support connection sharing #29 #43

ControlMaster
ControlPath
ControlPersist

tssh/args.go

@@ -74,6 +74,7 @@ type sshArgs struct {
 	Relay          bool        `arg:"--relay" help:"force trzsz run as a relay on the jump server"`
 	Debug          bool        `arg:"--debug" help:"verbose mode for debugging, same as ssh's -vvv"`
 	EncSecret      bool        `arg:"--enc-secret" help:"encode secret for configuration(~/.ssh/password)"`
+	originalDest   string
 }
 
 func (sshArgs) Description() string {

tssh/control.go

@@ -0,0 +1,325 @@
+// Copyright 2022 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 tssh
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"io"
+	"net"
+	"sync"
+	_ "unsafe"
+
+	"golang.org/x/crypto/ssh"
+)
+
+//go:linkname newMux golang.org/x/crypto/ssh.newMux
+func newMux(p packetConn) *mux
+
+//go:linkname muxSendRequest golang.org/x/crypto/ssh.(*mux).SendRequest
+func muxSendRequest(m *mux, name string, wantReply bool, payload []byte) (bool, []byte, error)
+
+//go:linkname muxOpenChannel golang.org/x/crypto/ssh.(*mux).OpenChannel
+func muxOpenChannel(m *mux, chanType string, extra []byte) (ssh.Channel, <-chan *ssh.Request, error)
+
+//go:linkname muxWait golang.org/x/crypto/ssh.(*mux).Wait
+func muxWait(m *mux) error
+
+// packetConn represents a transport that implements packet based
+// operations.
+type packetConn interface {
+	// Encrypt and send a packet of data to the remote peer.
+	writePacket(packet []byte) error
+
+	// Read a packet from the connection. The read is blocking,
+	// i.e. if error is nil, then the returned byte slice is
+	// always non-empty.
+	readPacket() ([]byte, error)
+
+	// Close closes the write-side of the connection.
+	Close() error
+}
+
+// channel is an implementation of the Channel interface that works
+// with the mux class.
+type channel struct{} // nolint:all
+
+// chanList is a thread safe channel list.
+type chanList struct { // nolint:all
+	// 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
+}
+
+// mux represents the state for the SSH connection protocol, which
+// multiplexes many channels onto a single packet transport.
+type mux struct {
+	conn     packetConn // nolint:all
+	chanList chanList   // nolint:all
+
+	incomingChannels chan ssh.NewChannel
+
+	globalSentMu     sync.Mutex       // nolint:all
+	globalResponses  chan interface{} // nolint:all
+	incomingRequests chan *ssh.Request
+
+	errCond *sync.Cond // nolint:all
+	err     error      // nolint:all
+}
+
+type connTransport interface {
+	packetConn
+	getSessionID() []byte
+	waitSession() error
+}
+
+// A connection represents an incoming connection.
+type connection struct {
+	transport connTransport
+	sshConn
+
+	// The connection protocol.
+	*mux
+}
+
+func (c *connection) Close() error {
+	return c.sshConn.conn.Close()
+}
+
+func (c *connection) SendRequest(name string, wantReply bool, payload []byte) (bool, []byte, error) {
+	return muxSendRequest(c.mux, name, wantReply, payload)
+}
+
+func (c *connection) OpenChannel(chanType string, extra []byte) (ssh.Channel, <-chan *ssh.Request, error) {
+	return muxOpenChannel(c.mux, chanType, extra)
+}
+
+func (c *connection) Wait() error {
+	return muxWait(c.mux)
+}
+
+// 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)
+}
+
+// NewControlClientConn establishes an SSH connection over an OpenSSH
+// ControlMaster socket c in proxy mode. The Request and NewChannel channels
+// must be serviced or the connection will hang.
+func NewControlClientConn(c net.Conn) (ssh.Conn, <-chan ssh.NewChannel, <-chan *ssh.Request, error) {
+	conn := &connection{
+		sshConn: sshConn{conn: c},
+	}
+	var err error
+	if conn.transport, err = handshakeControlProxy(c); err != nil {
+		return nil, nil, nil, fmt.Errorf("ssh: control proxy handshake failed; %v", err)
+	}
+	conn.mux = newMux(conn.transport)
+	return conn, conn.mux.incomingChannels, conn.mux.incomingRequests, nil
+}
+
+const (
+	muxMsgHello = 0x00000001
+	muxCliProxy = 0x1000000f
+	muxSvrProxy = 0x8000000f
+	muxSFailure = 0x80000003
+)
+
+// handshakeControlProxy attempts to establish a transport connection with an
