt.Sprintf("Devices=%d", numDevices), func(b *testing.B) {
+			c1, c2, err := netPipe()
+			if err != nil {
+				b.Fatalf("netPipe: %v", err)
+			}
+			serverDone := multiDeviceAgent(b, c2, numDevices, deviceLatency)
+
+			client := NewClient(c1)
+
+			b.ResetTimer()
+			b.SetParallelism(parallelism)
+			b.RunParallel(func(pb *testing.PB) {
+				for pb.Next() {
+					if err := client.RemoveAll(); err != nil {
+						b.Fatal(err)
+					}
+				}
+			})
+			b.StopTimer()
+
+			c1.Close()
+			c2.Close()
+			<-serverDone
+		})
+	}
+}

ssh/agent/client_test.go

@@ -6,6 +6,7 @@ package agent
 
 import (
 	"bytes"
+	"crypto/ed25519"
 	"crypto/rand"
 	"encoding/binary"
 	"errors"
@@ -40,7 +41,11 @@ func startOpenSSHAgent(t *testing.T) (client ExtendedAgent, socket string, clean
 	}
 
 	cmd := exec.Command(bin, "-s")
-	cmd.Env = []string{} // Do not let the user's environment influence ssh-agent behavior.
+	cmd.Env = []string{
+		// ssh-agent creates ~/.ssh and ~/.ssh/agent;
+		// ensure a writeable home directory.
+		"HOME=" + t.TempDir(),
+	} // Do not let the user's environment influence ssh-agent behavior.
 	cmd.Stderr = new(bytes.Buffer)
 	out, err := cmd.Output()
 	if err != nil {
@@ -590,3 +595,96 @@ func TestAgentExtensions(t *testing.T) {
 		t.Fatal("should have gotten agent extension failure")
 	}
 }
+
+// capturingAgent records the AddedKey observed on the server side of the
+// agent protocol. It forwards to a keyring with constraint fields stripped,
+// so the keyring's own rejection of unsupported constraints does not
+// interfere with what this test is measuring: the client-side wire
+// serialization of ConstraintExtensions.
+type capturingAgent struct {
+	Agent
+	lastAdd AddedKey
+}
+
+func newCapturingAgent() *capturingAgent {
+	return &capturingAgent{Agent: NewKeyring()}
+}
+
+func (a *capturingAgent) Add(key AddedKey) error {
+	a.lastAdd = key
+	stripped := key
+	stripped.ConstraintExtensions = nil
+	stripped.ConfirmBeforeUse = false
+	return a.Agent.Add(stripped)
+}
+
+// TestAddConstraintExtensionsWireFormat verifies that client.Add serializes
+// ConstraintExtensions into the SSH_AGENTC_ADD_IDENTITY payload and the
+// server deserializes them back into the AddedKey delivered to the backend.
+// Regressions in the client marshal loop (missing, swapped fields, wrong
+// framing) would be invisible to a keyring-based rejection test, which
+// signals only "extensions were present", not "the right ones arrived".
+func TestAddConstraintExtensionsWireFormat(t *testing.T) {
+	capturing := newCapturingAgent()
+	client, cleanup := startAgent(t, capturing)
+	defer cleanup()
+
+	constraints := []ConstraintExtension{
+		{ExtensionName: "ext-one@example.com", ExtensionDetails: []byte("details-one")},
+		{ExtensionName: "ext-two@example.com", ExtensionDetails: []byte("\x00\x01\x02\xff")},
+	}
+
+	if err := client.Add(AddedKey{
+		PrivateKey:           testPrivateKeys["rsa"],
+		Comment:              "wire-format-test",
+		ConstraintExtensions: constraints,
+	}); err != nil {
+		t.Fatalf("client.Add: %v", err)
+	}
+
+	got := capturing.lastAdd.ConstraintExtensions
+	if len(got) != len(constraints) {
+		t.Fatalf("server received %d extensions, want %d", len(got), len(constraints))
+	}
+	for i, want := range constraints {
+		if got[i].ExtensionName != want.ExtensionName {
+			t.Errorf("extension[%d] name: got %q, want %q", i, got[i].ExtensionName, want.ExtensionName)
+		}
+		if !bytes.Equal(got[i].ExtensionDetails, want.ExtensionDetails) {
+			t.Errorf("extension[%d] details: got %x, want %x", i, got[i].ExtensionDetails, want.ExtensionDetails)
+		}
+	}
+}
+
+func TestAddRejectsShortEd25519Key(t *testing.T) {
+	short := ed25519.PrivateKey(make([]byte, 16))
+	// insertCert reaches its ed25519 branch only when AddedKey.Certificate
+	// is non-nil. The length check returns before cert.Type/Marshal run, so
+	// an empty certificate is sufficient to drive the path.
+	emptyCert := &ssh.Certificate{}
+
+	cases := []struct {
+		name string
+		add  AddedKey
+	}{
+		{"insertKey value", AddedKey{PrivateKey: short}},
+		{"insertKey pointer", AddedKey{PrivateKey: &short}},
+		{"insertCert value", AddedKey{PrivateKey: short, Certificate: emptyCert}},
+		{"insertCert pointer", AddedKey{PrivateKey: &short, Certificate: emptyCert}},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			client, cleanup := startKeyringAgent(t)
+			defer cleanup()
+
+			err := client.Add(tc.add)
+			if err == nil {
+				t.Fatal("Add accepted ed25519 key shorter than 64 bytes")
+			}
+			if !strings.Contains(err.Error(), "bad ED25519 key size") {
+				t.Errorf("got error %q, want substring %q", err.Error(), "bad ED25519 key size")
+			}
+		})
+	}
+}

ssh/agent/forward.go

@@ -41,6 +41,7 @@ func ForwardToAgent(client *ssh.Client, keyring Agent) error {
 				continue
 			}
 			go ssh.DiscardRequests(reqs)
+			go io.Copy(io.Discard, channel.Stderr())
 			go func() {
 				ServeAgent(keyring, channel)
 				channel.Close()
@@ -72,6 +73,7 @@ func ForwardToRemote(client *ssh.Client, addr string) error {
 				continue
 			}
 			go ssh.DiscardRequests(reqs)
+			go io.Copy(io.Discard, channel.Stderr())
 			go forwardUnixSocket(channel, addr)
 		}
 	}()

ssh/agent/keyring.go

@@ -32,8 +32,10 @@ type keyring struct {
 
 var errLocked = errors.New("agent: locked")
 
-// NewKeyring returns an Agent that holds keys in memory.  It is safe
-// for concurrent use by multiple goroutines.
+// NewKeyring returns an Agent that holds keys in memory.  It is safe for
+// concurrent use by multiple goroutines.
+//
+// The returned Agent only supports the "lifetime" constraint.
 func NewKeyring() Agent {
 	return &keyring{}
 }
@@ -102,7 +104,7 @@ func (r *keyring) Unlock(passphrase []byte) error {
 	if !r.locked {
 		return errors.New("agent: not locked")
 	}
-	if 1 != subtle.ConstantTimeCompare(passphrase, r.passphrase) {
+	if subtle.ConstantTimeCompare(passphrase, r.passphrase) != 1 {
 		return fmt.Errorf("agent: incorrect passphrase")
 	}
 
@@ -143,15 +145,26 @@ func (r *keyring) List() ([]*Key, error) {
 	return ids, nil
 }
 
-// Insert adds a private key to the keyring. If a certificate
-// is given, that certificate is added as public key. Note that
-// any constraints given are ignored.
+// Add adds a private key to the keyring. If a certificate is given, that
+// certificate is added as public key.
+//
+// Add returns an error if key contains ConstraintExtensions or
+// ConfirmBeforeUse.
 func (r *keyring) Add(key AddedKey) error {
 	r.mu.Lock()
 	defer r.mu.Unlock()
 	if r.locked {
 		return errLocked
 	}
+
+	if key.ConfirmBeforeUse {
+		return errors.New("agent: confirm before use constraint is not supported")
+	}
+
+	if len(key.ConstraintExtensions) > 0 {
+		return errors.New("agent: constraint extensions are present but not supported")
+	}
+
 	signer, err := ssh.NewSignerFromKey(key.PrivateKey)
 
 	if err != nil {

ssh/agent/keyring_test.go

@@ -120,3 +120,42 @@ func TestAddDuplicateKey(t *testing.T) {
 		t.Fatal("key with the updated comment not found")
 	}
 }
+
+func TestAddKeyWithConstraints(t *testing.T) {
+	// Verifies the keyring refuses keys carrying constraint extensions it
+	// cannot enforce.
+	agent, cleanup := startKeyringAgent(t)
+	defer cleanup()
+
+	constraints := []ConstraintExtension{
+		{
+			ExtensionName:    "extension1",
+			ExtensionDetails: []byte("details1"),
+		},
+	}
+
+	key := testPrivateKeys["rsa"]
+
+	err := agent.Add(AddedKey{
+		PrivateKey:           key,
+		ConstraintExtensions: constraints,
+	})
+	if err == nil {
+		t.Fatal("adding a key with unsupported constraints succeeded")
+	}
+}
+
+func TestAddKeyWithConfirmBeforeUse(t *testing.T) {
+	agent, cleanup := startKeyringAgent(t)
+	defer cleanup()
+
+	key := testPrivateKeys["rsa"]
+
+	err := agent.Add(AddedKey{
+		PrivateKey:       key,
+		ConfirmBeforeUse: true,
+	})
+	if err == nil {
+		t.Fatal("adding a key with confirm before use constraint succeeded")
+	}
+}

ssh/agent/server.go

@@ -36,7 +36,7 @@ func (s *server) processRequestBytes(reqData []byte) []byte {
 		return []byte{agentFailure}
 	}
 
-	if err == nil && rep == nil {
+	if rep == nil {
 		return []byte{agentSuccess}
 	}
 
@@ -240,13 +240,35 @@ func setConstraints(key *AddedKey, constraintBytes []byte) error {
 	return nil
 }
 
+// checkRSAKeyParams enforces the same bounds as parseRSA in the ssh
+// package, and additionally caps the prime factors. Without this,
+// the rsa.PrivateKey built from an Add request would call Precompute()
+// on arbitrary inputs; the CRT coefficient recomputation is cubic in
+// |p| and can consume excessive CPU on oversized keys.
+func checkRSAKeyParams(N, E, P, Q *big.Int) error {
+	if N.BitLen() > 16384 {
+		return errors.New("agent: RSA modulus too large")
+	}
+	if P.BitLen() > 8192 || Q.BitLen() > 8192 {
+		return errors.New("agent: RSA prime too large")
+	}
+	if E.BitLen() > 24 {
+		return errors.New("agent: RSA public exponent too large")
+	}
+	e := E.Int64()
+	if e < 3 || e&1 == 0 {
+		return errors.New("agent: incorrect RSA public exponent")
+	}
+	return nil
+}
+
 func parseRSAKey(req []byte) (*AddedKey, error) {
 	var k rsaKeyMsg
 	if err := ssh.Unmarshal(req, &k); err != nil {
 		return nil, err
 	}
-	if k.E.BitLen() > 30 {
-		return nil, errors.New("agent: RSA public exponent too large")
+	if err := checkRSAKeyParams(k.N, k.E, k.P, k.Q); err != nil {
+		return nil, err
 	}
 	priv := &rsa.PrivateKey{
 		PublicKey: rsa.PublicKey{
@@ -270,6 +292,9 @@ func parseEd25519Key(req []byte) (*AddedKey, error) {
 	if err := ssh.Unmarshal(req, &k); err != nil {
 		return nil, err
 	}
+	if len(k.Priv) != ed25519.PrivateKeySize {
+		return nil, fmt.Errorf("agent: bad ED25519 key size: %d", len(k.Priv))
+	}
 	priv := ed25519.PrivateKey(k.Priv)
 
 	addedKey := &AddedKey{PrivateKey: &priv, Comment: k.Comments}
@@ -279,19 +304,60 @@ func parseEd25519Key(req []byte) (*AddedKey, error) {
 	return addedKey, nil
 }
 
+func checkDSAParams(param *dsa.Parameters) error {
+	// SSH specifies FIPS 186-2, which only provided a single size
+	// (1024 bits) DSA key. FIPS 186-3 allows for larger key
+	// sizes, which would confuse SSH.
+	if l := param.P.BitLen(); l != 1024 {
+		return fmt.Errorf("ssh: unsupported DSA key size %d", l)
+	}
+
+	// FIPS 186-2 specifies that Q must be exactly 160 bits. We must enforce
+	// this to prevent DoS attacks where an attacker sends a huge Q which makes
+	// verification slow.
+	if l := param.Q.BitLen(); l != 160 {
+		return fmt.Errorf("ssh: unsupported DSA sub-prime size %d", l)
+	}
+
+	// The generator G is an element of the group, so it must be strictly less
+	// than the modulus P.
+	if param.G.Cmp(param.P) >= 0 {
+		return errors.New("ssh: DSA generator larger than modulus")
+	}
+
+	// G must be positive.
+	if param.G.Sign() <= 0 {
+		return errors.New("ssh: DSA generator must be positive")
+	}
+
+	return nil
+}
+
 func parseDSAKey(req []byte) (*AddedKey, error) {
 	var k dsaKeyMsg
 	if err := ssh.Unmarshal(req, &k); err != nil {
 		return nil, err
 	}
+	params := dsa.Parameters{
+		P: k.P,
+		Q: k.Q,
+		G: k.G,
+	}
+	if err := checkDSAParams(&params); err != nil {
+		return nil, err
+	}
+
+	// The public value Y must be a non-zero element of the group, i.e. strictly
+	// between 0 and P, to prevent a maliciously oversized Y from slowing
+	// signature operations.
+	if k.Y.Sign() <= 0 || k.Y.Cmp(k.P) >= 0 {
+		return nil, errors.New("agent: DSA public value Y out of range")
+	}
+
 	priv := &dsa.PrivateKey{
 		PublicKey: dsa.PublicKey{
-			Parameters: dsa.Parameters{
-				P: k.P,
-				Q: k.Q,
-				G: k.G,
-			},
-			Y: k.Y,
+			Parameters: params,
+			Y:          k.Y,
 		},
 		X: k.X,
 	}
@@ -336,6 +402,9 @@ func parseEd25519Cert(req []byte) (*AddedKey, error) {
 	if err != nil {
 		return nil, err
 	}
+	if len(k.Priv) != ed25519.PrivateKeySize {
+		return nil, fmt.Errorf("agent: bad ED25519 key size: %d", len(k.Priv))
+	}
 	priv := ed25519.PrivateKey(k.Priv)
 	cert, ok := pubKey.(*ssh.Certificate)
 	if !ok {
@@ -393,8 +462,8 @@ func parseRSACert(req []byte) (*AddedKey, error) {
 		return nil, fmt.Errorf("agent: Unmarshal failed to parse public key: %v", err)
 	}
 
