Dummy file

client/android/ssh_client.go

@@ -1,829 +0,0 @@
-//go:build android
-
-package android
-
-import (
-	"bufio"
-	"bytes"
-	"context"
-	"errors"
-	"fmt"
-	"io"
-	"net"
-	"os"
-	"strconv"
-	"strings"
-	"sync"
-	"time"
-
-	log "github.com/sirupsen/logrus"
-	gossh "golang.org/x/crypto/ssh"
-	"golang.org/x/crypto/ssh/knownhosts"
-
-	"github.com/netbirdio/netbird/client/internal"
-	"github.com/netbirdio/netbird/client/internal/auth"
-	"github.com/netbirdio/netbird/client/internal/profilemanager"
-	nbssh "github.com/netbirdio/netbird/client/ssh"
-	"github.com/netbirdio/netbird/client/ssh/detection"
-)
-
-const (
-	sshDialTimeout      = 30 * time.Second
-	sshDetectionTimeout = 5 * time.Second
-)
-
-// PasswordRequiredMarker tells Java to prompt for a password and retry. It is
-// a string because gomobile flattens errors to their message, so a sentinel
-// value would not survive the binding.
-const PasswordRequiredMarker = "netbird-ssh-password-required"
-
-// HostKeyUnknownMarker tells Java to show the fingerprint and, on confirmation,
-// retry with TrustHostKey set. The presented fingerprint is appended after the
-// marker so the prompt can display it and the retry can guard against a key
-// that changed between the two connects. Only regular (non-NetBird) servers
-// reach this: NetBird peers verify against the registry.
-const HostKeyUnknownMarker = "netbird-ssh-hostkey-unknown"
-
-var (
-	errPasswordRequired = errors.New(PasswordRequiredMarker)
-	errClientClosed     = errors.New("ssh client closed")
-)
-
-// errHostKeyUnknown carries the presented fingerprint so Connect can build the
-// marker message the Java side parses.
-type errHostKeyUnknown struct {
-	fingerprint string
-}
-
-func (e *errHostKeyUnknown) Error() string {
-	return HostKeyUnknownMarker + ":" + e.fingerprint
-}
-
-// engineHostKeyVerifier adapts *internal.Engine to nbssh.HostKeyVerifier.
-type engineHostKeyVerifier struct {
-	engine *internal.Engine
-}
-
-func (v *engineHostKeyVerifier) VerifySSHHostKey(peerAddress string, presented []byte) error {
-	storedKey, found := v.engine.GetPeerSSHKey(peerAddress)
-	if !found {
-		return nbssh.ErrPeerNotFound
-	}
-	return nbssh.VerifyHostKey(storedKey, presented, peerAddress)
-}
-
-// SSHTerminalListener receives SSH session events. It is implemented in Java.
-//
-// All callbacks are invoked from goroutines and may run concurrently with each
-// other; the implementation must be safe to call from any thread.
-type SSHTerminalListener interface {
-	OnConnected()
-	OnData(data []byte)
-	OnClose(reason string)
-	OnError(message string)
-}
-
-// SSHClient is a NetBird-aware SSH client exposed to Java via gomobile.
-//
-// It dials through the running NetBird tunnel and runs a standard SSH session
-// on top with PTY enabled. Host-key verification uses the NetBird-provided
-// peer SSH host keys, identical to the desktop client.
-type SSHClient struct {
-	nb        *Client
-	mu        sync.Mutex
-	listener  SSHTerminalListener
-	urlOpener URLOpener
-
-	sshClient *gossh.Client
-	session   *gossh.Session
-	stdin     io.WriteCloser
-	closed    bool
-
-	// gen identifies the current connection attempt. Connect and Close bump it,
-	// so an in-flight dial or a reader left over from a previous connection
-	// finds itself stale and stays silent instead of publishing OnConnected or
-	// OnClose for a connection the caller already abandoned.
-	gen        uint64
-	dialCancel context.CancelFunc
-
-	// knownHostsPath is the TOFU store for regular SSH servers. Java supplies a
-	// per-profile path, since an overlay IP is a different host under a
-	// different profile. Empty until set: without it a regular server cannot be
-	// verified and Connect refuses one.
-	knownHostsPath string
-	// trustHostKey carries the fingerprint the user confirmed on a previous
-	// attempt, so the retry accepts exactly that key and persists it.
-	trustHostKey string
-}
-
-// NewSSHClient creates a new SSH client bound to the running NetBird Client.
-func NewSSHClient(c *Client) *SSHClient {
-	return &SSHClient{nb: c}
-}
-
-// SetListener registers the Java listener. Must be called before Connect to
-// receive any events.
-func (s *SSHClient) SetListener(l SSHTerminalListener) {
-	s.mu.Lock()
-	s.listener = l
-	s.mu.Unlock()
-}
-
-// SetURLOpener registers the Java URL opener used to display the device-code
-// authorization page in a Custom Tabs window when the target peer requires
-// JWT authentication. Must be set before Connect to be effective.
-func (s *SSHClient) SetURLOpener(opener URLOpener) {
-	s.mu.Lock()
-	s.urlOpener = opener
-	s.mu.Unlock()
-}
-
-// SetKnownHostsPath points the TOFU host-key store at a per-profile file. Must
-// be set before connecting to a regular SSH server; without it such a server
-// cannot be verified and Connect refuses one.
-func (s *SSHClient) SetKnownHostsPath(path string) {
-	s.mu.Lock()
-	s.knownHostsPath = path
-	s.mu.Unlock()
-}
-
-// TrustHostKey records the fingerprint the user confirmed for a regular server,
-// so the next Connect accepts that exact key and adds it to the known-hosts
