Merge branch 'main' into embedded-vnc

client/ssh/handshake.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"io"
 	"net"
-	"time"
 
 	log "github.com/sirupsen/logrus"
 	"golang.org/x/crypto/ssh"
@@ -13,26 +12,23 @@ import (
 
 // Handshake runs the SSH client handshake on an already dialed conn and
 // returns the resulting client. Dialing bounds only the TCP establishment;
-// without a deadline on the socket a peer that accepts and then goes silent
-// blocks the handshake forever, so the context deadline is applied to conn
-// for the duration of the handshake. conn is closed on any error.
+// a peer that accepts and then goes silent would block the handshake forever,
+// so conn is closed as soon as ctx is done, which unblocks the handshake and
+// surfaces the context error. conn is closed on any error.
 func Handshake(ctx context.Context, conn net.Conn, addr string, config *ssh.ClientConfig) (*ssh.Client, error) {
-	if deadline, ok := ctx.Deadline(); ok {
-		if err := conn.SetDeadline(deadline); err != nil {
-			closeHandshake(conn, "conn after deadline error")
-			return nil, fmt.Errorf("set handshake deadline: %w", err)
-		}
-	}
+	stop := context.AfterFunc(ctx, func() { closeHandshake(conn, "conn on context done") })
 
 	sshConn, chans, reqs, err := ssh.NewClientConn(conn, addr, config)
 	if err != nil {
-		closeHandshake(conn, "conn after handshake error")
-		return nil, fmt.Errorf("ssh handshake: %w", err)
+		if stop() {
+			closeHandshake(conn, "conn after handshake error")
+		}
+		return nil, handshakeError(ctx, err)
 	}
 
-	if err := conn.SetDeadline(time.Time{}); err != nil {
-		closeHandshake(sshConn, "ssh conn after deadline clear error")
-		return nil, fmt.Errorf("clear handshake deadline: %w", err)
+	if !stop() {
+		closeHandshake(sshConn, "ssh conn after context done")
+		return nil, fmt.Errorf("ssh handshake: %w", ctx.Err())
 	}
 
 	return ssh.NewClient(sshConn, chans, reqs), nil
@@ -43,3 +39,10 @@ func closeHandshake(c io.Closer, label string) {
 		log.Debugf("ssh: close %s: %v", label, err)
 	}
 }
+
+func handshakeError(ctx context.Context, err error) error {
+	if ctxErr := ctx.Err(); ctxErr != nil {
+		return fmt.Errorf("ssh handshake: %w: %w", ctxErr, err)
+	}
+	return fmt.Errorf("ssh handshake: %w", err)
+}

client/ssh/handshake_test.go

@@ -0,0 +1,90 @@
+package ssh
+
+import (
+	"context"
+	"errors"
+	"net"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	"golang.org/x/crypto/ssh"
+)
+
+func TestHandshake_ContextDeadlineWrapped(t *testing.T) {
+	conn := dialSilentServer(t)
+
+	ctx, cancel := context.WithTimeout(context.Background(), 50*time.Millisecond)
+	defer cancel()
+
+	_, err := Handshake(ctx, conn, conn.RemoteAddr().String(), testClientConfig())
+	require.Error(t, err)
+	require.True(t, errors.Is(err, context.DeadlineExceeded), "expected context.DeadlineExceeded, got: %v", err)
+}
+
+func TestHandshake_ContextCancelUnblocks(t *testing.T) {
+	conn := dialSilentServer(t)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	time.AfterFunc(50*time.Millisecond, cancel)
+
+	errCh := make(chan error, 1)
+	go func() {
+		_, err := Handshake(ctx, conn, conn.RemoteAddr().String(), testClientConfig())
+		errCh <- err
+	}()
+
+	select {
+	case err := <-errCh:
+		require.Error(t, err)
+		require.True(t, errors.Is(err, context.Canceled), "expected context.Canceled, got: %v", err)
+	case <-time.After(5 * time.Second):
+		t.Fatal("handshake did not return after context cancellation")
+	}
+}
+
+func TestHandshake_NonContextErrorNotWrapped(t *testing.T) {
+	conn := dialSilentServer(t)
+	require.NoError(t, conn.Close())
+
+	_, err := Handshake(context.Background(), conn, conn.RemoteAddr().String(), testClientConfig())
+	require.Error(t, err)
+	require.False(t, errors.Is(err, context.Canceled))
+	require.False(t, errors.Is(err, context.DeadlineExceeded))
+}
+
+func testClientConfig() *ssh.ClientConfig {
+	return &ssh.ClientConfig{
+		User:            "test",
+		HostKeyCallback: ssh.InsecureIgnoreHostKey(),
+	}
+}
+
+// dialSilentServer returns a client conn to a server that accepts and never
+// sends anything, so the SSH handshake blocks until the context is done.
+func dialSilentServer(t *testing.T) net.Conn {
+	t.Helper()
+
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	require.NoError(t, err)
+	t.Cleanup(func() { _ = listener.Close() })
+
+	done := make(chan struct{})
+	t.Cleanup(func() { close(done) })
+
+	go func() {
+		c, err := listener.Accept()
+		if err != nil {
+			return
+		}
+		defer func() { _ = c.Close() }()
+		<-done
+	}()
+
+	conn, err := net.Dial("tcp", listener.Addr().String())
+	require.NoError(t, err)
+	t.Cleanup(func() { _ = conn.Close() })
+
+	return conn
+}