Merge branch 'rdp-ssh' into dev

2026-07-20 06:31:29 +02:00 · 2026-05-28 15:40:22 -07:00
parent e5e72ba615 5d84fa9141
commit 57575490e1
19 changed files with 1877 additions and 51 deletions
--- a/authdaemon/connection.go
+++ b/authdaemon/connection.go
@@ -19,7 +19,7 @@ func (s *Server) ProcessConnection(req ConnectionRequest) {
 	if err := ensureUser(req.Username, req.Metadata, s.cfg.GenerateRandomPassword); err != nil {
 		logger.Warn("auth-daemon: ensure user: %v", err)
 	}
-	if cfg.PrincipalsFilePath != "" {
+	if cfg.PrincipalsFilePath != "" && req.NiceId != "" {
 		if err := writePrincipals(cfg.PrincipalsFilePath, req.Username, req.NiceId); err != nil {
 			logger.Warn("auth-daemon: write principals: %v", err)
 		}
--- a/authdaemon/routes.go
+++ b/authdaemon/routes.go
@@ -14,9 +14,9 @@ func (s *Server) registerRoutes() {
 // ConnectionMetadata is the metadata object in POST /connection.
 type ConnectionMetadata struct {
 	SudoMode     string   `json:"sudoMode"`     // "none" | "full" | "commands"
-	SudoCommands []string `json:"sudoCommands"`  // used when sudoMode is "commands"
+	SudoCommands []string `json:"sudoCommands"` // used when sudoMode is "commands"
 	Homedir      bool     `json:"homedir"`
-	Groups       []string `json:"groups"`        // system groups to add the user to
+	Groups       []string `json:"groups"` // system groups to add the user to
 }