-// store. Passing a fingerprint that no longer matches makes the connect fail
-// rather than trust a key that changed since the prompt.
-func (s *SSHClient) TrustHostKey(fingerprint string) {
-	s.mu.Lock()
-	s.trustHostKey = fingerprint
-	s.mu.Unlock()
-}
-
-// Connect dials the SSH server through the NetBird tunnel and performs the
-// SSH handshake. It auto-detects the server type via SSH banner inspection
-// and selects the appropriate authentication path:
-//
-//   - NetBird-SSH server requiring JWT: launches the OAuth 2.0 device-code
-//     flow, opens the verification URL through the registered URLOpener, and
-//     uses the resulting token as the SSH password. Host-key verification
-//     uses the NetBird peer registry.
-//   - NetBird-SSH server without JWT: authenticates with the NetBird SSH
-//     private key. Host-key verification uses the NetBird peer registry.
-//   - Regular SSH server (e.g. OpenSSH): authenticates with the NetBird key
-//     first (so a user-installed NetBird public key works), then falls back
-//     to the supplied password if non-empty. Host-key verification is
-//     trust-on-first-use against the per-profile known-hosts store.
-//
-// The password parameter is only consulted for regular SSH servers.
-func (s *SSHClient) Connect(host string, port int, user, password string) error {
-	if port < 1 || port > 65535 {
-		return fmt.Errorf("invalid port: %d", port)
-	}
-
-	cfg, _, cc := s.nb.stateSnapshot()
-	if cc == nil {
-		return errors.New("netbird client not running")
-	}
-	if cfg == nil {
-		return errors.New("netbird config not loaded")
-	}
-	engine := cc.Engine()
-	if engine == nil {
-		return errors.New("netbird engine not available")
-	}
-
-	s.mu.Lock()
-	s.gen++
-	gen := s.gen
-	s.mu.Unlock()
-
-	serverType := detectServerType(host, port)
-	log.Debugf("SSH server type: %s", serverType)
-
-	authMethods, hostKeyCallback, err := s.buildAuth(cfg, engine, serverType, password)
-	if err != nil {
-		return err
-	}
-
-	clientConfig := &gossh.ClientConfig{
-		User:            user,
-		Auth:            authMethods,
-		HostKeyCallback: hostKeyCallback,
-		Timeout:         sshDialTimeout,
-	}
-	err = s.dialAndHandshake(gen, host, port, clientConfig)
-
-	// An unknown host key is a prompt, not a failure: return the marker intact
-	// (rootCause would unwrap it) so Java can show the fingerprint and retry.
-	var unknownHost *errHostKeyUnknown
-	if errors.As(err, &unknownHost) {
-		return errors.New(unknownHost.Error())
-	}
-
-	// A regular server may still accept a password, so let the caller ask for
-	// one instead of failing. NetBird servers never use a password, so a
-	// failure there is genuine.
-	if err != nil && serverType != detection.ServerTypeNetBirdJWT &&
-		serverType != detection.ServerTypeNetBirdNoJWT && isAuthFailure(err) &&
-		passwordCouldHelp(err, password != "") {
-		return errPasswordRequired
-	}
-	if err != nil {
-		return rootCause(err)
-	}
-	return nil
-}
-
-// StartSession requests a PTY and starts an interactive shell. Output from
-// the session is forwarded to the listener via OnData.
-func (s *SSHClient) StartSession(cols, rows int) error {
-	err := s.startSession(cols, rows)
-	if err != nil {
-		log.Infof("SSH: start session failed: %v", err)
-		return rootCause(err)
-	}
-	return nil
-}
-
-// Write sends data to the SSH session stdin.
-func (s *SSHClient) Write(data []byte) error {
-	s.mu.Lock()
-	stdin := s.stdin
-	s.mu.Unlock()
-	if stdin == nil {
-		return errors.New("ssh session not started")
-	}
-	if _, err := stdin.Write(data); err != nil {
-		return fmt.Errorf("write stdin: %w", err)
-	}
-	return nil
-}
-
-// Resize updates the PTY window size.
-func (s *SSHClient) Resize(cols, rows int) error {
-	s.mu.Lock()
-	session := s.session
-	s.mu.Unlock()
-	if session == nil {
-		return errors.New("ssh session not started")
-	}
-	return session.WindowChange(rows, cols)
-}
-
-// Reset makes a closed client usable for another Connect: Close leaves the
-// one-shot guard set, and clearing it lets the same client back a reconnect.
-func (s *SSHClient) Reset() {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-	s.closed = false
-}
-
-// Close terminates the SSH session and underlying connection. Safe to call
-// multiple times.
-func (s *SSHClient) Close() error {
-	s.mu.Lock()
-	s.gen++
-	if s.dialCancel != nil {
-		s.dialCancel()
-		s.dialCancel = nil
-	}
-	sshClient := s.sshClient
-	session := s.session
-	stdin := s.stdin
-	s.sshClient = nil
-	s.session = nil
-	s.stdin = nil
-	notify := !s.closed
-	s.closed = true
-	listener := s.listener
-	s.mu.Unlock()
-
-	if stdin != nil {
-		if err := stdin.Close(); err != nil {
-			log.Debugf("ssh: stdin close: %v", err)
-		}
-	}
-	if session != nil {
-		if err := session.Close(); err != nil && !errors.Is(err, io.EOF) {
-			log.Debugf("ssh: session close: %v", err)
-		}
-	}
-	var firstErr error
-	if sshClient != nil {
-		if err := sshClient.Close(); err != nil {
-			firstErr = err
-		}
-	}
-	if notify && listener != nil {
-		listener.OnClose("closed by client")
-	}
-	return firstErr
-}
-
