--- /dev/null
+// 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 (
+ "encoding/binary"
+ "fmt"
+ "io"
+ "log"
+ "sync"
+ "sync/atomic"
+)
+
+// debugMux, if set, causes messages in the connection protocol to be
+// logged.
+const debugMux = false
+
+// chanList is a thread safe channel list.
+type chanList struct {
+ // protects concurrent access to chans
+ sync.Mutex
+
+ // chans are indexed by the local id of the channel, which the
+ // other side should send in the PeersId field.
+ chans []*channel
+
+ // This is a debugging aid: it offsets all IDs by this
+ // amount. This helps distinguish otherwise identical
+ // server/client muxes
+ offset uint32
+}
+
+// Assigns a channel ID to the given channel.
+func (c *chanList) add(ch *channel) uint32 {
+ c.Lock()
+ defer c.Unlock()
+ for i := range c.chans {
+ if c.chans[i] == nil {
+ c.chans[i] = ch
+ return uint32(i) + c.offset
+ }
+ }
+ c.chans = append(c.chans, ch)
+ return uint32(len(c.chans)-1) + c.offset
+}
+
+// getChan returns the channel for the given ID.
+func (c *chanList) getChan(id uint32) *channel {
+ id -= c.offset
+
+ c.Lock()
+ defer c.Unlock()
+ if id < uint32(len(c.chans)) {
+ return c.chans[id]
+ }
+ return nil
+}
+
+func (c *chanList) remove(id uint32) {
+ id -= c.offset
+ c.Lock()
+ if id < uint32(len(c.chans)) {
+ c.chans[id] = nil
+ }
+ c.Unlock()
+}
+
+// dropAll forgets all channels it knows, returning them in a slice.
+func (c *chanList) dropAll() []*channel {
+ c.Lock()
+ defer c.Unlock()
+ var r []*channel
+
+ for _, ch := range c.chans {
+ if ch == nil {
+ continue
+ }
+ r = append(r, ch)
+ }
+ c.chans = nil
+ return r
+}
+
+// mux represents the state for the SSH connection protocol, which
+// multiplexes many channels onto a single packet transport.
+type mux struct {
+ conn packetConn
+ chanList chanList
+
+ incomingChannels chan NewChannel
+
+ globalSentMu sync.Mutex
+ globalResponses chan interface{}
+ incomingRequests chan *Request
+
+ errCond *sync.Cond
+ err error
+}
+
+// When debugging, each new chanList instantiation has a different
+// offset.
+var globalOff uint32
+
+func (m *mux) Wait() error {
+ m.errCond.L.Lock()
+ defer m.errCond.L.Unlock()
+ for m.err == nil {
+ m.errCond.Wait()
+ }
+ return m.err
+}
+
+// newMux returns a mux that runs over the given connection.
+func newMux(p packetConn) *mux {
+ m := &mux{
+ conn: p,
+ incomingChannels: make(chan NewChannel, chanSize),
+ globalResponses: make(chan interface{}, 1),
+ incomingRequests: make(chan *Request, chanSize),
+ errCond: newCond(),
+ }
+ if debugMux {
+ m.chanList.offset = atomic.AddUint32(&globalOff, 1)
+ }
+
+ go m.loop()
+ return m
+}
+
+func (m *mux) sendMessage(msg interface{}) error {
+ p := Marshal(msg)
+ if debugMux {
+ log.Printf("send global(%d): %#v", m.chanList.offset, msg)
+ }
+ return m.conn.writePacket(p)
+}
+
+func (m *mux) SendRequest(name string, wantReply bool, payload []byte) (bool, []byte, error) {
+ if wantReply {
+ m.globalSentMu.Lock()
+ defer m.globalSentMu.Unlock()
+ }
+
+ if err := m.sendMessage(globalRequestMsg{
+ Type: name,
+ WantReply: wantReply,
+ Data: payload,
+ }); err != nil {
+ return false, nil, err
+ }
+
+ if !wantReply {
+ return false, nil, nil
+ }
+
+ msg, ok := <-m.globalResponses
+ if !ok {
+ return false, nil, io.EOF
+ }
+ switch msg := msg.(type) {
+ case *globalRequestFailureMsg:
+ return false, msg.Data, nil
+ case *globalRequestSuccessMsg:
+ return true, msg.Data, nil
+ default:
+ return false, nil, fmt.Errorf("ssh: unexpected response to request: %#v", msg)
+ }
+}
+
+// ackRequest must be called after processing a global request that
+// has WantReply set.
+func (m *mux) ackRequest(ok bool, data []byte) error {
+ if ok {
+ return m.sendMessage(globalRequestSuccessMsg{Data: data})
+ }
+ return m.sendMessage(globalRequestFailureMsg{Data: data})
+}
+
+func (m *mux) Close() error {
+ return m.conn.Close()
+}
+
+// loop runs the connection machine. It will process packets until an
+// error is encountered. To synchronize on loop exit, use mux.Wait.
