harness-drone/vendor/code.google.com/p/go.crypto/ssh/tcpip.go
2015-09-29 18:21:17 -07:00

367 lines
9.3 KiB
Go

// Copyright 2011 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 (
"errors"
"fmt"
"io"
"math/rand"
"net"
"strconv"
"strings"
"sync"
"time"
)
// Listen requests the remote peer open a listening socket
// on addr. Incoming connections will be available by calling
// Accept on the returned net.Listener.
func (c *ClientConn) Listen(n, addr string) (net.Listener, error) {
laddr, err := net.ResolveTCPAddr(n, addr)
if err != nil {
return nil, err
}
return c.ListenTCP(laddr)
}
// Automatic port allocation is broken with OpenSSH before 6.0. See
// also https://bugzilla.mindrot.org/show_bug.cgi?id=2017. In
// particular, OpenSSH 5.9 sends a channelOpenMsg with port number 0,
// rather than the actual port number. This means you can never open
// two different listeners with auto allocated ports. We work around
// this by trying explicit ports until we succeed.
const openSSHPrefix = "OpenSSH_"
var portRandomizer = rand.New(rand.NewSource(time.Now().UnixNano()))
// isBrokenOpenSSHVersion returns true if the given version string
// specifies a version of OpenSSH that is known to have a bug in port
// forwarding.
func isBrokenOpenSSHVersion(versionStr string) bool {
i := strings.Index(versionStr, openSSHPrefix)
if i < 0 {
return false
}
i += len(openSSHPrefix)
j := i
for ; j < len(versionStr); j++ {
if versionStr[j] < '0' || versionStr[j] > '9' {
break
}
}
version, _ := strconv.Atoi(versionStr[i:j])
return version < 6
}
// autoPortListenWorkaround simulates automatic port allocation by
// trying random ports repeatedly.
func (c *ClientConn) autoPortListenWorkaround(laddr *net.TCPAddr) (net.Listener, error) {
var sshListener net.Listener
var err error
const tries = 10
for i := 0; i < tries; i++ {
addr := *laddr
addr.Port = 1024 + portRandomizer.Intn(60000)
sshListener, err = c.ListenTCP(&addr)
if err == nil {
laddr.Port = addr.Port
return sshListener, err
}
}
return nil, fmt.Errorf("ssh: listen on random port failed after %d tries: %v", tries, err)
}
// RFC 4254 7.1
type channelForwardMsg struct {
Message string
WantReply bool
raddr string
rport uint32
}
// ListenTCP requests the remote peer open a listening socket
// on laddr. Incoming connections will be available by calling
// Accept on the returned net.Listener.
func (c *ClientConn) ListenTCP(laddr *net.TCPAddr) (net.Listener, error) {
if laddr.Port == 0 && isBrokenOpenSSHVersion(c.serverVersion) {
return c.autoPortListenWorkaround(laddr)
}
m := channelForwardMsg{
"tcpip-forward",
true, // sendGlobalRequest waits for a reply
laddr.IP.String(),
uint32(laddr.Port),
}
// send message
resp, err := c.sendGlobalRequest(m)
if err != nil {
return nil, err
}
// If the original port was 0, then the remote side will
// supply a real port number in the response.
if laddr.Port == 0 {
port, _, ok := parseUint32(resp.Data)
if !ok {
return nil, errors.New("unable to parse response")
}
laddr.Port = int(port)
}
// Register this forward, using the port number we obtained.
ch := c.forwardList.add(*laddr)
return &tcpListener{laddr, c, ch}, nil
}
// forwardList stores a mapping between remote
// forward requests and the tcpListeners.
type forwardList struct {
sync.Mutex
entries []forwardEntry
}
// forwardEntry represents an established mapping of a laddr on a
// remote ssh server to a channel connected to a tcpListener.
type forwardEntry struct {
laddr net.TCPAddr
c chan forward
}
// forward represents an incoming forwarded tcpip connection. The
// arguments to add/remove/lookup should be address as specified in
// the original forward-request.
type forward struct {
c *clientChan // the ssh client channel underlying this forward
raddr *net.TCPAddr // the raddr of the incoming connection
}
func (l *forwardList) add(addr net.TCPAddr) chan forward {
l.Lock()
defer l.Unlock()
f := forwardEntry{
addr,
make(chan forward, 1),
}
l.entries = append(l.entries, f)
return f.c
}
// remove removes the forward entry, and the channel feeding its
// listener.
func (l *forwardList) remove(addr net.TCPAddr) {
l.Lock()
defer l.Unlock()
for i, f := range l.entries {
if addr.IP.Equal(f.laddr.IP) && addr.Port == f.laddr.Port {
l.entries = append(l.entries[:i], l.entries[i+1:]...)
close(f.c)
return
}
}
}
// closeAll closes and clears all forwards.
func (l *forwardList) closeAll() {
l.Lock()
defer l.Unlock()
for _, f := range l.entries {
close(f.c)
}
l.entries = nil
}
func (l *forwardList) lookup(addr net.TCPAddr) (chan forward, bool) {
l.Lock()
defer l.Unlock()
for _, f := range l.entries {
if addr.IP.Equal(f.laddr.IP) && addr.Port == f.laddr.Port {
return f.c, true
}
}
return nil, false
}
type tcpListener struct {
laddr *net.TCPAddr
conn *ClientConn
in <-chan forward
}
// Accept waits for and returns the next connection to the listener.