-func (s *SSHClient) startSession(cols, rows int) error {
-	log.Debugf("SSH: starting session %dx%d", cols, rows)
-	s.mu.Lock()
-	sshClient := s.sshClient
-	gen := s.gen
-	s.mu.Unlock()
-
-	if sshClient == nil {
-		return errors.New("ssh client not connected")
-	}
-
-	session, err := sshClient.NewSession()
-	if err != nil {
-		return fmt.Errorf("new session: %w", err)
-	}
-
-	modes := gossh.TerminalModes{
-		gossh.ECHO:          1,
-		gossh.TTY_OP_ISPEED: 14400,
-		gossh.TTY_OP_OSPEED: 14400,
-		gossh.VINTR:         3,
-		gossh.VQUIT:         28,
-		gossh.VERASE:        127,
-	}
-	if err := session.RequestPty("xterm-256color", rows, cols, modes); err != nil {
-		closeQuiet(session, "session after pty error")
-		return fmt.Errorf("request pty: %w", err)
-	}
-
-	stdin, err := session.StdinPipe()
-	if err != nil {
-		closeQuiet(session, "session after stdin error")
-		return fmt.Errorf("stdin pipe: %w", err)
-	}
-	stdout, err := session.StdoutPipe()
-	if err != nil {
-		closeQuiet(session, "session after stdout error")
-		return fmt.Errorf("stdout pipe: %w", err)
-	}
-	stderr, err := session.StderrPipe()
-	if err != nil {
-		closeQuiet(session, "session after stderr error")
-		return fmt.Errorf("stderr pipe: %w", err)
-	}
-
-	if err := session.Shell(); err != nil {
-		closeQuiet(session, "session after shell error")
-		return fmt.Errorf("start shell: %w", err)
-	}
-
-	s.mu.Lock()
-	if gen != s.gen {
-		s.mu.Unlock()
-		closeQuiet(session, "stale session")
-		return errClientClosed
-	}
-	s.session = session
-	s.stdin = stdin
-	s.mu.Unlock()
-
-	readerDone := make(chan string, 2)
-	go func() { readerDone <- s.readLoop(stdout, "stdout") }()
-	go func() { readerDone <- s.readLoop(stderr, "stderr") }()
-	go func() {
-		reason := <-readerDone
-		if second := <-readerDone; reason == "" {
-			reason = second
-		}
-		s.notifyClose(gen, reason)
-	}()
-	log.Debug("SSH: session started, shell running")
-	return nil
-}
-
-func (s *SSHClient) buildAuth(cfg *profilemanager.Config, engine *internal.Engine,
-	serverType detection.ServerType, password string) ([]gossh.AuthMethod, gossh.HostKeyCallback, error) {
-
-	switch serverType {
-	case detection.ServerTypeNetBirdJWT:
-		token, err := s.requestJWTToken(cfg)
-		if err != nil {
-			return nil, nil, fmt.Errorf("jwt: %w", err)
-		}
-		auths := []gossh.AuthMethod{gossh.Password(token)}
-		return auths, nbssh.CreateHostKeyCallback(&engineHostKeyVerifier{engine: engine}), nil
-
-	case detection.ServerTypeNetBirdNoJWT:
-		if cfg.SSHKey == "" {
-			return nil, nil, errors.New("no NetBird SSH key available")
-		}
-		signer, err := gossh.ParsePrivateKey([]byte(cfg.SSHKey))
-		if err != nil {
-			return nil, nil, fmt.Errorf("parse netbird ssh key: %w", err)
-		}
-		auths := []gossh.AuthMethod{gossh.PublicKeys(signer)}
-		return auths, nbssh.CreateHostKeyCallback(&engineHostKeyVerifier{engine: engine}), nil
-
-	case detection.ServerTypeRegular:
-		var auths []gossh.AuthMethod
-		if cfg.SSHKey != "" {
-			if signer, err := gossh.ParsePrivateKey([]byte(cfg.SSHKey)); err == nil {
-				auths = append(auths, gossh.PublicKeys(signer))
-			} else {
-				log.Debugf("ssh: parse netbird key for regular auth: %v", err)
-			}
-		}
-		if password != "" {
-			pw := password
-			auths = append(auths, gossh.Password(pw))
-			auths = append(auths, gossh.KeyboardInteractive(func(_, _ string, questions []string, _ []bool) ([]string, error) {
-				answers := make([]string, len(questions))
-				for i := range questions {
-					answers[i] = pw
-				}
-				return answers, nil
-			}))
-		}
-		if len(auths) == 0 {
-			// Nothing to offer at all: ask for a password rather than failing,
-			// so the caller can retry once the user supplies one.
-			return nil, nil, errPasswordRequired
-		}
-		callback, err := s.tofuHostKeyCallback()
-		if err != nil {
-			return nil, nil, err
-		}
-		return auths, callback, nil
-
-	default:
-		return nil, nil, fmt.Errorf("unsupported SSH server type: %v", serverType)
-	}
-}
-
-// tofuHostKeyCallback verifies a regular server's host key against the
-// per-profile known-hosts file. An unknown host returns errHostKeyUnknown so
-// Java can show the fingerprint and, once confirmed, retry with the key
-// trusted; a changed key is rejected outright, as OpenSSH does. When the user
-// has confirmed a fingerprint, the callback accepts exactly that key and
-// appends it to the store.
-func (s *SSHClient) tofuHostKeyCallback() (gossh.HostKeyCallback, error) {
-	s.mu.Lock()
-	path := s.knownHostsPath
-	trusted := s.trustHostKey
-	s.mu.Unlock()
-
-	if path == "" {
-		return nil, errors.New("no known-hosts store configured for regular SSH")
-	}
-
-	if err := ensureFileExists(path); err != nil {
-		return nil, fmt.Errorf("prepare known-hosts store: %w", err)
-	}
-
-	known, err := knownhosts.New(path)
-	if err != nil {
-		return nil, fmt.Errorf("load known-hosts store: %w", err)
-	}
-
-	return func(hostname string, remote net.Addr, key gossh.PublicKey) error {
-		err := known(hostname, remote, key)
-		if err == nil {
-			return nil
-		}
-
-		var keyErr *knownhosts.KeyError