-	if rsaPub.E.BitLen() > 30 {
-		return nil, errors.New("agent: RSA public exponent too large")
+	if err := checkRSAKeyParams(rsaPub.N, rsaPub.E, k.P, k.Q); err != nil {
+		return nil, err
 	}
 
 	priv := rsa.PrivateKey{

ssh/agent/server_test.go

@@ -9,10 +9,12 @@ import (
 	"crypto/rand"
 	"fmt"
 	"io"
+	"math/big"
 	pseudorand "math/rand"
 	"reflect"
 	"strings"
 	"testing"
+	"time"
 
 	"golang.org/x/crypto/ssh"
 )
@@ -88,6 +90,96 @@ func TestSetupForwardAgent(t *testing.T) {
 	conn.Close()
 }
 
+func TestForwardAgentDiscardsStderr(t *testing.T) {
+	a, b, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer a.Close()
+	defer b.Close()
+
+	serverConf := ssh.ServerConfig{
+		NoClientAuth: true,
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+	incoming := make(chan *ssh.ServerConn, 1)
+	go func() {
+		conn, _, _, err := ssh.NewServerConn(a, &serverConf)
+		incoming <- conn
+		if err != nil {
+			t.Errorf("NewServerConn error: %v", err)
+			return
+		}
+	}()
+
+	conf := ssh.ClientConfig{
+		HostKeyCallback: ssh.InsecureIgnoreHostKey(),
+	}
+	conn, chans, reqs, err := ssh.NewClientConn(b, "", &conf)
+	if err != nil {
+		t.Fatalf("NewClientConn: %v", err)
+	}
+	client := ssh.NewClient(conn, chans, reqs)
+	defer client.Close()
+
+	if err := ForwardToAgent(client, NewKeyring()); err != nil {
+		t.Fatalf("ForwardToAgent: %v", err)
+	}
+
+	server := <-incoming
+	if server == nil {
+		t.Fatal("Unable to get server")
+	}
+	defer server.Close()
+
+	ch, chanReqs, err := server.OpenChannel(channelType, nil)
+	if err != nil {
+		t.Fatalf("OpenChannel(%q): %v", channelType, err)
+	}
+	go ssh.DiscardRequests(chanReqs)
+	defer ch.Close()
+
+	// Write more than the default channel receive window (2 MiB) on the
+	// stderr stream. If the forwarder did not drain it the remote window
+	// would be exhausted and this write would block forever, because no
+	// window-adjust messages are emitted for an extended stream that is
+	// never read.
+	const payload = 4 * 1024 * 1024
+	done := make(chan error, 1)
+	go func() {
+		buf := make([]byte, 32*1024)
+		remaining := payload
+		for remaining > 0 {
+			n := len(buf)
+			if remaining < n {
+				n = remaining
+			}
+			w, err := ch.Stderr().Write(buf[:n])
+			if err != nil {
+				done <- err
+				return
+			}
+			remaining -= w
+		}
+		done <- nil
+	}()
+
+	select {
+	case err := <-done:
+		if err != nil {
+			t.Fatalf("write to stderr: %v", err)
+		}
+	case <-time.After(10 * time.Second):
+		t.Fatal("write to stderr blocked: ForwardToAgent is not draining channel.Stderr()")
+	}
+
+	// The agent must still be reachable on the main stream after the
+	// stderr traffic.
+	if _, err := NewClient(ch).List(); err != nil {
+		t.Fatalf("List after stderr flood: %v", err)
+	}
+}
+
 func TestV1ProtocolMessages(t *testing.T) {
 	c1, c2, err := netPipe()
 	if err != nil {
@@ -154,6 +246,75 @@ func addKeyToAgent(key crypto.PrivateKey) error {
 	return verifyKey(sshAgent)
 }
 
+func TestParseDSAKeyHugeQ(t *testing.T) {
+	P := new(big.Int).Lsh(big.NewInt(1), 1023)
+	Q := new(big.Int).Lsh(big.NewInt(1), 20000) // very large
+	// G and Y: dummy values, just needs to be < P to pass that specific check.
+	G := big.NewInt(2)
+	Y := big.NewInt(5)
+
+	req := ssh.Marshal(dsaKeyMsg{
+		Type: ssh.InsecureKeyAlgoDSA,
+		P:    P,
+		Q:    Q,
+		G:    G,
+		Y:    Y,
+		X:    big.NewInt(1),
+	})
+
+	_, err := parseDSAKey(req)
+	if err == nil {
+		t.Fatal("parseDSAKey accepted a DSA key with large Q")
+	}
+
+	expectedError := "unsupported DSA sub-prime size"
+	if !strings.Contains(err.Error(), expectedError) {
+		t.Errorf("unexpected error message: got %q, want substring %q", err.Error(), expectedError)
+	}
+}
+
+func TestParseDSAKeyYOutOfRange(t *testing.T) {
+	// Valid 1024/160 parameters (values don't need to be a real DSA group,
+	// they only need to pass the checkDSAParams bit-length checks and the
+	// G < P / G > 0 checks).
+	P := new(big.Int).Lsh(big.NewInt(1), 1023)
+	P.SetBit(P, 0, 1) // make P odd so it can pass as a prime candidate shape
+	Q := new(big.Int).Lsh(big.NewInt(1), 159)
+	Q.SetBit(Q, 0, 1)
+	G := big.NewInt(2)
+
+	for _, tc := range []struct {
+		name string
+		Y    *big.Int
+	}{
+		{"Y_zero", big.NewInt(0)},
+		{"Y_negative", big.NewInt(-1)},
+		{"Y_equals_P", new(big.Int).Set(P)},
+		{"Y_greater_than_P", new(big.Int).Add(P, big.NewInt(1))},
+		{"Y_much_greater_than_P", new(big.Int).Lsh(big.NewInt(1), 20000)},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			req := ssh.Marshal(dsaKeyMsg{
+				Type: ssh.InsecureKeyAlgoDSA,
+				P:    P,
+				Q:    Q,
+				G:    G,
+				Y:    tc.Y,
+				X:    big.NewInt(1),
+			})
+
+			_, err := parseDSAKey(req)
+			if err == nil {
+				t.Fatalf("parseDSAKey accepted a DSA key with Y=%s (P=%s)", tc.Y, P)
+			}
+			expectedError := "DSA public value Y out of range"
+			if !strings.Contains(err.Error(), expectedError) {
+				t.Errorf("unexpected error message: got %q, want substring %q", err.Error(), expectedError)
+			}
+		})
+	}
+}
+
 func TestKeyTypes(t *testing.T) {
 	for k, v := range testPrivateKeys {
 		if err := addKeyToAgent(v); err != nil {
@@ -271,3 +432,35 @@ func TestParseConstraints(t *testing.T) {
 		t.Errorf("unexpected error: %v", err)
 	}
 }
+
+func TestParseEd25519KeyShortPanic(t *testing.T) {
+	msg := ssh.Marshal(ed25519KeyMsg{
+		Type: ssh.KeyAlgoED25519,
+		Pub:  []byte{1, 2, 3},
+		Priv: []byte{1, 2, 3, 4, 5},
+	})
+
+	a, b, err := netPipe()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer a.Close()
+	defer b.Close()
+
+	done := make(chan error, 1)
+	go func() { done <- ServeAgent(NewKeyring(), a) }()
+
+	c := NewClient(b)
+	_, err = c.(*client).call(msg)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	keys, err := c.List()
+	if err != nil {
+		t.Fatalf("agent died: %v", err)
+	}
+	if len(keys) != 0 {
+		t.Error("short ed25519 key was accepted into keyring")
+	}
+}

ssh/buffer_test.go

@@ -38,7 +38,7 @@ func TestBufferReadwrite(t *testing.T) {
 	b.write(alphabet[5:15])
 	r, _ = b.Read(make([]byte, 10))
 	r2, _ := b.Read(make([]byte, 10))
-	if r != 10 || r2 != 5 || 15 != r+r2 {
+	if r != 10 || r2 != 5 || r+r2 != 15 {
 		t.Fatal("Expected written == read == 15")
 	}
 }

ssh/certs.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"slices"
 	"sort"
 	"time"
 )
@@ -229,15 +230,20 @@ func parseCert(in []byte, privAlgo string) (*Certificate, error) {
 		return nil, err
 	}
 	c.Reserved = g.Reserved
+	// Reject a certificate whose signature key is itself a certificate before
+	// parsing it. Certificates signed by certificates are not supported (see
+	// PROTOCOL.certkeys), and rejecting after ParsePublicKey returns would allow
+	// a chain of nested certificates to recurse once per level, exhausting the
+	// goroutine stack.
+	if sigAlgo, _, ok := parseString(g.SignatureKey); !ok {
+		return nil, errShortRead
+	} else if _, ok := certKeyAlgoNames[string(sigAlgo)]; ok {
+		return nil, fmt.Errorf("ssh: the signature key type %q is invalid for certificates", sigAlgo)
+	}
 	k, err := ParsePublicKey(g.SignatureKey)
 	if err != nil {
 		return nil, err
 	}
-	// The Type() function is intended to return only certificate key types, but
-	// we use certKeyAlgoNames anyway for safety, to match [Certificate.Type].
-	if _, ok := certKeyAlgoNames[k.Type()]; ok {
-		return nil, fmt.Errorf("ssh: the signature key type %q is invalid for certificates", k.Type())
-	}
 	c.SignatureKey = k
 	c.Signature, rest, ok = parseSignatureBody(g.Signature)
 	if !ok || len(rest) > 0 {
@@ -300,8 +306,11 @@ const sourceAddressCriticalOption = "source-address"
 // minimally, the IsAuthority callback should be set.
 type CertChecker struct {
 	// SupportedCriticalOptions lists the CriticalOptions that the
-	// server application layer understands. These are only used
-	// for user certificates.
+	// application layer understands. A certificate carrying a critical
+	// option that is not listed here is rejected.
+	// CertChecker.Authenticate additionally accepts the source-address
+	// option, which the server enforces on the Permissions that
+	// Authenticate returns.
 	SupportedCriticalOptions []string
 
 	// IsUserAuthority should return true if the key is recognized as an
@@ -348,6 +357,9 @@ func (c *CertChecker) CheckHostKey(addr string, remote net.Addr, key PublicKey)
 	if cert.CertType != HostCert {
 		return fmt.Errorf("ssh: certificate presented as a host key has type %d", cert.CertType)
 	}
+	if c.IsHostAuthority == nil {
+		return errors.New("ssh: cannot verify certificate, IsHostAuthority not set")
+	}
 	if !c.IsHostAuthority(cert.SignatureKey, addr) {
 		return fmt.Errorf("ssh: no authorities for hostname: %v", addr)
 	}
@@ -361,8 +373,9 @@ func (c *CertChecker) CheckHostKey(addr string, remote net.Addr, key PublicKey)
 	return c.CheckCert(hostname, cert)
 }
 
-// Authenticate checks a user certificate. Authenticate can be used as
-// a value for ServerConfig.PublicKeyCallback.
+// Authenticate checks a user certificate. Authenticate can be used as a value
+// for ServerConfig.PublicKeyCallback. The source-address critical option is
+// allowed, as it will be enforced by the server.
 func (c *CertChecker) Authenticate(conn ConnMetadata, pubKey PublicKey) (*Permissions, error) {
 	cert, ok := pubKey.(*Certificate)
 	if !ok {
@@ -375,11 +388,17 @@ func (c *CertChecker) Authenticate(conn ConnMetadata, pubKey PublicKey) (*Permis
 	if cert.CertType != UserCert {
 		return nil, fmt.Errorf("ssh: cert has type %d", cert.CertType)
 	}
+	if c.IsUserAuthority == nil {
+		return nil, errors.New("ssh: cannot verify certificate, IsUserAuthority not set")
+	}
 	if !c.IsUserAuthority(cert.SignatureKey) {
 		return nil, fmt.Errorf("ssh: certificate signed by unrecognized authority")
 	}
-
-	if err := c.CheckCert(conn.User(), cert); err != nil {
+	// The source-address critical option is enforced by serverAuthenticate,
+	// so it is supported regardless of SupportedCriticalOptions
+	cc := *c
+	cc.SupportedCriticalOptions = append(slices.Clip(cc.SupportedCriticalOptions), sourceAddressCriticalOption)
+	if err := cc.CheckCert(conn.User(), cert); err != nil {
 		return nil, err
 	}
 
@@ -387,27 +406,15 @@ func (c *CertChecker) Authenticate(conn ConnMetadata, pubKey PublicKey) (*Permis
 }
 
 // CheckCert checks CriticalOptions, ValidPrincipals, revocation, timestamp and
-// the signature of the certificate.
+// the signature of the certificate. Critical options that are not listed in
+// SupportedCriticalOptions are rejected.
 func (c *CertChecker) CheckCert(principal string, cert *Certificate) error {
 	if c.IsRevoked != nil && c.IsRevoked(cert) {
 		return fmt.Errorf("ssh: certificate serial %d revoked", cert.Serial)
 	}
 
 	for opt := range cert.CriticalOptions {
-		// sourceAddressCriticalOption will be enforced by
-		// serverAuthenticate
-		if opt == sourceAddressCriticalOption {
-			continue
-		}
-
-		found := false
-		for _, supp := range c.SupportedCriticalOptions {
-			if supp == opt {
-				found = true
-				break
-			}
-		}
-		if !found {
+		if !slices.Contains(c.SupportedCriticalOptions, opt) {
 			return fmt.Errorf("ssh: unsupported critical option %q in certificate", opt)
 		}
 	}
@@ -438,7 +445,17 @@ func (c *CertChecker) CheckCert(principal string, cert *Certificate) error {
 	if before := int64(cert.ValidBefore); cert.ValidBefore != uint64(CertTimeInfinity) && (unixNow >= before || before < 0) {
 		return fmt.Errorf("ssh: cert has expired")
 	}
-	if err := cert.SignatureKey.Verify(cert.bytesForSigning(), cert.Signature); err != nil {
+	// Match OpenSSH: the SK user-presence flag is never enforced on a
+	// certificate's CA signature. OpenSSH calls sshkey_verify with
+	// detailsp==NULL in sshkey.c:cert_parse, so the UP/UV flags are
+	// not even extracted. The UP bit on a CA signature reflects the
+	// CA operator's presence at signing time, which has no bearing on
+	// whether the user being authenticated is present now; enforcing
+	// it here would only break interop with certificates issued by
+	// non-interactive SK CAs. skKeyWithoutUP is a no-op for non-SK
+	// keys (the common case).
+	caKey := skKeyWithoutUP(cert.SignatureKey)
+	if err := caKey.Verify(cert.bytesForSigning(), cert.Signature); err != nil {
 		return fmt.Errorf("ssh: certificate signature does not verify")
 	}
 

ssh/certs_test.go

@@ -9,10 +9,13 @@ import (
 	"crypto/ecdsa"
 	"crypto/elliptic"
 	"crypto/rand"
+	"crypto/sha256"
 	"fmt"
 	"io"
+	"math/big"
 	"net"
 	"reflect"
+	"strings"
 	"testing"
 	"time"
 