 // ConnectionRequest is the JSON body for POST /connection.
--- a/browsergateway/browsergateway.go
+++ b/browsergateway/browsergateway.go
@@ -0,0 +1,121 @@
+package browsergateway
+
+import (
+	"crypto/subtle"
+	"errors"
+	"net"
+	"net/http"
+	"strings"
+	"sync"
+)
+
+// Forwarding buffer size. RDP graphics traffic is bursty and TLS records cap
+// at ~16 KiB, so 64 KiB lets a couple of records pile up per syscall/frame
+// without wasting memory per session.
+const forwardBufSize = 64 * 1024
+
+// ListenPort is the port the browser gateway HTTP server listens on inside the
+// WireGuard netstack. This is a fixed value shared between newt and pangolin.
+// Targets do not overlap with this port because they start at 40000.
+const ListenPort = 39999
+
+// Target represents an allowed proxy destination for the browser gateway.
+// Only connections whose (Type, Destination, DestinationPort, AuthToken) match a
+// registered Target will be forwarded; all others are rejected.
+type Target struct {
+	ID              int
+	Type            string // "rdp" | "ssh" | "vnc"
+	Destination     string
+	DestinationPort int
+	AuthToken       string // per-target secret; must match the token supplied by the client
+}
+
+// Config holds the configuration for a Gateway.
+type Config struct {
+	// AuthToken is used only for NativeSSH mode (which has no external target
+	// to match against). For all proxy targets (RDP/SSH/VNC), auth tokens are
+	// stored per-Target and validated by isAllowed.
+	AuthToken string
+}
+
+// Gateway is a browser-based RDP/SSH/VNC WebSocket proxy.
+// Create one with New and mount it via RegisterHandlers or the individual
+// HandleRDP / HandleSSH / HandleVNC http.HandlerFunc methods.
+type Gateway struct {
+	authToken string
+
+	mu      sync.RWMutex
+	targets map[int]Target // keyed by Target.ID
+
+	server *http.Server
+}
+
+// New creates a new Gateway from the provided Config.
+func New(cfg Config) *Gateway {
+	return &Gateway{
+		authToken: cfg.AuthToken,
+		targets:   make(map[int]Target),
+	}
+}
+
+// SetTargets replaces the entire allowed-destination list atomically.
+func (g *Gateway) SetTargets(targets []Target) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.targets = make(map[int]Target, len(targets))
+	for _, t := range targets {
+		g.targets[t.ID] = t
+	}
+}
+
+// AddTarget adds or updates a single allowed destination.
+func (g *Gateway) AddTarget(t Target) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.targets[t.ID] = t
+}
+
+// RemoveTarget removes an allowed destination by its ID.
+func (g *Gateway) RemoveTarget(id int) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	delete(g.targets, id)
+}
+
+// isAllowed reports whether a connection to (targetType, host, port) with the
+// given authToken is permitted. The token is compared against the per-target
+// AuthToken using constant-time comparison to prevent timing attacks.
+func (g *Gateway) isAllowed(targetType, host string, port int, authToken string) bool {
+	g.mu.RLock()
+	defer g.mu.RUnlock()
+	for _, t := range g.targets {
+		if t.Type == targetType && t.Destination == host && t.DestinationPort == port {
+			return subtle.ConstantTimeCompare([]byte(authToken), []byte(t.AuthToken)) == 1
+		}
+	}
+	return false
+}
+
+// Start serves the browser gateway HTTP server on the provided listener.
+// It returns nil when the listener is closed (normal shutdown).
+func (g *Gateway) Start(ln net.Listener) error {
+	mux := http.NewServeMux()
+	g.RegisterHandlers(mux)
+	g.server = &http.Server{Handler: mux}
+	err := g.server.Serve(ln)
+	if err == nil ||
+		errors.Is(err, net.ErrClosed) ||
+		errors.Is(err, http.ErrServerClosed) ||
+		strings.Contains(err.Error(), "use of closed") ||
+		strings.Contains(err.Error(), "invalid state") {
+		return nil
+	}
+	return err
+}
+
+// RegisterHandlers registers the /rdp, /ssh, and /vnc routes on mux.
+func (g *Gateway) RegisterHandlers(mux *http.ServeMux) {
+	mux.HandleFunc("/gateway/rdp", g.HandleRDP)
+	mux.HandleFunc("/gateway/ssh", g.HandleSSH)
+	mux.HandleFunc("/gateway/vnc", g.handleVNC)
+}
--- a/browsergateway/rdcleanpath.go
+++ b/browsergateway/rdcleanpath.go
@@ -0,0 +1,88 @@
+package browsergateway
+
+import (
+	"encoding/asn1"
+	"fmt"
+)
+
+// RDCleanPath PDU version (BASE_VERSION + 1 = 3389 + 1).
+const rdCleanPathVersion = int64(3390)
+
+// rdCleanPathPdu is a Go translation of the ASN.1 SEQUENCE defined in the
+// ironrdp-rdcleanpath crate. All optional fields use EXPLICIT context-specific
+// tagging, matching the Rust `der::Sequence` derivation with
+// `tag_mode = "EXPLICIT"`.
+//
+// We only need a subset of fields for the basic proxy flow, but the struct
+// declares every tag we may encounter so that decoding does not fail on an
+// unexpected element.
+type rdCleanPathPdu struct {
+	Version           int64    `asn1:"explicit,tag:0"`
+	Destination       string   `asn1:"explicit,tag:2,optional,utf8"`
+	ProxyAuth         string   `asn1:"explicit,tag:3,optional,utf8"`
+	ServerAuth        string   `asn1:"explicit,tag:4,optional,utf8"`
+	PreconnectionBlob string   `asn1:"explicit,tag:5,optional,utf8"`
+	X224              []byte   `asn1:"explicit,tag:6,optional"`
+	ServerCertChain   [][]byte `asn1:"explicit,tag:7,optional"`
+	ServerAddr        string   `asn1:"explicit,tag:9,optional,utf8"`
+}
+
+// decodeRDCleanPathRequest parses a client-to-proxy RDCleanPath PDU.
+func decodeRDCleanPathRequest(buf []byte) (*rdCleanPathPdu, error) {
+	var pdu rdCleanPathPdu
+	rest, err := asn1.Unmarshal(buf, &pdu)
+	if err != nil {
+		return nil, fmt.Errorf("asn1 unmarshal: %w", err)
+	}
+	if len(rest) != 0 {
+		return nil, fmt.Errorf("trailing data after RDCleanPath PDU: %d bytes", len(rest))
+	}
+	if pdu.Version != rdCleanPathVersion {
+		return nil, fmt.Errorf("unexpected RDCleanPath version: %d", pdu.Version)
+	}
+	return &pdu, nil
+}
+
+// encodeRDCleanPathResponse builds a proxy-to-client RDCleanPath response PDU
+// containing the server address, X.224 connection confirm and server TLS chain.
+func encodeRDCleanPathResponse(serverAddr string, x224Rsp []byte, certChain [][]byte) ([]byte, error) {
+	pdu := rdCleanPathPdu{
+		Version:         rdCleanPathVersion,
+		X224:            x224Rsp,
+		ServerCertChain: certChain,
+		ServerAddr:      serverAddr,
+	}
+	return asn1.Marshal(pdu)
+}
+
+// detectRDCleanPathLength returns the total DER length of an RDCleanPath PDU
+// if enough bytes are available, otherwise -1.
+//
+// The PDU is a DER SEQUENCE, which begins with the universal SEQUENCE tag
+// (0x30) followed by a length octet/octets. We parse just enough to know the
+// total length so we can buffer accordingly.
+func detectRDCleanPathLength(buf []byte) int {
+	if len(buf) < 2 {
+		return -1
+	}
+	if buf[0] != 0x30 {
+		// Not a SEQUENCE: cannot be RDCleanPath.
+		return -2
+	}
+	l := buf[1]
+	if l < 0x80 {
+		return 2 + int(l)
+	}
+	n := int(l & 0x7f)
+	if n == 0 || n > 4 {
+		return -2
+	}
+	if len(buf) < 2+n {
+		return -1
+	}
+	total := 0
+	for i := 0; i < n; i++ {
+		total = (total << 8) | int(buf[2+i])
+	}
+	return 2 + n + total
+}
--- a/browsergateway/rdp.go
+++ b/browsergateway/rdp.go
@@ -0,0 +1,271 @@
+package browsergateway
+
+import (
+	"context"
+	"crypto/tls"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/coder/websocket"
+)
+
+// HandleRDP is an http.HandlerFunc for RDP-over-WebSocket connections.
+func (g *Gateway) HandleRDP(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+	ws, err := websocket.Accept(w, r, &websocket.AcceptOptions{
+		InsecureSkipVerify: true, // any-origin: minimal dev proxy with no auth
+		Subprotocols:       []string{"binary"},
+	})
+	if err != nil {
+		log.Printf("websocket upgrade failed: %v", err)
+		return
+	}
+	// Disable per-message read size cap (default is 32 KiB which would break
+	// large RDP graphics messages).
+	ws.SetReadLimit(-1)
+	defer ws.CloseNow() //nolint:errcheck
+
+	if err := g.serveSession(ctx, ws); err != nil {
+		log.Printf("session error: %v", err)
+	}
+}
+
+func (g *Gateway) serveSession(ctx context.Context, ws *websocket.Conn) error {
+	// Expose the WebSocket as a streaming net.Conn. Binary messages are
+	// concatenated into a byte stream and writes become single binary frames.
+	// This is a thin wrapper with no per-message goroutine, unlike Gorilla.
+	stream := websocket.NetConn(ctx, ws, websocket.MessageBinary)
+	defer stream.Close() //nolint:errcheck
+
+	// -- Read the initial RDCleanPath request from the client --
+	pdu, err := readCleanPath(stream)
+	if err != nil {
+		return fmt.Errorf("read RDCleanPath: %w", err)
+	}
+
+	if pdu.Destination == "" {
+		return errors.New("RDCleanPath missing destination")
+	}
+	if len(pdu.X224) == 0 {
+		return errors.New("RDCleanPath missing X224 connection PDU")
+	}
+
+	target := pdu.Destination
+	// Default port for RDP if not specified.
+	if _, _, splitErr := net.SplitHostPort(target); splitErr != nil {
+		target = net.JoinHostPort(target, "3389")
+	}
+
+	// Validate destination against the registered target allowlist,
+	// including per-target auth token.
+	rdpHost, rdpPortStr, _ := net.SplitHostPort(target)
+	rdpPort, _ := strconv.Atoi(rdpPortStr)
+	if !g.isAllowed("rdp", rdpHost, rdpPort, pdu.ProxyAuth) {
+		return fmt.Errorf("RDP destination %s is not in the allowed target list or auth token mismatch", target)
+	}
+
+	log.Printf("Connecting to RDP server %s", target)
+
+	// -- Open TCP connection to the destination RDP server --
+	serverTCP, err := net.DialTimeout("tcp", target, 15*time.Second)
+	if err != nil {
+		return fmt.Errorf("dial %s: %w", target, err)
+	}
+	defer serverTCP.Close()
+	if tcp, ok := serverTCP.(*net.TCPConn); ok {
+		// NoDelay is Go's default; set explicitly. RDP wants low latency for
+		// input echo, and the bulk path is naturally chunked by TLS records.
