go.mod: update golang.org/x dependencies

Update golang.org/x dependencies to their latest tagged versions.

Change-Id: Ia739869d49c750c7fa578b9dbd7bb998d8c87087
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/781683
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Nicholas Husin <nsh@golang.org>
Auto-Submit: Gopher Robot <gobot@golang.org>
Reviewed-by: Nicholas Husin <husin@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>

acme/acme.go

@@ -690,7 +690,7 @@ func (c *Client) addNonce(h http.Header) {
 }
 
 func (c *Client) fetchNonce(ctx context.Context, url string) (string, error) {
-	r, err := http.NewRequest("HEAD", url, nil)
+	r, err := http.NewRequestWithContext(ctx, "HEAD", url, nil)
 	if err != nil {
 		return "", err
 	}

acme/autocert/autocert.go

@@ -134,7 +134,8 @@ type Manager struct {
 	// RenewBefore optionally specifies how early certificates should
 	// be renewed before they expire.
 	//
-	// If zero, they're renewed 30 days before expiration.
+	// If zero, they're renewed at the lesser of 30 days or
+	// 1/3 of the certificate lifetime.
 	RenewBefore time.Duration
 
 	// Client is used to perform low-level operations, such as account registration
@@ -247,10 +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")
@@ -464,7 +461,7 @@ func (m *Manager) cert(ctx context.Context, ck certKey) (*tls.Certificate, error
 		leaf: cert.Leaf,
 	}
 	m.state[ck] = s
-	m.startRenew(ck, s.key, s.leaf.NotAfter)
+	m.startRenew(ck, s.key, s.leaf.NotBefore, s.leaf.NotAfter)
 	return cert, nil
 }
 
@@ -610,7 +607,7 @@ func (m *Manager) createCert(ctx context.Context, ck certKey) (*tls.Certificate,
 	}
 	state.cert = der
 	state.leaf = leaf
-	m.startRenew(ck, state.key, state.leaf.NotAfter)
+	m.startRenew(ck, state.key, state.leaf.NotBefore, state.leaf.NotAfter)
 	return state.tlscert()
 }
 
@@ -908,7 +905,7 @@ func httpTokenCacheKey(tokenPath string) string {
 //
 // The key argument is a certificate private key.
 // The exp argument is the cert expiration time (NotAfter).
-func (m *Manager) startRenew(ck certKey, key crypto.Signer, exp time.Time) {
+func (m *Manager) startRenew(ck certKey, key crypto.Signer, notBefore, notAfter time.Time) {
 	m.renewalMu.Lock()
 	defer m.renewalMu.Unlock()
 	if m.renewal[ck] != nil {
@@ -920,7 +917,7 @@ func (m *Manager) startRenew(ck certKey, key crypto.Signer, exp time.Time) {
 	}
 	dr := &domainRenewal{m: m, ck: ck, key: key}
 	m.renewal[ck] = dr
-	dr.start(exp)
+	dr.start(notBefore, notAfter)
 }
 
 // stopRenew stops all currently running cert renewal timers.
@@ -1028,13 +1025,6 @@ func (m *Manager) hostPolicy() HostPolicy {
 	return defaultHostPolicy
 }
 
-func (m *Manager) renewBefore() time.Duration {
-	if m.RenewBefore > renewJitter {
-		return m.RenewBefore
-	}
-	return 720 * time.Hour // 30 days
-}
-
 func (m *Manager) now() time.Time {
 	if m.nowFunc != nil {
 		return m.nowFunc()

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",
@@ -561,9 +561,9 @@ func TestHTTPHandlerDefaultFallback(t *testing.T) {
 		{"GET", "http://example.org/foo?a=b", 302, "https://example.org/foo?a=b"},
 		{"GET", "http://example.org:80/foo?a=b", 302, "https://example.org:443/foo?a=b"},
 		{"GET", "http://example.org:80/foo%20bar", 302, "https://example.org:443/foo%20bar"},
-		{"GET", "http://[2602:d1:xxxx::c60a]:1234", 302, "https://[2602:d1:xxxx::c60a]:443/"},
+		{"GET", "http://[2602:d1:abcd::c60a]:1234", 302, "https://[2602:d1:abcd::c60a]:443/"},
-		{"GET", "http://[2602:d1:xxxx::c60a]", 302, "https://[2602:d1:xxxx::c60a]/"},
+		{"GET", "http://[2602:d1:abcd::c60a]", 302, "https://[2602:d1:abcd::c60a]/"},
-		{"GET", "http://[2602:d1:xxxx::c60a]/foo?a=b", 302, "https://[2602:d1:xxxx::c60a]/foo?a=b"},
+		{"GET", "http://[2602:d1:abcd::c60a]/foo?a=b", 302, "https://[2602:d1:abcd::c60a]/foo?a=b"},
 		{"HEAD", "http://example.org", 302, "https://example.org/"},
 		{"HEAD", "http://example.org/foo", 302, "https://example.org/foo"},
 		{"HEAD", "http://example.org/foo/bar/", 302, "https://example.org/foo/bar/"},

acme/autocert/internal/acmetest/ca.go

@@ -145,7 +145,7 @@ func (ca *CAServer) URL() string {
 	return ca.url
 }
 
-// Roots returns a pool cointaining the CA root.
+// Roots returns a pool containing the CA root.
 func (ca *CAServer) Roots() *x509.CertPool {
 	if ca.url == "" {
 		panic("Roots called before Start")
@@ -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.go

@@ -11,9 +11,6 @@ import (
 	"time"
 )
 
-// renewJitter is the maximum deviation from Manager.RenewBefore.
-const renewJitter = time.Hour
-
 // domainRenewal tracks the state used by the periodic timers
 // renewing a single domain's cert.
 type domainRenewal struct {
@@ -30,13 +27,13 @@ type domainRenewal struct {
 // defined by the certificate expiration time exp.
 //
 // If the timer is already started, calling start is a noop.
-func (dr *domainRenewal) start(exp time.Time) {
+func (dr *domainRenewal) start(notBefore, notAfter time.Time) {
 	dr.timerMu.Lock()
 	defer dr.timerMu.Unlock()
 	if dr.timer != nil {
 		return
 	}
-	dr.timer = time.AfterFunc(dr.next(exp), dr.renew)
+	dr.timer = time.AfterFunc(dr.next(notBefore, notAfter), dr.renew)
 }
 
 // stop stops the cert renewal timer and waits for any in-flight calls to renew
@@ -79,7 +76,7 @@ func (dr *domainRenewal) renew() {
 	// TODO: rotate dr.key at some point?
 	next, err := dr.do(ctx)
 	if err != nil {
-		next = renewJitter / 2
+		next = time.Hour / 2
 		next += time.Duration(pseudoRand.int63n(int64(next)))
 	}
 	testDidRenewLoop(next, err)
@@ -107,8 +104,8 @@ func (dr *domainRenewal) do(ctx context.Context) (time.Duration, error) {
 	// a race is likely unavoidable in a distributed environment
 	// but we try nonetheless
 	if tlscert, err := dr.m.cacheGet(ctx, dr.ck); err == nil {
-		next := dr.next(tlscert.Leaf.NotAfter)
+		next := dr.next(tlscert.Leaf.NotBefore, tlscert.Leaf.NotAfter)
-		if next > dr.m.renewBefore()+renewJitter {
+		if next > 0 {
 			signer, ok := tlscert.PrivateKey.(crypto.Signer)
 			if ok {
 				state := &certState{
@@ -139,18 +136,23 @@ func (dr *domainRenewal) do(ctx context.Context) (time.Duration, error) {
 		return 0, err
 	}
 	dr.updateState(state)
-	return dr.next(leaf.NotAfter), nil
+	return dr.next(leaf.NotBefore, leaf.NotAfter), nil
 }
 
-func (dr *domainRenewal) next(expiry time.Time) time.Duration {
+// next returns the wait time before the next renewal should start.
-	d := expiry.Sub(dr.m.now()) - dr.m.renewBefore()
+// If manager.RenewBefore is set, it uses that capped at 30 days,
-	// add a bit of randomness to renew deadline
+// otherwise it uses a default of 1/3 of the cert lifetime.
-	n := pseudoRand.int63n(int64(renewJitter))
+// It builds in a jitter of 10% of the renew threshold, capped at 1 hour.
-	d -= time.Duration(n)
+func (dr *domainRenewal) next(notBefore, notAfter time.Time) time.Duration {
-	if d < 0 {
+	threshold := min(notAfter.Sub(notBefore)/3, 30*24*time.Hour)
-		return 0
+	if dr.m.RenewBefore > 0 {
+		threshold = min(dr.m.RenewBefore, 30*24*time.Hour)
 	}
-	return d
+	maxJitter := min(threshold/10, time.Hour)
+	jitter := pseudoRand.int63n(int64(maxJitter))
+	renewAt := notAfter.Add(-(threshold - time.Duration(jitter)))
+	renewWait := renewAt.Sub(dr.m.now())
+	return max(0, renewWait)
 }
 
 var testDidRenewLoop = func(next time.Duration, err error) {}

acme/autocert/renewal_test.go

@@ -17,27 +17,60 @@ import (
 
 func TestRenewalNext(t *testing.T) {
 	now := time.Now()
-	man := &Manager{
+	nowFn := func() time.Time { return now }
-		RenewBefore: 7 * 24 * time.Hour,
-		nowFunc:     func() time.Time { return now },
-	}
-	defer man.stopRenew()
 	tt := []struct {
-		expiry   time.Time
+		name        string
-		min, max time.Duration
+		renewBefore time.Duration // arg to Manager
+		// leaf cert validity
+		notBefore time.Time
+		validFor  time.Duration
+		// wait time
+		waitMin, waitMax time.Duration
 	}{
-		{now.Add(90 * 24 * time.Hour), 83*24*time.Hour - renewJitter, 83 * 24 * time.Hour},
+		{"default renewal, 1h cert, valid",
-		{now.Add(time.Hour), 0, 1},
+			0, now, time.Hour, 40 * time.Minute, 50 * time.Minute},
-		{now, 0, 1},
+		{"default renewal, 1h cert, should renew",
-		{now.Add(-time.Hour), 0, 1},
+			0, now.Add(-50 * time.Minute), time.Hour, 0, 0},
+		{"default renewal, 1h cert, expired",
+			0, now.Add(-400 * 24 * time.Hour), time.Hour, 0, 0},
+		{"default renewal, 6d cert, valid",
+			0, now, 6 * 24 * time.Hour, 4 * 24 * time.Hour, (4*24 + 1) * time.Hour},
+		{"default renewal, 6d cert, should renew",
+			0, now.Add(-5 * 24 * time.Hour), 6 * 24 * time.Hour, 0, 0},
+		{"default renewal, 6d cert, expired",
+			0, now.Add(-400 * 24 * time.Hour), 6 * 24 * time.Hour, 0, 0},
+		{"default renewal, 90d cert, valid",
+			0, now, 90 * 24 * time.Hour, 60 * 24 * time.Hour, (60*24 + 1) * time.Hour},
+		{"default renewal, 90d cert, should renew",
+			0, now.Add(-70 * 24 * time.Hour), 90 * 24 * time.Hour, 0, 0},
+		{"default renewal, 90d cert, expired",
+			0, now.Add(-400 * 24 * time.Hour), 90 * 24 * time.Hour, 0, 0},
+		{"default renewal, 398d cert, valid",
+			0, now, 398 * 24 * time.Hour, (368 * 24) * time.Hour, (368*24 + 1) * time.Hour},
+		{"default renewal, 398d cert, should renew",
+			0, now.Add(-378 * 24 * time.Hour), 398 * 24 * time.Hour, 0, 0},
+		{"default renewal, 398d cert, expired",
+			0, now.Add(-400 * 24 * time.Hour), 398 * 24 * time.Hour, 0, 0},
+		{"7d renewal, 90d cert, valid",
+			7 * 24 * time.Hour, now, 90 * 24 * time.Hour, 83 * 24 * time.Hour, (83*24 + 1) * time.Hour},
+		{"7d renewal, 90d cert, should not renew",
+			7 * 24 * time.Hour, now.Add(-70 * 24 * time.Hour), 90 * 24 * time.Hour, 13 * 24 * time.Hour, (13*24 + 1) * time.Hour},
+		{"7d renewal, 90d cert, should renew",
+			7 * 24 * time.Hour, now.Add(-85 * 24 * time.Hour), 90 * 24 * time.Hour, 0, 0},
+		{"7d renewal, 90d cert, expired",
+			7 * 24 * time.Hour, now.Add(-400 * 24 * time.Hour), 90 * 24 * time.Hour, 0, 0},
 	}
 
-	dr := &domainRenewal{m: man}
+	for _, test := range tt {
-	for i, test := range tt {
+		t.Run(test.name, func(t *testing.T) {
-		next := dr.next(test.expiry)
+			dr := &domainRenewal{m: &Manager{RenewBefore: test.renewBefore, nowFunc: nowFn}}
-		if next < test.min || test.max < next {
+			defer dr.m.stopRenew()
-			t.Errorf("%d: next = %v; want between %v and %v", i, next, test.min, test.max)
+
-		}
+			next := dr.next(test.notBefore, test.notBefore.Add(test.validFor))
+			if next < test.waitMin || next > test.waitMax {
+				t.Errorf("expected wait time: %v <= %v <= %v", test.waitMin, next, test.waitMax)
+			}
+		})
 	}
 }
 
@@ -147,9 +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)
@@ -239,7 +269,7 @@ func TestRenewFromCacheAlreadyRenewed(t *testing.T) {
 	}
 
 	// trigger renew
-	man.startRenew(exampleCertKey, s.key, s.leaf.NotAfter)
+	man.startRenew(exampleCertKey, s.key, s.leaf.NotBefore, s.leaf.NotAfter)
 	<-renewed
 	func() {
 		man.renewalMu.Lock()

acme/http.go

@@ -128,7 +128,7 @@ func wantStatus(codes ...int) resOkay {
 func (c *Client) get(ctx context.Context, url string, ok resOkay) (*http.Response, error) {
 	retry := c.retryTimer()
 	for {
-		req, err := http.NewRequest("GET", url, nil)
+		req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
 		if err != nil {
 			return nil, err
 		}
@@ -228,7 +228,7 @@ func (c *Client) postNoRetry(ctx context.Context, key crypto.Signer, url string,
 	if err != nil {
 		return nil, nil, err
 	}
-	req, err := http.NewRequest("POST", url, bytes.NewReader(b))
+	req, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewReader(b))
 	if err != nil {
 		return nil, nil, err
 	}

acme/pebble_test.go

@@ -757,7 +757,7 @@ func prepareBinaries(t *testing.T, pebbleDir string) string {
 
 	// We don't want to build in the module cache dir, which might not be
 	// writable or to pollute the user's clone with binaries if pebbleLocalDir
-	//is used.
+	// is used.
 	binDir := t.TempDir()
 
 	build := func(cmd string) {

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)
 	}
 
@@ -232,7 +235,7 @@ func (c *Client) AuthorizeOrder(ctx context.Context, id []AuthzID, opt ...OrderO
 	return responseOrder(res)
 }
 
-// GetOrder retrives an order identified by the given URL.
+// GetOrder retrieves an order identified by the given URL.
 // For orders created with AuthorizeOrder, the url value is Order.URI.
 //
 // If a caller needs to poll an order until its status is final,

acme/types.go

@@ -167,7 +167,11 @@ 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

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

@@ -6,7 +6,7 @@
 // Argon2 was selected as the winner of the Password Hashing Competition and can
 // be used to derive cryptographic keys from passwords.
 //
-// For a detailed specification of Argon2 see [1].
+// For a detailed specification of Argon2 see [argon2-specs.pdf].
 //
 // If you aren't sure which function you need, use Argon2id (IDKey) and
 // the parameter recommendations for your scenario.
@@ -17,7 +17,7 @@
 // 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 [2]) for non-interactive operations are time=3 and to
+// parameters (taken from [RFC 9106 Section 7.3]) for non-interactive operations are time=3 and to
 // use the maximum available memory.
 //
 // # Argon2id
@@ -27,11 +27,11 @@
 // 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 [2]) are time=1 and to
+// parameters for non-interactive operations (taken from [RFC 9106 Section 7.3]) are time=1 and to
 // use the maximum available memory.
 //
-// [1] https://github.com/P-H-C/phc-winner-argon2/blob/master/argon2-specs.pdf
+// [argon2-specs.pdf]: https://github.com/P-H-C/phc-winner-argon2/blob/master/argon2-specs.pdf
-// [2] https://tools.ietf.org/html/draft-irtf-cfrg-argon2-03#section-9.3
+// [RFC 9106 Section 7.3]: https://www.rfc-editor.org/rfc/rfc9106.html#section-7.3
 package argon2
 
 import (
@@ -59,7 +59,7 @@ const (
 //
 //	key := argon2.Key([]byte("some password"), salt, 3, 32*1024, 4, 32)
 //
-// The draft RFC recommends[2] time=3, and memory=32*1024 is a sensible number.
+// [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.
 //
@@ -69,6 +69,8 @@ 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)
 }
@@ -83,7 +85,7 @@ func Key(password, salt []byte, time, memory uint32, threads uint8, keyLen uint3
 //
 //	key := argon2.IDKey([]byte("some password"), salt, 1, 64*1024, 4, 32)
 //
-// The draft RFC recommends[2] time=1, and memory=64*1024 is a sensible number.
+// [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.
 //
@@ -93,6 +95,8 @@ func Key(password, salt []byte, time, memory uint32, threads uint8, keyLen uint3
 // 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
 func IDKey(password, salt []byte, time, memory uint32, threads uint8, keyLen uint32) []byte {
 	return deriveKey(argon2id, password, salt, nil, nil, time, memory, threads, keyLen)
 }

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_arm64.s

@@ -29,7 +29,7 @@ loop:
 	MOVD	$NUM_ROUNDS, R21
 	VLD1	(R11), [V30.S4, V31.S4]
 
-	// load contants
+	// load constants
 	// VLD4R (R10), [V0.S4, V1.S4, V2.S4, V3.S4]
 	WORD	$0x4D60E940
 

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)
 	}
 
@@ -56,14 +56,17 @@ func (c *chacha20poly1305) seal(dst, nonce, plaintext, additionalData []byte) []
 
 	ret, out := sliceForAppend(dst, len(plaintext)+16)
 	if alias.InexactOverlap(out, plaintext) {
-		panic("chacha20poly1305: invalid buffer overlap")
+		panic("chacha20poly1305: invalid buffer overlap of output and input")
+	}
+	if alias.AnyOverlap(out, additionalData) {
+		panic("chacha20poly1305: invalid buffer overlap of output and additional data")
 	}
 	chacha20Poly1305Seal(out[:], state[:], plaintext, additionalData)
 	return ret
 }
 
 func (c *chacha20poly1305) open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) {
-	if !cpu.X86.HasSSSE3 {
+	if !useAVX2 {
 		return c.openGeneric(dst, nonce, ciphertext, additionalData)
 	}
 
@@ -73,7 +76,10 @@ func (c *chacha20poly1305) open(dst, nonce, ciphertext, additionalData []byte) (
 	ciphertext = ciphertext[:len(ciphertext)-16]
 	ret, out := sliceForAppend(dst, len(ciphertext))
 	if alias.InexactOverlap(out, ciphertext) {
-		panic("chacha20poly1305: invalid buffer overlap")
+		panic("chacha20poly1305: invalid buffer overlap of output and input")
+	}
+	if alias.AnyOverlap(out, additionalData) {
+		panic("chacha20poly1305: invalid buffer overlap of output and additional data")
 	}
 	if !chacha20Poly1305Open(out, state[:], ciphertext, additionalData) {
 		for i := range out {

chacha20poly1305/chacha20poly1305_generic.go

@@ -31,7 +31,10 @@ func (c *chacha20poly1305) sealGeneric(dst, nonce, plaintext, additionalData []b
 	ret, out := sliceForAppend(dst, len(plaintext)+poly1305.TagSize)
 	ciphertext, tag := out[:len(plaintext)], out[len(plaintext):]
 	if alias.InexactOverlap(out, plaintext) {
-		panic("chacha20poly1305: invalid buffer overlap")
+		panic("chacha20poly1305: invalid buffer overlap of output and input")
+	}
+	if alias.AnyOverlap(out, additionalData) {
+		panic("chacha20poly1305: invalid buffer overlap of output and additional data")
 	}
 
 	var polyKey [32]byte
@@ -67,7 +70,10 @@ func (c *chacha20poly1305) openGeneric(dst, nonce, ciphertext, additionalData []
 
 	ret, out := sliceForAppend(dst, len(ciphertext))
 	if alias.InexactOverlap(out, ciphertext) {
-		panic("chacha20poly1305: invalid buffer overlap")
+		panic("chacha20poly1305: invalid buffer overlap of output and input")
+	}
+	if alias.AnyOverlap(out, additionalData) {
+		panic("chacha20poly1305: invalid buffer overlap of output and additional data")
 	}
 	if !p.Verify(tag) {
 		for i := range out {

chacha20poly1305/chacha20poly1305_test.go

@@ -153,7 +153,7 @@ func TestRandom(t *testing.T) {
 	t.Run("X", func(t *testing.T) { f(t, NonceSizeX) })
 }
 
-func benchamarkChaCha20Poly1305Seal(b *testing.B, buf []byte, nonceSize int) {
+func benchmarkChaCha20Poly1305Seal(b *testing.B, buf []byte, nonceSize int) {
 	b.ReportAllocs()
 	b.SetBytes(int64(len(buf)))
 
@@ -176,7 +176,7 @@ func benchamarkChaCha20Poly1305Seal(b *testing.B, buf []byte, nonceSize int) {
 	}
 }
 
-func benchamarkChaCha20Poly1305Open(b *testing.B, buf []byte, nonceSize int) {
+func benchmarkChaCha20Poly1305Open(b *testing.B, buf []byte, nonceSize int) {
 	b.ReportAllocs()
 	b.SetBytes(int64(len(buf)))
 
@@ -204,17 +204,17 @@ func benchamarkChaCha20Poly1305Open(b *testing.B, buf []byte, nonceSize int) {
 func BenchmarkChacha20Poly1305(b *testing.B) {
 	for _, length := range []int{64, 1350, 8 * 1024} {
 		b.Run("Open-"+strconv.Itoa(length), func(b *testing.B) {
-			benchamarkChaCha20Poly1305Open(b, make([]byte, length), NonceSize)
+			benchmarkChaCha20Poly1305Open(b, make([]byte, length), NonceSize)
 		})
 		b.Run("Seal-"+strconv.Itoa(length), func(b *testing.B) {
-			benchamarkChaCha20Poly1305Seal(b, make([]byte, length), NonceSize)
+			benchmarkChaCha20Poly1305Seal(b, make([]byte, length), NonceSize)
 		})
 
 		b.Run("Open-"+strconv.Itoa(length)+"-X", func(b *testing.B) {
-			benchamarkChaCha20Poly1305Open(b, make([]byte, length), NonceSizeX)
+			benchmarkChaCha20Poly1305Open(b, make([]byte, length), NonceSizeX)
 		})
 		b.Run("Seal-"+strconv.Itoa(length)+"-X", func(b *testing.B) {
-			benchamarkChaCha20Poly1305Seal(b, make([]byte, length), NonceSizeX)
+			benchmarkChaCha20Poly1305Seal(b, make([]byte, length), NonceSizeX)
 		})
 	}
 }

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"
+func fips140Enforced() bool { return false }
-
-var _ hash.XOF = (*xof)(nil)

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")
 	}

curve25519/curve25519.go

@@ -3,11 +3,14 @@
 // license that can be found in the LICENSE file.
 
 // Package curve25519 provides an implementation of the X25519 function, which
-// performs scalar multiplication on the elliptic curve known as Curve25519.
+// performs scalar multiplication on the elliptic curve known as Curve25519
-// See RFC 7748.
+// according to [RFC 7748].
 //
-// This package is a wrapper for the X25519 implementation
+// The curve25519 package is a wrapper for the X25519 implementation in the
-// in the crypto/ecdh package.
+// crypto/ecdh package. It is [frozen] and is not accepting new features.
+//
+// [RFC 7748]: https://datatracker.ietf.org/doc/html/rfc7748
+// [frozen]: https://go.dev/wiki/Frozen
 package curve25519
 
 import "crypto/ecdh"

ed25519/ed25519.go

@@ -2,16 +2,19 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Package ed25519 implements the Ed25519 signature algorithm. See
+// Package ed25519 implements the Ed25519 signature algorithm.
-// https://ed25519.cr.yp.to/.
 //
 // These functions are also compatible with the “Ed25519” function defined in
-// RFC 8032. However, unlike RFC 8032's formulation, this package's private key
+// [RFC 8032]. However, unlike RFC 8032's formulation, this package's private key
 // representation includes a public key suffix to make multiple signing
 // operations with the same key more efficient. This package refers to the RFC
 // 8032 private key as the “seed”.
 //
-// This package is a wrapper around the standard library crypto/ed25519 package.
+// The ed25519 package is a wrapper for the Ed25519 implementation in the
+// crypto/ed25519 package. It is [frozen] and is not accepting new features.
+//
+// [RFC 8032]: https://datatracker.ietf.org/doc/html/rfc8032
+// [frozen]: https://go.dev/wiki/Frozen
 package ed25519
 
 import (

go.mod

@@ -1,11 +1,11 @@
 module golang.org/x/crypto
 
-go 1.24.0
+go 1.25.0
 
 require (
-	golang.org/x/net v0.43.0 // tagx:ignore
+	golang.org/x/net v0.54.0 // tagx:ignore
-	golang.org/x/sys v0.36.0
+	golang.org/x/sys v0.45.0
-	golang.org/x/term v0.35.0
+	golang.org/x/term v0.43.0
 )
 
-require golang.org/x/text v0.29.0 // indirect
+require golang.org/x/text v0.37.0 // indirect

go.sum

@@ -1,8 +1,8 @@
-golang.org/x/net v0.43.0 h1:lat02VYK2j4aLzMzecihNvTlJNQUq316m2Mr9rnM6YE=
+golang.org/x/net v0.54.0 h1:2zJIZAxAHV/OHCDTCOHAYehQzLfSXuf/5SoL/Dv6w/w=
-golang.org/x/net v0.43.0/go.mod h1:vhO1fvI4dGsIjh73sWfUVjj3N7CA9WkKJNQm2svM6Jg=
+golang.org/x/net v0.54.0/go.mod h1:Sj4oj8jK6XmHpBZU/zWHw3BV3abl4Kvi+Ut7cQcY+cQ=
-golang.org/x/sys v0.36.0 h1:KVRy2GtZBrk1cBYA7MKu5bEZFxQk4NIDV6RLVcC8o0k=
+golang.org/x/sys v0.45.0 h1:dO4czNzziLiiXplLQgBCEpCvXQ3dnkn0SdaZSYdQ+FY=
-golang.org/x/sys v0.36.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/sys v0.45.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
-golang.org/x/term v0.35.0 h1:bZBVKBudEyhRcajGcNc3jIfWPqV4y/Kt2XcoigOWtDQ=
+golang.org/x/term v0.43.0 h1:S4RLU2sB31O/NCl+zFN9Aru9A/Cq2aqKpTZJ6B+DwT4=
-golang.org/x/term v0.35.0/go.mod h1:TPGtkTLesOwf2DE8CgVYiZinHAOuy5AYUYT1lENIZnA=
+golang.org/x/term v0.43.0/go.mod h1:lrhlHNdQJHO+1qVYiHfFKVuVioJIheAc3fBSMFYEIsk=
-golang.org/x/text v0.29.0 h1:1neNs90w9YzJ9BocxfsQNHKuAT4pkghyXc4nhZ6sJvk=
+golang.org/x/text v0.37.0 h1:Cqjiwd9eSg8e0QAkyCaQTNHFIIzWtidPahFWR83rTrc=
-golang.org/x/text v0.29.0/go.mod h1:7MhJOA9CD2qZyOKYazxdYMF85OwPdEr9jTtBpO7ydH4=
+golang.org/x/text v0.37.0/go.mod h1:a5sjxXGs9hsn/AJVwuElvCAo9v8QYLzvavO5z2PiM38=

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 {
+	// Use the stdlib Extract, which disables FIPS 140 enforcement of the HMAC
-		salt = make([]byte, hash().Size())
+	// 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)
+	return out
-	extractor.Write(secret)
-	return extractor.Sum(nil)
 }
 
-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/wycheproof/rsa_pss_test.go

