[client] Add port forwarding to ssh proxy

client/cmd/ssh.go

@@ -634,7 +634,11 @@ func parseAndStartLocalForward(ctx context.Context, c *sshclient.Client, forward
 		return err
 	}
 
-	cmd.Printf("Local port forwarding: %s -> %s\n", localAddr, remoteAddr)
+	if err := validateDestinationPort(remoteAddr); err != nil {
+		return fmt.Errorf("invalid remote address: %w", err)
+	}
+
+	log.Debugf("Local port forwarding: %s -> %s", localAddr, remoteAddr)
 
 	go func() {
 		if err := c.LocalPortForward(ctx, localAddr, remoteAddr); err != nil && !errors.Is(err, context.Canceled) {
@@ -652,7 +656,11 @@ func parseAndStartRemoteForward(ctx context.Context, c *sshclient.Client, forwar
 		return err
 	}
 
-	cmd.Printf("Remote port forwarding: %s -> %s\n", remoteAddr, localAddr)
+	if err := validateDestinationPort(localAddr); err != nil {
+		return fmt.Errorf("invalid local address: %w", err)
+	}
+
+	log.Debugf("Remote port forwarding: %s -> %s", remoteAddr, localAddr)
 
 	go func() {
 		if err := c.RemotePortForward(ctx, remoteAddr, localAddr); err != nil && !errors.Is(err, context.Canceled) {
@@ -663,6 +671,35 @@ func parseAndStartRemoteForward(ctx context.Context, c *sshclient.Client, forwar
 	return nil
 }
 
+// validateDestinationPort checks that the destination address has a valid port.
+// Port 0 is only valid for bind addresses (where the OS picks an available port),
+// not for destination addresses where we need to connect.
+func validateDestinationPort(addr string) error {
+	if strings.HasPrefix(addr, "/") || strings.HasPrefix(addr, "./") {
+		return nil
+	}
+
+	_, portStr, err := net.SplitHostPort(addr)
+	if err != nil {
+		return fmt.Errorf("parse address %s: %w", addr, err)
+	}
+
+	port, err := strconv.Atoi(portStr)
+	if err != nil {
+		return fmt.Errorf("invalid port %s: %w", portStr, err)
+	}
+
+	if port == 0 {
+		return fmt.Errorf("port 0 is not valid for destination address")
+	}
+
+	if port < 0 || port > 65535 {
+		return fmt.Errorf("port %d out of range (1-65535)", port)
+	}
+
+	return nil
+}
+
 // parsePortForwardSpec parses port forward specifications like "8080:localhost:80" or "[::1]:8080:localhost:80".
 // Also supports Unix sockets like "8080:/tmp/socket" or "127.0.0.1:8080:/tmp/socket".
 func parsePortForwardSpec(spec string) (string, string, error) {

client/proto/daemon.proto

@@ -372,6 +372,7 @@ message SSHSessionInfo {
   string remoteAddress = 2;
   string command = 3;
   string jwtUsername = 4;
+  repeated string portForwards = 5;
 }
 
 // SSHServerState contains the latest state of the SSH server

client/server/server.go

@@ -1128,6 +1128,7 @@ func (s *Server) getSSHServerState() *proto.SSHServerState {
 			RemoteAddress: session.RemoteAddress,
 			Command:       session.Command,
 			JwtUsername:   session.JWTUsername,
+			PortForwards:  session.PortForwards,
 		})
 	}
 

client/ssh/client/client.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"io"
 	"net"
 	"os"
 	"path/filepath"
@@ -557,8 +556,9 @@ func (c *Client) handleLocalForward(localConn net.Conn, remoteAddr string) {
 
 	channel, err := c.client.Dial("tcp", remoteAddr)
 	if err != nil {
-		if strings.Contains(err.Error(), "administratively prohibited") {
-			_, _ = fmt.Fprintf(os.Stderr, "channel open failed: administratively prohibited: port forwarding is disabled\n")
+		var openErr *ssh.OpenChannelError
+		if errors.As(err, &openErr) && openErr.Reason == ssh.Prohibited {
+			_, _ = fmt.Fprintf(os.Stderr, "channel open failed: port forwarding is disabled\n")
 		} else {
 			log.Debugf("local port forwarding to %s failed: %v", remoteAddr, err)
 		}
@@ -570,15 +570,7 @@ func (c *Client) handleLocalForward(localConn net.Conn, remoteAddr string) {
 		}
 	}()
 
-	go func() {
-		if _, err := io.Copy(channel, localConn); err != nil {
-			log.Debugf("local forward copy error (local->remote): %v", err)
-		}
-	}()
-
-	if _, err := io.Copy(localConn, channel); err != nil {
-		log.Debugf("local forward copy error (remote->local): %v", err)
-	}
+	nbssh.BidirectionalCopy(localConn, channel)
 }
 
 // RemotePortForward sets up remote port forwarding, binding on remote and forwarding to localAddr
@@ -633,7 +625,7 @@ func (c *Client) sendTCPIPForwardRequest(req tcpipForwardMsg) error {
 		return fmt.Errorf("send tcpip-forward request: %w", err)
 	}
 	if !ok {
-		return fmt.Errorf("remote port forwarding denied by server (check if --allow-ssh-remote-port-forwarding is enabled)")
+		return fmt.Errorf("remote port forwarding denied by server")
 	}
 	return nil
 }
@@ -692,15 +684,7 @@ func (c *Client) handleRemoteForwardChannel(newChan ssh.NewChannel, localAddr st
 		}
 	}()
 
-	go func() {
-		if _, err := io.Copy(localConn, channel); err != nil {
-			log.Debugf("remote forward copy error (remote->local): %v", err)
-		}
-	}()
-
-	if _, err := io.Copy(channel, localConn); err != nil {
-		log.Debugf("remote forward copy error (local->remote): %v", err)
-	}
+	nbssh.BidirectionalCopy(localConn, channel)
 }
 
 // tcpipForwardMsg represents the structure for tcpip-forward requests

client/ssh/common.go

@@ -193,3 +193,52 @@ func buildAddressList(hostname string, remote net.Addr) []string {
 	}
 	return addresses
 }
+
+// BidirectionalCopy copies data bidirectionally between two io.ReadWriter connections.
+// It waits for both directions to complete before returning.
+// The caller is responsible for closing the connections.
+func BidirectionalCopy(rw1, rw2 io.ReadWriter) {
+	done := make(chan struct{}, 2)
+
+	go func() {
+		_, _ = io.Copy(rw2, rw1)
+		done <- struct{}{}
+	}()
+
+	go func() {
+		_, _ = io.Copy(rw1, rw2)
+		done <- struct{}{}
+	}()
+
+	<-done
+	<-done
+}
+
+// BidirectionalCopyWithContext copies data bidirectionally between two io.ReadWriteCloser connections.
+// It waits for both directions to complete or for context cancellation before returning.
+// Both connections are closed when the function returns.
+func BidirectionalCopyWithContext(ctx context.Context, conn1, conn2 io.ReadWriteCloser) {
+	done := make(chan struct{}, 2)
+
+	go func() {
+		_, _ = io.Copy(conn2, conn1)
+		done <- struct{}{}
+	}()
+
+	go func() {
+		_, _ = io.Copy(conn1, conn2)
+		done <- struct{}{}
+	}()
+
+	select {
+	case <-ctx.Done():
+	case <-done:
+		select {
+		case <-ctx.Done():
+		case <-done:
+		}
+	}
+
+	_ = conn1.Close()
+	_ = conn2.Close()
+}