+		_ = tcp.SetNoDelay(true)
+		_ = tcp.SetKeepAlive(true)
+		_ = tcp.SetKeepAlivePeriod(30 * time.Second)
+		_ = tcp.SetReadBuffer(forwardBufSize)
+		_ = tcp.SetWriteBuffer(forwardBufSize)
+	}
+	serverAddr := serverTCP.RemoteAddr().String()
+
+	// Forward the optional pre-connection blob, then the X.224 connection request.
+	if pdu.PreconnectionBlob != "" {
+		if _, err := serverTCP.Write([]byte(pdu.PreconnectionBlob)); err != nil {
+			return fmt.Errorf("send PCB: %w", err)
+		}
+	}
+	if _, err := serverTCP.Write(pdu.X224); err != nil {
+		return fmt.Errorf("send X224: %w", err)
+	}
+
+	// -- Read the X.224 connection confirm from the server --
+	x224Rsp, err := readX224(serverTCP)
+	if err != nil {
+		return fmt.Errorf("read X224 response: %w", err)
+	}
+	logX224Negotiation(x224Rsp)
+
+	// -- Upgrade the server connection to TLS (skip verification) --
+	//
+	// Windows RDP hosts are picky: only set SNI when the target is a hostname
+	// (Go would skip SNI for IP literals anyway, but be explicit), and accept
+	// the full range of TLS versions / ciphers since some servers only
+	// negotiate TLS 1.0 or legacy suites.
+	host, _, _ := net.SplitHostPort(target)
+	tlsCfg := &tls.Config{
+		InsecureSkipVerify: true, //nolint:gosec // proxy intentionally skips verification
+		MinVersion:         tls.VersionTLS10,
+		// Cap at TLS 1.2: Windows RDP servers commonly send a TLS "internal_error"
+		// alert when CredSSP/NLA is layered on top of a TLS 1.3 session.
+		MaxVersion: tls.VersionTLS12,
+	}
+	if net.ParseIP(host) == nil {
+		tlsCfg.ServerName = host
+	}
+	tlsConn := tls.Client(serverTCP, tlsCfg)
+	if err := tlsConn.Handshake(); err != nil {
+		return fmt.Errorf("TLS handshake with server: %w", err)
+	}
+	log.Printf("Server TLS handshake OK (version=0x%04x cipher=0x%04x)",
+		tlsConn.ConnectionState().Version, tlsConn.ConnectionState().CipherSuite)
+
+	// Collect the raw DER server certificate chain to return to the client.
+	state := tlsConn.ConnectionState()
+	if len(state.PeerCertificates) == 0 {
+		return errors.New("server did not present any certificates")
+	}
+	chain := make([][]byte, 0, len(state.PeerCertificates))
+	for _, c := range state.PeerCertificates {
+		chain = append(chain, c.Raw)
+	}
+
+	// -- Send the RDCleanPath response back to the client --
+	rsp, err := encodeRDCleanPathResponse(serverAddr, x224Rsp, chain)
+	if err != nil {
+		return fmt.Errorf("encode RDCleanPath response: %w", err)
+	}
+	if _, err := stream.Write(rsp); err != nil {
+		return fmt.Errorf("write RDCleanPath response: %w", err)
+	}
+
+	log.Printf("RDCleanPath handshake complete, forwarding traffic to %s", serverAddr)
+
+	// -- Two-way blind forwarding of the (now TLS-encrypted) RDP stream --
+	return forward(stream, tlsConn)
+}
+
+// readCleanPath buffers bytes from the stream until a full RDCleanPath PDU has
+// been received, then decodes it.
+func readCleanPath(r io.Reader) (*rdCleanPathPdu, error) {
+	buf := make([]byte, 0, 1024)
+	tmp := make([]byte, 1024)
+	for {
+		total := detectRDCleanPathLength(buf)
+		switch {
+		case total == -2:
+			return nil, errors.New("invalid RDCleanPath PDU")
+		case total > 0 && len(buf) >= total:
+			return decodeRDCleanPathRequest(buf[:total])
+		}
+		n, err := r.Read(tmp)
+		if n > 0 {
+			buf = append(buf, tmp[:n]...)
+		}
+		if err != nil {
+			return nil, err
+		}
+	}
+}
+
+// readX224 reads exactly one TPKT-framed X.224 PDU from the server.
+//
+// The TPKT header is 4 bytes: version (0x03), reserved (0x00), and a u16
+// big-endian total length that includes the header itself.
+func readX224(r io.Reader) ([]byte, error) {
+	hdr := make([]byte, 4)
+	if _, err := io.ReadFull(r, hdr); err != nil {
+		return nil, err
+	}
+	if hdr[0] != 0x03 {
+		return nil, fmt.Errorf("unexpected TPKT version 0x%02x", hdr[0])
+	}
+	total := int(binary.BigEndian.Uint16(hdr[2:4]))
+	if total < 4 || total > 4096 {
+		return nil, fmt.Errorf("unreasonable TPKT length %d", total)
+	}
+	out := make([]byte, total)
+	copy(out, hdr)
+	if _, err := io.ReadFull(r, out[4:]); err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+// logX224Negotiation prints which RDP security protocol the server selected
+// (or the failure code), to help diagnose handshake issues such as the server
+// requiring NLA/CredSSP.
+//
+// X.224 Connection Confirm layout (RFC 1006 / [MS-RDPBCGR]):
+//
+//	bytes 0..3   TPKT header (03 00 LL LL)
+//	byte  4      X.224 length indicator
+//	byte  5      X.224 code (0xD0 = CC)
+//	bytes 6..10  DST-REF, SRC-REF, class
+//	byte  11     optional RDP Negotiation type (0x02 = response, 0x03 = failure)
+//	byte  12     flags
+//	bytes 13..14 length (little-endian, =8)
+//	bytes 15..18 selected protocol / failure code (u32 little-endian)
+func logX224Negotiation(pdu []byte) {
+	if len(pdu) < 19 {
+		log.Printf("X.224 response too short (%d bytes) to contain RDP negotiation", len(pdu))
+		return
+	}
+	switch pdu[11] {
+	case 0x02:
+		proto := uint32(pdu[15]) | uint32(pdu[16])<<8 | uint32(pdu[17])<<16 | uint32(pdu[18])<<24
+		name := "unknown"
+		switch proto {
+		case 0:
+			name = "RDP (standard)"
+		case 1:
+			name = "SSL/TLS"
+		case 2:
+			name = "HYBRID (CredSSP/NLA)"
+		case 8:
+			name = "HYBRID_EX"
+		}
+		log.Printf("Server selected RDP protocol 0x%x (%s)", proto, name)
+	case 0x03:
+		code := uint32(pdu[15]) | uint32(pdu[16])<<8 | uint32(pdu[17])<<16 | uint32(pdu[18])<<24
+		log.Printf("Server returned RDP negotiation failure code 0x%x", code)
+	default:
+		log.Printf("X.224 response has no RDP negotiation block (type=0x%02x)", pdu[11])
+	}
+}
+
+// forward shuttles bytes between the two streams until either side closes.
+func forward(a, b io.ReadWriteCloser) error {
+	errc := make(chan error, 2)
+	go func() {
+		buf := make([]byte, forwardBufSize)
+		_, err := io.CopyBuffer(a, b, buf)
+		_ = a.Close()
+		_ = b.Close()
+		errc <- err
+	}()
+	go func() {
+		buf := make([]byte, forwardBufSize)
+		_, err := io.CopyBuffer(b, a, buf)
+		_ = a.Close()
+		_ = b.Close()
+		errc <- err
+	}()
+	// Wait for one side to finish, then return.
+	err := <-errc
+	if errors.Is(err, io.EOF) || err == nil {
+		return nil
+	}
+	return err
+}
--- a/browsergateway/ssh.go
+++ b/browsergateway/ssh.go
@@ -0,0 +1,255 @@
+package browsergateway
+
+import (
+	"context"
+	"crypto/subtle"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net"
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/coder/websocket"
+	"golang.org/x/crypto/ssh"
+)
+
+// sshClientMsg is a JSON message sent from the browser to the proxy.
+type sshClientMsg struct {
+	// type: "auth" | "data" | "resize"
+	Type       string `json:"type"`
+	Password   string `json:"password,omitempty"`   // used when type="auth"
+	PrivateKey string `json:"privateKey,omitempty"` // used when type="auth"
+	Data       string `json:"data,omitempty"`       // used when type="data"
+	Cols       uint32 `json:"cols,omitempty"`       // used when type="resize"
+	Rows       uint32 `json:"rows,omitempty"`       // used when type="resize"
+}
+
+// sshServerMsg is a JSON message sent from the proxy back to the browser.
+type sshServerMsg struct {
+	// type: "data" | "error"
+	Type  string `json:"type"`
+	Data  string `json:"data,omitempty"`
+	Error string `json:"error,omitempty"`
+}
+
+// HandleSSH is an http.HandlerFunc for SSH-over-WebSocket connections.
+func (g *Gateway) HandleSSH(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+
+	token := r.URL.Query().Get("authToken")
+
+	var nativeSSH = false
+
+	// In proxy mode we also need host + username from query params.
+	var target, username string
+	if !nativeSSH {
+		host := r.URL.Query().Get("host")
+		port := r.URL.Query().Get("port")
+		username = r.URL.Query().Get("username")
+		if host == "" || username == "" {
+			http.Error(w, "missing host or username", http.StatusBadRequest)
+			return
+		}
+		if port == "" {
+			port = "22"
+		}
+		sshPort, _ := strconv.Atoi(port)
+		if !g.isAllowed("ssh", host, sshPort, token) {
+			http.Error(w, "destination not allowed or auth token mismatch", http.StatusForbidden)
+			return
+		}
+		target = net.JoinHostPort(host, port)
+	} else {
+		// Native SSH mode: validate the gateway token then read the target username.
+		if subtle.ConstantTimeCompare([]byte(token), []byte(g.authToken)) != 1 {
+			http.Error(w, "unauthorized", http.StatusUnauthorized)
+			return
+		}
+		username = r.URL.Query().Get("username")
+		if username == "" {
+			http.Error(w, "missing username", http.StatusBadRequest)
+			return
+		}
+	}
+
+	ws, err := websocket.Accept(w, r, &websocket.AcceptOptions{
+		InsecureSkipVerify: true,
+		Subprotocols:       []string{"ssh"},
+	})
+	if err != nil {
+		log.Printf("SSH websocket upgrade failed: %v", err)
+		return
+	}
+	ws.SetReadLimit(-1)
+	defer ws.CloseNow() //nolint:errcheck
+
+	if nativeSSH {
+		if err := serveNativeSSHSession(ctx, ws, username); err != nil {
+			log.Printf("SSH native session error: %v", err)
+		}
+	} else {
+		if err := serveSSHSession(ctx, ws, target, username, g.authToken); err != nil {
+			log.Printf("SSH session error: %v", err)
+		}
+	}
+}
+
+func serveSSHSession(ctx context.Context, ws *websocket.Conn, target, username, _ string) error {
+	// -- Wait for the auth message from the client to get the password --
+	_, authBytes, err := ws.Read(ctx)
+	if err != nil {
+		return fmt.Errorf("read auth message: %w", err)
+	}
+	var authMsg sshClientMsg
+	if err := json.Unmarshal(authBytes, &authMsg); err != nil || authMsg.Type != "auth" {
+		return fmt.Errorf("expected auth message, got: %s", authBytes)
+	}
+	password := authMsg.Password
+	privateKey := authMsg.PrivateKey
+
+	// Build the list of auth methods. Private key takes priority when provided.
+	var authMethods []ssh.AuthMethod
+	if privateKey != "" {