@@ -43,6 +46,34 @@ func TestParseCert(t *testing.T) {
 	}
 }
 
+func TestParseCertNestedSignatureKey(t *testing.T) {
+	signer, err := NewSignerFromKey(testPrivateKeys["ed25519"])
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cert := &Certificate{
+		Key:         signer.PublicKey(),
+		CertType:    UserCert,
+		ValidBefore: CertTimeInfinity,
+	}
+	if err := cert.SignCert(rand.Reader, signer); err != nil {
+		t.Fatal(err)
+	}
+
+	inner := *cert
+	cert.SignatureKey = &inner
+	blob := cert.Marshal()
+
+	_, err = ParsePublicKey(blob)
+	if err == nil {
+		t.Fatal("ParsePublicKey: expected error for certificate signed by a certificate, got nil")
+	}
+	if !strings.Contains(err.Error(), "invalid for certificates") {
+		t.Errorf("ParsePublicKey: got error %q, want it to mention the signature key is invalid for certificates", err)
+	}
+}
+
 // Cert generated by ssh-keygen OpenSSH_6.8p1 OS X 10.10.3
 // % ssh-keygen -s ca -I testcert -O source-address=192.168.1.0/24 -O force-command=/bin/sleep user.pub
 // user.pub key: ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDACh1rt2DXfV3hk6fszSQcQ/rueMId0kVD9U7nl8cfEnFxqOCrNT92g4laQIGl2mn8lsGZfTLg8ksHq3gkvgO3oo/0wHy4v32JeBOHTsN5AL4gfHNEhWeWb50ev47hnTsRIt9P4dxogeUo/hTu7j9+s9lLpEQXCvq6xocXQt0j8MV9qZBBXFLXVT3cWIkSqOdwt/5ZBg+1GSrc7WfCXVWgTk4a20uPMuJPxU4RQwZW6X3+O8Pqo8C3cW0OzZRFP6gUYUKUsTI5WntlS+LAxgw1mZNsozFGdbiOPRnEryE3SRldh9vjDR3tin1fGpA5P7+CEB/bqaXtG3V+F2OkqaMN
@@ -128,6 +159,103 @@ func TestValidateCert(t *testing.T) {
 	}
 }
 
+// signSKCert builds an SK-ECDSA signature over cert.bytesForSigning()
+// using caKey as the simulated hardware token. The SK signing flags
+// byte (UP bit and others) is caller-controlled so tests can exercise
+// the user-presence enforcement paths. caApp is the SK application
+// string (typically "ssh:").
+func signSKCert(t *testing.T, cert *Certificate, caKey *ecdsa.PrivateKey, caApp string, flags byte) {
+	t.Helper()
+	cert.SignatureKey = &skECDSAPublicKey{
+		application: caApp,
+		PublicKey:   caKey.PublicKey,
+	}
+	cert.Nonce = make([]byte, 32)
+	if _, err := rand.Read(cert.Nonce); err != nil {
+		t.Fatal(err)
+	}
+
+	h := sha256.New()
+	h.Write([]byte(caApp))
+	appDigest := h.Sum(nil)
+	h.Reset()
+	h.Write(cert.bytesForSigning())
+	dataDigest := h.Sum(nil)
+
+	var counter uint32 = 1
+	blob := struct {
+		ApplicationDigest []byte `ssh:"rest"`
+		Flags             byte
+		Counter           uint32
+		MessageDigest     []byte `ssh:"rest"`
+	}{appDigest, flags, counter, dataDigest}
+	h.Reset()
+	h.Write(Marshal(blob))
+	digest := h.Sum(nil)
+
+	r, s, err := ecdsa.Sign(rand.Reader, caKey, digest)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cert.Signature = &Signature{
+		Format: KeyAlgoSKECDSA256,
+		Blob:   Marshal(struct{ R, S *big.Int }{r, s}),
+		Rest: Marshal(struct {
+			Flags   byte
+			Counter uint32
+		}{flags, counter}),
+	}
+}
+
+// TestCheckCertSKAuthorityNoUPRequired pins the OpenSSH-parity
+// behavior of CertChecker.CheckCert for SK CA signatures: a
+// certificate signed by an SK CA that produced a UP=0 signature is
+// accepted, because the UP bit on a CA signature has no bearing on
+// the current user authentication (see sshkey.c:cert_parse, which
+// passes detailsp==NULL to sshkey_verify). Without this, certs issued
+// by non-interactive SK CAs would fail to verify.
+func TestCheckCertSKAuthorityNoUPRequired(t *testing.T) {
+	caKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	userKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	userPub, err := NewPublicKey(&userKey.PublicKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	mkCert := func(flags byte) *Certificate {
+		c := &Certificate{
+			CertType:        UserCert,
+			Key:             userPub,
+			ValidBefore:     CertTimeInfinity,
+			ValidPrincipals: []string{"user"},
+		}
+		signSKCert(t, c, caKey, "ssh:", flags)
+		return c
+	}
+
+	checker := CertChecker{
+		IsUserAuthority: func(k PublicKey) bool {
+			caSK := &skECDSAPublicKey{application: "ssh:", PublicKey: caKey.PublicKey}
+			return bytes.Equal(k.Marshal(), caSK.Marshal())
+		},
+	}
+
+	// Both UP=0 and UP=1 CA signatures verify: UP is not enforced
+	// here, matching OpenSSH.
+	if err := checker.CheckCert("user", mkCert(0)); err != nil {
+		t.Errorf("UP=0 CA signature must verify (OpenSSH parity): %v", err)
+	}
+	if err := checker.CheckCert("user", mkCert(flagUserPresence)); err != nil {
+		t.Errorf("UP=1 CA signature must verify: %v", err)
+	}
+}
+
 func TestValidateCertTime(t *testing.T) {
 	cert := Certificate{
 		ValidPrincipals: []string{"user"},
@@ -257,6 +385,82 @@ func TestHostKeyCert(t *testing.T) {
 	}
 }
 
+type testConnMeta struct {
+	ConnMetadata
+	user string
+}
+
+func (c testConnMeta) User() string { return c.user }
+
+func TestCertCriticalOptions(t *testing.T) {
+	appended := make([]string, 2)
+	appended[0], appended[1] = "supported-option", "appended-option"
+	supported := appended[:1]
+
+	checker := &CertChecker{
+		SupportedCriticalOptions: supported,
+		IsHostAuthority: func(p PublicKey, addr string) bool {
+			return bytes.Equal(testPublicKeys["ecdsa"].Marshal(), p.Marshal())
+		},
+		IsUserAuthority: func(p PublicKey) bool {
+			return bytes.Equal(testPublicKeys["ecdsa"].Marshal(), p.Marshal())
+		},
+	}
+
+	for _, test := range []struct {
+		name string
+		opts map[string]string
+		// succeed is the expected outcome of CheckHostKey, for a host
+		// certificate, and of CheckCert, for a user certificate.
+		succeed bool
+		// authSucceed is the expected outcome of Authenticate.
+		authSucceed bool
+	}{
+		{name: "no critical options", opts: nil, succeed: true, authSucceed: true},
+		{name: "source-address", opts: map[string]string{sourceAddressCriticalOption: "192.168.1.0/24"}, authSucceed: true},
+		{name: "unknown option", opts: map[string]string{"unknown-option": ""}},
+		{name: "supported option", opts: map[string]string{"supported-option": ""}, succeed: true, authSucceed: true},
+	} {
+		hostCert := &Certificate{
+			ValidPrincipals: []string{"hostname"},
+			Key:             testPublicKeys["rsa"],
+			ValidBefore:     CertTimeInfinity,
+			CertType:        HostCert,
+			Permissions:     Permissions{CriticalOptions: test.opts},
+		}
+		if err := hostCert.SignCert(rand.Reader, testSigners["ecdsa"]); err != nil {
+			t.Fatalf("SignCert: %v", err)
+		}
+
+		if err := checker.CheckHostKey("hostname:22", nil, hostCert); (err == nil) != test.succeed {
+			t.Errorf("CheckHostKey(%s): got %v, want success=%v", test.name, err, test.succeed)
+		}
+
+		userCert := &Certificate{
+			ValidPrincipals: []string{"user"},
+			Key:             testPublicKeys["rsa"],
+			ValidBefore:     CertTimeInfinity,
+			CertType:        UserCert,
+			Permissions:     Permissions{CriticalOptions: test.opts},
+		}
+		if err := userCert.SignCert(rand.Reader, testSigners["ecdsa"]); err != nil {
+			t.Fatalf("SignCert: %v", err)
+		}
+
+		if err := checker.CheckCert("user", userCert); (err == nil) != test.succeed {
+			t.Errorf("CheckCert(%s): got %v, want success=%v", test.name, err, test.succeed)
+		}
+
+		if _, err := checker.Authenticate(testConnMeta{user: "user"}, userCert); (err == nil) != test.authSucceed {
+			t.Errorf("Authenticate(%s): got %v, want success=%v", test.name, err, test.authSucceed)
+		}
+	}
+
+	if appended[1] != "appended-option" {
+		t.Errorf("Authenticate overwrote the caller's slice: got %q, want %q", appended[1], "appended-option")
+	}
+}
+
 type legacyRSASigner struct {
 	Signer
 }
@@ -330,10 +534,6 @@ func TestCertTypes(t *testing.T) {
 			go NewServerConn(c1, conf)
 
 			priv := m.signer
-			if err != nil {
-				t.Fatalf("error generating ssh pubkey: %v", err)
-			}
-
 			cert := &Certificate{
 				CertType: UserCert,
 				Key:      priv.PublicKey(),

ssh/channel.go

@@ -11,6 +11,7 @@ import (
 	"io"
 	"log"
 	"sync"
+	"sync/atomic"
 )
 
 const (
@@ -131,11 +132,17 @@ func (r RejectionReason) String() string {
 	return fmt.Sprintf("unknown reason %d", int(r))
 }
 
-func min(a uint32, b int) uint32 {
-	if a < uint32(b) {
-		return a
+// minPayloadSize returns min(limit, length) clamped to a uint32. It is used
+// to compute the size of the next channel data packet from the remaining
+// payload. The comparison is done in int64 because length is an int — on
+// 64-bit systems len(data) can exceed 2^32, and a direct uint32(length)
+// cast would silently truncate to 0 at every multiple of 2^32, causing
+// WriteExtended's loop to spin without making progress.
+func minPayloadSize(limit uint32, length int) uint32 {
+	if int64(length) > int64(limit) {
+		return limit
 	}
-	return uint32(b)
+	return uint32(length)
 }
 
 type channelDirection uint8
@@ -166,6 +173,12 @@ type channel struct {
 	// (for outbound channels) or received (for inbound channels).
 	decided bool
 
+	// established is set to true once the channel is open and may carry normal
+	// channel traffic: for an outbound channel when the peer's open
+	// confirmation is received, for an inbound channel when the local side
+	// accepts it. It is set and read from different goroutines.
+	established atomic.Bool
+
 	// direction contains either channelOutbound, for channels created
 	// locally, or channelInbound, for channels created by the peer.
 	direction channelDirection
@@ -177,6 +190,12 @@ type channel struct {
 	// with WantReply=true outstanding.  This lock is held by a
 	// goroutine that has such an outgoing request pending.
 	sentRequestMu sync.Mutex
+	// sentRequestPending is set to true while a SendRequest call with
+	// WantReply=true is in flight. handlePacket uses it as a gate: responses
+	// arriving while no request is pending are dropped to prevent a
+	// misbehaving peer from stalling the mux read loop by filling ch.msg
+	// with unsolicited channelRequestSuccess/Failure messages.
+	sentRequestPending atomic.Bool
 
 	incomingRequests chan *Request
 
@@ -203,6 +222,10 @@ type channel struct {
 	// packetPool has a buffer for each extended channel ID to
 	// save allocations during writes.
 	packetPool map[uint32][]byte
+
+	// closeOnce guards close so it is idempotent: closing the internal Go
+	// channels (msg, incomingRequests) more than once would panic.
+	closeOnce sync.Once
 }
 
 // writePacket sends a packet. If the packet is a channel close, it updates
@@ -251,7 +274,7 @@ func (ch *channel) WriteExtended(data []byte, extendedCode uint32) (n int, err e
 	ch.writeMu.Unlock()
 
 	for len(data) > 0 {
-		space := min(ch.maxRemotePayload, len(data))
+		space := minPayloadSize(ch.maxRemotePayload, len(data))
 		if space, err = ch.remoteWin.reserve(space); err != nil {
 			return n, err
 		}
@@ -327,7 +350,18 @@ func (ch *channel) handleData(packet []byte) error {
 	if extended == 1 {
 		ch.extPending.write(data)
 	} else if extended > 0 {
-		// discard other extended data.
+		// RFC 4254, Section 5.2 defines no extended data types other
+		// than stderr (type 1, handled above) and this package provides
+		// no API to read them, so the data is discarded. Credit its
+		// window back immediately: it can never be read, so the
+		// deduction above would otherwise shrink the window permanently.
+		// adjustWindow returns io.EOF if the local side has already
+		// sent a channel close; ignore it like ReadExtended does, since
+		// an error returned here would terminate the mux read loop and
+		// tear down the whole connection.
+		if err := ch.adjustWindow(length); err != nil && err != io.EOF {
+			return err
+		}
 	} else {
 		ch.pending.write(data)
 	}
@@ -380,17 +414,19 @@ func (c *channel) ReadExtended(data []byte, extended uint32) (n int, err error)
 }
 
 func (c *channel) close() {
-	c.pending.eof()
-	c.extPending.eof()
-	close(c.msg)
-	close(c.incomingRequests)
-	c.writeMu.Lock()
-	// This is not necessary for a normal channel teardown, but if
-	// there was another error, it is.
-	c.sentClose = true
-	c.writeMu.Unlock()
-	// Unblock writers.
-	c.remoteWin.close()
+	c.closeOnce.Do(func() {
+		c.pending.eof()
+		c.extPending.eof()
+		close(c.msg)
+		close(c.incomingRequests)
+		c.writeMu.Lock()
+		// This is not necessary for a normal channel teardown, but if
+		// there was another error, it is.
+		c.sentClose = true
+		c.writeMu.Unlock()
+		// Unblock writers.
+		c.remoteWin.close()
+	})
 }
 
