support "cancel-tcpip-forward" and "cancel-streamlocal-forward@openssh.com"

server.go

@@ -15,6 +15,7 @@ import (
 	"encoding/pem"
 	"fmt"
 	"github.com/mattn/go-shellwords"
+	"github.com/nwtgck/handy-sshd/sync_generics"
 	"github.com/pkg/sftp"
 	"golang.org/x/crypto/ssh"
 	"golang.org/x/exp/slog"
@@ -27,7 +28,8 @@ import (
 )
 
 type Server struct {
-	Logger *slog.Logger
+	Logger                *slog.Logger
+	bindAddressToListener sync_generics.Map[string, net.Listener]
 
 	// Permissions
 	AllowTcpipForward       bool
@@ -317,6 +319,10 @@ func (s *Server) HandleGlobalRequests(sshConn *ssh.ServerConn, reqs <-chan *ssh.
 			go func() {
 				s.handleTcpipForward(sshConn, req)
 			}()
+		case "cancel-tcpip-forward":
+			go func() {
+				s.cancelTcpipForward(req)
+			}()
 		case "streamlocal-forward@openssh.com":
 			if !s.AllowStreamlocalForward {
 				s.Logger.Info("streamlocal-forward not allowed")
@@ -326,8 +332,10 @@ func (s *Server) HandleGlobalRequests(sshConn *ssh.ServerConn, reqs <-chan *ssh.
 			go func() {
 				s.handleStreamlocalForward(sshConn, req)
 			}()
-		// TODO: support cancel-tcpip-forward
+		case "cancel-streamlocal-forward@openssh.com":
-		// TODO: support cancel-streamlocal-forward@openssh.com
+			go func() {
+				s.cancelStreamlocalForward(req)
+			}()
 		default:
 			// discard
 			if req.WantReply {
@@ -348,11 +356,13 @@ func (s *Server) handleTcpipForward(sshConn *ssh.ServerConn, req *ssh.Request) {
 		req.Reply(false, nil)
 		return
 	}
-	ln, err := net.Listen("tcp", net.JoinHostPort(msg.Addr, strconv.Itoa(int(msg.Port))))
+	address := net.JoinHostPort(msg.Addr, strconv.Itoa(int(msg.Port)))
+	ln, err := net.Listen("tcp", address)
 	if err != nil {
 		req.Reply(false, nil)
 		return
 	}
+	s.bindAddressToListener.Store(address, ln)
 	req.Reply(true, nil)
 	go func() {
 		sshConn.Wait()
@@ -404,6 +414,29 @@ func (s *Server) handleTcpipForward(sshConn *ssh.ServerConn, req *ssh.Request) {
 	}
 }
 
+// https://datatracker.ietf.org/doc/html/rfc4254#section-7.1
+func (s *Server) cancelTcpipForward(req *ssh.Request) {
+	var msg struct {
+		Addr string
+		Port uint32
+	}
+	if err := ssh.Unmarshal(req.Payload, &msg); err != nil {
+		req.Reply(false, nil)
+		return
+	}
+	address := net.JoinHostPort(msg.Addr, strconv.Itoa(int(msg.Port)))
+	ln, loaded := s.bindAddressToListener.LoadAndDelete(address)
+	if !loaded {
+		req.Reply(false, nil)
+		s.Logger.Info("failed to find listener", "address", address)
+	}
+	if err := ln.Close(); err != nil {
+		req.Reply(false, nil)
+		s.Logger.Info("failed to close", "err", err)
+	}
+	req.Reply(true, nil)
+}
+
 // client side: https://github.com/golang/crypto/blob/b4ddeeda5bc71549846db71ba23e83ecb26f36ed/ssh/streamlocal.go#L34
 func (s *Server) handleStreamlocalForward(sshConn *ssh.ServerConn, req *ssh.Request) {
 	// https://github.com/openssh/openssh-portable/blob/f9f18006678d2eac8b0c5a5dddf17ab7c50d1e9f/PROTOCOL#L272
@@ -419,6 +452,7 @@ func (s *Server) handleStreamlocalForward(sshConn *ssh.ServerConn, req *ssh.Requ
 		req.Reply(false, nil)
 		return
 	}
+	s.bindAddressToListener.Store(msg.SocketPath, ln)
 	req.Reply(true, nil)
 	go func() {
 		sshConn.Wait()
@@ -459,3 +493,25 @@ func (s *Server) handleStreamlocalForward(sshConn *ssh.ServerConn, req *ssh.Requ
 		}()
 	}
 }
+
+func (s *Server) cancelStreamlocalForward(req *ssh.Request) {
+	// https://github.com/openssh/openssh-portable/blob/f9f18006678d2eac8b0c5a5dddf17ab7c50d1e9f/PROTOCOL#L280
+	var msg struct {
+		SocketPath string
+	}
+	if err := ssh.Unmarshal(req.Payload, &msg); err != nil {
+		req.Reply(false, nil)
+		return
+	}
+	ln, loaded := s.bindAddressToListener.LoadAndDelete(msg.SocketPath)
+	if !loaded {
+		s.Logger.Info("failed to find listener", "address", msg.SocketPath)
+		req.Reply(false, nil)
+		return
+	}
+	if err := ln.Close(); err != nil {
+		req.Reply(false, nil)
+		s.Logger.Info("failed to close", "err", err)
+	}
+	req.Reply(true, nil)
+}

sync_generics/map.go

@@ -0,0 +1,62 @@
+package sync_generics
+
+import "sync"
+
+type Map[K any, V any] struct {
+	inner sync.Map
+}
+
+func (m *Map[K, V]) CompareAndDelete(key K, old V) (deleted bool) {
+	deleted = m.inner.CompareAndDelete(key, old)
+	return
+}
+
+func (m *Map[K, V]) CompareAndSwap(key K, old V, new V) bool {
+	return m.inner.CompareAndSwap(key, old, new)
+}
+
+func (m *Map[K, V]) Delete(key K) {
+	m.inner.Delete(key)
+}
+
+func (m *Map[K, V]) Load(key K) (value V, ok bool) {
+	_value, ok := m.inner.Load(key)
+	value = nilSafeTypeAssertion[V](_value)
+	return
+}
+
+func (m *Map[K, V]) LoadAndDelete(key K) (value V, loaded bool) {
+	_value, loaded := m.inner.LoadAndDelete(key)
+	value = nilSafeTypeAssertion[V](_value)
+	return
+}
+
+func (m *Map[K, V]) LoadOrStore(key K, value V) (actual V, loaded bool) {
+	_actual, loaded := m.inner.LoadOrStore(key, value)
+	actual = nilSafeTypeAssertion[V](_actual)
+	return
+}
+
+func (m *Map[K, V]) Range(f func(key K, value V) bool) {
+	m.inner.Range(func(key, value any) bool {
+		return f(nilSafeTypeAssertion[K](key), nilSafeTypeAssertion[V](value))
+	})
+}
+
+func (m *Map[K, V]) Store(key K, value V) {
+	m.inner.Store(key, value)
+}
+
+func (m *Map[K, V]) Swap(key K, value V) (previous V, loaded bool) {
+	_previous, loaded := m.inner.Swap(key, value)
+	previous = nilSafeTypeAssertion[V](_previous)
+	return
+}
+
+func nilSafeTypeAssertion[T any](value any) T {
+	var zero T
+	if value == nil {
+		return zero
+	}
+	return value.(T)
+}