+		signer, err := ssh.ParsePrivateKey([]byte(privateKey))
+		if err != nil {
+			sendSSHError(ctx, ws, fmt.Sprintf("Failed to parse private key: %v", err))
+			return fmt.Errorf("parse private key: %w", err)
+		}
+		authMethods = append(authMethods, ssh.PublicKeys(signer))
+	}
+	if password != "" {
+		authMethods = append(authMethods, ssh.Password(password))
+	}
+	if len(authMethods) == 0 {
+		sendSSHError(ctx, ws, "No authentication credentials provided")
+		return fmt.Errorf("no auth credentials")
+	}
+	log.Printf("SSH: connecting to %s as %s", target, username)
+	sshCfg := &ssh.ClientConfig{
+		User: username,
+		Auth: authMethods,
+		// HostKeyCallback is intentionally InsecureIgnoreHostKey for this dev
+		// proxy. In production, verify against a known-hosts store.
+		HostKeyCallback: ssh.InsecureIgnoreHostKey(), //nolint:gosec
+		Timeout:         15 * time.Second,
+	}
+
+	sshClient, err := ssh.Dial("tcp", target, sshCfg)
+	if err != nil {
+		sendSSHError(ctx, ws, fmt.Sprintf("SSH dial failed: %v", err))
+		return fmt.Errorf("ssh dial %s: %w", target, err)
+	}
+	defer sshClient.Close()
+
+	// -- Open an interactive session --
+	sess, err := sshClient.NewSession()
+	if err != nil {
+		sendSSHError(ctx, ws, fmt.Sprintf("Failed to open SSH session: %v", err))
+		return fmt.Errorf("ssh new session: %w", err)
+	}
+	defer sess.Close()
+
+	// Request a PTY.
+	if err := sess.RequestPty("xterm-256color", 24, 80, ssh.TerminalModes{
+		ssh.ECHO:          1,
+		ssh.TTY_OP_ISPEED: 38400,
+		ssh.TTY_OP_OSPEED: 38400,
+	}); err != nil {
+		sendSSHError(ctx, ws, fmt.Sprintf("Failed to request PTY: %v", err))
+		return fmt.Errorf("ssh request pty: %w", err)
+	}
+
+	stdinPipe, err := sess.StdinPipe()
+	if err != nil {
+		return fmt.Errorf("ssh stdin pipe: %w", err)
+	}
+	stdoutPipe, err := sess.StdoutPipe()
+	if err != nil {
+		return fmt.Errorf("ssh stdout pipe: %w", err)
+	}
+	stderrPipe, err := sess.StderrPipe()
+	if err != nil {
+		return fmt.Errorf("ssh stderr pipe: %w", err)
+	}
+
+	if err := sess.Shell(); err != nil {
+		sendSSHError(ctx, ws, fmt.Sprintf("Failed to start shell: %v", err))
+		return fmt.Errorf("ssh shell: %w", err)
+	}
+
+	log.Printf("SSH: session established with %s", target)
+
+	// -- Pump SSH stdout/stderr → WebSocket --
+	sessCtx, cancelSess := context.WithCancel(ctx)
+	defer cancelSess()
+
+	go func() {
+		buf := make([]byte, 4096)
+		for {
+			n, readErr := stdoutPipe.Read(buf)
+			if n > 0 {
+				msg := sshServerMsg{Type: "data", Data: string(buf[:n])}
+				b, _ := json.Marshal(msg)
+				if writeErr := ws.Write(sessCtx, websocket.MessageText, b); writeErr != nil {
+					return
+				}
+			}
+			if readErr != nil {
+				cancelSess()
+				return
+			}
+		}
+	}()
+
+	go func() {
+		buf := make([]byte, 4096)
+		for {
+			n, readErr := stderrPipe.Read(buf)
+			if n > 0 {
+				msg := sshServerMsg{Type: "data", Data: string(buf[:n])}
+				b, _ := json.Marshal(msg)
+				if writeErr := ws.Write(sessCtx, websocket.MessageText, b); writeErr != nil {
+					return
+				}
+			}
+			if readErr != nil {
+				return
+			}
+		}
+	}()
+
+	// -- Pump WebSocket input → SSH stdin / resize --
+	for {
+		_, msgBytes, readErr := ws.Read(sessCtx)
+		if readErr != nil {
+			break
+		}
+
+		var msg sshClientMsg
+		if err := json.Unmarshal(msgBytes, &msg); err != nil {
+			continue
+		}
+
+		switch msg.Type {
+		case "data":
+			if _, err := stdinPipe.Write([]byte(msg.Data)); err != nil {
+				return fmt.Errorf("write ssh stdin: %w", err)
+			}
+		case "resize":
+			if msg.Cols > 0 && msg.Rows > 0 {
+				_ = sess.WindowChange(int(msg.Rows), int(msg.Cols))
+			}
+		}
+	}
+
+	return nil
+}
+
+// sendSSHError sends an error message to the browser and logs it.
+func sendSSHError(ctx context.Context, ws *websocket.Conn, msg string) {
+	log.Printf("SSH error: %s", msg)
+	b, _ := json.Marshal(sshServerMsg{Type: "error", Error: msg})
+	_ = ws.Write(ctx, websocket.MessageText, b)
+}
--- a/browsergateway/ssh_native.go
+++ b/browsergateway/ssh_native.go
@@ -0,0 +1,92 @@
+package browsergateway
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+
+	"github.com/coder/websocket"
+	"github.com/fosrl/newt/nativessh"
+)
+
+// serveNativeSSHSession handles a WebSocket SSH session by authenticating the
+// user against the host OS (authorized_keys then PAM password) and then
+// spawning a PTY+shell running as that user.
+//
+// The auth frame from the browser must be a JSON sshClientMsg with type="auth"
+// carrying the same password/privateKey fields used by the proxy SSH path.
+// The target username is passed in from the HTTP layer (query param).
+func serveNativeSSHSession(ctx context.Context, ws *websocket.Conn, username string) error {
+	// Read the auth frame.
+	_, authBytes, err := ws.Read(ctx)
+	if err != nil {
+		return fmt.Errorf("read auth message: %w", err)
+	}
+	var authMsg sshClientMsg
+	if err := json.Unmarshal(authBytes, &authMsg); err != nil || authMsg.Type != "auth" {
+		return fmt.Errorf("expected auth message, got: %s", authBytes)
+	}
+
+	// Authenticate using host authorized_keys or PAM password.
+	if err := nativessh.Authenticate(username, authMsg.Password, authMsg.PrivateKey); err != nil {
+		sendSSHError(ctx, ws, "Authentication failed")
+		return fmt.Errorf("auth for user %q: %w", username, err)
+	}
+
+	log.Printf("SSH native: spawning shell as user %q", username)
+
+	sess, err := nativessh.NewPTYSessionAs(username)
+	if err != nil {
+		sendSSHError(ctx, ws, fmt.Sprintf("Failed to spawn shell: %v", err))
+		return fmt.Errorf("pty session as %q: %w", username, err)
+	}
+	defer sess.Close()
+
+	// Cancel context to unblock the WebSocket read loop when the shell exits.
+	sessCtx, cancelSess := context.WithCancel(ctx)
+	defer cancelSess()
+
+	// Pump PTY output → WebSocket.
+	go func() {
+		defer cancelSess()
+		buf := make([]byte, 4096)
+		for {
+			n, readErr := sess.Read(buf)
+			if n > 0 {
+				msg := sshServerMsg{Type: "data", Data: string(buf[:n])}
+				b, _ := json.Marshal(msg)
+				if writeErr := ws.Write(sessCtx, websocket.MessageText, b); writeErr != nil {
+					return
+				}
+			}
+			if readErr != nil {
+				return
+			}
+		}
+	}()
+
+	// Pump WebSocket input → PTY stdin / resize.
+	for {
+		_, msgBytes, readErr := ws.Read(sessCtx)
+		if readErr != nil {
+			break
+		}
+		var msg sshClientMsg
+		if err := json.Unmarshal(msgBytes, &msg); err != nil {
+			continue
+		}
+		switch msg.Type {
+		case "data":
+			if _, writeErr := sess.Write([]byte(msg.Data)); writeErr != nil {
+				return fmt.Errorf("write pty: %w", writeErr)
+			}
+		case "resize":
+			if msg.Cols > 0 && msg.Rows > 0 {
+				_ = sess.Resize(uint16(msg.Cols), uint16(msg.Rows))
+			}
+		}
+	}
+
+	return nil
+}
--- a/browsergateway/vnc.go
+++ b/browsergateway/vnc.go
@@ -0,0 +1,98 @@
+package browsergateway
+
+import (
+	"context"
+	"io"
+	"log"
+	"net"
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/coder/websocket"
+)
+
+const (
+	vncDialTimeout    = 10 * time.Second
+	vncKeepAlive      = 30 * time.Second
+	vncForwardBufSize = 32 * 1024
+)
+
+// handleVNC proxies a noVNC WebSocket connection to a raw TCP VNC backend.
+// It follows the same auth-token-in-query-param pattern as handleSSH.
+//
+// Query parameters:
+//
+//	authToken – shared secret matching the -auth-token flag
+//	host      – VNC backend hostname or IP
+//	port      – VNC backend port (default: 5900)
+func (g *Gateway) handleVNC(w http.ResponseWriter, r *http.Request) {
+	host := r.URL.Query().Get("host")
+	port := r.URL.Query().Get("port")
+	if host == "" {
+		http.Error(w, "missing host", http.StatusBadRequest)
+		return
+	}
+	if port == "" {
+		port = "5900"
+	}
+	vncPort, _ := strconv.Atoi(port)
+	authToken := r.URL.Query().Get("authToken")
+	if !g.isAllowed("vnc", host, vncPort, authToken) {
+		http.Error(w, "destination not allowed or auth token mismatch", http.StatusForbidden)
+		return
+	}
+	target := net.JoinHostPort(host, port)
+
+	// Accept the WebSocket. noVNC negotiates the "binary" subprotocol;
+	// fall back gracefully when the client sends "base64" as well.
+	ws, err := websocket.Accept(w, r, &websocket.AcceptOptions{
+		InsecureSkipVerify: true,
+		Subprotocols:       []string{"binary", "base64"},
+	})
+	if err != nil {
+		log.Printf("vnc: websocket upgrade failed: %v", err)
+		return
+	}
+	ws.SetReadLimit(-1)
+	defer ws.CloseNow() //nolint:errcheck
+
+	ctx := r.Context()
+	if err := serveVNC(ctx, ws, target); err != nil {
+		log.Printf("vnc: session error (%s): %v", target, err)
+	}
+}
+
+func serveVNC(ctx context.Context, ws *websocket.Conn, target string) error {
+	// Dial the VNC backend TCP server.
+	dialer := &net.Dialer{
+		Timeout:   vncDialTimeout,
+		KeepAlive: vncKeepAlive,
+	}
+	conn, err := dialer.DialContext(ctx, "tcp", target)
+	if err != nil {
+		return err
+	}
+	defer conn.Close() //nolint:errcheck
+
+	// Expose the WebSocket as a plain net.Conn byte stream (binary frames).
+	stream := websocket.NetConn(ctx, ws, websocket.MessageBinary)
+	defer stream.Close() //nolint:errcheck
+
+	// Proxy bidirectionally: VNC backend <-> browser.
+	errc := make(chan error, 2)
+	go func() {
+		buf := make([]byte, vncForwardBufSize)
+		_, err := io.CopyBuffer(conn, stream, buf)
+		errc <- err
+	}()
+	go func() {
+		buf := make([]byte, vncForwardBufSize)
+		_, err := io.CopyBuffer(stream, conn, buf)
+		errc <- err
+	}()
+
+	// Return when either direction closes.
+	err = <-errc
+	return err
+}
--- a/clients.go
+++ b/clients.go
@@ -7,6 +7,7 @@ import (
 	wgnetstack "github.com/fosrl/newt/clients"
 	"github.com/fosrl/newt/clients/permissions"
 	"github.com/fosrl/newt/logger"
+	"github.com/fosrl/newt/nativessh"
 	"github.com/fosrl/newt/websocket"
 	"golang.zx2c4.com/wireguard/tun/netstack"
 )
@@ -14,7 +15,7 @@ import (
 var wgService *clients.WireGuardService
 var ready bool