-		if !errors.As(err, &keyErr) {
-			return err
-		}
-		// Want holds the keys already stored for this host: non-empty means the
-		// presented key replaced a known one, which TOFU must never accept
-		// silently.
-		if len(keyErr.Want) > 0 {
-			return fmt.Errorf("SSH host key changed for %s (possible attack)", hostname)
-		}
-
-		fingerprint := gossh.FingerprintSHA256(key)
-		if trusted == "" {
-			return &errHostKeyUnknown{fingerprint: fingerprint}
-		}
-		if trusted != fingerprint {
-			return fmt.Errorf("SSH host key changed since it was confirmed for %s", hostname)
-		}
-		if err := appendKnownHost(path, hostname, remote, key); err != nil {
-			return fmt.Errorf("persist trusted host key: %w", err)
-		}
-		// The confirmation is spent: now that the key is stored, a later
-		// reconnect must verify against the file, not re-accept this fingerprint.
-		s.mu.Lock()
-		s.trustHostKey = ""
-		s.mu.Unlock()
-		return nil
-	}, nil
-}
-
-func (s *SSHClient) requestJWTToken(cfg *profilemanager.Config) (string, error) {
-	s.mu.Lock()
-	urlOpener := s.urlOpener
-	s.mu.Unlock()
-	if urlOpener == nil {
-		return "", errors.New("URL opener not configured for JWT auth")
-	}
-
-	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
-	defer cancel()
-
-	flow, err := auth.NewOAuthFlow(ctx, cfg, false, true, profilemanager.GetLoginHint())
-	if err != nil {
-		return "", fmt.Errorf("create oauth flow: %w", err)
-	}
-
-	flowInfo, err := flow.RequestAuthInfo(ctx)
-	if err != nil {
-		return "", fmt.Errorf("request auth info: %w", err)
-	}
-
-	// Called synchronously: Open is what marks the surface as opened on the
-	// client side, and OnLoginSuccess below is a no-op until it has. Starting
-	// both in their own goroutines let them race, so a fast token left the
-	// browser in front of the terminal.
-	urlOpener.Open(flowInfo.VerificationURIComplete, flowInfo.UserCode)
-
-	// WaitToken blocks for as long as the browser round-trip takes, so say so
-	// rather than leaving the terminal blank.
-	s.notifyStatus("Waiting for browser authentication...")
-
-	tokenInfo, err := flow.WaitToken(ctx, flowInfo)
-	if err != nil {
-		return "", fmt.Errorf("wait for token: %w", err)
-	}
-
-	token := tokenInfo.GetTokenToUse()
-	if token == "" {
-		return "", errors.New("empty token returned by IdP")
-	}
-
-	// Tells the client the browser round-trip is over so it can dismiss the
-	// surface it opened, the same way the login and session-extend flows do.
-	// Without it the Custom Tab stays in front of the terminal even though the
-	// token has already been collected.
-	urlOpener.OnLoginSuccess()
-
-	return token, nil
-}
-
-func (s *SSHClient) dialAndHandshake(gen uint64, host string, port int, clientConfig *gossh.ClientConfig) error {
-	addr := net.JoinHostPort(host, strconv.Itoa(port))
-	ctx, cancel := context.WithTimeout(context.Background(), sshDialTimeout)
-	defer cancel()
-
-	s.mu.Lock()
-	if gen != s.gen {
-		s.mu.Unlock()
-		return errClientClosed
-	}
-	s.dialCancel = cancel
-	s.mu.Unlock()
-
-	var dialer net.Dialer
-	conn, err := dialer.DialContext(ctx, "tcp", addr)
-	if err != nil {
-		return fmt.Errorf("dial %s: %w", addr, err)
-	}
-
-	// DialContext bounds only the TCP establishment; without a deadline on the
-	// socket a peer that accepts and then goes silent blocks the handshake
-	// forever.
-	if deadline, ok := ctx.Deadline(); ok {
-		if err := conn.SetDeadline(deadline); err != nil {
-			closeQuiet(conn, "conn after deadline error")
-			return fmt.Errorf("set handshake deadline: %w", err)
-		}
-	}
-
-	sshConn, chans, reqs, err := gossh.NewClientConn(conn, addr, clientConfig)
-	if err != nil {
-		if cerr := conn.Close(); cerr != nil {
-			log.Debugf("ssh: close after handshake error: %v", cerr)
-		}
-		return fmt.Errorf("ssh handshake: %w", err)
-	}
-
-	if err := conn.SetDeadline(time.Time{}); err != nil {
-		closeQuiet(sshConn, "ssh conn after deadline clear error")
-		return fmt.Errorf("clear handshake deadline: %w", err)
-	}
-
-	client := gossh.NewClient(sshConn, chans, reqs)
-	s.mu.Lock()
-	if gen != s.gen {
-		s.mu.Unlock()
-		closeQuiet(client, "stale ssh client")
-		return errClientClosed
-	}
-	s.sshClient = client
-	listener := s.listener
-	s.mu.Unlock()
-
-	if listener != nil {
-		listener.OnConnected()
-	}
-	return nil
-}
-
-func (s *SSHClient) readLoop(r io.Reader, name string) string {
-	buf := make([]byte, 4096)
-	for {
-		n, err := r.Read(buf)
-		if n > 0 {
-			s.mu.Lock()
-			listener := s.listener
-			s.mu.Unlock()
-			if listener != nil {
-				chunk := make([]byte, n)
-				copy(chunk, buf[:n])
-				listener.OnData(chunk)
-			}
-		}
-		if err != nil {
-			// EOF is a normal shell exit, so report it without a reason.
-			if errors.Is(err, io.EOF) {
-				return ""
-			}
-			log.Debugf("ssh %s read: %v", name, err)
-			return rootCause(err).Error()
-		}
-	}
-}
-
-// notifyStatus writes a progress line to the terminal through the normal
-// output path, so long steps are visible while nothing else is arriving.
-func (s *SSHClient) notifyStatus(text string) {
-	s.mu.Lock()
-	listener := s.listener
-	s.mu.Unlock()
-	if listener != nil {
