Add optional HTTP Basic Auth support for tunnel clients

Clients can now set TUNNEL_AUTH_USER and TUNNEL_AUTH_PASS to have the
server add a Traefik basicauth middleware in front of the tunnel route.
Credentials are sent as tunnel metadata over the SSH channel and the
server generates a bcrypt htpasswd entry for Traefik's Docker labels.

Co-authored-by: Cursor <cursoragent@cursor.com>

cmd/client/main.go

@@ -32,6 +32,10 @@ func main() {
 	domain := envRequired("TUNNEL_DOMAIN")
 	keyPath := envOr("TUNNEL_KEY", "/keys/id_ed25519")
 
+	// Optional HTTP Basic Auth credentials for Traefik middleware.
+	authUser := envOr("TUNNEL_AUTH_USER", "")
+	authPass := envOr("TUNNEL_AUTH_PASS", "")
+
 	localPortStr := envOr("TUNNEL_PORT", "8080")
 	localPort, err := strconv.Atoi(localPortStr)
 	if err != nil {
@@ -50,7 +54,11 @@ func main() {
 	maxBackoff := 30 * time.Second
 
 	for {
+		if authUser != "" {
+			log.Printf("Connecting to %s (domain=%s, local_port=%d, basicauth=enabled)", serverAddr, domain, localPort)
+		} else {
 			log.Printf("Connecting to %s (domain=%s, local_port=%d)", serverAddr, domain, localPort)
+		}
 
 		sshClient, err := client.Connect(serverAddr, signer)
 		if err != nil {
@@ -65,7 +73,7 @@ func main() {
 		log.Printf("Connected to %s", serverAddr)
 
 		// Set up the reverse tunnel (blocks until disconnected).
-		if err := client.SetupTunnel(sshClient, domain, localPort); err != nil {
+		if err := client.SetupTunnel(sshClient, domain, localPort, authUser, authPass); err != nil {
 			log.Printf("Tunnel error: %v (reconnecting in %s)", err, backoff)
 		}
 

internal/client/tunnel.go

@@ -14,14 +14,18 @@ import (
 // TunnelRequest is the metadata sent to the server on the tunnel-request channel.
 type TunnelRequest struct {
 	Domain   string `json:"domain"`
+	AuthUser string `json:"auth_user,omitempty"` // optional HTTP Basic Auth username
+	AuthPass string `json:"auth_pass,omitempty"` // optional HTTP Basic Auth password
 }
 
 // SetupTunnel sends domain metadata and establishes a reverse port forward.
 // The server will allocate a port and register Traefik routes for the domain.
 // localPort is the port of the service running on the client side.
-func SetupTunnel(client *ssh.Client, domain string, localPort int) error {
+// authUser and authPass are optional; if both are non-empty, the server will
+// add a Traefik basicauth middleware in front of this tunnel.
+func SetupTunnel(client *ssh.Client, domain string, localPort int, authUser, authPass string) error {
 	// Step 1: Open custom channel to send domain metadata.
-	if err := sendMetadata(client, domain); err != nil {
+	if err := sendMetadata(client, domain, authUser, authPass); err != nil {
 		return fmt.Errorf("send metadata: %w", err)
 	}
 
@@ -46,13 +50,13 @@ func SetupTunnel(client *ssh.Client, domain string, localPort int) error {
 }
 
 // sendMetadata opens a custom channel and sends the tunnel request JSON.
-func sendMetadata(client *ssh.Client, domain string) error {
+func sendMetadata(client *ssh.Client, domain, authUser, authPass string) error {
 	ch, _, err := client.OpenChannel("tunnel-request", nil)
 	if err != nil {
 		return fmt.Errorf("open tunnel-request channel: %w", err)
 	}
 
-	req := TunnelRequest{Domain: domain}
+	req := TunnelRequest{Domain: domain, AuthUser: authUser, AuthPass: authPass}
 	data, err := json.Marshal(req)
 	if err != nil {
 		ch.Close()
@@ -64,7 +68,11 @@ func sendMetadata(client *ssh.Client, domain string) error {
 		return fmt.Errorf("write metadata: %w", err)
 	}
 
+	if authUser != "" {
+		log.Printf("Sent tunnel metadata: domain=%s (with basicauth)", domain)
+	} else {
 		log.Printf("Sent tunnel metadata: domain=%s", domain)
+	}
 
 	// Keep the channel open in a goroutine for disconnect detection.
 	go func() {

internal/server/labels.go

@@ -6,6 +6,7 @@ import (
 	"strings"
 	"sync"
 
