go.mod: update golang.org/x dependencies

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

Change-Id: Ib391e4f2f09056cb025de97d5d8f2640859d9163
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/525335
Run-TryBot: Gopher Robot <gobot@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Gopher Robot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

acme/acme_test.go

@@ -354,11 +354,12 @@ func TestWaitAuthorization(t *testing.T) {
 		})
 	}
 	t.Run("context cancel", func(t *testing.T) {
-		ctx, cancel := context.WithTimeout(context.Background(), 200*time.Millisecond)
+		ctx, cancel := context.WithCancel(context.Background())
 		defer cancel()
 		_, err := runWaitAuthorization(ctx, t, func(w http.ResponseWriter, r *http.Request) {
 			w.Header().Set("Retry-After", "60")
 			fmt.Fprintf(w, `{"status":"pending"}`)
+			time.AfterFunc(1*time.Millisecond, cancel)
 		})
 		if err == nil {
 			t.Error("err is nil")
@@ -373,28 +374,14 @@ func runWaitAuthorization(ctx context.Context, t *testing.T, h http.HandlerFunc)
 		h(w, r)
 	}))
 	defer ts.Close()
-	type res struct {
-		authz *Authorization
-		err   error
+
+	client := &Client{
+		Key:          testKey,
+		DirectoryURL: ts.URL,
+		dir:          &Directory{},
+		KID:          "some-key-id", // set to avoid lookup attempt
 	}
-	ch := make(chan res, 1)
-	go func() {
-		client := &Client{
-			Key:          testKey,
-			DirectoryURL: ts.URL,
-			dir:          &Directory{},
-			KID:          "some-key-id", // set to avoid lookup attempt
-		}
-		a, err := client.WaitAuthorization(ctx, ts.URL)
-		ch <- res{a, err}
-	}()
-	select {
-	case <-time.After(3 * time.Second):
-		t.Fatal("WaitAuthorization took too long to return")
-	case v := <-ch:
-		return v.authz, v.err
-	}
-	panic("runWaitAuthorization: out of select")
+	return client.WaitAuthorization(ctx, ts.URL)
 }
 
 func TestRevokeAuthorization(t *testing.T) {

acme/autocert/autocert_test.go

@@ -427,18 +427,7 @@ func TestGetCertificate(t *testing.T) {
 
 			man.Client = &acme.Client{DirectoryURL: s.URL()}
 
-			var tlscert *tls.Certificate
-			var err error
-			done := make(chan struct{})
-			go func() {
-				tlscert, err = man.GetCertificate(tt.hello)
-				close(done)
-			}()
-			select {
-			case <-time.After(time.Minute):
-				t.Fatal("man.GetCertificate took too long to return")
-			case <-done:
-			}
+			tlscert, err := man.GetCertificate(tt.hello)
 			if tt.expectError != "" {
 				if err == nil {
 					t.Fatal("expected error, got certificate")
@@ -515,15 +504,12 @@ func TestGetCertificate_failedAttempt(t *testing.T) {
 	if _, err := man.GetCertificate(hello); err == nil {
 		t.Error("GetCertificate: err is nil")
 	}
-	select {
-	case <-time.After(5 * time.Second):
-		t.Errorf("took too long to remove the %q state", exampleCertKey)
-	case <-done:
-		man.stateMu.Lock()
-		defer man.stateMu.Unlock()
-		if v, exist := man.state[exampleCertKey]; exist {
-			t.Errorf("state exists for %v: %+v", exampleCertKey, v)
-		}
+
+	<-done
+	man.stateMu.Lock()
+	defer man.stateMu.Unlock()
+	if v, exist := man.state[exampleCertKey]; exist {
+		t.Errorf("state exists for %v: %+v", exampleCertKey, v)
 	}
 }
 
@@ -542,8 +528,9 @@ func TestRevokeFailedAuthz(t *testing.T) {
 		t.Fatal("expected GetCertificate to fail")
 	}
 
-	start := time.Now()
-	for time.Since(start) < 3*time.Second {
+	logTicker := time.NewTicker(3 * time.Second)
+	defer logTicker.Stop()
+	for {
 		authz, err := m.Client.GetAuthorization(context.Background(), ca.URL()+"/authz/0")
 		if err != nil {
 			t.Fatal(err)
@@ -551,10 +538,14 @@ func TestRevokeFailedAuthz(t *testing.T) {
 		if authz.Status == acme.StatusDeactivated {
 			return
 		}
+
+		select {
+		case <-logTicker.C:
+			t.Logf("still waiting on revocations")
+		default:
+		}
 		time.Sleep(50 * time.Millisecond)
 	}
-	t.Error("revocations took too long")
-
 }
 
 func TestHTTPHandlerDefaultFallback(t *testing.T) {

acme/rfc8555.go

@@ -117,7 +117,7 @@ func (c *Client) updateRegRFC(ctx context.Context, a *Account) (*Account, error)
 	return responseAccount(res)
 }
 
-// getGegRFC is equivalent to c.GetReg but for CAs implementing RFC 8555.
+// getRegRFC is equivalent to c.GetReg but for CAs implementing RFC 8555.
 // It expects c.Discover to have already been called.
 func (c *Client) getRegRFC(ctx context.Context) (*Account, error) {
 	req := json.RawMessage(`{"onlyReturnExisting": true}`)

acme/rfc8555_test.go

@@ -177,8 +177,7 @@ func TestRFC_postKID(t *testing.T) {
 	}))
 	defer ts.Close()
 
-	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
-	defer cancel()
+	ctx := context.Background()
 	cl := &Client{
 		Key:          testKey,
 		DirectoryURL: ts.URL,
@@ -316,8 +315,7 @@ func TestRFC_Register(t *testing.T) {
 	s.start()
 	defer s.close()
 
-	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
-	defer cancel()
+	ctx := context.Background()
 	cl := &Client{
 		Key:          testKeyEC,
 		DirectoryURL: s.url("/"),
@@ -454,8 +452,7 @@ func TestRFC_RegisterExternalAccountBinding(t *testing.T) {
 	s.start()
 	defer s.close()
 
-	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
-	defer cancel()
+	ctx := context.Background()
 	cl := &Client{
 		Key:          testKeyEC,
 		DirectoryURL: s.url("/"),
@@ -867,24 +864,13 @@ func testWaitOrderStatus(t *testing.T, okStatus string) {
 	s.start()
 	defer s.close()
 
-	var order *Order
-	var err error
-	done := make(chan struct{})
-	go func() {
-		cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")}
-		order, err = cl.WaitOrder(context.Background(), s.url("/orders/1"))
-		close(done)
-	}()
-	select {
-	case <-time.After(3 * time.Second):
-		t.Fatal("WaitOrder took too long to return")
-	case <-done:
-		if err != nil {
-			t.Fatalf("WaitOrder: %v", err)
-		}
-		if order.Status != okStatus {
-			t.Errorf("order.Status = %q; want %q", order.Status, okStatus)
-		}
+	cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")}
+	order, err := cl.WaitOrder(context.Background(), s.url("/orders/1"))
+	if err != nil {
+		t.Fatalf("WaitOrder: %v", err)
+	}
+	if order.Status != okStatus {
+		t.Errorf("order.Status = %q; want %q", order.Status, okStatus)
 	}
 }
 
@@ -909,30 +895,20 @@ func TestRFC_WaitOrderError(t *testing.T) {
 	s.start()
 	defer s.close()
 
-	var err error
-	done := make(chan struct{})
-	go func() {
-		cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")}
-		_, err = cl.WaitOrder(context.Background(), s.url("/orders/1"))
-		close(done)
-	}()
-	select {
-	case <-time.After(3 * time.Second):
-		t.Fatal("WaitOrder took too long to return")
-	case <-done:
-		if err == nil {
-			t.Fatal("WaitOrder returned nil error")
-		}
-		e, ok := err.(*OrderError)
-		if !ok {
-			t.Fatalf("err = %v (%T); want OrderError", err, err)
-		}
-		if e.OrderURL != s.url("/orders/1") {
-			t.Errorf("e.OrderURL = %q; want %q", e.OrderURL, s.url("/orders/1"))
-		}
-		if e.Status != StatusInvalid {
-			t.Errorf("e.Status = %q; want %q", e.Status, StatusInvalid)
-		}
+	cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")}
+	_, err := cl.WaitOrder(context.Background(), s.url("/orders/1"))
+	if err == nil {
+		t.Fatal("WaitOrder returned nil error")
+	}
+	e, ok := err.(*OrderError)
+	if !ok {
+		t.Fatalf("err = %v (%T); want OrderError", err, err)
+	}
+	if e.OrderURL != s.url("/orders/1") {
+		t.Errorf("e.OrderURL = %q; want %q", e.OrderURL, s.url("/orders/1"))
+	}
+	if e.Status != StatusInvalid {
+		t.Errorf("e.Status = %q; want %q", e.Status, StatusInvalid)
 	}
 }
 
@@ -972,8 +948,7 @@ func TestRFC_CreateOrderCert(t *testing.T) {
 	})
 	s.start()
 	defer s.close()
-	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
-	defer cancel()
+	ctx := context.Background()
 
 	cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")}
 	cert, curl, err := cl.CreateOrderCert(ctx, s.url("/pleaseissue"), csr, true)

bcrypt/bcrypt.go

@@ -50,7 +50,7 @@ func (ih InvalidHashPrefixError) Error() string {
 type InvalidCostError int
 
 func (ic InvalidCostError) Error() string {
-	return fmt.Sprintf("crypto/bcrypt: cost %d is outside allowed range (%d,%d)", int(ic), int(MinCost), int(MaxCost))
+	return fmt.Sprintf("crypto/bcrypt: cost %d is outside allowed range (%d,%d)", int(ic), MinCost, MaxCost)
 }
 
 const (
@@ -82,11 +82,20 @@ type hashed struct {
 	minor byte
 }
 
+// ErrPasswordTooLong is returned when the password passed to
+// GenerateFromPassword is too long (i.e. > 72 bytes).
+var ErrPasswordTooLong = errors.New("bcrypt: password length exceeds 72 bytes")
+
 // GenerateFromPassword returns the bcrypt hash of the password at the given
 // cost. If the cost given is less than MinCost, the cost will be set to
 // DefaultCost, instead. Use CompareHashAndPassword, as defined in this package,
 // to compare the returned hashed password with its cleartext version.
+// GenerateFromPassword does not accept passwords longer than 72 bytes, which
+// is the longest password bcrypt will operate on.
 func GenerateFromPassword(password []byte, cost int) ([]byte, error) {
+	if len(password) > 72 {
+		return nil, ErrPasswordTooLong
+	}
 	p, err := newFromPassword(password, cost)
 	if err != nil {
 		return nil, err

bcrypt/bcrypt_test.go

@@ -241,3 +241,10 @@ func TestNoSideEffectsFromCompare(t *testing.T) {
 		t.Errorf("got=%q want=%q", got, want)
 	}
 }
+
+func TestPasswordTooLong(t *testing.T) {
+	_, err := GenerateFromPassword(make([]byte, 73), 1)
+	if err != ErrPasswordTooLong {
+		t.Errorf("unexpected error: got %q, want %q", err, ErrPasswordTooLong)
+	}
+}

cryptobyte/asn1.go

@@ -264,36 +264,35 @@ func (s *String) ReadASN1Boolean(out *bool) bool {
 	return true
 }
 
-var bigIntType = reflect.TypeOf((*big.Int)(nil)).Elem()
-
 // ReadASN1Integer decodes an ASN.1 INTEGER into out and advances. If out does
-// not point to an integer or to a big.Int, it panics. It reports whether the
-// read was successful.
+// not point to an integer, to a big.Int, or to a []byte it panics. Only
+// positive and zero values can be decoded into []byte, and they are returned as
+// big-endian binary values that share memory with s. Positive values will have
+// no leading zeroes, and zero will be returned as a single zero byte.
+// ReadASN1Integer reports whether the read was successful.
 func (s *String) ReadASN1Integer(out interface{}) bool {
-	if reflect.TypeOf(out).Kind() != reflect.Ptr {
-		panic("out is not a pointer")
-	}
-	switch reflect.ValueOf(out).Elem().Kind() {
-	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+	switch out := out.(type) {
+	case *int, *int8, *int16, *int32, *int64:
 		var i int64
 		if !s.readASN1Int64(&i) || reflect.ValueOf(out).Elem().OverflowInt(i) {
 			return false
 		}
 		reflect.ValueOf(out).Elem().SetInt(i)
 		return true
-	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+	case *uint, *uint8, *uint16, *uint32, *uint64:
 		var u uint64
 		if !s.readASN1Uint64(&u) || reflect.ValueOf(out).Elem().OverflowUint(u) {
 			return false
 		}
 		reflect.ValueOf(out).Elem().SetUint(u)
 		return true
-	case reflect.Struct:
-		if reflect.TypeOf(out).Elem() == bigIntType {
-			return s.readASN1BigInt(out.(*big.Int))
-		}
+	case *big.Int:
+		return s.readASN1BigInt(out)
+	case *[]byte:
+		return s.readASN1Bytes(out)
+	default:
+		panic("out does not point to an integer type")
 	}
-	panic("out does not point to an integer type")
 }
 
 func checkASN1Integer(bytes []byte) bool {
@@ -333,6 +332,21 @@ func (s *String) readASN1BigInt(out *big.Int) bool {
 	return true
 }
 
+func (s *String) readASN1Bytes(out *[]byte) bool {
+	var bytes String
+	if !s.ReadASN1(&bytes, asn1.INTEGER) || !checkASN1Integer(bytes) {
+		return false
+	}
+	if bytes[0]&0x80 == 0x80 {
+		return false
+	}
+	for len(bytes) > 1 && bytes[0] == 0 {
+		bytes = bytes[1:]
+	}
+	*out = bytes
+	return true
+}
+
 func (s *String) readASN1Int64(out *int64) bool {
 	var bytes String
 	if !s.ReadASN1(&bytes, asn1.INTEGER) || !checkASN1Integer(bytes) || !asn1Signed(out, bytes) {
@@ -417,6 +431,14 @@ func (s *String) readBase128Int(out *int) bool {
 		}
 		ret <<= 7
 		b := s.read(1)[0]
+
+		// ITU-T X.690, section 8.19.2:
+		// The subidentifier shall be encoded in the fewest possible octets,
+		// that is, the leading octet of the subidentifier shall not have the value 0x80.
+		if i == 0 && b == 0x80 {
+			return false
+		}
+
 		ret |= int(b & 0x7f)
 		if b&0x80 == 0 {
 			*out = ret
@@ -532,7 +554,7 @@ func (s *String) ReadASN1BitString(out *encoding_asn1.BitString) bool {
 		return false
 	}
 
-	paddingBits := uint8(bytes[0])
+	paddingBits := bytes[0]
 	bytes = bytes[1:]
 	if paddingBits > 7 ||
 		len(bytes) == 0 && paddingBits != 0 ||
@@ -545,7 +567,7 @@ func (s *String) ReadASN1BitString(out *encoding_asn1.BitString) bool {
 	return true
 }
 
-// ReadASN1BitString decodes an ASN.1 BIT STRING into out and advances. It is
+// ReadASN1BitStringAsBytes decodes an ASN.1 BIT STRING into out and advances. It is
 // an error if the BIT STRING is not a whole number of bytes. It reports
 // whether the read was successful.
 func (s *String) ReadASN1BitStringAsBytes(out *[]byte) bool {
@@ -554,7 +576,7 @@ func (s *String) ReadASN1BitStringAsBytes(out *[]byte) bool {
 		return false
 	}
 
-	paddingBits := uint8(bytes[0])
+	paddingBits := bytes[0]
 	if paddingBits != 0 {
 		return false
 	}
@@ -654,34 +676,27 @@ func (s *String) SkipOptionalASN1(tag asn1.Tag) bool {
 	return s.ReadASN1(&unused, tag)
 }
 