@@ -141,7 +141,7 @@ func TestRsaPss(t *testing.T) {
 			}
 			// Run all the tests twice: the first time with the salt length
 			// as PSSSaltLengthAuto, and the second time with the salt length
-			// explictily set to tg.SLen.
+			// explicitly set to tg.SLen.
 			for i := 0; i < 2; i++ {
 				for _, sig := range tg.Tests {
 					h.Reset()

nacl/auth/auth.go

@@ -2,25 +2,16 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-/*
+// Package auth authenticates a message using a secret key.
-Package auth authenticates a message using a secret key.
+//
-
+// This package is interoperable with [NaCl].
-The Sum function, viewed as a function of the message for a uniform random
+//
-key, is designed to meet the standard notion of unforgeability. This means
+// The auth package is essentially a wrapper for HMAC-SHA-512 (implemented by
-that an attacker cannot find authenticators for any messages not authenticated
+// crypto/hmac and crypto/sha512), truncated to 32 bytes. It is [frozen] and is
-by the sender, even if the attacker has adaptively influenced the messages
+// not accepting new features.
-authenticated by the sender. For a formal definition see, e.g., Section 2.4
+//
-of Bellare, Kilian, and Rogaway, "The security of the cipher block chaining
+// [NaCl]: https://nacl.cr.yp.to/auth.html
-message authentication code," Journal of Computer and System Sciences 61 (2000),
+// [frozen]: https://go.dev/wiki/Frozen
-362–399; http://www-cse.ucsd.edu/~mihir/papers/cbc.html.
-
-auth does not make any promises regarding "strong" unforgeability; perhaps
-one valid authenticator can be converted into another valid authenticator for
-the same message. NaCl also does not make any promises regarding "truncated
-unforgeability."
-
-This package is interoperable with NaCl: https://nacl.cr.yp.to/auth.html.
-*/
 package auth
 
 import (

nacl/box/box_test.go

@@ -114,7 +114,7 @@ func TestSealOpenAnonymous(t *testing.T) {
 		t.Fatal("expected out to be unchanged")
 	}
 	if !bytes.HasPrefix(box, orig) {
-		t.Fatal("expected out to be coppied to returned slice")
+		t.Fatal("expected out to be copied to returned slice")
 	}
 	_, ok = OpenAnonymous(nil, box[len(out):], publicKey, privateKey)
 	if !ok {

nacl/sign/sign.go

@@ -4,20 +4,15 @@
 
 // Package sign signs small messages using public-key cryptography.
 //
-// Sign uses Ed25519 to sign messages. The length of messages is not hidden.
+// This package is interoperable with [libsodium], as well as [TweetNaCl].
-// Messages should be small because:
-// 1. The whole message needs to be held in memory to be processed.
-// 2. Using large messages pressures implementations on small machines to process
-// plaintext without verifying the signature. This is very dangerous, and this API
-// discourages it, but a protocol that uses excessive message sizes might present
-// some implementations with no other choice.
-// 3. Performance may be improved by working with messages that fit into data caches.
-// Thus large amounts of data should be chunked so that each message is small.
 //
-// This package is not interoperable with the current release of NaCl
+// The sign package is essentially a wrapper for the Ed25519 signature
-// (https://nacl.cr.yp.to/sign.html), which does not support Ed25519 yet. However,
+// algorithm (implemented by crypto/ed25519). It is [frozen] and is not accepting
-// it is compatible with the NaCl fork libsodium (https://www.libsodium.org), as well
+// new features.
-// as TweetNaCl (https://tweetnacl.cr.yp.to/).
+//
+// [libsodium]: https://libsodium.gitbook.io/doc/public-key_cryptography/public-key_signatures
+// [TweetNaCl]: https://tweetnacl.cr.yp.to/
+// [frozen]: https://go.dev/wiki/Frozen
 package sign
 
 import (

nacl/sign/sign_test.go

@@ -69,6 +69,6 @@ func TestGenerateSignOpen(t *testing.T) {
 	}
 
 	if !bytes.Equal(message, testMessage) {
-		t.Fatalf("verified message does not match signed messge, got\n%x\n, expected\n%x", message, testMessage)
+		t.Fatalf("verified message does not match signed message, got\n%x\n, expected\n%x", message, testMessage)
 	}
 }

openpgp/packet/opaque_test.go

@@ -51,7 +51,7 @@ func TestOpaqueParseReason(t *testing.T) {
 	const expectedBad = 3
 	// Test post-conditions, make sure we actually parsed packets as expected.
 	if badPackets != expectedBad {
-		t.Errorf("unexpected # unparseable packets: %d (want %d)", badPackets, expectedBad)
+		t.Errorf("unexpected # unparsable packets: %d (want %d)", badPackets, expectedBad)
 	}
 	if uid == nil {
 		t.Errorf("failed to find expected UID in unsupported keyring")

openpgp/s2k/s2k.go

@@ -53,7 +53,7 @@ func (c *Config) hash() crypto.Hash {
 
 func (c *Config) encodedCount() uint8 {
 	if c == nil || c.S2KCount == 0 {
-		return 96 // The common case. Correspoding to 65536
+		return 96 // The common case. Corresponding to 65536
 	}
 
 	i := c.S2KCount

otr/otr.go

@@ -8,6 +8,10 @@
 // The version of OTR implemented by this package has been deprecated
 // (https://bugs.otr.im/lib/libotr/issues/140). An implementation of OTRv3 is
 // available at https://github.com/coyim/otr3.
+//
+// The otr package is [frozen] and is not accepting new features.
+//
+// [frozen]: https://go.dev/wiki/Frozen
 package otr
 
 import (

otr/otr_test.go

@@ -75,8 +75,8 @@ const libOTRPrivateKey = `(privkeys
  (account
 (name "foo@example.com")
 (protocol prpl-jabber)
-(private-key 
+(private-key
- (dsa 
+ (dsa
   (p #00FC07ABCF0DC916AFF6E9AE47BEF60C7AB9B4D6B2469E436630E36F8A489BE812486A09F30B71224508654940A835301ACC525A4FF133FC152CC53DCC59D65C30A54F1993FE13FE63E5823D4C746DB21B90F9B9C00B49EC7404AB1D929BA7FBA12F2E45C6E0A651689750E8528AB8C031D3561FECEE72EBB4A090D450A9B7A857#)
   (q #00997BD266EF7B1F60A5C23F3A741F2AEFD07A2081#)
   (g #535E360E8A95EBA46A4F7DE50AD6E9B2A6DB785A66B64EB9F20338D2A3E8FB0E94725848F1AA6CC567CB83A1CC517EC806F2E92EAE71457E80B2210A189B91250779434B41FC8A8873F6DB94BEA7D177F5D59E7E114EE10A49CFD9CEF88AE43387023B672927BA74B04EB6BBB5E57597766A2F9CE3857D7ACE3E1E3BC1FC6F26#)
@@ -402,7 +402,7 @@ func TestAgainstLibOTR(t *testing.T) {
 	// This test requires otr.c.test to be built as /tmp/a.out.
 	// If enabled, this tests runs forever performing OTR handshakes in a
 	// loop.
-	return
+	t.Skip("This test requires otr.c.test to be built as /tmp/a.out")
 
 	alicePrivateKey, _ := hex.DecodeString(alicePrivateKeyHex)
 	var alice Conversation

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
-Package pbkdf2 implements the key derivation function PBKDF2 as defined in RFC
+// RFC 8018 (PKCS #5 v2.1).
-2898 / PKCS #5 v2.0.
+//
-
+// This package is a wrapper for the PBKDF2 implementation in the
-A key derivation function is useful when encrypting data based on a password
+// [crypto/pbkdf2] package. It is [frozen] and is not accepting new features.
-or any other not-fully-random data. It uses a pseudorandom function to derive
+//
-a secure encryption key based on the password.
+// [frozen]: https://go.dev/wiki/Frozen
-
-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
 
 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)
+	out, err := pbkdf2.Key(h, string(password), salt, iter, keyLen)
-	hashLen := prf.Size()
+	if err != nil {
-	numBlocks := (keyLen + hashLen - 1) / hashLen
+		// FIPS 140 enforcement, or an invalid key length.
-
+		panic(err)
-	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]
-			}
-		}
 	}
-	return dk[:keyLen]
+	return out
 }

pkcs12/pkcs12.go

@@ -4,12 +4,16 @@
 
 // Package pkcs12 implements some of PKCS#12.
 //
-// This implementation is distilled from https://tools.ietf.org/html/rfc7292
+// This implementation is distilled from [RFC 7292] and referenced documents.
-// and referenced documents. It is intended for decoding P12/PFX-stored
+// It is intended for decoding P12/PFX-stored certificates and keys for use
-// certificates and keys for use with the crypto/tls package.
+// with the crypto/tls package.
 //
-// This package is frozen. If it's missing functionality you need, consider
+// The pkcs12 package is [frozen] and is not accepting new features.
-// an alternative like software.sslmate.com/src/go-pkcs12.
+// If it's missing functionality you need, consider an alternative like
+// software.sslmate.com/src/go-pkcs12.
+//
+// [RFC 7292]: https://datatracker.ietf.org/doc/html/rfc7292
+// [frozen]: https://go.dev/wiki/Frozen
 package pkcs12
 
 import (

salsa20/salsa/hsalsa20.go

@@ -3,6 +3,10 @@
 // license that can be found in the LICENSE file.
 
 // Package salsa provides low-level access to functions in the Salsa family.
+//
+// Deprecated: this package exposes unsafe low-level operations. New applications
+// should consider using the AEAD construction in golang.org/x/crypto/chacha20poly1305
+// instead. Existing users should migrate to golang.org/x/crypto/salsa20.
 package salsa
 
 import "math/bits"

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) {

sha3/_asm/go.mod

@@ -1,15 +0,0 @@
-module sha3/_asm
-
-go 1.22
-
-require (
-	github.com/mmcloughlin/avo v0.6.0
-	golang.org/x/crypto v0.33.0
-)
-
-require (
-	golang.org/x/mod v0.19.0 // indirect
-	golang.org/x/sync v0.7.0 // indirect
-	golang.org/x/sys v0.30.0 // indirect
-	golang.org/x/tools v0.23.0 // indirect
-)

sha3/_asm/go.sum

@@ -1,12 +0,0 @@
-github.com/mmcloughlin/avo v0.6.0 h1:QH6FU8SKoTLaVs80GA8TJuLNkUYl4VokHKlPhVDg4YY=
-github.com/mmcloughlin/avo v0.6.0/go.mod h1:8CoAGaCSYXtCPR+8y18Y9aB/kxb8JSS6FRI7mSkvD+8=
-golang.org/x/crypto v0.33.0 h1:IOBPskki6Lysi0lo9qQvbxiQ+FvsCC/YWOecCHAixus=
-golang.org/x/crypto v0.33.0/go.mod h1:bVdXmD7IV/4GdElGPozy6U7lWdRXA4qyRVGJV57uQ5M=
-golang.org/x/mod v0.19.0 h1:fEdghXQSo20giMthA7cd28ZC+jts4amQ3YMXiP5oMQ8=
-golang.org/x/mod v0.19.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
-golang.org/x/sync v0.7.0 h1:YsImfSBoP9QPYL0xyKJPq0gcaJdG3rInoqxTWbfQu9M=
-golang.org/x/sync v0.7.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
-golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
-golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
-golang.org/x/tools v0.23.0 h1:SGsXPZ+2l4JsgaCKkx+FQ9YZ5XEtA1GZYuoDjenLjvg=
-golang.org/x/tools v0.23.0/go.mod h1:pnu6ufv6vQkll6szChhK3C3L/ruaIv5eBeztNG8wtsI=

sha3/_asm/keccakf_amd64_asm.go

@@ -1,438 +0,0 @@
-// Copyright 2024 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.
-
-// This code was translated into a form compatible with 6a from the public
-// domain sources at https://github.com/gvanas/KeccakCodePackage
-
-package main
-
-import (
-	. "github.com/mmcloughlin/avo/build"
-	. "github.com/mmcloughlin/avo/operand"
-	. "github.com/mmcloughlin/avo/reg"
-	_ "golang.org/x/crypto/sha3"
-)
-
-//go:generate go run . -out ../keccakf_amd64.s -pkg sha3
-
-// Round Constants for use in the ι step.
-var RoundConstants = [24]uint64{
-	0x0000000000000001,
-	0x0000000000008082,
-	0x800000000000808A,
-	0x8000000080008000,
-	0x000000000000808B,
-	0x0000000080000001,
-	0x8000000080008081,
-	0x8000000000008009,
-	0x000000000000008A,
-	0x0000000000000088,
-	0x0000000080008009,
-	0x000000008000000A,
-	0x000000008000808B,
-	0x800000000000008B,
-	0x8000000000008089,
-	0x8000000000008003,
-	0x8000000000008002,
-	0x8000000000000080,
-	0x000000000000800A,
-	0x800000008000000A,
-	0x8000000080008081,
-	0x8000000000008080,
-	0x0000000080000001,
-	0x8000000080008008,
-}
-
-var (
-	// Temporary registers
-	rT1 GPPhysical = RAX
-
-	// Round vars
-	rpState = Mem{Base: RDI}
-	rpStack = Mem{Base: RSP}
-
-	rDa = RBX
-	rDe = RCX
-	rDi = RDX
-	rDo = R8
-	rDu = R9
-
-	rBa = R10
-	rBe = R11
-	rBi = R12
-	rBo = R13
-	rBu = R14
-
-	rCa = RSI
-	rCe = RBP
-	rCi = rBi
-	rCo = rBo
-	rCu = R15
-)
-
-const (
-	_ba = iota * 8
-	_be
-	_bi
-	_bo
-	_bu
-	_ga
-	_ge
-	_gi
-	_go
-	_gu
-	_ka
-	_ke
-	_ki
-	_ko
-	_ku
-	_ma
-	_me
-	_mi
-	_mo
-	_mu
-	_sa
-	_se
-	_si
-	_so
-	_su
-)
-
-func main() {
-	Package("golang.org/x/crypto/sha3")
-	ConstraintExpr("amd64,!purego,gc")
-	keccakF1600()
-	Generate()
-}
-
-func MOVQ_RBI_RCE() { MOVQ(rBi, rCe) }
-func XORQ_RT1_RCA() { XORQ(rT1, rCa) }
-func XORQ_RT1_RCE() { XORQ(rT1, rCe) }
-func XORQ_RBA_RCU() { XORQ(rBa, rCu) }
-func XORQ_RBE_RCU() { XORQ(rBe, rCu) }
-func XORQ_RDU_RCU() { XORQ(rDu, rCu) }
-func XORQ_RDA_RCA() { XORQ(rDa, rCa) }
-func XORQ_RDE_RCE() { XORQ(rDe, rCe) }
-
-type ArgMacro func()
-
-func mKeccakRound(
-	iState, oState Mem,
-	rc U64,
-	B_RBI_RCE, G_RT1_RCA, G_RT1_RCE, G_RBA_RCU,
-	K_RT1_RCA, K_RT1_RCE, K_RBA_RCU, M_RT1_RCA,
-	M_RT1_RCE, M_RBE_RCU, S_RDU_RCU, S_RDA_RCA,
-	S_RDE_RCE ArgMacro,
-) {
-	Comment("Prepare round")
-	MOVQ(rCe, rDa)
-	ROLQ(Imm(1), rDa)
-
-	MOVQ(iState.Offset(_bi), rCi)
-	XORQ(iState.Offset(_gi), rDi)
-	XORQ(rCu, rDa)
-	XORQ(iState.Offset(_ki), rCi)
-	XORQ(iState.Offset(_mi), rDi)
-	XORQ(rDi, rCi)
-
-	MOVQ(rCi, rDe)
-	ROLQ(Imm(1), rDe)
-
-	MOVQ(iState.Offset(_bo), rCo)
-	XORQ(iState.Offset(_go), rDo)
-	XORQ(rCa, rDe)
-	XORQ(iState.Offset(_ko), rCo)
-	XORQ(iState.Offset(_mo), rDo)
-	XORQ(rDo, rCo)
-
-	MOVQ(rCo, rDi)
-	ROLQ(Imm(1), rDi)
-
-	MOVQ(rCu, rDo)
-	XORQ(rCe, rDi)
-	ROLQ(Imm(1), rDo)
-
-	MOVQ(rCa, rDu)
-	XORQ(rCi, rDo)
-	ROLQ(Imm(1), rDu)
-
-	Comment("Result b")
-	MOVQ(iState.Offset(_ba), rBa)
-	MOVQ(iState.Offset(_ge), rBe)
-	XORQ(rCo, rDu)
-	MOVQ(iState.Offset(_ki), rBi)
-	MOVQ(iState.Offset(_mo), rBo)
-	MOVQ(iState.Offset(_su), rBu)
-	XORQ(rDe, rBe)
-	ROLQ(Imm(44), rBe)
-	XORQ(rDi, rBi)
-	XORQ(rDa, rBa)
-	ROLQ(Imm(43), rBi)
-
-	MOVQ(rBe, rCa)
-	MOVQ(rc, rT1)
-	ORQ(rBi, rCa)
-	XORQ(rBa, rT1)
-	XORQ(rT1, rCa)
-	MOVQ(rCa, oState.Offset(_ba))
-
-	XORQ(rDu, rBu)
-	ROLQ(Imm(14), rBu)
-	MOVQ(rBa, rCu)
-	ANDQ(rBe, rCu)
-	XORQ(rBu, rCu)
-	MOVQ(rCu, oState.Offset(_bu))
-
-	XORQ(rDo, rBo)
-	ROLQ(Imm(21), rBo)
-	MOVQ(rBo, rT1)
-	ANDQ(rBu, rT1)
-	XORQ(rBi, rT1)
-	MOVQ(rT1, oState.Offset(_bi))
-
-	NOTQ(rBi)
-	ORQ(rBa, rBu)
-	ORQ(rBo, rBi)
-	XORQ(rBo, rBu)
-	XORQ(rBe, rBi)
-	MOVQ(rBu, oState.Offset(_bo))
-	MOVQ(rBi, oState.Offset(_be))
-	B_RBI_RCE()
-
-	Comment("Result g")
-	MOVQ(iState.Offset(_gu), rBe)
-	XORQ(rDu, rBe)
-	MOVQ(iState.Offset(_ka), rBi)
-	ROLQ(Imm(20), rBe)
-	XORQ(rDa, rBi)
-	ROLQ(Imm(3), rBi)
-	MOVQ(iState.Offset(_bo), rBa)
-	MOVQ(rBe, rT1)
-	ORQ(rBi, rT1)
-	XORQ(rDo, rBa)
-	MOVQ(iState.Offset(_me), rBo)
-	MOVQ(iState.Offset(_si), rBu)
-	ROLQ(Imm(28), rBa)
-	XORQ(rBa, rT1)
-	MOVQ(rT1, oState.Offset(_ga))
-	G_RT1_RCA()
-
-	XORQ(rDe, rBo)
-	ROLQ(Imm(45), rBo)
-	MOVQ(rBi, rT1)
-	ANDQ(rBo, rT1)
-	XORQ(rBe, rT1)
-	MOVQ(rT1, oState.Offset(_ge))
-	G_RT1_RCE()
-
-	XORQ(rDi, rBu)
-	ROLQ(Imm(61), rBu)
-	MOVQ(rBu, rT1)
-	ORQ(rBa, rT1)
-	XORQ(rBo, rT1)
-	MOVQ(rT1, oState.Offset(_go))
-
-	ANDQ(rBe, rBa)
-	XORQ(rBu, rBa)
-	MOVQ(rBa, oState.Offset(_gu))
-	NOTQ(rBu)
-	G_RBA_RCU()
-
-	ORQ(rBu, rBo)
-	XORQ(rBi, rBo)
-	MOVQ(rBo, oState.Offset(_gi))
-
-	Comment("Result k")
-	MOVQ(iState.Offset(_be), rBa)
-	MOVQ(iState.Offset(_gi), rBe)
-	MOVQ(iState.Offset(_ko), rBi)
-	MOVQ(iState.Offset(_mu), rBo)
-	MOVQ(iState.Offset(_sa), rBu)
-	XORQ(rDi, rBe)
-	ROLQ(Imm(6), rBe)
-	XORQ(rDo, rBi)
-	ROLQ(Imm(25), rBi)
-	MOVQ(rBe, rT1)
-	ORQ(rBi, rT1)
-	XORQ(rDe, rBa)
-	ROLQ(Imm(1), rBa)
-	XORQ(rBa, rT1)
-	MOVQ(rT1, oState.Offset(_ka))
-	K_RT1_RCA()
-
-	XORQ(rDu, rBo)
-	ROLQ(Imm(8), rBo)
-	MOVQ(rBi, rT1)
-	ANDQ(rBo, rT1)
-	XORQ(rBe, rT1)
-	MOVQ(rT1, oState.Offset(_ke))
-	K_RT1_RCE()
-
-	XORQ(rDa, rBu)
-	ROLQ(Imm(18), rBu)
-	NOTQ(rBo)
-	MOVQ(rBo, rT1)
-	ANDQ(rBu, rT1)
-	XORQ(rBi, rT1)
-	MOVQ(rT1, oState.Offset(_ki))
-
-	MOVQ(rBu, rT1)
-	ORQ(rBa, rT1)
-	XORQ(rBo, rT1)
-	MOVQ(rT1, oState.Offset(_ko))
-
-	ANDQ(rBe, rBa)
-	XORQ(rBu, rBa)
-	MOVQ(rBa, oState.Offset(_ku))
-	K_RBA_RCU()
-
-	Comment("Result m")
-	MOVQ(iState.Offset(_ga), rBe)
-	XORQ(rDa, rBe)
-	MOVQ(iState.Offset(_ke), rBi)
-	ROLQ(Imm(36), rBe)
-	XORQ(rDe, rBi)
-	MOVQ(iState.Offset(_bu), rBa)
-	ROLQ(Imm(10), rBi)
-	MOVQ(rBe, rT1)
-	MOVQ(iState.Offset(_mi), rBo)
-	ANDQ(rBi, rT1)
-	XORQ(rDu, rBa)
-	MOVQ(iState.Offset(_so), rBu)
-	ROLQ(Imm(27), rBa)
-	XORQ(rBa, rT1)
-	MOVQ(rT1, oState.Offset(_ma))
-	M_RT1_RCA()
-
-	XORQ(rDi, rBo)
-	ROLQ(Imm(15), rBo)
-	MOVQ(rBi, rT1)
-	ORQ(rBo, rT1)
-	XORQ(rBe, rT1)
-	MOVQ(rT1, oState.Offset(_me))
-	M_RT1_RCE()
-
-	XORQ(rDo, rBu)
-	ROLQ(Imm(56), rBu)
-	NOTQ(rBo)
-	MOVQ(rBo, rT1)
-	ORQ(rBu, rT1)
-	XORQ(rBi, rT1)
-	MOVQ(rT1, oState.Offset(_mi))
-
-	ORQ(rBa, rBe)
-	XORQ(rBu, rBe)
-	MOVQ(rBe, oState.Offset(_mu))
-
-	ANDQ(rBa, rBu)
-	XORQ(rBo, rBu)
-	MOVQ(rBu, oState.Offset(_mo))
-	M_RBE_RCU()
-
-	Comment("Result s")
-	MOVQ(iState.Offset(_bi), rBa)
-	MOVQ(iState.Offset(_go), rBe)
-	MOVQ(iState.Offset(_ku), rBi)
-	XORQ(rDi, rBa)
-	MOVQ(iState.Offset(_ma), rBo)
-	ROLQ(Imm(62), rBa)
-	XORQ(rDo, rBe)
-	MOVQ(iState.Offset(_se), rBu)
-	ROLQ(Imm(55), rBe)
-
-	XORQ(rDu, rBi)
-	MOVQ(rBa, rDu)
-	XORQ(rDe, rBu)
-	ROLQ(Imm(2), rBu)
-	ANDQ(rBe, rDu)
-	XORQ(rBu, rDu)
-	MOVQ(rDu, oState.Offset(_su))
-
-	ROLQ(Imm(39), rBi)
-	S_RDU_RCU()
-	NOTQ(rBe)
-	XORQ(rDa, rBo)
-	MOVQ(rBe, rDa)
-	ANDQ(rBi, rDa)
-	XORQ(rBa, rDa)
-	MOVQ(rDa, oState.Offset(_sa))
-	S_RDA_RCA()
-
-	ROLQ(Imm(41), rBo)
-	MOVQ(rBi, rDe)
-	ORQ(rBo, rDe)
-	XORQ(rBe, rDe)
-	MOVQ(rDe, oState.Offset(_se))
-	S_RDE_RCE()
-
-	MOVQ(rBo, rDi)
-	MOVQ(rBu, rDo)
-	ANDQ(rBu, rDi)
-	ORQ(rBa, rDo)
-	XORQ(rBi, rDi)
-	XORQ(rBo, rDo)
-	MOVQ(rDi, oState.Offset(_si))
-	MOVQ(rDo, oState.Offset(_so))
-}
-
-// keccakF1600 applies the Keccak permutation to a 1600b-wide
-// state represented as a slice of 25 uint64s.
-func keccakF1600() {
-	Implement("keccakF1600")
-	AllocLocal(200)
-
-	Load(Param("a"), rpState.Base)
-
-	Comment("Convert the user state into an internal state")
-	NOTQ(rpState.Offset(_be))
-	NOTQ(rpState.Offset(_bi))
-	NOTQ(rpState.Offset(_go))
-	NOTQ(rpState.Offset(_ki))
-	NOTQ(rpState.Offset(_mi))
-	NOTQ(rpState.Offset(_sa))
-
-	Comment("Execute the KeccakF permutation")
-	MOVQ(rpState.Offset(_ba), rCa)
-	MOVQ(rpState.Offset(_be), rCe)
-	MOVQ(rpState.Offset(_bu), rCu)
-
-	XORQ(rpState.Offset(_ga), rCa)
-	XORQ(rpState.Offset(_ge), rCe)
-	XORQ(rpState.Offset(_gu), rCu)
-
-	XORQ(rpState.Offset(_ka), rCa)
-	XORQ(rpState.Offset(_ke), rCe)
-	XORQ(rpState.Offset(_ku), rCu)
-
-	XORQ(rpState.Offset(_ma), rCa)
-	XORQ(rpState.Offset(_me), rCe)
-	XORQ(rpState.Offset(_mu), rCu)
-
-	XORQ(rpState.Offset(_sa), rCa)
-	XORQ(rpState.Offset(_se), rCe)
-	MOVQ(rpState.Offset(_si), rDi)
-	MOVQ(rpState.Offset(_so), rDo)
-	XORQ(rpState.Offset(_su), rCu)
-
-	for i, rc := range RoundConstants[:len(RoundConstants)-1] {
-		var iState, oState Mem
-		if i%2 == 0 {
-			iState, oState = rpState, rpStack
-		} else {
-			iState, oState = rpStack, rpState
-		}
-		mKeccakRound(iState, oState, U64(rc), MOVQ_RBI_RCE, XORQ_RT1_RCA, XORQ_RT1_RCE, XORQ_RBA_RCU, XORQ_RT1_RCA, XORQ_RT1_RCE, XORQ_RBA_RCU, XORQ_RT1_RCA, XORQ_RT1_RCE, XORQ_RBE_RCU, XORQ_RDU_RCU, XORQ_RDA_RCA, XORQ_RDE_RCE)
-	}
-	mKeccakRound(rpStack, rpState, U64(RoundConstants[len(RoundConstants)-1]), NOP, NOP, NOP, NOP, NOP, NOP, NOP, NOP, NOP, NOP, NOP, NOP, NOP)
-
-	Comment("Revert the internal state to the user state")
-	NOTQ(rpState.Offset(_be))
-	NOTQ(rpState.Offset(_bi))
-	NOTQ(rpState.Offset(_go))
-	NOTQ(rpState.Offset(_ki))
-	NOTQ(rpState.Offset(_mi))
-	NOTQ(rpState.Offset(_sa))
-
-	RET()
-}

sha3/allocations_test.go

@@ -1,61 +0,0 @@
-// Copyright 2023 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 !noopt
-
-package sha3_test
-
-import (
-	"runtime"
-	"testing"
-
-	"golang.org/x/crypto/sha3"
-)
-
-var sink byte
-
-func TestAllocations(t *testing.T) {
-	want := 0.0
-
-	if runtime.GOARCH == "s390x" {
-		// On s390x the returned hash.Hash is conditional so it escapes.
-		want = 3.0
-	}
-
-	t.Run("New", func(t *testing.T) {
-		if allocs := testing.AllocsPerRun(10, func() {
-			h := sha3.New256()
-			b := []byte("ABC")
-			h.Write(b)
-			out := make([]byte, 0, 32)
-			out = h.Sum(out)
-			sink ^= out[0]
-		}); allocs > want {
-			t.Errorf("expected zero allocations, got %0.1f", allocs)
-		}
-	})
-	t.Run("NewShake", func(t *testing.T) {
-		if allocs := testing.AllocsPerRun(10, func() {
-			h := sha3.NewShake128()
-			b := []byte("ABC")
-			h.Write(b)
-			out := make([]byte, 0, 32)
-			out = h.Sum(out)
-			sink ^= out[0]
-			h.Read(out)
-			sink ^= out[0]
-		}); allocs > want {
-			t.Errorf("expected zero allocations, got %0.1f", allocs)
-		}
-	})
-	t.Run("Sum", func(t *testing.T) {
-		if allocs := testing.AllocsPerRun(10, func() {
-			b := []byte("ABC")
-			out := sha3.Sum256(b)
-			sink ^= out[0]
-		}); allocs > want {
-			t.Errorf("expected zero allocations, got %0.1f", allocs)
-		}
-	})
-}

sha3/doc.go

@@ -1,66 +0,0 @@
-// Copyright 2014 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 sha3 implements the SHA-3 fixed-output-length hash functions and
-// the SHAKE variable-output-length hash functions defined by FIPS-202.
-//
-// All types in this package also implement [encoding.BinaryMarshaler],
-// [encoding.BinaryAppender] and [encoding.BinaryUnmarshaler] to marshal and
-// unmarshal the internal state of the hash.
-//
-// Both types of hash function use the "sponge" construction and the Keccak
-// permutation. For a detailed specification see http://keccak.noekeon.org/
-//
-// # Guidance
-//
-// If you aren't sure what function you need, use SHAKE256 with at least 64
-// bytes of output. The SHAKE instances are faster than the SHA3 instances;
-// the latter have to allocate memory to conform to the hash.Hash interface.
-//
-// If you need a secret-key MAC (message authentication code), prepend the
-// secret key to the input, hash with SHAKE256 and read at least 32 bytes of
-// output.
-//
-// # Security strengths
-//
-// The SHA3-x (x equals 224, 256, 384, or 512) functions have a security
-// strength against preimage attacks of x bits. Since they only produce "x"
-// bits of output, their collision-resistance is only "x/2" bits.
-//
-// The SHAKE-256 and -128 functions have a generic security strength of 256 and
-// 128 bits against all attacks, provided that at least 2x bits of their output
-// is used.  Requesting more than 64 or 32 bytes of output, respectively, does
-// not increase the collision-resistance of the SHAKE functions.
-//
-// # The sponge construction
-//
-// A sponge builds a pseudo-random function from a public pseudo-random
-// permutation, by applying the permutation to a state of "rate + capacity"
-// bytes, but hiding "capacity" of the bytes.
-//
-// A sponge starts out with a zero state. To hash an input using a sponge, up
-// to "rate" bytes of the input are XORed into the sponge's state. The sponge
-// is then "full" and the permutation is applied to "empty" it. This process is
-// repeated until all the input has been "absorbed". The input is then padded.
-// The digest is "squeezed" from the sponge in the same way, except that output
-// is copied out instead of input being XORed in.
-//
-// A sponge is parameterized by its generic security strength, which is equal
-// to half its capacity; capacity + rate is equal to the permutation's width.
-// Since the KeccakF-1600 permutation is 1600 bits (200 bytes) wide, this means
-// that the security strength of a sponge instance is equal to (1600 - bitrate) / 2.
-//
-// # Recommendations
-//
-// The SHAKE functions are recommended for most new uses. They can produce
-// output of arbitrary length. SHAKE256, with an output length of at least
-// 64 bytes, provides 256-bit security against all attacks.  The Keccak team
-// recommends it for most applications upgrading from SHA2-512. (NIST chose a
-// much stronger, but much slower, sponge instance for SHA3-512.)
-//
-// The SHA-3 functions are "drop-in" replacements for the SHA-2 functions.
-// They produce output of the same length, with the same security strengths
-// against all attacks. This means, in particular, that SHA3-256 only has
-// 128-bit collision resistance, because its output length is 32 bytes.
-package sha3

sha3/hashes.go

@@ -2,127 +2,94 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Package sha3 implements the SHA-3 hash algorithms and the SHAKE extendable
+// output functions defined in FIPS 202.
+//
+// Most of this package is a wrapper around the crypto/sha3 package in the
+// standard library. The only exception is the legacy Keccak hash functions.
 package sha3
 
