fix TestValidTerminalMode: missing output from echo SHELL $SHELL

add leading `echo` to have better compatibility

before

```
 go test -run ^TestValidTerminalMode -v
=== RUN   TestValidTerminalMode
    session_test.go:261: echo SHELL $SHELL && stty -a && exit:
        Last login: Thu Jul  6 12:24:38 2023 from 192.168.200.1
SHELL /bin/bashubuntu:~$
        speed 38400 baud; rows 80; columns 40;
        line = 0;
        intr = ^C; quit = ^\; erase = ^?;
        kill = ^U; eof = ^D; eol = <undef>;
        eol2 = <undef>; swtch = <undef>;
        start = ^Q; stop = ^S; susp = ^Z;
        rprnt = ^R; werase = ^W; lnext = ^V;
        discard = ^O; min = 1; time = 0;
        -parenb -parodd -cmspar cs8 -hupcl
        -cstopb cread -clocal -crtscts
        -ignbrk -brkint -ignpar -parmrk -inpck
        -istrip -inlcr -igncr icrnl ixon -ixoff
        -iuclc -ixany -imaxbel -iutf8
        opost -olcuc -ocrnl onlcr -onocr -onlret
        -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
        isig icanon iexten -echo echoe echok
        -echonl -noflsh -xcase -tostop -echoprt
        echoctl echoke -flusho -extproc
        logout
    session_test.go:266: missing output from echo SHELL $SHELL
```

after

```
 go test -run ^TestValidTerminalMode -v
=== RUN   TestValidTerminalMode
    session_test.go:261: echo SHELL $SHELL && stty -a && exit:
        Last login: Thu Jul  6 12:24:38 2023 from 192.168.200.1
        bolian@ubuntu:~$
        SHELL /bin/bash
        speed 38400 baud; rows 80; columns 40;
        line = 0;
        intr = ^C; quit = ^\; erase = ^?;
        kill = ^U; eof = ^D; eol = <undef>;
        eol2 = <undef>; swtch = <undef>;
        start = ^Q; stop = ^S; susp = ^Z;
        rprnt = ^R; werase = ^W; lnext = ^V;
        discard = ^O; min = 1; time = 0;
        -parenb -parodd -cmspar cs8 -hupcl
        -cstopb cread -clocal -crtscts
        -ignbrk -brkint -ignpar -parmrk -inpck
        -istrip -inlcr -igncr icrnl ixon -ixoff
        -iuclc -ixany -imaxbel -iutf8
        opost -olcuc -ocrnl onlcr -onocr -onlret
        -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
        isig icanon iexten -echo echoe echok
        -echonl -noflsh -xcase -tostop -echoprt
        echoctl echoke -flusho -extproc
        logout
--- PASS: TestValidTerminalMode (0.06s)
```

Change-Id: If60c040edb8c78a7d86bf58a6be47636d9e8f173
GitHub-Last-Rev: a2cc1b1af09e47df82fcb8685d829dfed945e8b0
GitHub-Pull-Request: golang/crypto#264
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/508115
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Heschi Kreinick <heschi@google.com>
Auto-Submit: Heschi Kreinick <heschi@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>

go.mod

@@ -3,9 +3,9 @@ module golang.org/x/crypto
 go 1.17
 
 require (
-	golang.org/x/net v0.10.0
-	golang.org/x/sys v0.8.0
-	golang.org/x/term v0.8.0
+	golang.org/x/net v0.10.0 // tagx:ignore
+	golang.org/x/sys v0.10.0
+	golang.org/x/term v0.10.0
 )
 