 // responseMessageReceived is called when a success or failure message is
@@ -404,10 +440,20 @@ func (ch *channel) responseMessageReceived() error {
 		return errors.New("ssh: duplicate response received for channel")
 	}
 	ch.decided = true
+	ch.established.Store(true)
 	return nil
 }
 
 func (ch *channel) handlePacket(packet []byte) error {
+	// Only the open response is expected before the channel is established.
+	if !ch.established.Load() {
+		switch packet[0] {
+		case msgChannelOpenConfirm, msgChannelOpenFailure:
+		default:
+			return nil
+		}
+	}
+
 	switch packet[0] {
 	case msgChannelData, msgChannelExtendedData:
 		return ch.handleData(packet)
@@ -460,27 +506,41 @@ func (ch *channel) handlePacket(packet []byte) error {
 		}
 
 		ch.incomingRequests <- &req
+	case *channelRequestSuccessMsg, *channelRequestFailureMsg:
+		// Drop responses that arrive when no SendRequest is waiting, to
+		// prevent a malicious peer from filling ch.msg and stalling the
+		// mux read loop. The non-blocking send additionally protects the
+		// loop if a well-behaved caller is slow to read.
+		if !ch.sentRequestPending.Load() {
+			return nil
+		}
+		select {
+		case ch.msg <- msg:
+		default:
+		}
 	default:
-		ch.msg <- msg
+		// No other message type is expected on an established channel.
+		return fmt.Errorf("ssh: unexpected message type %d on channel %d", packet[0], ch.localId)
 	}
 	return nil
 }
 
 func (m *mux) newChannel(chanType string, direction channelDirection, extraData []byte) *channel {
 	ch := &channel{
-		remoteWin:        window{Cond: newCond()},
-		myWindow:         channelWindowSize,
-		pending:          newBuffer(),
-		extPending:       newBuffer(),
-		direction:        direction,
-		incomingRequests: make(chan *Request, chanSize),
-		msg:              make(chan interface{}, chanSize),
-		chanType:         chanType,
-		extraData:        extraData,
-		mux:              m,
-		packetPool:       make(map[uint32][]byte),
+		remoteWin:          window{Cond: newCond()},
+		myWindow:           channelWindowSize,
+		maxIncomingPayload: channelMaxPacket,
+		pending:            newBuffer(),
+		extPending:         newBuffer(),
+		direction:          direction,
+		incomingRequests:   make(chan *Request, chanSize),
+		msg:                make(chan interface{}, chanSize),
+		chanType:           chanType,
+		extraData:          extraData,
+		mux:                m,
+		packetPool:         make(map[uint32][]byte),
 	}
-	ch.localId = m.chanList.add(ch)
+	m.chanList.add(ch)
 	return ch
 }
 
@@ -504,7 +564,6 @@ func (ch *channel) Accept() (Channel, <-chan *Request, error) {
 	if ch.decided {
 		return nil, nil, errDecidedAlready
 	}
-	ch.maxIncomingPayload = channelMaxPacket
 	confirm := channelOpenConfirmMsg{
 		PeersID:       ch.remoteId,
 		MyID:          ch.localId,
@@ -512,6 +571,7 @@ func (ch *channel) Accept() (Channel, <-chan *Request, error) {
 		MaxPacketSize: ch.maxIncomingPayload,
 	}
 	ch.decided = true
+	ch.established.Store(true)
 	if err := ch.sendMessage(confirm); err != nil {
 		return nil, nil, err
 	}
@@ -530,7 +590,17 @@ func (ch *channel) Reject(reason RejectionReason, message string) error {
 		Language: "en",
 	}
 	ch.decided = true
-	return ch.sendMessage(reject)
+	err := ch.sendMessage(reject)
+
+	// Remove the channel from the mux to prevent memory leaks.
+	// Do not call ch.close() here: no goroutine holds a reference to a
+	// rejected channel's internal channels (msg, incomingRequests), so
+	// removing it from chanList is sufficient for GC. Calling close()
+	// would race with the mux loop goroutine (handlePacket or dropAll),
+	// causing a panic from closing an already-closed channel.
+	ch.mux.chanList.remove(ch.localId)
+
+	return err
 }
 
 func (ch *channel) Read(data []byte) (int, error) {
@@ -586,6 +656,27 @@ func (ch *channel) SendRequest(name string, wantReply bool, payload []byte) (boo
 	if wantReply {
 		ch.sentRequestMu.Lock()
 		defer ch.sentRequestMu.Unlock()
+
+		// Open the gate so that responses arriving while this request is in
+		// flight are allowed to reach ch.msg. Responses arriving while no
+		// request is pending are dropped by handlePacket.
+		ch.sentRequestPending.Store(true)
+		defer ch.sentRequestPending.Store(false)
+
+		// Drain any spurious responses that may have been buffered. This
+		// prevents a previously buffered unexpected response from being
+		// consumed instead of the actual response for this request.
+	drain:
+		for {
+			select {
+			case _, ok := <-ch.msg:
+				if !ok {
+					break drain
+				}
+			default:
+				break drain
+			}
+		}
 	}
 
 	msg := channelRequestMsg{

ssh/channel_test.go

@@ -0,0 +1,250 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssh
+
+import (
+	"encoding/binary"
+	"io"
+	"math/bits"
+	"testing"
+	"time"
+	"unsafe"
+)
+
+func TestMinPayloadSize(t *testing.T) {
+	// 4 GiB (2^32). Declared as a var (not a const) so that int(bigPayload)
+	// is a runtime conversion: a constant conversion would fail to compile
+	// on 32-bit platforms with "constant 4294967296 overflows int". On
+	// 32-bit the value truncates to 0 at runtime, but the is64Bit cases
+	// that reference it are skipped by the runtime check below.
+	var bigPayload int64 = 1 << 32
+
+	tests := []struct {
+		name       string
+		maxPayload uint32
+		dataLen    int
+		want       uint32
+		is64Bit    bool // Flag to run only on 64-bit architectures
+	}{
+		{
+			name:       "Normal Case - Data fits in payload",
+			maxPayload: 32768,
+			dataLen:    1000,
+			want:       1000,
+		},
+		{
+			name:       "Normal Case - Data larger than payload",
+			maxPayload: 32768,
+			dataLen:    50000,
+			want:       32768,
+		},
+		{
+			name:       "Boundary Case - Data zero",
+			maxPayload: 32768,
+			dataLen:    0,
+			want:       0,
+		},
+		{
+			name:       "Overflow Case - Data is exactly 4GB (1<<32)",
+			maxPayload: 32768,
+			dataLen:    int(bigPayload),
+			want:       32768,
+			is64Bit:    true,
+		},
+		{
+			name:       "Overflow Case - Data is 4GB + small amount",
+			maxPayload: 32768,
+			dataLen:    int(bigPayload + 100),
+			want:       32768,
+			is64Bit:    true,
+		},
+	}
+
+	is64Bit := bits.UintSize == 64
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.is64Bit && !is64Bit {
+				t.Skip("Skipping test requiring 64-bit int")
+			}
+			got := minPayloadSize(tt.maxPayload, tt.dataLen)
+			if got != tt.want {
+				t.Errorf("minPayloadSize(%d, %d) = %d; want %d", tt.maxPayload, tt.dataLen, got, tt.want)
+			}
+		})
+	}
+}
+
+// TestWriteExtendedNoInfiniteLoopOnLargeWrite is an end-to-end regression
+// test for the integer-overflow bug in WriteExtended. Before the fix, a
+// write whose len(data) was a multiple of 2^32 caused minPayloadSize to
+// return 0; WriteExtended then spun forever, reserving 0 bytes per
+// iteration and never advancing the data slice.
+//
+// We exercise the real WriteExtended path with a slice whose declared
+// length is exactly 2^32. Allocating 4 GiB is unnecessary: each iteration
+// only reads up to maxRemotePayload bytes from the head of the slice, and
+// the loop blocks in remoteWin.reserve() once the channel window is
+// exhausted — before the slice base advances past the underlying buffer.
+//
+// With the fix, the loop blocks in reserve(); we detect that via
+// waitWriterBlocked(), then close the window to let WriteExtended return.
+// With the bug, the loop never blocks and the test times out.
+//
+//go:nocheckptr
+func TestWriteExtendedNoInfiniteLoopOnLargeWrite(t *testing.T) {
+	if bits.UintSize < 64 {
+		t.Skip("test requires 64-bit int to construct a slice with len >= 2^32")
+	}
+
+	reader, writer, mux := channelPair(t)
+	defer reader.Close()
+	defer writer.Close()
+	defer mux.Close()
+
+	// Sized to hold the full pre-update remote window so that no iteration
+	// reads past the backing buffer before reserve() blocks.
+	backing := make([]byte, channelWindowSize)
+	var bigLen int64 = 1 << 32
+	bigSlice := unsafe.Slice(&backing[0], int(bigLen))
+
+	done := make(chan int, 1)
+	go func() {
+		n, _ := writer.Write(bigSlice)
+		done <- n
+	}()
+
+	blocked := make(chan struct{})
+	go func() {
+		writer.remoteWin.waitWriterBlocked()
+		close(blocked)
+	}()
+
+	select {
+	case <-blocked:
+		// Good — the loop made progress and is now blocked in reserve().
+		// Close the window to let WriteExtended return.
+		writer.remoteWin.close()
+	case <-time.After(2 * time.Second):
+		t.Fatal("WriteExtended did not block in reserve within 2s — minPayloadSize likely returned 0 (integer overflow regression)")
+	}
+
+	select {
+	case n := <-done:
+		if n == 0 {
+			t.Fatalf("WriteExtended returned n=0; expected progress")
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("WriteExtended did not return after closing the window")
+	}
+}
+
+func TestDiscardedExtendedDataReturnsWindowCredit(t *testing.T) {
+	client, _, serverChans := forwardingPair(t)
+
+	clientCh, reqs, err := client.OpenChannel("test", nil)
+	if err != nil {
+		t.Fatalf("OpenChannel: %v", err)
+	}
+	go DiscardRequests(reqs)
+	defer clientCh.Close()
+
+	serverCh := (<-serverChans).(*channel)
+	defer serverCh.Close()
+
+	// Write more than the default channel receive window (2 MiB) of
+	// extended data with a type code other than stderr. The peer
+	// discards such data: if it did not return the window credit the
+	// write would block forever once the window is exhausted.
+	const payload = 4 * 1024 * 1024
+	done := make(chan error, 1)
+	go func() {
+		buf := make([]byte, 32*1024)
+		remaining := payload
+		for remaining > 0 {
+			n := min(len(buf), remaining)
+			nw, err := serverCh.WriteExtended(buf[:n], 2)
+			if err != nil {
+				done <- err
+				return
+			}
+			remaining -= nw
+		}
+		done <- nil
+	}()
+
+	select {
+	case err := <-done:
+		if err != nil {
+			t.Fatalf("write of discarded extended data: %v", err)
+		}
+	case <-time.After(10 * time.Second):
+		t.Fatal("write of discarded extended data blocked: window credit is not returned")
+	}
+
+	// The main stream must still be usable.
+	want := []byte("main stream after extended data")
+	if _, err := serverCh.Write(want); err != nil {
+		t.Fatalf("write to main stream: %v", err)
+	}
+	got := make([]byte, len(want))
+	if _, err := io.ReadFull(clientCh, got); err != nil {
+		t.Fatalf("read from main stream: %v", err)
+	}
+	if string(got) != string(want) {
+		t.Fatalf("read %q from main stream, want %q", got, want)
+	}
+
+	// Reading the main stream payload above orders the test after all
+	// preceding packets: everything received has now been either read or
+	// discarded, so the full window credit must have been accounted.
+	// Anything less indicates a partial-credit leak that the liveness
+	// check above would not detect.
+	cc := clientCh.(*channel)
+	cc.windowMu.Lock()
+	window := cc.myWindow + cc.myConsumed
+	cc.windowMu.Unlock()
+	if window != channelWindowSize {
+		t.Errorf("myWindow+myConsumed = %d, want %d", window, channelWindowSize)
+	}
+}
+
+func TestDiscardedExtendedDataAfterClose(t *testing.T) {
+	client, _, serverChans := forwardingPair(t)
+
+	clientCh, reqs, err := client.OpenChannel("test", nil)
+	if err != nil {
+		t.Fatalf("OpenChannel: %v", err)
+	}
+	go DiscardRequests(reqs)
+	serverCh := <-serverChans
+	defer serverCh.Close()
+
+	ch := clientCh.(*channel)
+	// Close the channel locally: sentClose is now set, but the channel
+	// stays in the mux chanList until the peer's close arrives, so
+	// in-flight data packets are still dispatched to handleData.
+	if err := ch.Close(); err != nil {
+		t.Fatalf("Close: %v", err)
+	}
+
+	// Deliver extended data packets with an unknown type code, enough to
+	// cross the adjustWindow send threshold of 3*maxIncomingPayload.
+	// The window adjust message cannot be sent after the close and
+	// adjustWindow fails with io.EOF: handleData must swallow that
+	// error, since any error it returns terminates the mux read loop
+	// and tears down every channel on the connection.
+	const packetLen = 32 * 1024
+	packet := make([]byte, 13+packetLen)
+	packet[0] = msgChannelExtendedData
+	binary.BigEndian.PutUint32(packet[1:], ch.localId)
+	binary.BigEndian.PutUint32(packet[5:], 2)
+	binary.BigEndian.PutUint32(packet[9:], packetLen)
+	for range 5 {
+		if err := ch.handleData(packet); err != nil {
+			t.Fatalf("handleData after local close: %v", err)
+		}
+	}
+}

ssh/cipher.go

@@ -129,6 +129,10 @@ func init() {
 	// You should expect that an active attacker can recover plaintext if
 	// you do.
 	cipherModes[InsecureCipherAES128CBC] = &cipherMode{16, aes.BlockSize, newAESCBCCipher}
+	// AES-192 and AES-256 reuse the same CBC packet cipher; aes.NewCipher
+	// selects the key schedule from the key length.
+	cipherModes[InsecureCipherAES192CBC] = &cipherMode{24, aes.BlockSize, newAESCBCCipher}
+	cipherModes[InsecureCipherAES256CBC] = &cipherMode{32, aes.BlockSize, newAESCBCCipher}
 	cipherModes[InsecureCipherTripleDESCBC] = &cipherMode{24, des.BlockSize, newTripleDESCBCCipher}
 }
 
@@ -407,7 +411,7 @@ func (c *gcmCipher) readCipherPacket(seqNum uint32, r io.Reader) ([]byte, error)
 		return nil, fmt.Errorf("ssh: illegal padding %d", padding)
 	}
 
-	if int(padding+1) >= len(plain) {
+	if int(padding)+1 >= len(plain) {
 		return nil, fmt.Errorf("ssh: padding %d too large", padding)
 	}
 	plain = plain[1 : length-uint32(padding)]
@@ -586,7 +590,7 @@ func (c *cbcCipher) writeCipherPacket(seqNum uint32, w io.Writer, rand io.Reader
 
 	// Length of encrypted portion of the packet (header, payload, padding).
 	// Enforce minimum padding and packet size.
-	encLength := maxUInt32(prefixLen+len(packet)+cbcMinPaddingSize, cbcMinPaddingSize)
+	encLength := maxUInt32(prefixLen+len(packet)+cbcMinPaddingSize, cbcMinPacketSize)
 	// Enforce block size.
 	encLength = (encLength + effectiveBlockSize - 1) / effectiveBlockSize * effectiveBlockSize
 

ssh/client.go

@@ -88,6 +88,32 @@ func NewClientConn(c net.Conn, addr string, config *ClientConfig) (Conn, <-chan
 	return conn, conn.mux.incomingChannels, conn.mux.incomingRequests, nil
 }
 