func (l *tcpListener) Accept() (net.Conn, error) {
s, ok := <-l.in
if !ok {
return nil, io.EOF
}
return &tcpChanConn{
tcpChan: &tcpChan{
clientChan: s.c,
Reader: s.c.stdout,
Writer: s.c.stdin,
},
laddr: l.laddr,
raddr: s.raddr,
}, nil
}
// Close closes the listener.
func (l *tcpListener) Close() error {
m := channelForwardMsg{
"cancel-tcpip-forward",
true,
l.laddr.IP.String(),
uint32(l.laddr.Port),
}
l.conn.forwardList.remove(*l.laddr)
if _, err := l.conn.sendGlobalRequest(m); err != nil {
return err
}
return nil
}
// Addr returns the listener's network address.
func (l *tcpListener) Addr() net.Addr {
return l.laddr
}
// Dial initiates a connection to the addr from the remote host.
// The resulting connection has a zero LocalAddr() and RemoteAddr().
func (c *ClientConn) Dial(n, addr string) (net.Conn, error) {
// Parse the address into host and numeric port.
host, portString, err := net.SplitHostPort(addr)
if err != nil {
return nil, err
}
port, err := strconv.ParseUint(portString, 10, 16)
if err != nil {
return nil, err
}
// Use a zero address for local and remote address.
zeroAddr := &net.TCPAddr{
IP: net.IPv4zero,
Port: 0,
}
ch, err := c.dial(net.IPv4zero.String(), 0, host, int(port))
if err != nil {
return nil, err
}
return &tcpChanConn{
tcpChan: ch,
laddr: zeroAddr,
raddr: zeroAddr,
}, nil
}
// DialTCP connects to the remote address raddr on the network net,
// which must be "tcp", "tcp4", or "tcp6". If laddr is not nil, it is used
// as the local address for the connection.
func (c *ClientConn) DialTCP(n string, laddr, raddr *net.TCPAddr) (net.Conn, error) {
if laddr == nil {
laddr = &net.TCPAddr{
IP: net.IPv4zero,
Port: 0,
}
}
ch, err := c.dial(laddr.IP.String(), laddr.Port, raddr.IP.String(), raddr.Port)
if err != nil {
return nil, err
}
return &tcpChanConn{
tcpChan: ch,
laddr: laddr,
raddr: raddr,
}, nil
}
// RFC 4254 7.2
type channelOpenDirectMsg struct {
ChanType string
PeersId uint32
PeersWindow uint32
MaxPacketSize uint32
raddr string
rport uint32
laddr string
lport uint32
}
// dial opens a direct-tcpip connection to the remote server. laddr and raddr are passed as
// strings and are expected to be resolvable at the remote end.
func (c *ClientConn) dial(laddr string, lport int, raddr string, rport int) (*tcpChan, error) {
ch := c.newChan(c.transport)
if err := c.transport.writePacket(marshal(msgChannelOpen, channelOpenDirectMsg{
ChanType: "direct-tcpip",
PeersId: ch.localId,
PeersWindow: channelWindowSize,
MaxPacketSize: channelMaxPacketSize,
raddr: raddr,
rport: uint32(rport),
laddr: laddr,
lport: uint32(lport),
})); err != nil {
c.chanList.remove(ch.localId)
return nil, err
}
if err := ch.waitForChannelOpenResponse(); err != nil {
c.chanList.remove(ch.localId)
return nil, fmt.Errorf("ssh: unable to open direct tcpip connection: %v", err)
}
return &tcpChan{
clientChan: ch,
Reader: ch.stdout,
Writer: ch.stdin,
}, nil
}
type tcpChan struct {
*clientChan // the backing channel
io.Reader
io.Writer
}
// tcpChanConn fulfills the net.Conn interface without
// the tcpChan having to hold laddr or raddr directly.
type tcpChanConn struct {
*tcpChan
laddr, raddr net.Addr
}
// LocalAddr returns the local network address.
func (t *tcpChanConn) LocalAddr() net.Addr {
return t.laddr
}
// RemoteAddr returns the remote network address.
func (t *tcpChanConn) RemoteAddr() net.Addr {
return t.raddr
}
// SetDeadline sets the read and write deadlines associated
// with the connection.
func (t *tcpChanConn) SetDeadline(deadline time.Time) error {
if err := t.SetReadDeadline(deadline); err != nil {
return err
}
return t.SetWriteDeadline(deadline)
}
// SetReadDeadline sets the read deadline.
// A zero value for t means Read will not time out.
// After the deadline, the error from Read will implement net.Error
// with Timeout() == true.
func (t *tcpChanConn) SetReadDeadline(deadline time.Time) error {
return errors.New("ssh: tcpChan: deadline not supported")
}
// SetWriteDeadline exists to satisfy the net.Conn interface
// but is not implemented by this type. It always returns an error.
func (t *tcpChanConn) SetWriteDeadline(deadline time.Time) error {
return errors.New("ssh: tcpChan: deadline not supported")
}