+	"golang.org/x/crypto/bcrypt"
 	"golang.org/x/crypto/ssh"
 )
 
@@ -20,6 +21,7 @@ type LabelManager struct {
 	entrypoint   string // e.g. "websecure"
 	certResolver string // e.g. "letsencryptresolver"
 	labels       map[string]bool // track which tunnel keys we've added
+	authLabels   map[string]bool // track which tunnel keys have auth middleware
 }
 
 // NewLabelManager creates a label manager that updates Swarm service labels via SSH.
@@ -37,6 +39,7 @@ func NewLabelManager(
 		entrypoint:   entrypoint,
 		certResolver: certResolver,
 		labels:       make(map[string]bool),
+		authLabels:   make(map[string]bool),
 	}
 
 	// Verify we can reach the Swarm manager and the service exists.
@@ -54,12 +57,14 @@ func NewLabelManager(
 }
 
 // Add adds Traefik routing labels to the Swarm service for a tunnel.
-func (lm *LabelManager) Add(tunKey, domain string, port int) error {
+// If authUser and authPass are non-empty, a basicauth middleware is also added.
+func (lm *LabelManager) Add(tunKey, domain string, port int, authUser, authPass string) error {
 	lm.mu.Lock()
 	defer lm.mu.Unlock()
 
 	routerName := fmt.Sprintf("tunnel-%s-router", tunKey)
 	serviceName := fmt.Sprintf("tunnel-%s-service", tunKey)
+	middlewareName := fmt.Sprintf("tunnel-%s-auth", tunKey)
 
 	// Build the label-add flags for docker service update.
 	labelArgs := []string{
@@ -77,6 +82,26 @@ func (lm *LabelManager) Add(tunKey, domain string, port int) error {
 			fmt.Sprintf("%d", port)),
 	}
 
+	// If auth credentials are provided, add basicauth middleware labels.
+	if authUser != "" && authPass != "" {
+		htpasswd, err := generateHTPasswd(authUser, authPass)
+		if err != nil {
+			return fmt.Errorf("generate htpasswd for %s: %w", domain, err)
+		}
+		labelArgs = append(labelArgs,
+			labelFlag(
+				fmt.Sprintf("traefik.http.middlewares.%s.basicauth.users", middlewareName),
+				htpasswd,
+			),
+			labelFlag(
+				fmt.Sprintf("traefik.http.routers.%s.middlewares", routerName),
+				middlewareName,
+			),
+		)
+		lm.authLabels[tunKey] = true
+		log.Printf("BasicAuth middleware %s added for %s", middlewareName, domain)
+	}
+
 	cmd := fmt.Sprintf("docker service update --label-add %s %s",
 		strings.Join(labelArgs, " --label-add "), lm.serviceName)
 
@@ -101,6 +126,8 @@ func (lm *LabelManager) Remove(tunKey string) error {
 	routerName := fmt.Sprintf("tunnel-%s-router", tunKey)
 	serviceName := fmt.Sprintf("tunnel-%s-service", tunKey)
 
+	middlewareName := fmt.Sprintf("tunnel-%s-auth", tunKey)
+
 	// Build the label-rm flags.
 	rmLabels := []string{
 		fmt.Sprintf("traefik.http.routers.%s.rule", routerName),
@@ -111,6 +138,16 @@ func (lm *LabelManager) Remove(tunKey string) error {
 		fmt.Sprintf("traefik.http.services.%s.loadbalancer.server.port", serviceName),
 	}
 
+	// Remove auth middleware labels if they were added.
+	if lm.authLabels[tunKey] {
+		rmLabels = append(rmLabels,
+			fmt.Sprintf("traefik.http.middlewares.%s.basicauth.users", middlewareName),
+			fmt.Sprintf("traefik.http.routers.%s.middlewares", routerName),
+		)
+		delete(lm.authLabels, tunKey)
+		log.Printf("Removing BasicAuth middleware %s", middlewareName)
+	}
+
 	cmd := fmt.Sprintf("docker service update --label-rm %s %s",
 		strings.Join(rmLabels, " --label-rm "), lm.serviceName)
 
@@ -123,6 +160,18 @@ func (lm *LabelManager) Remove(tunKey string) error {
 	return nil
 }
 
