982eec1 fix(remote): harden udp bootstrap lifetime · vev-vt

M internal/adapters/dgram/ssh_dialer.go +13 -0


@@ -27,6 +27,7 @@ type bootstrapProcess interface {
27	27		StdoutPipe() (io.ReadCloser, error)
28	28		Start() error
29	29		Kill() error
	30	+	Wait() error
30	31		}
31	32
32	33		type execBootstrapProcess struct{ cmd *exec.Cmd }

@@ -34,6 +35,7 @@ type execBootstrapProcess struct{ cmd *exec.Cmd }
34	35		func (p execBootstrapProcess) StdoutPipe() (io.ReadCloser, error) { return p.cmd.StdoutPipe() }
35	36		func (p execBootstrapProcess) Start() error { return p.cmd.Start() }
36	37		func (p execBootstrapProcess) Kill() error { return p.cmd.Process.Kill() }
	38	+	func (p execBootstrapProcess) Wait() error { return p.cmd.Wait() }
37	39
38	40		var (
39	41		startUDPBootstrap = func(ctx context.Context, target, session string, stderr io.Writer) bootstrapProcess {

@@ -98,10 +100,14 @@ func (d RemoteDialer) Dial(ctx context.Context) (ports.Transport, error) {
98	100		return nil, udpUnavailable("start bootstrap", err, &stderr)
99	101		}
100	102		cleanup := true
	103	+	waited := false
101	104		defer func() {
102	105		if cleanup {
103	106		_ = proc.Kill()
104	107		}
	108	+	if !waited {
	109	+	_ = proc.Wait()
	110	+	}
105	111		_ = stdout.Close()
106	112		}()
107	113

@@ -109,6 +115,13 @@ func (d RemoteDialer) Dial(ctx context.Context) (ports.Transport, error) {
109	115		if err != nil {
110	116		return nil, udpUnavailable("read bootstrap readiness", err, &stderr)
111	117		}
	118	+	if err := proc.Wait(); err != nil {
	119	+	waited = true
	120	+	cleanup = false
	121	+	return nil, udpUnavailable("wait bootstrap", err, &stderr)
	122	+	}
	123	+	waited = true
	124	+	cleanup = false
112	125		peer, err := net.ResolveUDPAddr("udp", net.JoinHostPort(sshTargetHost(d.Target), strconv.Itoa(ready.port)))
113	126		if err != nil {
114	127		return nil, udpUnavailable("resolve UDP peer", err, &stderr)


@@ -27,6 +27,7 @@ type bootstrapProcess interface {
27	StdoutPipe() (io.ReadCloser, error)	27		StdoutPipe() (io.ReadCloser, error)
28	Start() error	28		Start() error
29	Kill() error	29		Kill() error
		30	+	Wait() error
30	}	31		}
31		32
32	type execBootstrapProcess struct{ cmd *exec.Cmd }	33		type execBootstrapProcess struct{ cmd *exec.Cmd }

@@ -34,6 +35,7 @@ type execBootstrapProcess struct{ cmd *exec.Cmd }
34	func (p execBootstrapProcess) StdoutPipe() (io.ReadCloser, error) { return p.cmd.StdoutPipe() }	35		func (p execBootstrapProcess) StdoutPipe() (io.ReadCloser, error) { return p.cmd.StdoutPipe() }
35	func (p execBootstrapProcess) Start() error { return p.cmd.Start() }	36		func (p execBootstrapProcess) Start() error { return p.cmd.Start() }
36	func (p execBootstrapProcess) Kill() error { return p.cmd.Process.Kill() }	37		func (p execBootstrapProcess) Kill() error { return p.cmd.Process.Kill() }
		38	+	func (p execBootstrapProcess) Wait() error { return p.cmd.Wait() }
37		39
38	var (	40		var (
39	startUDPBootstrap = func(ctx context.Context, target, session string, stderr io.Writer) bootstrapProcess {	41		startUDPBootstrap = func(ctx context.Context, target, session string, stderr io.Writer) bootstrapProcess {

@@ -98,10 +100,14 @@ func (d RemoteDialer) Dial(ctx context.Context) (ports.Transport, error) {
98	return nil, udpUnavailable("start bootstrap", err, &stderr)	100		return nil, udpUnavailable("start bootstrap", err, &stderr)
99	}	101		}
100	cleanup := true	102		cleanup := true
		103	+	waited := false
101	defer func() {	104		defer func() {
102	if cleanup {	105		if cleanup {
103	_ = proc.Kill()	106		_ = proc.Kill()
104	}	107		}
		108	+	if !waited {
		109	+	_ = proc.Wait()
		110	+	}
105	_ = stdout.Close()	111		_ = stdout.Close()
106	}()	112		}()
107		113