+// NewControlClientConn establishes an SSH connection over an OpenSSH
+// ControlMaster socket c in proxy mode.
+//
+// Note that this package only implements the client side of the multiplexing
+// protocol. The provided net.Conn must be a local, secure connection (such as a
+// Unix domain socket) connected to an already-running OpenSSH process acting as
+// the ControlMaster.
+//
+// WARNING: Because proxy mode bypasses the standard cryptographic handshake
+// passing a standard network connection (e.g., TCP) will result in plaintext
+// data leakage.
+//
+// The Request and NewChannel channels must be serviced or the connection
+// will hang.
+func NewControlClientConn(c net.Conn) (Conn, <-chan NewChannel, <-chan *Request, error) {
+	conn := &connection{
+		sshConn: sshConn{conn: c},
+	}
+	var err error
+	if conn.transport, err = handshakeControlProxy(c); err != nil {
+		return nil, nil, nil, fmt.Errorf("ssh: control proxy handshake failed: %w", err)
+	}
+	conn.mux = newMux(conn.transport)
+	return conn, conn.mux.incomingChannels, conn.mux.incomingRequests, nil
+}
+
 // clientHandshake performs the client side key exchange. See RFC 4253 Section
 // 7.
 func (c *connection) clientHandshake(dialAddress string, config *ClientConfig) error {
@@ -197,6 +223,59 @@ type HostKeyCallback func(hostname string, remote net.Addr, key PublicKey) error
 // the server. A BannerCallback receives the message sent by the remote server.
 type BannerCallback func(message string) error
 
+// ClientAuthContext contains information about the current state of the
+// authentication process, passed to [ClientAuthCallback].
+type ClientAuthContext struct {
+	// Metadata contains the connection metadata.
+	Metadata ConnMetadata
+
+	// Algorithms contains the negotiated algorithms.
+	Algorithms NegotiatedAlgorithms
+
+	// AllowedMethods lists the authentication methods currently accepted
+	// by the server. These are the protocol-level names defined in RFC 4252
+	// such as "publickey", "password".
+	AllowedMethods []string
+
+	// PartialSuccessMethods lists the authentication methods that have already
+	// succeeded, indicating a multi-step authentication flow. This list
+	// represents the exact sequence of partial successes and may contain
+	// duplicates if the same method succeeded multiple times.
+	PartialSuccessMethods []string
+
+	// TriedMethods lists the methods that have already been attempted and
+	// failed during this session. This list represents the exact sequence of
+	// failures and may contain duplicates. This allows the callback to also
+	// track the number of failed attempts for a specific method.
+	TriedMethods []string
+}
+
+// ClientAuthCallback is a hook invoked before each authentication attempt. It
+// allows the client to dynamically select an authentication method based on the
+// current context, server capabilities, or previous failures.
+//
+// The callback is invoked after the initial "none" authentication method, once
+// the server's supported authentication methods are known.
+//
+// Return values:
+//   - (AuthMethod, nil): The client will attempt this specific method next.
+//     The returned method does NOT need to be present in [ClientConfig.Auth].
+//     This allows for dynamic authentication strategies (e.g., prompting
+//     for a password only if public key auth fails). Callers should inspect
+//     [ClientAuthContext.TriedMethods] to avoid repeatedly returning the
+//     same failing method.
+//   - (nil, nil): The client selects from [ClientConfig.Auth] the first
+//     instance of a method that has not been tried yet, or aborts if none
+//     are left. If authentication is not successful, the callback is invoked
+//     again before the following attempt.
+//   - (nil, error): The authentication process is aborted immediately,
+//     causing the ongoing SSH handshake to fail with the provided error.
+//
+// To bound resource use, the client caps the total number of authentication
+// attempts (failures and partial successes combined) at 64. If the cap is
+// exceeded the handshake aborts with an error.
+type ClientAuthCallback func(ctx *ClientAuthContext) (AuthMethod, error)
+
 // A ClientConfig structure is used to configure a Client. It must not be
 // modified after having been passed to an SSH function.
 type ClientConfig struct {
@@ -210,6 +289,9 @@ type ClientConfig struct {
 	// Auth contains possible authentication methods to use with the
 	// server. Only the first instance of a particular RFC 4252 method will
 	// be used during authentication.
+	//
+	// If AuthCallback is set, these AuthMethod are only used if the
+	// callback returns nil.
 	Auth []AuthMethod
 
 	// HostKeyCallback is called during the cryptographic
@@ -240,6 +322,9 @@ type ClientConfig struct {
 	//
 	// A Timeout of zero means no timeout.
 	Timeout time.Duration
+
+	// AuthCallback, if non-nil, is invoked before each authentication attempt.
+	AuthCallback ClientAuthCallback
 }
 
 // InsecureIgnoreHostKey returns a function that can be used for

ssh/client_auth.go

@@ -21,6 +21,12 @@ const (
 	authSuccess
 )
 
+// maxAuthClientTried bounds the total number of authentication attempts
+// (failures and partial successes combined) the client makes before
+// aborting the loop, to prevent unbounded growth when an AuthCallback
+// keeps supplying methods.
+const maxAuthClientTried = 64
+
 // clientAuthenticate authenticates with the remote server. See RFC 4252.
 func (c *connection) clientAuthenticate(config *ClientConfig) error {
 	// initiate user auth session
@@ -67,32 +73,62 @@ func (c *connection) clientAuthenticate(config *ClientConfig) error {
 	// then any untried methods suggested by the server.
 	var tried []string
 	var lastMethods []string
+	var partialSuccess []string
 
 	sessionID := c.transport.getSessionID()
 	for auth := AuthMethod(new(noneAuth)); auth != nil; {
 		ok, methods, err := auth.auth(sessionID, config.User, c.transport, config.Rand, extensions)
 		if err != nil {
 			// On disconnect, return error immediately
-			if _, ok := err.(*disconnectMsg); ok {
+			if _, isDisconnect := err.(*disconnectMsg); isDisconnect {
 				return err
 			}
-			// We return the error later if there is no other method left to
-			// try.
+			// We return the error later if there is no other method
+			// left to try.
 			ok = authFailure
 		}
-		if ok == authSuccess {
-			// success
+
+		switch ok {
+		case authSuccess:
 			return nil
-		} else if ok == authFailure {
-			if m := auth.method(); !slices.Contains(tried, m) {
-				tried = append(tried, m)
-			}
+		case authPartialSuccess:
+			partialSuccess = append(partialSuccess, auth.method())
+		case authFailure:
+			tried = append(tried, auth.method())
 		}
+		if len(partialSuccess)+len(tried) > maxAuthClientTried {
+			return fmt.Errorf("ssh: too many authentication attempts (%d), aborting",
+				len(partialSuccess)+len(tried))
+		}
+
 		if methods == nil {
 			methods = lastMethods
 		}
 		lastMethods = methods
 
+		// If AuthCallback is set it takes precedence: it picks the next
+		// AuthMethod dynamically. The returned method need not be in
+		// config.Auth. If the callback returns (nil, nil) we fall back to
+		// selecting the next untried method from config.Auth below; on
+		// (nil, error) the handshake aborts.
+		if config.AuthCallback != nil {
+			ctx := &ClientAuthContext{
+				Metadata:              c,
+				Algorithms:            c.Algorithms(),
+				AllowedMethods:        slices.Clone(methods),
+				PartialSuccessMethods: slices.Clone(partialSuccess),
+				TriedMethods:          slices.Clone(tried),
+			}
+			altAuth, cbErr := config.AuthCallback(ctx)
+			if cbErr != nil {
+				return cbErr
+			}
+			if altAuth != nil {
+				auth = altAuth
+				continue
+			}
+		}
+
 		auth = nil
 
 	findNext:
@@ -274,10 +310,14 @@ func pickSignatureAlgorithm(signer Signer, extensions map[string][]byte) (MultiA
 	}
 
 	// Filter algorithms based on those supported by MultiAlgorithmSigner.
+	// Iterate over the signer's algorithms first to preserve its preference order.
+	supportedKeyAlgos := algorithmsForKeyFormat(keyFormat)
 	var keyAlgos []string
-	for _, algo := range algorithmsForKeyFormat(keyFormat) {
-		if slices.Contains(as.Algorithms(), underlyingAlgo(algo)) {
-			keyAlgos = append(keyAlgos, algo)
+	for _, signerAlgo := range as.Algorithms() {
+		if idx := slices.IndexFunc(supportedKeyAlgos, func(algo string) bool {
+			return underlyingAlgo(algo) == signerAlgo
+		}); idx >= 0 {
+			keyAlgos = append(keyAlgos, supportedKeyAlgos[idx])
 		}
 	}
 
@@ -373,11 +413,11 @@ func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand
 			return authFailure, nil, err
 		}
 
-		// If authentication succeeds or the list of available methods does not
-		// contain the "publickey" method, do not attempt to authenticate with any
-		// other keys.  According to RFC 4252 Section 7, the latter can occur when
-		// additional authentication methods are required.
-		if success == authSuccess || !slices.Contains(methods, cb.method()) {
+		// If authentication succeeds or partially succeeds, return immediately
+		// so the caller can select the next auth method. According to RFC 4252
+		// Section 7, if the server no longer lists "publickey" among its
+		// allowed methods, do not attempt to authenticate with any other keys.
+		if success == authSuccess || success == authPartialSuccess || !slices.Contains(methods, cb.method()) {
 			return success, methods, err
 		}
 	}
@@ -758,7 +798,7 @@ func (g *gssAPIWithMICCallback) auth(session []byte, user string, c packetConn,
 			return authFailure, nil, fmt.Errorf("GSS-API Error:\n"+
 				"Major Status: %d\n"+
 				"Minor Status: %d\n"+
-				"Error Message: %s\n", userAuthGSSAPIErrorResp.MajorStatus, userAuthGSSAPIErrorResp.MinorStatus,
+				"Error Message: %q\n", userAuthGSSAPIErrorResp.MajorStatus, userAuthGSSAPIErrorResp.MinorStatus,
 				userAuthGSSAPIErrorResp.Message)
 		case msgUserAuthGSSAPIToken:
 			userAuthGSSAPITokenReq := &userAuthGSSAPIToken{}

ssh/client_auth_test.go

@@ -7,10 +7,12 @@ package ssh
 import (
 	"bytes"
 	"crypto/rand"
+	"crypto/rsa"
 	"errors"
 	"fmt"
 	"io"
 	"log"
+	"math/big"
 	"net"
 	"os"
 	"runtime"
@@ -169,6 +171,723 @@ func TestClientAuthThirdKey(t *testing.T) {
 	}
 }
 