-func setupClients(client *websocket.Client) {
+func setupClients(client *websocket.Client, credStore *nativessh.CredentialStore) {
 	var host = endpoint
 	if strings.HasPrefix(host, "http://") {
 		host = strings.TrimPrefix(host, "http://")
@@ -42,6 +43,8 @@ func setupClients(client *websocket.Client) {
 		logger.Fatal("Failed to create WireGuard service: %v", err)
 	}

+	wgService.SetCredentialStore(credStore)
+
 	client.OnTokenUpdate(func(token string) {
 		wgService.SetToken(token)
 	})
--- a/clients/clients.go
+++ b/clients/clients.go
@@ -20,6 +20,7 @@ import (
 	newtDevice "github.com/fosrl/newt/device"
 	"github.com/fosrl/newt/holepunch"
 	"github.com/fosrl/newt/logger"
+	"github.com/fosrl/newt/nativessh"
 	"github.com/fosrl/newt/netstack2"
 	"github.com/fosrl/newt/network"
 	"github.com/fosrl/newt/util"
@@ -109,6 +110,9 @@ type WireGuardService struct {
 	sharedBind         *bind.SharedBind
 	holePunchManager   *holepunch.Manager
 	useNativeInterface bool
+	// SSH server running on the clients' netstack
+	sshServer *sshServerHandle
+	credStore *nativessh.CredentialStore
 	// Direct UDP relay from main tunnel to clients' WireGuard
 	directRelayStop    chan struct{}
 	directRelayWg      sync.WaitGroup
@@ -197,6 +201,13 @@ func NewWireGuardService(interfaceName string, port uint16, mtu int, host string
 	return service, nil
 }

+// SetCredentialStore sets the in-memory SSH credential store used by the
+// native SSH server. It must be called before the netstack is configured
+// (i.e. before the first newt/wg/receive-config message is processed).
+func (s *WireGuardService) SetCredentialStore(store *nativessh.CredentialStore) {
+	s.credStore = store
+}
+
 // ReportRTT allows reporting native RTTs to telemetry, rate-limited externally.
 func (s *WireGuardService) ReportRTT(seconds float64) {
 	if s.serverPubKey == "" {
@@ -215,6 +226,12 @@ func (s *WireGuardService) Close() {
 		s.stopGetConfig = nil
 	}

+	// Stop SSH server before tearing down the netstack
+	if s.sshServer != nil {
+		s.sshServer.stop()
+		s.sshServer = nil
+	}
+
 	// Flush access logs before tearing down the tunnel
 	if s.tnet != nil {
 		if ph := s.tnet.GetProxyHandler(); ph != nil {
@@ -909,6 +926,16 @@ func (s *WireGuardService) ensureWireguardInterface(wgconfig WgConfig) error {
 		logger.Error("Failed to start WireGuard tester server: %v", err)
 	}

+	// Start the SSH server on the clients' netstack (port 22).
+	// A nil credStore means SSH is disabled (--disable-ssh), so skip starting the server.
+	if s.credStore != nil {
+		if h, sshErr := startSSHOnNetstack(s.tnet, s.credStore); sshErr != nil {
+			logger.Warn("nativessh: not starting SSH server on clients netstack: %v", sshErr)
+		} else {
+			s.sshServer = h
+		}
+	}
+
 	// Note: we already unlocked above, so don't use defer unlock

 	// Apply any pending blocked state to the newly created proxy handler
@@ -1590,3 +1617,33 @@ func (s *WireGuardService) filterReadOnlyFields(config string) string {

 	return strings.Join(filteredLines, "\n")
 }
+
+// sshServerHandle holds the listener so the SSH server can be stopped by
+// closing it.
+type sshServerHandle struct {
+	ln net.Listener
+}
+
+func (h *sshServerHandle) stop() {
+	_ = h.ln.Close()
+}
+
+// startSSHOnNetstack creates a TCP listener on port 22 of the clients' netstack
+// and starts serving SSH connections on it in the background. The returned
+// handle can be used to stop the server by closing the listener.
+func startSSHOnNetstack(tnet *netstack2.Net, creds *nativessh.CredentialStore) (*sshServerHandle, error) {
+	srv := nativessh.NewServer(nativessh.ServerConfig{
+		Credentials: creds,
+	})
+	ln, err := tnet.ListenTCP(&net.TCPAddr{Port: 22})
+	if err != nil {
+		return nil, fmt.Errorf("listen on netstack port 22: %w", err)
+	}
+	h := &sshServerHandle{ln: ln}
+	go func() {
+		if err := srv.Serve(ln); err != nil {
+			logger.Debug("nativessh: clients netstack server stopped: %v", err)
+		}
+	}()
+	return h, nil
+}
--- a/go.mod
+++ b/go.mod
@@ -3,10 +3,13 @@ module github.com/fosrl/newt
 go 1.25.0