+// OpenSSH ControlMaster socket in proxy mode. For details see:
+// https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.mux
+func handshakeControlProxy(rw io.ReadWriteCloser) (connTransport, error) {
+	b := &controlBuffer{}
+	b.writeUint32(muxMsgHello)
+	b.writeUint32(4) // Protocol Version
+	if _, err := rw.Write(b.lengthPrefixedBytes()); err != nil {
+		return nil, fmt.Errorf("mux hello write failed: %v", err)
+	}
+
+	b.Reset()
+	b.writeUint32(muxCliProxy)
+	b.writeUint32(0) // Request ID
+	if _, err := rw.Write(b.lengthPrefixedBytes()); err != nil {
+		return nil, fmt.Errorf("mux client proxy write failed: %v", err)
+	}
+
+	r := controlReader{rw}
+	m, err := r.next()
+	if err != nil {
+		return nil, fmt.Errorf("mux hello read failed: %v", err)
+	}
+	if m.messageType != muxMsgHello {
+		return nil, fmt.Errorf("mux reply not hello")
+	}
+	if v, err := m.readUint32(); err != nil || v != 4 {
+		return nil, fmt.Errorf("mux reply hello has bad protocol version")
+	}
+	m, err = r.next()
+	if err != nil {
+		return nil, fmt.Errorf("error reading mux server proxy: %v", err)
+	}
+	if m.messageType != muxSvrProxy {
+		return nil, fmt.Errorf("expected server proxy response got %d", m.messageType)
+	}
+	return &controlProxyTransport{rw}, nil
+}
+
+// controlProxyTransport implements the connTransport interface for
+// ControlMaster connections. Each controlMessage has zero length padding and
+// no MAC.
+type controlProxyTransport struct {
+	rw io.ReadWriteCloser
+}
+
+func (p *controlProxyTransport) Close() error {
+	return p.rw.Close()
+}
+
+func (p *controlProxyTransport) getSessionID() []byte {
+	return nil
+}
+
+func (p *controlProxyTransport) readPacket() ([]byte, error) {
+	var l uint32
+	err := binary.Read(p.rw, binary.BigEndian, &l)
+	if err == nil {
+		buf := &bytes.Buffer{}
+		_, err = io.CopyN(buf, p.rw, int64(l))
+		if err == nil {
+			// Discard the padding byte.
+			_, _ = buf.ReadByte()
+			return buf.Bytes(), nil
+		}
+	}
+	return nil, err
+}
+
+func (p *controlProxyTransport) writePacket(controlMessage []byte) error {
+	l := uint32(len(controlMessage)) + 1
+	b := &bytes.Buffer{}
+	_ = binary.Write(b, binary.BigEndian, &l) // controlMessage Length.
+	b.WriteByte(0)                            // Padding Length.
+	b.Write(controlMessage)
+	_, err := p.rw.Write(b.Bytes())
+	return err
+}
+
+func (p *controlProxyTransport) waitSession() error {
+	return nil
+}
+
+type controlBuffer struct {
+	bytes.Buffer
+}
+
+func (b *controlBuffer) writeUint32(i uint32) {
+	_ = binary.Write(b, binary.BigEndian, i)
+}
+
+func (b *controlBuffer) lengthPrefixedBytes() []byte {
+	b2 := &bytes.Buffer{}
+	_ = binary.Write(b2, binary.BigEndian, uint32(b.Len()))
+	b2.Write(b.Bytes())
+	return b2.Bytes()
+}
+
+type controlMessage struct {
+	body        bytes.Buffer
+	messageType uint32
+}
+
+func (p controlMessage) readUint32() (uint32, error) {
+	var u uint32
+	err := binary.Read(&p.body, binary.BigEndian, &u)
+	return u, err
+}
+
+func (p controlMessage) readString() (string, error) {
+	var l uint32
+	err := binary.Read(&p.body, binary.BigEndian, &l)
+	if err != nil {
+		return "", fmt.Errorf("error reading string length: %v", err)
+	}
+	b := p.body.Next(int(l))
+	if len(b) != int(l) {
+		return string(b), fmt.Errorf("EOF on string read")
+	}
+	return string(b), nil
+}
+
+type controlReader struct {
+	r io.Reader
+}
+
+func (r controlReader) next() (*controlMessage, error) {
+	p := &controlMessage{}
+	var len uint32
+	err := binary.Read(r.r, binary.BigEndian, &len)
+	if err != nil {
+		return nil, fmt.Errorf("error reading message length: %v", err)
+	}
+	_, err = io.CopyN(&p.body, r.r, int64(len))
+	if err != nil {
+		return nil, fmt.Errorf("error reading message payload: %v", err)
+	}
+	err = binary.Read(&p.body, binary.BigEndian, &p.messageType)
+	if err != nil {
+		return nil, fmt.Errorf("error reading message type: %v", err)
+	}
+	if p.messageType == muxSFailure {
+		reason, _ := p.readString()
+		return nil, fmt.Errorf("server failure: '%s'", reason)
+	}
+	return p, nil
+}