+// invalidRSASigner offers an RSA public key the server cannot parse: its public
+// exponent is even, which parseRSA rejects regardless of any key size limit.
+// The key is intentionally invalid for a structural reason rather than for its
+// size, so the test stays meaningful even if the accepted modulus size changes.
+// Its Sign method is never reached, because the key is rejected during the
+// initial public key query.
+type invalidRSASigner struct{}
+
+func (invalidRSASigner) PublicKey() PublicKey {
+	n := new(big.Int).Lsh(big.NewInt(1), 2048)
+	pub, err := NewPublicKey(&rsa.PublicKey{N: n, E: 2}) // incorrect exponent.
+	if err != nil {
+		panic(err)
+	}
+	return pub
+}
+
+func (invalidRSASigner) Sign(rand io.Reader, data []byte) (*Signature, error) {
+	return nil, errors.New("ssh: invalid test key must not be used to sign")
+}
+
+func TestClientAuthInvalidPublicKey(t *testing.T) {
+	config := &ClientConfig{
+		User: "testuser",
+		Auth: []AuthMethod{
+			PublicKeys(invalidRSASigner{}, testSigners["rsa"]),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+	if err := tryAuth(t, config); err != nil {
+		t.Fatalf("client auth failed but should have fallen back to a valid key: %s", err)
+	}
+}
+
+// partialSuccessPublicKeyAndKbdInteractiveServer returns a server config
+// where the rsa key gets partial success and the server offers both publickey
+// and keyboard-interactive as next methods. The VerifiedPublicKeyCallback
+// tracks state so that the same key only triggers partial success once,
+// avoiding an impossible auth loop.
+func partialSuccessPublicKeyAndKbdInteractiveServer() *ServerConfig {
+	rsaDone := false
+	serverConf := &ServerConfig{
+		PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+			if bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+				return nil, nil
+			}
+			return nil, errors.New("invalid credentials")
+		},
+		VerifiedPublicKeyCallback: func(conn ConnMetadata, key PublicKey, permissions *Permissions, signatureAlgorithm string) (*Permissions, error) {
+			if !rsaDone && bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+				rsaDone = true
+				return nil, &PartialSuccessError{
+					Next: ServerAuthCallbacks{
+						PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+							if bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+								return nil, nil
+							}
+							return nil, errors.New("invalid credentials")
+						},
+						KeyboardInteractiveCallback: func(conn ConnMetadata, client KeyboardInteractiveChallenge) (*Permissions, error) {
+							answers, err := client("", "", []string{"token: "}, []bool{true})
+							if err != nil {
+								return nil, err
+							}
+							if len(answers) == 1 && answers[0] == "correct-token" {
+								return nil, nil
+							}
+							return nil, errors.New("invalid token")
+						},
+					},
+				}
+			}
+			return nil, errors.New("invalid credentials")
+		},
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+	return serverConf
+}
+
+// partialSuccessMultiKeyServer returns a server config that requires two
+// public keys in sequence: the first key (rsa) triggers partial success
+// requiring a second key (ecdsa) to complete authentication.
+func partialSuccessMultiKeyServer() *ServerConfig {
+	firstKeyDone := false
+	serverConf := &ServerConfig{
+		PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+			if bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+				return nil, nil
+			}
+			if bytes.Equal(key.Marshal(), testPublicKeys["ecdsa"].Marshal()) {
+				return nil, nil
+			}
+			return nil, errors.New("invalid credentials")
+		},
+		VerifiedPublicKeyCallback: func(conn ConnMetadata, key PublicKey, permissions *Permissions, signatureAlgorithm string) (*Permissions, error) {
+			if !firstKeyDone && bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+				firstKeyDone = true
+				return nil, &PartialSuccessError{
+					Next: ServerAuthCallbacks{
+						PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+							if bytes.Equal(key.Marshal(), testPublicKeys["ecdsa"].Marshal()) {
+								return nil, nil
+							}
+							return nil, errors.New("invalid credentials")
+						},
+					},
+				}
+			}
+			if firstKeyDone && bytes.Equal(key.Marshal(), testPublicKeys["ecdsa"].Marshal()) {
+				return nil, nil
+			}
+			return nil, errors.New("invalid credentials")
+		},
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+	return serverConf
+}
+
+func TestStaticMultiKeyPartialSuccess(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	clientConf := &ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"], testSigners["ecdsa"]),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	go NewServerConn(c1, partialSuccessMultiKeyServer())
+
+	_, _, _, err = NewClientConn(c2, "", clientConf)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+}
+
+func TestStaticPartialSuccess(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	clientConf := &ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+			KeyboardInteractive(func(name, instruction string, questions []string, echos []bool) ([]string, error) {
+				return []string{"correct-token"}, nil
+			}),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	go NewServerConn(c1, partialSuccessPublicKeyAndKbdInteractiveServer())
+
+	_, _, _, err = NewClientConn(c2, "", clientConf)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+}
+
+// partialSuccessKeyAThenKeyBServer returns a server config where keyA (rsa)
+// gets partial success and the server offers BOTH publickey and
+// keyboard-interactive. keyB (ecdsa) then completes auth successfully.
+func partialSuccessKeyAThenKeyBServer() *ServerConfig {
+	keyADone := false
+	serverConf := &ServerConfig{
+		PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+			if bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+				return nil, nil
+			}
+			if bytes.Equal(key.Marshal(), testPublicKeys["ecdsa"].Marshal()) {
+				return nil, nil
+			}
+			return nil, errors.New("invalid credentials")
+		},
+		VerifiedPublicKeyCallback: func(conn ConnMetadata, key PublicKey, permissions *Permissions, signatureAlgorithm string) (*Permissions, error) {
+			if !keyADone && bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+				keyADone = true
+				return nil, &PartialSuccessError{
+					Next: ServerAuthCallbacks{
+						PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+							if bytes.Equal(key.Marshal(), testPublicKeys["ecdsa"].Marshal()) {
+								return nil, nil
+							}
+							return nil, errors.New("invalid credentials")
+						},
+						KeyboardInteractiveCallback: func(conn ConnMetadata, client KeyboardInteractiveChallenge) (*Permissions, error) {
+							answers, err := client("", "", []string{"token: "}, []bool{true})
+							if err != nil {
+								return nil, err
+							}
+							if len(answers) == 1 && answers[0] == "correct-token" {
+								return nil, nil
+							}
+							return nil, errors.New("invalid token")
+						},
+					},
+				}
+			}
+			if keyADone && bytes.Equal(key.Marshal(), testPublicKeys["ecdsa"].Marshal()) {
+				return nil, nil
+			}
+			return nil, errors.New("invalid credentials")
+		},
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+	return serverConf
+}
+
+func TestStaticPartialSuccessKeyAThenKeyB(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	clientConf := &ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"], testSigners["ecdsa"]),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	go NewServerConn(c1, partialSuccessKeyAThenKeyBServer())
+
+	_, _, _, err = NewClientConn(c2, "", clientConf)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+}
+
+// partialSuccessMultiKeyThenKbdInteractiveServer returns a server config
+// that strictly requires keyA (rsa) AND keyB (ecdsa) as public keys before
+// allowing keyboard-interactive. After keyA, ONLY publickey is offered
+// (for keyB). After keyB, ONLY keyboard-interactive is offered.
+func partialSuccessMultiKeyThenKbdInteractiveServer() *ServerConfig {
+	serverConf := &ServerConfig{
+		PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+			if bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+				return nil, &PartialSuccessError{
+					Next: ServerAuthCallbacks{
+						PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+							if bytes.Equal(key.Marshal(), testPublicKeys["ecdsa"].Marshal()) {
+								return nil, &PartialSuccessError{
+									Next: ServerAuthCallbacks{
+										KeyboardInteractiveCallback: func(conn ConnMetadata, client KeyboardInteractiveChallenge) (*Permissions, error) {
+											answers, err := client("", "", []string{"token: "}, []bool{true})
+											if err != nil {
+												return nil, err
+											}
+											if len(answers) == 1 && answers[0] == "correct-token" {
+												return nil, nil
+											}
+											return nil, errors.New("invalid token")
+										},
+									},
+								}
+							}
+							return nil, errors.New("invalid credentials")
+						},
+					},
+				}
+			}
+			return nil, errors.New("invalid credentials")
+		},
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+	return serverConf
+}
+
+func TestStaticMultiKeyPartialThenKbdInteractive(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	clientConf := &ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"], testSigners["ecdsa"]),
+			KeyboardInteractive(func(name, instruction string, questions []string, echos []bool) ([]string, error) {
+				return []string{"correct-token"}, nil
+			}),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	go NewServerConn(c1, partialSuccessMultiKeyThenKbdInteractiveServer())
+
+	_, _, _, err = NewClientConn(c2, "", clientConf)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+}
+
+func TestAuthMethodDynamic(t *testing.T) {
+	config := &ClientConfig{
+		User:            "testuser",
+		Auth:            nil,
+		HostKeyCallback: InsecureIgnoreHostKey(),
+		AuthCallback: func(ctx *ClientAuthContext) (AuthMethod, error) {
+			if len(ctx.Metadata.SessionID()) == 0 {
+				t.Error("empty sessionID")
+			}
+			if ctx.Algorithms.HostKey == "" {
+				t.Error("empty Host Key")
+			}
+			if slices.Contains(ctx.AllowedMethods, "password") {
+				return Password(clientPassword), nil
+			}
+			return nil, errors.New("auth callback error")
+		},
+	}
+
+	if err := tryAuth(t, config); err != nil {
+		t.Fatalf("unable to dial remote side: %s", err)
+	}
+}
+
+func TestAuthCallbackError(t *testing.T) {
+	config := &ClientConfig{
+		User: "testuser",
+		Auth: []AuthMethod{
+			Password(clientPassword),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+		AuthCallback: func(ctx *ClientAuthContext) (AuthMethod, error) {
+			return nil, errors.New("auth callback error")
+		},
+	}
+
+	if err := tryAuth(t, config); err == nil {
+		t.Fatal("authentication unexpectedly succeeded after AuthCallback returned an error")
+	}
+}
+
+func TestAuthCallbackPartialSuccess(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	clientConf := &ClientConfig{
+		User:            "user",
+		HostKeyCallback: InsecureIgnoreHostKey(),
+		AuthCallback: func(ctx *ClientAuthContext) (AuthMethod, error) {
+			if slices.Contains(ctx.AllowedMethods, "publickey") && !slices.Contains(ctx.PartialSuccessMethods, "publickey") {
+				return PublicKeys(testSigners["rsa"]), nil
+			}
+			if slices.Contains(ctx.PartialSuccessMethods, "publickey") && slices.Contains(ctx.AllowedMethods, "keyboard-interactive") {
+				return KeyboardInteractive(func(name, instruction string, questions []string, echos []bool) ([]string, error) {
+					return []string{"correct-token"}, nil
+				}), nil
+			}
+			return nil, fmt.Errorf("unexpected auth state: allowed=%v partial=%v", ctx.AllowedMethods, ctx.PartialSuccessMethods)
+		},
+	}
+
+	go NewServerConn(c1, partialSuccessPublicKeyAndKbdInteractiveServer())
+
+	_, _, _, err = NewClientConn(c2, "", clientConf)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+}
+
+func TestAuthCallbackMultiKeyPartialSuccess(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	clientConf := &ClientConfig{
+		User:            "user",
+		HostKeyCallback: InsecureIgnoreHostKey(),
+		AuthCallback: func(ctx *ClientAuthContext) (AuthMethod, error) {
+			if slices.Contains(ctx.AllowedMethods, "publickey") && !slices.Contains(ctx.PartialSuccessMethods, "publickey") {
+				return PublicKeys(testSigners["rsa"]), nil
+			}
+			if slices.Contains(ctx.PartialSuccessMethods, "publickey") && slices.Contains(ctx.AllowedMethods, "publickey") {
+				return PublicKeys(testSigners["ecdsa"]), nil
+			}
+			return nil, fmt.Errorf("unexpected auth state: allowed=%v partial=%v", ctx.AllowedMethods, ctx.PartialSuccessMethods)
+		},
+	}
+
+	go NewServerConn(c1, partialSuccessMultiKeyServer())
+
+	_, _, _, err = NewClientConn(c2, "", clientConf)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+}
+
+func TestAuthCallbackMultiKeyPartialThenKbdInteractive(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	clientConf := &ClientConfig{
+		User:            "user",
+		HostKeyCallback: InsecureIgnoreHostKey(),
+		AuthCallback: func(ctx *ClientAuthContext) (AuthMethod, error) {
+			partialCount := len(ctx.PartialSuccessMethods)
+			if partialCount == 0 && slices.Contains(ctx.AllowedMethods, "publickey") {
+				return PublicKeys(testSigners["rsa"]), nil
+			}
+			if partialCount == 1 && slices.Contains(ctx.AllowedMethods, "publickey") {
+				return PublicKeys(testSigners["ecdsa"]), nil
+			}
+			if partialCount >= 2 && slices.Contains(ctx.AllowedMethods, "keyboard-interactive") {
+				return KeyboardInteractive(func(name, instruction string, questions []string, echos []bool) ([]string, error) {
+					return []string{"correct-token"}, nil
+				}), nil
+			}
+			return nil, fmt.Errorf("unexpected auth state: allowed=%v partial=%v tried=%v",
+				ctx.AllowedMethods, ctx.PartialSuccessMethods, ctx.TriedMethods)
+		},
+	}
+
+	go NewServerConn(c1, partialSuccessMultiKeyThenKbdInteractiveServer())
+
+	_, _, _, err = NewClientConn(c2, "", clientConf)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+}
+
+func TestAuthCallbackPartialSuccessKeyAThenKeyB(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	clientConf := &ClientConfig{
+		User:            "user",
+		HostKeyCallback: InsecureIgnoreHostKey(),
+		AuthCallback: func(ctx *ClientAuthContext) (AuthMethod, error) {
+			if len(ctx.PartialSuccessMethods) == 0 && slices.Contains(ctx.AllowedMethods, "publickey") {
+				return PublicKeys(testSigners["rsa"]), nil
+			}
+			if len(ctx.PartialSuccessMethods) == 1 && slices.Contains(ctx.AllowedMethods, "publickey") {
+				return PublicKeys(testSigners["ecdsa"]), nil
+			}
+			return nil, fmt.Errorf("unexpected auth state: allowed=%v partial=%v",
+				ctx.AllowedMethods, ctx.PartialSuccessMethods)
+		},
+	}
+
+	go NewServerConn(c1, partialSuccessKeyAThenKeyBServer())
+
+	_, _, _, err = NewClientConn(c2, "", clientConf)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+}
+
+func TestAuthCallbackPartialSuccessWithStaticAuth(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	clientConf := &ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+		AuthCallback: func(ctx *ClientAuthContext) (AuthMethod, error) {
+			if slices.Contains(ctx.PartialSuccessMethods, "publickey") && slices.Contains(ctx.AllowedMethods, "keyboard-interactive") {
+				return KeyboardInteractive(func(name, instruction string, questions []string, echos []bool) ([]string, error) {
+					return []string{"correct-token"}, nil
+				}), nil
+			}
+			return nil, nil
+		},
+	}
+
+	go NewServerConn(c1, partialSuccessPublicKeyAndKbdInteractiveServer())
+
+	_, _, _, err = NewClientConn(c2, "", clientConf)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+}
+
+func partialSuccessPubKeyForbiddenAfterPartialServer(maxTries int) *ServerConfig {
+	serverConf := &ServerConfig{
+		PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+			if bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+				return nil, nil
+			}
+			return nil, errors.New("invalid credentials")
+		},
+		VerifiedPublicKeyCallback: func(conn ConnMetadata, key PublicKey, permissions *Permissions, signatureAlgorithm string) (*Permissions, error) {
+			if bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+				return nil, &PartialSuccessError{
+					Next: ServerAuthCallbacks{
+						PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+							return nil, errors.New("legacy public key authentication is forbidden")
+						},
+						KeyboardInteractiveCallback: func(conn ConnMetadata, client KeyboardInteractiveChallenge) (*Permissions, error) {
+							answers, err := client("", "", []string{"token: "}, []bool{true})
+							if err != nil {
+								return nil, err
+							}
+							if len(answers) == 1 && answers[0] == "correct-token" {
+								return nil, nil
+							}
+							return nil, errors.New("invalid token")
+						},
+					},
+				}
+			}
+			return nil, errors.New("invalid credentials")
+		},
+		MaxAuthTries: maxTries,
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+	return serverConf
+}
+
+func TestAuthCallbackPartialSuccessWithStaticMultiKey(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	clientConf := &ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			PublicKeys(
+				testSigners["rsa"],
+				testSigners["ecdsa"],
+				testSigners["ed25519"],
+			),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+		AuthCallback: func(ctx *ClientAuthContext) (AuthMethod, error) {
+			if slices.Contains(ctx.PartialSuccessMethods, "publickey") && slices.Contains(ctx.AllowedMethods, "keyboard-interactive") {
+				return KeyboardInteractive(func(name, instruction string, questions []string, echos []bool) ([]string, error) {
+					return []string{"correct-token"}, nil
+				}), nil
+			}
+			return nil, nil
+		},
+	}
+
+	go NewServerConn(c1, partialSuccessPubKeyForbiddenAfterPartialServer(2))
+
+	_, _, _, err = NewClientConn(c2, "", clientConf)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+}
+
+func TestAuthCallbackPartialSuccessShortCircuit(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	serverConf := partialSuccessPubKeyForbiddenAfterPartialServer(2)
+
+	pubkeyAttempts := 0
+	clientConf := &ClientConfig{
+		User:            "user",
+		HostKeyCallback: InsecureIgnoreHostKey(),
+		AuthCallback: func(ctx *ClientAuthContext) (AuthMethod, error) {
+			if slices.Contains(ctx.AllowedMethods, "publickey") && !slices.Contains(ctx.PartialSuccessMethods, "publickey") {
+				pubkeyAttempts++
+				return PublicKeys(testSigners["rsa"], testSigners["ecdsa"], testSigners["ed25519"]), nil
+			}
+			if slices.Contains(ctx.PartialSuccessMethods, "publickey") && slices.Contains(ctx.AllowedMethods, "keyboard-interactive") {
+				return KeyboardInteractive(func(name, instruction string, questions []string, echos []bool) ([]string, error) {
+					return []string{"correct-token"}, nil
+				}), nil
+			}
+			return nil, fmt.Errorf("unexpected auth state: allowed=%v partial=%v tried=%v",
+				ctx.AllowedMethods, ctx.PartialSuccessMethods, ctx.TriedMethods)
+		},
+	}
+
+	go NewServerConn(c1, serverConf)
+
+	_, _, _, err = NewClientConn(c2, "", clientConf)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+	if pubkeyAttempts != 1 {
+		t.Errorf("expected publickey to be attempted once before short-circuit, got %d", pubkeyAttempts)
+	}
+}
+
+func TestAuthCallbackTriedLoopBound(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	serverConf := &ServerConfig{
+		MaxAuthTries: -1,
+		PasswordCallback: func(conn ConnMetadata, pass []byte) (*Permissions, error) {
+			return nil, errors.New("password rejected")
+		},
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+
+	invocations := 0
+	clientConf := &ClientConfig{
+		User:            "user",
+		HostKeyCallback: InsecureIgnoreHostKey(),
+		AuthCallback: func(ctx *ClientAuthContext) (AuthMethod, error) {
+			invocations++
+			return Password("wrong"), nil
+		},
+	}
+
+	go NewServerConn(c1, serverConf)
+
+	_, _, _, err = NewClientConn(c2, "", clientConf)
+	if err == nil {
+		t.Fatal("expected the client to abort after exceeding the attempts cap")
+	}
+	if !strings.Contains(err.Error(), "too many authentication attempts") {
+		t.Errorf("unexpected error: %v", err)
+	}
+	if invocations != maxAuthClientTried {
+		t.Errorf("AuthCallback invoked %d times; expected %d",
+			invocations, maxAuthClientTried)
+	}
+}
+
+func alwaysPartialPubKeyServer() *ServerConfig {
+	var alwaysPartial func(ConnMetadata, PublicKey) (*Permissions, error)
+	alwaysPartial = func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+		if !bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+			return nil, errors.New("invalid credentials")
+		}
+		return nil, &PartialSuccessError{
+			Next: ServerAuthCallbacks{
+				PublicKeyCallback: alwaysPartial,
+			},
+		}
+	}
+	serverConf := &ServerConfig{
+		MaxAuthTries:      -1,
+		PublicKeyCallback: alwaysPartial,
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+	return serverConf
+}
+
+func TestAuthCallbackPartialSuccessLoopBound(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	invocations := 0
+	clientConf := &ClientConfig{
+		User:            "user",
+		HostKeyCallback: InsecureIgnoreHostKey(),
+		AuthCallback: func(ctx *ClientAuthContext) (AuthMethod, error) {
+			invocations++
+			return PublicKeys(testSigners["rsa"]), nil
+		},
+	}
+
+	go NewServerConn(c1, alwaysPartialPubKeyServer())
+
+	_, _, _, err = NewClientConn(c2, "", clientConf)
+	if err == nil {
+		t.Fatal("expected the client to abort after exceeding the attempts cap")
+	}
+	if !strings.Contains(err.Error(), "too many authentication attempts") {
+		t.Errorf("unexpected error: %v", err)
+	}
+	if invocations != maxAuthClientTried {
+		t.Errorf("AuthCallback invoked %d times; expected %d",
+			invocations, maxAuthClientTried)
+	}
+}
+
 func TestAuthMethodPassword(t *testing.T) {
 	config := &ClientConfig{
 		User: "testuser",
@@ -971,6 +1690,74 @@ func TestAuthMethodGSSAPIWithMIC(t *testing.T) {
 	}
 }
 