 require (
+	github.com/coder/websocket v1.8.14
+	github.com/creack/pty v1.1.24
 	github.com/gaissmai/bart v0.26.1
 	github.com/gorilla/websocket v1.5.3
 	github.com/moby/moby/api v1.54.2
 	github.com/moby/moby/client v0.4.1
+	github.com/msteinert/pam/v2 v2.1.0
 	github.com/prometheus/client_golang v1.23.2
 	github.com/vishvananda/netlink v1.3.1
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.68.0
--- a/go.sum
+++ b/go.sum
@@ -6,10 +6,14 @@ github.com/cenkalti/backoff/v5 v5.0.3 h1:ZN+IMa753KfX5hd8vVaMixjnqRZ3y8CuJKRKj1x
 github.com/cenkalti/backoff/v5 v5.0.3/go.mod h1:rkhZdG3JZukswDf7f0cwqPNk4K0sa+F97BxZthm/crw=
 github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
 github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
+github.com/coder/websocket v1.8.14 h1:9L0p0iKiNOibykf283eHkKUHHrpG7f65OE3BhhO7v9g=
+github.com/coder/websocket v1.8.14/go.mod h1:NX3SzP+inril6yawo5CQXx8+fk145lPDC6pumgx0mVg=
 github.com/containerd/errdefs v1.0.0 h1:tg5yIfIlQIrxYtu9ajqY42W3lpS19XqdxRQeEwYG8PI=
 github.com/containerd/errdefs v1.0.0/go.mod h1:+YBYIdtsnF4Iw6nWZhJcqGSg/dwvV7tyJ/kCkyJ2k+M=
 github.com/containerd/errdefs/pkg v0.3.0 h1:9IKJ06FvyNlexW690DXuQNx2KA2cUJXx151Xdx3ZPPE=
 github.com/containerd/errdefs/pkg v0.3.0/go.mod h1:NJw6s9HwNuRhnjJhM7pylWwMyAkmCQvQ4GpJHEqRLVk=
+github.com/creack/pty v1.1.24 h1:bJrF4RRfyJnbTJqzRLHzcGaZK1NeM5kTC9jGgovnR1s=
+github.com/creack/pty v1.1.24/go.mod h1:08sCNb52WyoAwi2QDyzUCTgcvVFhUzewun7wtTfvcwE=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/distribution/reference v0.6.0 h1:0IXCQ5g4/QMHHkarYzh5l+u8T3t73zM5QvfrDyIgxBk=
@@ -53,6 +57,8 @@ github.com/moby/moby/api v1.54.2 h1:wiat9QAhnDQjA7wk1kh/TqHz2I1uUA7M7t9SAl/JNXg=
 github.com/moby/moby/api v1.54.2/go.mod h1:+RQ6wluLwtYaTd1WnPLykIDPekkuyD/ROWQClE83pzs=
 github.com/moby/moby/client v0.4.1 h1:DMQgisVoMkmMs7fp3ROSdiBnoAu8+vo3GggFl06M/wY=
 github.com/moby/moby/client v0.4.1/go.mod h1:z52C9O2POPOsnxZAy//WtKcQ32P+jT/NGeXu/7nfjGQ=
+github.com/msteinert/pam/v2 v2.1.0 h1:er5F9TKV5nGFuTt12ubtqPHEUdeBwReP7vd3wovidGY=
+github.com/msteinert/pam/v2 v2.1.0/go.mod h1:KT28NNIcDFf3PcBmNI2mIGO4zZJ+9RSs/At2PB3IDVc=
 github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 h1:C3w9PqII01/Oq1c1nUAm88MOHcQC9l5mIlSMApZMrHA=
 github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822/go.mod h1:+n7T8mK8HuQTcFwEeznm/DIxMOiR9yIdICNftLE1DvQ=
 github.com/opencontainers/go-digest v1.0.0 h1:apOUWs51W5PlhuyGyz9FCeeBIOUDA/6nW8Oi/yOhh5U=
@@ -119,6 +125,8 @@ golang.org/x/sys v0.2.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.10.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.43.0 h1:Rlag2XtaFTxp19wS8MXlJwTvoh8ArU6ezoyFsMyCTNI=
 golang.org/x/sys v0.43.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
+golang.org/x/term v0.42.0 h1:UiKe+zDFmJobeJ5ggPwOshJIVt6/Ft0rcfrXZDLWAWY=
+golang.org/x/term v0.42.0/go.mod h1:Dq/D+snpsbazcBG5+F9Q1n2rXV8Ma+71xEjTRufARgY=
 golang.org/x/text v0.36.0 h1:JfKh3XmcRPqZPKevfXVpI1wXPTqbkE5f7JA92a55Yxg=
 golang.org/x/text v0.36.0/go.mod h1:NIdBknypM8iqVmPiuco0Dh6P5Jcdk8lJL0CUebqK164=
 golang.org/x/time v0.12.0 h1:ScB/8o8olJvc+CQPWrK3fPZNfh7qgwCrY0zJmoEQLSE=
--- a/main.go
+++ b/main.go
@@ -23,9 +23,11 @@ import (
 	"time"

 	"github.com/fosrl/newt/authdaemon"
+	"github.com/fosrl/newt/browsergateway"
 	"github.com/fosrl/newt/docker"
 	"github.com/fosrl/newt/healthcheck"
 	"github.com/fosrl/newt/logger"
+	"github.com/fosrl/newt/nativessh"
 	"github.com/fosrl/newt/proxy"
 	"github.com/fosrl/newt/updates"
 	"github.com/fosrl/newt/util"
@@ -41,15 +43,24 @@ import (
 	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 )

+type BrowserGatewayTarget struct {
+	ID              int    `json:"id"`
+	Type            string `json:"type"`
+	Destination     string `json:"destination"`
+	DestinationPort int    `json:"destinationPort"`
+	AuthToken       string `json:"authToken"`
+}
+
 type WgData struct {
-	Endpoint           string               `json:"endpoint"`
-	RelayPort          uint16               `json:"relayPort"`
-	PublicKey          string               `json:"publicKey"`
-	ServerIP           string               `json:"serverIP"`
-	TunnelIP           string               `json:"tunnelIP"`
-	Targets            TargetsByType        `json:"targets"`
-	HealthCheckTargets []healthcheck.Config `json:"healthCheckTargets"`
-	ChainId            string               `json:"chainId"`
+	Endpoint              string                 `json:"endpoint"`
+	RelayPort             uint16                 `json:"relayPort"`
+	PublicKey             string                 `json:"publicKey"`
+	ServerIP              string                 `json:"serverIP"`
+	TunnelIP              string                 `json:"tunnelIP"`
+	Targets               TargetsByType          `json:"targets"`
+	HealthCheckTargets    []healthcheck.Config   `json:"healthCheckTargets"`
+	BrowserGatewayTargets []BrowserGatewayTarget `json:"browserGatewayTargets"`
+	ChainId               string                 `json:"chainId"`
 }

 type TargetsByType struct {
@@ -124,6 +135,7 @@ var (
 	port                               uint16
 	portStr                            string
 	disableClients                     bool
+	disableSSH                         bool
 	updownScript                       string
 	dockerSocket                       string
 	dockerEnforceNetworkValidation     string
@@ -135,6 +147,8 @@ var (
 	pingStopChan                       chan struct{}
 	stopFunc                           func()
 	pendingRegisterChainId             string
+	browserGateway                     *browsergateway.Gateway
+	browserGatewayStop                 func()
 	pendingPingChainId                 string
 	healthFile                         string
 	useNativeInterface                 bool
@@ -145,7 +159,6 @@ var (
 	authDaemonKey                      string
 	authDaemonPrincipalsFile           string
 	authDaemonCACertPath               string
-	authDaemonEnabled                  bool
 	authDaemonGenerateRandomPassword   bool
 	// Build/version (can be overridden via -ldflags "-X main.newtVersion=...")
 	newtVersion  = "version_replaceme"
@@ -244,7 +257,6 @@ func runNewtMain(ctx context.Context) {
 	authDaemonKey = os.Getenv("AD_KEY")
 	authDaemonPrincipalsFile = os.Getenv("AD_PRINCIPALS_FILE")
 	authDaemonCACertPath = os.Getenv("AD_CA_CERT_PATH")
-	authDaemonEnabledEnv := os.Getenv("AUTH_DAEMON_ENABLED")
 	authDaemonGenerateRandomPasswordEnv := os.Getenv("AD_GENERATE_RANDOM_PASSWORD")

 	// Metrics/observability env mirrors
@@ -257,6 +269,8 @@ func runNewtMain(ctx context.Context) {

 	disableClientsEnv := os.Getenv("DISABLE_CLIENTS")
 	disableClients = disableClientsEnv == "true"
+	disableSSHEnv := os.Getenv("DISABLE_SSH")
+	disableSSH = disableSSHEnv == "true"
 	useNativeInterfaceEnv := os.Getenv("USE_NATIVE_INTERFACE")
 	useNativeInterface = useNativeInterfaceEnv == "true"
 	enforceHealthcheckCertEnv := os.Getenv("ENFORCE_HC_CERT")
@@ -329,6 +343,9 @@ func runNewtMain(ctx context.Context) {
 	if disableClientsEnv == "" {
 		flag.BoolVar(&disableClients, "disable-clients", false, "Disable clients on the WireGuard interface")
 	}
+	if disableSSHEnv == "" {
+		flag.BoolVar(&disableSSH, "disable-ssh", false, "Disable SSH auth daemon and native SSH mode (remote auth daemon still works)")
+	}
 	if enforceHealthcheckCertEnv == "" {
 		flag.BoolVar(&enforceHealthcheckCert, "enforce-hc-cert", false, "Enforce certificate validation for health checks (default: false, accepts any cert)")
 	}
@@ -363,6 +380,8 @@ func runNewtMain(ctx context.Context) {
 	if tlsClientKey == "" {
 		flag.StringVar(&tlsClientKey, "tls-client-key", "", "Path to client private key file (PEM/DER format)")
 	}
+	// add a dummy input for --auth-daemon but ignore it since the auth daemon is always enabled now and this is just for backward compatibility with older versions
+	flag.Bool("auth-daemon", false, "Enable auth daemon mode (deprecated, always enabled)")

 	// Handle multiple CA files
 	var tlsClientCAsFlag stringSlice
@@ -474,13 +493,7 @@ func runNewtMain(ctx context.Context) {
 	if authDaemonCACertPath == "" {
 		flag.StringVar(&authDaemonCACertPath, "ad-ca-cert-path", "/etc/ssh/ca.pem", "Path to the CA certificate file for auth daemon")
 	}
-	if authDaemonEnabledEnv == "" {
-		flag.BoolVar(&authDaemonEnabled, "auth-daemon", false, "Enable auth daemon mode (runs alongside normal newt operation)")
-	} else {
-		if v, err := strconv.ParseBool(authDaemonEnabledEnv); err == nil {
-			authDaemonEnabled = v
-		}
-	}
+
 	if authDaemonGenerateRandomPasswordEnv == "" {
 		flag.BoolVar(&authDaemonGenerateRandomPassword, "ad-generate-random-password", false, "Generate a random password for authenticated users")
 	} else {
@@ -519,11 +532,12 @@ func runNewtMain(ctx context.Context) {
 	loggerLevel := util.ParseLogLevel(logLevel)

 	// Start auth daemon if enabled
-	if authDaemonEnabled {
+	if !disableSSH {
 		if err := startAuthDaemon(ctx); err != nil {
 			logger.Fatal("Failed to start auth daemon: %v", err)
 		}
 	}
+
 	logger.GetLogger().SetLevel(loggerLevel)

 	// Initialize telemetry after flags are parsed (so flags override env)
@@ -740,8 +754,15 @@ func runNewtMain(ctx context.Context) {
 	var connectionBlocked atomic.Bool
 	var currentPM atomic.Pointer[proxy.ProxyManager]

+	// In-memory SSH credentials shared with the native SSH server started in
+	// the clients netstack once the WireGuard interface is ready.
+	var sshCredStore *nativessh.CredentialStore
+	if !disableSSH {
+		sshCredStore = nativessh.NewCredentialStore()
+	}
+
 	if !disableClients {
-		setupClients(client)
+		setupClients(client, sshCredStore)
 	}