-// ReadOptionalASN1Integer attempts to read an optional ASN.1 INTEGER
-// explicitly tagged with tag into out and advances. If no element with a
-// matching tag is present, it writes defaultValue into out instead. If out
-// does not point to an integer or to a big.Int, it panics. It reports
-// whether the read was successful.
+// ReadOptionalASN1Integer attempts to read an optional ASN.1 INTEGER explicitly
+// tagged with tag into out and advances. If no element with a matching tag is
+// present, it writes defaultValue into out instead. Otherwise, it behaves like
+// ReadASN1Integer.
 func (s *String) ReadOptionalASN1Integer(out interface{}, tag asn1.Tag, defaultValue interface{}) bool {
-	if reflect.TypeOf(out).Kind() != reflect.Ptr {
-		panic("out is not a pointer")
-	}
 	var present bool
 	var i String
 	if !s.ReadOptionalASN1(&i, &present, tag) {
 		return false
 	}
 	if !present {
-		switch reflect.ValueOf(out).Elem().Kind() {
-		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
-			reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		switch out.(type) {
+		case *int, *int8, *int16, *int32, *int64,
+			*uint, *uint8, *uint16, *uint32, *uint64, *[]byte:
 			reflect.ValueOf(out).Elem().Set(reflect.ValueOf(defaultValue))
-		case reflect.Struct:
-			if reflect.TypeOf(out).Elem() != bigIntType {
-				panic("invalid integer type")
-			}
-			if reflect.TypeOf(defaultValue).Kind() != reflect.Ptr ||
-				reflect.TypeOf(defaultValue).Elem() != bigIntType {
+		case *big.Int:
+			if defaultValue, ok := defaultValue.(*big.Int); ok {
+				out.(*big.Int).Set(defaultValue)
+			} else {
 				panic("out points to big.Int, but defaultValue does not")
 			}
-			out.(*big.Int).Set(defaultValue.(*big.Int))
 		default:
 			panic("invalid integer type")
 		}

cryptobyte/asn1_test.go

@@ -154,6 +154,32 @@ func TestReadASN1IntegerSigned(t *testing.T) {
 		}
 	})
 
+	// Repeat the same cases, reading into a []byte.
+	t.Run("bytes", func(t *testing.T) {
+		for i, test := range testData64 {
+			in := String(test.in)
+			var out []byte
+			ok := in.ReadASN1Integer(&out)
+			if test.out < 0 {
+				if ok {
+					t.Errorf("#%d: in.ReadASN1Integer(%d) = %v, want false", i, test.out, ok)
+				}
+				continue
+			}
+			if !ok {
+				t.Errorf("#%d: in.ReadASN1Integer() = %v, want true", i, ok)
+				continue
+			}
+			n := new(big.Int).SetBytes(out).Int64()
+			if n != test.out {
+				t.Errorf("#%d: in.ReadASN1Integer() = %v, want true; out = %x, want %d", i, ok, out, test.out)
+			}
+			if out[0] == 0 && len(out) > 1 {
+				t.Errorf("#%d: in.ReadASN1Integer() = %v; out = %x, has leading zeroes", i, ok, out)
+			}
+		}
+	})
+
 	// Repeat with the implicit-tagging functions
 	t.Run("WithTag", func(t *testing.T) {
 		for i, test := range testData64 {
@@ -250,6 +276,7 @@ func TestASN1ObjectIdentifier(t *testing.T) {
 		{[]byte{6, 7, 85, 0x02, 0x85, 0xc7, 0xcc, 0xfb, 0x01}, true, []int{2, 5, 2, 1492336001}},
 		{[]byte{6, 7, 0x55, 0x02, 0x87, 0xff, 0xff, 0xff, 0x7f}, true, []int{2, 5, 2, 2147483647}}, // 2**31-1
 		{[]byte{6, 7, 0x55, 0x02, 0x88, 0x80, 0x80, 0x80, 0x00}, false, []int{}},                   // 2**31
+		{[]byte{6, 3, 85, 0x80, 0x02}, false, []int{}},                                             // leading 0x80 octet
 	}
 
 	for i, test := range testData {

cryptobyte/builder.go

@@ -303,9 +303,9 @@ func (b *Builder) add(bytes ...byte) {
 	b.result = append(b.result, bytes...)
 }
 
-// Unwrite rolls back n bytes written directly to the Builder. An attempt by a
-// child builder passed to a continuation to unwrite bytes from its parent will
-// panic.
+// Unwrite rolls back non-negative n bytes written directly to the Builder.
+// An attempt by a child builder passed to a continuation to unwrite bytes
+// from its parent will panic.
 func (b *Builder) Unwrite(n int) {
 	if b.err != nil {
 		return
@@ -317,6 +317,9 @@ func (b *Builder) Unwrite(n int) {
 	if length < 0 {
 		panic("cryptobyte: internal error")
 	}
+	if n < 0 {
+		panic("cryptobyte: attempted to unwrite negative number of bytes")
+	}
 	if n > length {
 		panic("cryptobyte: attempted to unwrite more than was written")
 	}

curve25519/curve25519.go

@@ -5,71 +5,18 @@
 // Package curve25519 provides an implementation of the X25519 function, which
 // performs scalar multiplication on the elliptic curve known as Curve25519.
 // See RFC 7748.
+//
+// Starting in Go 1.20, this package is a wrapper for the X25519 implementation
+// in the crypto/ecdh package.
 package curve25519 // import "golang.org/x/crypto/curve25519"
 
-import (
-	"crypto/subtle"
-	"errors"
-	"strconv"
-
-	"golang.org/x/crypto/curve25519/internal/field"
-)
-
 // ScalarMult sets dst to the product scalar * point.
 //
 // Deprecated: when provided a low-order point, ScalarMult will set dst to all
 // zeroes, irrespective of the scalar. Instead, use the X25519 function, which
 // will return an error.
 func ScalarMult(dst, scalar, point *[32]byte) {
-	var e [32]byte
-
-	copy(e[:], scalar[:])
-	e[0] &= 248
-	e[31] &= 127
-	e[31] |= 64
-
-	var x1, x2, z2, x3, z3, tmp0, tmp1 field.Element
-	x1.SetBytes(point[:])
-	x2.One()
-	x3.Set(&x1)
-	z3.One()
-
-	swap := 0
-	for pos := 254; pos >= 0; pos-- {
-		b := e[pos/8] >> uint(pos&7)
-		b &= 1
-		swap ^= int(b)
-		x2.Swap(&x3, swap)
-		z2.Swap(&z3, swap)
-		swap = int(b)
-
-		tmp0.Subtract(&x3, &z3)
-		tmp1.Subtract(&x2, &z2)
-		x2.Add(&x2, &z2)
-		z2.Add(&x3, &z3)
-		z3.Multiply(&tmp0, &x2)
-		z2.Multiply(&z2, &tmp1)
-		tmp0.Square(&tmp1)
-		tmp1.Square(&x2)
-		x3.Add(&z3, &z2)
-		z2.Subtract(&z3, &z2)
-		x2.Multiply(&tmp1, &tmp0)
-		tmp1.Subtract(&tmp1, &tmp0)
-		z2.Square(&z2)
-
-		z3.Mult32(&tmp1, 121666)
-		x3.Square(&x3)
-		tmp0.Add(&tmp0, &z3)
-		z3.Multiply(&x1, &z2)
-		z2.Multiply(&tmp1, &tmp0)
-	}
-
-	x2.Swap(&x3, swap)
-	z2.Swap(&z3, swap)
-
-	z2.Invert(&z2)
-	x2.Multiply(&x2, &z2)
-	copy(dst[:], x2.Bytes())
+	scalarMult(dst, scalar, point)
 }
 
 // ScalarBaseMult sets dst to the product scalar * base where base is the
@@ -78,7 +25,7 @@ func ScalarMult(dst, scalar, point *[32]byte) {
 // It is recommended to use the X25519 function with Basepoint instead, as
 // copying into fixed size arrays can lead to unexpected bugs.
 func ScalarBaseMult(dst, scalar *[32]byte) {
-	ScalarMult(dst, scalar, &basePoint)
+	scalarBaseMult(dst, scalar)
 }
 
 const (
@@ -91,21 +38,10 @@ const (
 // Basepoint is the canonical Curve25519 generator.
 var Basepoint []byte
 
-var basePoint = [32]byte{9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+var basePoint = [32]byte{9}
 
 func init() { Basepoint = basePoint[:] }
 
-func checkBasepoint() {
-	if subtle.ConstantTimeCompare(Basepoint, []byte{
-		0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	}) != 1 {
-		panic("curve25519: global Basepoint value was modified")
-	}
-}
-
 // X25519 returns the result of the scalar multiplication (scalar * point),
 // according to RFC 7748, Section 5. scalar, point and the return value are
 // slices of 32 bytes.
@@ -121,26 +57,3 @@ func X25519(scalar, point []byte) ([]byte, error) {
 	var dst [32]byte
 	return x25519(&dst, scalar, point)
 }
-
-func x25519(dst *[32]byte, scalar, point []byte) ([]byte, error) {
-	var in [32]byte
-	if l := len(scalar); l != 32 {
-		return nil, errors.New("bad scalar length: " + strconv.Itoa(l) + ", expected 32")
-	}
-	if l := len(point); l != 32 {
-		return nil, errors.New("bad point length: " + strconv.Itoa(l) + ", expected 32")
-	}
-	copy(in[:], scalar)
-	if &point[0] == &Basepoint[0] {
-		checkBasepoint()
-		ScalarBaseMult(dst, &in)
-	} else {
-		var base, zero [32]byte
-		copy(base[:], point)
-		ScalarMult(dst, &in, &base)
-		if subtle.ConstantTimeCompare(dst[:], zero[:]) == 1 {
-			return nil, errors.New("bad input point: low order point")
-		}
-	}
-	return dst[:], nil
-}

curve25519/curve25519_compat.go

@@ -0,0 +1,105 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !go1.20
+
+package curve25519
+
+import (
+	"crypto/subtle"
+	"errors"
+	"strconv"
+
+	"golang.org/x/crypto/curve25519/internal/field"
+)
+
+func scalarMult(dst, scalar, point *[32]byte) {
+	var e [32]byte
+
+	copy(e[:], scalar[:])
+	e[0] &= 248
+	e[31] &= 127
+	e[31] |= 64
+
+	var x1, x2, z2, x3, z3, tmp0, tmp1 field.Element
+	x1.SetBytes(point[:])
+	x2.One()
+	x3.Set(&x1)
+	z3.One()
+
+	swap := 0
+	for pos := 254; pos >= 0; pos-- {
+		b := e[pos/8] >> uint(pos&7)
+		b &= 1
+		swap ^= int(b)
+		x2.Swap(&x3, swap)
+		z2.Swap(&z3, swap)
+		swap = int(b)
+
+		tmp0.Subtract(&x3, &z3)
+		tmp1.Subtract(&x2, &z2)
+		x2.Add(&x2, &z2)
+		z2.Add(&x3, &z3)
+		z3.Multiply(&tmp0, &x2)
+		z2.Multiply(&z2, &tmp1)
+		tmp0.Square(&tmp1)
+		tmp1.Square(&x2)
+		x3.Add(&z3, &z2)
+		z2.Subtract(&z3, &z2)
+		x2.Multiply(&tmp1, &tmp0)
+		tmp1.Subtract(&tmp1, &tmp0)
+		z2.Square(&z2)
+
+		z3.Mult32(&tmp1, 121666)
+		x3.Square(&x3)
+		tmp0.Add(&tmp0, &z3)
+		z3.Multiply(&x1, &z2)
+		z2.Multiply(&tmp1, &tmp0)
+	}
+
+	x2.Swap(&x3, swap)
+	z2.Swap(&z3, swap)
+
+	z2.Invert(&z2)
+	x2.Multiply(&x2, &z2)
+	copy(dst[:], x2.Bytes())
+}
+
+func scalarBaseMult(dst, scalar *[32]byte) {
+	checkBasepoint()
+	scalarMult(dst, scalar, &basePoint)
+}
+
+func x25519(dst *[32]byte, scalar, point []byte) ([]byte, error) {
+	var in [32]byte
+	if l := len(scalar); l != 32 {
+		return nil, errors.New("bad scalar length: " + strconv.Itoa(l) + ", expected 32")
+	}
+	if l := len(point); l != 32 {
+		return nil, errors.New("bad point length: " + strconv.Itoa(l) + ", expected 32")
+	}
+	copy(in[:], scalar)
+	if &point[0] == &Basepoint[0] {
+		scalarBaseMult(dst, &in)
+	} else {
+		var base, zero [32]byte
+		copy(base[:], point)
+		scalarMult(dst, &in, &base)
+		if subtle.ConstantTimeCompare(dst[:], zero[:]) == 1 {
+			return nil, errors.New("bad input point: low order point")
+		}
+	}
+	return dst[:], nil
+}
+
+func checkBasepoint() {
+	if subtle.ConstantTimeCompare(Basepoint, []byte{
+		0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	}) != 1 {
+		panic("curve25519: global Basepoint value was modified")
+	}
+}

curve25519/curve25519_go120.go

@@ -0,0 +1,46 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.20
+
+package curve25519
+
+import "crypto/ecdh"
+
+func x25519(dst *[32]byte, scalar, point []byte) ([]byte, error) {
+	curve := ecdh.X25519()
+	pub, err := curve.NewPublicKey(point)
+	if err != nil {
+		return nil, err
+	}
+	priv, err := curve.NewPrivateKey(scalar)
+	if err != nil {
+		return nil, err
+	}
+	out, err := priv.ECDH(pub)
+	if err != nil {
+		return nil, err
+	}
+	copy(dst[:], out)
+	return dst[:], nil
+}
+
+func scalarMult(dst, scalar, point *[32]byte) {
+	if _, err := x25519(dst, scalar[:], point[:]); err != nil {
+		// The only error condition for x25519 when the inputs are 32 bytes long
+		// is if the output would have been the all-zero value.
+		for i := range dst {
+			dst[i] = 0
+		}
+	}
+}
+
+func scalarBaseMult(dst, scalar *[32]byte) {
+	curve := ecdh.X25519()
+	priv, err := curve.NewPrivateKey(scalar[:])
+	if err != nil {
+		panic("curve25519: internal error: scalarBaseMult was not 32 bytes")
+	}
+	copy(dst[:], priv.PublicKey().Bytes())
+}

curve25519/curve25519_test.go

@@ -2,13 +2,15 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package curve25519
+package curve25519_test
 
 import (
 	"bytes"
 	"crypto/rand"
 	"encoding/hex"
 	"testing"
+
+	"golang.org/x/crypto/curve25519"
 )
 
 const expectedHex = "89161fde887b2b53de549af483940106ecc114d6982daa98256de23bdf77661a"
@@ -19,7 +21,7 @@ func TestX25519Basepoint(t *testing.T) {
 
 	for i := 0; i < 200; i++ {
 		var err error
-		x, err = X25519(x, Basepoint)
+		x, err = curve25519.X25519(x, curve25519.Basepoint)
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -32,12 +34,12 @@ func TestX25519Basepoint(t *testing.T) {
 }
 
 func TestLowOrderPoints(t *testing.T) {
-	scalar := make([]byte, ScalarSize)
+	scalar := make([]byte, curve25519.ScalarSize)
 	if _, err := rand.Read(scalar); err != nil {
 		t.Fatal(err)
 	}
 	for i, p := range lowOrderPoints {
-		out, err := X25519(scalar, p)
+		out, err := curve25519.X25519(scalar, p)
 		if err == nil {
 			t.Errorf("%d: expected error, got nil", i)
 		}
@@ -48,10 +50,10 @@ func TestLowOrderPoints(t *testing.T) {
 }
 
 func TestTestVectors(t *testing.T) {
-	t.Run("Legacy", func(t *testing.T) { testTestVectors(t, ScalarMult) })
+	t.Run("Legacy", func(t *testing.T) { testTestVectors(t, curve25519.ScalarMult) })
 	t.Run("X25519", func(t *testing.T) {
 		testTestVectors(t, func(dst, scalar, point *[32]byte) {
-			out, err := X25519(scalar[:], point[:])
+			out, err := curve25519.X25519(scalar[:], point[:])
 			if err != nil {
 				t.Fatal(err)
 			}
@@ -88,10 +90,10 @@ func TestHighBitIgnored(t *testing.T) {
 	var hi0, hi1 [32]byte
 
 	u[31] &= 0x7f
-	ScalarMult(&hi0, &s, &u)
+	curve25519.ScalarMult(&hi0, &s, &u)
 
 	u[31] |= 0x80
-	ScalarMult(&hi1, &s, &u)
+	curve25519.ScalarMult(&hi1, &s, &u)
 
 	if !bytes.Equal(hi0[:], hi1[:]) {
 		t.Errorf("high bit of group point should not affect result")
@@ -101,14 +103,14 @@ func TestHighBitIgnored(t *testing.T) {
 var benchmarkSink byte
 
 func BenchmarkX25519Basepoint(b *testing.B) {
-	scalar := make([]byte, ScalarSize)
+	scalar := make([]byte, curve25519.ScalarSize)
 	if _, err := rand.Read(scalar); err != nil {
 		b.Fatal(err)
 	}
 