+type maliciousGSSAPIWithMICAuthMethod struct{}
+
+func (maliciousGSSAPIWithMICAuthMethod) method() string {
+	// Reuse an advertised auth method name so the client attempts this
+	// AuthMethod even when gssapi-with-mic is not advertised.
+	return "password"
+}
+
+func (maliciousGSSAPIWithMICAuthMethod) auth(session []byte, user string, c packetConn, rand io.Reader, _ map[string][]byte) (authResult, []string, error) {
+	req := &userAuthRequestMsg{
+		User:    user,
+		Service: serviceSSH,
+		Method:  "gssapi-with-mic",
+	}
+	req.Payload = appendU32(req.Payload, 1)
+	req.Payload = appendString(req.Payload, string(krb5OID))
+	if err := c.writePacket(Marshal(req)); err != nil {
+		return authFailure, nil, err
+	}
+
+	packet, err := c.readPacket()
+	if err != nil {
+		return authFailure, nil, err
+	}
+	switch packet[0] {
+	case msgUserAuthFailure:
+		var msg userAuthFailureMsg
+		if err := Unmarshal(packet, &msg); err != nil {
+			return authFailure, nil, err
+		}
+		if msg.PartialSuccess {
+			return authPartialSuccess, msg.Methods, nil
+		}
+		return authFailure, msg.Methods, nil
+	default:
+		return authFailure, nil, unexpectedMessageError(msgUserAuthFailure, packet[0])
+	}
+}
+
+func TestGSSAPIWithMICPartialConfigRejectedAtRuntime(t *testing.T) {
+	config := &ClientConfig{
+		User: "testuser",
+		Auth: []AuthMethod{
+			maliciousGSSAPIWithMICAuthMethod{},
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	clientErr, serverErrs := tryAuthBothSides(t, config, &GSSAPIWithMICConfig{
+		Server: &FakeServer{},
+	})
+
+	if clientErr == nil || !strings.Contains(clientErr.Error(), "ssh: unable to authenticate") {
+		t.Fatalf("client got %v, want authentication failure", clientErr)
+	}
+
+	found := false
+	for _, err := range serverErrs {
+		if err != nil && strings.Contains(err.Error(), "ssh: gssapi-with-mic auth not configured") {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatalf("server auth errors = %v, want gssapi-with-mic auth not configured", serverErrs)
+	}
+}
+
 func TestCompatibleAlgoAndSignatures(t *testing.T) {
 	type testcase struct {
 		algo       string
@@ -1159,6 +1946,52 @@ func TestPickSignatureAlgorithm(t *testing.T) {
 	}
 }
 
+func TestPickSignatureAlgorithmRespectsSignerPreference(t *testing.T) {
+	algoSigner, ok := testSigners["rsa"].(AlgorithmSigner)
+	if !ok {
+		t.Fatalf("rsa test signer does not implement the AlgorithmSigner interface")
+	}
+
+	serverExtensions := map[string][]byte{
+		"server-sig-algs": []byte(KeyAlgoRSASHA256 + "," + KeyAlgoRSASHA512),
+	}
+
+	tests := []struct {
+		name         string
+		signerPrefs  []string
+		expectedAlgo string
+	}{
+		{
+			name:         "Signer prefers SHA512 then SHA256",
+			signerPrefs:  []string{KeyAlgoRSASHA512, KeyAlgoRSASHA256},
+			expectedAlgo: KeyAlgoRSASHA512,
+		},
+		{
+			name:         "Signer prefers SHA256 then SHA512",
+			signerPrefs:  []string{KeyAlgoRSASHA256, KeyAlgoRSASHA512},
+			expectedAlgo: KeyAlgoRSASHA256,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			orderedSigner, err := NewSignerWithAlgorithms(algoSigner, tc.signerPrefs)
+			if err != nil {
+				t.Fatalf("failed to create ordered signer: %v", err)
+			}
+
+			_, selectedAlgo, err := pickSignatureAlgorithm(orderedSigner, serverExtensions)
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+
+			if selectedAlgo != tc.expectedAlgo {
+				t.Errorf("Algorithm mismatch; got %q want %q", selectedAlgo, tc.expectedAlgo)
+			}
+		})
+	}
+}
+
 // configurablePublicKeyCallback is a public key callback that allows to
 // configure the signature algorithm and format. This way we can emulate the
 // behavior of buggy clients.

ssh/common.go

@@ -37,6 +37,8 @@ const (
 	CipherAES192CTR            = "aes192-ctr"
 	CipherAES256CTR            = "aes256-ctr"
 	InsecureCipherAES128CBC    = "aes128-cbc"
+	InsecureCipherAES192CBC    = "aes192-cbc"
+	InsecureCipherAES256CBC    = "aes256-cbc"
 	InsecureCipherTripleDESCBC = "3des-cbc"
 	InsecureCipherRC4          = "arcfour"
 	InsecureCipherRC4128       = "arcfour128"
@@ -128,6 +130,8 @@ var (
 	// package and which have security issues.
 	insecureCiphers = []string{
 		InsecureCipherAES128CBC,
+		InsecureCipherAES192CBC,
+		InsecureCipherAES256CBC,
 		InsecureCipherTripleDESCBC,
 		InsecureCipherRC4256,
 		InsecureCipherRC4128,
@@ -419,7 +423,7 @@ type AlgorithmNegotiationError struct {
 }
 
 func (a *AlgorithmNegotiationError) Error() string {
-	return fmt.Sprintf("ssh: no common algorithm for %s; we offered: %v, peer offered: %v",
+	return fmt.Sprintf("ssh: no common algorithm for %s; we offered: %q, peer offered: %q",
 		a.What, a.SupportedAlgorithms, a.RequestedAlgorithms)
 }
 
@@ -437,7 +441,7 @@ func (a *DirectionAlgorithms) rekeyBytes() int64 {
 	// 2^(BLOCKSIZE/4) blocks. For all AES flavors BLOCKSIZE is
 	// 128.
 	switch a.Cipher {
-	case CipherAES128CTR, CipherAES192CTR, CipherAES256CTR, CipherAES128GCM, CipherAES256GCM, InsecureCipherAES128CBC:
+	case CipherAES128CTR, CipherAES192CTR, CipherAES256CTR, CipherAES128GCM, CipherAES256GCM, InsecureCipherAES128CBC, InsecureCipherAES192CBC, InsecureCipherAES256CBC:
 		return 16 * (1 << 32)
 
 	}
@@ -544,7 +548,7 @@ func (c *Config) SetDefaults() {
 	if c.Rand == nil {
 		c.Rand = rand.Reader
 	}
-	if c.Ciphers == nil {
+	if len(c.Ciphers) == 0 {
 		c.Ciphers = defaultCiphers
 	}
 	var ciphers []string
@@ -556,7 +560,7 @@ func (c *Config) SetDefaults() {
 	}
 	c.Ciphers = ciphers
 
-	if c.KeyExchanges == nil {
+	if len(c.KeyExchanges) == 0 {
 		c.KeyExchanges = defaultKexAlgos
 	}
 	var kexs []string
@@ -571,7 +575,7 @@ func (c *Config) SetDefaults() {
 	}
 	c.KeyExchanges = kexs
 
-	if c.MACs == nil {
+	if len(c.MACs) == 0 {
 		c.MACs = defaultMACs
 	}
 	var macs []string

ssh/connection.go

@@ -17,7 +17,7 @@ type OpenChannelError struct {
 }
 
 func (e *OpenChannelError) Error() string {
-	return fmt.Sprintf("ssh: rejected: %s (%s)", e.Reason, e.Message)
+	return fmt.Sprintf("ssh: rejected: %s (%q)", e.Reason, e.Message)
 }
 
 // ConnMetadata holds metadata for the connection.
@@ -91,9 +91,17 @@ func DiscardRequests(in <-chan *Request) {
 	}
 }
 
+// A connTransport represents the transport for a connection.
+type connTransport interface {
+	packetConn
+	getAlgorithms() NegotiatedAlgorithms
+	getSessionID() []byte
+	waitSession() error
+}
+
 // A connection represents an incoming connection.
 type connection struct {
-	transport *handshakeTransport
+	transport connTransport
 	sshConn
 
 	// The connection protocol.

ssh/control.go

@@ -0,0 +1,155 @@
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssh
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+
+	"golang.org/x/crypto/cryptobyte"
+)
+
+const (
+	muxProtocolVersion = 4
+
+	muxMsgHello = 0x00000001
+	muxCProxy   = 0x1000000f
+	muxSProxy   = 0x8000000f
+)
+
+const controlProxyRequestID = 0
+
+// handshakeControlProxy attempts to establish a transport connection with an
+// OpenSSH ControlMaster socket in proxy mode. For details see:
+// https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.mux
+func handshakeControlProxy(rw io.ReadWriteCloser) (connTransport, error) {
+	if err := controlProxyWritePacket(rw, func(b *cryptobyte.Builder) {
+		b.AddUint32(muxMsgHello)
+		b.AddUint32(muxProtocolVersion)
+	}); err != nil {
+		return nil, fmt.Errorf("mux hello write failed: %w", err)
+	}
+	if err := controlProxyWritePacket(rw, func(b *cryptobyte.Builder) {
+		b.AddUint32(muxCProxy)
+		b.AddUint32(controlProxyRequestID)
+	}); err != nil {
+		return nil, fmt.Errorf("mux client proxy write failed: %w", err)
+	}
+
+	messageType, body, err := controlProxyReadMessage(rw)
+	if err != nil {
+		return nil, fmt.Errorf("mux hello read failed: %w", err)
+	}
+	if messageType != muxMsgHello {
+		return nil, fmt.Errorf("expected hello response, got %v", messageType)
+	}
+	var v uint32
+	if !body.ReadUint32(&v) {
+		return nil, errors.New("EOF reading mux protocol version")
+	}
+	if v != muxProtocolVersion {
+		return nil, fmt.Errorf("mux server has unsupported version %v", v)
+	}
+	messageType, body, err = controlProxyReadMessage(rw)
+	if err != nil {
+		return nil, fmt.Errorf("mux server proxy read failed: %w", err)
+	}
+	if messageType != muxSProxy {
+		return nil, fmt.Errorf("expected server proxy response, got %v", messageType)
+	}
+	var reqID uint32
+	if !body.ReadUint32(&reqID) {
+		return nil, errors.New("EOF reading request id")
+	}
+	if reqID != controlProxyRequestID {
+		return nil, fmt.Errorf("expected request id %v, got %v", controlProxyRequestID, reqID)
+	}
+	return &controlProxyTransport{rw}, nil
+}
+
+// controlProxyTransport implements the connTransport interface for
+// ControlMaster connections. Each controlMessage has zero length padding and
+// no MAC.
+type controlProxyTransport struct {
+	rw io.ReadWriteCloser
+}
+
+func (p *controlProxyTransport) Close() error {
+	return p.rw.Close()
+}
+
+func (p *controlProxyTransport) writePacket(controlMessage []byte) error {
+	return controlProxyWritePacket(p.rw, func(b *cryptobyte.Builder) {
+		b.AddUint8(0) // Padding length.
+		b.AddBytes(controlMessage)
+	})
+}
+
+func (p *controlProxyTransport) readPacket() ([]byte, error) {
+	buf, err := controlProxyReadPacket(p.rw)
+	if err != nil {
+		return nil, fmt.Errorf("ssh: error reading control message: %w", err)
+	}
+	// Discard the padding length.
+	if len(buf) < 1 {
+		return nil, errors.New("ssh: EOF reading padding length")
+	}
+	if buf[0] != 0 {
+		return nil, errors.New("ssh: unexpected non-zero padding in control message")
+	}
+	return buf[1:], nil
+}
+
+func (p *controlProxyTransport) getAlgorithms() NegotiatedAlgorithms {
+	return NegotiatedAlgorithms{}
+}
+
+func (p *controlProxyTransport) getSessionID() []byte {
+	return nil
+}
+
+func (p *controlProxyTransport) waitSession() error {
+	return nil
+}
+
+func controlProxyWritePacket(w io.Writer, f cryptobyte.BuilderContinuation) error {
+	var buf []byte
+	b := cryptobyte.NewBuilder(buf)
+	b.AddUint32LengthPrefixed(f)
+	out, err := b.Bytes()
+	if err != nil {
+		return err
+	}
+	_, err = w.Write(out)
+	return err
+}
+
+func controlProxyReadPacket(r io.Reader) (cryptobyte.String, error) {
+	var l uint32
+	if err := binary.Read(r, binary.BigEndian, &l); err != nil {
+		return nil, err
+	}
+	if l > maxPacket {
+		return nil, fmt.Errorf("message length %v exceeds maximum %v", l, maxPacket)
+	}
+	buf := make([]byte, l)
+	if _, err := io.ReadFull(r, buf); err != nil {
+		return nil, err
+	}
+	return buf, nil
+}
+
+func controlProxyReadMessage(r io.Reader) (messageType uint32, body cryptobyte.String, err error) {
+	body, err = controlProxyReadPacket(r)
+	if err != nil {
+		return 0, nil, fmt.Errorf("error reading message body: %w", err)
+	}
+	if !body.ReadUint32(&messageType) {
+		return 0, nil, errors.New("EOF reading message type")
+	}
+	return messageType, body, nil
+}