 	// Initialize connection blocked state from config
@@ -787,6 +808,13 @@ func runNewtMain(ctx context.Context) {
 			pingStopChan = nil
 		}

+		// Shutdown browser gateway if running
+		if browserGatewayStop != nil {
+			browserGatewayStop()
+			browserGatewayStop = nil
+			browserGateway = nil
+		}
+
 		// Stop proxy manager if running
 		if pm != nil {
 			pm.Stop()
@@ -996,6 +1024,42 @@ persistent_keepalive_interval=5`, util.FixKey(privateKey.String()), util.FixKey(
 		if err != nil {
 			logger.Error("Failed to start proxy manager: %v", err)
 		}
+
+		// Start browser gateway if targets are present
+		if len(wgData.BrowserGatewayTargets) > 0 {
+			// Shutdown any existing gateway first
+			if browserGatewayStop != nil {
+				browserGatewayStop()
+				browserGatewayStop = nil
+			}
+
+			bgTargets := make([]browsergateway.Target, 0, len(wgData.BrowserGatewayTargets))
+			for _, t := range wgData.BrowserGatewayTargets {
+				bgTargets = append(bgTargets, browsergateway.Target{
+					ID:              t.ID,
+					Type:            t.Type,
+					Destination:     t.Destination,
+					DestinationPort: t.DestinationPort,
+					AuthToken:       t.AuthToken,
+				})
+			}
+
+			browserGateway = browsergateway.New(browsergateway.Config{})
+			browserGateway.SetTargets(bgTargets)
+
+			ln, bgErr := tnet.ListenTCP(&net.TCPAddr{Port: browsergateway.ListenPort})
+			if bgErr != nil {
+				logger.Error("Failed to start browser gateway listener: %v", bgErr)
+			} else {
+				browserGatewayStop = func() { _ = ln.Close() }
+				go func() {
+					logger.Info("Browser gateway started on port %d", browsergateway.ListenPort)
+					if startErr := browserGateway.Start(ln); startErr != nil {
+						logger.Error("Browser gateway stopped with error: %v", startErr)
+					}
+				}()
+			}
+		}
 	})

 	client.RegisterHandler("newt/wg/reconnect", func(msg websocket.WSMessage) {
@@ -1716,14 +1780,14 @@ persistent_keepalive_interval=5`, util.FixKey(privateKey.String()), util.FixKey(

 		// Define the structure of the incoming message
 		type SSHCertData struct {
-			MessageId          int    `json:"messageId"`
-			AgentPort          int    `json:"agentPort"`
-			AgentHost          string `json:"agentHost"`
-			ExternalAuthDaemon bool   `json:"externalAuthDaemon"`
-			CACert             string `json:"caCert"`
-			Username           string `json:"username"`
-			NiceID             string `json:"niceId"`
-			Metadata           struct {
+			MessageId      int    `json:"messageId"`
+			AgentPort      int    `json:"agentPort"`
+			AgentHost      string `json:"agentHost"`
+			AuthDaemonMode string `json:"authDaemonMode"` // site, remote, native
+			CACert         string `json:"caCert"`
+			Username       string `json:"username"`
+			NiceID         string `json:"niceId"`
+			Metadata       struct {
 				SudoMode     string   `json:"sudoMode"`
 				SudoCommands []string `json:"sudoCommands"`
 				Homedir      bool     `json:"homedir"`
@@ -1746,31 +1810,45 @@ persistent_keepalive_interval=5`, util.FixKey(privateKey.String()), util.FixKey(
 			return
 		}

-		// Check if we're running the auth daemon internally
-		if authDaemonServer != nil && !certData.ExternalAuthDaemon { // if the auth daemon is running internally and the external auth daemon is not enabled
+		// Use a switch statement for AuthDaemonMode
+		switch certData.AuthDaemonMode {
+		case "site":
 			// Call ProcessConnection directly when running internally
 			logger.Debug("Calling internal auth daemon ProcessConnection for user %s", certData.Username)

-			authDaemonServer.ProcessConnection(authdaemon.ConnectionRequest{
-				CaCert:   certData.CACert,
-				NiceId:   certData.NiceID,
-				Username: certData.Username,
-				Metadata: authdaemon.ConnectionMetadata{
-					SudoMode:     certData.Metadata.SudoMode,
-					SudoCommands: certData.Metadata.SudoCommands,
-					Homedir:      certData.Metadata.Homedir,
-					Groups:       certData.Metadata.Groups,
-				},
-			})
-
-			// Send success response back to cloud
-			err = client.SendMessage("ws/round-trip/complete", map[string]interface{}{
-				"messageId": certData.MessageId,
-				"complete":  true,
-			})
+			if authDaemonServer != nil {
+				authDaemonServer.ProcessConnection(authdaemon.ConnectionRequest{
+					CaCert:   certData.CACert,
+					NiceId:   certData.NiceID,
+					Username: certData.Username,
+					Metadata: authdaemon.ConnectionMetadata{
+						SudoMode:     certData.Metadata.SudoMode,
+						SudoCommands: certData.Metadata.SudoCommands,
+						Homedir:      certData.Metadata.Homedir,
+						Groups:       certData.Metadata.Groups,
+					},
+				})
+				// Send success response back to cloud
+				err = client.SendMessage("ws/round-trip/complete", map[string]interface{}{
+					"messageId": certData.MessageId,
+					"complete":  true,
+				})
+			} else {
+				logger.Error("Auth daemon server is not initialized, cannot process connection")
+				// Send failure response back to cloud
+				err = client.SendMessage("ws/round-trip/complete", map[string]interface{}{
+					"messageId": certData.MessageId,
+					"complete":  true,
+					"error":     "auth daemon server not initialized",
+				})
+				if err != nil {
+					logger.Error("Failed to send SSH cert failure response: %v", err)
+				}
+				return
+			}

 			logger.Info("Successfully processed connection via internal auth daemon for user %s", certData.Username)
-		} else {
+		case "remote":
 			// External auth daemon mode - make HTTP request
 			// Check if auth daemon key is configured
 			if authDaemonKey == "" {
@@ -1867,6 +1945,48 @@ persistent_keepalive_interval=5`, util.FixKey(privateKey.String()), util.FixKey(
 			}

 			logger.Info("Successfully registered SSH certificate with external auth daemon for user %s", certData.Username)
+		case "native":
+			logger.Debug("Processing SSH cert for native SSH server for user %s", certData.Username)
+			if authDaemonServer != nil && sshCredStore != nil {
+				authDaemonServer.ProcessConnection(authdaemon.ConnectionRequest{
+					CaCert:   "", // dont write the cert to the host
+					NiceId:   "", // dont write the cert to the host
+					Username: certData.Username,
+					Metadata: authdaemon.ConnectionMetadata{ // but push the user
+						SudoMode:     certData.Metadata.SudoMode,
+						SudoCommands: certData.Metadata.SudoCommands,
+						Homedir:      certData.Metadata.Homedir,
+						Groups:       certData.Metadata.Groups,
+					},
+				})
+
+				// Update in-memory credentials used by the native SSH server.
+				if err := sshCredStore.SetCAKey(certData.CACert); err != nil {
+					logger.Error("nativessh: failed to set CA key: %v", err)
+				}
+				sshCredStore.AddPrincipals(certData.Username, certData.NiceID)
+				logger.Info("nativessh: updated credentials for user %s (niceId=%s)", certData.Username, certData.NiceID)
+			} else {
+				logger.Error("Auth daemon server or SSH credential store not initialized, cannot process connection")
+				// Send failure response back to cloud
+				err = client.SendMessage("ws/round-trip/complete", map[string]interface{}{
+					"messageId": certData.MessageId,
+					"complete":  true,
+					"error":     "auth daemon server or SSH credential store not initialized",
+				})
+				if err != nil {
+					logger.Error("Failed to send SSH cert failure response: %v", err)
+				}
+				return
+			}
+		default:
+			logger.Error("Unknown auth daemon mode: %s", certData.AuthDaemonMode)
+			client.SendMessage("ws/round-trip/complete", map[string]interface{}{
+				"messageId": certData.MessageId,
+				"complete":  true,
+				"error":     fmt.Sprintf("unknown auth daemon mode: %s", certData.AuthDaemonMode),
+			})
+			return
 		}

 		// Send success response back to cloud
@@ -1879,6 +1999,94 @@ persistent_keepalive_interval=5`, util.FixKey(privateKey.String()), util.FixKey(
 		}
 	})