@@ -109,6 +115,13 @@ func (d RemoteDialer) Dial(ctx context.Context) (ports.Transport, error) {
109	if err != nil {	115		if err != nil {
110	return nil, udpUnavailable("read bootstrap readiness", err, &stderr)	116		return nil, udpUnavailable("read bootstrap readiness", err, &stderr)
111	}	117		}
		118	+	if err := proc.Wait(); err != nil {
		119	+	waited = true
		120	+	cleanup = false
		121	+	return nil, udpUnavailable("wait bootstrap", err, &stderr)
		122	+	}
		123	+	waited = true
		124	+	cleanup = false
112	peer, err := net.ResolveUDPAddr("udp", net.JoinHostPort(sshTargetHost(d.Target), strconv.Itoa(ready.port)))	125		peer, err := net.ResolveUDPAddr("udp", net.JoinHostPort(sshTargetHost(d.Target), strconv.Itoa(ready.port)))
113	if err != nil {	126		if err != nil {
114	return nil, udpUnavailable("resolve UDP peer", err, &stderr)	127		return nil, udpUnavailable("resolve UDP peer", err, &stderr)

M internal/adapters/dgram/ssh_dialer_test.go +33 -4


@@ -85,12 +85,15 @@ func TestStdioDialerUsesContextBeforeStartingSSH(t *testing.T) {
85	85		type fakeBootstrapProcess struct {
86	86		stdout io.ReadCloser
87	87		startErr error
	88	+	waitErr error
88	89		killed bool
	90	+	waited bool
89	91		}
90	92
91	93		func (p *fakeBootstrapProcess) StdoutPipe() (io.ReadCloser, error) { return p.stdout, nil }
92	94		func (p *fakeBootstrapProcess) Start() error { return p.startErr }
93	95		func (p *fakeBootstrapProcess) Kill() error { p.killed = true; return nil }
	96	+	func (p *fakeBootstrapProcess) Wait() error { p.waited = true; return p.waitErr }
94	97
95	98		func withBootstrapStarter(t *testing.T, fn func(context.Context, string, string, io.Writer) bootstrapProcess) {
96	99		t.Helper()

@@ -115,14 +118,19 @@ func TestRemoteDialerUDPBootstrapFailures(t *testing.T) {
115	118		listen error
116	119		want string
117	120		killed bool
	121	+	waited bool
118	122		}{
119	123		{name: "start failure", start: errors.New("ssh missing"), want: "vev: remote UDP transport unavailable: start bootstrap: ssh missing"},
120		-	{name: "malformed readiness", stdout: "hello\n", want: "malformed readiness line", killed: true},
121		-	{name: "packet listen failure", stdout: "VEV-UDP 4444 " + key + "\n", listen: errors.New("bind denied"), want: "listen UDP: bind denied", killed: true},
	124	+	{name: "malformed readiness", stdout: "hello\n", want: "malformed readiness line", killed: true, waited: true},
	125	+	{name: "bootstrap wait failure", stdout: "VEV-UDP 4444 " + key + "\n", want: "wait bootstrap: exit status 255", waited: true},
	126	+	{name: "packet listen failure", stdout: "VEV-UDP 4444 " + key + "\n", listen: errors.New("bind denied"), want: "listen UDP: bind denied", waited: true},
122	127		}
123	128		for _, tt := range tests {
124	129		t.Run(tt.name, func(t *testing.T) {
125	130		proc := &fakeBootstrapProcess{stdout: io.NopCloser(strings.NewReader(tt.stdout)), startErr: tt.start}
	131	+	if tt.name == "bootstrap wait failure" {
	132	+	proc.waitErr = errors.New("exit status 255")
	133	+	}
126	134		withBootstrapStarter(t, func(context.Context, string, string, io.Writer) bootstrapProcess { return proc })
127	135		if tt.listen != nil {
128	136		withListenUDP(t, func(context.Context) (net.PacketConn, error) { return nil, tt.listen })