-// This file provides functions for creating instances of the SHA-3
-// and SHAKE hash functions, as well as utility functions for hashing
-// bytes.
-
 import (
-	"crypto"
+	"crypto/sha3"
 	"hash"
 )
 
 // New224 creates a new SHA3-224 hash.
 // Its generic security strength is 224 bits against preimage attacks,
 // and 112 bits against collision attacks.
+//
+// It is a wrapper for the [sha3.New224] function in the standard library.
+//
+//go:fix inline
 func New224() hash.Hash {
-	return new224()
+	return sha3.New224()
 }
 
 // New256 creates a new SHA3-256 hash.
 // Its generic security strength is 256 bits against preimage attacks,
 // and 128 bits against collision attacks.
+//
+// It is a wrapper for the [sha3.New256] function in the standard library.
+//
+//go:fix inline
 func New256() hash.Hash {
-	return new256()
+	return sha3.New256()
 }
 
 // New384 creates a new SHA3-384 hash.
 // Its generic security strength is 384 bits against preimage attacks,
 // and 192 bits against collision attacks.
+//
+// It is a wrapper for the [sha3.New384] function in the standard library.
+//
+//go:fix inline
 func New384() hash.Hash {
-	return new384()
+	return sha3.New384()
 }
 
 // New512 creates a new SHA3-512 hash.
 // Its generic security strength is 512 bits against preimage attacks,
 // and 256 bits against collision attacks.
+//
+// It is a wrapper for the [sha3.New512] function in the standard library.
+//
+//go:fix inline
 func New512() hash.Hash {
-	return new512()
+	return sha3.New512()
-}
-
-func init() {
-	crypto.RegisterHash(crypto.SHA3_224, New224)
-	crypto.RegisterHash(crypto.SHA3_256, New256)
-	crypto.RegisterHash(crypto.SHA3_384, New384)
-	crypto.RegisterHash(crypto.SHA3_512, New512)
-}
-
-const (
-	dsbyteSHA3   = 0b00000110
-	dsbyteKeccak = 0b00000001
-	dsbyteShake  = 0b00011111
-	dsbyteCShake = 0b00000100
-
-	// rateK[c] is the rate in bytes for Keccak[c] where c is the capacity in
-	// bits. Given the sponge size is 1600 bits, the rate is 1600 - c bits.
-	rateK256  = (1600 - 256) / 8
-	rateK448  = (1600 - 448) / 8
-	rateK512  = (1600 - 512) / 8
-	rateK768  = (1600 - 768) / 8
-	rateK1024 = (1600 - 1024) / 8
-)
-
-func new224Generic() *state {
-	return &state{rate: rateK448, outputLen: 28, dsbyte: dsbyteSHA3}
-}
-
-func new256Generic() *state {
-	return &state{rate: rateK512, outputLen: 32, dsbyte: dsbyteSHA3}
-}
-
-func new384Generic() *state {
-	return &state{rate: rateK768, outputLen: 48, dsbyte: dsbyteSHA3}
-}
-
-func new512Generic() *state {
-	return &state{rate: rateK1024, outputLen: 64, dsbyte: dsbyteSHA3}
-}
-
-// NewLegacyKeccak256 creates a new Keccak-256 hash.
-//
-// Only use this function if you require compatibility with an existing cryptosystem
-// that uses non-standard padding. All other users should use New256 instead.
-func NewLegacyKeccak256() hash.Hash {
-	return &state{rate: rateK512, outputLen: 32, dsbyte: dsbyteKeccak}
-}
-
-// NewLegacyKeccak512 creates a new Keccak-512 hash.
-//
-// Only use this function if you require compatibility with an existing cryptosystem
-// that uses non-standard padding. All other users should use New512 instead.
-func NewLegacyKeccak512() hash.Hash {
-	return &state{rate: rateK1024, outputLen: 64, dsbyte: dsbyteKeccak}
 }
 
 // Sum224 returns the SHA3-224 digest of the data.
-func Sum224(data []byte) (digest [28]byte) {
+//
-	h := New224()
+// It is a wrapper for the [sha3.Sum224] function in the standard library.
-	h.Write(data)
+//
-	h.Sum(digest[:0])
+//go:fix inline
-	return
+func Sum224(data []byte) [28]byte {
+	return sha3.Sum224(data)
 }
 
 // Sum256 returns the SHA3-256 digest of the data.
-func Sum256(data []byte) (digest [32]byte) {
+//
-	h := New256()
+// It is a wrapper for the [sha3.Sum256] function in the standard library.
-	h.Write(data)
+//
-	h.Sum(digest[:0])
+//go:fix inline
-	return
+func Sum256(data []byte) [32]byte {
+	return sha3.Sum256(data)
 }
 
 // Sum384 returns the SHA3-384 digest of the data.
-func Sum384(data []byte) (digest [48]byte) {
+//
-	h := New384()
+// It is a wrapper for the [sha3.Sum384] function in the standard library.
-	h.Write(data)
+//
-	h.Sum(digest[:0])
+//go:fix inline
-	return
+func Sum384(data []byte) [48]byte {
+	return sha3.Sum384(data)
 }
 
 // Sum512 returns the SHA3-512 digest of the data.
-func Sum512(data []byte) (digest [64]byte) {
+//
-	h := New512()
+// It is a wrapper for the [sha3.Sum512] function in the standard library.
-	h.Write(data)
+//
-	h.Sum(digest[:0])
+//go:fix inline
-	return
+func Sum512(data []byte) [64]byte {
+	return sha3.Sum512(data)
 }

sha3/hashes_noasm.go

@@ -1,23 +0,0 @@
-// Copyright 2023 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 || !s390x
-
-package sha3
-
-func new224() *state {
-	return new224Generic()
-}
-
-func new256() *state {
-	return new256Generic()
-}
-
-func new384() *state {
-	return new384Generic()
-}
-
-func new512() *state {
-	return new512Generic()
-}

sha3/keccakf_amd64.go

@@ -1,13 +0,0 @@
-// Copyright 2015 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 amd64 && !purego && gc
-
-package sha3
-
-// This function is implemented in keccakf_amd64.s.
-
-//go:noescape
-
-func keccakF1600(a *[25]uint64)

sha3/legacy_hash.go

@@ -4,15 +4,46 @@
 
 package sha3
 
+// This implementation is only used for NewLegacyKeccak256 and
+// NewLegacyKeccak512, which are not implemented by crypto/sha3.
+// All other functions in this package are wrappers around crypto/sha3.
+
 import (
 	"crypto/subtle"
 	"encoding/binary"
 	"errors"
+	"hash"
 	"unsafe"
 
 	"golang.org/x/sys/cpu"
 )
 
+const (
+	dsbyteKeccak = 0b00000001
+
+	// rateK[c] is the rate in bytes for Keccak[c] where c is the capacity in
+	// bits. Given the sponge size is 1600 bits, the rate is 1600 - c bits.
+	rateK256  = (1600 - 256) / 8
+	rateK512  = (1600 - 512) / 8
+	rateK1024 = (1600 - 1024) / 8
+)
+
+// NewLegacyKeccak256 creates a new Keccak-256 hash.
+//
+// Only use this function if you require compatibility with an existing cryptosystem
+// that uses non-standard padding. All other users should use New256 instead.
+func NewLegacyKeccak256() hash.Hash {
+	return &state{rate: rateK512, outputLen: 32, dsbyte: dsbyteKeccak}
+}
+
+// NewLegacyKeccak512 creates a new Keccak-512 hash.
+//
+// Only use this function if you require compatibility with an existing cryptosystem
+// that uses non-standard padding. All other users should use New512 instead.
+func NewLegacyKeccak512() hash.Hash {
+	return &state{rate: rateK1024, outputLen: 64, dsbyte: dsbyteKeccak}
+}
+
 // spongeDirection indicates the direction bytes are flowing through the sponge.
 type spongeDirection int
 
@@ -173,12 +204,9 @@ func (d *state) Sum(in []byte) []byte {
 }
 
 const (
-	magicSHA3   = "sha\x08"
-	magicShake  = "sha\x09"
-	magicCShake = "sha\x0a"
 	magicKeccak = "sha\x0b"
 	// magic || rate || main state || n || sponge direction
-	marshaledSize = len(magicSHA3) + 1 + 200 + 1 + 1
+	marshaledSize = len(magicKeccak) + 1 + 200 + 1 + 1
 )
 
 func (d *state) MarshalBinary() ([]byte, error) {
@@ -187,12 +215,6 @@ func (d *state) MarshalBinary() ([]byte, error) {
 
 func (d *state) AppendBinary(b []byte) ([]byte, error) {
 	switch d.dsbyte {
-	case dsbyteSHA3:
-		b = append(b, magicSHA3...)
-	case dsbyteShake:
-		b = append(b, magicShake...)
-	case dsbyteCShake:
-		b = append(b, magicCShake...)
 	case dsbyteKeccak:
 		b = append(b, magicKeccak...)
 	default:
@@ -210,12 +232,9 @@ func (d *state) UnmarshalBinary(b []byte) error {
 		return errors.New("sha3: invalid hash state")
 	}
 
-	magic := string(b[:len(magicSHA3)])
+	magic := string(b[:len(magicKeccak)])
-	b = b[len(magicSHA3):]
+	b = b[len(magicKeccak):]
 	switch {
-	case magic == magicSHA3 && d.dsbyte == dsbyteSHA3:
-	case magic == magicShake && d.dsbyte == dsbyteShake:
-	case magic == magicCShake && d.dsbyte == dsbyteCShake:
 	case magic == magicKeccak && d.dsbyte == dsbyteKeccak:
 	default:
 		return errors.New("sha3: invalid hash state identifier")

sha3/legacy_keccakf.go

@@ -2,10 +2,12 @@
 // 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
-
 package sha3
 
+// This implementation is only used for NewLegacyKeccak256 and
+// NewLegacyKeccak512, which are not implemented by crypto/sha3.
+// All other functions in this package are wrappers around crypto/sha3.
+
 import "math/bits"
 
 // rc stores the round constants for use in the ι step.

sha3/sha3_s390x.go

@@ -1,303 +0,0 @@
-// Copyright 2017 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 sha3
-
-// This file contains code for using the 'compute intermediate
-// message digest' (KIMD) and 'compute last message digest' (KLMD)
-// instructions to compute SHA-3 and SHAKE hashes on IBM Z.
-
-import (
-	"hash"
-
-	"golang.org/x/sys/cpu"
-)
-
-// codes represent 7-bit KIMD/KLMD function codes as defined in
-// the Principles of Operation.
-type code uint64
-
-const (
-	// function codes for KIMD/KLMD
-	sha3_224  code = 32
-	sha3_256       = 33
-	sha3_384       = 34
-	sha3_512       = 35
-	shake_128      = 36
-	shake_256      = 37
-	nopad          = 0x100
-)
-
-// kimd is a wrapper for the 'compute intermediate message digest' instruction.
-// src must be a multiple of the rate for the given function code.
-//
-//go:noescape
-func kimd(function code, chain *[200]byte, src []byte)
-
-// klmd is a wrapper for the 'compute last message digest' instruction.
-// src padding is handled by the instruction.
-//
-//go:noescape
-func klmd(function code, chain *[200]byte, dst, src []byte)
-
-type asmState struct {
-	a         [200]byte       // 1600 bit state
-	buf       []byte          // care must be taken to ensure cap(buf) is a multiple of rate
-	rate      int             // equivalent to block size
-	storage   [3072]byte      // underlying storage for buf
-	outputLen int             // output length for full security
-	function  code            // KIMD/KLMD function code
-	state     spongeDirection // whether the sponge is absorbing or squeezing
-}
-
-func newAsmState(function code) *asmState {
-	var s asmState
-	s.function = function
-	switch function {
-	case sha3_224:
-		s.rate = 144
-		s.outputLen = 28
-	case sha3_256:
-		s.rate = 136
-		s.outputLen = 32
-	case sha3_384:
-		s.rate = 104
-		s.outputLen = 48
-	case sha3_512:
-		s.rate = 72
-		s.outputLen = 64
-	case shake_128:
-		s.rate = 168
-		s.outputLen = 32
-	case shake_256:
-		s.rate = 136
-		s.outputLen = 64
-	default:
-		panic("sha3: unrecognized function code")
-	}
-
-	// limit s.buf size to a multiple of s.rate
-	s.resetBuf()
-	return &s
-}
-
-func (s *asmState) clone() *asmState {
-	c := *s
-	c.buf = c.storage[:len(s.buf):cap(s.buf)]
-	return &c
-}
-
-// copyIntoBuf copies b into buf. It will panic if there is not enough space to
-// store all of b.
-func (s *asmState) copyIntoBuf(b []byte) {
-	bufLen := len(s.buf)
-	s.buf = s.buf[:len(s.buf)+len(b)]
-	copy(s.buf[bufLen:], b)
-}
-
-// resetBuf points buf at storage, sets the length to 0 and sets cap to be a
-// multiple of the rate.
-func (s *asmState) resetBuf() {
-	max := (cap(s.storage) / s.rate) * s.rate
-	s.buf = s.storage[:0:max]
-}
-
-// Write (via the embedded io.Writer interface) adds more data to the running hash.
-// It never returns an error.
-func (s *asmState) Write(b []byte) (int, error) {
-	if s.state != spongeAbsorbing {
-		panic("sha3: Write after Read")
-	}
-	length := len(b)
-	for len(b) > 0 {
-		if len(s.buf) == 0 && len(b) >= cap(s.buf) {
-			// Hash the data directly and push any remaining bytes
-			// into the buffer.
-			remainder := len(b) % s.rate
-			kimd(s.function, &s.a, b[:len(b)-remainder])
-			if remainder != 0 {
-				s.copyIntoBuf(b[len(b)-remainder:])
-			}
-			return length, nil
-		}
-
-		if len(s.buf) == cap(s.buf) {
-			// flush the buffer
-			kimd(s.function, &s.a, s.buf)
-			s.buf = s.buf[:0]
-		}
-
-		// copy as much as we can into the buffer
-		n := len(b)
-		if len(b) > cap(s.buf)-len(s.buf) {
-			n = cap(s.buf) - len(s.buf)
-		}
-		s.copyIntoBuf(b[:n])
-		b = b[n:]
-	}
-	return length, nil
-}
-
-// Read squeezes an arbitrary number of bytes from the sponge.
-func (s *asmState) Read(out []byte) (n int, err error) {
-	// The 'compute last message digest' instruction only stores the digest
-	// at the first operand (dst) for SHAKE functions.
-	if s.function != shake_128 && s.function != shake_256 {
-		panic("sha3: can only call Read for SHAKE functions")
-	}
-
-	n = len(out)
-
-	// need to pad if we were absorbing
-	if s.state == spongeAbsorbing {
-		s.state = spongeSqueezing
-
-		// write hash directly into out if possible
-		if len(out)%s.rate == 0 {
-			klmd(s.function, &s.a, out, s.buf) // len(out) may be 0
-			s.buf = s.buf[:0]
-			return
-		}
-
-		// write hash into buffer
-		max := cap(s.buf)
-		if max > len(out) {
-			max = (len(out)/s.rate)*s.rate + s.rate
-		}
-		klmd(s.function, &s.a, s.buf[:max], s.buf)
-		s.buf = s.buf[:max]
-	}
-
-	for len(out) > 0 {
-		// flush the buffer
-		if len(s.buf) != 0 {
-			c := copy(out, s.buf)
-			out = out[c:]
-			s.buf = s.buf[c:]
-			continue
-		}
-
-		// write hash directly into out if possible
-		if len(out)%s.rate == 0 {
-			klmd(s.function|nopad, &s.a, out, nil)
-			return
-		}
-
-		// write hash into buffer
-		s.resetBuf()
-		if cap(s.buf) > len(out) {
-			s.buf = s.buf[:(len(out)/s.rate)*s.rate+s.rate]
-		}
-		klmd(s.function|nopad, &s.a, s.buf, nil)
-	}
-	return
-}
-
-// Sum appends the current hash to b and returns the resulting slice.
-// It does not change the underlying hash state.
-func (s *asmState) Sum(b []byte) []byte {
-	if s.state != spongeAbsorbing {
-		panic("sha3: Sum after Read")
-	}
-
-	// Copy the state to preserve the original.
-	a := s.a
-
-	// Hash the buffer. Note that we don't clear it because we
-	// aren't updating the state.
-	switch s.function {
-	case sha3_224, sha3_256, sha3_384, sha3_512:
-		klmd(s.function, &a, nil, s.buf)
-		return append(b, a[:s.outputLen]...)
-	case shake_128, shake_256:
-		d := make([]byte, s.outputLen, 64)
-		klmd(s.function, &a, d, s.buf)
-		return append(b, d[:s.outputLen]...)
-	default:
-		panic("sha3: unknown function")
-	}
-}
-
-// Reset resets the Hash to its initial state.
-func (s *asmState) Reset() {
-	for i := range s.a {
-		s.a[i] = 0
-	}
-	s.resetBuf()
-	s.state = spongeAbsorbing
-}
-
-// Size returns the number of bytes Sum will return.
-func (s *asmState) Size() int {
-	return s.outputLen
-}
-
-// BlockSize returns the hash's underlying block size.
-// The Write method must be able to accept any amount
-// of data, but it may operate more efficiently if all writes
-// are a multiple of the block size.
-func (s *asmState) BlockSize() int {
-	return s.rate
-}
-
-// Clone returns a copy of the ShakeHash in its current state.
-func (s *asmState) Clone() ShakeHash {
-	return s.clone()
-}
-
-// new224 returns an assembly implementation of SHA3-224 if available,
-// otherwise it returns a generic implementation.
-func new224() hash.Hash {
-	if cpu.S390X.HasSHA3 {
-		return newAsmState(sha3_224)
-	}
-	return new224Generic()
-}
-
-// new256 returns an assembly implementation of SHA3-256 if available,
-// otherwise it returns a generic implementation.
-func new256() hash.Hash {
-	if cpu.S390X.HasSHA3 {
-		return newAsmState(sha3_256)
-	}
-	return new256Generic()
-}
-
-// new384 returns an assembly implementation of SHA3-384 if available,
-// otherwise it returns a generic implementation.
-func new384() hash.Hash {
-	if cpu.S390X.HasSHA3 {
-		return newAsmState(sha3_384)
-	}
-	return new384Generic()
-}
-
-// new512 returns an assembly implementation of SHA3-512 if available,
-// otherwise it returns a generic implementation.
-func new512() hash.Hash {
-	if cpu.S390X.HasSHA3 {
-		return newAsmState(sha3_512)
-	}
-	return new512Generic()
-}
-
-// newShake128 returns an assembly implementation of SHAKE-128 if available,
-// otherwise it returns a generic implementation.
-func newShake128() ShakeHash {
-	if cpu.S390X.HasSHA3 {
-		return newAsmState(shake_128)
-	}
-	return newShake128Generic()
-}
-
-// newShake256 returns an assembly implementation of SHAKE-256 if available,
-// otherwise it returns a generic implementation.
-func newShake256() ShakeHash {
-	if cpu.S390X.HasSHA3 {
-		return newAsmState(shake_256)
-	}
-	return newShake256Generic()
-}

sha3/sha3_s390x.s

@@ -1,33 +0,0 @@
-// Copyright 2017 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
-
-#include "textflag.h"
-
-// func kimd(function code, chain *[200]byte, src []byte)
-TEXT ·kimd(SB), NOFRAME|NOSPLIT, $0-40
-	MOVD function+0(FP), R0
-	MOVD chain+8(FP), R1
-	LMG  src+16(FP), R2, R3 // R2=base, R3=len
-
-continue:
-	WORD $0xB93E0002 // KIMD --, R2
-	BVS  continue    // continue if interrupted
-	MOVD $0, R0      // reset R0 for pre-go1.8 compilers
-	RET
-
-// func klmd(function code, chain *[200]byte, dst, src []byte)
-TEXT ·klmd(SB), NOFRAME|NOSPLIT, $0-64
-	// TODO: SHAKE support
-	MOVD function+0(FP), R0
-	MOVD chain+8(FP), R1
-	LMG  dst+16(FP), R2, R3 // R2=base, R3=len
-	LMG  src+40(FP), R4, R5 // R4=base, R5=len
-
-continue:
-	WORD $0xB93F0024 // KLMD R2, R4
-	BVS  continue    // continue if interrupted
-	MOVD $0, R0      // reset R0 for pre-go1.8 compilers
-	RET

sha3/sha3_test.go

@@ -16,7 +16,6 @@ import (
 	"encoding"
 	"encoding/hex"
 	"encoding/json"
-	"fmt"
 	"hash"
 	"io"
 	"math/rand"
@@ -523,124 +522,3 @@ func testMarshalUnmarshal(t *testing.T, h hash.Hash) {
 		t.Errorf("got %x, want %x", got, want)
 	}
 }
-
-// BenchmarkPermutationFunction measures the speed of the permutation function
-// with no input data.
-func BenchmarkPermutationFunction(b *testing.B) {
-	b.SetBytes(int64(200))
-	var lanes [25]uint64
-	for i := 0; i < b.N; i++ {
-		keccakF1600(&lanes)
-	}
-}
-
-// benchmarkHash tests the speed to hash num buffers of buflen each.
-func benchmarkHash(b *testing.B, h hash.Hash, size, num int) {
-	b.StopTimer()
-	h.Reset()
-	data := sequentialBytes(size)
-	b.SetBytes(int64(size * num))
-	b.StartTimer()
-
-	var state []byte
-	for i := 0; i < b.N; i++ {
-		for j := 0; j < num; j++ {
-			h.Write(data)
-		}
-		state = h.Sum(state[:0])
-	}
-	b.StopTimer()
-	h.Reset()
-}
-
-// benchmarkShake is specialized to the Shake instances, which don't
-// require a copy on reading output.
-func benchmarkShake(b *testing.B, h ShakeHash, size, num int) {
-	b.StopTimer()
-	h.Reset()
-	data := sequentialBytes(size)
-	d := make([]byte, 32)
-
-	b.SetBytes(int64(size * num))
-	b.StartTimer()
-
-	for i := 0; i < b.N; i++ {
-		h.Reset()
-		for j := 0; j < num; j++ {
-			h.Write(data)
-		}
-		h.Read(d)
-	}
-}
-
-func BenchmarkSha3_512_MTU(b *testing.B) { benchmarkHash(b, New512(), 1350, 1) }
-func BenchmarkSha3_384_MTU(b *testing.B) { benchmarkHash(b, New384(), 1350, 1) }
-func BenchmarkSha3_256_MTU(b *testing.B) { benchmarkHash(b, New256(), 1350, 1) }
-func BenchmarkSha3_224_MTU(b *testing.B) { benchmarkHash(b, New224(), 1350, 1) }
-
-func BenchmarkShake128_MTU(b *testing.B)  { benchmarkShake(b, NewShake128(), 1350, 1) }
-func BenchmarkShake256_MTU(b *testing.B)  { benchmarkShake(b, NewShake256(), 1350, 1) }
-func BenchmarkShake256_16x(b *testing.B)  { benchmarkShake(b, NewShake256(), 16, 1024) }
-func BenchmarkShake256_1MiB(b *testing.B) { benchmarkShake(b, NewShake256(), 1024, 1024) }
-
-func BenchmarkSha3_512_1MiB(b *testing.B) { benchmarkHash(b, New512(), 1024, 1024) }
-
-func Example_sum() {
-	buf := []byte("some data to hash")
-	// A hash needs to be 64 bytes long to have 256-bit collision resistance.
-	h := make([]byte, 64)
-	// Compute a 64-byte hash of buf and put it in h.
-	ShakeSum256(h, buf)
-	fmt.Printf("%x\n", h)
-	// Output: 0f65fe41fc353e52c55667bb9e2b27bfcc8476f2c413e9437d272ee3194a4e3146d05ec04a25d16b8f577c19b82d16b1424c3e022e783d2b4da98de3658d363d
-}
-
-func Example_mac() {
-	k := []byte("this is a secret key; you should generate a strong random key that's at least 32 bytes long")
-	buf := []byte("and this is some data to authenticate")
-	// A MAC with 32 bytes of output has 256-bit security strength -- if you use at least a 32-byte-long key.
-	h := make([]byte, 32)
-	d := NewShake256()
-	// Write the key into the hash.
-	d.Write(k)
-	// Now write the data.
-	d.Write(buf)
-	// Read 32 bytes of output from the hash into h.
-	d.Read(h)
-	fmt.Printf("%x\n", h)
-	// Output: 78de2974bd2711d5549ffd32b753ef0f5fa80a0db2556db60f0987eb8a9218ff
-}
-
-func ExampleNewCShake256() {
-	out := make([]byte, 32)
-	msg := []byte("The quick brown fox jumps over the lazy dog")
-
-	// Example 1: Simple cshake
-	c1 := NewCShake256([]byte("NAME"), []byte("Partition1"))
-	c1.Write(msg)
-	c1.Read(out)
-	fmt.Println(hex.EncodeToString(out))
-
-	// Example 2: Different customization string produces different digest
-	c1 = NewCShake256([]byte("NAME"), []byte("Partition2"))
-	c1.Write(msg)
-	c1.Read(out)
-	fmt.Println(hex.EncodeToString(out))
-
-	// Example 3: Longer output length produces longer digest
-	out = make([]byte, 64)
-	c1 = NewCShake256([]byte("NAME"), []byte("Partition1"))
-	c1.Write(msg)
-	c1.Read(out)
-	fmt.Println(hex.EncodeToString(out))
-
-	// Example 4: Next read produces different result
-	c1.Read(out)
-	fmt.Println(hex.EncodeToString(out))
-
-	// Output:
-	//a90a4c6ca9af2156eba43dc8398279e6b60dcd56fb21837afe6c308fd4ceb05b
-	//a8db03e71f3e4da5c4eee9d28333cdd355f51cef3c567e59be5beb4ecdbb28f0
-	//a90a4c6ca9af2156eba43dc8398279e6b60dcd56fb21837afe6c308fd4ceb05b9dd98c6ee866ca7dc5a39d53e960f400bcd5a19c8a2d6ec6459f63696543a0d8
-	//85e73a72228d08b46515553ca3a29d47df3047e5d84b12d6c2c63e579f4fd1105716b7838e92e981863907f434bfd4443c9e56ea09da998d2f9b47db71988109
-}

sha3/shake.go

@@ -4,24 +4,10 @@
 
 package sha3
 
-// This file defines the ShakeHash interface, and provides
-// functions for creating SHAKE and cSHAKE instances, as well as utility
-// functions for hashing bytes to arbitrary-length output.
-//
-//
-// SHAKE implementation is based on FIPS PUB 202 [1]
-// cSHAKE implementations is based on NIST SP 800-185 [2]
-//
-// [1] https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.202.pdf
-// [2] https://doi.org/10.6028/NIST.SP.800-185
-
 import (
-	"bytes"
+	"crypto/sha3"
-	"encoding/binary"
-	"errors"
 	"hash"
 	"io"
-	"math/bits"
 )
 