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		out, err := X25519(scalar, Basepoint)
+		out, err := curve25519.X25519(scalar, curve25519.Basepoint)
 		if err != nil {
 			b.Fatal(err)
 		}
@@ -117,11 +119,11 @@ func BenchmarkX25519Basepoint(b *testing.B) {
 }
 
 func BenchmarkX25519(b *testing.B) {
-	scalar := make([]byte, ScalarSize)
+	scalar := make([]byte, curve25519.ScalarSize)
 	if _, err := rand.Read(scalar); err != nil {
 		b.Fatal(err)
 	}
-	point, err := X25519(scalar, Basepoint)
+	point, err := curve25519.X25519(scalar, curve25519.Basepoint)
 	if err != nil {
 		b.Fatal(err)
 	}
@@ -131,7 +133,7 @@ func BenchmarkX25519(b *testing.B) {
 
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		out, err := X25519(scalar, point)
+		out, err := curve25519.X25519(scalar, point)
 		if err != nil {
 			b.Fatal(err)
 		}

curve25519/internal/field/fe_generic.go

@@ -245,7 +245,7 @@ func feSquareGeneric(v, a *Element) {
 	v.carryPropagate()
 }
 
-// carryPropagate brings the limbs below 52 bits by applying the reduction
+// carryPropagateGeneric brings the limbs below 52 bits by applying the reduction
 // identity (a * 2²⁵⁵ + b = a * 19 + b) to the l4 carry. TODO inline
 func (v *Element) carryPropagateGeneric() *Element {
 	c0 := v.l0 >> 51

curve25519/vectors_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package curve25519
+package curve25519_test
 
 // lowOrderPoints from libsodium.
 // https://github.com/jedisct1/libsodium/blob/65621a1059a37d/src/libsodium/crypto_scalarmult/curve25519/ref10/x25519_ref10.c#L11-L70

go.mod

@@ -3,9 +3,9 @@ module golang.org/x/crypto
 go 1.17
 
 require (
-	golang.org/x/net v0.2.0
-	golang.org/x/sys v0.2.0
-	golang.org/x/term v0.2.0
+	golang.org/x/net v0.10.0 // tagx:ignore
+	golang.org/x/sys v0.12.0
+	golang.org/x/term v0.12.0
 )
 
-require golang.org/x/text v0.4.0 // indirect
+require golang.org/x/text v0.13.0 // indirect

go.sum

@@ -2,30 +2,40 @@ github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5t
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
+golang.org/x/mod v0.8.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
-golang.org/x/net v0.2.0 h1:sZfSu1wtKLGlWI4ZZayP0ck9Y73K1ynO6gqzTdBVdPU=
-golang.org/x/net v0.2.0/go.mod h1:KqCZLdyyvdV855qA2rE3GC2aiw5xGR5TEjj8smXukLY=
+golang.org/x/net v0.6.0/go.mod h1:2Tu9+aMcznHK/AK1HMvgo6xiTLG5rD5rZLDS+rp2Bjs=
+golang.org/x/net v0.10.0 h1:X2//UzNDwYmtCLn7To6G58Wr6f5ahEAQgKNzv9Y951M=
+golang.org/x/net v0.10.0/go.mod h1:0qNGK6F8kojg2nk9dLZ2mShWaEBan6FAoqfSigmmuDg=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.2.0 h1:ljd4t30dBnAvMZaQCevtY0xLLD0A+bRZXbgLMLU1F/A=
-golang.org/x/sys v0.2.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.8.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.12.0 h1:CM0HF96J0hcLAwsHPJZjfdNzs0gftsLfgKt57wWHJ0o=
+golang.org/x/sys v0.12.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
-golang.org/x/term v0.2.0 h1:z85xZCsEl7bi/KwbNADeBYoOP0++7W1ipu+aGnpwzRM=
-golang.org/x/term v0.2.0/go.mod h1:TVmDHMZPmdnySmBfhjOoOdhjzdE1h4u1VwSiw2l1Nuc=
+golang.org/x/term v0.5.0/go.mod h1:jMB1sMXY+tzblOD4FWmEbocvup2/aLOaQEp7JmGp78k=
+golang.org/x/term v0.8.0/go.mod h1:xPskH00ivmX89bAKVGSKKtLOWNx2+17Eiy94tnKShWo=
+golang.org/x/term v0.12.0 h1:/ZfYdc3zq+q02Rv9vGqTeSItdzZTSNDmfTi0mBAuidU=
+golang.org/x/term v0.12.0/go.mod h1:owVbMEjm3cBLCHdkQu9b1opXd4ETQWc3BhuQGKgXgvU=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
-golang.org/x/text v0.4.0 h1:BrVqGRd7+k1DiOgtnFvAkoQEWQvBc25ouMJM6429SFg=
-golang.org/x/text v0.4.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
+golang.org/x/text v0.7.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
+golang.org/x/text v0.9.0/go.mod h1:e1OnstbJyHTd6l/uOt8jFFHp6TRDWZR/bV3emEE/zU8=
+golang.org/x/text v0.13.0 h1:ablQoSUd0tRdKxZewP80B+BaqeKJuVhuRxj/dkrun3k=
+golang.org/x/text v0.13.0/go.mod h1:TvPlkZtksWOMsz7fbANvkp4WM8x/WCo/om8BMLbz+aE=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
+golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

internal/testenv/exec.go

@@ -0,0 +1,120 @@
+// 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.
+
+package testenv
+
+import (
+	"context"
+	"os"
+	"os/exec"
+	"reflect"
+	"strconv"
+	"testing"
+	"time"
+)
+
+// CommandContext is like exec.CommandContext, but:
+//   - skips t if the platform does not support os/exec,
+//   - sends SIGQUIT (if supported by the platform) instead of SIGKILL
+//     in its Cancel function
+//   - if the test has a deadline, adds a Context timeout and WaitDelay
+//     for an arbitrary grace period before the test's deadline expires,
+//   - fails the test if the command does not complete before the test's deadline, and
+//   - sets a Cleanup function that verifies that the test did not leak a subprocess.
+func CommandContext(t testing.TB, ctx context.Context, name string, args ...string) *exec.Cmd {
+	t.Helper()
+
+	var (
+		cancelCtx   context.CancelFunc
+		gracePeriod time.Duration // unlimited unless the test has a deadline (to allow for interactive debugging)
+	)
+
+	if t, ok := t.(interface {
+		testing.TB
+		Deadline() (time.Time, bool)
+	}); ok {
+		if td, ok := t.Deadline(); ok {
+			// Start with a minimum grace period, just long enough to consume the
+			// output of a reasonable program after it terminates.
+			gracePeriod = 100 * time.Millisecond
+			if s := os.Getenv("GO_TEST_TIMEOUT_SCALE"); s != "" {
+				scale, err := strconv.Atoi(s)
+				if err != nil {
+					t.Fatalf("invalid GO_TEST_TIMEOUT_SCALE: %v", err)
+				}
+				gracePeriod *= time.Duration(scale)
+			}
+
+			// If time allows, increase the termination grace period to 5% of the
+			// test's remaining time.
+			testTimeout := time.Until(td)
+			if gp := testTimeout / 20; gp > gracePeriod {
+				gracePeriod = gp
+			}
+
+			// When we run commands that execute subprocesses, we want to reserve two
+			// grace periods to clean up: one for the delay between the first
+			// termination signal being sent (via the Cancel callback when the Context
+			// expires) and the process being forcibly terminated (via the WaitDelay
+			// field), and a second one for the delay becween the process being
+			// terminated and and the test logging its output for debugging.
+			//
+			// (We want to ensure that the test process itself has enough time to
+			// log the output before it is also terminated.)
+			cmdTimeout := testTimeout - 2*gracePeriod
+
+			if cd, ok := ctx.Deadline(); !ok || time.Until(cd) > cmdTimeout {
+				// Either ctx doesn't have a deadline, or its deadline would expire
+				// after (or too close before) the test has already timed out.
+				// Add a shorter timeout so that the test will produce useful output.
+				ctx, cancelCtx = context.WithTimeout(ctx, cmdTimeout)
+			}
+		}
+	}
+
+	cmd := exec.CommandContext(ctx, name, args...)
+	// Set the Cancel and WaitDelay fields only if present (go 1.20 and later).
+	// TODO: When Go 1.19 is no longer supported, remove this use of reflection
+	// and instead set the fields directly.
+	if cmdCancel := reflect.ValueOf(cmd).Elem().FieldByName("Cancel"); cmdCancel.IsValid() {
+		cmdCancel.Set(reflect.ValueOf(func() error {
+			if cancelCtx != nil && ctx.Err() == context.DeadlineExceeded {
+				// The command timed out due to running too close to the test's deadline.
+				// There is no way the test did that intentionally — it's too close to the
+				// wire! — so mark it as a test failure. That way, if the test expects the
+				// command to fail for some other reason, it doesn't have to distinguish
+				// between that reason and a timeout.
+				t.Errorf("test timed out while running command: %v", cmd)
+			} else {
+				// The command is being terminated due to ctx being canceled, but
+				// apparently not due to an explicit test deadline that we added.
+				// Log that information in case it is useful for diagnosing a failure,
+				// but don't actually fail the test because of it.
+				t.Logf("%v: terminating command: %v", ctx.Err(), cmd)
+			}
+			return cmd.Process.Signal(Sigquit)
+		}))
+	}
+	if cmdWaitDelay := reflect.ValueOf(cmd).Elem().FieldByName("WaitDelay"); cmdWaitDelay.IsValid() {
+		cmdWaitDelay.Set(reflect.ValueOf(gracePeriod))
+	}
+
+	t.Cleanup(func() {
+		if cancelCtx != nil {
+			cancelCtx()
+		}
+		if cmd.Process != nil && cmd.ProcessState == nil {
+			t.Errorf("command was started, but test did not wait for it to complete: %v", cmd)
+		}
+	})
+
+	return cmd
+}
+
+// Command is like exec.Command, but applies the same changes as
+// testenv.CommandContext (with a default Context).
+func Command(t testing.TB, name string, args ...string) *exec.Cmd {
+	t.Helper()
+	return CommandContext(t, context.Background(), name, args...)
+}

internal/testenv/testenv_notunix.go

@@ -0,0 +1,15 @@
+// Copyright 2021 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 windows || plan9 || (js && wasm) || wasip1
+
+package testenv
+
+import (
+	"os"
+)
+
+// Sigquit is the signal to send to kill a hanging subprocess.
+// On Unix we send SIGQUIT, but on non-Unix we only have os.Kill.
+var Sigquit = os.Kill

internal/testenv/testenv_unix.go

@@ -0,0 +1,15 @@
+// Copyright 2021 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 unix
+
+package testenv
+
+import (
+	"syscall"
+)
+
+// Sigquit is the signal to send to kill a hanging subprocess.
+// Send SIGQUIT to get a stack trace.
+var Sigquit = syscall.SIGQUIT

internal/wycheproof/ecdh_stdlib_test.go

@@ -118,7 +118,7 @@ func TestECDHStdLib(t *testing.T) {
 					}
 
 					shared := decodeHex(tt.Shared)
-					x, err := curve.ECDH(priv, pub)
+					x, err := priv.ECDH(pub)
 					if err != nil {
 						if tg.Curve == "curve25519" && !shouldPass {
 							// ECDH is expected to only return an error when using X25519,

internal/wycheproof/ecdsa_test.go

@@ -6,7 +6,11 @@ package wycheproof
 
 import (
 	"crypto/ecdsa"
+	"math/big"
 	"testing"
+
+	"golang.org/x/crypto/cryptobyte"
+	"golang.org/x/crypto/cryptobyte/asn1"
 )
 
 func TestECDSA(t *testing.T) {
@@ -76,9 +80,25 @@ func TestECDSA(t *testing.T) {
 			h.Reset()
 			h.Write(decodeHex(sig.Msg))
 			hashed := h.Sum(nil)
-			got := ecdsa.VerifyASN1(pub, hashed, decodeHex(sig.Sig))
+			sigBytes := decodeHex(sig.Sig)
+			got := ecdsa.VerifyASN1(pub, hashed, sigBytes)
 			if want := shouldPass(sig.Result, sig.Flags, flagsShouldPass); got != want {
-				t.Errorf("tcid: %d, type: %s, comment: %q, wanted success: %t", sig.TcID, sig.Result, sig.Comment, want)
+				t.Errorf("tcid: %d, type: %s, comment: %q, VerifyASN1 wanted success: %t", sig.TcID, sig.Result, sig.Comment, want)
+			}
+
+			var r, s big.Int
+			var inner cryptobyte.String
+			input := cryptobyte.String(sigBytes)
+			if !input.ReadASN1(&inner, asn1.SEQUENCE) ||
+				!input.Empty() ||
+				!inner.ReadASN1Integer(&r) ||
+				!inner.ReadASN1Integer(&s) ||
+				!inner.Empty() {
+				continue
+			}
+			got = ecdsa.Verify(pub, hashed, &r, &s)
+			if want := shouldPass(sig.Result, sig.Flags, flagsShouldPass); got != want {
+				t.Errorf("tcid: %d, type: %s, comment: %q, Verify wanted success: %t", sig.TcID, sig.Result, sig.Comment, want)
 			}
 		}
 	}

internal/wycheproof/wycheproof_test.go

@@ -11,6 +11,7 @@ import (
 	"crypto/x509"
 	"encoding/hex"
 	"encoding/json"
+	"flag"
 	"fmt"
 	"log"
 	"os"
@@ -28,6 +29,11 @@ const wycheproofModVer = "v0.0.0-20191219022705-2196000605e4"
 var wycheproofTestVectorsDir string
 
 func TestMain(m *testing.M) {
+	flag.Parse()
+	if flag.Lookup("test.short").Value.(flag.Getter).Get().(bool) {
+		log.Println("skipping test that downloads testdata via 'go mod download' in short mode")
+		os.Exit(0)
+	}
 	if _, err := exec.LookPath("go"); err != nil {
 		log.Printf("skipping test because 'go' command is unavailable: %v", err)
 		os.Exit(0)
@@ -42,8 +48,6 @@ func TestMain(m *testing.M) {
 	// can be used in the following tests.
 	path := "github.com/google/wycheproof@" + wycheproofModVer
 	cmd := exec.Command("go", "mod", "download", "-json", path)
-	// TODO: enable the sumdb once the Trybots proxy supports it.
-	cmd.Env = append(os.Environ(), "GONOSUMDB=*")
 	output, err := cmd.Output()
 	if err != nil {
 		log.Fatalf("failed to run `go mod download -json %s`, output: %s", path, output)

openpgp/armor/armor.go

@@ -156,7 +156,7 @@ func (r *openpgpReader) Read(p []byte) (n int, err error) {
 	n, err = r.b64Reader.Read(p)
 	r.currentCRC = crc24(r.currentCRC, p[:n])
 
-	if err == io.EOF && r.lReader.crcSet && r.lReader.crc != uint32(r.currentCRC&crc24Mask) {
+	if err == io.EOF && r.lReader.crcSet && r.lReader.crc != r.currentCRC&crc24Mask {
 		return 0, ArmorCorrupt
 	}
 

openpgp/keys.go

@@ -61,7 +61,7 @@ type Key struct {
 type KeyRing interface {
 	// KeysById returns the set of keys that have the given key id.
 	KeysById(id uint64) []Key
-	// KeysByIdAndUsage returns the set of keys with the given id
+	// KeysByIdUsage returns the set of keys with the given id
 	// that also meet the key usage given by requiredUsage.
 	// The requiredUsage is expressed as the bitwise-OR of
 	// packet.KeyFlag* values.
@@ -183,7 +183,7 @@ func (el EntityList) KeysById(id uint64) (keys []Key) {
 	return
 }
 