-		listener.OnData([]byte("\r\n\x1b[33m" + text + "\x1b[0m\r\n"))
-	}
-}
-
-func (s *SSHClient) notifyClose(gen uint64, reason string) {
-	s.mu.Lock()
-	if gen != s.gen || s.closed {
-		s.mu.Unlock()
-		return
-	}
-	s.closed = true
-	listener := s.listener
-	s.mu.Unlock()
-	if listener != nil {
-		listener.OnClose(reason)
-	}
-}
-
-// RemoveKnownHost deletes every known_hosts entry for host:port from the store,
-// so a host trusted for a session that is being deleted does not linger. Java
-// calls this only once no session targets that host, so a shared host stays
-// trusted. Missing file or entry is not an error: the goal state is "absent".
-func RemoveKnownHost(path, host string, port int) error {
-	target := knownhosts.Normalize(net.JoinHostPort(host, strconv.Itoa(port)))
-
-	data, err := os.ReadFile(path)
-	if err != nil {
-		if os.IsNotExist(err) {
-			return nil
-		}
-		return err
-	}
-
-	var kept []string
-	changed := false
-	scanner := bufio.NewScanner(bytes.NewReader(data))
-	for scanner.Scan() {
-		line := scanner.Text()
-		if knownHostsLineMatches(line, target) {
-			changed = true
-			continue
-		}
-		kept = append(kept, line)
-	}
-	if err := scanner.Err(); err != nil {
-		return err
-	}
-	if !changed {
-		return nil
-	}
-
-	out := strings.Join(kept, "\n")
-	if len(kept) > 0 {
-		out += "\n"
-	}
-	return os.WriteFile(path, []byte(out), 0o600)
-}
-
-func closeQuiet(c io.Closer, label string) {
-	if c == nil {
-		return
-	}
-	if err := c.Close(); err != nil && !errors.Is(err, io.EOF) {
-		log.Debugf("ssh: close %s: %v", label, err)
-	}
-}
-
-func detectServerType(host string, port int) detection.ServerType {
-	ctx, cancel := context.WithTimeout(context.Background(), sshDetectionTimeout)
-	defer cancel()
-
-	dialer := &net.Dialer{}
-	serverType, err := detection.DetectSSHServerType(ctx, dialer, host, port)
-	if err != nil {
-		log.Debugf("ssh: server detection failed: %v (assuming regular SSH)", err)
-		return detection.ServerTypeRegular
-	}
-	return serverType
-}
-
-// rootCause returns the innermost error of a %w chain, so the terminal shows
-// "i/o timeout" rather than every layer that added context on the way up.
-func rootCause(err error) error {
-	for {
-		// A joined error has no single root, so keep it as-is.
-		if _, ok := err.(interface{ Unwrap() []error }); ok {
-			return err
-		}
-		next := errors.Unwrap(err)
-		if next == nil {
-			return err
-		}
-		err = next
-	}
-}
-
-// ensureFileExists creates an empty known-hosts file when none exists yet, so
-// knownhosts.New has something to parse on the first connection to any host.
-func ensureFileExists(path string) error {
-	f, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY, 0o600)
-	if err != nil {
-		return err
-	}
-	return f.Close()
-}
-
-// appendKnownHost adds the confirmed key to the store in the standard
-// known_hosts format, so it verifies silently on later connections and can be
-// inspected or edited like any OpenSSH known_hosts file.
-func appendKnownHost(path, hostname string, remote net.Addr, key gossh.PublicKey) error {
-	addresses := []string{knownhosts.Normalize(hostname)}
-	if remote != nil {
-		if normalized := knownhosts.Normalize(remote.String()); normalized != addresses[0] {
-			addresses = append(addresses, normalized)
-		}
-	}
-	line := knownhosts.Line(addresses, key)
-
-	f, err := os.OpenFile(path, os.O_APPEND|os.O_WRONLY, 0o600)
-	if err != nil {
-		return err
-	}
-	defer func() {
-		if cerr := f.Close(); cerr != nil {
-			log.Debugf("ssh: close known-hosts after append: %v", cerr)
-		}
-	}()
-	_, err = f.WriteString(line + "\n")
-	return err
-}
-
-// knownHostsLineMatches reports whether a known_hosts line's address list
-// contains the normalized target. Comment and blank lines never match.
-func knownHostsLineMatches(line, target string) bool {
-	trimmed := strings.TrimSpace(line)
-	if trimmed == "" || strings.HasPrefix(trimmed, "#") {
-		return false
-	}
-	fields := strings.Fields(trimmed)
-	if len(fields) == 0 {
-		return false
-	}
-	for _, addr := range strings.Split(fields[0], ",") {
-		if addr == target {
-			return true
-		}
-	}
-	return false
-}
-
-// isAuthFailure distinguishes credential rejection from dial, timeout and
-// host-key errors, which retrying with a password would not fix.
-func isAuthFailure(err error) bool {
-	if errors.Is(err, errPasswordRequired) {
-		return true
-	}
-	var partial *gossh.PartialSuccessError
-	if errors.As(err, &partial) {
-		return true
-	}
-	return strings.Contains(err.Error(), "unable to authenticate")
-}
-
-// passwordCouldHelp reports whether prompting for a password again can change
-// the outcome. gossh lists a method under "attempted methods" only when the
-// server offered it, so a supplied password that was never attempted means the
-// server does not accept passwords and the real error should surface instead.
-func passwordCouldHelp(err error, passwordOffered bool) bool {
-	if !passwordOffered {
-		return true
-	}
-	msg := err.Error()
-	return strings.Contains(msg, "password") || strings.Contains(msg, "keyboard-interactive")
-}