ssh/control_test.go

@@ -0,0 +1,275 @@
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssh
+
+import (
+	"bytes"
+	"io"
+	"strings"
+	"testing"
+)
+
+func TestControlClientHandshake(t *testing.T) {
+	reqs := [][]byte{
+		// Hello request.
+		{0x00, 0x00, 0x00, 0x08, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x04},
+		// Client proxy request.
+		{0x00, 0x00, 0x00, 0x08, 0x10, 0x00, 0x00, 0x0f, 0x00, 0x00, 0x00, 0x00},
+	}
+	respsNormal := [][]byte{
+		// Hello response.
+		{0x00, 0x00, 0x00, 0x08, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x04},
+		// Server proxy response.
+		{0x00, 0x00, 0x00, 0x08, 0x80, 0x00, 0x00, 0x0f, 0x00, 0x00, 0x00, 0x00},
+	}
+	for _, tt := range []struct {
+		name        string
+		resps       [][]byte
+		expectedErr string
+	}{
+		{
+			name:  "normal handshake",
+			resps: respsNormal,
+		},
+		{
+			name: "length greater than max",
+			resps: [][]byte{
+				{0xff, 0xff, 0xff, 0xff},
+				respsNormal[1],
+			},
+			expectedErr: "message length 4294967295 exceeds maximum",
+		},
+		{
+			name: "missing hello response",
+			resps: [][]byte{
+				{},
+			},
+			expectedErr: "use of closed network connection",
+		},
+		{
+			name: "hello response too short",
+			resps: [][]byte{
+				{0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00},
+				respsNormal[1],
+			},
+			expectedErr: "EOF",
+		},
+		{
+			name: "bad hello response type",
+			resps: [][]byte{
+				{0x00, 0x00, 0x00, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04},
+				respsNormal[1],
+			},
+			expectedErr: "expected hello response, got 0",
+		},
+		{
+			name: "bad protocol version",
+			resps: [][]byte{
+				{0x00, 0x00, 0x00, 0x08, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00},
+				respsNormal[1],
+			},
+			expectedErr: "mux server has unsupported version 0",
+		},
+		{
+			name: "missing server proxy response",
+			resps: [][]byte{
+				respsNormal[0],
+			},
+			expectedErr: "use of closed network connection",
+		},
+		{
+			name: "server proxy response too short",
+			resps: [][]byte{
+				respsNormal[0],
+				{0x00, 0x00, 0x00, 0x06, 0x80, 0x00, 0x00, 0x0f, 0x00, 0x00},
+			},
+			expectedErr: "EOF",
+		},
+		{
+			name: "bad server proxy response type",
+			resps: [][]byte{
+				respsNormal[0],
+				{0x00, 0x00, 0x00, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
+			},
+			expectedErr: "expected server proxy response, got 0",
+		},
+		{
+			name: "bad request id",
+			resps: [][]byte{
+				respsNormal[0],
+				{0x00, 0x00, 0x00, 0x08, 0x80, 0x00, 0x00, 0x0f, 0x00, 0x00, 0x00, 0x01},
+			},
+			expectedErr: "expected request id 0, got 1",
+		},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			done := make(chan error, 1)
+
+			ok := func() bool {
+				c1, c2, err := netPipe()
+				if err != nil {
+					t.Fatalf("netPipe: %v", err)
+				}
+				defer c1.Close()
+				defer c2.Close()
+
+				go func() {
+					defer close(done)
+					_, _, _, err := NewControlClientConn(c2)
+					c2.Write([]byte{0}) // Dummy message to unblock the final read.
+					done <- err
+				}()
+
+				i := 0
+				for ; i < len(reqs) && i < len(tt.resps); i++ {
+					expected := reqs[i]
+					buf := make([]byte, len(expected))
+					if _, err := io.ReadFull(c1, buf); err != nil {
+						t.Errorf("error reading message %d: %v", i+1, err)
+						return false
+					}
+					if !bytes.Equal(buf, expected) {
+						t.Errorf(
+							"unexpected message %d: got %v, want %v",
+							i+1, buf, expected,
+						)
+						return false
+					}
+					_, err = c1.Write(tt.resps[i])
+					if err != nil {
+						t.Errorf("error writing message %d: %v", i+1, err)
+						return false
+					}
+				}
+				// Wait for the next message so that the final response can be read.
+				buf := make([]byte, 1)
+				c1.Read(buf)
+				return true
+			}()
+			if !ok {
+				return
+			}
+
+			err := <-done
+			if tt.expectedErr != "" {
+				if err == nil || !strings.Contains(err.Error(), tt.expectedErr) {
+					t.Fatalf("got err %q; want err containing %q", err, tt.expectedErr)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("got err %q; want no err", err)
+			}
+		})
+	}
+}
+
+func TestControlClientTransport(t *testing.T) {
+	type response struct {
+		status  bool
+		payload []byte
+		err     error
+	}
+
+	for _, tt := range []struct {
+		name        string
+		resp        []byte
+		respStatus  bool
+		respPayload []byte
+		expectedErr string
+	}{
+		{
+			name:       "successful request",
+			resp:       []byte{0x00, 0x00, 0x00, 0x02, 0x00, 0x51},
+			respStatus: true,
+		},
+		{
+			name:       "failed request",
+			resp:       []byte{0x00, 0x00, 0x00, 0x02, 0x00, 0x52},
+			respStatus: false,
+		},
+		{
+			name:        "short response",
+			resp:        []byte{0x00, 0x00, 0x00, 0x00},
+			expectedErr: "EOF",
+		},
+		{
+			name:        "response with payload",
+			resp:        []byte{0x00, 0x00, 0x00, 0x05, 0x00, 0x51, 0x01, 0x02, 0x03},
+			respStatus:  true,
+			respPayload: []byte{1, 2, 3},
+		},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			c1, c2, err := netPipe()
+			if err != nil {
+				t.Fatalf("netPipe: %v", err)
+			}
+			defer c1.Close()
+			defer c2.Close()
+
+			// Handshake responses.
+			c1.Write([]byte{
+				0x00, 0x00, 0x00, 0x08, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x04,
+				0x00, 0x00, 0x00, 0x08, 0x80, 0x00, 0x00, 0x0f, 0x00, 0x00, 0x00, 0x00,
+			})
+
+			conn, chans, reqs, err := NewControlClientConn(c2)
+			if err != nil {
+				t.Fatal(err)
+			}
+			client := NewClient(conn, chans, reqs)
+
+			done := make(chan response, 1)
+			go func() {
+				defer close(done)
+				status, payload, err := client.SendRequest("hello", true, nil)
+				if err != nil {
+					done <- response{err: err}
+					return
+				}
+				done <- response{
+					status:  status,
+					payload: payload,
+				}
+			}()
+
+			// Discard handshake.
+			io.CopyN(io.Discard, c1, 24)
+
+			expectedReq := []byte{
+				0x00, 0x00, 0x00, 0x0c, 0x00, 0x50,
+				0x00, 0x00, 0x00, 0x05, 'h', 'e', 'l', 'l', 'o',
+				0x01,
+			}
+			buf := make([]byte, len(expectedReq))
+			if _, err := io.ReadFull(c1, buf); err != nil {
+				t.Fatalf("reading request: %v", err)
+			}
+			if !bytes.Equal(buf, expectedReq) {
+				t.Fatalf("got request %v; want %v", buf, expectedReq)
+			}
+
+			c1.Write(tt.resp)
+
+			resp := <-done
+			if tt.expectedErr != "" {
+				if resp.err == nil || !strings.Contains(resp.err.Error(), tt.expectedErr) {
+					t.Fatalf("got err %q; want err containing %q", resp.err, tt.expectedErr)
+				}
+				return
+			}
+			if resp.err != nil {
+				t.Fatalf("got err %q; want no err", resp.err)
+			}
+			if resp.status != tt.respStatus {
+				t.Fatalf("got status %v; want %v", resp.status, tt.respStatus)
+			}
+			if !bytes.Equal(resp.payload, tt.respPayload) {
+				t.Errorf("got payload %v; want %v", resp.payload, tt.respPayload)
+			}
+		})
+	}
+}

ssh/handshake.go

@@ -162,7 +162,7 @@ func newClientTransport(conn keyingTransport, clientVersion, serverVersion []byt
 	t.remoteAddr = addr
 	t.hostKeyCallback = config.HostKeyCallback
 	t.bannerCallback = config.BannerCallback
-	if config.HostKeyAlgorithms != nil {
+	if len(config.HostKeyAlgorithms) > 0 {
 		t.hostKeyAlgorithms = config.HostKeyAlgorithms
 	} else {
 		t.hostKeyAlgorithms = defaultHostKeyAlgos

ssh/handshake_test.go

@@ -195,7 +195,7 @@ func TestHandshakeBasic(t *testing.T) {
 		}
 
 		want := []byte{msgRequestSuccess, byte(i)}
-		if bytes.Compare(p, want) != 0 {
+		if !bytes.Equal(p, want) {
 			t.Errorf("message %d: got %v, want %v", i, p, want)
 		}
 	}
@@ -1336,7 +1336,7 @@ func TestAlgorithmNegotiationError(t *testing.T) {
 	if !errors.As(err, &negotiationError) {
 		t.Fatalf("expected algorithm negotiation error, got %v", err)
 	}
-	expectedErrorString := fmt.Sprintf("ssh: handshake failed: ssh: no common algorithm for client to server cipher; we offered: %v, peer offered: %v",
+	expectedErrorString := fmt.Sprintf("ssh: handshake failed: ssh: no common algorithm for client to server cipher; we offered: %q, peer offered: %q",
 		clientConf.Ciphers, serverConf.Ciphers)
 	if err.Error() != expectedErrorString {
 		t.Fatalf("expected error string %q, got %q", expectedErrorString, err.Error())
@@ -1352,7 +1352,7 @@ func TestAlgorithmNegotiationError(t *testing.T) {
 	if !errors.As(err, &negotiationError) {
 		t.Fatalf("expected algorithm negotiation error, got %v", err)
 	}
-	expectedErrorString = fmt.Sprintf("ssh: no common algorithm for client to server cipher; we offered: %v, peer offered: %v",
+	expectedErrorString = fmt.Sprintf("ssh: no common algorithm for client to server cipher; we offered: %q, peer offered: %q",
 		serverConf.Ciphers, clientConf.Ciphers)
 	if err.Error() != expectedErrorString {
 		t.Fatalf("expected error string %q, got %q", expectedErrorString, err.Error())

ssh/kex.go

@@ -16,6 +16,7 @@ import (
 	"io"
 	"math/big"
 	"slices"
+	"sync"
 
 	"golang.org/x/crypto/curve25519"
 )
@@ -718,15 +719,9 @@ func (gex *dhGEXSHA) Server(c packetConn, randSource io.Reader, magics *handshak
 			kexDHGexRequest.MaxBits, kexDHGexRequest.PreferredBits)
 	}
 
-	var p *big.Int
-	// We hardcode sending Oakley Group 14 (2048 bits), Oakley Group 15 (3072
-	// bits) or Oakley Group 16 (4096 bits), based on the requested max size.
-	if kexDHGexRequest.MaxBits < 3072 {
-		p, _ = new(big.Int).SetString(oakleyGroup14, 16)
-	} else if kexDHGexRequest.MaxBits < 4096 {
-		p, _ = new(big.Int).SetString(oakleyGroup15, 16)
-	} else {
-		p, _ = new(big.Int).SetString(oakleyGroup16, 16)
+	p, err := chooseDH(kexDHGexRequest)
+	if err != nil {
+		return nil, err
 	}
 
 	g := big.NewInt(2)
@@ -805,3 +800,65 @@ func (gex *dhGEXSHA) Server(c packetConn, randSource io.Reader, magics *handshak
 		Hash:      gex.hashFunc,
 	}, err
 }
+
+type dhKEXGroup struct {
+	size int
+	p    *big.Int
+}
+
+// supportedDHKEXGroups returns the DH groups the server is willing to offer
+// for diffie-hellman-group-exchange-* key exchanges. The list is built lazily
+// on first use to keep the hex-to-big.Int parse out of package initialization.
+var supportedDHKEXGroups = sync.OnceValue(func() []dhKEXGroup {
+	specs := []struct {
+		size int
+		hex  string
+	}{
+		{2048, oakleyGroup14},
+		{3072, oakleyGroup15},
+		{4096, oakleyGroup16},
+	}
+	out := make([]dhKEXGroup, 0, len(specs))
+	for _, s := range specs {
+		p, _ := new(big.Int).SetString(s.hex, 16)
+		out = append(out, dhKEXGroup{size: s.size, p: p})
+	}
+	return out
+})
+
+// chooseDH picks a DH group for the given client request, mirroring the
+// algorithm used by OpenSSH's choose_dh in dh.c: prefer the smallest known
+// group larger than  or equal to the client's PreferredBits, and otherwise pick
+// the largest group within the accepted [MinBits, MaxBits] range.
+func chooseDH(req kexDHGexRequestMsg) (*big.Int, error) {
+	var best *big.Int
+	bestSize := 0
+	wantBits := int(req.PreferredBits)
+
+	for _, group := range supportedDHKEXGroups() {
+		if uint32(group.size) < req.MinBits || uint32(group.size) > req.MaxBits {
+			continue
+		}
+
+		if bestSize == 0 {
+			best = group.p
+			bestSize = group.size
+			continue
+		}
+
+		closerFromAbove := group.size >= wantBits && group.size < bestSize
+		closerFromBelow := group.size > bestSize && bestSize < wantBits
+
+		if closerFromAbove || closerFromBelow {
+			best = group.p
+			bestSize = group.size
+		}
+	}
+
+	if bestSize == 0 {
+		return nil, fmt.Errorf("ssh: no suitable DH group found for request min: %d, preferred: %d, max: %d",
+			req.MinBits, req.PreferredBits, req.MaxBits)
+	}
+
+	return best, nil
+}