@@ -137,10 +145,28 @@ func TestRemoteDialerUDPBootstrapFailures(t *testing.T) {
137	145		if proc.killed != tt.killed {
138	146		t.Fatalf("killed=%v, want %v", proc.killed, tt.killed)
139	147		}
	148	+	if proc.waited != tt.waited {
	149	+	t.Fatalf("waited=%v, want %v", proc.waited, tt.waited)
	150	+	}
140	151		})
141	152		}
142	153		}
143	154
	155	+	func TestListenUDPPacketUsesDualStackWildcard(t *testing.T) {
	156	+	pc, err := listenUDPPacket(context.Background())
	157	+	if err != nil {
	158	+	t.Fatal(err)
	159	+	}
	160	+	defer func() { _ = pc.Close() }()
	161	+	addr, ok := pc.LocalAddr().(*net.UDPAddr)
	162	+	if !ok {
	163	+	t.Fatalf("local addr = %T, want *net.UDPAddr", pc.LocalAddr())
	164	+	}
	165	+	if !addr.IP.IsUnspecified() {
	166	+	t.Fatalf("listen IP = %v, want unspecified wildcard", addr.IP)
	167	+	}
	168	+	}
	169	+
144	170		func TestRemoteDialerProbeFailureCleansUpWithoutStdioFallback(t *testing.T) {
145	171		key := base64.StdEncoding.EncodeToString(make([]byte, pdgram.KeySize))
146	172		proc := &fakeBootstrapProcess{stdout: io.NopCloser(strings.NewReader("VEV-UDP 4444 " + key + "\n"))}

@@ -170,8 +196,11 @@ func TestRemoteDialerProbeFailureCleansUpWithoutStdioFallback(t *testing.T) {
170	196		if !closed {
171	197		t.Fatal("packet conn not closed after probe failure")
172	198		}
173		-	if !proc.killed {
174		-	t.Fatal("bootstrap process not killed after probe failure")
	199	+	if proc.killed {
	200	+	t.Fatal("bootstrap process killed after it was already waited")
	201	+	}
	202	+	if !proc.waited {
	203	+	t.Fatal("bootstrap process not waited after probe failure")
175	204		}
176	205		}
177	206

 type fakeBootstrapProcess struct {
 	stdout   io.ReadCloser
 	startErr error
+	waitErr  error
 	killed   bool
+	waited   bool
 }
 func (p *fakeBootstrapProcess) StdoutPipe() (io.ReadCloser, error) { return p.stdout, nil }
 func (p *fakeBootstrapProcess) Start() error                       { return p.startErr }
 func (p *fakeBootstrapProcess) Kill() error                        { p.killed = true; return nil }
+func (p *fakeBootstrapProcess) Wait() error                        { p.waited = true; return p.waitErr }
 func withBootstrapStarter(t *testing.T, fn func(context.Context, string, string, io.Writer) bootstrapProcess) {
 	t.Helper()
 		listen error
 		want   string
 		killed bool
+		waited bool
 	}{
 		{name: "start failure", start: errors.New("ssh missing"), want: "vev: remote UDP transport unavailable: start bootstrap: ssh missing"},
-		{name: "malformed readiness", stdout: "hello\n", want: "malformed readiness line", killed: true},
+		{name: "malformed readiness", stdout: "hello\n", want: "malformed readiness line", killed: true, waited: true},
-		{name: "packet listen failure", stdout: "VEV-UDP 4444 " + key + "\n", listen: errors.New("bind denied"), want: "listen UDP: bind denied", killed: true},
+		{name: "bootstrap wait failure", stdout: "VEV-UDP 4444 " + key + "\n", want: "wait bootstrap: exit status 255", waited: true},
+		{name: "packet listen failure", stdout: "VEV-UDP 4444 " + key + "\n", listen: errors.New("bind denied"), want: "listen UDP: bind denied", waited: true},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			proc := &fakeBootstrapProcess{stdout: io.NopCloser(strings.NewReader(tt.stdout)), startErr: tt.start}
+			if tt.name == "bootstrap wait failure" {
+				proc.waitErr = errors.New("exit status 255")
+			}
 			withBootstrapStarter(t, func(context.Context, string, string, io.Writer) bootstrapProcess { return proc })
 			if tt.listen != nil {
 				withListenUDP(t, func(context.Context) (net.PacketConn, error) { return nil, tt.listen })
 			if proc.killed != tt.killed {
 				t.Fatalf("killed=%v, want %v", proc.killed, tt.killed)
 			}
+			if proc.waited != tt.waited {
+				t.Fatalf("waited=%v, want %v", proc.waited, tt.waited)
+			}
 		})
 	}
 }
+func TestListenUDPPacketUsesDualStackWildcard(t *testing.T) {
+	pc, err := listenUDPPacket(context.Background())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() { _ = pc.Close() }()
+	addr, ok := pc.LocalAddr().(*net.UDPAddr)
+	if !ok {
+		t.Fatalf("local addr = %T, want *net.UDPAddr", pc.LocalAddr())
+	}
+	if !addr.IP.IsUnspecified() {
+		t.Fatalf("listen IP = %v, want unspecified wildcard", addr.IP)
+	}
+}
 func TestRemoteDialerProbeFailureCleansUpWithoutStdioFallback(t *testing.T) {
 	key := base64.StdEncoding.EncodeToString(make([]byte, pdgram.KeySize))
 	proc := &fakeBootstrapProcess{stdout: io.NopCloser(strings.NewReader("VEV-UDP 4444 " + key + "\n"))}
 	if !closed {
 		t.Fatal("packet conn not closed after probe failure")
 	}
-	if !proc.killed {
+	if proc.killed {
-		t.Fatal("bootstrap process not killed after probe failure")
+		t.Fatal("bootstrap process killed after it was already waited")
+	}
+	if !proc.waited {
+		t.Fatal("bootstrap process not waited after probe failure")
 	}
 }