 // ShakeHash defines the interface to hash functions that support
@@ -32,7 +18,7 @@ type ShakeHash interface {
 	hash.Hash
 
 	// Read reads more output from the hash; reading affects the hash's
-	// state. (ShakeHash.Read is thus very different from Hash.Sum)
+	// state. (ShakeHash.Read is thus very different from Hash.Sum.)
 	// It never returns an error, but subsequent calls to Write or Sum
 	// will panic.
 	io.Reader
@@ -41,115 +27,18 @@ type ShakeHash interface {
 	Clone() ShakeHash
 }
 
-// cSHAKE specific context
-type cshakeState struct {
-	*state // SHA-3 state context and Read/Write operations
-
-	// initBlock is the cSHAKE specific initialization set of bytes. It is initialized
-	// by newCShake function and stores concatenation of N followed by S, encoded
-	// by the method specified in 3.3 of [1].
-	// It is stored here in order for Reset() to be able to put context into
-	// initial state.
-	initBlock []byte
-}
-
-func bytepad(data []byte, rate int) []byte {
-	out := make([]byte, 0, 9+len(data)+rate-1)
-	out = append(out, leftEncode(uint64(rate))...)
-	out = append(out, data...)
-	if padlen := rate - len(out)%rate; padlen < rate {
-		out = append(out, make([]byte, padlen)...)
-	}
-	return out
-}
-
-func leftEncode(x uint64) []byte {
-	// Let n be the smallest positive integer for which 2^(8n) > x.
-	n := (bits.Len64(x) + 7) / 8
-	if n == 0 {
-		n = 1
-	}
-	// Return n || x with n as a byte and x an n bytes in big-endian order.
-	b := make([]byte, 9)
-	binary.BigEndian.PutUint64(b[1:], x)
-	b = b[9-n-1:]
-	b[0] = byte(n)
-	return b
-}
-
-func newCShake(N, S []byte, rate, outputLen int, dsbyte byte) ShakeHash {
-	c := cshakeState{state: &state{rate: rate, outputLen: outputLen, dsbyte: dsbyte}}
-	c.initBlock = make([]byte, 0, 9+len(N)+9+len(S)) // leftEncode returns max 9 bytes
-	c.initBlock = append(c.initBlock, leftEncode(uint64(len(N))*8)...)
-	c.initBlock = append(c.initBlock, N...)
-	c.initBlock = append(c.initBlock, leftEncode(uint64(len(S))*8)...)
-	c.initBlock = append(c.initBlock, S...)
-	c.Write(bytepad(c.initBlock, c.rate))
-	return &c
-}
-
-// Reset resets the hash to initial state.
-func (c *cshakeState) Reset() {
-	c.state.Reset()
-	c.Write(bytepad(c.initBlock, c.rate))
-}
-
-// Clone returns copy of a cSHAKE context within its current state.
-func (c *cshakeState) Clone() ShakeHash {
-	b := make([]byte, len(c.initBlock))
-	copy(b, c.initBlock)
-	return &cshakeState{state: c.clone(), initBlock: b}
-}
-
-// Clone returns copy of SHAKE context within its current state.
-func (c *state) Clone() ShakeHash {
-	return c.clone()
-}
-
-func (c *cshakeState) MarshalBinary() ([]byte, error) {
-	return c.AppendBinary(make([]byte, 0, marshaledSize+len(c.initBlock)))
-}
-
-func (c *cshakeState) AppendBinary(b []byte) ([]byte, error) {
-	b, err := c.state.AppendBinary(b)
-	if err != nil {
-		return nil, err
-	}
-	b = append(b, c.initBlock...)
-	return b, nil
-}
-
-func (c *cshakeState) UnmarshalBinary(b []byte) error {
-	if len(b) <= marshaledSize {
-		return errors.New("sha3: invalid hash state")
-	}
-	if err := c.state.UnmarshalBinary(b[:marshaledSize]); err != nil {
-		return err
-	}
-	c.initBlock = bytes.Clone(b[marshaledSize:])
-	return nil
-}
-
 // NewShake128 creates a new SHAKE128 variable-output-length ShakeHash.
 // Its generic security strength is 128 bits against all attacks if at
 // least 32 bytes of its output are used.
 func NewShake128() ShakeHash {
-	return newShake128()
+	return &shakeWrapper{sha3.NewSHAKE128(), 32, false, sha3.NewSHAKE128}
 }
 
 // NewShake256 creates a new SHAKE256 variable-output-length ShakeHash.
 // Its generic security strength is 256 bits against all attacks if
 // at least 64 bytes of its output are used.
 func NewShake256() ShakeHash {
-	return newShake256()
+	return &shakeWrapper{sha3.NewSHAKE256(), 64, false, sha3.NewSHAKE256}
-}
-
-func newShake128Generic() *state {
-	return &state{rate: rateK256, outputLen: 32, dsbyte: dsbyteShake}
-}
-
-func newShake256Generic() *state {
-	return &state{rate: rateK512, outputLen: 64, dsbyte: dsbyteShake}
 }
 
 // NewCShake128 creates a new instance of cSHAKE128 variable-output-length ShakeHash,
@@ -159,10 +48,9 @@ func newShake256Generic() *state {
 // computations on same input with different S yield unrelated outputs.
 // When N and S are both empty, this is equivalent to NewShake128.
 func NewCShake128(N, S []byte) ShakeHash {
-	if len(N) == 0 && len(S) == 0 {
+	return &shakeWrapper{sha3.NewCSHAKE128(N, S), 32, false, func() *sha3.SHAKE {
-		return NewShake128()
+		return sha3.NewCSHAKE128(N, S)
-	}
+	}}
-	return newCShake(N, S, rateK256, 32, dsbyteCShake)
 }
 
 // NewCShake256 creates a new instance of cSHAKE256 variable-output-length ShakeHash,
@@ -172,10 +60,9 @@ func NewCShake128(N, S []byte) ShakeHash {
 // computations on same input with different S yield unrelated outputs.
 // When N and S are both empty, this is equivalent to NewShake256.
 func NewCShake256(N, S []byte) ShakeHash {
-	if len(N) == 0 && len(S) == 0 {
+	return &shakeWrapper{sha3.NewCSHAKE256(N, S), 64, false, func() *sha3.SHAKE {
-		return NewShake256()
+		return sha3.NewCSHAKE256(N, S)
-	}
+	}}
-	return newCShake(N, S, rateK512, 64, dsbyteCShake)
 }
 
 // ShakeSum128 writes an arbitrary-length digest of data into hash.
@@ -191,3 +78,42 @@ func ShakeSum256(hash, data []byte) {
 	h.Write(data)
 	h.Read(hash)
 }
+
+// shakeWrapper adds the Size, Sum, and Clone methods to a sha3.SHAKE
+// to implement the ShakeHash interface.
+type shakeWrapper struct {
+	*sha3.SHAKE
+	outputLen int
+	squeezing bool
+	newSHAKE  func() *sha3.SHAKE
+}
+
+func (w *shakeWrapper) Read(p []byte) (n int, err error) {
+	w.squeezing = true
+	return w.SHAKE.Read(p)
+}
+
+func (w *shakeWrapper) Clone() ShakeHash {
+	s := w.newSHAKE()
+	b, err := w.MarshalBinary()
+	if err != nil {
+		panic(err) // unreachable
+	}
+	if err := s.UnmarshalBinary(b); err != nil {
+		panic(err) // unreachable
+	}
+	return &shakeWrapper{s, w.outputLen, w.squeezing, w.newSHAKE}
+}
+
+func (w *shakeWrapper) Size() int { return w.outputLen }
+
+func (w *shakeWrapper) Sum(b []byte) []byte {
+	if w.squeezing {
+		panic("sha3: Sum after Read")
+	}
+	out := make([]byte, w.outputLen)
+	// Clone the state so that we don't affect future Write calls.
+	s := w.Clone()
+	s.Read(out)
+	return append(b, out...)
+}

sha3/shake_noasm.go

@@ -1,15 +0,0 @@
-// Copyright 2023 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 || !s390x
-
-package sha3
-
-func newShake128() *state {
-	return newShake128Generic()
-}
-
-func newShake256() *state {
-	return newShake256Generic()
-}

ssh/agent/client.go

@@ -430,8 +430,9 @@ func (c *client) List() ([]*Key, error) {
 		return keys, nil
 	case *failureAgentMsg:
 		return nil, errors.New("agent: failed to list keys")
+	default:
+		return nil, fmt.Errorf("agent: failed to list keys, unexpected message type %T", msg)
 	}
-	panic("unreachable")
 }
 
 // Sign has the agent sign the data using a protocol 2 key as defined
@@ -462,8 +463,9 @@ func (c *client) SignWithFlags(key ssh.PublicKey, data []byte, flags SignatureFl
 		return &sig, nil
 	case *failureAgentMsg:
 		return nil, errors.New("agent: failed to sign challenge")
+	default:
+		return nil, fmt.Errorf("agent: failed to sign challenge, unexpected message type %T", msg)
 	}
-	panic("unreachable")
 }
 
 // unmarshal parses an agent message in packet, returning the parsed
@@ -661,6 +663,13 @@ 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)

ssh/agent/client_test.go

@@ -7,6 +7,7 @@ package agent
 import (
 	"bytes"
 	"crypto/rand"
+	"encoding/binary"
 	"errors"
 	"io"
 	"net"
@@ -39,7 +40,11 @@ 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 {
@@ -347,6 +352,53 @@ func TestServerResponseTooLarge(t *testing.T) {
 	}
 }
 
+func TestInvalidResponses(t *testing.T) {
+	a, b, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	done := make(chan struct{})
+	defer func() { <-done }()
+
+	defer a.Close()
+	defer b.Close()
+
+	agent := NewClient(a)
+	go func() {
+		defer close(done)
+
+		resp := []byte{agentSuccess}
+		msg := make([]byte, 4+len(resp))
+		binary.BigEndian.PutUint32(msg[:4], uint32(len(resp)))
+		copy(msg[4:], resp)
+
+		if _, err := b.Write(msg); err != nil {
+			t.Errorf("unexpected error sending agent reply: %v", err)
+			b.Close()
+			return
+		}
+
+		if _, err := b.Write(msg); err != nil {
+			t.Errorf("unexpected error sending agent reply: %v", err)
+			b.Close()
+		}
+	}()
+	_, err = agent.List()
+	if err == nil {
+		t.Fatal("error expected")
+	}
+	if !strings.Contains(err.Error(), "failed to list keys, unexpected message type") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	_, err = agent.Sign(testPublicKeys["rsa"], []byte("message"))
+	if err == nil {
+		t.Fatal("error expected")
+	}
+	if !strings.Contains(err.Error(), "failed to sign challenge, unexpected message type") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
 func TestAuth(t *testing.T) {
 	agent, _, cleanup := startOpenSSHAgent(t)
 	defer cleanup()
@@ -542,3 +594,63 @@ 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)
+		}
+	}
+}

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
+// NewKeyring returns an Agent that holds keys in memory.  It is safe for
-// for concurrent use by multiple goroutines.
+// concurrent use by multiple goroutines.
+//
+// The returned Agent only supports the "lifetime" constraint.
 func NewKeyring() Agent {
 	return &keyring{}
 }
@@ -112,7 +114,7 @@ func (r *keyring) Unlock(passphrase []byte) error {
 }
 
 // expireKeysLocked removes expired keys from the keyring. If a key was added
-// with a lifetimesecs contraint and seconds >= lifetimesecs seconds have
+// with a lifetimesecs constraint and seconds >= lifetimesecs seconds have
 // elapsed, it is removed. The caller *must* be holding the keyring mutex.
 func (r *keyring) expireKeysLocked() {
 	for _, k := range r.keys {
@@ -143,15 +145,26 @@ func (r *keyring) List() ([]*Key, error) {
 	return ids, nil
 }
 
-// Insert adds a private key to the keyring. If a certificate
+// Add adds a private key to the keyring. If a certificate is given, that
-// is given, that certificate is added as public key. Note that
+// certificate is added as public key.
-// any constraints given are ignored.
+//
+// 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

@@ -30,7 +30,7 @@ func validateListedKeys(t *testing.T, a Agent, expectedKeys []string) {
 		return
 	}
 	if len(listedKeys) != len(expectedKeys) {
-		t.Fatalf("expeted %d key, got %d", len(expectedKeys), len(listedKeys))
+		t.Fatalf("expected %d key, got %d", len(expectedKeys), len(listedKeys))
 		return
 	}
 	actualKeys := make(map[string]bool)
@@ -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}
 	}
 
@@ -203,6 +203,9 @@ func parseConstraints(constraints []byte) (lifetimeSecs uint32, confirmBeforeUse
 	for len(constraints) != 0 {
 		switch constraints[0] {
 		case agentConstrainLifetime:
+			if len(constraints) < 5 {
+				return 0, false, nil, io.ErrUnexpectedEOF
+			}
 			lifetimeSecs = binary.BigEndian.Uint32(constraints[1:5])
 			constraints = constraints[5:]
 		case agentConstrainConfirm:
@@ -267,6 +270,9 @@ 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}
@@ -333,6 +339,9 @@ 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 {

ssh/agent/server_test.go

@@ -8,6 +8,7 @@ import (
 	"crypto"
 	"crypto/rand"
 	"fmt"
+	"io"
 	pseudorand "math/rand"
 	"reflect"
 	"strings"
@@ -258,9 +259,47 @@ func TestParseConstraints(t *testing.T) {
 		t.Errorf("got extension %v, want %v", extensions, expect)
 	}
 
+	// Test Malformed Constraint
+	_, _, _, err = parseConstraints([]byte{1})
+	if err != io.ErrUnexpectedEOF {
+		t.Errorf("got %v, want %v", err, io.ErrUnexpectedEOF)
+	}
+
 	// Test Unknown Constraint
 	_, _, _, err = parseConstraints([]byte{128})
 	if err == nil || !strings.Contains(err.Error(), "unknown constraint") {
 		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/certs.go

@@ -348,6 +348,9 @@ 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)
 	}
@@ -375,6 +378,9 @@ 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")
 	}
@@ -438,7 +444,17 @@ 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

@@ -9,8 +9,10 @@ import (
 	"crypto/ecdsa"
 	"crypto/elliptic"
 	"crypto/rand"
+	"crypto/sha256"
 	"fmt"
 	"io"
+	"math/big"
 	"net"
 	"reflect"
 	"testing"
@@ -128,6 +130,103 @@ 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"},
@@ -330,15 +429,13 @@ 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(),
 			}
-			cert.SignCert(rand.Reader, priv)
+			if err := cert.SignCert(rand.Reader, priv); err != nil {
+				t.Fatalf("error signing certificate: %v", err)
+			}
 
 			certSigner, err := NewCertSigner(cert, priv)
 			if err != nil {

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 {
+// minPayloadSize returns min(limit, length) clamped to a uint32. It is used
-	if a < uint32(b) {
+// to compute the size of the next channel data packet from the remaining
-		return a
+// 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
@@ -177,6 +184,12 @@ 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
 
@@ -251,7 +264,7 @@ 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
 		}
@@ -460,6 +473,18 @@ 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
 	}
@@ -530,7 +555,17 @@ 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 +621,24 @@ 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 <-ch.msg:
+			default:
+				break drain
+			}
+		}
 	}
 
 	msg := channelRequestMsg{

ssh/channel_test.go

@@ -0,0 +1,140 @@
+// 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 (
+	"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")
+	}
+}

ssh/cipher.go

@@ -8,6 +8,7 @@ import (
 	"crypto/aes"
 	"crypto/cipher"
 	"crypto/des"
+	"crypto/fips140"
 	"crypto/rc4"
 	"crypto/subtle"
 	"encoding/binary"
@@ -15,6 +16,7 @@ import (
 	"fmt"
 	"hash"
 	"io"
+	"slices"
 
 	"golang.org/x/crypto/chacha20"
 	"golang.org/x/crypto/internal/poly1305"
@@ -93,41 +95,41 @@ func streamCipherMode(skip int, createFunc func(key, iv []byte) (cipher.Stream,
 }
 
 // cipherModes documents properties of supported ciphers. Ciphers not included
-// are not supported and will not be negotiated, even if explicitly requested in
+// are not supported and will not be negotiated, even if explicitly configured.
-// ClientConfig.Crypto.Ciphers.
+// When FIPS mode is enabled, only FIPS-approved algorithms are included.
-var cipherModes = map[string]*cipherMode{
+var cipherModes = map[string]*cipherMode{}
-	// Ciphers from RFC 4344, which introduced many CTR-based ciphers. Algorithms
-	// are defined in the order specified in the RFC.
-	CipherAES128CTR: {16, aes.BlockSize, streamCipherMode(0, newAESCTR)},
-	CipherAES192CTR: {24, aes.BlockSize, streamCipherMode(0, newAESCTR)},
-	CipherAES256CTR: {32, aes.BlockSize, streamCipherMode(0, newAESCTR)},
 
-	// Ciphers from RFC 4345, which introduces security-improved arcfour ciphers.
+func init() {
-	// They are defined in the order specified in the RFC.
+	cipherModes[CipherAES128CTR] = &cipherMode{16, aes.BlockSize, streamCipherMode(0, newAESCTR)}
-	InsecureCipherRC4128: {16, 0, streamCipherMode(1536, newRC4)},
+	cipherModes[CipherAES192CTR] = &cipherMode{24, aes.BlockSize, streamCipherMode(0, newAESCTR)}
-	InsecureCipherRC4256: {32, 0, streamCipherMode(1536, newRC4)},
+	cipherModes[CipherAES256CTR] = &cipherMode{32, aes.BlockSize, streamCipherMode(0, newAESCTR)}
+	//  Use of GCM with arbitrary IVs is not allowed in FIPS 140-only mode,
+	// we'll wire it up to NewGCMForSSH in Go 1.26.
+	//
+	// For now it means we'll work with fips140=on but not fips140=only.
+	cipherModes[CipherAES128GCM] = &cipherMode{16, 12, newGCMCipher}
+	cipherModes[CipherAES256GCM] = &cipherMode{32, 12, newGCMCipher}
 
-	// Cipher defined in RFC 4253, which describes SSH Transport Layer Protocol.
+	if fips140.Enabled() {
-	// Note that this cipher is not safe, as stated in RFC 4253: "Arcfour (and
+		defaultCiphers = slices.DeleteFunc(defaultCiphers, func(algo string) bool {
-	// RC4) has problems with weak keys, and should be used with caution."
+			_, ok := cipherModes[algo]
-	// RFC 4345 introduces improved versions of Arcfour.
+			return !ok
-	InsecureCipherRC4: {16, 0, streamCipherMode(0, newRC4)},
+		})
-
+		return
-	// AEAD ciphers
+	}
-	CipherAES128GCM:        {16, 12, newGCMCipher},
-	CipherAES256GCM:        {32, 12, newGCMCipher},
-	CipherChaCha20Poly1305: {64, 0, newChaCha20Cipher},
 
+	cipherModes[CipherChaCha20Poly1305] = &cipherMode{64, 0, newChaCha20Cipher}
+	// Insecure ciphers not included in the default configuration.
+	cipherModes[InsecureCipherRC4128] = &cipherMode{16, 0, streamCipherMode(1536, newRC4)}
+	cipherModes[InsecureCipherRC4256] = &cipherMode{32, 0, streamCipherMode(1536, newRC4)}
+	cipherModes[InsecureCipherRC4] = &cipherMode{16, 0, streamCipherMode(0, newRC4)}
 	// CBC mode is insecure and so is not included in the default config.
 	// (See https://www.ieee-security.org/TC/SP2013/papers/4977a526.pdf). If absolutely
 	// needed, it's possible to specify a custom Config to enable it.
 	// You should expect that an active attacker can recover plaintext if
 	// you do.
-	InsecureCipherAES128CBC: {16, aes.BlockSize, newAESCBCCipher},
+	cipherModes[InsecureCipherAES128CBC] = &cipherMode{16, aes.BlockSize, newAESCBCCipher}
-
+	cipherModes[InsecureCipherTripleDESCBC] = &cipherMode{24, des.BlockSize, newTripleDESCBCCipher}
-	// 3des-cbc is insecure and is not included in the default
-	// config.
-	InsecureCipherTripleDESCBC: {24, des.BlockSize, newTripleDESCBCCipher},
 }
 
 // prefixLen is the length of the packet prefix that contains the packet length
@@ -405,7 +407,7 @@ 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)]
@@ -584,7 +586,7 @@ 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_auth.go

@@ -9,6 +9,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"slices"
 	"strings"
 )
 
@@ -83,7 +84,7 @@ func (c *connection) clientAuthenticate(config *ClientConfig) error {
 			// success
 			return nil
 		} else if ok == authFailure {
-			if m := auth.method(); !contains(tried, m) {
+			if m := auth.method(); !slices.Contains(tried, m) {
 				tried = append(tried, m)
 			}
 		}
@@ -97,7 +98,7 @@ func (c *connection) clientAuthenticate(config *ClientConfig) error {
 	findNext:
 		for _, a := range config.Auth {
 			candidateMethod := a.method()
-			if contains(tried, candidateMethod) {
+			if slices.Contains(tried, candidateMethod) {
 				continue
 			}
 			for _, meth := range methods {
@@ -117,15 +118,6 @@ func (c *connection) clientAuthenticate(config *ClientConfig) error {
 	return fmt.Errorf("ssh: unable to authenticate, attempted methods %v, no supported methods remain", tried)
 }
 
-func contains(list []string, e string) bool {
-	for _, s := range list {
-		if s == e {
-			return true
-		}
-	}
-	return false
-}
-
 // An AuthMethod represents an instance of an RFC 4252 authentication method.
 type AuthMethod interface {
 	// auth authenticates user over transport t.
@@ -255,7 +247,7 @@ func pickSignatureAlgorithm(signer Signer, extensions map[string][]byte) (MultiA
 		// Fallback to use if there is no "server-sig-algs" extension or a
 		// common algorithm cannot be found. We use the public key format if the
 		// MultiAlgorithmSigner supports it, otherwise we return an error.
-		if !contains(as.Algorithms(), underlyingAlgo(keyFormat)) {
+		if !slices.Contains(as.Algorithms(), underlyingAlgo(keyFormat)) {
 			return "", fmt.Errorf("ssh: no common public key signature algorithm, server only supports %q for key type %q, signer only supports %v",
 				underlyingAlgo(keyFormat), keyFormat, as.Algorithms())
 		}
@@ -282,10 +274,14 @@ 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) {
+	for _, signerAlgo := range as.Algorithms() {
-		if contains(as.Algorithms(), underlyingAlgo(algo)) {
+		if idx := slices.IndexFunc(supportedKeyAlgos, func(algo string) bool {
-			keyAlgos = append(keyAlgos, algo)
+			return underlyingAlgo(algo) == signerAlgo
+		}); idx >= 0 {
+			keyAlgos = append(keyAlgos, supportedKeyAlgos[idx])
 		}
 	}
 
@@ -334,7 +330,7 @@ func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand
 		// the key try to use the obtained algorithm as if "server-sig-algs" had
 		// not been implemented if supported from the algorithm signer.
 		if !ok && idx < origSignersLen && isRSACert(algo) && algo != CertAlgoRSAv01 {
-			if contains(as.Algorithms(), KeyAlgoRSA) {
+			if slices.Contains(as.Algorithms(), KeyAlgoRSA) {
 				// We retry using the compat algorithm after all signers have
 				// been tried normally.
 				signers = append(signers, &multiAlgorithmSigner{
@@ -385,7 +381,7 @@ func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand
 		// 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 || !contains(methods, cb.method()) {
+		if success == authSuccess || !slices.Contains(methods, cb.method()) {
 			return success, methods, err
 		}
 	}
@@ -434,7 +430,7 @@ func confirmKeyAck(key PublicKey, c packetConn) (bool, error) {
 			// servers send the key type instead. OpenSSH allows any algorithm
 			// that matches the public key, so we do the same.
 			// https://github.com/openssh/openssh-portable/blob/86bdd385/sshconnect2.c#L709
-			if !contains(algorithmsForKeyFormat(key.Type()), msg.Algo) {
+			if !slices.Contains(algorithmsForKeyFormat(key.Type()), msg.Algo) {
 				return false, nil
 			}
 			if !bytes.Equal(msg.PubKey, pubKey) {

ssh/client_auth_test.go

@@ -14,6 +14,7 @@ import (
 	"net"
 	"os"
 	"runtime"
+	"slices"
 	"strings"
 	"testing"
 )
@@ -1135,7 +1136,7 @@ func TestPickSignatureAlgorithm(t *testing.T) {
 				t.Fatalf("error generating cert signer: %v", err)
 			}
 			// The signer supports the public key algorithm and the
-			// public key format is a certificate type so the cerificate
+			// public key format is a certificate type so the certificate
 			// algorithm matching the key format must be returned
 			_, algo, err = pickSignatureAlgorithm(certSigner, c.extensions)
 			if err != nil {
@@ -1158,6 +1159,52 @@ 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.
@@ -1214,7 +1261,7 @@ func (cb configurablePublicKeyCallback) auth(session []byte, user string, c pack
 	if err != nil {
 		return authFailure, nil, err
 	}
-	if success == authSuccess || !contains(methods, cb.method()) {
+	if success == authSuccess || !slices.Contains(methods, cb.method()) {
 		return success, methods, err
 	}
 

ssh/common.go

@@ -6,6 +6,7 @@ package ssh
 
 import (
 	"crypto"
+	"crypto/fips140"
 	"crypto/rand"
 	"fmt"
 	"io"
@@ -256,6 +257,40 @@ type Algorithms struct {
 	PublicKeyAuths []string
 }
 
+func init() {
+	if fips140.Enabled() {
+		defaultHostKeyAlgos = slices.DeleteFunc(defaultHostKeyAlgos, func(algo string) bool {
+			_, err := hashFunc(underlyingAlgo(algo))
+			return err != nil
+		})
+		defaultPubKeyAuthAlgos = slices.DeleteFunc(defaultPubKeyAuthAlgos, func(algo string) bool {
+			_, err := hashFunc(underlyingAlgo(algo))
+			return err != nil
+		})
+	}
+}
+
+func hashFunc(format string) (crypto.Hash, error) {
+	switch format {
+	case KeyAlgoRSASHA256, KeyAlgoECDSA256, KeyAlgoSKED25519, KeyAlgoSKECDSA256:
+		return crypto.SHA256, nil
+	case KeyAlgoECDSA384:
+		return crypto.SHA384, nil
+	case KeyAlgoRSASHA512, KeyAlgoECDSA521:
+		return crypto.SHA512, nil
+	case KeyAlgoED25519:
+		// KeyAlgoED25519 doesn't pre-hash.
+		return 0, nil
+	case KeyAlgoRSA, InsecureKeyAlgoDSA:
+		if fips140.Enabled() {
+			return 0, fmt.Errorf("ssh: hash algorithm for format %q not allowed in FIPS 140 mode", format)
+		}
+		return crypto.SHA1, nil
+	default:
+		return 0, fmt.Errorf("ssh: hash algorithm for format %q not mapped", format)
+	}
+}
+
 // SupportedAlgorithms returns algorithms currently implemented by this package,
 // excluding those with security issues, which are returned by
 // InsecureAlgorithms. The algorithms listed here are in preference order.
@@ -283,21 +318,6 @@ func InsecureAlgorithms() Algorithms {
 
 var supportedCompressions = []string{compressionNone}
 
-// hashFuncs keeps the mapping of supported signature algorithms to their
-// respective hashes needed for signing and verification.
-var hashFuncs = map[string]crypto.Hash{
-	KeyAlgoRSA:         crypto.SHA1,
-	KeyAlgoRSASHA256:   crypto.SHA256,
-	KeyAlgoRSASHA512:   crypto.SHA512,
-	InsecureKeyAlgoDSA: crypto.SHA1,
-	KeyAlgoECDSA256:    crypto.SHA256,
-	KeyAlgoECDSA384:    crypto.SHA384,
-	KeyAlgoECDSA521:    crypto.SHA512,
-	// KeyAlgoED25519 doesn't pre-hash.
-	KeyAlgoSKECDSA256: crypto.SHA256,
-	KeyAlgoSKED25519:  crypto.SHA256,
-}
-
 // algorithmsForKeyFormat returns the supported signature algorithms for a given
 // public key format (PublicKey.Type), in order of preference. See RFC 8332,
 // Section 2. See also the note in sendKexInit on backwards compatibility.
@@ -312,11 +332,40 @@ func algorithmsForKeyFormat(keyFormat string) []string {
 	}
 }
 