-// KeysByIdAndUsage returns the set of keys with the given id that also meet
+// KeysByIdUsage returns the set of keys with the given id that also meet
 // the key usage given by requiredUsage.  The requiredUsage is expressed as
 // the bitwise-OR of packet.KeyFlag* values.
 func (el EntityList) KeysByIdUsage(id uint64, requiredUsage byte) (keys []Key) {

openpgp/packet/compressed.go

@@ -60,7 +60,7 @@ func (c *Compressed) parse(r io.Reader) error {
 	return err
 }
 
-// compressedWriterCloser represents the serialized compression stream
+// compressedWriteCloser represents the serialized compression stream
 // header and the compressor. Its Close() method ensures that both the
 // compressor and serialized stream header are closed. Its Write()
 // method writes to the compressor.

ssh/agent/client_test.go

@@ -29,6 +29,9 @@ func startOpenSSHAgent(t *testing.T) (client ExtendedAgent, socket string, clean
 		// types supported vary by platform.
 		t.Skip("skipping test due to -short")
 	}
+	if runtime.GOOS == "windows" {
+		t.Skip("skipping on windows, we don't support connecting to the ssh-agent via a named pipe")
+	}
 
 	bin, err := exec.LookPath("ssh-agent")
 	if err != nil {
@@ -366,7 +369,8 @@ func TestAuth(t *testing.T) {
 	go func() {
 		conn, _, _, err := ssh.NewServerConn(a, &serverConf)
 		if err != nil {
-			t.Fatalf("Server: %v", err)
+			t.Errorf("NewServerConn error: %v", err)
+			return
 		}
 		conn.Close()
 	}()

ssh/agent/server.go

@@ -20,7 +20,7 @@ import (
 	"golang.org/x/crypto/ssh"
 )
 
-// Server wraps an Agent and uses it to implement the agent side of
+// server wraps an Agent and uses it to implement the agent side of
 // the SSH-agent, wire protocol.
 type server struct {
 	agent Agent

ssh/agent/server_test.go

@@ -53,10 +53,11 @@ func TestSetupForwardAgent(t *testing.T) {
 	incoming := make(chan *ssh.ServerConn, 1)
 	go func() {
 		conn, _, _, err := ssh.NewServerConn(a, &serverConf)
-		if err != nil {
-			t.Fatalf("Server: %v", err)
-		}
 		incoming <- conn
+		if err != nil {
+			t.Errorf("NewServerConn error: %v", err)
+			return
+		}
 	}()
 
 	conf := ssh.ClientConfig{
@@ -71,8 +72,10 @@ func TestSetupForwardAgent(t *testing.T) {
 	if err := ForwardToRemote(client, socket); err != nil {
 		t.Fatalf("SetupForwardAgent: %v", err)
 	}
-
 	server := <-incoming
+	if server == nil {
+		t.Fatal("Unable to get server")
+	}
 	ch, reqs, err := server.OpenChannel(channelType, nil)
 	if err != nil {
 		t.Fatalf("OpenChannel(%q): %v", channelType, err)

ssh/benchmark_test.go

@@ -6,6 +6,7 @@ package ssh
 
 import (
 	"errors"
+	"fmt"
 	"io"
 	"net"
 	"testing"
@@ -90,16 +91,16 @@ func BenchmarkEndToEnd(b *testing.B) {
 	go func() {
 		newCh, err := server.Accept()
 		if err != nil {
-			b.Fatalf("Client: %v", err)
+			panic(fmt.Sprintf("Client: %v", err))
 		}
 		ch, incoming, err := newCh.Accept()
 		if err != nil {
-			b.Fatalf("Accept: %v", err)
+			panic(fmt.Sprintf("Accept: %v", err))
 		}
 		go DiscardRequests(incoming)
 		for i := 0; i < b.N; i++ {
 			if _, err := io.ReadFull(ch, output); err != nil {
-				b.Fatalf("ReadFull: %v", err)
+				panic(fmt.Sprintf("ReadFull: %v", err))
 			}
 		}
 		ch.Close()

ssh/cipher.go

@@ -114,7 +114,8 @@ var cipherModes = map[string]*cipherMode{
 	"arcfour": {16, 0, streamCipherMode(0, newRC4)},
 
 	// AEAD ciphers
-	gcmCipherID:        {16, 12, newGCMCipher},
+	gcm128CipherID:     {16, 12, newGCMCipher},
+	gcm256CipherID:     {32, 12, newGCMCipher},
 	chacha20Poly1305ID: {64, 0, newChaCha20Cipher},
 
 	// CBC mode is insecure and so is not included in the default config.

ssh/cipher_test.go

@@ -141,7 +141,7 @@ func TestCVE202143565(t *testing.T) {
 		constructPacket func(packetCipher) io.Reader
 	}{
 		{
-			cipher: gcmCipherID,
+			cipher: gcm128CipherID,
 			constructPacket: func(client packetCipher) io.Reader {
 				internalCipher := client.(*gcmCipher)
 				b := &bytes.Buffer{}

ssh/client_auth_test.go

@@ -132,9 +132,7 @@ func TestClientAuthPublicKey(t *testing.T) {
 	if err := tryAuth(t, config); err != nil {
 		t.Fatalf("unable to dial remote side: %s", err)
 	}
-	// Once the server implements the server-sig-algs extension, this will turn
-	// into KeyAlgoRSASHA256.
-	if len(signer.used) != 1 || signer.used[0] != KeyAlgoRSA {
+	if len(signer.used) != 1 || signer.used[0] != KeyAlgoRSASHA256 {
 		t.Errorf("unexpected Sign/SignWithAlgorithm calls: %q", signer.used)
 	}
 }
@@ -957,3 +955,124 @@ func TestAuthMethodGSSAPIWithMIC(t *testing.T) {
 		}
 	}
 }
+
+func TestCompatibleAlgoAndSignatures(t *testing.T) {
+	type testcase struct {
+		algo       string
+		sigFormat  string
+		compatible bool
+	}
+	testcases := []*testcase{
+		{
+			KeyAlgoRSA,
+			KeyAlgoRSA,
+			true,
+		},
+		{
+			KeyAlgoRSA,
+			KeyAlgoRSASHA256,
+			true,
+		},
+		{
+			KeyAlgoRSA,
+			KeyAlgoRSASHA512,
+			true,
+		},
+		{
+			KeyAlgoRSASHA256,
+			KeyAlgoRSA,
+			true,
+		},
+		{
+			KeyAlgoRSASHA512,
+			KeyAlgoRSA,
+			true,
+		},
+		{
+			KeyAlgoRSASHA512,
+			KeyAlgoRSASHA256,
+			true,
+		},
+		{
+			KeyAlgoRSASHA256,
+			KeyAlgoRSASHA512,
+			true,
+		},
+		{
+			KeyAlgoRSASHA512,
+			KeyAlgoRSASHA512,
+			true,
+		},
+		{
+			CertAlgoRSAv01,
+			KeyAlgoRSA,
+			true,
+		},
+		{
+			CertAlgoRSAv01,
+			KeyAlgoRSASHA256,
+			true,
+		},
+		{
+			CertAlgoRSAv01,
+			KeyAlgoRSASHA512,
+			true,
+		},
+		{
+			CertAlgoRSASHA256v01,
+			KeyAlgoRSASHA512,
+			true,
+		},
+		{
+			CertAlgoRSASHA512v01,
+			KeyAlgoRSASHA512,
+			true,
+		},
+		{
+			CertAlgoRSASHA512v01,
+			KeyAlgoRSASHA256,
+			true,
+		},
+		{
+			CertAlgoRSASHA256v01,
+			CertAlgoRSAv01,
+			true,
+		},
+		{
+			CertAlgoRSAv01,
+			CertAlgoRSASHA512v01,
+			true,
+		},
+		{
+			KeyAlgoECDSA256,
+			KeyAlgoRSA,
+			false,
+		},
+		{
+			KeyAlgoECDSA256,
+			KeyAlgoECDSA521,
+			false,
+		},
+		{
+			KeyAlgoECDSA256,
+			KeyAlgoECDSA256,
+			true,
+		},
+		{
+			KeyAlgoECDSA256,
+			KeyAlgoED25519,
+			false,
+		},
+		{
+			KeyAlgoED25519,
+			KeyAlgoED25519,
+			true,
+		},
+	}
+
+	for _, c := range testcases {
+		if isAlgoCompatible(c.algo, c.sigFormat) != c.compatible {
+			t.Errorf("algorithm %q, signature format %q, expected compatible to be %t", c.algo, c.sigFormat, c.compatible)
+		}
+	}
+}

ssh/client_test.go

@@ -254,3 +254,93 @@ func TestNewClientConn(t *testing.T) {
 		})
 	}
 }
+
+func TestUnsupportedAlgorithm(t *testing.T) {
+	for _, tt := range []struct {
+		name      string
+		config    Config
+		wantError string
+	}{
+		{
+			"unsupported KEX",
+			Config{
+				KeyExchanges: []string{"unsupported"},
+			},
+			"no common algorithm",
+		},
+		{
+			"unsupported and supported KEXs",
+			Config{
+				KeyExchanges: []string{"unsupported", kexAlgoCurve25519SHA256},
+			},
+			"",
+		},
+		{
+			"unsupported cipher",
+			Config{
+				Ciphers: []string{"unsupported"},
+			},
+			"no common algorithm",
+		},
+		{
+			"unsupported and supported ciphers",
+			Config{
+				Ciphers: []string{"unsupported", chacha20Poly1305ID},
+			},
+			"",
+		},
+		{
+			"unsupported MAC",
+			Config{
+				MACs: []string{"unsupported"},
+				// MAC is used for non AAED ciphers.
+				Ciphers: []string{"aes256-ctr"},
+			},
+			"no common algorithm",
+		},
+		{
+			"unsupported and supported MACs",
+			Config{
+				MACs: []string{"unsupported", "hmac-sha2-256-etm@openssh.com"},
+				// MAC is used for non AAED ciphers.
+				Ciphers: []string{"aes256-ctr"},
+			},
+			"",
+		},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			c1, c2, err := netPipe()
+			if err != nil {
+				t.Fatalf("netPipe: %v", err)
+			}
+			defer c1.Close()
+			defer c2.Close()
+
+			serverConf := &ServerConfig{
+				Config: tt.config,
+				PasswordCallback: func(conn ConnMetadata, password []byte) (*Permissions, error) {
+					return &Permissions{}, nil
+				},
+			}
+			serverConf.AddHostKey(testSigners["rsa"])
+			go NewServerConn(c1, serverConf)
+
+			clientConf := &ClientConfig{
+				User:   "testuser",
+				Config: tt.config,
+				Auth: []AuthMethod{
+					Password("testpw"),
+				},
+				HostKeyCallback: InsecureIgnoreHostKey(),
+			}
+			_, _, _, err = NewClientConn(c2, "", clientConf)
+			if err != nil {
+				if tt.wantError == "" || !strings.Contains(err.Error(), tt.wantError) {
+					t.Errorf("%s: got error %q, missing %q", tt.name, err.Error(), tt.wantError)
+				}
+			} else if tt.wantError != "" {
+				t.Errorf("%s: succeeded, but want error string %q", tt.name, tt.wantError)
+			}
+		})
+	}
+}

ssh/common.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"io"
 	"math"
+	"strings"
 	"sync"
 
 	_ "crypto/sha1"
@@ -27,7 +28,7 @@ const (
 // supportedCiphers lists ciphers we support but might not recommend.
 var supportedCiphers = []string{
 	"aes128-ctr", "aes192-ctr", "aes256-ctr",
-	"aes128-gcm@openssh.com",
+	"aes128-gcm@openssh.com", gcm256CipherID,
 	chacha20Poly1305ID,
 	"arcfour256", "arcfour128", "arcfour",
 	aes128cbcID,
@@ -36,7 +37,7 @@ var supportedCiphers = []string{
 
 // preferredCiphers specifies the default preference for ciphers.
 var preferredCiphers = []string{
-	"aes128-gcm@openssh.com",
+	"aes128-gcm@openssh.com", gcm256CipherID,
 	chacha20Poly1305ID,
 	"aes128-ctr", "aes192-ctr", "aes256-ctr",
 }
@@ -48,7 +49,8 @@ var supportedKexAlgos = []string{
 	// P384 and P521 are not constant-time yet, but since we don't
 	// reuse ephemeral keys, using them for ECDH should be OK.
 	kexAlgoECDH256, kexAlgoECDH384, kexAlgoECDH521,
-	kexAlgoDH14SHA256, kexAlgoDH14SHA1, kexAlgoDH1SHA1,
+	kexAlgoDH14SHA256, kexAlgoDH16SHA512, kexAlgoDH14SHA1,
+	kexAlgoDH1SHA1,
 }
 
 // serverForbiddenKexAlgos contains key exchange algorithms, that are forbidden
@@ -58,8 +60,9 @@ var serverForbiddenKexAlgos = map[string]struct{}{
 	kexAlgoDHGEXSHA256: {}, // server half implementation is only minimal to satisfy the automated tests
 }
 
-// preferredKexAlgos specifies the default preference for key-exchange algorithms
-// in preference order.
+// preferredKexAlgos specifies the default preference for key-exchange
+// algorithms in preference order. The diffie-hellman-group16-sha512 algorithm
+// is disabled by default because it is a bit slower than the others.
 var preferredKexAlgos = []string{
 	kexAlgoCurve25519SHA256, kexAlgoCurve25519SHA256LibSSH,
 	kexAlgoECDH256, kexAlgoECDH384, kexAlgoECDH521,
@@ -69,12 +72,12 @@ var preferredKexAlgos = []string{
 // supportedHostKeyAlgos specifies the supported host-key algorithms (i.e. methods
 // of authenticating servers) in preference order.
 var supportedHostKeyAlgos = []string{
-	CertAlgoRSASHA512v01, CertAlgoRSASHA256v01,
+	CertAlgoRSASHA256v01, CertAlgoRSASHA512v01,
 	CertAlgoRSAv01, CertAlgoDSAv01, CertAlgoECDSA256v01,
 	CertAlgoECDSA384v01, CertAlgoECDSA521v01, CertAlgoED25519v01,
 
 	KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521,
-	KeyAlgoRSASHA512, KeyAlgoRSASHA256,
+	KeyAlgoRSASHA256, KeyAlgoRSASHA512,
 	KeyAlgoRSA, KeyAlgoDSA,
 
 	KeyAlgoED25519,
@@ -84,7 +87,7 @@ var supportedHostKeyAlgos = []string{
 // This is based on RFC 4253, section 6.4, but with hmac-md5 variants removed
 // because they have reached the end of their useful life.
 var supportedMACs = []string{
-	"hmac-sha2-256-etm@openssh.com", "hmac-sha2-256", "hmac-sha1", "hmac-sha1-96",
+	"hmac-sha2-256-etm@openssh.com", "hmac-sha2-512-etm@openssh.com", "hmac-sha2-256", "hmac-sha2-512", "hmac-sha1", "hmac-sha1-96",
 }
 
 var supportedCompressions = []string{compressionNone}
@@ -118,6 +121,27 @@ func algorithmsForKeyFormat(keyFormat string) []string {
 	}
 }
 
+// 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))
+}
+
+// supportedPubKeyAuthAlgos specifies the supported client public key
+// authentication algorithms. Note that this doesn't include certificate types
+// since those use the underlying algorithm. This list is sent to the client if
+// it supports the server-sig-algs extension. Order is irrelevant.
+var supportedPubKeyAuthAlgos = []string{
+	KeyAlgoED25519,
+	KeyAlgoSKED25519, KeyAlgoSKECDSA256,
+	KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521,
+	KeyAlgoRSASHA256, KeyAlgoRSASHA512, KeyAlgoRSA,
+	KeyAlgoDSA,
+}
+
+var supportedPubKeyAuthAlgosList = strings.Join(supportedPubKeyAuthAlgos, ",")
+
 // unexpectedMessageError results when the SSH message that we received didn't
 // match what we wanted.
 func unexpectedMessageError(expected, got uint8) error {
@@ -153,7 +177,7 @@ func (a *directionAlgorithms) rekeyBytes() int64 {
 	// 2^(BLOCKSIZE/4) blocks. For all AES flavors BLOCKSIZE is
 	// 128.
 	switch a.Cipher {
-	case "aes128-ctr", "aes192-ctr", "aes256-ctr", gcmCipherID, aes128cbcID:
+	case "aes128-ctr", "aes192-ctr", "aes256-ctr", gcm128CipherID, gcm256CipherID, aes128cbcID:
 		return 16 * (1 << 32)
 