+func (m *mux) loop() {
+ var err error
+ for err == nil {
+ err = m.onePacket()
+ }
+
+ for _, ch := range m.chanList.dropAll() {
+ ch.close()
+ }
+
+ close(m.incomingChannels)
+ close(m.incomingRequests)
+ close(m.globalResponses)
+
+ m.conn.Close()
+
+ m.errCond.L.Lock()
+ m.err = err
+ m.errCond.Broadcast()
+ m.errCond.L.Unlock()
+
+ if debugMux {
+ log.Println("loop exit", err)
+ }
+}
+
+// onePacket reads and processes one packet.
+func (m *mux) onePacket() error {
+ packet, err := m.conn.readPacket()
+ if err != nil {
+ return err
+ }
+
+ if debugMux {
+ if packet[0] == msgChannelData || packet[0] == msgChannelExtendedData {
+ log.Printf("decoding(%d): data packet - %d bytes", m.chanList.offset, len(packet))
+ } else {
+ p, _ := decode(packet)
+ log.Printf("decoding(%d): %d %#v - %d bytes", m.chanList.offset, packet[0], p, len(packet))
+ }
+ }
+
+ switch packet[0] {
+ case msgChannelOpen:
+ return m.handleChannelOpen(packet)
+ case msgGlobalRequest, msgRequestSuccess, msgRequestFailure:
+ return m.handleGlobalPacket(packet)
+ }
+
+ // assume a channel packet.
+ if len(packet) < 5 {
+ return parseError(packet[0])
+ }
+ id := binary.BigEndian.Uint32(packet[1:])
+ ch := m.chanList.getChan(id)
+ if ch == nil {
+ return fmt.Errorf("ssh: invalid channel %d", id)
+ }
+
+ return ch.handlePacket(packet)
+}
+
+func (m *mux) handleGlobalPacket(packet []byte) error {
+ msg, err := decode(packet)
+ if err != nil {
+ return err
+ }
+
+ switch msg := msg.(type) {
+ case *globalRequestMsg:
+ m.incomingRequests <- &Request{
+ Type: msg.Type,
+ WantReply: msg.WantReply,
+ Payload: msg.Data,
+ mux: m,
+ }
+ case *globalRequestSuccessMsg, *globalRequestFailureMsg:
+ m.globalResponses <- msg
+ default:
+ panic(fmt.Sprintf("not a global message %#v", msg))
+ }
+
+ return nil
+}
+
+// handleChannelOpen schedules a channel to be Accept()ed.
+func (m *mux) handleChannelOpen(packet []byte) error {
+ var msg channelOpenMsg
+ if err := Unmarshal(packet, &msg); err != nil {
+ return err
+ }
+
+ if msg.MaxPacketSize < minPacketLength || msg.MaxPacketSize > 1<<31 {
+ failMsg := channelOpenFailureMsg{
+ PeersId: msg.PeersId,
+ Reason: ConnectionFailed,
+ Message: "invalid request",
+ Language: "en_US.UTF-8",
+ }
+ return m.sendMessage(failMsg)
+ }
+
+ c := m.newChannel(msg.ChanType, channelInbound, msg.TypeSpecificData)
+ c.remoteId = msg.PeersId
+ c.maxRemotePayload = msg.MaxPacketSize
+ c.remoteWin.add(msg.PeersWindow)
+ m.incomingChannels <- c
+ return nil
+}
+
+func (m *mux) OpenChannel(chanType string, extra []byte) (Channel, <-chan *Request, error) {
+ ch, err := m.openChannel(chanType, extra)
+ if err != nil {
+ return nil, nil, err
+ }
+
+ return ch, ch.incomingRequests, nil
+}
+
+func (m *mux) openChannel(chanType string, extra []byte) (*channel, error) {
+ ch := m.newChannel(chanType, channelOutbound, extra)
+
+ ch.maxIncomingPayload = channelMaxPacket
+
+ open := channelOpenMsg{
+ ChanType: chanType,
+ PeersWindow: ch.myWindow,
+ MaxPacketSize: ch.maxIncomingPayload,
+ TypeSpecificData: extra,
+ PeersId: ch.localId,
+ }
+ if err := m.sendMessage(open); err != nil {
+ return nil, err
+ }
+
+ switch msg := (<-ch.msg).(type) {
+ case *channelOpenConfirmMsg:
+ return ch, nil
+ case *channelOpenFailureMsg:
+ return nil, &OpenChannelError{msg.Reason, msg.Message}
+ default:
+ return nil, fmt.Errorf("ssh: unexpected packet in response to channel open: %T", msg)
+ }
+}
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