func (sshClient *sshClient) handleNewDirectTcpipChannel(newChannel ssh.NewChannel) {
// http://tools.ietf.org/html/rfc4254#section-7.2
var directTcpipExtraData struct {
HostToConnect string
PortToConnect uint32
OriginatorIPAddress string
OriginatorPort uint32
}
err := ssh.Unmarshal(newChannel.ExtraData(), &directTcpipExtraData)
if err != nil {
sshClient.rejectNewChannel(newChannel, ssh.Prohibited, "invalid extra data")
return
}
targetAddr := fmt.Sprintf("%s:%d",
directTcpipExtraData.HostToConnect,
directTcpipExtraData.PortToConnect)
log.WithContextFields(LogFields{"target": targetAddr}).Debug("dialing")
// TODO: port forward dial timeout
// TODO: report ssh.ResourceShortage when appropriate
// TODO: IPv6 support
fwdConn, err := net.Dial("tcp4", targetAddr)
if err != nil {
sshClient.rejectNewChannel(newChannel, ssh.ConnectionFailed, err.Error())
return
}
defer fwdConn.Close()
fwdChannel, requests, err := newChannel.Accept()
if err != nil {
log.WithContextFields(LogFields{"error": err}).Warning("accept new channel failed")
return
}
sshClient.Lock()
sshClient.portForwardCount += 1
sshClient.concurrentPortForwardCount += 1
if sshClient.concurrentPortForwardCount > sshClient.peakConcurrentPortForwardCount {
sshClient.peakConcurrentPortForwardCount = sshClient.concurrentPortForwardCount
}
sshClient.Unlock()
log.WithContextFields(LogFields{"target": targetAddr}).Debug("relaying")
go ssh.DiscardRequests(requests)
defer fwdChannel.Close()
// When idle port forward traffic rules are in place, wrap fwdConn
// in an IdleTimeoutConn configured to reset idle on writes as well
// as read. This ensures the port forward idle timeout only happens
// when both upstream and downstream directions are are idle.
if sshClient.trafficRules.IdlePortForwardTimeoutMilliseconds > 0 {
fwdConn = psiphon.NewIdleTimeoutConn(
fwdConn,
time.Duration(sshClient.trafficRules.IdlePortForwardTimeoutMilliseconds)*time.Millisecond,
true)
}
// relay channel to forwarded connection
// TODO: relay errors to fwdChannel.Stderr()?
var bytesUp, bytesDown int64
relayWaitGroup := new(sync.WaitGroup)
relayWaitGroup.Add(1)
go func() {
defer relayWaitGroup.Done()
var err error
bytesUp, err = copyWithThrottle(
fwdConn, fwdChannel, sshClient.trafficRules.ThrottleUpstreamSleepMilliseconds)
if err != nil {
log.WithContextFields(LogFields{"error": err}).Warning("upstream relay failed")
}
}()
bytesDown, err = copyWithThrottle(
fwdChannel, fwdConn, sshClient.trafficRules.ThrottleDownstreamSleepMilliseconds)
if err != nil {
log.WithContextFields(LogFields{"error": err}).Warning("downstream relay failed")
}
fwdChannel.CloseWrite()
relayWaitGroup.Wait()
sshClient.Lock()
sshClient.concurrentPortForwardCount -= 1
sshClient.bytesUp += bytesUp
sshClient.bytesDown += bytesDown
sshClient.Unlock()
log.WithContextFields(LogFields{"target": targetAddr}).Debug("exiting")
}
func (sshServer *sshServer) handleClient(tcpConn *net.TCPConn) {
sshClient := &sshClient{
sshServer: sshServer,
startTime: time.Now(),
geoIPData: GeoIPLookup(psiphon.IPAddressFromAddr(tcpConn.RemoteAddr())),
}
sshClient.trafficRules = sshServer.config.GetTrafficRules(sshClient.geoIPData.Country)
// Wrap the base TCP connection with an IdleTimeoutConn which will terminate
// the connection if no data is received before the deadline. This timeout is
// in effect for the entire duration of the SSH connection. Clients must actively
// use the connection or send SSH keep alive requests to keep the connection
// active.
conn := psiphon.NewIdleTimeoutConn(tcpConn, SSH_CONNECTION_READ_DEADLINE, false)
// Run the initial [obfuscated] SSH handshake in a goroutine so we can both
// respect shutdownBroadcast and implement a specific handshake timeout.
// The timeout is to reclaim network resources in case the handshake takes
// too long.
type sshNewServerConnResult struct {
conn net.Conn
sshConn *ssh.ServerConn
channels <-chan ssh.NewChannel
requests <-chan *ssh.Request
err error
}
resultChannel := make(chan *sshNewServerConnResult, 2)
if SSH_HANDSHAKE_TIMEOUT > 0 {
time.AfterFunc(time.Duration(SSH_HANDSHAKE_TIMEOUT), func() {
resultChannel <- &sshNewServerConnResult{err: errors.New("ssh handshake timeout")}
})
}
go func() {
result := &sshNewServerConnResult{}
if sshServer.useObfuscation {
result.conn, result.err = psiphon.NewObfuscatedSshConn(
psiphon.OBFUSCATION_CONN_MODE_SERVER, conn, sshServer.config.ObfuscatedSSHKey)
} else {
result.conn = conn
}
if result.err == nil {
sshServerConfig := &ssh.ServerConfig{
PasswordCallback: sshClient.passwordCallback,
AuthLogCallback: sshClient.authLogCallback,
ServerVersion: sshServer.config.SSHServerVersion,
}
sshServerConfig.AddHostKey(sshServer.sshHostKey)
result.sshConn, result.channels, result.requests, result.err =
ssh.NewServerConn(result.conn, sshServerConfig)
}
resultChannel <- result
}()
var result *sshNewServerConnResult
select {
case result = <-resultChannel:
case <-sshServer.shutdownBroadcast:
// Close() will interrupt an ongoing handshake
// TODO: wait for goroutine to exit before returning?
conn.Close()
return
}
if result.err != nil {
conn.Close()
log.WithContextFields(LogFields{"error": result.err}).Warning("handshake failed")
return
}
sshClient.Lock()
sshClient.sshConn = result.sshConn
sshClient.Unlock()
clientID, ok := sshServer.registerClient(sshClient)
if !ok {
conn.Close()
log.WithContext().Warning("register failed")
return
}
defer sshServer.unregisterClient(clientID)
go ssh.DiscardRequests(result.requests)
sshClient.handleChannels(result.channels)
}