 	}
@@ -163,7 +187,8 @@ func (a *directionAlgorithms) rekeyBytes() int64 {
 }
 
 var aeadCiphers = map[string]bool{
-	gcmCipherID:        true,
+	gcm128CipherID:     true,
+	gcm256CipherID:     true,
 	chacha20Poly1305ID: true,
 }
 
@@ -246,16 +271,16 @@ type Config struct {
 	// unspecified, a size suitable for the chosen cipher is used.
 	RekeyThreshold uint64
 
-	// The allowed key exchanges algorithms. If unspecified then a
-	// default set of algorithms is used.
+	// The allowed key exchanges algorithms. If unspecified then a default set
+	// of algorithms is used. Unsupported values are silently ignored.
 	KeyExchanges []string
 
-	// The allowed cipher algorithms. If unspecified then a sensible
-	// default is used.
+	// The allowed cipher algorithms. If unspecified then a sensible default is
+	// used. Unsupported values are silently ignored.
 	Ciphers []string
 
-	// The allowed MAC algorithms. If unspecified then a sensible default
-	// is used.
+	// The allowed MAC algorithms. If unspecified then a sensible default is
+	// used. Unsupported values are silently ignored.
 	MACs []string
 }
 
@@ -272,7 +297,7 @@ func (c *Config) SetDefaults() {
 	var ciphers []string
 	for _, c := range c.Ciphers {
 		if cipherModes[c] != nil {
-			// reject the cipher if we have no cipherModes definition
+			// Ignore the cipher if we have no cipherModes definition.
 			ciphers = append(ciphers, c)
 		}
 	}
@@ -281,10 +306,26 @@ func (c *Config) SetDefaults() {
 	if c.KeyExchanges == nil {
 		c.KeyExchanges = preferredKexAlgos
 	}
+	var kexs []string
+	for _, k := range c.KeyExchanges {
+		if kexAlgoMap[k] != nil {
+			// Ignore the KEX if we have no kexAlgoMap definition.
+			kexs = append(kexs, k)
+		}
+	}
+	c.KeyExchanges = kexs
 
 	if c.MACs == nil {
 		c.MACs = supportedMACs
 	}
+	var macs []string
+	for _, m := range c.MACs {
+		if macModes[m] != nil {
+			// Ignore the MAC if we have no macModes definition.
+			macs = append(macs, m)
+		}
+	}
+	c.MACs = macs
 
 	if c.RekeyThreshold == 0 {
 		// cipher specific default

ssh/common_test.go

@@ -82,11 +82,11 @@ func TestFindAgreedAlgorithms(t *testing.T) {
 	}
 
 	cases := []testcase{
-		testcase{
+		{
 			name: "standard",
 		},
 
-		testcase{
+		{
 			name: "no common hostkey",
 			serverIn: kexInitMsg{
 				ServerHostKeyAlgos: []string{"hostkey2"},
@@ -94,7 +94,7 @@ func TestFindAgreedAlgorithms(t *testing.T) {
 			wantErr: true,
 		},
 
-		testcase{
+		{
 			name: "no common kex",
 			serverIn: kexInitMsg{
 				KexAlgos: []string{"kex2"},
@@ -102,7 +102,7 @@ func TestFindAgreedAlgorithms(t *testing.T) {
 			wantErr: true,
 		},
 
-		testcase{
+		{
 			name: "no common cipher",
 			serverIn: kexInitMsg{
 				CiphersClientServer: []string{"cipher2"},
@@ -110,7 +110,7 @@ func TestFindAgreedAlgorithms(t *testing.T) {
 			wantErr: true,
 		},
 
-		testcase{
+		{
 			name: "client decides cipher",
 			serverIn: kexInitMsg{
 				CiphersClientServer: []string{"cipher1", "cipher2"},

ssh/connection.go

@@ -97,7 +97,7 @@ func (c *connection) Close() error {
 	return c.sshConn.conn.Close()
 }
 
-// sshconn provides net.Conn metadata, but disallows direct reads and
+// sshConn provides net.Conn metadata, but disallows direct reads and
 // writes.
 type sshConn struct {
 	conn net.Conn

ssh/handshake.go

@@ -58,11 +58,13 @@ type handshakeTransport struct {
 	incoming  chan []byte
 	readError error
 
-	mu             sync.Mutex
-	writeError     error
-	sentInitPacket []byte
-	sentInitMsg    *kexInitMsg
-	pendingPackets [][]byte // Used when a key exchange is in progress.
+	mu               sync.Mutex
+	writeError       error
+	sentInitPacket   []byte
+	sentInitMsg      *kexInitMsg
+	pendingPackets   [][]byte // Used when a key exchange is in progress.
+	writePacketsLeft uint32
+	writeBytesLeft   int64
 
 	// If the read loop wants to schedule a kex, it pings this
 	// channel, and the write loop will send out a kex
@@ -71,7 +73,8 @@ type handshakeTransport struct {
 
 	// If the other side requests or confirms a kex, its kexInit
 	// packet is sent here for the write loop to find it.
-	startKex chan *pendingKex
+	startKex    chan *pendingKex
+	kexLoopDone chan struct{} // closed (with writeError non-nil) when kexLoop exits
 
 	// data for host key checking
 	hostKeyCallback HostKeyCallback
@@ -86,12 +89,10 @@ type handshakeTransport struct {
 	// Algorithms agreed in the last key exchange.
 	algorithms *algorithms
 
+	// Counters exclusively owned by readLoop.
 	readPacketsLeft uint32
 	readBytesLeft   int64
 
-	writePacketsLeft uint32
-	writeBytesLeft   int64
-
 	// The session ID or nil if first kex did not complete yet.
 	sessionID []byte
 }
@@ -108,7 +109,8 @@ func newHandshakeTransport(conn keyingTransport, config *Config, clientVersion,
 		clientVersion: clientVersion,
 		incoming:      make(chan []byte, chanSize),
 		requestKex:    make(chan struct{}, 1),
-		startKex:      make(chan *pendingKex, 1),
+		startKex:      make(chan *pendingKex),
+		kexLoopDone:   make(chan struct{}),
 
 		config: config,
 	}
@@ -340,16 +342,17 @@ write:
 		t.mu.Unlock()
 	}
 
-	// drain startKex channel. We don't service t.requestKex
-	// because nobody does blocking sends there.
-	go func() {
-		for init := range t.startKex {
-			init.done <- t.writeError
-		}
-	}()
-
 	// Unblock reader.
 	t.conn.Close()
+
+	// drain startKex channel. We don't service t.requestKex
+	// because nobody does blocking sends there.
+	for request := range t.startKex {
+		request.done <- t.getWriteError()
+	}
+
+	// Mark that the loop is done so that Close can return.
+	close(t.kexLoopDone)
 }
 
 // The protocol uses uint32 for packet counters, so we can't let them
@@ -545,7 +548,16 @@ func (t *handshakeTransport) writePacket(p []byte) error {
 }
 
 func (t *handshakeTransport) Close() error {
-	return t.conn.Close()
+	// Close the connection. This should cause the readLoop goroutine to wake up
+	// and close t.startKex, which will shut down kexLoop if running.
+	err := t.conn.Close()
+
+	// Wait for the kexLoop goroutine to complete.
+	// At that point we know that the readLoop goroutine is complete too,
+	// because kexLoop itself waits for readLoop to close the startKex channel.
+	<-t.kexLoopDone
+
+	return err
 }
 
 func (t *handshakeTransport) enterKeyExchange(otherInitPacket []byte) error {
@@ -615,7 +627,8 @@ func (t *handshakeTransport) enterKeyExchange(otherInitPacket []byte) error {
 		return err
 	}
 
-	if t.sessionID == nil {
+	firstKeyExchange := t.sessionID == nil
+	if firstKeyExchange {
 		t.sessionID = result.H
 	}
 	result.SessionID = t.sessionID
@@ -626,6 +639,24 @@ func (t *handshakeTransport) enterKeyExchange(otherInitPacket []byte) error {
 	if err = t.conn.writePacket([]byte{msgNewKeys}); err != nil {
 		return err
 	}
+
+	// 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.
+	if !isClient && firstKeyExchange && contains(clientInit.KexAlgos, "ext-info-c") {
+		extInfo := &extInfoMsg{
+			NumExtensions: 1,
+			Payload:       make([]byte, 0, 4+15+4+len(supportedPubKeyAuthAlgosList)),
+		}
+		extInfo.Payload = appendInt(extInfo.Payload, len("server-sig-algs"))
+		extInfo.Payload = append(extInfo.Payload, "server-sig-algs"...)
+		extInfo.Payload = appendInt(extInfo.Payload, len(supportedPubKeyAuthAlgosList))
+		extInfo.Payload = append(extInfo.Payload, supportedPubKeyAuthAlgosList...)
+		if err := t.conn.writePacket(Marshal(extInfo)); err != nil {
+			return err
+		}
+	}
+
 	if packet, err := t.conn.readPacket(); err != nil {
 		return err
 	} else if packet[0] != msgNewKeys {

ssh/handshake_test.go

@@ -148,6 +148,7 @@ func TestHandshakeBasic(t *testing.T) {
 	clientDone := make(chan int, 0)
 	gotHalf := make(chan int, 0)
 	const N = 20
+	errorCh := make(chan error, 1)
 
 	go func() {
 		defer close(clientDone)
@@ -158,7 +159,9 @@ func TestHandshakeBasic(t *testing.T) {
 		for i := 0; i < N; i++ {
 			p := []byte{msgRequestSuccess, byte(i)}
 			if err := trC.writePacket(p); err != nil {
-				t.Fatalf("sendPacket: %v", err)
+				errorCh <- err
+				trC.Close()
+				return
 			}
 			if (i % 10) == 5 {
 				<-gotHalf
@@ -177,16 +180,15 @@ func TestHandshakeBasic(t *testing.T) {
 				checker.waitCall <- 1
 			}
 		}
+		errorCh <- nil
 	}()
 
 	// Server checks that client messages come in cleanly
 	i := 0
-	err = nil
 	for ; i < N; i++ {
-		var p []byte
-		p, err = trS.readPacket()
-		if err != nil {
-			break
+		p, err := trS.readPacket()
+		if err != nil && err != io.EOF {
+			t.Fatalf("server error: %v", err)
 		}
 		if (i % 10) == 5 {
 			gotHalf <- 1
@@ -198,8 +200,8 @@ func TestHandshakeBasic(t *testing.T) {
 		}
 	}
 	<-clientDone
-	if err != nil && err != io.EOF {
-		t.Fatalf("server error: %v", err)
+	if err := <-errorCh; err != nil {
+		t.Fatalf("sendPacket: %v", err)
 	}
 	if i != N {
 		t.Errorf("received %d messages, want 10.", i)
@@ -345,16 +347,16 @@ func TestHandshakeAutoRekeyRead(t *testing.T) {
 
 	// While we read out the packet, a key change will be
 	// initiated.
-	done := make(chan int, 1)
+	errorCh := make(chan error, 1)
 	go func() {
-		defer close(done)
-		if _, err := trC.readPacket(); err != nil {
-			t.Fatalf("readPacket(client): %v", err)
-		}
-
+		_, err := trC.readPacket()
+		errorCh <- err
 	}()
 
-	<-done
+	if err := <-errorCh; err != nil {
+		t.Fatalf("readPacket(client): %v", err)
+	}
+
 	<-sync.called
 }
 
@@ -421,8 +423,8 @@ func TestHandshakeErrorHandlingWriteCoupled(t *testing.T) {
 // handshakeTransport deadlocks, the go runtime will detect it and
 // panic.
 func testHandshakeErrorHandlingN(t *testing.T, readLimit, writeLimit int, coupled bool) {
-	if runtime.GOOS == "js" && runtime.GOARCH == "wasm" {
-		t.Skip("skipping on js/wasm; see golang.org/issue/32840")
+	if (runtime.GOOS == "js" || runtime.GOOS == "wasip1") && runtime.GOARCH == "wasm" {
+		t.Skipf("skipping on %s/wasm; see golang.org/issue/32840", runtime.GOOS)
 	}
 	msg := Marshal(&serviceRequestMsg{strings.Repeat("x", int(minRekeyThreshold)/4)})
 
@@ -562,7 +564,7 @@ func TestHandshakeRekeyDefault(t *testing.T) {
 }
 
 func TestHandshakeAEADCipherNoMAC(t *testing.T) {
-	for _, cipher := range []string{chacha20Poly1305ID, gcmCipherID} {
+	for _, cipher := range []string{chacha20Poly1305ID, gcm128CipherID} {
 		checker := &syncChecker{
 			called: make(chan int, 1),
 		}

ssh/kex.go

@@ -23,6 +23,7 @@ const (
 	kexAlgoDH1SHA1                = "diffie-hellman-group1-sha1"
 	kexAlgoDH14SHA1               = "diffie-hellman-group14-sha1"
 	kexAlgoDH14SHA256             = "diffie-hellman-group14-sha256"
+	kexAlgoDH16SHA512             = "diffie-hellman-group16-sha512"
 	kexAlgoECDH256                = "ecdh-sha2-nistp256"
 	kexAlgoECDH384                = "ecdh-sha2-nistp384"
 	kexAlgoECDH521                = "ecdh-sha2-nistp521"
@@ -430,6 +431,17 @@ func init() {
 		hashFunc: crypto.SHA256,
 	}
 
+	// This is the group called diffie-hellman-group16-sha512 in RFC
+	// 8268 and Oakley Group 16 in RFC 3526.
+	p, _ = new(big.Int).SetString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
+
+	kexAlgoMap[kexAlgoDH16SHA512] = &dhGroup{
+		g:        new(big.Int).SetInt64(2),
+		p:        p,
+		pMinus1:  new(big.Int).Sub(p, bigOne),
+		hashFunc: crypto.SHA512,
+	}
+
 	kexAlgoMap[kexAlgoECDH521] = &ecdh{elliptic.P521()}
 	kexAlgoMap[kexAlgoECDH384] = &ecdh{elliptic.P384()}
 	kexAlgoMap[kexAlgoECDH256] = &ecdh{elliptic.P256()}

ssh/kex_test.go

@@ -8,6 +8,7 @@ package ssh
 
 import (
 	"crypto/rand"
+	"fmt"
 	"reflect"
 	"sync"
 	"testing"
@@ -63,3 +64,43 @@ func TestKexes(t *testing.T) {
 		})
 	}
 }
+
+func BenchmarkKexes(b *testing.B) {
+	type kexResultErr struct {
+		result *kexResult
+		err    error
+	}
+
+	for name, kex := range kexAlgoMap {
+		b.Run(name, func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				t1, t2 := memPipe()
+
+				s := make(chan kexResultErr, 1)
+				c := make(chan kexResultErr, 1)
+				var magics handshakeMagics
+
+				go func() {
+					r, e := kex.Client(t1, rand.Reader, &magics)
+					t1.Close()
+					c <- kexResultErr{r, e}
+				}()
+				go func() {
+					r, e := kex.Server(t2, rand.Reader, &magics, testSigners["ecdsa"].(AlgorithmSigner), testSigners["ecdsa"].PublicKey().Type())
+					t2.Close()
+					s <- kexResultErr{r, e}
+				}()
+
+				clientRes := <-c
+				serverRes := <-s
+
+				if clientRes.err != nil {
+					panic(fmt.Sprintf("client: %v", clientRes.err))
+				}
+				if serverRes.err != nil {
+					panic(fmt.Sprintf("server: %v", serverRes.err))
+				}
+			}
+		})
+	}
+}

ssh/keys.go

@@ -1087,9 +1087,9 @@ func (*PassphraseMissingError) Error() string {
 	return "ssh: this private key is passphrase protected"
 }
 