+	// Register handler for adding browser gateway targets dynamically
+	client.RegisterHandler("newt/browsergateway/add", func(msg websocket.WSMessage) {
+		logger.Debug("Received browser gateway add message")
+
+		type BrowserGatewayAddData struct {
+			Targets []BrowserGatewayTarget `json:"targets"`
+		}
+
+		var addData BrowserGatewayAddData
+		jsonData, err := json.Marshal(msg.Data)
+		if err != nil {
+			logger.Error("Error marshaling browser gateway add data: %v", err)
+			return
+		}
+		if err := json.Unmarshal(jsonData, &addData); err != nil {
+			logger.Error("Error unmarshaling browser gateway add data: %v", err)
+			return
+		}
+
+		if len(addData.Targets) == 0 {
+			return
+		}
+
+		// If the gateway doesn't exist yet but we have a tunnel, start it
+		if browserGateway == nil && tnet != nil {
+			browserGateway = browsergateway.New(browsergateway.Config{})
+			ln, bgErr := tnet.ListenTCP(&net.TCPAddr{Port: browsergateway.ListenPort})
+			if bgErr != nil {
+				logger.Error("Failed to start browser gateway listener: %v", bgErr)
+				browserGateway = nil
+			} else {
+				browserGatewayStop = func() { _ = ln.Close() }
+				go func() {
+					logger.Info("Browser gateway started on port %d", browsergateway.ListenPort)
+					if startErr := browserGateway.Start(ln); startErr != nil {
+						logger.Error("Browser gateway stopped with error: %v", startErr)
+					}
+				}()
+			}
+		}
+
+		if browserGateway == nil {
+			logger.Warn("Browser gateway not available, cannot add targets")
+			return
+		}
+
+		for _, t := range addData.Targets {
+			browserGateway.AddTarget(browsergateway.Target{
+				ID:              t.ID,
+				Type:            t.Type,
+				Destination:     t.Destination,
+				DestinationPort: t.DestinationPort,
+				AuthToken:       t.AuthToken,
+			})
+			logger.Debug("Added browser gateway target %d", t.ID)
+		}
+	})
+
+	// Register handler for removing browser gateway targets dynamically
+	client.RegisterHandler("newt/browsergateway/remove", func(msg websocket.WSMessage) {
+		logger.Debug("Received browser gateway remove message")
+
+		type BrowserGatewayRemoveData struct {
+			IDs []int `json:"ids"`
+		}
+
+		var removeData BrowserGatewayRemoveData
+		jsonData, err := json.Marshal(msg.Data)
+		if err != nil {
+			logger.Error("Error marshaling browser gateway remove data: %v", err)
+			return
+		}
+		if err := json.Unmarshal(jsonData, &removeData); err != nil {
+			logger.Error("Error unmarshaling browser gateway remove data: %v", err)
+			return
+		}
+
+		if browserGateway == nil {
+			logger.Warn("Browser gateway not available, cannot remove targets")
+			return
+		}
+
+		for _, id := range removeData.IDs {
+			browserGateway.RemoveTarget(id)
+			logger.Debug("Removed browser gateway target %d", id)
+		}
+	})
+
 	client.OnConnect(func() error {
 		publicKey = privateKey.PublicKey()
 		logger.Debug("Public key: %s", publicKey)
--- a/nativessh/auth.go
+++ b/nativessh/auth.go
@@ -0,0 +1,76 @@
+package nativessh
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"os/user"
+	"path/filepath"
+	"strings"
+
+	"golang.org/x/crypto/ssh"
+)
+
+// CheckAuthorizedKeys reports whether key matches any entry in the system
+// user's ~/.ssh/authorized_keys file.  Returns false (not an error) when the
+// user or file does not exist.
+func CheckAuthorizedKeys(username string, key ssh.PublicKey) bool {
+	u, err := user.Lookup(username)
+	if err != nil {
+		return false
+	}
+	f, err := os.Open(filepath.Join(u.HomeDir, ".ssh", "authorized_keys"))
+	if err != nil {
+		return false
+	}
+	defer f.Close()
+
+	want := ssh.FingerprintSHA256(key)
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		parsed, _, _, _, err := ssh.ParseAuthorizedKey([]byte(line))
+		if err != nil {
+			continue
+		}
+		if ssh.FingerprintSHA256(parsed) == want {
+			return true
+		}
+	}
+	return false
+}
+
+// SystemUserExists reports whether a user account with the given name exists
+// on the host OS.
+func SystemUserExists(username string) bool {
+	_, err := user.Lookup(username)
+	return err == nil
+}
+
+// Authenticate authenticates a user for a browser-based native SSH session.
+// It tries, in order:
+//  1. Private key — parses privateKeyPEM and checks it against the user's
+//     ~/.ssh/authorized_keys.
+//  2. Password — verifies password via the host OS PAM stack (Linux only).
+//
+// Returns nil on the first method that succeeds, or an error if all fail.
+func Authenticate(username, password, privateKeyPEM string) error {
+	if !SystemUserExists(username) {
+		return fmt.Errorf("user %q does not exist", username)
+	}
+	if privateKeyPEM != "" {
+		signer, err := ssh.ParsePrivateKey([]byte(privateKeyPEM))
+		if err == nil && CheckAuthorizedKeys(username, signer.PublicKey()) {
+			return nil
+		}
+	}
+	if password != "" {
+		if err := VerifySystemPassword(username, password); err == nil {
+			return nil
+		}
+	}
+	return fmt.Errorf("authentication failed for user %q", username)
+}
--- a/nativessh/pam_linux.go
+++ b/nativessh/pam_linux.go
@@ -0,0 +1,34 @@
+//go:build linux
+
+package nativessh
+
+import (
+	"fmt"
+
+	"github.com/msteinert/pam/v2"
+)
+
+// VerifySystemPassword authenticates username/password via PAM using the
+// "sshd" service stack.  It returns nil on success and an error on failure.
+// The caller must not reveal the error detail to the client.
+func VerifySystemPassword(username, password string) error {
+	tx, err := pam.StartFunc("sshd", username, func(s pam.Style, msg string) (string, error) {
+		switch s {
+		case pam.PromptEchoOff, pam.PromptEchoOn:
+			return password, nil
+		default:
+			return "", nil
+		}
+	})
+	if err != nil {
+		return fmt.Errorf("PAM start: %w", err)
+	}
+
+	if err := tx.Authenticate(0); err != nil {
+		return fmt.Errorf("PAM authenticate: %w", err)
+	}
+	if err := tx.AcctMgmt(0); err != nil {
+		return fmt.Errorf("PAM acct_mgmt: %w", err)
+	}
+	return nil
+}
--- a/nativessh/pam_other.go
+++ b/nativessh/pam_other.go
@@ -0,0 +1,11 @@
+//go:build !linux
+
+package nativessh
+
+import "errors"
+
+// VerifySystemPassword is not supported on non-Linux platforms; it always
+// returns an error so that password authentication is never accepted.
+func VerifySystemPassword(username, password string) error {
+	return errors.New("password authentication not supported on this platform")
+}
--- a/nativessh/pty.go
+++ b/nativessh/pty.go
@@ -0,0 +1,89 @@
+package nativessh
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"sync"
+
+	"github.com/creack/pty"
+)
+
+// PTYSession is a running shell process attached to a PTY.
+// It implements io.ReadWriteCloser so it can be bridged to any transport.
+type PTYSession struct {
+	ptmx     *os.File
+	cmd      *exec.Cmd
+	waitOnce sync.Once
+	exitCode int
+}
+
+// findShell returns the path to the best available interactive shell by
+// checking preferred shells in order, falling back to /bin/sh.
+func findShell() string {
+	preferred := []string{"zsh", "bash", "fish", "ksh", "sh"}
+	for _, name := range preferred {
+		if path, err := exec.LookPath(name); err == nil {
+			return path
+		}
+	}
+	return "/bin/sh"
+}
+
+// NewPTYSession spawns the best available shell in a PTY.
+func NewPTYSession() (*PTYSession, error) {
+	shell := findShell()
+	cmd := exec.Command(shell)
+	cmd.Env = append(os.Environ(), "TERM=xterm-256color")
+	ptmx, err := pty.Start(cmd)
+	if err != nil {
+		return nil, fmt.Errorf("pty start: %w", err)
+	}
+	return &PTYSession{ptmx: ptmx, cmd: cmd}, nil
+}
+
+// Read reads output from the PTY.
+func (p *PTYSession) Read(b []byte) (int, error) {
+	return p.ptmx.Read(b)
+}
+
+// Write writes input to the PTY.
+func (p *PTYSession) Write(b []byte) (int, error) {
+	return p.ptmx.Write(b)
+}
+
+// Resize changes the PTY window size.
+func (p *PTYSession) Resize(cols, rows uint16) error {
+	return pty.Setsize(p.ptmx, &pty.Winsize{Cols: cols, Rows: rows})
+}
+
+// wait waits for the child process to exit exactly once and records its exit
+// code. Safe to call concurrently or multiple times.
+func (p *PTYSession) wait() {
+	p.waitOnce.Do(func() {
+		err := p.cmd.Wait()
+		if err != nil {
+			var exitErr *exec.ExitError
+			if errors.As(err, &exitErr) {
+				p.exitCode = exitErr.ExitCode()
+				return
+			}
+			p.exitCode = 1
+		}
+	})
+}
+
+// ExitCode waits for the shell process to exit and returns its exit code.
+// It is safe to call before or after Close.
+func (p *PTYSession) ExitCode() int {
+	p.wait()
+	return p.exitCode
+}
+
+// Close closes the PTY and waits for the child process to exit.
+func (p *PTYSession) Close() error {
+	err := p.ptmx.Close()
+	p.wait()
+	return err
+}
--- a/nativessh/pty_unix.go
+++ b/nativessh/pty_unix.go
@@ -0,0 +1,69 @@
+//go:build !windows
+
+package nativessh
+
+import (
+	"fmt"
+	"os/exec"
+	"os/user"
+	"strconv"
+	"syscall"
+
+	"github.com/creack/pty"
+)
+
+// NewPTYSessionAs spawns an interactive shell in a PTY running as the given
+// system user.  The calling process must have sufficient privileges (typically
+// root / CAP_SETUID) to switch to a different UID/GID.
+func NewPTYSessionAs(username string) (*PTYSession, error) {
+	u, err := user.Lookup(username)
+	if err != nil {
+		return nil, fmt.Errorf("user lookup %q: %w", username, err)
+	}
+	uid, err := strconv.ParseUint(u.Uid, 10, 32)
+	if err != nil {
+		return nil, fmt.Errorf("parse uid: %w", err)
+	}
+	gid, err := strconv.ParseUint(u.Gid, 10, 32)
+	if err != nil {
+		return nil, fmt.Errorf("parse gid: %w", err)
+	}
+
+	// Collect supplementary group IDs.
+	groupIDs, err := u.GroupIds()
+	if err != nil {
+		groupIDs = []string{}
+	}
+	var groups []uint32
+	for _, g := range groupIDs {
+		gval, err := strconv.ParseUint(g, 10, 32)
+		if err == nil {
+			groups = append(groups, uint32(gval))
+		}
+	}
+
+	shell := findShell()
+	cmd := exec.Command(shell, "--login")
+	cmd.Env = []string{
+		"TERM=xterm-256color",
+		"HOME=" + u.HomeDir,
+		"USER=" + username,
+		"LOGNAME=" + username,
+		"SHELL=" + shell,
+		"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
+	}
+	cmd.Dir = u.HomeDir
+	cmd.SysProcAttr = &syscall.SysProcAttr{
+		Credential: &syscall.Credential{
+			Uid:    uint32(uid),
+			Gid:    uint32(gid),
+			Groups: groups,
+		},
+	}
+
+	ptmx, err := pty.Start(cmd)
+	if err != nil {
+		return nil, fmt.Errorf("pty start: %w", err)
+	}
+	return &PTYSession{ptmx: ptmx, cmd: cmd}, nil
+}
--- a/nativessh/server.go
+++ b/nativessh/server.go
@@ -0,0 +1,343 @@
+package nativessh
+
+import (
+	"crypto/ed25519"
+	"crypto/rand"
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"strings"
+	"sync"
+
+	"golang.org/x/crypto/ssh"
+)
+
+// CredentialStore holds in-memory SSH credentials that can be updated at runtime.
+// It is safe for concurrent use.
+type CredentialStore struct {
+	mu         sync.RWMutex
+	caKey      ssh.PublicKey
+	principals map[string]map[string]struct{} // username -> set of allowed principals
+}
+
+// NewCredentialStore returns an empty, ready-to-use CredentialStore.
+func NewCredentialStore() *CredentialStore {
+	return &CredentialStore{
+		principals: make(map[string]map[string]struct{}),
+	}
+}
+
+// SetCAKey parses and stores the CA public key from authorized_keys-format data.
+func (s *CredentialStore) SetCAKey(authorizedKeyData string) error {
+	key, _, _, _, err := ssh.ParseAuthorizedKey([]byte(authorizedKeyData))
+	if err != nil {
+		return fmt.Errorf("parse CA key: %w", err)
+	}
+	s.mu.Lock()
+	s.caKey = key
+	s.mu.Unlock()
+	return nil
+}
+
+// AddPrincipals records username and niceId as allowed principals for username.
+// Both values are stored; either can appear in the certificate's ValidPrincipals
+// field to satisfy the standard cert-auth principal check.
+func (s *CredentialStore) AddPrincipals(username, niceId string) {
+	username = strings.TrimSpace(username)
+	niceId = strings.TrimSpace(niceId)
+	if username == "" {
+		return
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.principals[username] == nil {
+		s.principals[username] = make(map[string]struct{})
+	}
+	s.principals[username][username] = struct{}{}
+	if niceId != "" {
+		s.principals[username][niceId] = struct{}{}
+	}
+}
+
+// get returns the CA key and the principal set for username under a read lock.
+func (s *CredentialStore) get(username string) (ssh.PublicKey, map[string]struct{}) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	return s.caKey, s.principals[username]
+}
+
+// ServerConfig holds configuration for the native SSH server.
+type ServerConfig struct {
+	// ListenAddr is the TCP address to listen on. Defaults to ":2222".
+	ListenAddr string
+	// Credentials provides in-memory CA key and per-user principals.
+	// Updates to the store are reflected immediately for new connections.
+	// If nil or the store has no CA key set, all connections are rejected.
+	Credentials *CredentialStore
+}
+
+// Server is a simple SSH server that authenticates clients via SSH certificate
+// auth only. Certificates must be signed by the configured CA and the
+// connecting username must appear in both the certificate's principal list and
+// the local principals file.
+type Server struct {
+	cfg ServerConfig
+}
+
+// NewServer creates a new Server. The ListenAddr defaults to ":2222" when empty.
+func NewServer(cfg ServerConfig) *Server {
+	if cfg.ListenAddr == "" {
+		cfg.ListenAddr = ":2222"
+	}
+	return &Server{cfg: cfg}
+}
+
+// buildSSHConfig builds the ssh.ServerConfig with multi-method authentication:
+//  1. Public key: host ~/.ssh/authorized_keys, then CA certificate.
+//  2. Password: system PAM stack (Linux only).
+func (s *Server) buildSSHConfig() (*ssh.ServerConfig, error) {
+	hostSigner, err := generateHostKey()
+	if err != nil {
+		return nil, fmt.Errorf("host key: %w", err)
+	}
+	cfg := &ssh.ServerConfig{
+		PublicKeyCallback: makePublicKeyCallback(s.cfg.Credentials),
+		PasswordCallback:  makePasswordCallback(),
+	}
+	cfg.AddHostKey(hostSigner)
+	return cfg, nil
+}
+
+// Serve accepts connections on ln and handles them. It returns when ln is
+// closed or a non-temporary Accept error occurs.
+func (s *Server) Serve(ln net.Listener) error {
+	sshCfg, err := s.buildSSHConfig()
+	if err != nil {
+		return err
+	}
+	log.Printf("nativessh: server listening on %s", ln.Addr())
+	for {
+		conn, err := ln.Accept()
+		if err != nil {
+			return err
+		}
+		go s.handleConn(conn, sshCfg)
+	}
+}
+
+// ListenAndServe starts the SSH server on the host network and blocks until
+// the listener is closed.
+func (s *Server) ListenAndServe() error {
+	ln, err := net.Listen("tcp", s.cfg.ListenAddr)
+	if err != nil {
+		return fmt.Errorf("listen %s: %w", s.cfg.ListenAddr, err)
+	}
+	defer ln.Close()
+	return s.Serve(ln)
+}
+
+func (s *Server) handleConn(conn net.Conn, cfg *ssh.ServerConfig) {
+	defer conn.Close()
+	sshConn, chans, reqs, err := ssh.NewServerConn(conn, cfg)
+	if err != nil {
+		log.Printf("nativessh: handshake failed from %s: %v", conn.RemoteAddr(), err)
+		return
+	}
+	defer sshConn.Close()
+	log.Printf("nativessh: connection from %s user=%s", conn.RemoteAddr(), sshConn.User())
+
+	go ssh.DiscardRequests(reqs)
+
+	for newChan := range chans {
+		if newChan.ChannelType() != "session" {
+			_ = newChan.Reject(ssh.UnknownChannelType, "unknown channel type")
+			continue
+		}
+		ch, requests, err := newChan.Accept()
+		if err != nil {
+			log.Printf("nativessh: channel accept error: %v", err)
+			return
+		}
+		go s.handleSession(ch, requests)
+	}
+}
+
+// handleSession drives a single SSH session channel. It waits for a pty-req
+// followed by a shell request and then bridges the PTY to the channel.
+func (s *Server) handleSession(ch ssh.Channel, requests <-chan *ssh.Request) {
+	defer ch.Close()
+
+	var (
+		sess    *PTYSession
+		started bool
+	)
+
+	for req := range requests {
+		switch req.Type {
+		case "pty-req":
+			var err error
+			if sess == nil {
+				sess, err = NewPTYSession()
+				if err != nil {
+					log.Printf("nativessh: PTY start error: %v", err)
+					if req.WantReply {
+						_ = req.Reply(false, nil)
+					}
+					return
+				}
+			}
+			cols, rows := parsePTYReq(req.Payload)
+			_ = sess.Resize(cols, rows)
+			if req.WantReply {
+				_ = req.Reply(true, nil)
+			}
+
+		case "shell":
+			if req.WantReply {
+				_ = req.Reply(true, nil)
+			}
+			if started || sess == nil {
+				continue
+			}
+			started = true
+			// PTY output → SSH channel.
+			go func() {
+				_, _ = io.Copy(ch, sess)
+				// Notify the client of the shell's exit status so it can
+				// disconnect cleanly instead of requiring a manual disconnect.
+				exitCode := sess.ExitCode()
+				exitStatusPayload := ssh.Marshal(struct{ Status uint32 }{uint32(exitCode)})
+				_, _ = ch.SendRequest("exit-status", false, exitStatusPayload)
+				_ = ch.CloseWrite()
+				sess.Close() //nolint:errcheck
+				// Close the channel so the ssh library closes the requests
+				// channel, which unblocks the for-range loop in handleSession
+				// and allows the deferred ch.Close() to run. Without this,
+				// handleSession blocks forever waiting for requests to drain.
+				_ = ch.Close()
+			}()
+			// SSH channel input → PTY stdin.
+			go func() {
+				_, _ = io.Copy(sess, ch)
+			}()
+
+		case "window-change":
+			if sess != nil {
+				cols, rows := parseWindowChange(req.Payload)
+				_ = sess.Resize(cols, rows)
+			}
+			if req.WantReply {
+				_ = req.Reply(true, nil)
+			}
+
+		default:
+			if req.WantReply {
+				_ = req.Reply(false, nil)
+			}
+		}
+	}
+
+	if sess != nil && !started {
+		sess.Close() //nolint:errcheck
+	}
+}
+
+// makePublicKeyCallback returns a PublicKeyCallback that tries, in order:
+//  1. Host authorized_keys  – matches any key in the OS user's
+//     ~/.ssh/authorized_keys file.
+//  2. CA certificate        – validates an SSH certificate signed by the
+//     configured CA and checks that the user appears in the principals map.
+//
+// store may be nil or empty; those paths are simply skipped.
+func makePublicKeyCallback(store *CredentialStore) func(ssh.ConnMetadata, ssh.PublicKey) (*ssh.Permissions, error) {
+	return func(meta ssh.ConnMetadata, key ssh.PublicKey) (*ssh.Permissions, error) {
+		// 1. Host authorized_keys.
+		if CheckAuthorizedKeys(meta.User(), key) {
+			log.Printf("nativessh: authorized_keys auth for user %q", meta.User())
+			return &ssh.Permissions{}, nil
+		}
+
+		// 2. CA certificate.
+		if store != nil {
+			caKey, userPrincipals := store.get(meta.User())
+			if caKey != nil {
+				checker := &ssh.CertChecker{
+					IsUserAuthority: func(auth ssh.PublicKey) bool {
+						return ssh.FingerprintSHA256(auth) == ssh.FingerprintSHA256(caKey)
+					},
+				}
+				perms, err := checker.Authenticate(meta, key)
+				if err == nil {
+					if len(userPrincipals) == 0 {
+						return nil, fmt.Errorf("user %q not in allowed principals list", meta.User())
+					}
+					log.Printf("nativessh: CA cert auth for user %q", meta.User())
+					return perms, nil
+				}
+			}
+		}
+
+		return nil, fmt.Errorf("public key not authorized for user %q", meta.User())
+	}
+}
+
+// makePasswordCallback returns a PasswordCallback that validates the supplied
+// password via the host OS PAM stack.  On non-Linux platforms this always
+// fails (see pam_other.go).
+func makePasswordCallback() func(ssh.ConnMetadata, []byte) (*ssh.Permissions, error) {
+	return func(meta ssh.ConnMetadata, password []byte) (*ssh.Permissions, error) {
+		if err := VerifySystemPassword(meta.User(), string(password)); err != nil {
+			// Return a generic message to the client; log the real reason.
+			log.Printf("nativessh: password auth failed for user %q: %v", meta.User(), err)
+			return nil, fmt.Errorf("permission denied")
+		}
+		log.Printf("nativessh: password auth for user %q", meta.User())
+		return &ssh.Permissions{}, nil
+	}
+}
+
+// generateHostKey generates a fresh ephemeral Ed25519 host key in memory.
+// A new key is created on every server start; nothing is written to disk.
+func generateHostKey() (ssh.Signer, error) {
+	_, priv, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		return nil, fmt.Errorf("generate host key: %w", err)
+	}
+	log.Printf("nativessh: generated ephemeral Ed25519 host key")
+	return ssh.NewSignerFromKey(priv)
+}
+
+// ptyRequestMsg mirrors the SSH wire format for pty-req (RFC 4254 §6.2).
+type ptyRequestMsg struct {
+	Term     string
+	Columns  uint32
+	Rows     uint32
+	Width    uint32
+	Height   uint32
+	Modelist string
+}
+
+func parsePTYReq(payload []byte) (cols, rows uint16) {
+	var req ptyRequestMsg
+	if err := ssh.Unmarshal(payload, &req); err != nil {
+		return 80, 24
+	}
+	return uint16(req.Columns), uint16(req.Rows)
+}
+
+// windowChangeMsg mirrors the SSH wire format for window-change (RFC 4254 §6.7).
+type windowChangeMsg struct {
+	Columns uint32
+	Rows    uint32
+	Width   uint32
+	Height  uint32
+}
+
+func parseWindowChange(payload []byte) (cols, rows uint16) {
+	var msg windowChangeMsg
+	if err := ssh.Unmarshal(payload, &msg); err != nil {
+		return 80, 24
+	}
+	return uint16(msg.Columns), uint16(msg.Rows)
+}