M internal/app/remote.go +16 -0


@@ -11,6 +11,22 @@ func parseRemoteAttachTarget(s string) (target, session string, ok bool) {
11	11		return "", "", false
12	12		}
13	13		afterAt := s[at+1:]
	14	+	if strings.HasPrefix(afterAt, "[") {
	15	+	closeBracket := strings.IndexByte(afterAt, ']')
	16	+	if closeBracket < 0 {
	17	+	return "", "", false
	18	+	}
	19	+	suffix := afterAt[closeBracket+1:]
	20	+	switch {
	21	+	case suffix == "":
	22	+	return s, "", true
	23	+	case strings.HasPrefix(suffix, ":"):
	24	+	targetEnd := at + 1 + closeBracket + 1
	25	+	return s[:targetEnd], suffix[1:], true
	26	+	default:
	27	+	return "", "", false
	28	+	}
	29	+	}
14	30		colon := strings.LastIndexByte(afterAt, ':')
15	31		if colon < 0 {
16	32		return s, "", true


@@ -11,6 +11,22 @@ func parseRemoteAttachTarget(s string) (target, session string, ok bool) {
11	return "", "", false	11		return "", "", false
12	}	12		}
13	afterAt := s[at+1:]	13		afterAt := s[at+1:]
		14	+	if strings.HasPrefix(afterAt, "[") {
		15	+	closeBracket := strings.IndexByte(afterAt, ']')
		16	+	if closeBracket < 0 {
		17	+	return "", "", false
		18	+	}
		19	+	suffix := afterAt[closeBracket+1:]
		20	+	switch {
		21	+	case suffix == "":
		22	+	return s, "", true
		23	+	case strings.HasPrefix(suffix, ":"):
		24	+	targetEnd := at + 1 + closeBracket + 1
		25	+	return s[:targetEnd], suffix[1:], true
		26	+	default:
		27	+	return "", "", false
		28	+	}
		29	+	}
14	colon := strings.LastIndexByte(afterAt, ':')	30		colon := strings.LastIndexByte(afterAt, ':')
15	if colon < 0 {	31		if colon < 0 {
16	return s, "", true	32		return s, "", true

M internal/app/remote_test.go +3 -0


@@ -17,6 +17,9 @@ func TestParseRemoteAttachTarget(t *testing.T) {
17	17		{name: "remote no session", input: "user@example.com", wantTarget: "user@example.com", wantOK: true},
18	18		{name: "remote with session", input: "user@example.com:work", wantTarget: "user@example.com", wantSession: "work", wantOK: true},
19	19		{name: "remote empty session allowed", input: "user@example.com:", wantTarget: "user@example.com", wantOK: true},
	20	+	{name: "bracketed ipv6 no session", input: "user@[2001:db8::1]", wantTarget: "user@[2001:db8::1]", wantOK: true},
	21	+	{name: "bracketed ipv6 with session", input: "user@[2001:db8::1]:work", wantTarget: "user@[2001:db8::1]", wantSession: "work", wantOK: true},
	22	+	{name: "malformed bracketed ipv6", input: "user@[2001:db8::1"},
20	23		{name: "target with at in userinfo", input: "first@user@example.com:work", wantTarget: "first@user@example.com", wantSession: "work", wantOK: true},
21	24		}
22	25


