Upgrading dependencies to include logrus.

vendor/golang.org/x/crypto/ssh/handshake.go

@@ -0,0 +1,646 @@
+// 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 (
+	"crypto/rand"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"sync"
+)
+
+// debugHandshake, if set, prints messages sent and received.  Key
+// exchange messages are printed as if DH were used, so the debug
+// messages are wrong when using ECDH.
+const debugHandshake = false
+
+// chanSize sets the amount of buffering SSH connections. This is
+// primarily for testing: setting chanSize=0 uncovers deadlocks more
+// quickly.
+const chanSize = 16
+
+// keyingTransport is a packet based transport that supports key
+// changes. It need not be thread-safe. It should pass through
+// msgNewKeys in both directions.
+type keyingTransport interface {
+	packetConn
+
+	// prepareKeyChange sets up a key change. The key change for a
+	// direction will be effected if a msgNewKeys message is sent
+	// or received.
+	prepareKeyChange(*algorithms, *kexResult) error
+}
+
+// handshakeTransport implements rekeying on top of a keyingTransport
+// and offers a thread-safe writePacket() interface.
+type handshakeTransport struct {
+	conn   keyingTransport
+	config *Config
+
+	serverVersion []byte
+	clientVersion []byte
+
+	// hostKeys is non-empty if we are the server. In that case,
+	// it contains all host keys that can be used to sign the
+	// connection.
+	hostKeys []Signer
+
+	// hostKeyAlgorithms is non-empty if we are the client. In that case,
+	// we accept these key types from the server as host key.
+	hostKeyAlgorithms []string
+
+	// On read error, incoming is closed, and readError is set.
+	incoming  chan []byte
+	readError error
+
+	mu             sync.Mutex
+	writeError     error
+	sentInitPacket []byte
+	sentInitMsg    *kexInitMsg
+	pendingPackets [][]byte // Used when a key exchange is in progress.
+
+	// If the read loop wants to schedule a kex, it pings this
+	// channel, and the write loop will send out a kex
+	// message.
+	requestKex chan struct{}
+
+	// If the other side requests or confirms a kex, its kexInit
+	// packet is sent here for the write loop to find it.
+	startKex chan *pendingKex
+
+	// data for host key checking
+	hostKeyCallback HostKeyCallback
+	dialAddress     string
+	remoteAddr      net.Addr
+
+	// bannerCallback is non-empty if we are the client and it has been set in
+	// ClientConfig. In that case it is called during the user authentication
+	// dance to handle a custom server's message.
+	bannerCallback BannerCallback
+
+	// Algorithms agreed in the last key exchange.
+	algorithms *algorithms
+
+	readPacketsLeft uint32
+	readBytesLeft   int64
+
+	writePacketsLeft uint32
+	writeBytesLeft   int64
+
+	// The session ID or nil if first kex did not complete yet.
+	sessionID []byte
+}
+
+type pendingKex struct {
+	otherInit []byte
+	done      chan error
+}
+
+func newHandshakeTransport(conn keyingTransport, config *Config, clientVersion, serverVersion []byte) *handshakeTransport {
+	t := &handshakeTransport{
+		conn:          conn,
+		serverVersion: serverVersion,
+		clientVersion: clientVersion,
+		incoming:      make(chan []byte, chanSize),
+		requestKex:    make(chan struct{}, 1),
+		startKex:      make(chan *pendingKex, 1),
+
+		config: config,
+	}
+	t.resetReadThresholds()
+	t.resetWriteThresholds()
+
+	// We always start with a mandatory key exchange.
+	t.requestKex <- struct{}{}
+	return t
+}
+
+func newClientTransport(conn keyingTransport, clientVersion, serverVersion []byte, config *ClientConfig, dialAddr string, addr net.Addr) *handshakeTransport {
+	t := newHandshakeTransport(conn, &config.Config, clientVersion, serverVersion)
+	t.dialAddress = dialAddr
+	t.remoteAddr = addr
+	t.hostKeyCallback = config.HostKeyCallback
+	t.bannerCallback = config.BannerCallback
+	if config.HostKeyAlgorithms != nil {
+		t.hostKeyAlgorithms = config.HostKeyAlgorithms
+	} else {
+		t.hostKeyAlgorithms = supportedHostKeyAlgos
+	}
+	go t.readLoop()
+	go t.kexLoop()
+	return t
+}
+
+func newServerTransport(conn keyingTransport, clientVersion, serverVersion []byte, config *ServerConfig) *handshakeTransport {
+	t := newHandshakeTransport(conn, &config.Config, clientVersion, serverVersion)
+	t.hostKeys = config.hostKeys
+	go t.readLoop()
+	go t.kexLoop()
+	return t
+}
+
+func (t *handshakeTransport) getSessionID() []byte {
+	return t.sessionID
+}
+
+// waitSession waits for the session to be established. This should be
+// the first thing to call after instantiating handshakeTransport.