client/firewall/iptables/acl_linux.go

@@ -42,6 +42,7 @@ type aclManager struct {
 	optionalEntries map[string][]entry
 	ipsetStore      *ipsetStore
 	v6              bool
+	ipsetSupported  bool
 
 	stateManager *statemanager.Manager
 }
@@ -60,6 +61,8 @@ func newAclManager(iptablesClient *iptables.IPTables, wgIface iFaceMapper) (*acl
 func (m *aclManager) init(stateManager *statemanager.Manager) error {
 	m.stateManager = stateManager
 
+	m.ipsetSupported = m.probeIPSetSupport()
+
 	m.seedInitialEntries()
 	m.seedInitialOptionalEntries()
 
@@ -91,6 +94,12 @@ func (m *aclManager) AddPeerFiltering(
 	if m.v6 && ipsetName != "" {
 		ipsetName += "-v6"
 	}
+	// When the kernel lacks the required ipset hash module, fall back to
+	// per-IP iptables rules (pre-0.68 behavior) so ACLs keep working instead
+	// of silently leaving the chain empty.
+	if ipsetName != "" && !m.ipsetSupported {
+		ipsetName = ""
+	}
 	proto := protoForFamily(protocol, m.v6)
 	specs := filterRuleSpecs(ip, proto, sPort, dPort, action, ipsetName)
 
@@ -498,6 +507,40 @@ func transformIPsetName(ipsetName string, sPort, dPort *firewall.Port, action fi
 	}
 }
 
+// probeIPSetSupport checks whether the kernel can create the ipset type used for
+// ACL rules. On kernels lacking the required ipset hash module, ipset creation
+// fails (e.g. "invalid argument"), which would otherwise leave the ACL chain
+// empty and silently drop all policy-permitted inbound traffic. When unsupported,
+// the manager falls back to per-IP iptables rules.
+func (m *aclManager) probeIPSetSupport() bool {
+	// Use a unique name so concurrent processes don't collide and we only ever
+	// destroy the set we created ourselves. ipset names are limited to 31 chars,
+	// so use a short random suffix.
+	probeName := "nb-probe-" + uuid.New().String()[:8]
+
+	opts := ipset.CreateOptions{
+		Replace: true,
+	}
+	if m.v6 {
+		opts.Family = ipset.FamilyIPV6
+	}
+
+	if err := ipset.Create(probeName, ipset.TypeHashNet, opts); err != nil {
+		log.Warnf("ipset is not available (failed to create probe set: %v); "+
+			"falling back to per-IP iptables ACL rules. Ensure the kernel provides "+
+			"the ipset hash:net module (ip_set_hash_net) for better performance with large rule sets", err)
+		return false
+	}
+
+	defer func() {
+		if err := ipset.Destroy(probeName); err != nil {
+			log.Debugf("destroy ipset probe set %q: %v", probeName, err)
+		}
+	}()
+
+	return true
+}
+
 func (m *aclManager) createIPSet(name string) error {
 	opts := ipset.CreateOptions{
 		Replace: true,