+// keyFormatForAlgorithm returns the key format corresponding to the given
+// signature algorithm. It returns an empty string if the signature algorithm is
+// invalid or unsupported.
+func keyFormatForAlgorithm(sigAlgo string) string {
+	switch sigAlgo {
+	case KeyAlgoRSA, KeyAlgoRSASHA256, KeyAlgoRSASHA512:
+		return KeyAlgoRSA
+	case CertAlgoRSAv01, CertAlgoRSASHA256v01, CertAlgoRSASHA512v01:
+		return CertAlgoRSAv01
+	case KeyAlgoED25519,
+		KeyAlgoSKED25519,
+		KeyAlgoSKECDSA256,
+		KeyAlgoECDSA256,
+		KeyAlgoECDSA384,
+		KeyAlgoECDSA521,
+		InsecureKeyAlgoDSA,
+		InsecureCertAlgoDSAv01,
+		CertAlgoECDSA256v01,
+		CertAlgoECDSA384v01,
+		CertAlgoECDSA521v01,
+		CertAlgoSKECDSA256v01,
+		CertAlgoED25519v01,
+		CertAlgoSKED25519v01:
+		return sigAlgo
+	default:
+		return ""
+	}
+}
+
 // isRSA returns whether algo is a supported RSA algorithm, including certificate
 // algorithms.
 func isRSA(algo string) bool {
 	algos := algorithmsForKeyFormat(KeyAlgoRSA)
-	return contains(algos, underlyingAlgo(algo))
+	return slices.Contains(algos, underlyingAlgo(algo))
 }
 
 func isRSACert(algo string) bool {
@@ -515,7 +564,7 @@ func (c *Config) SetDefaults() {
 		if kexAlgoMap[k] != nil {
 			// Ignore the KEX if we have no kexAlgoMap definition.
 			kexs = append(kexs, k)
-			if k == KeyExchangeCurve25519 && !contains(c.KeyExchanges, keyExchangeCurve25519LibSSH) {
+			if k == KeyExchangeCurve25519 && !slices.Contains(c.KeyExchanges, keyExchangeCurve25519LibSSH) {
 				kexs = append(kexs, keyExchangeCurve25519LibSSH)
 			}
 		}

ssh/common_test.go

@@ -5,7 +5,9 @@
 package ssh
 
 import (
+	"maps"
 	"reflect"
+	"slices"
 	"testing"
 )
 
@@ -174,3 +176,21 @@ func TestFindAgreedAlgorithms(t *testing.T) {
 		})
 	}
 }
+
+func TestKeyFormatAlgorithms(t *testing.T) {
+	supportedAlgos := SupportedAlgorithms()
+	insecureAlgos := InsecureAlgorithms()
+	algoritms := append(supportedAlgos.PublicKeyAuths, insecureAlgos.PublicKeyAuths...)
+	algoritms = append(algoritms, slices.Collect(maps.Keys(certKeyAlgoNames))...)
+
+	for _, algo := range algoritms {
+		keyFormat := keyFormatForAlgorithm(algo)
+		if keyFormat == "" {
+			t.Errorf("got empty key format for algorithm %q", algo)
+		}
+		if !slices.Contains(algorithmsForKeyFormat(keyFormat), algo) {
+			t.Errorf("algorithms for key format %q, does not contain %q", keyFormat, algo)
+		}
+
+	}
+}

ssh/doc.go

@@ -17,8 +17,18 @@ References:
 	[PROTOCOL.certkeys]: http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/PROTOCOL.certkeys?rev=HEAD
 	[SSH-PARAMETERS]:    http://www.iana.org/assignments/ssh-parameters/ssh-parameters.xml#ssh-parameters-1
 	[SSH-CERTS]:	https://datatracker.ietf.org/doc/html/draft-miller-ssh-cert-01
+	[FIPS 140-3 mode]: https://go.dev/doc/security/fips140
 
 This package does not fall under the stability promise of the Go language itself,
 so its API may be changed when pressing needs arise.
+
+# FIPS 140-3 mode
+
+When the program is in [FIPS 140-3 mode], this package behaves as if only SP
+800-140C and SP 800-140D approved cipher suites, signature algorithms,
+certificate public key types and sizes, and key exchange and derivation
+algorithms were implemented. Others are silently ignored and not negotiated, or
+rejected. This set may depend on the algorithms supported by the FIPS 140-3 Go
+Cryptographic Module selected with GOFIPS140, and may change across Go versions.
 */
 package ssh

ssh/example_test.go

@@ -155,7 +155,7 @@ func ExampleNewServerConn() {
 }
 
 func ExampleServerConfig() {
-	// Minimal ServerConfig with SHA-1 algoritms disabled and supporting only
+	// Minimal ServerConfig with SHA-1 algorithms disabled and supporting only
 	// public key authentication.
 
 	// The algorithms returned by ssh.SupportedAlgorithms() are different from
@@ -344,7 +344,7 @@ func ExampleClientConfig() {
 		log.Fatalf("unable to parse private key: %v", err)
 	}
 
-	// Minimal ClientConfig with SHA-1 algoritms disabled.
+	// Minimal ClientConfig with SHA-1 algorithms disabled.
 	// The algorithms returned by ssh.SupportedAlgorithms() are different from
 	// the default ones and do not include algorithms that are considered
 	// insecure, such as those using SHA-1, returned by
@@ -361,7 +361,7 @@ func ExampleClientConfig() {
 			ssh.PublicKeys(signer),
 		},
 		HostKeyCallback: ssh.FixedHostKey(hostKey),
-		// We should check that hostKey algorithm is inlcuded in
+		// We should check that hostKey algorithm is included in
 		// algorithms.HostKeys.
 		HostKeyAlgorithms: algorithms.HostKeys,
 	}

ssh/handshake.go

@@ -10,6 +10,7 @@ import (
 	"io"
 	"log"
 	"net"
+	"slices"
 	"strings"
 	"sync"
 )
@@ -527,7 +528,7 @@ func (t *handshakeTransport) sendKexInit() error {
 			switch s := k.(type) {
 			case MultiAlgorithmSigner:
 				for _, algo := range algorithmsForKeyFormat(keyFormat) {
-					if contains(s.Algorithms(), underlyingAlgo(algo)) {
+					if slices.Contains(s.Algorithms(), underlyingAlgo(algo)) {
 						msg.ServerHostKeyAlgos = append(msg.ServerHostKeyAlgos, algo)
 					}
 				}
@@ -679,7 +680,7 @@ func (t *handshakeTransport) enterKeyExchange(otherInitPacket []byte) error {
 		return err
 	}
 
-	if t.sessionID == nil && ((isClient && contains(serverInit.KexAlgos, kexStrictServer)) || (!isClient && contains(clientInit.KexAlgos, kexStrictClient))) {
+	if t.sessionID == nil && ((isClient && slices.Contains(serverInit.KexAlgos, kexStrictServer)) || (!isClient && slices.Contains(clientInit.KexAlgos, kexStrictClient))) {
 		t.strictMode = true
 		if err := t.conn.setStrictMode(); err != nil {
 			return err
@@ -736,7 +737,7 @@ func (t *handshakeTransport) enterKeyExchange(otherInitPacket []byte) error {
 	// On the server side, after the first SSH_MSG_NEWKEYS, send a SSH_MSG_EXT_INFO
 	// message with the server-sig-algs extension if the client supports it. See
 	// RFC 8308, Sections 2.4 and 3.1, and [PROTOCOL], Section 1.9.
-	if !isClient && firstKeyExchange && contains(clientInit.KexAlgos, "ext-info-c") {
+	if !isClient && firstKeyExchange && slices.Contains(clientInit.KexAlgos, "ext-info-c") {
 		supportedPubKeyAuthAlgosList := strings.Join(t.publicKeyAuthAlgorithms, ",")
 		extInfo := &extInfoMsg{
 			NumExtensions: 2,
@@ -790,7 +791,7 @@ func (a algorithmSignerWrapper) SignWithAlgorithm(rand io.Reader, data []byte, a
 func pickHostKey(hostKeys []Signer, algo string) AlgorithmSigner {
 	for _, k := range hostKeys {
 		if s, ok := k.(MultiAlgorithmSigner); ok {
-			if !contains(s.Algorithms(), underlyingAlgo(algo)) {
+			if !slices.Contains(s.Algorithms(), underlyingAlgo(algo)) {
 				continue
 			}
 		}

ssh/handshake_test.go

@@ -1330,7 +1330,7 @@ func TestAlgorithmNegotiationError(t *testing.T) {
 
 	_, _, _, err = NewClientConn(c2, "", clientConf)
 	if err == nil {
-		t.Fatal("client connection succeded expected algorithm negotiation error")
+		t.Fatal("client connection succeeded expected algorithm negotiation error")
 	}
 	var negotiationError *AlgorithmNegotiationError
 	if !errors.As(err, &negotiationError) {

ssh/kex.go

@@ -8,12 +8,14 @@ import (
 	"crypto"
 	"crypto/ecdsa"
 	"crypto/elliptic"
+	"crypto/fips140"
 	"crypto/rand"
 	"encoding/binary"
 	"errors"
 	"fmt"
 	"io"
 	"math/big"
+	"slices"
 
 	"golang.org/x/crypto/curve25519"
 )
@@ -395,9 +397,27 @@ func ecHash(curve elliptic.Curve) crypto.Hash {
 	return crypto.SHA512
 }
 
+// kexAlgoMap defines the supported KEXs. KEXs not included are not supported
+// and will not be negotiated, even if explicitly configured. When FIPS mode is
+// enabled, only FIPS-approved algorithms are included.
 var kexAlgoMap = map[string]kexAlgorithm{}
 
 func init() {
+	// mlkem768x25519-sha256 we'll work with fips140=on but not fips140=only
+	// until Go 1.26.
+	kexAlgoMap[KeyExchangeMLKEM768X25519] = &mlkem768WithCurve25519sha256{}
+	kexAlgoMap[KeyExchangeECDHP521] = &ecdh{elliptic.P521()}
+	kexAlgoMap[KeyExchangeECDHP384] = &ecdh{elliptic.P384()}
+	kexAlgoMap[KeyExchangeECDHP256] = &ecdh{elliptic.P256()}
+
+	if fips140.Enabled() {
+		defaultKexAlgos = slices.DeleteFunc(defaultKexAlgos, func(algo string) bool {
+			_, ok := kexAlgoMap[algo]
+			return !ok
+		})
+		return
+	}
+
 	p, _ := new(big.Int).SetString(oakleyGroup2, 16)
 	kexAlgoMap[InsecureKeyExchangeDH1SHA1] = &dhGroup{
 		g:        new(big.Int).SetInt64(2),
@@ -431,14 +451,10 @@ func init() {
 		hashFunc: crypto.SHA512,
 	}
 
-	kexAlgoMap[KeyExchangeECDHP521] = &ecdh{elliptic.P521()}
-	kexAlgoMap[KeyExchangeECDHP384] = &ecdh{elliptic.P384()}
-	kexAlgoMap[KeyExchangeECDHP256] = &ecdh{elliptic.P256()}
 	kexAlgoMap[KeyExchangeCurve25519] = &curve25519sha256{}
 	kexAlgoMap[keyExchangeCurve25519LibSSH] = &curve25519sha256{}
 	kexAlgoMap[InsecureKeyExchangeDHGEXSHA1] = &dhGEXSHA{hashFunc: crypto.SHA1}
 	kexAlgoMap[KeyExchangeDHGEXSHA256] = &dhGEXSHA{hashFunc: crypto.SHA256}
-	kexAlgoMap[KeyExchangeMLKEM768X25519] = &mlkem768WithCurve25519sha256{}
 }
 
 // curve25519sha256 implements the curve25519-sha256 (formerly known as

ssh/keys.go

@@ -27,6 +27,7 @@ import (
 	"fmt"
 	"io"
 	"math/big"
+	"slices"
 	"strings"
 
 	"golang.org/x/crypto/ssh/internal/bcrypt_pbkdf"
@@ -89,6 +90,11 @@ func parsePubKey(in []byte, algo string) (pubKey PublicKey, rest []byte, err err
 		}
 		return cert, nil, nil
 	}
+	if keyFormat := keyFormatForAlgorithm(algo); keyFormat != "" {
+		return nil, nil, fmt.Errorf("ssh: signature algorithm %q isn't a key format; key is malformed and should be re-encoded with type %q",
+			algo, keyFormat)
+	}
+
 	return nil, nil, fmt.Errorf("ssh: unknown key algorithm: %v", algo)
 }
 
@@ -191,9 +197,10 @@ func ParseKnownHosts(in []byte) (marker string, hosts []string, pubKey PublicKey
 	return "", nil, nil, "", nil, io.EOF
 }
 
-// ParseAuthorizedKey parses a public key from an authorized_keys
+// ParseAuthorizedKey parses a public key from an authorized_keys file used in
-// file used in OpenSSH according to the sshd(8) manual page.
+// OpenSSH according to the sshd(8) manual page. Invalid lines are ignored.
 func ParseAuthorizedKey(in []byte) (out PublicKey, comment string, options []string, rest []byte, err error) {
+	var lastErr error
 	for len(in) > 0 {
 		end := bytes.IndexByte(in, '\n')
 		if end != -1 {
@@ -222,6 +229,8 @@ func ParseAuthorizedKey(in []byte) (out PublicKey, comment string, options []str
 
 		if out, comment, err = parseAuthorizedKey(in[i:]); err == nil {
 			return out, comment, options, rest, nil
+		} else {
+			lastErr = err
 		}
 
 		// No key type recognised. Maybe there's an options field at
@@ -264,12 +273,18 @@ func ParseAuthorizedKey(in []byte) (out PublicKey, comment string, options []str
 		if out, comment, err = parseAuthorizedKey(in[i:]); err == nil {
 			options = candidateOptions
 			return out, comment, options, rest, nil
+		} else {
+			lastErr = err
 		}
 
 		in = rest
 		continue
 	}
 
+	if lastErr != nil {
+		return nil, "", nil, nil, fmt.Errorf("ssh: no key found; last parsing error for ignored line: %w", lastErr)
+	}
+
 	return nil, "", nil, nil, errors.New("ssh: no key found")
 }
 
@@ -395,11 +410,11 @@ func NewSignerWithAlgorithms(signer AlgorithmSigner, algorithms []string) (Multi
 	}
 
 	for _, algo := range algorithms {
-		if !contains(supportedAlgos, algo) {
+		if !slices.Contains(supportedAlgos, algo) {
 			return nil, fmt.Errorf("ssh: algorithm %q is not supported for key type %q",
 				algo, signer.PublicKey().Type())
 		}
-		if !contains(signerAlgos, algo) {
+		if !slices.Contains(signerAlgos, algo) {
 			return nil, fmt.Errorf("ssh: algorithm %q is restricted for the provided signer", algo)
 		}
 	}
@@ -454,6 +469,12 @@ func parseRSA(in []byte) (out PublicKey, rest []byte, err error) {
 		return nil, nil, err
 	}
 
+	// 8192 bits is also the maximum RSA key size accepted by crypto/tls for
+	// signature verification:
+	// https://github.com/golang/go/blob/69801b25/src/crypto/tls/handshake_client.go#L1096
+	if w.N.BitLen() > 8192 {
+		return nil, nil, errors.New("ssh: rsa modulus too large")
+	}
 	if w.E.BitLen() > 24 {
 		return nil, nil, errors.New("ssh: exponent too large")
 	}
@@ -486,10 +507,13 @@ func (r *rsaPublicKey) Marshal() []byte {
 
 func (r *rsaPublicKey) Verify(data []byte, sig *Signature) error {
 	supportedAlgos := algorithmsForKeyFormat(r.Type())
-	if !contains(supportedAlgos, sig.Format) {
+	if !slices.Contains(supportedAlgos, sig.Format) {
 		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, r.Type())
 	}
-	hash := hashFuncs[sig.Format]
+	hash, err := hashFunc(sig.Format)
+	if err != nil {
+		return err
+	}
 	h := hash.New()
 	h.Write(data)
 	digest := h.Sum(nil)
@@ -556,6 +580,24 @@ func checkDSAParams(param *dsa.Parameters) error {
 		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
 }
 
@@ -578,6 +620,14 @@ func parseDSA(in []byte) (out PublicKey, rest []byte, err error) {
 		return nil, nil, err
 	}
 
+	// The public value Y must be a non-zero element of the group, i.e.
+	// strictly between 0 and P. crypto/dsa.Verify does not range-check Y,
+	// so we reject out-of-range values here to prevent a maliciously
+	// oversized Y from slowing verification.
+	if w.Y.Sign() <= 0 || w.Y.Cmp(w.P) >= 0 {
+		return nil, nil, errors.New("ssh: DSA public value Y out of range")
+	}
+
 	key := &dsaPublicKey{
 		Parameters: param,
 		Y:          w.Y,
@@ -606,7 +656,11 @@ func (k *dsaPublicKey) Verify(data []byte, sig *Signature) error {
 	if sig.Format != k.Type() {
 		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type())
 	}
-	h := hashFuncs[sig.Format].New()
+	hash, err := hashFunc(sig.Format)
+	if err != nil {
+		return err
+	}
+	h := hash.New()
 	h.Write(data)
 	digest := h.Sum(nil)
 
@@ -651,7 +705,11 @@ func (k *dsaPrivateKey) SignWithAlgorithm(rand io.Reader, data []byte, algorithm
 		return nil, fmt.Errorf("ssh: unsupported signature algorithm %s", algorithm)
 	}
 
-	h := hashFuncs[k.PublicKey().Type()].New()
+	hash, err := hashFunc(k.PublicKey().Type())
+	if err != nil {
+		return nil, err
+	}
+	h := hash.New()
 	h.Write(data)
 	digest := h.Sum(nil)
 	r, s, err := dsa.Sign(rand, k.PrivateKey, digest)
@@ -801,8 +859,11 @@ func (k *ecdsaPublicKey) Verify(data []byte, sig *Signature) error {
 	if sig.Format != k.Type() {
 		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type())
 	}
-
+	hash, err := hashFunc(sig.Format)
-	h := hashFuncs[sig.Format].New()
+	if err != nil {
+		return err
+	}
+	h := hash.New()
 	h.Write(data)
 	digest := h.Sum(nil)
 
@@ -840,11 +901,25 @@ type skFields struct {
 	Counter uint32
 }
 
+// flagUserPresence is the "user present" bit (UP) in the SK signature
+// flags, matching the FIDO CTAP2 authenticatorData UP flag. See
+// openssh/PROTOCOL.u2f.
+const flagUserPresence = 0x01
+
+// errSKMissingUserPresence is returned by SK key Verify methods when
+// the signature does not assert user presence and the key was not
+// marked as no-touch-required.
+var errSKMissingUserPresence = errors.New("ssh: signature missing required user presence flag")
+
 type skECDSAPublicKey struct {
 	// application is a URL-like string, typically "ssh:" for SSH.
 	// see openssh/PROTOCOL.u2f for details.
 	application string
 	ecdsa.PublicKey
+	// noTouchRequired, when true, disables the default user-presence
+	// check in Verify. It is set by skKeyWithoutUP on a clone of the
+	// key, never on an instance shared across authentication attempts.
+	noTouchRequired bool
 }
 
 func (k *skECDSAPublicKey) Type() string {
@@ -905,8 +980,11 @@ func (k *skECDSAPublicKey) Verify(data []byte, sig *Signature) error {
 	if sig.Format != k.Type() {
 		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type())
 	}
-
+	hash, err := hashFunc(sig.Format)
-	h := hashFuncs[sig.Format].New()
+	if err != nil {
+		return err
+	}
+	h := hash.New()
 	h.Write([]byte(k.application))
 	appDigest := h.Sum(nil)
 
@@ -927,6 +1005,10 @@ func (k *skECDSAPublicKey) Verify(data []byte, sig *Signature) error {
 		return err
 	}
 
+	if skf.Flags&flagUserPresence == 0 && !k.noTouchRequired {
+		return errSKMissingUserPresence
+	}
+
 	blob := struct {
 		ApplicationDigest []byte `ssh:"rest"`
 		Flags             byte
@@ -960,6 +1042,10 @@ type skEd25519PublicKey struct {
 	// see openssh/PROTOCOL.u2f for details.
 	application string
 	ed25519.PublicKey
+	// noTouchRequired, when true, disables the default user-presence
+	// check in Verify. It is set by skKeyWithoutUP on a clone of the
+	// key, never on an instance shared across authentication attempts.
+	noTouchRequired bool
 }
 
 func (k *skEd25519PublicKey) Type() string {
@@ -1009,7 +1095,11 @@ func (k *skEd25519PublicKey) Verify(data []byte, sig *Signature) error {
 		return fmt.Errorf("invalid size %d for Ed25519 public key", l)
 	}
 
-	h := hashFuncs[sig.Format].New()
+	hash, err := hashFunc(sig.Format)
+	if err != nil {
+		return err
+	}
+	h := hash.New()
 	h.Write([]byte(k.application))
 	appDigest := h.Sum(nil)
 
@@ -1030,6 +1120,10 @@ func (k *skEd25519PublicKey) Verify(data []byte, sig *Signature) error {
 		return err
 	}
 
+	if skf.Flags&flagUserPresence == 0 && !k.noTouchRequired {
+		return errSKMissingUserPresence
+	}
+
 	blob := struct {
 		ApplicationDigest []byte `ssh:"rest"`
 		Flags             byte
@@ -1112,11 +1206,14 @@ func (s *wrappedSigner) SignWithAlgorithm(rand io.Reader, data []byte, algorithm
 		algorithm = s.pubKey.Type()
 	}
 
-	if !contains(s.Algorithms(), algorithm) {
+	if !slices.Contains(s.Algorithms(), algorithm) {
 		return nil, fmt.Errorf("ssh: unsupported signature algorithm %q for key format %q", algorithm, s.pubKey.Type())
 	}
 
-	hashFunc := hashFuncs[algorithm]
+	hashFunc, err := hashFunc(algorithm)
+	if err != nil {
+		return nil, err
+	}
 	var digest []byte
 	if hashFunc != 0 {
 		h := hashFunc.New()
@@ -1451,6 +1548,7 @@ type openSSHEncryptedPrivateKey struct {
 	NumKeys      uint32
 	PubKey       []byte
 	PrivKeyBlock []byte
+	Rest         []byte `ssh:"rest"`
 }
 
 type openSSHPrivateKey struct {

ssh/keys_test.go

@@ -12,6 +12,7 @@ import (
 	"crypto/elliptic"
 	"crypto/rand"
 	"crypto/rsa"
+	"crypto/sha256"
 	"crypto/x509"
 	"encoding/base64"
 	"encoding/hex"
@@ -19,6 +20,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"math/big"
 	"reflect"
 	"strings"
 	"testing"
@@ -59,6 +61,17 @@ func TestKeyMarshalParse(t *testing.T) {
 	}
 }
 
+func TestParsePublicKeyWithSigningAlgoAsKeyFormat(t *testing.T) {
+	key := []byte(`rsa-sha2-256 AAAADHJzYS1zaGEyLTI1NgAAAAMBAAEAAAEBAJ7qMyjLXEJCCJmRknuCLo0uPi5GrPY5pQYr84lhlN8Gor5KVL2LKYCW4e70r5xzj7SrHHSCft1FMlYg1KDO9xrprJh733kQqAPWETmSuH0EfRtGtcH6EarKyVxk6As076/yNiiMKVBtG0RPa1L7FviTfcYK4vnCCVrbv3RmA5CCzuG5BSMbRLxzVb4Ri3p8jhxYT8N4QGe/2yqvJLys5vQ9szpZR3tcFp3DJIVZhBRfR6LnoY23XZniAAMQaUVBX86dXQ++dNwAwZSXSt9Og+AniOCiBYqhNVa5n3DID/H7YtEtG+CbZr3r2KD3fv8AfSLRar4XOp8rsRdD31h/kr8=`)
+	_, _, _, _, err := ParseAuthorizedKey(key)
+	if err == nil {
+		t.Fatal("parsing a public key using a signature algorithm as the key format succeeded unexpectedly")
+	}
+	if !strings.Contains(err.Error(), `signature algorithm "rsa-sha2-256" isn't a key format`) {
+		t.Errorf(`got %v, expected 'signature algorithm "rsa-sha2-256" isn't a key format'`, err)
+	}
+}
+
 func TestUnsupportedCurves(t *testing.T) {
 	raw, err := ecdsa.GenerateKey(elliptic.P224(), rand.Reader)
 	if err != nil {
@@ -205,6 +218,20 @@ func TestParseRSAPrivateKey(t *testing.T) {
 	}
 }
 
+func TestParseRSAModulusTooLarge(t *testing.T) {
+	rsa16384 := "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAIAQC0vyqtnpzMZ8Th6gv1t3+7dDVd2X+7MwjqKe08/wrKZaIuCAHX7jglC8FdHfiOcPhLHAreSJLZGXiSzCTUExbp9Zdt7tHluKMQxZCnbk02V89ggc4KpptQqfcmjMNgrEPF4PGJBe3eSYu9m7A1ptm0buWxaKtA17O1c2q2CVNYmuajSUAfi8+AZcdyRAX8eqga3u77DEj4O+CCuNA908NYv9Pc7SbaCwCgX3FXh7MvlaYcruTk529psNk1SK6uwBNak3CLRrXUBo5yTO7cCO0gmlvd8SwtY5mPaDLLCJa+Ed2t9OCt8HCPrdkH3aiQBTP3k/Iofy3NRv+/1lenJP1qWB2rnyagoj+osrLc6m8PRd7GBje7KdO6nyY1D+q1MvX4zV1qNQfD+38N6PixVX1MGKw72sD+oLCDjHKS24BHfnfaE7f8n+Alp2mxnSz9tYqsN3JXrbbwblzH8YFOz9MMKkTY5lQNQFoKdTHoPVXBqcMlGQGgC/kkH9TH110MDE3L+Z0i9kG53QLcHNVC0cJzo6X77PQF1WoS33Ssf1s21kUB6fe/5G2L2Tuy635ingtnQMUazwJMli+y/3U7QqqcuJzITbLw/zozRzbqFRE4HHOyGkJSptraH4/3cjmYro8JL20A7EUDiXxmn+z+eoxaBWaEP2Rs5LH0ocrwYmBmSUIrPy4e5ESlRRVuv+prNUB1pYGnFZUI9HRRFxRFg+SxXZZp4mq8jzroRLZFAqKY1/eDgsCGoV1HG3QW1t0jGNkv8BL/Zpz7Hhmt0lRr7rVN+PJaTQx8NNUJZ/l7nMXp/+7aTbkyI8PiNyemko0+joDrkBWdcK0vi8Du6k3oQRBUsJ0aM0iPxMWQq/oYyHqpf6revycYTUdOGeckGWXuXLNRIZQ/PsKuw/teqDaBkkMKaQH2oXWMsacL6WDu5VYUQidOtaTgHX8AKVHF/vobTQfw7HgPKlyRN41dAX+YIjRABYoqU7M2MYPuoPYbqzTz7iLZyFP8FCJ3dRQBTWSeer/s+Ih6Ev1EsznVmAw9SKb5q8QCSYk5mMugUTDVETOQo10CGAF6094/PcJRXgag/uWs4k+13c+/HaeNzrHQyqzWnf9bFFHIvs7Wqov9k+nWv/TwSGplkyBk4bHfhEZNbl+b6T8sZXsv8mTT+INzKT4DCVZ5a/G+NQ6Xo26Aa6Se5DOdzdXOLZ7yIhOi+olip8AOXIIFLb7Vee1+q7Ri6ScUJEKxdEvec5EceXEtWs0U4AnuHgiH0ewJSX9yUp8T4ImCzu00JhTMOH2nXU3PJuGgZgrDifNWXGpFruIBjHWRKpESpy+9HPGoNoxSO/hzSfuM5LKvwX+I96cMK5OC+fKsBh59cMpU4YnqFNh59ZP/kaMDxAXgrVku5s9oB3Rgc7t1rfm6dqycBiwn4QnYJpk7M+gzAbrF/nty8y84ajNdhINXgMgvv3JLC5YTqznBPm3koHSOEF8f4xtCZtzjNN6jNjX8gEvxoRpC9Z+X15c8XBSFyDMBoi0FMDor619XJKgTxNiOYmeH/DLhKEb8MIaug8IFu34FKbG81IsWD+zwA1A5xqXEVlgsfEOcML+Oe2rulkpwQBWnsmY+f/Z80004Mytreo/ME2TDuPJPOi15D0j0CbwG7xzE8qrn0EomBE9mrwH3uuH7df3lzx1HiLAmh2s4MO5R64AoWeAPQW9lWZPzp+2dNgk+0qWpoEsMN+r91yWxUZHgeoC+GJKs13LItH32sGInyUrquMYQjEh44fAEFrMREcS4A7l+875GUmWC6i2MSLyvtAzuPS2IV0t9GU0ooH8cfG5JUeDnsJcVanJTR+XuXPetM+cDyGFTGri3lsCndE9maLgs9iDHtJxzKUBUUakaIPLsXtZD51cS4jhSbbHuzgC21BRtnBhCE2phVYbz4Tj0t90wBmemBaP2eVwv9p4s/JJAHEELvV7k+Gro4FozOoC2WBdqdTPDFB00la08O6ADBdjd2el2pRA7HCTG6v3qwA6RQJfm4UHOXaFYhhiNngxHB4VHZMvpd+YMEqNmtYOb4lzWwI13iHU0Rh0Sj4IaY9EwEy/KjR5dc2DjWGj11SFFCP1uG24fccF+LhtdMNDItI1mBxfaeRelYlsCZwtbbVLnuVQ5izuTzXa48x7CBaHnD3i09BZCuQITLX4d7KkD6CLWWTHrc5onLFJKxRF/p5AEFoqtN3vP9CsLXSYNKxFV5UbxAY5TnAoLFCCo0WbgvtAV77jWSbru9Oq/7ORN9smog4zNuYBZE1uXjxM2xszDduOym7+CxwpJMc7XPknt2XwiANaf2QANMMMH6lmnjTH1RVR7oH4+ts4xVcsdiO/QOlMp+Th9/KIMYyUevR18vHbs+88uxzIG28/58xLZTs6rZc71g9mGw9Q21ugL2sfTc7e0VDMnAmdg+92s2RXQMvkmx+oRc+IsFqgOZzjYcTmnJxZaXsoIsydDVcTalgmhK6/dD0grPLaGgaeXMEw2hN8p8seAHrGRW8+6WBD63NBYaAG0/zwuGOCHUo/BeG9bz39Hsz9Yvs5KvJiLhmM5K+8RlnxIY329REqdFZVyuXyy0NpDueFQelnd0j47Quc7GJGX3QycJiKpLolMtDnpnjgYOvdfycM+JEMZGwpLsBBE8R6vJ3RVczT6DdMtpVQ4l7kOzsPSYlp4qAv5fiqUboyv5eP7G7MOD/qSUwBnMS1p9Vm4Wr8B9w=="
+	_, _, _, _, err := ParseAuthorizedKey([]byte(rsa16384))
+
+	if err == nil {
+		t.Fatal("ParseAuthorizedKey accepted a 16384-bit modulus; expected it to be rejected")
+	}
+
+	expectedError := "rsa modulus too large"
+	if !strings.Contains(err.Error(), expectedError) {
+		t.Errorf("unexpected error message: got %q, want substring %q", err.Error(), expectedError)
+	}
+}
+
 func TestParseECPrivateKey(t *testing.T) {
 	key := testPrivateKeys["ecdsa"]
 