+func (t *handshakeTransport) waitSession() error {
+	p, err := t.readPacket()
+	if err != nil {
+		return err
+	}
+	if p[0] != msgNewKeys {
+		return fmt.Errorf("ssh: first packet should be msgNewKeys")
+	}
+
+	return nil
+}
+
+func (t *handshakeTransport) id() string {
+	if len(t.hostKeys) > 0 {
+		return "server"
+	}
+	return "client"
+}
+
+func (t *handshakeTransport) printPacket(p []byte, write bool) {
+	action := "got"
+	if write {
+		action = "sent"
+	}
+
+	if p[0] == msgChannelData || p[0] == msgChannelExtendedData {
+		log.Printf("%s %s data (packet %d bytes)", t.id(), action, len(p))
+	} else {
+		msg, err := decode(p)
+		log.Printf("%s %s %T %v (%v)", t.id(), action, msg, msg, err)
+	}
+}
+
+func (t *handshakeTransport) readPacket() ([]byte, error) {
+	p, ok := <-t.incoming
+	if !ok {
+		return nil, t.readError
+	}
+	return p, nil
+}
+
+func (t *handshakeTransport) readLoop() {
+	first := true
+	for {
+		p, err := t.readOnePacket(first)
+		first = false
+		if err != nil {
+			t.readError = err
+			close(t.incoming)
+			break
+		}
+		if p[0] == msgIgnore || p[0] == msgDebug {
+			continue
+		}
+		t.incoming <- p
+	}
+
+	// Stop writers too.
+	t.recordWriteError(t.readError)
+
+	// Unblock the writer should it wait for this.
+	close(t.startKex)
+
+	// Don't close t.requestKex; it's also written to from writePacket.
+}
+
+func (t *handshakeTransport) pushPacket(p []byte) error {
+	if debugHandshake {
+		t.printPacket(p, true)
+	}
+	return t.conn.writePacket(p)
+}
+
+func (t *handshakeTransport) getWriteError() error {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	return t.writeError
+}
+
+func (t *handshakeTransport) recordWriteError(err error) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.writeError == nil && err != nil {
+		t.writeError = err
+	}
+}
+
+func (t *handshakeTransport) requestKeyExchange() {
+	select {
+	case t.requestKex <- struct{}{}:
+	default:
+		// something already requested a kex, so do nothing.
+	}
+}
+
+func (t *handshakeTransport) resetWriteThresholds() {
+	t.writePacketsLeft = packetRekeyThreshold
+	if t.config.RekeyThreshold > 0 {
+		t.writeBytesLeft = int64(t.config.RekeyThreshold)
+	} else if t.algorithms != nil {
+		t.writeBytesLeft = t.algorithms.w.rekeyBytes()
+	} else {
+		t.writeBytesLeft = 1 << 30
+	}
+}
+
+func (t *handshakeTransport) kexLoop() {
+
+write:
+	for t.getWriteError() == nil {
+		var request *pendingKex
+		var sent bool
+
+		for request == nil || !sent {
+			var ok bool
+			select {
+			case request, ok = <-t.startKex:
+				if !ok {
+					break write
+				}
+			case <-t.requestKex:
+				break
+			}
+
+			if !sent {
+				if err := t.sendKexInit(); err != nil {
+					t.recordWriteError(err)
+					break
+				}
+				sent = true
+			}
+		}
+
+		if err := t.getWriteError(); err != nil {
+			if request != nil {
+				request.done <- err
+			}
+			break
+		}
+
+		// We're not servicing t.requestKex, but that is OK:
+		// we never block on sending to t.requestKex.
+
+		// We're not servicing t.startKex, but the remote end
+		// has just sent us a kexInitMsg, so it can't send
+		// another key change request, until we close the done
+		// channel on the pendingKex request.
+
+		err := t.enterKeyExchange(request.otherInit)
+
+		t.mu.Lock()
+		t.writeError = err
+		t.sentInitPacket = nil
+		t.sentInitMsg = nil
+
+		t.resetWriteThresholds()
+
+		// we have completed the key exchange. Since the
+		// reader is still blocked, it is safe to clear out
+		// the requestKex channel. This avoids the situation
+		// where: 1) we consumed our own request for the
+		// initial kex, and 2) the kex from the remote side
+		// caused another send on the requestKex channel,
+	clear:
+		for {
+			select {
+			case <-t.requestKex:
+				//
+			default:
+				break clear
+			}
+		}
+
+		request.done <- t.writeError
+
+		// kex finished. Push packets that we received while
+		// the kex was in progress. Don't look at t.startKex
+		// and don't increment writtenSinceKex: if we trigger
+		// another kex while we are still busy with the last
+		// one, things will become very confusing.