-// ParseRawPrivateKey returns a private key from a PEM encoded private key. It
-// supports RSA (PKCS#1), PKCS#8, DSA (OpenSSL), and ECDSA private keys. If the
-// private key is encrypted, it will return a PassphraseMissingError.
+// ParseRawPrivateKey returns a private key from a PEM encoded private key. It supports
+// RSA, DSA, ECDSA, and Ed25519 private keys in PKCS#1, PKCS#8, OpenSSL, and OpenSSH
+// formats. If the private key is encrypted, it will return a PassphraseMissingError.
 func ParseRawPrivateKey(pemBytes []byte) (interface{}, error) {
 	block, _ := pem.Decode(pemBytes)
 	if block == nil {

ssh/knownhosts/knownhosts.go

@@ -142,7 +142,7 @@ func keyEq(a, b ssh.PublicKey) bool {
 	return bytes.Equal(a.Marshal(), b.Marshal())
 }
 
-// IsAuthorityForHost can be used as a callback in ssh.CertChecker
+// IsHostAuthority can be used as a callback in ssh.CertChecker
 func (db *hostKeyDB) IsHostAuthority(remote ssh.PublicKey, address string) bool {
 	h, p, err := net.SplitHostPort(address)
 	if err != nil {

ssh/mac.go

@@ -10,6 +10,7 @@ import (
 	"crypto/hmac"
 	"crypto/sha1"
 	"crypto/sha256"
+	"crypto/sha512"
 	"hash"
 )
 
@@ -46,9 +47,15 @@ func (t truncatingMAC) Size() int {
 func (t truncatingMAC) BlockSize() int { return t.hmac.BlockSize() }
 
 var macModes = map[string]*macMode{
+	"hmac-sha2-512-etm@openssh.com": {64, true, func(key []byte) hash.Hash {
+		return hmac.New(sha512.New, key)
+	}},
 	"hmac-sha2-256-etm@openssh.com": {32, true, func(key []byte) hash.Hash {
 		return hmac.New(sha256.New, key)
 	}},
+	"hmac-sha2-512": {64, false, func(key []byte) hash.Hash {
+		return hmac.New(sha512.New, key)
+	}},
 	"hmac-sha2-256": {32, false, func(key []byte) hash.Hash {
 		return hmac.New(sha256.New, key)
 	}},

ssh/mux_test.go

@@ -5,6 +5,8 @@
 package ssh
 
 import (
+	"errors"
+	"fmt"
 	"io"
 	"sync"
 	"testing"
@@ -29,14 +31,21 @@ func channelPair(t *testing.T) (*channel, *channel, *mux) {
 	go func() {
 		newCh, ok := <-s.incomingChannels
 		if !ok {
-			t.Fatalf("No incoming channel")
+			t.Error("no incoming channel")
+			close(res)
+			return
 		}
 		if newCh.ChannelType() != "chan" {
-			t.Fatalf("got type %q want chan", newCh.ChannelType())
+			t.Errorf("got type %q want chan", newCh.ChannelType())
+			newCh.Reject(Prohibited, fmt.Sprintf("got type %q want chan", newCh.ChannelType()))
+			close(res)
+			return
 		}
 		ch, _, err := newCh.Accept()
 		if err != nil {
-			t.Fatalf("Accept %v", err)
+			t.Errorf("accept: %v", err)
+			close(res)
+			return
 		}
 		res <- ch.(*channel)
 	}()
@@ -45,8 +54,12 @@ func channelPair(t *testing.T) (*channel, *channel, *mux) {
 	if err != nil {
 		t.Fatalf("OpenChannel: %v", err)
 	}
+	w := <-res
+	if w == nil {
+		t.Fatal("unable to get write channel")
+	}
 
-	return <-res, ch, c
+	return w, ch, c
 }
 
 // Test that stderr and stdout can be addressed from different
@@ -74,14 +87,14 @@ func TestMuxChannelExtendedThreadSafety(t *testing.T) {
 	go func() {
 		c, err := io.ReadAll(reader)
 		if string(c) != magic {
-			t.Fatalf("stdout read got %q, want %q (error %s)", c, magic, err)
+			t.Errorf("stdout read got %q, want %q (error %s)", c, magic, err)
 		}
 		rd.Done()
 	}()
 	go func() {
 		c, err := io.ReadAll(reader.Stderr())
 		if string(c) != magic {
-			t.Fatalf("stderr read got %q, want %q (error %s)", c, magic, err)
+			t.Errorf("stderr read got %q, want %q (error %s)", c, magic, err)
 		}
 		rd.Done()
 	}()
@@ -102,11 +115,13 @@ func TestMuxReadWrite(t *testing.T) {
 	go func() {
 		_, err := s.Write([]byte(magic))
 		if err != nil {
-			t.Fatalf("Write: %v", err)
+			t.Errorf("Write: %v", err)
+			return
 		}
 		_, err = s.Extended(1).Write([]byte(magicExt))
 		if err != nil {
-			t.Fatalf("Write: %v", err)
+			t.Errorf("Write: %v", err)
+			return
 		}
 	}()
 
@@ -215,10 +230,13 @@ func TestMuxReject(t *testing.T) {
 	go func() {
 		ch, ok := <-server.incomingChannels
 		if !ok {
-			t.Fatalf("Accept")
+			t.Error("cannot accept channel")
+			return
 		}
 		if ch.ChannelType() != "ch" || string(ch.ExtraData()) != "extra" {
-			t.Fatalf("unexpected channel: %q, %q", ch.ChannelType(), ch.ExtraData())
+			t.Errorf("unexpected channel: %q, %q", ch.ChannelType(), ch.ExtraData())
+			ch.Reject(RejectionReason(UnknownChannelType), UnknownChannelType.String())
+			return
 		}
 		ch.Reject(RejectionReason(42), "message")
 	}()
@@ -294,7 +312,7 @@ func TestMuxUnknownChannelRequests(t *testing.T) {
 	defer serverPipe.Close()
 	defer client.Close()
 
-	kDone := make(chan struct{})
+	kDone := make(chan error, 1)
 	go func() {
 		// Ignore unknown channel messages that don't want a reply.
 		err := serverPipe.writePacket(Marshal(channelRequestMsg{
@@ -304,7 +322,8 @@ func TestMuxUnknownChannelRequests(t *testing.T) {
 			RequestSpecificData: []byte{},
 		}))
 		if err != nil {
-			t.Fatalf("send: %v", err)
+			kDone <- fmt.Errorf("send: %w", err)
+			return
 		}
 
 		// Send a keepalive, which should get a channel failure message
@@ -316,44 +335,53 @@ func TestMuxUnknownChannelRequests(t *testing.T) {
 			RequestSpecificData: []byte{},
 		}))
 		if err != nil {
-			t.Fatalf("send: %v", err)
+			kDone <- fmt.Errorf("send: %w", err)
+			return
 		}
 
 		packet, err := serverPipe.readPacket()
 		if err != nil {
-			t.Fatalf("read packet: %v", err)
+			kDone <- fmt.Errorf("read packet: %w", err)
+			return
 		}
 		decoded, err := decode(packet)
 		if err != nil {
-			t.Fatalf("decode failed: %v", err)
+			kDone <- fmt.Errorf("decode failed: %w", err)
+			return
 		}
 
 		switch msg := decoded.(type) {
 		case *channelRequestFailureMsg:
 			if msg.PeersID != 2 {
-				t.Fatalf("received response to wrong message: %v", msg)
+				kDone <- fmt.Errorf("received response to wrong message: %v", msg)
+				return
+
 			}
 		default:
-			t.Fatalf("unexpected channel message: %v", msg)
+			kDone <- fmt.Errorf("unexpected channel message: %v", msg)
+			return
 		}
 
-		kDone <- struct{}{}
+		kDone <- nil
 
 		// Receive and respond to the keepalive to confirm the mux is
 		// still processing requests.
 		packet, err = serverPipe.readPacket()
 		if err != nil {
-			t.Fatalf("read packet: %v", err)
+			kDone <- fmt.Errorf("read packet: %w", err)
+			return
 		}
 		if packet[0] != msgGlobalRequest {
-			t.Fatalf("expected global request")
+			kDone <- errors.New("expected global request")
+			return
 		}
 
 		err = serverPipe.writePacket(Marshal(globalRequestFailureMsg{
 			Data: []byte{},
 		}))
 		if err != nil {
-			t.Fatalf("failed to send failure msg: %v", err)
+			kDone <- fmt.Errorf("failed to send failure msg: %w", err)
+			return
 		}
 
 		close(kDone)
@@ -362,7 +390,10 @@ func TestMuxUnknownChannelRequests(t *testing.T) {
 	// Wait for the server to send the keepalive message and receive back a
 	// response.
 	select {
-	case <-kDone:
+	case err := <-kDone:
+		if err != nil {
+			t.Fatal(err)
+		}
 	case <-time.After(10 * time.Second):
 		t.Fatalf("server never received ack")
 	}
@@ -373,7 +404,10 @@ func TestMuxUnknownChannelRequests(t *testing.T) {
 	}
 
 	select {
-	case <-kDone:
+	case err := <-kDone:
+		if err != nil {
+			t.Fatal(err)
+		}
 	case <-time.After(10 * time.Second):
 		t.Fatalf("server never shut down")
 	}
@@ -385,20 +419,23 @@ func TestMuxClosedChannel(t *testing.T) {
 	defer serverPipe.Close()
 	defer client.Close()
 
-	kDone := make(chan struct{})
+	kDone := make(chan error, 1)
 	go func() {
 		// Open the channel.
 		packet, err := serverPipe.readPacket()
 		if err != nil {
-			t.Fatalf("read packet: %v", err)
+			kDone <- fmt.Errorf("read packet: %w", err)
+			return
 		}
 		if packet[0] != msgChannelOpen {
-			t.Fatalf("expected chan open")
+			kDone <- errors.New("expected chan open")
+			return
 		}
 
 		var openMsg channelOpenMsg
 		if err := Unmarshal(packet, &openMsg); err != nil {
-			t.Fatalf("unmarshal: %v", err)
+			kDone <- fmt.Errorf("unmarshal: %w", err)
+			return
 		}
 
 		// Send back the opened channel confirmation.
@@ -409,7 +446,8 @@ func TestMuxClosedChannel(t *testing.T) {
 			MaxPacketSize: channelMaxPacket,
 		}))
 		if err != nil {
-			t.Fatalf("send: %v", err)
+			kDone <- fmt.Errorf("send: %w", err)
+			return
 		}
 
 		// Close the channel.
@@ -417,7 +455,8 @@ func TestMuxClosedChannel(t *testing.T) {
 			PeersID: openMsg.PeersID,
 		}))
 		if err != nil {
-			t.Fatalf("send: %v", err)
+			kDone <- fmt.Errorf("send: %w", err)
+			return
 		}
 
 		// Send a keepalive message on the channel we just closed.
@@ -428,43 +467,51 @@ func TestMuxClosedChannel(t *testing.T) {
 			RequestSpecificData: []byte{},
 		}))
 		if err != nil {
-			t.Fatalf("send: %v", err)
+			kDone <- fmt.Errorf("send: %w", err)
+			return
 		}
 
 		// Receive the channel closed response.
 		packet, err = serverPipe.readPacket()
 		if err != nil {
-			t.Fatalf("read packet: %v", err)
+			kDone <- fmt.Errorf("read packet: %w", err)
+			return
 		}
 		if packet[0] != msgChannelClose {
-			t.Fatalf("expected channel close")
+			kDone <- errors.New("expected channel close")
+			return
 		}
 
 		// Receive the keepalive response failure.
 		packet, err = serverPipe.readPacket()
 		if err != nil {
-			t.Fatalf("read packet: %v", err)
+			kDone <- fmt.Errorf("read packet: %w", err)
+			return
 		}
 		if packet[0] != msgChannelFailure {
-			t.Fatalf("expected channel close")
+			kDone <- errors.New("expected channel failure")
+			return
 		}
-		kDone <- struct{}{}
+		kDone <- nil
 
 		// Receive and respond to the keepalive to confirm the mux is
 		// still processing requests.
 		packet, err = serverPipe.readPacket()
 		if err != nil {
-			t.Fatalf("read packet: %v", err)
+			kDone <- fmt.Errorf("read packet: %w", err)
+			return
 		}
 		if packet[0] != msgGlobalRequest {
-			t.Fatalf("expected global request")
+			kDone <- errors.New("expected global request")
+			return
 		}
 
 		err = serverPipe.writePacket(Marshal(globalRequestFailureMsg{
 			Data: []byte{},
 		}))
 		if err != nil {
-			t.Fatalf("failed to send failure msg: %v", err)
+			kDone <- fmt.Errorf("failed to send failure msg: %w", err)
+			return
 		}
 
 		close(kDone)

ssh/server.go

@@ -291,15 +291,6 @@ func (s *connection) serverHandshake(config *ServerConfig) (*Permissions, error)
 	return perms, err
 }
 
-func isAcceptableAlgo(algo string) bool {
-	switch algo {
-	case KeyAlgoRSA, KeyAlgoRSASHA256, KeyAlgoRSASHA512, KeyAlgoDSA, KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521, KeyAlgoSKECDSA256, KeyAlgoED25519, KeyAlgoSKED25519,
-		CertAlgoRSAv01, CertAlgoDSAv01, CertAlgoECDSA256v01, CertAlgoECDSA384v01, CertAlgoECDSA521v01, CertAlgoSKECDSA256v01, CertAlgoED25519v01, CertAlgoSKED25519v01:
-		return true
-	}
-	return false
-}
-
 func checkSourceAddress(addr net.Addr, sourceAddrs string) error {
 	if addr == nil {
 		return errors.New("ssh: no address known for client, but source-address match required")
@@ -379,6 +370,25 @@ func gssExchangeToken(gssapiConfig *GSSAPIWithMICConfig, firstToken []byte, s *c
 	return authErr, perms, nil
 }
 
+// isAlgoCompatible checks if the signature format is compatible with the
+// selected algorithm taking into account edge cases that occur with old
+// clients.
+func isAlgoCompatible(algo, sigFormat string) bool {
+	// Compatibility for old clients.
+	//
+	// For certificate authentication with OpenSSH 7.2-7.7 signature format can
+	// be rsa-sha2-256 or rsa-sha2-512 for the algorithm
+	// ssh-rsa-cert-v01@openssh.com.
+	//
+	// With gpg-agent < 2.2.6 the algorithm can be rsa-sha2-256 or rsa-sha2-512
+	// for signature format ssh-rsa.
+	if isRSA(algo) && isRSA(sigFormat) {
+		return true
+	}
+	// Standard case: the underlying algorithm must match the signature format.
+	return underlyingAlgo(algo) == sigFormat
+}
+
 // ServerAuthError represents server authentication errors and is
 // sometimes returned by NewServerConn. It appends any authentication
 // errors that may occur, and is returned if all of the authentication
@@ -514,7 +524,7 @@ userAuthLoop:
 				return nil, parseError(msgUserAuthRequest)
 			}
 			algo := string(algoBytes)
-			if !isAcceptableAlgo(algo) {
+			if !contains(supportedPubKeyAuthAlgos, underlyingAlgo(algo)) {
 				authErr = fmt.Errorf("ssh: algorithm %q not accepted", algo)
 				break
 			}
@@ -572,11 +582,11 @@ userAuthLoop:
 				// algorithm name that corresponds to algo with
 				// sig.Format.  This is usually the same, but
 				// for certs, the names differ.
-				if !isAcceptableAlgo(sig.Format) {
+				if !contains(supportedPubKeyAuthAlgos, sig.Format) {
 					authErr = fmt.Errorf("ssh: algorithm %q not accepted", sig.Format)
 					break
 				}
-				if underlyingAlgo(algo) != sig.Format {
+				if !isAlgoCompatible(algo, sig.Format) {
 					authErr = fmt.Errorf("ssh: signature %q not compatible with selected algorithm %q", sig.Format, algo)
 					break
 				}

ssh/session_test.go

@@ -36,7 +36,8 @@ func dial(handler serverType, t *testing.T) *Client {
 
 		conn, chans, reqs, err := NewServerConn(c1, &conf)
 		if err != nil {
-			t.Fatalf("Unable to handshake: %v", err)
+			t.Errorf("Unable to handshake: %v", err)
+			return
 		}
 		go DiscardRequests(reqs)
 
@@ -647,10 +648,12 @@ func TestSessionID(t *testing.T) {
 		User:            "user",
 	}
 