@@ -260,6 +287,21 @@ func TestParseEncryptedPrivateKeysWithPassphrase(t *testing.T) {
 	}
 }
 
+func TestParseEncryptedPrivateKeysWithUnsupportedCiphers(t *testing.T) {
+	for _, tt := range testdata.UnsupportedCipherData {
+		t.Run(tt.Name, func(t *testing.T) {
+			_, err := ParsePrivateKeyWithPassphrase(tt.PEMBytes, []byte(tt.EncryptionKey))
+			if err == nil {
+				t.Fatalf("expected 'unknown cipher' error for %q, got nil", tt.Name)
+				// If this cipher is now supported, remove it from testdata.UnsupportedCipherData
+			}
+			if !strings.Contains(err.Error(), "unknown cipher") {
+				t.Errorf("wanted 'unknown cipher' error, got %v", err.Error())
+			}
+		})
+	}
+}
+
 func TestParseEncryptedPrivateKeysWithIncorrectPassphrase(t *testing.T) {
 	pem := testdata.PEMEncryptedKeys[0].PEMBytes
 	for i := 0; i < 4096; i++ {
@@ -330,6 +372,72 @@ func TestMarshalParsePublicKey(t *testing.T) {
 	}
 }
 
+func TestParseDSAHugeQ(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)
+
+	rawKey := struct {
+		P, Q, G, Y *big.Int
+	}{
+		P: P,
+		Q: Q,
+		G: G,
+		Y: Y,
+	}
+
+	inputBytes := Marshal(&rawKey)
+
+	_, _, err := parseDSA(inputBytes)
+	if err == nil {
+		t.Fatal("parseDSA accepted a DSA key with large Q")
+	}
+
+	expectedError := "ssh: 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 TestParseDSAYOutOfRange(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) {
+			rawKey := struct {
+				P, Q, G, Y *big.Int
+			}{P: P, Q: Q, G: G, Y: tc.Y}
+
+			_, _, err := parseDSA(Marshal(&rawKey))
+			if err == nil {
+				t.Fatalf("parseDSA 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 TestMarshalPrivateKey(t *testing.T) {
 	tests := []struct {
 		name string
@@ -734,6 +842,296 @@ func TestSKKeys(t *testing.T) {
 	}
 }
 
+// skTestHarness builds SK-formatted signatures over a fixed payload
+// using a caller-supplied signing function, letting tests vary the UP
+// flag byte without duplicating the wire-format scaffolding.
+type skTestHarness struct {
+	format      string
+	application string
+	data        []byte
+	// sign takes the SHA-256 digest of the marshalled SK blob and
+	// returns the value to embed in Signature.Blob. For ECDSA keys the
+	// helper feeds the digest to ecdsa.Sign; for ed25519 the helper
+	// feeds the raw marshalled blob to ed25519.Sign.
+	signDigest func(digest []byte) []byte
+	signBlob   func(blob []byte) []byte
+}
+
+func (h skTestHarness) sign(t *testing.T, flags byte) *Signature {
+	t.Helper()
+	hsh := sha256.New()
+	hsh.Write([]byte(h.application))
+	appDigest := hsh.Sum(nil)
+
+	hsh.Reset()
+	hsh.Write(h.data)
+	dataDigest := hsh.Sum(nil)
+
+	var counter uint32 = 1
+	blob := struct {
+		ApplicationDigest []byte `ssh:"rest"`
+		Flags             byte
+		Counter           uint32
+		MessageDigest     []byte `ssh:"rest"`
+	}{appDigest, flags, counter, dataDigest}
+	marshalled := Marshal(blob)
+
+	var sigBlob []byte
+	if h.signDigest != nil {
+		hsh.Reset()
+		hsh.Write(marshalled)
+		sigBlob = h.signDigest(hsh.Sum(nil))
+	} else {
+		sigBlob = h.signBlob(marshalled)
+	}
+
+	return &Signature{
+		Format: h.format,
+		Blob:   sigBlob,
+		Rest: Marshal(struct {
+			Flags   byte
+			Counter uint32
+		}{flags, counter}),
+	}
+}
+
+func TestSKUserPresence(t *testing.T) {
+	ecKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	h := skTestHarness{
+		format:      "sk-ecdsa-sha2-nistp256@openssh.com",
+		application: "ssh:",
+		data:        []byte("test data"),
+		signDigest: func(digest []byte) []byte {
+			r, s, err := ecdsa.Sign(rand.Reader, ecKey, digest)
+			if err != nil {
+				t.Fatal(err)
+			}
+			return Marshal(struct{ R, S *big.Int }{r, s})
+		},
+	}
+
+	pk := &skECDSAPublicKey{
+		application: h.application,
+		PublicKey:   ecKey.PublicKey,
+	}
+
+	// Valid signature with UP=1 should pass.
+	if err := pk.Verify(h.data, h.sign(t, flagUserPresence)); err != nil {
+		t.Errorf("Verify failed with UP=1: %v", err)
+	}
+
+	// Valid signature with UP=0 should fail with the user-presence sentinel.
+	sigNoUP := h.sign(t, 0)
+	if err := pk.Verify(h.data, sigNoUP); !errors.Is(err, errSKMissingUserPresence) {
+		t.Errorf("expected errSKMissingUserPresence, got: %v", err)
+	}
+
+	// UV set but UP clear must still fail: we only waive UP, never UV-only.
+	if err := pk.Verify(h.data, h.sign(t, 0x04)); !errors.Is(err, errSKMissingUserPresence) {
+		t.Errorf("UV-only (flags=0x04): expected errSKMissingUserPresence, got: %v", err)
+	}
+
+	// With noTouchRequired, UP=0 passes; UP=1+UV=1 also passes.
+	pk.noTouchRequired = true
+	if err := pk.Verify(h.data, sigNoUP); err != nil {
+		t.Errorf("Verify with noTouchRequired failed: %v", err)
+	}
+	if err := pk.Verify(h.data, h.sign(t, flagUserPresence|0x04)); err != nil {
+		t.Errorf("Verify UP|UV with noTouchRequired failed: %v", err)
+	}
+}
+
+func TestSKKeyWithoutUP(t *testing.T) {
+	ecKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	edPub, _, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	skEC := &skECDSAPublicKey{PublicKey: ecKey.PublicKey}
+	skED := &skEd25519PublicKey{PublicKey: edPub}
+	certEC := &Certificate{Key: &skECDSAPublicKey{PublicKey: ecKey.PublicKey}}
+	certED := &Certificate{Key: &skEd25519PublicKey{PublicKey: edPub}}
+	rsaKey, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		t.Fatal(err)
+	}
+	rsaPub, err := NewPublicKey(&rsaKey.PublicKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+	certRSA := &Certificate{Key: rsaPub}
+
+	// SK raw keys: return a clone with the flag set, original untouched.
+	gotEC := skKeyWithoutUP(skEC)
+	if gotEC == skEC {
+		t.Error("skECDSAPublicKey: expected a clone, got the original pointer")
+	}
+	if !gotEC.(*skECDSAPublicKey).noTouchRequired {
+		t.Error("skECDSAPublicKey clone: noTouchRequired not set")
+	}
+	if skEC.noTouchRequired {
+		t.Error("skECDSAPublicKey: original mutated")
+	}
+
+	gotED := skKeyWithoutUP(skED)
+	if gotED == skED {
+		t.Error("skEd25519PublicKey: expected a clone, got the original pointer")
+	}
+	if !gotED.(*skEd25519PublicKey).noTouchRequired {
+		t.Error("skEd25519PublicKey clone: noTouchRequired not set")
+	}
+	if skED.noTouchRequired {
+		t.Error("skEd25519PublicKey: original mutated")
+	}
+
+	// Certificate wrapping SK: return a clone of the cert with a cloned
+	// SK key inside. Neither the original cert nor the original inner
+	// key must be mutated.
+	originalInnerEC := certEC.Key
+	gotCertEC := skKeyWithoutUP(certEC)
+	if gotCertEC == certEC {
+		t.Error("*Certificate(SK ecdsa): expected a clone, got the original pointer")
+	}
+	if got := gotCertEC.(*Certificate).Key.(*skECDSAPublicKey); !got.noTouchRequired {
+		t.Error("*Certificate(SK ecdsa): inner clone missing noTouchRequired")
+	}
+	if certEC.Key != originalInnerEC {
+		t.Error("*Certificate(SK ecdsa): original cert's Key pointer mutated")
+	}
+	if originalInnerEC.(*skECDSAPublicKey).noTouchRequired {
+		t.Error("*Certificate(SK ecdsa): original inner key mutated")
+	}
+
+	gotCertED := skKeyWithoutUP(certED)
+	if gotCertED == certED {
+		t.Error("*Certificate(SK ed25519): expected a clone, got the original pointer")
+	}
+	if got := gotCertED.(*Certificate).Key.(*skEd25519PublicKey); !got.noTouchRequired {
+		t.Error("*Certificate(SK ed25519): inner clone missing noTouchRequired")
+	}
+
+	// Non-SK key inside a cert: return original unchanged (nothing to clone).
+	if got := skKeyWithoutUP(certRSA); got != certRSA {
+		t.Error("*Certificate(RSA): expected the original pointer back")
+	}
+
+	// Plain non-SK key: return original unchanged.
+	if got := skKeyWithoutUP(rsaPub); got != rsaPub {
+		t.Error("rsaPublicKey: expected the original pointer back")
+	}
+
+	// Pathological: *Certificate whose Key is itself a *Certificate.
+	// The SSH cert format forbids this and parseCert rejects it, but
+	// a Go caller can still construct such a value. skKeyWithoutUP
+	// must not recurse into it (or panic); it returns the input
+	// unchanged. This also defends against a hypothetical cycle built
+	// from hand-constructed Certificate pointers.
+	nestedCert := &Certificate{Key: &Certificate{Key: skEC}}
+	if got := skKeyWithoutUP(nestedCert); got != nestedCert {
+		t.Error("*Certificate wrapping *Certificate: expected the original pointer back")
+	}
+	selfCycle := &Certificate{}
+	selfCycle.Key = selfCycle
+	if got := skKeyWithoutUP(selfCycle); got != selfCycle {
+		t.Error("self-referential *Certificate: expected the original pointer back")
+	}
+}
+
+func TestNoTouchAllowed(t *testing.T) {
+	ecKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	sk := &skECDSAPublicKey{PublicKey: ecKey.PublicKey}
+	certNoExt := &Certificate{Key: sk}
+	certOptOut := &Certificate{
+		Key:         sk,
+		Permissions: Permissions{Extensions: map[string]string{"no-touch-required": ""}},
+	}
+	// Non-empty value: OpenSSH writes "" but any value must be accepted
+	// because the check is presence-only.
+	certOptOutNonEmpty := &Certificate{
+		Key:         sk,
+		Permissions: Permissions{Extensions: map[string]string{"no-touch-required": "yes"}},
+	}
+	// no-touch-required belongs in Extensions, never CriticalOptions.
+	// Putting it in CriticalOptions must NOT be treated as opt-out.
+	certCritOnly := &Certificate{
+		Key:         sk,
+		Permissions: Permissions{CriticalOptions: map[string]string{"no-touch-required": ""}},
+	}
+
+	permsEmpty := &Permissions{}
+	permsOptOut := &Permissions{Extensions: map[string]string{"no-touch-required": ""}}
+	permsCritOnly := &Permissions{CriticalOptions: map[string]string{"no-touch-required": ""}}
+
+	cases := []struct {
+		name  string
+		pub   PublicKey
+		perms *Permissions
+		want  bool
+	}{
+		{"nil perms, no cert", sk, nil, false},
+		{"empty perms, no cert", sk, permsEmpty, false},
+		{"perms opt-out, raw key", sk, permsOptOut, true},
+		{"nil perms, cert opt-out", certOptOut, nil, true},
+		{"nil perms, cert opt-out non-empty value", certOptOutNonEmpty, nil, true},
+		{"nil perms, cert no ext", certNoExt, nil, false},
+		{"perms opt-out, cert no ext", certNoExt, permsOptOut, true},
+		{"empty perms, cert opt-out", certOptOut, permsEmpty, true},
+		// Negative controls: CriticalOptions must not waive UP.
+		{"critical-options only, raw key", sk, permsCritOnly, false},
+		{"critical-options only, cert", certCritOnly, nil, false},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := noTouchAllowed(tc.pub, tc.perms); got != tc.want {
+				t.Errorf("noTouchAllowed = %v, want %v", got, tc.want)
+			}
+		})
+	}
+}
+
+func TestSKUserPresenceEd25519(t *testing.T) {
+	pub, priv, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	h := skTestHarness{
+		format:      "sk-ssh-ed25519@openssh.com",
+		application: "ssh:",
+		data:        []byte("test data"),
+		signBlob: func(blob []byte) []byte {
+			return ed25519.Sign(priv, blob)
+		},
+	}
+
+	pk := &skEd25519PublicKey{
+		application: h.application,
+		PublicKey:   pub,
+	}
+
+	if err := pk.Verify(h.data, h.sign(t, flagUserPresence)); err != nil {
+		t.Errorf("Verify failed with UP=1: %v", err)
+	}
+	sigNoUP := h.sign(t, 0)
+	if err := pk.Verify(h.data, sigNoUP); !errors.Is(err, errSKMissingUserPresence) {
+		t.Errorf("expected errSKMissingUserPresence, got: %v", err)
+	}
+	pk.noTouchRequired = true
+	if err := pk.Verify(h.data, sigNoUP); err != nil {
+		t.Errorf("Verify with noTouchRequired failed: %v", err)
+	}
+}
+
 func TestNewSignerWithAlgos(t *testing.T) {
 	algorithSigner, ok := testSigners["rsa"].(AlgorithmSigner)
 	if !ok {

ssh/knownhosts/knownhosts.go

@@ -160,8 +160,13 @@ func (db *hostKeyDB) IsHostAuthority(remote ssh.PublicKey, address string) bool
 
 // IsRevoked can be used as a callback in ssh.CertChecker
 func (db *hostKeyDB) IsRevoked(key *ssh.Certificate) bool {
-	_, ok := db.revoked[string(key.Marshal())]
+	if _, ok := db.revoked[string(key.Marshal())]; ok {
-	return ok
+		return true
+	}
+	if _, ok := db.revoked[string(key.SignatureKey.Marshal())]; ok {
+		return true
+	}
+	return false
 }
 
 const markerCert = "@cert-authority"

ssh/knownhosts/knownhosts_test.go

@@ -6,6 +6,8 @@ package knownhosts
 
 import (
 	"bytes"
+	"crypto/ed25519"
+	"crypto/rand"
 	"fmt"
 	"net"
 	"reflect"
@@ -272,7 +274,45 @@ func TestWildcardMatch(t *testing.T) {
 	}
 }
 
-// TODO(hanwen): test coverage for certificates.
+func TestRevokedCA(t *testing.T) {
+	_, caPriv, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	caSigner, err := ssh.NewSignerFromKey(caPriv)
+	if err != nil {
+		t.Fatal(err)
+	}
+	caKey := caSigner.PublicKey()
+
+	_, hostPriv, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	hostKey, err := ssh.NewPublicKey(hostPriv.Public())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cert := &ssh.Certificate{
+		CertType:        ssh.HostCert,
+		Key:             hostKey,
+		ValidBefore:     ssh.CertTimeInfinity,
+		ValidPrincipals: []string{"server.org"},
+	}
+	if err := cert.SignCert(rand.Reader, caSigner); err != nil {
+		t.Fatal(err)
+	}
+
+	caLine := "ssh-ed25519 " + serialize(caKey)[len("ssh-ed25519 "):]
+	knownHostsData := "@revoked server.org " + caLine + "\n" +
+		"@cert-authority server.org " + caLine + "\n"
+	db := testDB(t, knownHostsData)
+
+	if !db.IsRevoked(cert) {
+		t.Error("IsRevoked returned false for certificate signed by revoked CA")
+	}
+}
 
 const testHostname = "hostname"
 

ssh/mac.go

@@ -7,11 +7,13 @@ package ssh
 // Message authentication support
 
 import (
+	"crypto/fips140"
 	"crypto/hmac"
 	"crypto/sha1"
 	"crypto/sha256"
 	"crypto/sha512"
 	"hash"
+	"slices"
 )
 
 type macMode struct {
@@ -46,23 +48,37 @@ func (t truncatingMAC) Size() int {
 
 func (t truncatingMAC) BlockSize() int { return t.hmac.BlockSize() }
 
-var macModes = map[string]*macMode{
+// macModes defines the supported MACs. MACs not included are not supported
-	HMACSHA512ETM: {64, true, func(key []byte) hash.Hash {
+// and will not be negotiated, even if explicitly configured. When FIPS mode is
+// enabled, only FIPS-approved algorithms are included.
+var macModes = map[string]*macMode{}
+
+func init() {
+	macModes[HMACSHA512ETM] = &macMode{64, true, func(key []byte) hash.Hash {
 		return hmac.New(sha512.New, key)
-	}},
+	}}
-	HMACSHA256ETM: {32, true, func(key []byte) hash.Hash {
+	macModes[HMACSHA256ETM] = &macMode{32, true, func(key []byte) hash.Hash {
 		return hmac.New(sha256.New, key)
-	}},
+	}}
-	HMACSHA512: {64, false, func(key []byte) hash.Hash {
+	macModes[HMACSHA512] = &macMode{64, false, func(key []byte) hash.Hash {
 		return hmac.New(sha512.New, key)
-	}},
+	}}
-	HMACSHA256: {32, false, func(key []byte) hash.Hash {
+	macModes[HMACSHA256] = &macMode{32, false, func(key []byte) hash.Hash {
 		return hmac.New(sha256.New, key)
-	}},
+	}}
-	HMACSHA1: {20, false, func(key []byte) hash.Hash {
+
+	if fips140.Enabled() {
+		defaultMACs = slices.DeleteFunc(defaultMACs, func(algo string) bool {
+			_, ok := macModes[algo]
+			return !ok
+		})
+		return
+	}
+
+	macModes[HMACSHA1] = &macMode{20, false, func(key []byte) hash.Hash {
 		return hmac.New(sha1.New, key)
-	}},
+	}}
-	InsecureHMACSHA196: {20, false, func(key []byte) hash.Hash {
+	macModes[InsecureHMACSHA196] = &macMode{20, false, func(key []byte) hash.Hash {
 		return truncatingMAC{12, hmac.New(sha1.New, key)}
-	}},
+	}}
 }

ssh/messages.go

@@ -792,7 +792,7 @@ func marshalString(to []byte, s []byte) []byte {
 	return to[len(s):]
 }
 
-var bigIntType = reflect.TypeOf((*big.Int)(nil))
+var bigIntType = reflect.TypeFor[*big.Int]()
 
 // Decode a packet into its corresponding message.
 func decode(packet []byte) (interface{}, error) {

ssh/messages_test.go

@@ -257,7 +257,7 @@ func TestDecode(t *testing.T) {
 	userAuthSuccess, err := decode([]byte{msgUserAuthSuccess})
 	if err != nil {
 		t.Errorf("error decoding userAuthSuccessMsg")
-	} else if reflect.TypeOf(userAuthSuccess) != reflect.TypeOf((*userAuthSuccessMsg)(nil)) {
+	} else if _, ok := userAuthSuccess.(*userAuthSuccessMsg); !ok {
 		t.Errorf("error decoding userAuthSuccessMsg, unexpected %T", userAuthSuccess)
 	}
 }

ssh/mux.go

@@ -91,9 +91,10 @@ type mux struct {
 
 	incomingChannels chan NewChannel
 
-	globalSentMu     sync.Mutex
+	globalSentMu      sync.Mutex
-	globalResponses  chan interface{}
+	globalSentPending atomic.Bool
-	incomingRequests chan *Request
+	globalResponses   chan interface{}
+	incomingRequests  chan *Request
 
 	errCond *sync.Cond
 	err     error
@@ -141,6 +142,24 @@ func (m *mux) SendRequest(name string, wantReply bool, payload []byte) (bool, []
 	if wantReply {
 		m.globalSentMu.Lock()
 		defer m.globalSentMu.Unlock()
+
+		// Open the gate so that responses arriving while this request is in
+		// flight are allowed to reach globalResponses. Any response arriving
+		// while no request is pending is dropped by handleGlobalPacket.
+		m.globalSentPending.Store(true)
+		defer m.globalSentPending.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 <-m.globalResponses:
+			default:
+				break drain
+			}
+		}
 	}
 
 	if err := m.sendMessage(globalRequestMsg{
@@ -267,7 +286,16 @@ func (m *mux) handleGlobalPacket(packet []byte) error {
 			mux:       m,
 		}
 	case *globalRequestSuccessMsg, *globalRequestFailureMsg:
-		m.globalResponses <- msg
+		// Drop responses that arrive when no SendRequest is waiting, to
+		// prevent a malicious peer from staging responses for a future
+		// caller.
+		if !m.globalSentPending.Load() {
+			return nil
+		}
+		select {
+		case m.globalResponses <- msg:
+		default:
+		}
 	default:
 		panic(fmt.Sprintf("not a global message %#v", msg))
 	}

ssh/mux_test.go

@@ -825,6 +825,50 @@ func TestMuxChannelWindowDeferredUpdates(t *testing.T) {
 	}
 }
 