client/firewall/iptables/manager_linux_test.go

@@ -291,3 +291,40 @@ func TestIptablesCreatePerformance(t *testing.T) {
 		})
 	}
 }
+
+// TestIptablesACLIPSetFallback verifies that when the kernel lacks ipset support,
+// the ACL manager falls back to per-IP iptables rules (-s <ip>) instead of
+// silently leaving the chain empty. See discussion #6125.
+func TestIptablesACLIPSetFallback(t *testing.T) {
+	ipv4Client, err := iptables.NewWithProtocol(iptables.ProtocolIPv4)
+	require.NoError(t, err)
+
+	// Use Create()/Init() so the router-owned chains (chainRTFWDIN/OUT) are
+	// created before the ACL manager's createDefaultChains() references them.
+	manager, err := Create(ifaceMock, iface.DefaultMTU)
+	require.NoError(t, err)
+	require.NoError(t, manager.Init(nil))
+
+	aclMgr := manager.aclMgr
+	// Simulate a kernel without the ipset hash module.
+	aclMgr.ipsetSupported = false
+
+	defer func() {
+		require.NoError(t, manager.Close(nil))
+	}()
+
+	ip := netip.MustParseAddr("10.20.0.42")
+	port := &fw.Port{Values: []uint16{22}}
+
+	rules, err := aclMgr.AddPeerFiltering(nil, ip.AsSlice(), "tcp", nil, port, fw.ActionAccept, "nb0000001")
+	require.NoError(t, err, "AddPeerFiltering should succeed via fallback")
+	require.NotEmpty(t, rules)
+
+	rule := rules[0].(*Rule)
+	require.Empty(t, rule.ipsetName, "fallback rule must not reference an ipset")
+	require.Contains(t, strings.Join(rule.specs, " "), "-s 10.20.0.42", "fallback rule must match by source IP")
+	require.NotContains(t, strings.Join(rule.specs, " "), "--match-set", "fallback rule must not use ipset matching")
+
+	// The rule must actually be present in the ACL chain (not silently dropped).
+	checkRuleSpecs(t, ipv4Client, rule.chain, true, rule.specs...)
+}

client/internal/dns/host_darwin.go

@@ -267,18 +267,38 @@ func (s *systemConfigurator) getSystemDNSSettings() (SystemDNSSettings, error) {
 		return SystemDNSSettings{}, fmt.Errorf("sending the command: %w", err)
 	}
 
-	var dnsSettings SystemDNSSettings
+	dnsSettings, serverAddresses, err := parseSystemDNSSettings(b)
+	if err != nil {
+		return dnsSettings, err
+	}
+
+	s.mu.Lock()
+	s.origNameservers = serverAddresses
+	s.mu.Unlock()
+
+	return dnsSettings, nil
+}
+
+// parseSystemDNSSettings parses the output of `scutil show State:/Network/Service/<id>/DNS`.
+// Lines that don't match the expected "index : value" shape are skipped: hosts with unusual
+// network services (e.g. orphaned hardware ports) can produce entries without a value.
+func parseSystemDNSSettings(out []byte) (SystemDNSSettings, []netip.Addr, error) {
+	// port is not exposed by scutil, default to 53
+	dnsSettings := SystemDNSSettings{ServerPort: DefaultPort}
 	var serverAddresses []netip.Addr
 	inSearchDomainsArray := false
 	inServerAddressesArray := false
 
-	scanner := bufio.NewScanner(bytes.NewReader(b))
+	scanner := bufio.NewScanner(bytes.NewReader(out))
 	for scanner.Scan() {
 		line := strings.TrimSpace(scanner.Text())
 		switch {
 		case strings.HasPrefix(line, "DomainName :"):
-			domainName := strings.TrimSpace(strings.Split(line, ":")[1])
-			dnsSettings.Domains = append(dnsSettings.Domains, domainName)
+			domainName := strings.TrimSpace(strings.TrimPrefix(line, "DomainName :"))
+			if domainName != "" {
+				dnsSettings.Domains = append(dnsSettings.Domains, domainName)
+			}
+			continue
 		case line == "SearchDomains : <array> {":
 			inSearchDomainsArray = true
 			continue
@@ -288,36 +308,45 @@ func (s *systemConfigurator) getSystemDNSSettings() (SystemDNSSettings, error) {
 		case line == "}":
 			inSearchDomainsArray = false
 			inServerAddressesArray = false
+			continue
+		}
+
+		if !inSearchDomainsArray && !inServerAddressesArray {
+			continue
+		}
+
+		parts := strings.SplitN(line, " : ", 2)
+		if len(parts) != 2 {
+			log.Debugf("skipping unexpected scutil DNS line %q", line)
+			continue
+		}
+		value := strings.TrimSpace(parts[1])
+		if value == "" {
+			continue
 		}
 
 		if inSearchDomainsArray {
-			searchDomain := strings.Split(line, " : ")[1]
-			dnsSettings.Domains = append(dnsSettings.Domains, searchDomain)
-		} else if inServerAddressesArray {
-			address := strings.Split(line, " : ")[1]
-			if ip, err := netip.ParseAddr(address); err == nil && !ip.IsUnspecified() {
-				ip = ip.Unmap()
-				serverAddresses = append(serverAddresses, ip)
-				// Prefer the first IPv4 server as ServerIP since our DNS listener is IPv4.
-				if !dnsSettings.ServerIP.IsValid() && ip.Is4() {
-					dnsSettings.ServerIP = ip
-				}
-			}
+			dnsSettings.Domains = append(dnsSettings.Domains, value)
+			continue
+		}
+
+		ip, err := netip.ParseAddr(value)
+		if err != nil || ip.IsUnspecified() {
+			continue
+		}
+		ip = ip.Unmap()
+		serverAddresses = append(serverAddresses, ip)
+		// Prefer the first IPv4 server as ServerIP since our DNS listener is IPv4.
+		if !dnsSettings.ServerIP.IsValid() && ip.Is4() {
+			dnsSettings.ServerIP = ip
 		}
 	}
 
 	if err := scanner.Err(); err != nil {
-		return dnsSettings, err
+		return dnsSettings, serverAddresses, err
 	}
 