+	srvErrCh := make(chan error, 1)
 	go func() {
 		conn, chans, reqs, err := NewServerConn(c1, serverConf)
+		srvErrCh <- err
 		if err != nil {
-			t.Fatalf("server handshake: %v", err)
+			return
 		}
 		serverID <- conn.SessionID()
 		go DiscardRequests(reqs)
@@ -659,10 +662,12 @@ func TestSessionID(t *testing.T) {
 		}
 	}()
 
+	cliErrCh := make(chan error, 1)
 	go func() {
 		conn, chans, reqs, err := NewClientConn(c2, "", clientConf)
+		cliErrCh <- err
 		if err != nil {
-			t.Fatalf("client handshake: %v", err)
+			return
 		}
 		clientID <- conn.SessionID()
 		go DiscardRequests(reqs)
@@ -671,6 +676,14 @@ func TestSessionID(t *testing.T) {
 		}
 	}()
 
+	if err := <-srvErrCh; err != nil {
+		t.Fatalf("server handshake: %v", err)
+	}
+
+	if err := <-cliErrCh; err != nil {
+		t.Fatalf("client handshake: %v", err)
+	}
+
 	s := <-serverID
 	c := <-clientID
 	if bytes.Compare(s, c) != 0 {

ssh/test/agent_unix_test.go

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd
-// +build aix darwin dragonfly freebsd linux netbsd openbsd
+//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
+// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
 
 package test
 
@@ -17,7 +17,6 @@ import (
 
 func TestAgentForward(t *testing.T) {
 	server := newServer(t)
-	defer server.Shutdown()
 	conn := server.Dial(clientConfig())
 	defer conn.Close()
 

ssh/test/banner_test.go

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd
-// +build aix darwin dragonfly freebsd linux netbsd openbsd
+//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
+// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
 
 package test
 
@@ -13,7 +13,6 @@ import (
 
 func TestBannerCallbackAgainstOpenSSH(t *testing.T) {
 	server := newServer(t)
-	defer server.Shutdown()
 
 	clientConf := clientConfig()
 

ssh/test/cert_test.go

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd
-// +build aix darwin dragonfly freebsd linux netbsd openbsd
+//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
+// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
 
 package test
 
@@ -18,7 +18,6 @@ import (
 // Test both logging in with a cert, and also that the certificate presented by an OpenSSH host can be validated correctly
 func TestCertLogin(t *testing.T) {
 	s := newServer(t)
-	defer s.Shutdown()
 
 	// Use a key different from the default.
 	clientKey := testSigners["dsa"]

ssh/test/dial_unix_test.go

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !windows && !solaris && !js
-// +build !windows,!solaris,!js
+//go:build !windows && !js && !wasip1
+// +build !windows,!js,!wasip1
 
 package test
 
@@ -24,7 +24,6 @@ type dialTester interface {
 
 func testDial(t *testing.T, n, listenAddr string, x dialTester) {
 	server := newServer(t)
-	defer server.Shutdown()
 	sshConn := server.Dial(clientConfig())
 	defer sshConn.Close()
 

ssh/test/forward_unix_test.go

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd
-// +build aix darwin dragonfly freebsd linux netbsd openbsd
+//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
+// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
 
 package test
 
@@ -23,7 +23,6 @@ type closeWriter interface {
 
 func testPortForward(t *testing.T, n, listenAddr string) {
 	server := newServer(t)
-	defer server.Shutdown()
 	conn := server.Dial(clientConfig())
 	defer conn.Close()
 
@@ -120,7 +119,6 @@ func TestPortForwardUnix(t *testing.T) {
 
 func testAcceptClose(t *testing.T, n, listenAddr string) {
 	server := newServer(t)
-	defer server.Shutdown()
 	conn := server.Dial(clientConfig())
 
 	sshListener, err := conn.Listen(n, listenAddr)
@@ -162,10 +160,9 @@ func TestAcceptCloseUnix(t *testing.T) {
 // Check that listeners exit if the underlying client transport dies.
 func testPortForwardConnectionClose(t *testing.T, n, listenAddr string) {
 	server := newServer(t)
-	defer server.Shutdown()
-	conn := server.Dial(clientConfig())
+	client := server.Dial(clientConfig())
 
-	sshListener, err := conn.Listen(n, listenAddr)
+	sshListener, err := client.Listen(n, listenAddr)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -184,14 +181,10 @@ func testPortForwardConnectionClose(t *testing.T, n, listenAddr string) {
 
 	// It would be even nicer if we closed the server side, but it
 	// is more involved as the fd for that side is dup()ed.
-	server.clientConn.Close()
+	server.lastDialConn.Close()
 
-	select {
-	case <-time.After(1 * time.Second):
-		t.Errorf("timeout: listener did not close.")
-	case err := <-quit:
-		t.Logf("quit as expected (error %v)", err)
-	}
+	err = <-quit
+	t.Logf("quit as expected (error %v)", err)
 }
 
 func TestPortForwardConnectionCloseTCP(t *testing.T) {

ssh/test/multi_auth_test.go

@@ -77,27 +77,27 @@ func (ctx *multiAuthTestCtx) kbdIntCb(user, instruction string, questions []stri
 func TestMultiAuth(t *testing.T) {
 	testCases := []multiAuthTestCase{
 		// Test password,publickey authentication, assert that password callback is called 1 time
-		multiAuthTestCase{
+		{
 			authMethods:         []string{"password", "publickey"},
 			expectedPasswordCbs: 1,
 		},
 		// Test keyboard-interactive,publickey authentication, assert that keyboard-interactive callback is called 1 time
-		multiAuthTestCase{
+		{
 			authMethods:       []string{"keyboard-interactive", "publickey"},
 			expectedKbdIntCbs: 1,
 		},
 		// Test publickey,password authentication, assert that password callback is called 1 time
-		multiAuthTestCase{
+		{
 			authMethods:         []string{"publickey", "password"},
 			expectedPasswordCbs: 1,
 		},
 		// Test publickey,keyboard-interactive authentication, assert that keyboard-interactive callback is called 1 time
-		multiAuthTestCase{
+		{
 			authMethods:       []string{"publickey", "keyboard-interactive"},
 			expectedKbdIntCbs: 1,
 		},
 		// Test password,password authentication, assert that password callback is called 2 times
-		multiAuthTestCase{
+		{
 			authMethods:         []string{"password", "password"},
 			expectedPasswordCbs: 2,
 		},
@@ -108,7 +108,6 @@ func TestMultiAuth(t *testing.T) {
 			ctx := newMultiAuthTestCtx(t)
 
 			server := newServerForConfig(t, "MultiAuth", map[string]string{"AuthMethods": strings.Join(testCase.authMethods, ",")})
-			defer server.Shutdown()
 
 			clientConfig := clientConfig()
 			server.setTestPassword(clientConfig.User, ctx.password)

ssh/test/session_test.go

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !windows && !solaris && !js
-// +build !windows,!solaris,!js
+//go:build !windows && !js && !wasip1
+// +build !windows,!js,!wasip1
 
 package test
 
@@ -14,6 +14,8 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"path/filepath"
+	"regexp"
 	"runtime"
 	"strings"
 	"testing"
@@ -23,7 +25,6 @@ import (
 
 func TestRunCommandSuccess(t *testing.T) {
 	server := newServer(t)
-	defer server.Shutdown()
 	conn := server.Dial(clientConfig())
 	defer conn.Close()
 
@@ -40,7 +41,6 @@ func TestRunCommandSuccess(t *testing.T) {
 
 func TestHostKeyCheck(t *testing.T) {
 	server := newServer(t)
-	defer server.Shutdown()
 
 	conf := clientConfig()
 	hostDB := hostKeyDB()
@@ -62,7 +62,6 @@ func TestHostKeyCheck(t *testing.T) {
 
 func TestRunCommandStdin(t *testing.T) {
 	server := newServer(t)
-	defer server.Shutdown()
 	conn := server.Dial(clientConfig())
 	defer conn.Close()
 
@@ -85,7 +84,6 @@ func TestRunCommandStdin(t *testing.T) {
 
 func TestRunCommandStdinError(t *testing.T) {
 	server := newServer(t)
-	defer server.Shutdown()
 	conn := server.Dial(clientConfig())
 	defer conn.Close()
 
@@ -109,7 +107,6 @@ func TestRunCommandStdinError(t *testing.T) {
 
 func TestRunCommandFailed(t *testing.T) {
 	server := newServer(t)
-	defer server.Shutdown()
 	conn := server.Dial(clientConfig())
 	defer conn.Close()
 
@@ -126,7 +123,6 @@ func TestRunCommandFailed(t *testing.T) {
 
 func TestRunCommandWeClosed(t *testing.T) {
 	server := newServer(t)
-	defer server.Shutdown()
 	conn := server.Dial(clientConfig())
 	defer conn.Close()
 
@@ -146,7 +142,6 @@ func TestRunCommandWeClosed(t *testing.T) {
 
 func TestFuncLargeRead(t *testing.T) {
 	server := newServer(t)
-	defer server.Shutdown()
 	conn := server.Dial(clientConfig())
 	defer conn.Close()
 
@@ -178,7 +173,6 @@ func TestFuncLargeRead(t *testing.T) {
 
 func TestKeyChange(t *testing.T) {
 	server := newServer(t)
-	defer server.Shutdown()
 	conf := clientConfig()
 	hostDB := hostKeyDB()
 	conf.HostKeyCallback = hostDB.Check
@@ -225,7 +219,6 @@ func TestValidTerminalMode(t *testing.T) {
 		t.Skipf("skipping on %s", runtime.GOOS)
 	}
 	server := newServer(t)
-	defer server.Shutdown()
 	conn := server.Dial(clientConfig())
 	defer conn.Close()
 
@@ -255,15 +248,31 @@ func TestValidTerminalMode(t *testing.T) {
 		t.Fatalf("session failed: %s", err)
 	}
 
-	stdin.Write([]byte("stty -a && exit\n"))
+	if _, err := io.WriteString(stdin, "echo && echo SHELL $SHELL && stty -a && exit\n"); err != nil {
+		t.Fatal(err)
+	}
 
-	var buf bytes.Buffer
-	if _, err := io.Copy(&buf, stdout); err != nil {
+	buf := new(strings.Builder)
+	if _, err := io.Copy(buf, stdout); err != nil {
 		t.Fatalf("reading failed: %s", err)
 	}
 
+	if testing.Verbose() {
+		t.Logf("echo && echo SHELL $SHELL && stty -a && exit:\n%s", buf)
+	}
+
+	shellLine := regexp.MustCompile("(?m)^SHELL (.*)$").FindStringSubmatch(buf.String())
+	if len(shellLine) != 2 {
+		t.Fatalf("missing output from echo SHELL $SHELL")
+	}
+	switch shell := filepath.Base(strings.TrimSpace(shellLine[1])); shell {
+	case "sh", "bash":
+	default:
+		t.Skipf("skipping test on non-Bourne shell %q", shell)
+	}
+
 	if sttyOutput := buf.String(); !strings.Contains(sttyOutput, "-echo ") {
-		t.Fatalf("terminal mode failure: expected -echo in stty output, got %s", sttyOutput)
+		t.Fatal("terminal mode failure: expected -echo in stty output")
 	}
 }
 
@@ -274,7 +283,6 @@ func TestWindowChange(t *testing.T) {
 		t.Skipf("skipping on %s", runtime.GOOS)
 	}
 	server := newServer(t)
-	defer server.Shutdown()
 	conn := server.Dial(clientConfig())
 	defer conn.Close()
 
@@ -322,7 +330,6 @@ func TestWindowChange(t *testing.T) {
 
 func testOneCipher(t *testing.T, cipher string, cipherOrder []string) {
 	server := newServer(t)
-	defer server.Shutdown()
 	conf := clientConfig()
 	conf.Ciphers = []string{cipher}
 	// Don't fail if sshd doesn't have the cipher.
@@ -381,7 +388,6 @@ func TestMACs(t *testing.T) {
 	for _, mac := range macOrder {
 		t.Run(mac, func(t *testing.T) {
 			server := newServer(t)
-			defer server.Shutdown()
 			conf := clientConfig()
 			conf.MACs = []string{mac}
 			// Don't fail if sshd doesn't have the MAC.
@@ -404,10 +410,12 @@ func TestKeyExchanges(t *testing.T) {
 	// are not included in the default list of supported kex so we have to add them
 	// here manually.
 	kexOrder = append(kexOrder, "diffie-hellman-group-exchange-sha1", "diffie-hellman-group-exchange-sha256")
+	// The key exchange algorithms diffie-hellman-group16-sha512 is disabled by
+	// default so we add it here manually.
+	kexOrder = append(kexOrder, "diffie-hellman-group16-sha512")
 	for _, kex := range kexOrder {
 		t.Run(kex, func(t *testing.T) {
 			server := newServer(t)
-			defer server.Shutdown()
 			conf := clientConfig()
 			// Don't fail if sshd doesn't have the kex.
 			conf.KeyExchanges = append([]string{kex}, kexOrder...)
@@ -442,8 +450,6 @@ func TestClientAuthAlgorithms(t *testing.T) {
 			} else {
 				t.Errorf("failed for key %q", key)
 			}
-
-			server.Shutdown()
 		})
 	}
 }

ssh/test/test_unix_test.go

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || plan9
-// +build aix darwin dragonfly freebsd linux netbsd openbsd plan9
+//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || plan9 || solaris
+// +build aix darwin dragonfly freebsd linux netbsd openbsd plan9 solaris
 
 package test
 
@@ -23,6 +23,7 @@ import (
 	"testing"
 	"text/template"
 
+	"golang.org/x/crypto/internal/testenv"
 	"golang.org/x/crypto/ssh"
 	"golang.org/x/crypto/ssh/testdata"
 )
@@ -67,17 +68,13 @@ var configTmpl = map[string]*template.Template{
 
 type server struct {
 	t          *testing.T
-	cleanup    func() // executed during Shutdown
 	configfile string
-	cmd        *exec.Cmd
-	output     bytes.Buffer // holds stderr from sshd process
 
 	testUser     string // test username for sshd
 	testPasswd   string // test password for sshd
 	sshdTestPwSo string // dynamic library to inject a custom password into sshd
 
-	// Client half of the network connection.
-	clientConn net.Conn
+	lastDialConn net.Conn
 }
 
 func username() string {
@@ -193,15 +190,15 @@ func (s *server) TryDialWithAddr(config *ssh.ClientConfig, addr string) (*ssh.Cl
 		s.t.Fatalf("unixConnection: %v", err)
 	}
 
-	s.cmd = exec.Command(sshd, "-f", s.configfile, "-i", "-e")
+	cmd := testenv.Command(s.t, sshd, "-f", s.configfile, "-i", "-e")
 	f, err := c2.File()
 	if err != nil {
 		s.t.Fatalf("UnixConn.File: %v", err)
 	}
 	defer f.Close()
-	s.cmd.Stdin = f
-	s.cmd.Stdout = f
-	s.cmd.Stderr = &s.output
+	cmd.Stdin = f
+	cmd.Stdout = f
+	cmd.Stderr = new(bytes.Buffer)
 
 	if s.sshdTestPwSo != "" {
 		if s.testUser == "" {
@@ -210,18 +207,29 @@ func (s *server) TryDialWithAddr(config *ssh.ClientConfig, addr string) (*ssh.Cl
 		if s.testPasswd == "" {
 			s.t.Fatal("password missing from sshd_test_pw.so config")
 		}
-		s.cmd.Env = append(os.Environ(),
+		cmd.Env = append(os.Environ(),
 			fmt.Sprintf("LD_PRELOAD=%s", s.sshdTestPwSo),
 			fmt.Sprintf("TEST_USER=%s", s.testUser),
 			fmt.Sprintf("TEST_PASSWD=%s", s.testPasswd))
 	}
 