+func TestMuxChannelRejectRemovesFromMux(t *testing.T) {
+	serverMux, clientMux := muxPair()
+	defer serverMux.Close()
+	defer clientMux.Close()
+
+	var wg sync.WaitGroup
+	t.Cleanup(wg.Wait)
+	wg.Add(1)
+
+	go func() {
+		defer wg.Done()
+
+		// The server waits for the channel creation request
+		newCh, ok := <-serverMux.incomingChannels
+		if !ok {
+			t.Error("failed to accept channel")
+			return
+		}
+		ch := newCh.(*channel)
+
+		if serverMux.chanList.getChan(ch.localId) == nil {
+			t.Errorf("channel %d is not in the chanList before Reject", ch.localId)
+		}
+
+		if err := ch.Reject(Prohibited, "rejecting this channel"); err != nil {
+			t.Errorf("Reject failed: %v", err)
+		}
+
+		if serverMux.chanList.getChan(ch.localId) != nil {
+			t.Errorf("channel %d is still in the chanList after Reject", ch.localId)
+		}
+	}()
+
+	_, _, err := clientMux.OpenChannel("test_leak", nil)
+
+	if err == nil {
+		t.Fatal("expected an error (channel rejected), but got nil")
+	}
+
+	if _, ok := err.(*OpenChannelError); !ok {
+		t.Errorf("expected *OpenChannelError, got: %T", err)
+	}
+}
+
 // Don't ship code with debug=true.
 func TestDebug(t *testing.T) {
 	if debugMux {
@@ -837,3 +881,488 @@ func TestDebug(t *testing.T) {
 		t.Error("transport debug switched on")
 	}
 }
+
+func TestMuxUnexpectedGlobalResponsesDiscarded(t *testing.T) {
+	clientPipe, serverPipe := memPipe()
+	client := newMux(clientPipe)
+	defer serverPipe.Close()
+	defer client.Close()
+
+	done := make(chan error, 1)
+	go func() {
+		// Send multiple unexpected global responses, this should not block the
+		// globalResponses channel.
+		for i := range 5 {
+			err := serverPipe.writePacket(Marshal(globalRequestSuccessMsg{
+				Data: []byte{byte(i)},
+			}))
+			if err != nil {
+				done <- fmt.Errorf("send success msg %d: %w", i, err)
+				return
+			}
+		}
+		for i := range 5 {
+			err := serverPipe.writePacket(Marshal(globalRequestFailureMsg{
+				Data: []byte{byte(i)},
+			}))
+			if err != nil {
+				done <- fmt.Errorf("send failure msg %d: %w", i, err)
+				return
+			}
+		}
+
+		// Now send a global request and wait for the response. This
+		// verifies the mux is still processing packets.
+		err := serverPipe.writePacket(Marshal(globalRequestMsg{
+			Type:      "keepalive@golang.org",
+			WantReply: true,
+			Data:      nil,
+		}))
+		if err != nil {
+			done <- fmt.Errorf("send global request: %w", err)
+			return
+		}
+
+		packet, err := serverPipe.readPacket()
+		if err != nil {
+			done <- fmt.Errorf("read packet: %w", err)
+			return
+		}
+		decoded, err := decode(packet)
+		if err != nil {
+			done <- fmt.Errorf("decode: %w", err)
+			return
+		}
+		switch decoded.(type) {
+		case *globalRequestSuccessMsg, *globalRequestFailureMsg:
+			// Expected response
+		default:
+			done <- fmt.Errorf("unexpected packet type: %T", decoded)
+			return
+		}
+		done <- nil
+	}()
+
+	// Handle the incoming request from the server and reply
+	req, ok := <-client.incomingRequests
+	if !ok {
+		t.Fatal("incomingRequests channel closed unexpectedly")
+	}
+	if req.Type != "keepalive@golang.org" {
+		t.Fatalf("unexpected request type: %s", req.Type)
+	}
+	if err := req.Reply(true, nil); err != nil {
+		t.Fatalf("Reply: %v", err)
+	}
+
+	if err := <-done; err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestMuxConcurrentGlobalRequests(t *testing.T) {
+	clientMux, serverMux := muxPair()
+	defer serverMux.Close()
+	defer clientMux.Close()
+
+	const numRequests = 50
+
+	serverDone := make(chan struct{})
+	go func() {
+		defer close(serverDone)
+		for r := range serverMux.incomingRequests {
+			if r.WantReply {
+				replyData := append([]byte("reply:"), r.Payload...)
+				r.Reply(true, replyData)
+			}
+		}
+	}()
+
+	var clientWg sync.WaitGroup
+	clientWg.Add(numRequests)
+
+	errCh := make(chan error, numRequests)
+
+	for i := range numRequests {
+		go func(id int) {
+			defer clientWg.Done()
+
+			payloadStr := fmt.Sprintf("req-%d", id)
+			payload := []byte(payloadStr)
+
+			// This call blocks until the globalSentMu is acquired.
+			// The mutex ensures that even with many concurrent attempts,
+			// the "drain" and "send" logic happens atomically per request.
+			ok, data, err := clientMux.SendRequest("echo", true, payload)
+			if err != nil {
+				errCh <- fmt.Errorf("req %d error: %v", id, err)
+				return
+			}
+			if !ok {
+				errCh <- fmt.Errorf("req %d failed (want success)", id)
+				return
+			}
+
+			expected := "reply:" + payloadStr
+			if string(data) != expected {
+				errCh <- fmt.Errorf("req %d mismatch: got %q, want %q", id, string(data), expected)
+			}
+		}(i)
+	}
+
+	clientWg.Wait()
+	close(errCh)
+
+	for err := range errCh {
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	clientMux.Close()
+	<-serverDone
+}
+
+func TestMuxGlobalResponseDroppedWhenIdle(t *testing.T) {
+	clientPipe, serverPipe := memPipe()
+	clientMux := newMux(clientPipe)
+	defer serverPipe.Close()
+	defer clientMux.Close()
+
+	errCh := make(chan error, 1)
+	go func() {
+		// Send a spurious response while no SendRequest is pending.
+		if err := serverPipe.writePacket(Marshal(globalRequestSuccessMsg{
+			Data: []byte("spurious"),
+		})); err != nil {
+			errCh <- fmt.Errorf("send spurious: %w", err)
+			return
+		}
+		// Follow with a global request; once the client observes this on
+		// incomingRequests, the mux loop has necessarily processed (and
+		// dropped) the prior spurious response.
+		if err := serverPipe.writePacket(Marshal(globalRequestMsg{
+			Type:      "sync@example.com",
+			WantReply: false,
+		})); err != nil {
+			errCh <- fmt.Errorf("send sync request: %w", err)
+			return
+		}
+		errCh <- nil
+	}()
+
+	if err := <-errCh; err != nil {
+		t.Fatal(err)
+	}
+
+	req, ok := <-clientMux.incomingRequests
+	if !ok {
+		t.Fatal("incomingRequests closed unexpectedly")
+	}
+	if req.Type != "sync@example.com" {
+		t.Fatalf("unexpected sync request type %q", req.Type)
+	}
+
+	// The spurious response preceded the sync request, so by now the mux
+	// loop has processed it. The pending-gate must have caused it to be
+	// dropped rather than buffered.
+	if n := len(clientMux.globalResponses); n != 0 {
+		t.Fatalf("globalResponses buffer should be empty after idle drop, has %d entries", n)
+	}
+}
+
+func TestMuxStaleResponseDrained(t *testing.T) {
+	// Simulate a stale response sitting in globalResponses (e.g. a response
+	// that slipped in through the pending-gate on a prior SendRequest that
+	// exited without consuming it). The drain step in the next SendRequest
+	// must discard it so the caller receives the correct reply.
+	clientMux, serverMux := muxPair()
+	defer serverMux.Close()
+	defer clientMux.Close()
+
+	clientMux.globalResponses <- &globalRequestSuccessMsg{Data: []byte("stale")}
+
+	serverDone := make(chan struct{})
+	go func() {
+		defer close(serverDone)
+		for req := range serverMux.incomingRequests {
+			if req.WantReply {
+				req.Reply(true, append([]byte("reply:"), req.Payload...))
+			}
+		}
+	}()
+
+	ok, data, err := clientMux.SendRequest("test", true, []byte("hello"))
+	if err != nil {
+		t.Fatalf("request failed: %v", err)
+	}
+	if !ok {
+		t.Fatal("expected success response")
+	}
+	if string(data) != "reply:hello" {
+		t.Fatalf("got %q, want %q (drain did not remove stale response)", data, "reply:hello")
+	}
+
+	clientMux.Close()
+	<-serverDone
+}
+
+func TestMuxGlobalResponseAcceptedWhilePending(t *testing.T) {
+	// Positive control: when a SendRequest is actually pending, the
+	// response must be delivered (the gate is open).
+	clientMux, serverMux := muxPair()
+	defer serverMux.Close()
+	defer clientMux.Close()
+
+	serverDone := make(chan struct{})
+	go func() {
+		defer close(serverDone)
+		for req := range serverMux.incomingRequests {
+			if req.WantReply {
+				req.Reply(true, []byte("pong"))
+			}
+		}
+	}()
+
+	ok, data, err := clientMux.SendRequest("ping", true, nil)
+	if err != nil {
+		t.Fatalf("SendRequest: %v", err)
+	}
+	if !ok || string(data) != "pong" {
+		t.Fatalf("unexpected response: ok=%v data=%q", ok, data)
+	}
+
+	clientMux.Close()
+	<-serverDone
+}
+
+func TestChannelUnexpectedResponsesDiscarded(t *testing.T) {
+	// A malicious peer that spams channelRequestSuccess/Failure messages
+	// for an open, idle channel must not be able to stall the mux read
+	// loop by filling ch.msg. After the flood, the channel must still be
+	// usable: a subsequent legitimate SendRequest receives its reply.
+	clientMux, serverMux := muxPair()
+	defer serverMux.Close()
+	defer clientMux.Close()
+
+	serverRes := make(chan *channel, 1)
+	go func() {
+		newCh, ok := <-serverMux.incomingChannels
+		if !ok {
+			close(serverRes)
+			return
+		}
+		c, _, err := newCh.Accept()
+		if err != nil {
+			close(serverRes)
+			return
+		}
+		serverRes <- c.(*channel)
+	}()
+
+	clientCh, err := clientMux.openChannel("chan", nil)
+	if err != nil {
+		t.Fatalf("openChannel: %v", err)
+	}
+	serverCh := <-serverRes
+	if serverCh == nil {
+		t.Fatal("server did not accept channel")
+	}
+
+	// Spam many unsolicited success/failure responses. More than chanSize
+	// to ensure ch.msg would overflow without the pending-gate.
+	const spam = chanSize * 4
+	done := make(chan error, 1)
+	go func() {
+		for i := range spam {
+			if err := serverCh.ackRequest(i%2 == 0); err != nil {
+				done <- fmt.Errorf("ackRequest %d: %w", i, err)
+				return
+			}
+		}
+		// Echo any legitimate request back.
+		for req := range serverCh.incomingRequests {
+			if req.WantReply {
+				if err := req.Reply(true, append([]byte("reply:"), req.Payload...)); err != nil {
+					done <- fmt.Errorf("reply: %w", err)
+					return
+				}
+			}
+		}
+		done <- nil
+	}()
+
+	// If the flood had wedged the mux loop, this SendRequest would never
+	// receive a reply.
+	ok, err := clientCh.SendRequest("ping", true, []byte("hello"))
+	if err != nil {
+		t.Fatalf("SendRequest: %v", err)
+	}
+	if !ok {
+		t.Fatal("expected success reply")
+	}
+
+	// Clean up so the server goroutine can exit.
+	clientCh.Close()
+	serverCh.Close()
+	if err := <-done; err != nil {
+		if !errors.Is(err, io.EOF) {
+			t.Fatal(err)
+		}
+	}
+}
+
+func TestChannelConcurrentRequests(t *testing.T) {
+	writer, reader, mux := channelPair(t)
+	defer writer.Close()
+	defer reader.Close()
+	defer mux.Close()
+
+	serverDone := make(chan struct{})
+	go func() {
+		defer close(serverDone)
+		for req := range writer.incomingRequests {
+			if req.WantReply {
+				req.Reply(true, append([]byte("reply:"), req.Payload...))
+			}
+		}
+	}()
+
+	const numRequests = 50
+	var wg sync.WaitGroup
+	wg.Add(numRequests)
+	errCh := make(chan error, numRequests)
+
+	for i := 0; i < numRequests; i++ {
+		go func(id int) {
+			defer wg.Done()
+			payload := []byte(fmt.Sprintf("req-%d", id))
+			ok, err := reader.SendRequest("echo", true, payload)
+			if err != nil {
+				errCh <- fmt.Errorf("req %d: %v", id, err)
+				return
+			}
+			if !ok {
+				errCh <- fmt.Errorf("req %d: expected success", id)
+			}
+		}(i)
+	}
+
+	wg.Wait()
+	close(errCh)
+
+	for err := range errCh {
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	reader.Close()
+	writer.Close()
+	<-serverDone
+}
+
+func TestChannelResponseDroppedWhenIdle(t *testing.T) {
+	// A spurious response arriving while no SendRequest is pending must
+	// be dropped rather than buffered in ch.msg.
+	writer, reader, mux := channelPair(t)
+	defer writer.Close()
+	defer reader.Close()
+	defer mux.Close()
+
+	// Server sends an unsolicited reply, then a request so we can
+	// synchronise: once the client observes the request, the mux loop has
+	// necessarily processed (and dropped) the prior spurious reply.
+	errCh := make(chan error, 1)
+	go func() {
+		if err := writer.ackRequest(true); err != nil {
+			errCh <- err
+			return
+		}
+		if _, err := writer.SendRequest("sync", false, nil); err != nil {
+			errCh <- err
+			return
+		}
+		errCh <- nil
+	}()
+
+	req := <-reader.incomingRequests
+	if req.Type != "sync" {
+		t.Fatalf("unexpected request type %q", req.Type)
+	}
+
+	if n := len(reader.msg); n != 0 {
+		t.Fatalf("ch.msg should be empty after idle drop, has %d entries", n)
+	}
+
+	if err := <-errCh; err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestChannelStaleResponseDrained(t *testing.T) {
+	// Simulate a stale response sitting in ch.msg (e.g. a response that
+	// slipped through the pending-gate on a prior SendRequest that exited
+	// without consuming it). The drain step in the next SendRequest must
+	// discard it so the caller receives the correct reply.
+	writer, reader, mux := channelPair(t)
+	defer writer.Close()
+	defer reader.Close()
+	defer mux.Close()
+
+	reader.msg <- &channelRequestSuccessMsg{PeersID: reader.remoteId}
+
+	serverDone := make(chan struct{})
+	go func() {
+		defer close(serverDone)
+		for req := range writer.incomingRequests {
+			if req.WantReply {
+				req.Reply(false, append([]byte("nack:"), req.Payload...))
+			}
+		}
+	}()
+
+	ok, err := reader.SendRequest("test", true, []byte("hello"))
+	if err != nil {
+		t.Fatalf("SendRequest: %v", err)
+	}
+	// If the stale success had been consumed, ok would be true.
+	if ok {
+		t.Fatal("got stale success response; drain did not remove it")
+	}
+
+	reader.Close()
+	writer.Close()
+	<-serverDone
+}
+
+func TestChannelResponseAcceptedWhilePending(t *testing.T) {
+	// Positive control: when a SendRequest is actually pending, the
+	// response must be delivered (the gate is open).
+	writer, reader, mux := channelPair(t)
+	defer writer.Close()
+	defer reader.Close()
+	defer mux.Close()
+
+	serverDone := make(chan struct{})
+	go func() {
+		defer close(serverDone)
+		for req := range writer.incomingRequests {
+			if req.WantReply {
+				req.Reply(true, nil)
+			}
+		}
+	}()
+
+	ok, err := reader.SendRequest("ping", true, nil)
+	if err != nil {
+		t.Fatalf("SendRequest: %v", err)
+	}
+	if !ok {
+		t.Fatal("expected success")
+	}
+
+	reader.Close()
+	writer.Close()
+	<-serverDone
+}

ssh/server.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"slices"
 	"strings"
 )
 
@@ -33,16 +34,24 @@ type Permissions struct {
 	// or not supported.
 	CriticalOptions map[string]string
 
-	// Extensions are extra functionality that the server may
+	// Extensions are extra functionality that the server may offer on
-	// offer on authenticated connections. Lack of support for an
+	// authenticated connections. Lack of support for an extension does not
-	// extension does not preclude authenticating a user. Common
+	// preclude authenticating a user. Common extensions are
-	// extensions are "permit-agent-forwarding",
+	// "permit-agent-forwarding", "permit-X11-forwarding". In general the Go
-	// "permit-X11-forwarding". The Go SSH library currently does
+	// SSH library does not act on extensions and it is up to server
-	// not act on any extension, and it is up to server
+	// implementations to honor them; extensions can also be used to pass data
-	// implementations to honor them. Extensions can be used to
+	// from the authentication callbacks to the server application layer.
-	// pass data from the authentication callbacks to the server
+	//
-	// application layer.
+	// The one extension acted upon by this library is "no-touch-required",
+	// which applies only to security-key public keys
+	// (sk-ecdsa-sha2-nistp256@openssh.com and sk-ssh-ed25519@openssh.com).
+	// When present, it waives the default requirement that SK signatures
+	// assert user presence (i.e. a physical touch of the authenticator)
+	// during signature verification.
 	Extensions map[string]string
+
+	// ExtraData allows to store user defined data.
+	ExtraData map[any]any
 }
 
 type GSSAPIWithMICConfig struct {
@@ -80,6 +89,79 @@ type ServerPreAuthConn interface {
 	SendAuthBanner(string) error
 }
 
+// noTouchRequiredExtension is the extension name used by OpenSSH in
+// authorized_keys options and certificate extensions to mark keys
+// whose signatures do not need to assert user presence (touch). See
+// ssh-keygen(1) and sshd(8).
+const noTouchRequiredExtension = "no-touch-required"
+
+// noTouchAllowed reports whether the user presence requirement on
+// SK signatures should be waived for this authentication attempt. The
+// requirement is waived when the "no-touch-required" extension is
+// present either in the Permissions returned by the auth callback
+// (authorized_keys-level opt-out) or in the certificate's own
+// Extensions (CA-level opt-out), matching OpenSSH behavior. OpenSSH
+// reads the per-key opt-out only from cert Extensions and
+// authorized_keys options (never from CriticalOptions); we follow the
+// same rule.
+func noTouchAllowed(pubKey PublicKey, perms *Permissions) bool {
+	if perms != nil {
+		if _, ok := perms.Extensions[noTouchRequiredExtension]; ok {
+			return true
+		}
+	}
+	if cert, ok := pubKey.(*Certificate); ok {
+		if _, ok := cert.Extensions[noTouchRequiredExtension]; ok {
+			return true
+		}
+	}
+	return false
+}
+
+// skKeyWithoutUP returns a PublicKey equivalent to pubKey but whose
+// Verify accepts SK signatures with the user-presence flag clear. If
+// pubKey is not (and does not wrap) an SK key, pubKey is returned
+// unchanged. The returned value never mutates pubKey: for SK keys a
+// shallow copy is made so that the noTouchRequired flag is set only on
+// the clone.
+//
+// The implementation is iterative rather than recursive. When pubKey
+// is a *Certificate we unwrap exactly one level to look at the inner
+// key. The SSH cert format forbids Certificate.Key from being another
+// Certificate (parseCert rejects it), but nothing stops callers from
+// constructing such a value directly in Go; a recursive descent could
+// otherwise be driven to unbounded depth by a hand-crafted or cyclic
+// Certificate. A malformed input of that shape simply returns
+// unchanged here.
+func skKeyWithoutUP(pubKey PublicKey) PublicKey {
+	cert, isCert := pubKey.(*Certificate)
+	target := pubKey
+	if isCert {
+		target = cert.Key
+	}
+	var cloned PublicKey
+	switch k := target.(type) {
+	case *skECDSAPublicKey:
+		c := *k
+		c.noTouchRequired = true
+		cloned = &c
+	case *skEd25519PublicKey:
+		c := *k
+		c.noTouchRequired = true
+		cloned = &c
+	default:
+		// Not an SK key (or a pathological *Certificate wrapping
+		// another *Certificate): pubKey is already usable for Verify.
+		return pubKey
+	}
+	if !isCert {
+		return cloned
+	}
+	c := *cert
+	c.Key = cloned
+	return &c
+}
+
 // ServerConfig holds server specific configuration data.
 type ServerConfig struct {
 	// Config contains configuration shared between client and server.
@@ -126,6 +208,21 @@ type ServerConfig struct {
 	// Permissions.Extensions entry.
 	PublicKeyCallback func(conn ConnMetadata, key PublicKey) (*Permissions, error)
 
+	// VerifiedPublicKeyCallback, if non-nil, is called after a client
+	// successfully confirms having control over a key that was previously
+	// approved by PublicKeyCallback. The permissions object passed to the
+	// callback is the one returned by PublicKeyCallback for the given public
+	// key and its ownership is transferred to the callback. The returned
+	// Permissions object can be the same object, optionally modified, or a
+	// completely new object. If VerifiedPublicKeyCallback is non-nil,
+	// PublicKeyCallback is not allowed to return a PartialSuccessError, which
+	// can instead be returned by VerifiedPublicKeyCallback.
+	//
+	// VerifiedPublicKeyCallback does not affect which authentication methods
+	// are included in the list of methods that can be attempted by the client.
+	VerifiedPublicKeyCallback func(conn ConnMetadata, key PublicKey, permissions *Permissions,
+		signatureAlgorithm string) (*Permissions, error)
+
 	// KeyboardInteractiveCallback, if non-nil, is called when
 	// keyboard-interactive authentication is selected (RFC
 	// 4256). The client object's Challenge function should be
@@ -223,8 +320,10 @@ func (c *pubKeyCache) add(candidate cachedPubKey) {
 type ServerConn struct {
 	Conn
 
-	// If the succeeding authentication callback returned a
+	// If the succeeding authentication callback returned a non-nil Permissions
-	// non-nil Permissions pointer, it is stored here.
+	// pointer, it is stored here. These are the permissions from the final,
+	// successful authentication method. Permissions returned by callbacks that
+	// return PartialSuccessError are not preserved and must be nil.
 	Permissions *Permissions
 }
 
@@ -246,7 +345,7 @@ func NewServerConn(c net.Conn, config *ServerConfig) (*ServerConn, <-chan NewCha
 		fullConf.PublicKeyAuthAlgorithms = defaultPubKeyAuthAlgos
 	} else {
 		for _, algo := range fullConf.PublicKeyAuthAlgorithms {
-			if !contains(SupportedAlgorithms().PublicKeyAuths, algo) && !contains(InsecureAlgorithms().PublicKeyAuths, algo) {
+			if !slices.Contains(SupportedAlgorithms().PublicKeyAuths, algo) && !slices.Contains(InsecureAlgorithms().PublicKeyAuths, algo) {
 				c.Close()
 				return nil, nil, nil, fmt.Errorf("ssh: unsupported public key authentication algorithm %s", algo)
 			}
@@ -631,7 +730,7 @@ userAuthLoop:
 				return nil, parseError(msgUserAuthRequest)
 			}
 			algo := string(algoBytes)
-			if !contains(config.PublicKeyAuthAlgorithms, underlyingAlgo(algo)) {
+			if !slices.Contains(config.PublicKeyAuthAlgorithms, underlyingAlgo(algo)) {
 				authErr = fmt.Errorf("ssh: algorithm %q not accepted", algo)
 				break
 			}
@@ -652,6 +751,9 @@ userAuthLoop:
 				candidate.pubKeyData = pubKeyData
 				candidate.perms, candidate.result = authConfig.PublicKeyCallback(s, pubKey)
 				_, isPartialSuccessError := candidate.result.(*PartialSuccessError)
+				if isPartialSuccessError && config.VerifiedPublicKeyCallback != nil {
+					return nil, errors.New("ssh: invalid library usage: PublicKeyCallback must not return partial success when VerifiedPublicKeyCallback is defined")
+				}
 
 				if (candidate.result == nil || isPartialSuccessError) &&
 					candidate.perms != nil &&
@@ -695,7 +797,7 @@ userAuthLoop:
 				// ssh-rsa-cert-v01@openssh.com algorithm with ssh-rsa public
 				// key type. The algorithm and public key type must be
 				// consistent: both must be certificate algorithms, or neither.
-				if !contains(algorithmsForKeyFormat(pubKey.Type()), algo) {
+				if !slices.Contains(algorithmsForKeyFormat(pubKey.Type()), algo) {
 					authErr = fmt.Errorf("ssh: public key type %q not compatible with selected algorithm %q",
 						pubKey.Type(), algo)
 					break
@@ -705,7 +807,7 @@ userAuthLoop:
 				// algorithm name that corresponds to algo with
 				// sig.Format.  This is usually the same, but
 				// for certs, the names differ.
-				if !contains(config.PublicKeyAuthAlgorithms, sig.Format) {
+				if !slices.Contains(config.PublicKeyAuthAlgorithms, sig.Format) {
 					authErr = fmt.Errorf("ssh: algorithm %q not accepted", sig.Format)
 					break
 				}
@@ -715,13 +817,33 @@ userAuthLoop:
 				}
 
 				signedData := buildDataSignedForAuth(sessionID, userAuthReq, algo, pubKeyData)
-
+				// pubKey is reused below for VerifiedPublicKeyCallback and
-				if err := pubKey.Verify(signedData, sig); err != nil {
+				// must remain the key as presented by the client; derive a
+				// separate value for Verify that carries any applicable
+				// no-touch-required opt-out.
+				pubKeyForVerify := pubKey
+				if noTouchAllowed(pubKey, candidate.perms) {
+					pubKeyForVerify = skKeyWithoutUP(pubKey)
+				}
+				if err := pubKeyForVerify.Verify(signedData, sig); err != nil {
 					return nil, err
 				}
 
 				authErr = candidate.result
 				perms = candidate.perms
+				if authErr == nil && config.VerifiedPublicKeyCallback != nil {
+					// Only call VerifiedPublicKeyCallback after the key has been accepted
+					// and successfully verified. If authErr is non-nil, the key is not
+					// considered verified and the callback must not run.
+					perms, authErr = config.VerifiedPublicKeyCallback(s, pubKey, perms, algo)
+				}
+				if authErr == nil && perms != nil && perms.CriticalOptions != nil {
+					if saco := perms.CriticalOptions[sourceAddressCriticalOption]; saco != "" {
+						if err := checkSourceAddress(s.RemoteAddr(), saco); err != nil {
+							authErr = err
+						}
+					}
+				}
 			}
 		case "gssapi-with-mic":
 			if authConfig.GSSAPIWithMICConfig == nil {
@@ -796,6 +918,13 @@ userAuthLoop:
 		var failureMsg userAuthFailureMsg
 
 		if partialSuccess, ok := authErr.(*PartialSuccessError); ok {
+			// Permissions are not preserved between authentication steps. To
+			// avoid confusion about the final state of the connection, we
+			// disallow returning non-nil Permissions combined with
+			// PartialSuccessError.
+			if perms != nil {
+				return nil, errors.New("ssh: permissions must be nil when returning PartialSuccessError")
+			}
 			// After a partial success error we don't allow changing the user
 			// name and execute the NoClientAuthCallback.
 			partialSuccessReturned = true

ssh/server_test.go

@@ -6,9 +6,14 @@ package ssh
 
 import (
 	"bytes"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/sha256"
 	"errors"
 	"fmt"
 	"io"
+	"math/big"
 	"net"
 	"reflect"
 	"strings"
@@ -434,6 +439,472 @@ func TestPreAuthConnAndBanners(t *testing.T) {
 	}
 }
 