-	// default to 53 port
-	dnsSettings.ServerPort = DefaultPort
-
-	s.mu.Lock()
-	s.origNameservers = serverAddresses
-	s.mu.Unlock()
-
-	return dnsSettings, nil
+	return dnsSettings, serverAddresses, nil
 }
 
 func (s *systemConfigurator) getOriginalNameservers() []netip.Addr {
@@ -435,11 +464,15 @@ func (s *systemConfigurator) getPrimaryService() (string, string, error) {
 	router := ""
 	for scanner.Scan() {
 		text := scanner.Text()
+		parts := strings.SplitN(text, ":", 2)
+		if len(parts) != 2 {
+			continue
+		}
 		if strings.Contains(text, "PrimaryService") {
-			primaryService = strings.TrimSpace(strings.Split(text, ":")[1])
+			primaryService = strings.TrimSpace(parts[1])
 		}
 		if strings.Contains(text, "Router") {
-			router = strings.TrimSpace(strings.Split(text, ":")[1])
+			router = strings.TrimSpace(parts[1])
 		}
 	}
 	if err := scanner.Err(); err != nil && err != io.EOF {

client/internal/dns/host_darwin_test.go

@@ -328,6 +328,120 @@ func removeTestDNSKey(key string) error {
 	return err
 }
 
+func TestParseSystemDNSSettings(t *testing.T) {
+	tests := []struct {
+		name            string
+		output          string
+		expectedDomains []string
+		expectedServers []netip.Addr
+		expectedIP      netip.Addr
+	}{
+		{
+			name: "well_formed",
+			output: `<dictionary> {
+  DomainName : example.com
+  SearchDomains : <array> {
+    0 : example.com
+    1 : corp.example.com
+  }
+  ServerAddresses : <array> {
+    0 : 192.168.1.1
+    1 : fd00::53
+  }
+}
+`,
+			expectedDomains: []string{"example.com", "example.com", "corp.example.com"},
+			expectedServers: []netip.Addr{netip.MustParseAddr("192.168.1.1"), netip.MustParseAddr("fd00::53")},
+			expectedIP:      netip.MustParseAddr("192.168.1.1"),
+		},
+		{
+			// entries without a value after the separator used to panic with
+			// "index out of range [1] with length 1"
+			name: "malformed_array_entries_skipped",
+			output: `<dictionary> {
+  SearchDomains : <array> {
+    0 :
+    (null)
+
+    1 : corp.example.com
+  }
+  ServerAddresses : <array> {
+    0 :
+    1 : 192.168.1.1
+  }
+}
+`,
+			expectedDomains: []string{"corp.example.com"},
+			expectedServers: []netip.Addr{netip.MustParseAddr("192.168.1.1")},
+			expectedIP:      netip.MustParseAddr("192.168.1.1"),
+		},
+		{
+			name: "domain_name_without_value_skipped",
+			output: `<dictionary> {
+  DomainName :
+  ServerAddresses : <array> {
+    0 : 192.168.1.1
+  }
+}
+`,
+			expectedServers: []netip.Addr{netip.MustParseAddr("192.168.1.1")},
+			expectedIP:      netip.MustParseAddr("192.168.1.1"),
+		},
+		{
+			name: "ipv6_first_prefers_ipv4_server_ip",
+			output: `<dictionary> {
+  ServerAddresses : <array> {
+    0 : fd00::53
+    1 : 192.168.1.1
+  }
+}
+`,
+			expectedServers: []netip.Addr{netip.MustParseAddr("fd00::53"), netip.MustParseAddr("192.168.1.1")},
+			expectedIP:      netip.MustParseAddr("192.168.1.1"),
+		},
+		{
+			name: "invalid_and_unspecified_addresses_skipped",
+			output: `<dictionary> {
+  ServerAddresses : <array> {
+    0 : (null)
+    1 : 0.0.0.0
+    2 : 192.168.1.1
+  }
+}
+`,
+			expectedServers: []netip.Addr{netip.MustParseAddr("192.168.1.1")},
+			expectedIP:      netip.MustParseAddr("192.168.1.1"),
+		},
+		{
+			name: "v4_mapped_address_unmapped",
+			output: `<dictionary> {
+  ServerAddresses : <array> {
+    0 : ::ffff:192.168.1.1
+  }
+}
+`,
+			expectedServers: []netip.Addr{netip.MustParseAddr("192.168.1.1")},
+			expectedIP:      netip.MustParseAddr("192.168.1.1"),
+		},
+		{
+			name:   "empty_output",
+			output: "",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			settings, servers, err := parseSystemDNSSettings([]byte(tc.output))
+			require.NoError(t, err, "parsing should not fail")
+
+			assert.Equal(t, tc.expectedDomains, settings.Domains, "domains should match")
+			assert.Equal(t, tc.expectedServers, servers, "server addresses should match")
+			assert.Equal(t, tc.expectedIP, settings.ServerIP, "server IP should match")
+			assert.Equal(t, DefaultPort, settings.ServerPort, "server port should default to 53")
+		})
+	}
+}
+
 func TestGetOriginalNameservers(t *testing.T) {
 	configurator := &systemConfigurator{
 		createdKeys: make(map[string]struct{}),