@@ -17,6 +17,9 @@ func TestParseRemoteAttachTarget(t *testing.T) {
17	{name: "remote no session", input: "user@example.com", wantTarget: "user@example.com", wantOK: true},	17		{name: "remote no session", input: "user@example.com", wantTarget: "user@example.com", wantOK: true},
18	{name: "remote with session", input: "user@example.com:work", wantTarget: "user@example.com", wantSession: "work", wantOK: true},	18		{name: "remote with session", input: "user@example.com:work", wantTarget: "user@example.com", wantSession: "work", wantOK: true},
19	{name: "remote empty session allowed", input: "user@example.com:", wantTarget: "user@example.com", wantOK: true},	19		{name: "remote empty session allowed", input: "user@example.com:", wantTarget: "user@example.com", wantOK: true},
		20	+	{name: "bracketed ipv6 no session", input: "user@[2001:db8::1]", wantTarget: "user@[2001:db8::1]", wantOK: true},
		21	+	{name: "bracketed ipv6 with session", input: "user@[2001:db8::1]:work", wantTarget: "user@[2001:db8::1]", wantSession: "work", wantOK: true},
		22	+	{name: "malformed bracketed ipv6", input: "user@[2001:db8::1"},
20	{name: "target with at in userinfo", input: "first@user@example.com:work", wantTarget: "first@user@example.com", wantSession: "work", wantOK: true},	23		{name: "target with at in userinfo", input: "first@user@example.com:work", wantTarget: "first@user@example.com", wantSession: "work", wantOK: true},
21	}	24		}
22		25

M internal/app/run.go +12 -3


@@ -646,10 +646,17 @@ func runUDPBootstrap(ctx context.Context, session string) error {
646	646		if session != "" {
647	647		args = append(args, session)
648	648		}
	649	+	devNull, err := os.OpenFile(os.DevNull, os.O_RDWR, 0)
	650	+	if err != nil {
	651	+	_ = w.Close()
	652	+	return err
	653	+	}
	654	+	defer func() { _ = devNull.Close() }()
	655	+
649	656		cmd := udpProxyCommand(ctx, exe, args...)
650		-	cmd.Stdin = nil
	657	+	cmd.Stdin = devNull
651	658		cmd.Stdout = w
652		-	cmd.Stderr = os.Stderr
	659	+	cmd.Stderr = devNull
653	660		cmd.SysProcAttr = &syscall.SysProcAttr{Setsid: true}
654	661		if err := cmd.Start(); err != nil {
655	662		_ = w.Close()

@@ -677,9 +684,11 @@ func runUDPBootstrap(ctx context.Context, session string) error {
677	684		_, err := fmt.Fprint(os.Stdout, line)
678	685		return err
679	686		case err := <-errCh:
	687	+	_ = cmd.Wait()
680	688		return err
681	689		case <-readyCtx.Done():
682	690		_ = cmd.Process.Kill()
	691	+	_ = cmd.Wait()
683	692		return fmt.Errorf("vev: udp bootstrap readiness: %w", readyCtx.Err())
684	693		}
685	694		}

@@ -694,7 +703,7 @@ func runUDPProxy(ctx context.Context, session string, ready io.Writer) error {
694	703		log.Debug("udp proxy starting", "session", session)
695	704
696	705		var lc net.ListenConfig
697		-	conn, err := lc.ListenPacket(ctx, "udp", "0.0.0.0:0")
	706	+	conn, err := lc.ListenPacket(ctx, "udp", ":0")
698	707		if err != nil {
699	708		return err
700	709		}