+// generateHTPasswd creates a bcrypt-hashed htpasswd entry for Traefik basicauth.
+// The output format is user:$$hash (with $ escaped for Docker label values).
+func generateHTPasswd(user, pass string) (string, error) {
+	hash, err := bcrypt.GenerateFromPassword([]byte(pass), bcrypt.DefaultCost)
+	if err != nil {
+		return "", fmt.Errorf("bcrypt hash: %w", err)
+	}
+	// Traefik in Docker labels requires dollar signs to be doubled.
+	escaped := strings.ReplaceAll(string(hash), "$", "$$")
+	return fmt.Sprintf("%s:%s", user, escaped), nil
+}
+
 // labelFlag formats a --label-add value, quoting properly for shell.
 func labelFlag(key, value string) string {
 	return fmt.Sprintf("'%s=%s'", key, value)

internal/server/ssh.go

@@ -16,6 +16,8 @@ import (
 // TunnelRequest is the metadata a client sends when opening a tunnel channel.
 type TunnelRequest struct {
 	Domain   string `json:"domain"`
+	AuthUser string `json:"auth_user,omitempty"`
+	AuthPass string `json:"auth_pass,omitempty"`
 }
 
 // SSHServer handles incoming SSH connections and sets up reverse tunnels.
@@ -33,6 +35,8 @@ type activeTunnel struct {
 	listener net.Listener
 	done     chan struct{}
 	connKey  string // tracks which SSH connection owns this tunnel
+	authUser string // optional HTTP Basic Auth username
+	authPass string // optional HTTP Basic Auth password
 }
 
 // NewSSHServer creates a new SSH server with host key and authorized keys.
@@ -185,11 +189,17 @@ func (s *SSHServer) handleTunnelChannel(newChan ssh.NewChannel, connKey string)
 
 	log.Printf("Tunnel metadata received: domain=%s (conn=%s)", req.Domain, connKey)
 
+	if req.AuthUser != "" && req.AuthPass != "" {
+		log.Printf("Tunnel metadata includes basicauth for domain=%s", req.Domain)
+	}
+
 	// Store domain mapping for this connection so forward handler can use it.
 	s.mu.Lock()
 	s.activeTuns[connKey+"-meta"] = &activeTunnel{
 		domain:   req.Domain,
 		connKey:  connKey,
+		authUser: req.AuthUser,
+		authPass: req.AuthPass,
 	}
 	s.mu.Unlock()
 

internal/server/tunnel.go

@@ -137,9 +137,12 @@ func (s *SSHServer) handleForwardRequest(
 	// Determine the domain for Traefik label registration.
 	// Look up the metadata channel first, fall back to bind address.
 	domain := fwdReq.BindAddr
+	var authUser, authPass string
 	s.mu.Lock()
 	if meta, ok := s.activeTuns[connKey+"-meta"]; ok {
 		domain = meta.domain
+		authUser = meta.authUser
+		authPass = meta.authPass
 	}
 	s.mu.Unlock()
 
@@ -154,14 +157,16 @@ func (s *SSHServer) handleForwardRequest(
 		listener: listener,
 		done:     done,
 		connKey:  connKey,
+		authUser: authUser,
+		authPass: authPass,
 	}
 
 	s.mu.Lock()
 	s.activeTuns[tunKey] = tun
 	s.mu.Unlock()
 
-	// Register Traefik labels.
-	if err := s.labels.Add(tunKey, domain, port); err != nil {
+	// Register Traefik labels (with optional basicauth middleware).
+	if err := s.labels.Add(tunKey, domain, port, authUser, authPass); err != nil {
 		log.Printf("WARN: failed to add Traefik labels for %s: %v", domain, err)
 	} else {
 		log.Printf("Traefik labels added for %s -> port %d", domain, port)

stack.production.yml

@@ -11,8 +11,6 @@ services:
       SSH_PORT: "2222"
       PORT_RANGE_START: "10000"
       PORT_RANGE_END: "10100"
-      SSH_HOST_KEY: "/keys/host_key"
-      AUTHORIZED_KEYS: "/keys/authorized_keys"
       TRAEFIK_SSH_HOST: "ingress.nixc.us:65522"
       TRAEFIK_SSH_USER: "root"
       TRAEFIK_SSH_KEY: "/keys/deploy_key"
@@ -43,7 +41,6 @@ services:
         traefik.enable: "true"
         traefik.docker.network: "traefik"
         # Dynamic tunnel labels are added at runtime via docker service update.
-        # The base labels below just enable Traefik discovery.
       update_config:
         order: stop-first
         failure_action: rollback