+func TestVerifiedPublicKeyCallback(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	extraKey := "extra"
+	extraDataString := "just a string"
+
+	serverConf := &ServerConfig{
+		VerifiedPublicKeyCallback: func(conn ConnMetadata, key PublicKey, permissions *Permissions, signatureAlgorithm string) (*Permissions, error) {
+			if permissions != nil && permissions.ExtraData != nil {
+				if !reflect.DeepEqual(map[any]any{extraKey: extraDataString}, permissions.ExtraData) {
+					t.Errorf("expected extra data: %v; got: %v", extraDataString, permissions.ExtraData)
+				}
+			} else {
+				t.Error("expected extra data is missing")
+			}
+			if signatureAlgorithm != KeyAlgoRSASHA256 {
+				t.Errorf("expected signature algorithm: %q; got: %q", KeyAlgoRSASHA256, signatureAlgorithm)
+			}
+			return permissions, nil
+		},
+		PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+			return &Permissions{ExtraData: map[any]any{extraKey: extraDataString}}, nil
+		},
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+
+	done := make(chan struct{})
+	go func() {
+		defer close(done)
+		conn, _, _, err := NewServerConn(c1, serverConf)
+		if err != nil {
+			t.Errorf("unexpected server error: %v", err)
+		}
+		if !reflect.DeepEqual(map[any]any{extraKey: extraDataString}, conn.Permissions.ExtraData) {
+			t.Errorf("expected extra data: %v; got: %v", extraDataString, conn.Permissions.ExtraData)
+		}
+	}()
+
+	clientConf := ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	_, _, _, err = NewClientConn(c2, "", &clientConf)
+	if err != nil {
+		t.Fatal(err)
+	}
+	<-done
+}
+
+func TestVerifiedPublicCallbackPartialSuccess(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	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{
+						PasswordCallback: func(conn ConnMetadata, password []byte) (*Permissions, error) {
+							if string(password) == clientPassword {
+								return nil, nil
+							}
+							return nil, nil
+						},
+					},
+				}
+			}
+			return nil, errors.New("invalid credentials")
+		},
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+
+	clientConf := ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+			Password(clientPassword),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	go NewServerConn(c1, serverConf)
+
+	_, _, _, err = NewClientConn(c2, "", &clientConf)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+}
+
+func TestVerifiedPublicKeyCallbackPwdAndKey(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	serverConf := &ServerConfig{
+		PasswordCallback: func(conn ConnMetadata, password []byte) (*Permissions, error) {
+			if string(password) == clientPassword {
+				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")
+						},
+					},
+				}
+			}
+			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, nil
+			}
+			return nil, errors.New("invalid credentials")
+		},
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+
+	clientConf := ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			Password(clientPassword),
+			PublicKeys(testSigners["rsa"]),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	go NewServerConn(c1, serverConf)
+
+	_, _, _, err = NewClientConn(c2, "", &clientConf)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+}
+
+func TestVerifiedPubKeyCallbackAuthMethods(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	serverConf := &ServerConfig{
+		PasswordCallback: func(conn ConnMetadata, password []byte) (*Permissions, error) {
+			return nil, nil
+		},
+		VerifiedPublicKeyCallback: func(conn ConnMetadata, key PublicKey, permissions *Permissions, signatureAlgorithm string) (*Permissions, error) {
+			if bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+				return nil, nil
+			}
+			return nil, errors.New("invalid credentials")
+		},
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+
+	clientConf := ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	go NewServerConn(c1, serverConf)
+
+	_, _, _, err = NewClientConn(c2, "", &clientConf)
+	if err == nil {
+		t.Fatal("client login succeed with only VerifiedPublicKeyCallback defined")
+	}
+}
+
+func TestVerifiedPubKeyCallbackError(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	serverConf := &ServerConfig{
+		PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+			return nil, nil
+		},
+		VerifiedPublicKeyCallback: func(conn ConnMetadata, key PublicKey, permissions *Permissions, signatureAlgorithm string) (*Permissions, error) {
+			return nil, errors.New("invalid credentials")
+		},
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+
+	clientConf := ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	go NewServerConn(c1, serverConf)
+
+	_, _, _, err = NewClientConn(c2, "", &clientConf)
+	if err == nil {
+		t.Fatal("client login succeed with VerifiedPublicKeyCallback returning an error")
+	}
+}
+
+func TestVerifiedPubKeyCallbackSourceAddress(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	serverConf := &ServerConfig{
+		PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+			return nil, nil
+		},
+		VerifiedPublicKeyCallback: func(conn ConnMetadata, key PublicKey, permissions *Permissions, signatureAlgorithm string) (*Permissions, error) {
+			return &Permissions{
+				CriticalOptions: map[string]string{
+					sourceAddressCriticalOption: "192.168.99.99",
+				},
+			}, nil
+		},
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+
+	clientConf := ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	go NewServerConn(c1, serverConf)
+
+	_, _, _, err = NewClientConn(c2, "", &clientConf)
+	if err == nil {
+		t.Fatal("client login succeed with VerifiedPublicKeyCallback returning mismatching source-address")
+	}
+}
+
+func TestVerifiedPublicCallbackPartialSuccessBadUsage(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	serverConf := &ServerConfig{
+		PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+			if bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+				// Returning PartialSuccessError is not permitted when
+				// VerifiedPublicKeyCallback is defined. This callback is
+				// invoked for both query requests and real authentications,
+				// while VerifiedPublicKeyCallback is only triggered if the
+				// client has proven control of the key.
+				return nil, &PartialSuccessError{
+					Next: ServerAuthCallbacks{
+						PasswordCallback: func(conn ConnMetadata, password []byte) (*Permissions, error) {
+							if string(password) == clientPassword {
+								return nil, nil
+							}
+							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{
+						PasswordCallback: func(conn ConnMetadata, password []byte) (*Permissions, error) {
+							if string(password) == clientPassword {
+								return nil, nil
+							}
+							return nil, nil
+						},
+					},
+				}
+			}
+			return nil, errors.New("invalid credentials")
+		},
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+
+	clientConf := ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+			Password(clientPassword),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	go NewServerConn(c1, serverConf)
+
+	_, _, _, err = NewClientConn(c2, "", &clientConf)
+	if err == nil {
+		t.Fatal("authentication succeeded with PartialSuccess returned from PublicKeyCallback and  VerifiedPublicKeyCallback defined")
+	}
+}
+
+func TestVerifiedPublicKeyCallbackOnError(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	var verifiedCallbackCalled bool
+
+	serverConf := &ServerConfig{
+		VerifiedPublicKeyCallback: func(conn ConnMetadata, key PublicKey, permissions *Permissions, signatureAlgorithm string) (*Permissions, error) {
+			verifiedCallbackCalled = true
+			return nil, nil
+		},
+		PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+			return nil, errors.New("invalid key")
+		},
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+
+	done := make(chan struct{})
+	go func() {
+		defer close(done)
+		NewServerConn(c1, serverConf)
+	}()
+
+	clientConf := ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	_, _, _, err = NewClientConn(c2, "", &clientConf)
+	if err == nil {
+		t.Fatal("authentication should fail")
+	}
+	<-done
+	if verifiedCallbackCalled {
+		t.Error("VerifiedPublicKeyCallback called after PublicKeyCallback returned an error")
+	}
+}
+
+func TestVerifiedPublicKeyCallbackOnly(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	serverConf := &ServerConfig{
+		VerifiedPublicKeyCallback: func(conn ConnMetadata, key PublicKey, permissions *Permissions, signatureAlgorithm string) (*Permissions, error) {
+			return nil, nil
+		},
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+	done := make(chan struct{})
+	go func() {
+		defer close(done)
+		NewServerConn(c1, serverConf)
+	}()
+
+	clientConf := ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	_, _, _, err = NewClientConn(c2, "", &clientConf)
+	if err == nil {
+		t.Fatal("authentication succeeded with only VerifiedPublicKeyCallback defined")
+	}
+	<-done
+}
+
+func TestPartialSuccessWithNonNilPerms(t *testing.T) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	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()) {
+				// Intentionally return non-nil Permissions along with a
+				// PartialSuccessError. Since permissions are reset between
+				// authentication steps, this constitutes invalid library usage
+				// and the server is expected to reject the connection.
+				return &Permissions{Extensions: map[string]string{"permit-port-forwarding": ""}}, &PartialSuccessError{
+					Next: ServerAuthCallbacks{
+						PasswordCallback: func(conn ConnMetadata, password []byte) (*Permissions, error) {
+							if string(password) == clientPassword {
+								return nil, nil
+							}
+							return nil, nil
+						},
+					},
+				}
+			}
+			return nil, errors.New("invalid credentials")
+		},
+	}
+	serverConf.AddHostKey(testSigners["rsa"])
+
+	clientConf := ClientConfig{
+		User: "user",
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+			Password(clientPassword),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	go NewServerConn(c1, serverConf)
+
+	_, _, _, err = NewClientConn(c2, "", &clientConf)
+	if err == nil {
+		t.Fatal("authentication succeeded unexpectedly; server should have rejected non-nil Permissions combined with PartialSuccessError")
+	}
+}
+
 type markerConn struct {
 	closed uint32
 	used   uint32
@@ -476,3 +947,126 @@ func (*markerConn) RemoteAddr() net.Addr { return nil }
 func (*markerConn) SetDeadline(t time.Time) error      { return nil }
 func (*markerConn) SetReadDeadline(t time.Time) error  { return nil }
 func (*markerConn) SetWriteDeadline(t time.Time) error { return nil }
+
+// skTestSigner is a Signer that produces SK-ECDSA signatures over
+// user-auth data, simulating a FIDO/U2F authenticator. The flags
+// byte (UP and other bits) is caller-controlled so tests can exercise
+// the server's user-presence enforcement and its opt-out paths. This
+// is test-only: the real Signer is hardware-backed.
+type skTestSigner struct {
+	priv        *ecdsa.PrivateKey
+	pub         PublicKey
+	flags       byte
+	application string
+}
+
+func (s *skTestSigner) PublicKey() PublicKey { return s.pub }
+
+func (s *skTestSigner) Sign(r io.Reader, data []byte) (*Signature, error) {
+	h := sha256.New()
+	h.Write([]byte(s.application))
+	appDigest := h.Sum(nil)
+	h.Reset()
+	h.Write(data)
+	dataDigest := h.Sum(nil)
+	var counter uint32 = 1
+	blob := struct {
+		ApplicationDigest []byte `ssh:"rest"`
+		Flags             byte
+		Counter           uint32
+		MessageDigest     []byte `ssh:"rest"`
+	}{appDigest, s.flags, counter, dataDigest}
+	h.Reset()
+	h.Write(Marshal(blob))
+	digest := h.Sum(nil)
+	x, y, err := ecdsa.Sign(r, s.priv, digest)
+	if err != nil {
+		return nil, err
+	}
+	return &Signature{
+		Format: KeyAlgoSKECDSA256,
+		Blob:   Marshal(struct{ R, S *big.Int }{x, y}),
+		Rest: Marshal(struct {
+			Flags   byte
+			Counter uint32
+		}{s.flags, counter}),
+	}, nil
+}
+
+// TestServerAuthSKUserPresence drives the full userAuthLoop with an SK
+// public-key client and verifies the server's wiring of the UP check
+// and its two opt-out paths: the per-key Permissions.Extensions route
+// and (via cert) the cert-level route. It also confirms that non-SK
+// clients are unaffected by the new code path.
+func TestServerAuthSKUserPresence(t *testing.T) {
+	userKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	skPub := &skECDSAPublicKey{application: "ssh:", PublicKey: userKey.PublicKey}
+
+	runAuth := func(t *testing.T, signer Signer, perms *Permissions) error {
+		t.Helper()
+		c1, c2, err := netPipe()
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer c1.Close()
+		defer c2.Close()
+
+		serverConf := &ServerConfig{
+			PublicKeyCallback: func(ConnMetadata, PublicKey) (*Permissions, error) {
+				return perms, nil
+			},
+		}
+		serverConf.AddHostKey(testSigners["ecdsa"])
+
+		serverErr := make(chan error, 1)
+		go func() {
+			_, _, _, err := NewServerConn(c1, serverConf)
+			serverErr <- err
+		}()
+
+		clientConf := &ClientConfig{
+			User:            "user",
+			Auth:            []AuthMethod{PublicKeys(signer)},
+			HostKeyCallback: InsecureIgnoreHostKey(),
+		}
+		_, _, _, clientErr := NewClientConn(c2, "", clientConf)
+		<-serverErr
+		return clientErr
+	}
+
+	optOut := &Permissions{Extensions: map[string]string{noTouchRequiredExtension: ""}}
+
+	t.Run("UP=1, default perms accepts", func(t *testing.T) {
+		s := &skTestSigner{priv: userKey, pub: skPub, flags: flagUserPresence, application: "ssh:"}
+		if err := runAuth(t, s, nil); err != nil {
+			t.Errorf("expected auth to succeed: %v", err)
+		}
+	})
+	t.Run("UP=0, default perms rejects", func(t *testing.T) {
+		s := &skTestSigner{priv: userKey, pub: skPub, flags: 0, application: "ssh:"}
+		if err := runAuth(t, s, nil); err == nil {
+			t.Error("expected auth to fail with UP=0")
+		}
+	})
+	t.Run("UP=0, perms opt-out accepts", func(t *testing.T) {
+		s := &skTestSigner{priv: userKey, pub: skPub, flags: 0, application: "ssh:"}
+		if err := runAuth(t, s, optOut); err != nil {
+			t.Errorf("expected auth to succeed with opt-out: %v", err)
+		}
+	})
+	t.Run("UP=0, perms CriticalOptions does NOT opt out", func(t *testing.T) {
+		s := &skTestSigner{priv: userKey, pub: skPub, flags: 0, application: "ssh:"}
+		critOnly := &Permissions{CriticalOptions: map[string]string{noTouchRequiredExtension: ""}}
+		if err := runAuth(t, s, critOnly); err == nil {
+			t.Error("no-touch-required in CriticalOptions must not waive UP")
+		}
+	})
+	t.Run("non-SK RSA signer unaffected", func(t *testing.T) {
+		if err := runAuth(t, testSigners["rsa"], nil); err != nil {
+			t.Errorf("plain RSA auth must still work: %v", err)
+		}
+	})
+}

ssh/ssh_gss.go

@@ -106,6 +106,13 @@ func parseGSSAPIPayload(payload []byte) (*userAuthRequestGSSAPI, error) {
 	if !ok {
 		return nil, errors.New("parse uint32 failed")
 	}
+	// Each ASN.1 encoded OID must have a minimum
+	// of 2 bytes; 64 maximum mechanisms is an
+	// arbitrary, but reasonable ceiling.
+	const maxMechs = 64
+	if n > maxMechs || int(n)*2 > len(rest) {
+		return nil, errors.New("invalid mechanism count")
+	}
 	s := &userAuthRequestGSSAPI{
 		N:    n,
 		OIDS: make([]asn1.ObjectIdentifier, n),
@@ -122,7 +129,6 @@ func parseGSSAPIPayload(payload []byte) (*userAuthRequestGSSAPI, error) {
 		if rest, err = asn1.Unmarshal(desiredMech, &s.OIDS[i]); err != nil {
 			return nil, err
 		}
-
 	}
 	return s, nil
 }

ssh/ssh_gss_test.go

@@ -17,6 +17,37 @@ func TestParseGSSAPIPayload(t *testing.T) {
 	}
 }
 
+func TestParseDubiousGSSAPIPayload(t *testing.T) {
+	for _, tc := range []struct {
+		name    string
+		payload []byte
+		wanterr bool
+	}{
+		{
+			"num mechanisms is unrealistic",
+			[]byte{0xFF, 0x00, 0x00, 0xFF,
+				0x00, 0x00, 0x00, 0x0b, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x12, 0x01, 0x02, 0x02},
+			true,
+		},
+		{
+			"num mechanisms greater than payload",
+			[]byte{0x00, 0x00, 0x00, 0x40, // 64, |rest| too small
+				0x00, 0x00, 0x00, 0x0b, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x12, 0x01, 0x02, 0x02},
+			true,
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			_, err := parseGSSAPIPayload(tc.payload)
+			if tc.wanterr && err == nil {
+				t.Errorf("got nil, want error")
+			}
+			if !tc.wanterr && err != nil {
+				t.Errorf("got %v, want nil", err)
+			}
+		})
+	}
+}
+
 func TestBuildMIC(t *testing.T) {
 	sessionID := []byte{134, 180, 134, 194, 62, 145, 171, 82, 119, 149, 254, 196, 125, 173, 177, 145, 187, 85, 53,
 		183, 44, 150, 219, 129, 166, 195, 19, 33, 209, 246, 175, 121}

ssh/streamlocal.go

@@ -44,7 +44,7 @@ func (c *Client) ListenUnix(socketPath string) (net.Listener, error) {
 	if !ok {
 		return nil, errors.New("ssh: streamlocal-forward@openssh.com request denied by peer")
 	}
-	ch := c.forwards.add(&net.UnixAddr{Name: socketPath, Net: "unix"})
+	ch := c.forwards.add("unix", socketPath)
 
 	return &unixListener{socketPath, c, ch}, nil
 }
@@ -96,7 +96,7 @@ func (l *unixListener) Accept() (net.Conn, error) {
 // Close closes the listener.
 func (l *unixListener) Close() error {
 	// this also closes the listener.
-	l.conn.forwards.remove(&net.UnixAddr{Name: l.socketPath, Net: "unix"})
+	l.conn.forwards.remove("unix", l.socketPath)
 	m := streamLocalChannelForwardMsg{
 		l.socketPath,
 	}

ssh/tcpip.go

@@ -11,6 +11,7 @@ import (
 	"io"
 	"math/rand"
 	"net"
+	"net/netip"
 	"strconv"
 	"strings"
 	"sync"
@@ -22,14 +23,21 @@ import (
 // the returned net.Listener. The listener must be serviced, or the
 // SSH connection may hang.
 // N must be "tcp", "tcp4", "tcp6", or "unix".
+//
+// If the address is a hostname, it is sent to the remote peer as-is, without
+// being resolved locally, and the Listener Addr method will return a zero IP.
 func (c *Client) Listen(n, addr string) (net.Listener, error) {
 	switch n {
 	case "tcp", "tcp4", "tcp6":
-		laddr, err := net.ResolveTCPAddr(n, addr)
+		host, portStr, err := net.SplitHostPort(addr)
 		if err != nil {
 			return nil, err
 		}
-		return c.ListenTCP(laddr)
+		port, err := strconv.ParseInt(portStr, 10, 32)
+		if err != nil {
+			return nil, err
+		}
+		return c.listenTCPInternal(host, int(port))
 	case "unix":
 		return c.ListenUnix(addr)
 	default:
@@ -102,15 +110,24 @@ func (c *Client) handleForwards() {
 // ListenTCP requests the remote peer open a listening socket
 // on laddr. Incoming connections will be available by calling
 // Accept on the returned net.Listener.
+//
+// ListenTCP accepts an IP address, to provide a hostname use [Client.Listen]
+// with "tcp", "tcp4", or "tcp6" network instead.
 func (c *Client) ListenTCP(laddr *net.TCPAddr) (net.Listener, error) {
 	c.handleForwardsOnce.Do(c.handleForwards)
 	if laddr.Port == 0 && isBrokenOpenSSHVersion(string(c.ServerVersion())) {
 		return c.autoPortListenWorkaround(laddr)
 	}
 
+	return c.listenTCPInternal(laddr.IP.String(), laddr.Port)
+}
+
+func (c *Client) listenTCPInternal(host string, port int) (net.Listener, error) {
+	c.handleForwardsOnce.Do(c.handleForwards)
+
 	m := channelForwardMsg{
-		laddr.IP.String(),
+		host,
-		uint32(laddr.Port),
+		uint32(port),
 	}
 	// send message
 	ok, resp, err := c.SendRequest("tcpip-forward", true, Marshal(&m))
@@ -123,20 +140,33 @@ func (c *Client) ListenTCP(laddr *net.TCPAddr) (net.Listener, error) {
 
 	// If the original port was 0, then the remote side will
 	// supply a real port number in the response.
-	if laddr.Port == 0 {
+	if port == 0 {
 		var p struct {
 			Port uint32
 		}
 		if err := Unmarshal(resp, &p); err != nil {
 			return nil, err
 		}
-		laddr.Port = int(p.Port)
+		port = int(p.Port)
 	}
+	// Construct a local address placeholder for the remote listener. If the
+	// original host is an IP address, preserve it so that Listener.Addr()
+	// reports the same IP. If the host is a hostname or cannot be parsed as an
+	// IP, fall back to IPv4zero. The port field is always set, even if the
+	// original port was 0, because in that case the remote server will assign
+	// one, allowing callers to determine which port was selected.
+	ip := net.IPv4zero
+	if parsed, err := netip.ParseAddr(host); err == nil {
+		ip = net.IP(parsed.AsSlice())
+	}
+	laddr := &net.TCPAddr{
+		IP:   ip,
+		Port: port,
+	}
+	addr := net.JoinHostPort(host, strconv.FormatInt(int64(port), 10))
+	ch := c.forwards.add("tcp", addr)
 
-	// Register this forward, using the port number we obtained.
+	return &tcpListener{laddr, addr, c, ch}, nil
-	ch := c.forwards.add(laddr)
-
-	return &tcpListener{laddr, c, ch}, nil
 }
 
 // forwardList stores a mapping between remote
@@ -149,8 +179,9 @@ type forwardList struct {
 // forwardEntry represents an established mapping of a laddr on a
 // remote ssh server to a channel connected to a tcpListener.
 type forwardEntry struct {
-	laddr net.Addr
+	addr    string // host:port or socket path
-	c     chan forward
+	network string // tcp or unix
+	c       chan forward
 }
 
 // forward represents an incoming forwarded tcpip connection. The
@@ -161,12 +192,13 @@ type forward struct {
 	raddr net.Addr   // the raddr of the incoming connection
 }
 
-func (l *forwardList) add(addr net.Addr) chan forward {
+func (l *forwardList) add(n, addr string) chan forward {
 	l.Lock()
 	defer l.Unlock()
 	f := forwardEntry{
-		laddr: addr,
+		addr:    addr,
-		c:     make(chan forward, 1),
+		network: n,
+		c:       make(chan forward, 1),
 	}
 	l.entries = append(l.entries, f)
 	return f.c
@@ -185,19 +217,20 @@ func parseTCPAddr(addr string, port uint32) (*net.TCPAddr, error) {
 	if port == 0 || port > 65535 {
 		return nil, fmt.Errorf("ssh: port number out of range: %d", port)
 	}
-	ip := net.ParseIP(string(addr))
+	ip, err := netip.ParseAddr(addr)
-	if ip == nil {
+	if err != nil {
 		return nil, fmt.Errorf("ssh: cannot parse IP address %q", addr)
 	}
-	return &net.TCPAddr{IP: ip, Port: int(port)}, nil
+	return &net.TCPAddr{IP: net.IP(ip.AsSlice()), Port: int(port)}, nil
 }
 
 func (l *forwardList) handleChannels(in <-chan NewChannel) {
 	for ch := range in {
 		var (
-			laddr net.Addr
+			addr    string
-			raddr net.Addr
+			network string
-			err   error
+			raddr   net.Addr
+			err     error
 		)
 		switch channelType := ch.ChannelType(); channelType {
 		case "forwarded-tcpip":
@@ -207,40 +240,34 @@ func (l *forwardList) handleChannels(in <-chan NewChannel) {
 				continue
 			}
 
-			// RFC 4254 section 7.2 specifies that incoming
+			// RFC 4254 section 7.2 specifies that incoming addresses should
-			// addresses should list the address, in string
+			// list the address that was connected, in string format. It is the
-			// format. It is implied that this should be an IP
+			// same address used in the tcpip-forward request. The originator
-			// address, as it would be impossible to connect to it
+			// address is an IP address instead.
-			// otherwise.
+			addr = net.JoinHostPort(payload.Addr, strconv.FormatUint(uint64(payload.Port), 10))
-			laddr, err = parseTCPAddr(payload.Addr, payload.Port)
+
-			if err != nil {
-				ch.Reject(ConnectionFailed, err.Error())
-				continue
-			}
 			raddr, err = parseTCPAddr(payload.OriginAddr, payload.OriginPort)
 			if err != nil {
 				ch.Reject(ConnectionFailed, err.Error())
 				continue
 			}
-
+			network = "tcp"
 		case "forwarded-streamlocal@openssh.com":
 			var payload forwardedStreamLocalPayload
 			if err = Unmarshal(ch.ExtraData(), &payload); err != nil {
 				ch.Reject(ConnectionFailed, "could not parse forwarded-streamlocal@openssh.com payload: "+err.Error())
 				continue
 			}
-			laddr = &net.UnixAddr{
+			addr = payload.SocketPath
-				Name: payload.SocketPath,
-				Net:  "unix",
-			}
 			raddr = &net.UnixAddr{
 				Name: "@",
 				Net:  "unix",
 			}
+			network = "unix"
 		default:
 			panic(fmt.Errorf("ssh: unknown channel type %s", channelType))
 		}
-		if ok := l.forward(laddr, raddr, ch); !ok {
+		if ok := l.forward(network, addr, raddr, ch); !ok {
 			// Section 7.2, implementations MUST reject spurious incoming
 			// connections.
 			ch.Reject(Prohibited, "no forward for address")
@@ -252,11 +279,11 @@ func (l *forwardList) handleChannels(in <-chan NewChannel) {
 
 // remove removes the forward entry, and the channel feeding its
 // listener.
-func (l *forwardList) remove(addr net.Addr) {
+func (l *forwardList) remove(n, addr string) {
 	l.Lock()
 	defer l.Unlock()
 	for i, f := range l.entries {
-		if addr.Network() == f.laddr.Network() && addr.String() == f.laddr.String() {
+		if n == f.network && addr == f.addr {
 			l.entries = append(l.entries[:i], l.entries[i+1:]...)
 			close(f.c)
 			return
@@ -274,11 +301,11 @@ func (l *forwardList) closeAll() {
 	l.entries = nil
 }
 
-func (l *forwardList) forward(laddr, raddr net.Addr, ch NewChannel) bool {
+func (l *forwardList) forward(n, addr string, raddr net.Addr, ch NewChannel) bool {
 	l.Lock()
 	defer l.Unlock()
 	for _, f := range l.entries {
-		if laddr.Network() == f.laddr.Network() && laddr.String() == f.laddr.String() {
+		if n == f.network && addr == f.addr {
 			f.c <- forward{newCh: ch, raddr: raddr}
 			return true
 		}
@@ -288,6 +315,7 @@ func (l *forwardList) forward(laddr, raddr net.Addr, ch NewChannel) bool {
 
 type tcpListener struct {
 	laddr *net.TCPAddr
+	addr  string
 
 	conn *Client
 	in   <-chan forward
@@ -314,13 +342,21 @@ func (l *tcpListener) Accept() (net.Conn, error) {
 
 // Close closes the listener.
 func (l *tcpListener) Close() error {
+	host, port, err := net.SplitHostPort(l.addr)
+	if err != nil {
+		return err
+	}
+	rport, err := strconv.ParseUint(port, 10, 32)
+	if err != nil {
+		return err
+	}
 	m := channelForwardMsg{
-		l.laddr.IP.String(),
+		host,
-		uint32(l.laddr.Port),
+		uint32(rport),
 	}
 
 	// this also closes the listener.
-	l.conn.forwards.remove(l.laddr)
+	l.conn.forwards.remove("tcp", l.addr)
 	ok, _, err := l.conn.SendRequest("cancel-tcpip-forward", true, Marshal(&m))
 	if err == nil && !ok {
 		err = errors.New("ssh: cancel-tcpip-forward failed")

ssh/test/agent_unix_test.go

@@ -24,9 +24,8 @@ func TestAgentForward(t *testing.T) {
 		t.Fatalf("Error adding key: %s", err)
 	}
 	if err := keyring.Add(agent.AddedKey{
-		PrivateKey:       testPrivateKeys["ecdsa"],
+		PrivateKey:   testPrivateKeys["ecdsa"],
-		ConfirmBeforeUse: true,
+		LifetimeSecs: 3600,
-		LifetimeSecs:     3600,
 	}); err != nil {
 		t.Fatalf("Error adding key with constraints: %s", err)
 	}

ssh/test/doc.go

@@ -4,4 +4,6 @@
 
 // Package test contains integration tests for the
 // golang.org/x/crypto/ssh package.
+//
+// Deprecated: this package is for internal use only.
 package test

ssh/test/forward_unix_test.go

@@ -51,6 +51,8 @@ func testPortForward(t *testing.T, n, listenAddr string) {
 		}
 	}()
 
+	// The forwarded address match the listen address because we run the tests
+	// on the same host.
 	forwardedAddr := sshListener.Addr().String()
 	netConn, err := net.Dial(n, forwardedAddr)
 	if err != nil {
@@ -111,6 +113,8 @@ func testPortForward(t *testing.T, n, listenAddr string) {
 }
 
 func TestPortForwardTCP(t *testing.T) {
+	testPortForward(t, "tcp", ":0")
+	testPortForward(t, "tcp", "[::]:0")
 	testPortForward(t, "tcp", "localhost:0")
 }
 

ssh/test/recording_client_test.go

@@ -251,7 +251,7 @@ func TestClientKeyExchanges(t *testing.T) {
 
 	var keyExchanges []string
 	for _, kex := range config.KeyExchanges {
-		// Exclude ecdh for now, to make them determistic we should use see a
+		// Exclude ecdh for now, to make them deterministic we should use see a
 		// stream of fixed bytes as the random source.
 		if !strings.HasPrefix(kex, "ecdh-") {
 			keyExchanges = append(keyExchanges, kex)

ssh/test/recording_server_test.go

@@ -232,7 +232,7 @@ func TestServerKeyExchanges(t *testing.T) {
 
 	var keyExchanges []string
 	for _, kex := range config.KeyExchanges {
-		// Exclude ecdh for now, to make them determistic we should use see a
+		// Exclude ecdh for now, to make them deterministic we should use see a
 		// stream of fixed bytes as the random source.
 		// Exclude ML-KEM because server side is not deterministic.
 		if !strings.HasPrefix(kex, "ecdh-") && !strings.HasPrefix(kex, "mlkem") {

ssh/testdata/keys.go

@@ -310,6 +310,53 @@ gbDGyT3bXMQtagvCwoW+/oMTKXiZP5jCJpEO8=
 	},
 }
 
+var UnsupportedCipherData = []struct {
+    Name string
+    EncryptionKey string
+    PEMBytes []byte
+} {
+	0: {
+		Name:              "ed25519-encrypted-chacha20-poly1305",
+		EncryptionKey:     "password",
+		PEMBytes: []byte(`-----BEGIN OPENSSH PRIVATE KEY-----
+b3BlbnNzaC1rZXktdjEAAAAAHWNoYWNoYTIwLXBvbHkxMzA1QG9wZW5zc2guY29tAAAABm
+JjcnlwdAAAABgAAAAQdPyPIjXDRAVHskY0yp9SWwAAAGQAAAABAAAAMwAAAAtzc2gtZWQy
+NTUxOQAAACBi6qXITEUrmNce/c2lfozxALlKH3o/6sll8G7wzl1lvQAAAJDNlW1sEkvnK0
+8EecF1vHdPk85yClbh3KkHv09mbGAX/Gk6cJpYEGgJSkO7OEF4kG9DVGGd17+TZbTnM4LD
+vYAJZExx2XLgJFEtHCVmJjYzwxx7yC7+s6u/XjrSlZS60RHunOPKyq+C+s48sejXvmX+t5
+0ZoVCI8aftT0ycis3gvLU9sCwJ2UnF6kAV226Z4g2aLkuJbgCDTEcYCRD64K1r
+-----END OPENSSH PRIVATE KEY-----
+`),
+	},
+	1: {
+		Name:              "ed25519-encrypted-aes128-gcm",
+		EncryptionKey:     "password",
+		PEMBytes: []byte(`-----BEGIN OPENSSH PRIVATE KEY-----
+b3BlbnNzaC1rZXktdjEAAAAAFmFlczEyOC1nY21Ab3BlbnNzaC5jb20AAAAGYmNyeXB0AA
+AAGAAAABBeMJIOqiyFwNCvDv6f8tQeAAAAZAAAAAEAAAAzAAAAC3NzaC1lZDI1NTE5AAAA
+IGYpUcb3tGp9kF6pppcUdq3EPMr85BaSUdhiXGbhS5YNAAAAkNBtMEu0UlLgToThuQc+4m
+/o0DfFIERu0sspQivn5RJHCtulVKfU9BMiEnF0+LOMOABMlYesgLOtoMxwm4ZCSWH54kZk
+vaFyyvvxY+RLDuWNQZCryffIA4+iLCUQR1EdxMDiJweKnGJuD64a+9xTJt47A3Vq4SYzji
+EuVmM0FqS8lbT2ynYSe3va0Qyw13jEO5qbtCuyG+C5GejL7kX4Z64=
+-----END OPENSSH PRIVATE KEY-----
+`),
+	},
+	2: {
+		Name:              "ed25519-encrypted-aes256-gcm",
+		EncryptionKey:     "password",
+		PEMBytes: []byte(`-----BEGIN OPENSSH PRIVATE KEY-----
+b3BlbnNzaC1rZXktdjEAAAAAFmFlczI1Ni1nY21Ab3BlbnNzaC5jb20AAAAGYmNyeXB0AA
+AAGAAAABBR1p3vH2Wr/HPL+q20L2rjAAAAZAAAAAEAAAAzAAAAC3NzaC1lZDI1NTE5AAAA
+IM3tT1xrAuOHcrBdoLRo/ojWZsAw2lHfF5hJgFEOts5MAAAAkH/YGrDhDw8u+F8e4P+84B
+tAzvp55Lf1Yl7y34BrVmqlWqw/7boqahOp6iYJHNpcuanzc5T6s7Z3wSSYodbY1uvFOfbj
+rtP6rIHQIY5J2C40WOYJN8IkZlkwDXwZY0qoE9699ZYmWdwsXRZ7QDhjd2W8ziyZBsttiB
+kv2ceuJMLT04TrKc2+RUkj4CQYnz7p8EkgZlUozx8wBSxKFGnkP7k=
+-----END OPENSSH PRIVATE KEY-----
+`),
+	},
+}
+
+
 // SKData contains a list of PubKeys backed by U2F/FIDO2 Security Keys and their test data.
 var SKData = []struct {
 	Name         string

ssh/transport.go

@@ -8,6 +8,7 @@ import (
 	"bufio"
 	"bytes"
 	"errors"
+	"fmt"
 	"io"
 	"log"
 )
@@ -254,6 +255,9 @@ var (
 // (to setup server->client keys) or clientKeys (for client->server keys).
 func newPacketCipher(d direction, algs DirectionAlgorithms, kex *kexResult) (packetCipher, error) {
 	cipherMode := cipherModes[algs.Cipher]
+	if cipherMode == nil {
+		return nil, fmt.Errorf("ssh: unsupported cipher %v", algs.Cipher)
+	}
 
 	iv := make([]byte, cipherMode.ivSize)
 	key := make([]byte, cipherMode.keySize)