-	if err := s.cmd.Start(); err != nil {
-		s.t.Fail()
-		s.Shutdown()
+	if err := cmd.Start(); err != nil {
 		s.t.Fatalf("s.cmd.Start: %v", err)
 	}
-	s.clientConn = c1
+	s.lastDialConn = c1
+	s.t.Cleanup(func() {
+		// Don't check for errors; if it fails it's most
+		// likely "os: process already finished", and we don't
+		// care about that. Use os.Interrupt, so child
+		// processes are killed too.
+		cmd.Process.Signal(os.Interrupt)
+		cmd.Wait()
+		if s.t.Failed() {
+			// log any output from sshd process
+			s.t.Logf("sshd:\n%s", cmd.Stderr)
+		}
+	})
+
 	conn, chans, reqs, err := ssh.NewClientConn(c1, addr, config)
 	if err != nil {
 		return nil, err
@@ -232,29 +240,11 @@ func (s *server) TryDialWithAddr(config *ssh.ClientConfig, addr string) (*ssh.Cl
 func (s *server) Dial(config *ssh.ClientConfig) *ssh.Client {
 	conn, err := s.TryDial(config)
 	if err != nil {
-		s.t.Fail()
-		s.Shutdown()
 		s.t.Fatalf("ssh.Client: %v", err)
 	}
 	return conn
 }
 
-func (s *server) Shutdown() {
-	if s.cmd != nil && s.cmd.Process != nil {
-		// Don't check for errors; if it fails it's most
-		// likely "os: process already finished", and we don't
-		// care about that. Use os.Interrupt, so child
-		// processes are killed too.
-		s.cmd.Process.Signal(os.Interrupt)
-		s.cmd.Wait()
-	}
-	if s.t.Failed() {
-		// log any output from sshd process
-		s.t.Logf("sshd: %s", s.output.String())
-	}
-	s.cleanup()
-}
-
 func writeFile(path string, contents []byte) {
 	f, err := os.OpenFile(path, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0600)
 	if err != nil {
@@ -351,15 +341,15 @@ func newServerForConfig(t *testing.T, config string, configVars map[string]strin
 		authkeys.Write(ssh.MarshalAuthorizedKey(testPublicKeys[k]))
 	}
 	writeFile(filepath.Join(dir, "authorized_keys"), authkeys.Bytes())
+	t.Cleanup(func() {
+		if err := os.RemoveAll(dir); err != nil {
+			t.Error(err)
+		}
+	})
 
 	return &server{
 		t:          t,
 		configfile: f.Name(),
-		cleanup: func() {
-			if err := os.RemoveAll(dir); err != nil {
-				t.Error(err)
-			}
-		},
 	}
 }
 

ssh/transport.go

@@ -17,7 +17,8 @@ import (
 const debugTransport = false
 
 const (
-	gcmCipherID    = "aes128-gcm@openssh.com"
+	gcm128CipherID = "aes128-gcm@openssh.com"
+	gcm256CipherID = "aes256-gcm@openssh.com"
 	aes128cbcID    = "aes128-cbc"
 	tripledescbcID = "3des-cbc"
 )

x509roots/fallback/fallback.go

@@ -0,0 +1,31 @@
+// 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 go1.20
+
+// Package fallback embeds a set of fallback X.509 trusted roots in the
+// application by automatically invoking [x509.SetFallbackRoots]. This allows
+// the application to work correctly even if the operating system does not
+// provide a verifier or system roots pool.
+//
+// To use it, import the package like
+//
+//	import _ "golang.org/x/crypto/x509roots/fallback"
+//
+// It's recommended that only binaries, and not libraries, import this package.
+//
+// This package must be kept up to date for security and compatibility reasons.
+// Use govulncheck to be notified of when new versions of the package are
+// available.
+package fallback
+
+import "crypto/x509"
+
+func init() {
+	p := x509.NewCertPool()
+	for _, c := range bundle {
+		p.AddCert(c)
+	}
+	x509.SetFallbackRoots(p)
+}

x509roots/fallback/go.mod

@@ -0,0 +1,3 @@
+module golang.org/x/crypto/x509roots/fallback
+
+go 1.20

x509roots/fallback/internal/goissue52287/goissue52287.go

@@ -0,0 +1,8 @@
+// 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.
+
+// Package goissue52287 is an empty internal package.
+// It exists only to work around go.dev/issue/52287 and
+// can be removed after Go 1.19 stops being supported.
+package goissue52287

x509roots/gen_fallback_bundle.go

@@ -0,0 +1,135 @@
+// 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 generate
+// +build generate
+
+//go:generate go run gen_fallback_bundle.go
+
+package main
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/pem"
+	"flag"
+	"fmt"
+	"go/format"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"sort"
+
+	"golang.org/x/crypto/x509roots/nss"
+)
+
+const tmpl = `// Code generated by gen_fallback_bundle.go; DO NOT EDIT.
+
+//go:build go1.20
+
+package fallback
+
+import "crypto/x509"
+import "encoding/pem"
+
+func mustParse(b []byte) []*x509.Certificate {
+	var roots []*x509.Certificate
+	for len(b) > 0 {
+		var block *pem.Block
+		block, b = pem.Decode(b)
+		if block == nil {
+			break
+		}
+		if block.Type != "CERTIFICATE" {
+			panic("unexpected PEM block type: " + block.Type)
+		}
+		cert, err := x509.ParseCertificate(block.Bytes)
+		if err != nil {
+			panic(err)
+		}
+		roots = append(roots, cert)
+	}
+	return roots
+}
+
+var bundle = mustParse([]byte(pemRoots))
+
+// Format of the PEM list is:
+//   * Subject common name
+//   * SHA256 hash
+//   * PEM block
+
+`
+
+var (
+	certDataURL  = flag.String("certdata-url", "https://hg.mozilla.org/mozilla-central/raw-file/tip/security/nss/lib/ckfw/builtins/certdata.txt", "URL to the raw certdata.txt file to parse (certdata-path overrides this, if provided)")
+	certDataPath = flag.String("certdata-path", "", "Path to the NSS certdata.txt file to parse (this overrides certdata-url, if provided)")
+	output       = flag.String("output", "fallback/bundle.go", "Path to file to write output to")
+)
+
+func main() {
+	flag.Parse()
+
+	var certdata io.Reader
+
+	if *certDataPath != "" {
+		f, err := os.Open(*certDataPath)
+		if err != nil {
+			log.Fatalf("unable to open %q: %s", *certDataPath, err)
+		}
+		defer f.Close()
+		certdata = f
+	} else {
+		resp, err := http.Get(*certDataURL)
+		if err != nil {
+			log.Fatalf("failed to request %q: %s", *certDataURL, err)
+		}
+		defer resp.Body.Close()
+		certdata = resp.Body
+	}
+
+	certs, err := nss.Parse(certdata)
+	if err != nil {
+		log.Fatalf("failed to parse %q: %s", *certDataPath, err)
+	}
+
+	sort.Slice(certs, func(i, j int) bool {
+		// Sort based on the stringified subject (which may not be unique), and
+		// break any ties by just sorting on the raw DER (which will be unique,
+		// but is expensive). This should produce a stable sorting, which should
+		// be mostly readable by a human looking for a specific root or set of
+		// roots.
+		subjI, subjJ := certs[i].X509.Subject.String(), certs[j].X509.Subject.String()
+		if subjI == subjJ {
+			return string(certs[i].X509.Raw) < string(certs[j].X509.Raw)
+		}
+		return subjI < subjJ
+	})
+
+	b := new(bytes.Buffer)
+	b.WriteString(tmpl)
+	fmt.Fprintln(b, "const pemRoots = `")
+	for _, c := range certs {
+		if len(c.Constraints) > 0 {
+			// Until the constrained roots API lands, skip anything that has any
+			// additional constraints. Once that API is available, we can add
+			// build constraints that support both the current version and the
+			// new version.
+			continue
+		}
+		fmt.Fprintf(b, "# %s\n# %x\n", c.X509.Subject.String(), sha256.Sum256(c.X509.Raw))
+		pem.Encode(b, &pem.Block{Type: "CERTIFICATE", Bytes: c.X509.Raw})
+	}
+	fmt.Fprintln(b, "`")
+
+	formatted, err := format.Source(b.Bytes())
+	if err != nil {
+		log.Fatalf("failed to format source: %s", err)
+	}
+
+	if err := os.WriteFile(*output, formatted, 0644); err != nil {
+		log.Fatalf("failed to write to %q: %s", *output, err)
+	}
+}

x509roots/nss/parser.go

@@ -0,0 +1,259 @@
+// 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.
+
+// Package nss provides functionality for parsing NSS certdata.txt
+// formatted certificate lists and extracting serverAuth roots. Most
+// users should not use this package themselves, and should instead
+// rely on the golang.org/x/crypto/x509roots/fallback package which
+// calls x509.SetFallbackRoots on a pre-parsed set of roots.
+package nss
+
+import (
+	"bufio"
+	"bytes"
+	"crypto/sha1"
+	"crypto/x509"
+	"errors"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// Constraint is a constraint to be applied to a certificate or
+// certificate chain.
+type Constraint interface {
+	Kind() Kind
+}
+
+// Kind is the constraint kind, using the NSS enumeration.
+type Kind int
+
+const (
+	CKA_NSS_SERVER_DISTRUST_AFTER Kind = iota
+)
+
+// DistrustAfter is a Constraint that indicates a certificate has a
+// CKA_NSS_SERVER_DISTRUST_AFTER constraint. This constraint defines a date
+// after which any certificate issued which is rooted by the constrained
+// certificate should be distrusted.
+type DistrustAfter time.Time
+
+func (DistrustAfter) Kind() Kind {
+	return CKA_NSS_SERVER_DISTRUST_AFTER
+}
+
+// A Certificate represents a single trusted serverAuth certificate in the NSS
+// certdata.txt list and any constraints that should be applied to chains
+// rooted by it.
+type Certificate struct {
+	// Certificate is the parsed certificate
+	X509 *x509.Certificate
+	// Constraints contains a list of additional constraints that should be
+	// applied to any certificates that chain to Certificate. If there are
+	// any unknown constraints in the slice, Certificate should not be
+	// trusted.
+	Constraints []Constraint
+}
+
+func parseMulitLineOctal(s *bufio.Scanner) ([]byte, error) {
+	buf := bytes.NewBuffer(nil)
+	for s.Scan() {
+		if s.Text() == "END" {
+			break
+		}
+		b, err := strconv.Unquote(fmt.Sprintf("\"%s\"", s.Text()))
+		if err != nil {
+			return nil, err
+		}
+		buf.Write([]byte(b))
+	}
+	return buf.Bytes(), nil
+}
+
+type certObj struct {
+	c             *x509.Certificate
+	DistrustAfter *time.Time
+}
+
+func parseCertClass(s *bufio.Scanner) ([sha1.Size]byte, *certObj, error) {
+	var h [sha1.Size]byte
+	co := &certObj{}
+	for s.Scan() {
+		l := s.Text()
+		if l == "" {
+			// assume an empty newline indicates the end of a block
+			break
+		}
+		if strings.HasPrefix(l, "CKA_VALUE") {
+			b, err := parseMulitLineOctal(s)
+			if err != nil {
+				return h, nil, err
+			}
+			co.c, err = x509.ParseCertificate(b)
+			if err != nil {
+				return h, nil, err
+			}
+			h = sha1.Sum(b)
+		} else if strings.HasPrefix(l, "CKA_NSS_MOZILLA_CA_POLICY CK_BBOOL CK_FALSE") {
+			// we don't want it
+			return h, nil, nil
+		} else if l == "CKA_NSS_SERVER_DISTRUST_AFTER MULTILINE_OCTAL" {
+			dateStr, err := parseMulitLineOctal(s)
+			if err != nil {
+				return h, nil, err
+			}
+			t, err := time.Parse("060102150405Z0700", string(dateStr))
+			if err != nil {
+				return h, nil, err
+			}
+			co.DistrustAfter = &t
+		}
+	}
+	if co.c == nil {
+		return h, nil, errors.New("malformed CKO_CERTIFICATE object")
+	}
+	return h, co, nil
+}
+
+type trustObj struct {
+	trusted bool
+}
+
+func parseTrustClass(s *bufio.Scanner) ([sha1.Size]byte, *trustObj, error) {
+	var h [sha1.Size]byte
+	to := &trustObj{trusted: false} // default to untrusted
+
+	for s.Scan() {
+		l := s.Text()
+		if l == "" {
+			// assume an empty newline indicates the end of a block
+			break
+		}
+		if l == "CKA_CERT_SHA1_HASH MULTILINE_OCTAL" {
+			hash, err := parseMulitLineOctal(s)
+			if err != nil {
+				return h, nil, err
+			}
+			copy(h[:], hash)
+		} else if l == "CKA_TRUST_SERVER_AUTH CK_TRUST CKT_NSS_TRUSTED_DELEGATOR" {
+			// we only care about server auth
+			to.trusted = true
+		}
+	}
+
+	return h, to, nil
+}
+
+// Parse parses a NSS certdata.txt formatted file, returning only
+// trusted serverAuth roots, as well as any additional constraints. This parser
+// is very opinionated, only returning roots that are currently trusted for
+// serverAuth. As such roots returned by this package should only be used for
+// making trust decisions about serverAuth certificates, as the trust status for
+// other uses is not considered. Using the roots returned by this package for
+// trust decisions should be done carefully.
+//
+// Some roots returned by the parser may include additional constraints
+// (currently only DistrustAfter) which need to be considered when verifying
+// certificates which chain to them.
+//
+// Parse is not intended to be a general purpose parser for certdata.txt.
+func Parse(r io.Reader) ([]*Certificate, error) {
+	// certdata.txt is a rather strange format. It is essentially a list of
+	// textual PKCS#11 objects, delimited by empty lines. There are two main
+	// types of objects, certificates (CKO_CERTIFICATE) and trust definitions
+	// (CKO_NSS_TRUST). These objects appear to alternate, but this ordering is
+	// not defined anywhere, and should probably not be relied on. A single root
+	// certificate requires both the certificate object and the trust definition
+	// object in order to be properly understood.
+	//
+	// The list contains not just serverAuth certificates, so we need to be
+	// careful to only extract certificates which have the serverAuth trust bit
+	// set. Similarly there are a number of trust related bool fields that
+	// appear to _always_ be CKA_TRUE, but it seems unsafe to assume this is the
+	// case, so we should always double check.
+	//
+	// Since we only really care about a couple of fields, this parser throws
+	// away a lot of information, essentially just consuming CKA_CLASS objects
+	// and looking for the individual fields we care about. We could write a
+	// siginificantly more complex parser, which handles the entire format, but
+	// it feels like that would be over engineered for the little information
+	// that we really care about.
+
+	scanner := bufio.NewScanner(r)
+
+	type nssEntry struct {
+		cert  *certObj
+		trust *trustObj
+	}
+	entries := map[[sha1.Size]byte]*nssEntry{}
+
+	for scanner.Scan() {
+		// scan until we hit CKA_CLASS
+		if !strings.HasPrefix(scanner.Text(), "CKA_CLASS") {
+			continue
+		}
+
+		f := strings.Fields(scanner.Text())
+		if len(f) != 3 {
+			return nil, errors.New("malformed CKA_CLASS")
+		}
+		switch f[2] {
+		case "CKO_CERTIFICATE":
+			h, co, err := parseCertClass(scanner)
+			if err != nil {
+				return nil, err
+			}
+			if co != nil {
+				e, ok := entries[h]
+				if !ok {
+					e = &nssEntry{}
+					entries[h] = e
+				}
+				e.cert = co
+			}
+
+		case "CKO_NSS_TRUST":
+			h, to, err := parseTrustClass(scanner)
+			if err != nil {
+				return nil, err
+			}
+			if to != nil {
+				e, ok := entries[h]
+				if !ok {
+					e = &nssEntry{}
+					entries[h] = e
+				}
+				e.trust = to
+			}
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		return nil, err
+	}
+
+	var certs []*Certificate
+	for h, e := range entries {
+		if e.cert == nil && e.trust != nil {
+			// We may skip some certificates which are distrusted due to mozilla
+			// policy (CKA_NSS_MOZILLA_CA_POLICY CK_BBOOL CK_FALSE), which means
+			// we might get entries that appear to have a trust object, but no
+			// certificate. We can just continue on here.
+			continue
+		} else if e.cert != nil && e.trust == nil {
+			return nil, fmt.Errorf("missing trust object for certificate with SHA1 hash: %x", h)
+		}
+		if !e.trust.trusted {
+			continue
+		}
+		nssCert := &Certificate{X509: e.cert.c}
+		if e.cert.DistrustAfter != nil {
+			nssCert.Constraints = append(nssCert.Constraints, DistrustAfter(*e.cert.DistrustAfter))
+		}
+		certs = append(certs, nssCert)
+	}
+
+	return certs, nil
+}