 	if session != "" {
 		args = append(args, session)
 	}
+	devNull, err := os.OpenFile(os.DevNull, os.O_RDWR, 0)
+	if err != nil {
+		_ = w.Close()
+		return err
+	}
+	defer func() { _ = devNull.Close() }()
 	cmd := udpProxyCommand(ctx, exe, args...)
-	cmd.Stdin = nil
+	cmd.Stdin = devNull
 	cmd.Stdout = w
-	cmd.Stderr = os.Stderr
+	cmd.Stderr = devNull
 	cmd.SysProcAttr = &syscall.SysProcAttr{Setsid: true}
 	if err := cmd.Start(); err != nil {
 		_ = w.Close()
 		_, err := fmt.Fprint(os.Stdout, line)
 		return err
 	case err := <-errCh:
+		_ = cmd.Wait()
 		return err
 	case <-readyCtx.Done():
 		_ = cmd.Process.Kill()
+		_ = cmd.Wait()
 		return fmt.Errorf("vev: udp bootstrap readiness: %w", readyCtx.Err())
 	}
 }
 	log.Debug("udp proxy starting", "session", session)
 	var lc net.ListenConfig
-	conn, err := lc.ListenPacket(ctx, "udp", "0.0.0.0:0")
+	conn, err := lc.ListenPacket(ctx, "udp", ":0")
 	if err != nil {
 		return err
 	}

M internal/app/run_test.go +8 -0


@@ -575,9 +575,11 @@ func TestRunUDPBootstrapForwardsReadinessAndExits(t *testing.T) {
575	575		t.Fatal(err)
576	576		}
577	577		defer func() { _ = r.Close() }()
	578	+	var gotCmd *exec.Cmd
578	579		udpProxyCommand = func(context.Context, string, ...string) *exec.Cmd {
579	580		cmd := exec.Command("/bin/sh", "-c", "printf 'VEV-UDP 4242 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=\\n'")
580	581		cmd.Stdout = w
	582	+	gotCmd = cmd
581	583		return cmd
582	584		}
583	585		t.Cleanup(func() { udpProxyCommand = oldCommand })

@@ -591,4 +593,10 @@ func TestRunUDPBootstrapForwardsReadinessAndExits(t *testing.T) {
591	593		if got != "VEV-UDP 4242 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=\n" {
592	594		t.Fatalf("readiness = %q", got)
593	595		}
	596	+	if gotCmd.Stdin == nil \|\| gotCmd.Stderr == nil {
	597	+	t.Fatalf("proxy stdio = stdin %T stderr %T, want detached from SSH channels", gotCmd.Stdin, gotCmd.Stderr)
	598	+	}
	599	+	if gotCmd.Stdout == os.Stdout \|\| gotCmd.Stderr == os.Stderr \|\| gotCmd.Stdin == os.Stdin {
	600	+	t.Fatalf("proxy inherited SSH stdio handles")
	601	+	}
594	602		}


@@ -575,9 +575,11 @@ func TestRunUDPBootstrapForwardsReadinessAndExits(t *testing.T) {
575	t.Fatal(err)	575		t.Fatal(err)
576	}	576		}
577	defer func() { _ = r.Close() }()	577		defer func() { _ = r.Close() }()
		578	+	var gotCmd *exec.Cmd
578	udpProxyCommand = func(context.Context, string, ...string) *exec.Cmd {	579		udpProxyCommand = func(context.Context, string, ...string) *exec.Cmd {
579	cmd := exec.Command("/bin/sh", "-c", "printf 'VEV-UDP 4242 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=\\n'")	580		cmd := exec.Command("/bin/sh", "-c", "printf 'VEV-UDP 4242 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=\\n'")
580	cmd.Stdout = w	581		cmd.Stdout = w
		582	+	gotCmd = cmd
581	return cmd	583		return cmd
582	}	584		}
583	t.Cleanup(func() { udpProxyCommand = oldCommand })	585		t.Cleanup(func() { udpProxyCommand = oldCommand })

@@ -591,4 +593,10 @@ func TestRunUDPBootstrapForwardsReadinessAndExits(t *testing.T) {
591	if got != "VEV-UDP 4242 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=\n" {	593		if got != "VEV-UDP 4242 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=\n" {
592	t.Fatalf("readiness = %q", got)	594		t.Fatalf("readiness = %q", got)
593	}	595		}
		596	+	if gotCmd.Stdin == nil \|\| gotCmd.Stderr == nil {
		597	+	t.Fatalf("proxy stdio = stdin %T stderr %T, want detached from SSH channels", gotCmd.Stdin, gotCmd.Stderr)
		598	+	}
		599	+	if gotCmd.Stdout == os.Stdout \|\| gotCmd.Stderr == os.Stderr \|\| gotCmd.Stdin == os.Stdin {
		600	+	t.Fatalf("proxy inherited SSH stdio handles")
		601	+	}
594	}	602		}