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// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package ssh
import (
// OpenChannelError is returned if the other side rejects an
// OpenChannel request.
type OpenChannelError struct {
Reason RejectionReason
Message string
func (e *OpenChannelError) Error() string {
return fmt.Sprintf("ssh: rejected: %s (%s)", e.Reason, e.Message)
// ConnMetadata holds metadata for the connection.
type ConnMetadata interface {
// User returns the user ID for this connection.
User() string
// SessionID returns the session hash, also denoted by H.
SessionID() []byte
// ClientVersion returns the client's version string as hashed
// into the session ID.
ClientVersion() []byte
// ServerVersion returns the server's version string as hashed
// into the session ID.
ServerVersion() []byte
// RemoteAddr returns the remote address for this connection.
RemoteAddr() net.Addr
// LocalAddr returns the local address for this connection.
LocalAddr() net.Addr
// Conn represents an SSH connection for both server and client roles.
// Conn is the basis for implementing an application layer, such
// as ClientConn, which implements the traditional shell access for
// clients.
type Conn interface {
// SendRequest sends a global request, and returns the
// reply. If wantReply is true, it returns the response status
// and payload. See also RFC 4254, section 4.
SendRequest(name string, wantReply bool, payload []byte) (bool, []byte, error)
// OpenChannel tries to open an channel. If the request is
// rejected, it returns *OpenChannelError. On success it returns
// the SSH Channel and a Go channel for incoming, out-of-band
// requests. The Go channel must be serviced, or the
// connection will hang.
OpenChannel(name string, data []byte) (Channel, <-chan *Request, error)
// Close closes the underlying network connection
Close() error
// Wait blocks until the connection has shut down, and returns the
// error causing the shutdown.
Wait() error
// TODO(hanwen): consider exposing:
// RequestKeyChange
// Disconnect
// DiscardRequests consumes and rejects all requests from the
// passed-in channel.
func DiscardRequests(in <-chan *Request) {
for req := range in {
if req.WantReply {
req.Reply(false, nil)
// A connection represents an incoming connection.
type connection struct {
transport *handshakeTransport
// The connection protocol.
func (c *connection) Close() error {
return c.sshConn.conn.Close()
// sshconn provides net.Conn metadata, but disallows direct reads and
// writes.
type sshConn struct {
conn net.Conn
user string
sessionID []byte
clientVersion []byte
serverVersion []byte
func dup(src []byte) []byte {
dst := make([]byte, len(src))
copy(dst, src)
return dst
func (c *sshConn) User() string {
return c.user
func (c *sshConn) RemoteAddr() net.Addr {
return c.conn.RemoteAddr()
func (c *sshConn) Close() error {
return c.conn.Close()
func (c *sshConn) LocalAddr() net.Addr {
return c.conn.LocalAddr()
func (c *sshConn) SessionID() []byte {
return dup(c.sessionID)
func (c *sshConn) ClientVersion() []byte {
return dup(c.clientVersion)
func (c *sshConn) ServerVersion() []byte {
return dup(c.serverVersion)