-require golang.org/x/text v0.9.0 // indirect
+require golang.org/x/text v0.11.0 // indirect

go.sum

@@ -18,19 +18,22 @@ golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBc
 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 v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.8.0 h1:EBmGv8NaZBZTWvrbjNoL6HVt+IVy3QDQpJs7VRIw3tU=
 golang.org/x/sys v0.8.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.10.0 h1:SqMFp9UcQJZa+pmYuAKjd9xq1f0j5rLcDIk0mj4qAsA=
+golang.org/x/sys v0.10.0/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 v0.5.0/go.mod h1:jMB1sMXY+tzblOD4FWmEbocvup2/aLOaQEp7JmGp78k=
-golang.org/x/term v0.8.0 h1:n5xxQn2i3PC0yLAbjTpNT85q/Kgzcr2gIoX9OrJUols=
 golang.org/x/term v0.8.0/go.mod h1:xPskH00ivmX89bAKVGSKKtLOWNx2+17Eiy94tnKShWo=
+golang.org/x/term v0.10.0 h1:3R7pNqamzBraeqj/Tj8qt1aQ2HpmlC+Cx/qL/7hn4/c=
+golang.org/x/term v0.10.0/go.mod h1:lpqdcUyK/oCiQxvxVrppt5ggO2KCZ5QblwqPnfZ6d5o=
 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 v0.7.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
-golang.org/x/text v0.9.0 h1:2sjJmO8cDvYveuX97RDLsxlyUxLl+GHoLxBiRdHllBE=
 golang.org/x/text v0.9.0/go.mod h1:e1OnstbJyHTd6l/uOt8jFFHp6TRDWZR/bV3emEE/zU8=
+golang.org/x/text v0.11.0 h1:LAntKIrcmeSKERyiOh0XMV39LXS8IE9UL2yP7+f5ij4=
+golang.org/x/text v0.11.0/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=

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

ssh/client_auth_test.go

@@ -955,3 +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/common.go

@@ -85,7 +85,7 @@ 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}
@@ -119,6 +119,13 @@ 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

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/server.go

@@ -370,6 +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
@@ -567,7 +586,7 @@ userAuthLoop:
 					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/test/agent_unix_test.go

@@ -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

@@ -13,7 +13,6 @@ import (
 
 func TestBannerCallbackAgainstOpenSSH(t *testing.T) {
 	server := newServer(t)
-	defer server.Shutdown()
 
 	clientConf := clientConfig()
 

ssh/test/cert_test.go

@@ -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

@@ -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

@@ -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

@@ -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

@@ -25,7 +25,6 @@ import (
 
 func TestRunCommandSuccess(t *testing.T) {
 	server := newServer(t)
-	defer server.Shutdown()
 	conn := server.Dial(clientConfig())
 	defer conn.Close()
 
@@ -42,7 +41,6 @@ func TestRunCommandSuccess(t *testing.T) {
 
 func TestHostKeyCheck(t *testing.T) {
 	server := newServer(t)
-	defer server.Shutdown()
 
 	conf := clientConfig()
 	hostDB := hostKeyDB()
@@ -64,7 +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()
 
@@ -87,7 +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()
 
@@ -111,7 +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()
 
@@ -128,7 +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()
 
@@ -148,7 +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()
 
@@ -180,7 +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
@@ -227,7 +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()
 
@@ -257,7 +248,7 @@ func TestValidTerminalMode(t *testing.T) {
 		t.Fatalf("session failed: %s", err)
 	}
 
-	if _, err := io.WriteString(stdin, "echo SHELL $SHELL && stty -a && exit\n"); err != nil {
+	if _, err := io.WriteString(stdin, "echo && echo SHELL $SHELL && stty -a && exit\n"); err != nil {
 		t.Fatal(err)
 	}
 
@@ -267,7 +258,7 @@ func TestValidTerminalMode(t *testing.T) {
 	}
 
 	if testing.Verbose() {
-		t.Logf("echo SHELL $SHELL && stty -a && exit:\n%s", buf)
+		t.Logf("echo && echo SHELL $SHELL && stty -a && exit:\n%s", buf)
 	}
 
 	shellLine := regexp.MustCompile("(?m)^SHELL (.*)$").FindStringSubmatch(buf.String())
@@ -292,7 +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()
 
@@ -340,7 +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.
@@ -399,7 +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.
@@ -425,7 +413,6 @@ func TestKeyExchanges(t *testing.T) {
 	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...)
@@ -460,8 +447,6 @@ func TestClientAuthAlgorithms(t *testing.T) {
 			} else {
 				t.Errorf("failed for key %q", key)
 			}
-
-			server.Shutdown()
 		})
 	}
 }

ssh/test/test_unix_test.go

@@ -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)
-			}
-		},
 	}
 }
 

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
+}