+		for _, p := range t.pendingPackets {
+			t.writeError = t.pushPacket(p)
+			if t.writeError != nil {
+				break
+			}
+		}
+		t.pendingPackets = t.pendingPackets[:0]
+		t.mu.Unlock()
+	}
+
+	// drain startKex channel. We don't service t.requestKex
+	// because nobody does blocking sends there.
+	go func() {
+		for init := range t.startKex {
+			init.done <- t.writeError
+		}
+	}()
+
+	// Unblock reader.
+	t.conn.Close()
+}
+
+// The protocol uses uint32 for packet counters, so we can't let them
+// reach 1<<32.  We will actually read and write more packets than
+// this, though: the other side may send more packets, and after we
+// hit this limit on writing we will send a few more packets for the
+// key exchange itself.
+const packetRekeyThreshold = (1 << 31)
+
+func (t *handshakeTransport) resetReadThresholds() {
+	t.readPacketsLeft = packetRekeyThreshold
+	if t.config.RekeyThreshold > 0 {
+		t.readBytesLeft = int64(t.config.RekeyThreshold)
+	} else if t.algorithms != nil {
+		t.readBytesLeft = t.algorithms.r.rekeyBytes()
+	} else {
+		t.readBytesLeft = 1 << 30
+	}
+}
+
+func (t *handshakeTransport) readOnePacket(first bool) ([]byte, error) {
+	p, err := t.conn.readPacket()
+	if err != nil {
+		return nil, err
+	}
+
+	if t.readPacketsLeft > 0 {
+		t.readPacketsLeft--
+	} else {
+		t.requestKeyExchange()
+	}
+
+	if t.readBytesLeft > 0 {
+		t.readBytesLeft -= int64(len(p))
+	} else {
+		t.requestKeyExchange()
+	}
+
+	if debugHandshake {
+		t.printPacket(p, false)
+	}
+
+	if first && p[0] != msgKexInit {
+		return nil, fmt.Errorf("ssh: first packet should be msgKexInit")
+	}
+
+	if p[0] != msgKexInit {
+		return p, nil
+	}
+
+	firstKex := t.sessionID == nil
+
+	kex := pendingKex{
+		done:      make(chan error, 1),
+		otherInit: p,
+	}
+	t.startKex <- &kex
+	err = <-kex.done
+
+	if debugHandshake {
+		log.Printf("%s exited key exchange (first %v), err %v", t.id(), firstKex, err)
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	t.resetReadThresholds()
+
+	// By default, a key exchange is hidden from higher layers by
+	// translating it into msgIgnore.
+	successPacket := []byte{msgIgnore}
+	if firstKex {
+		// sendKexInit() for the first kex waits for
+		// msgNewKeys so the authentication process is
+		// guaranteed to happen over an encrypted transport.
+		successPacket = []byte{msgNewKeys}
+	}
+
+	return successPacket, nil
+}
+
+// sendKexInit sends a key change message.
+func (t *handshakeTransport) sendKexInit() error {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.sentInitMsg != nil {
+		// kexInits may be sent either in response to the other side,
+		// or because our side wants to initiate a key change, so we
+		// may have already sent a kexInit. In that case, don't send a
+		// second kexInit.
+		return nil
+	}
+
+	msg := &kexInitMsg{
+		KexAlgos:                t.config.KeyExchanges,
+		CiphersClientServer:     t.config.Ciphers,
+		CiphersServerClient:     t.config.Ciphers,
+		MACsClientServer:        t.config.MACs,
+		MACsServerClient:        t.config.MACs,
+		CompressionClientServer: supportedCompressions,
+		CompressionServerClient: supportedCompressions,
+	}
+	io.ReadFull(rand.Reader, msg.Cookie[:])
+
+	if len(t.hostKeys) > 0 {
+		for _, k := range t.hostKeys {
+			msg.ServerHostKeyAlgos = append(
+				msg.ServerHostKeyAlgos, k.PublicKey().Type())
+		}
+	} else {
+		msg.ServerHostKeyAlgos = t.hostKeyAlgorithms
+	}
+	packet := Marshal(msg)
+
+	// writePacket destroys the contents, so save a copy.
+	packetCopy := make([]byte, len(packet))
+	copy(packetCopy, packet)
+
+	if err := t.pushPacket(packetCopy); err != nil {
+		return err
+	}
+
+	t.sentInitMsg = msg
+	t.sentInitPacket = packet
+
+	return nil
+}
+
+func (t *handshakeTransport) writePacket(p []byte) error {
+	switch p[0] {
+	case msgKexInit:
+		return errors.New("ssh: only handshakeTransport can send kexInit")
+	case msgNewKeys:
+		return errors.New("ssh: only handshakeTransport can send newKeys")
+	}
+
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.writeError != nil {
+		return t.writeError
+	}
+
+	if t.sentInitMsg != nil {
+		// Copy the packet so the writer can reuse the buffer.
+		cp := make([]byte, len(p))
+		copy(cp, p)
+		t.pendingPackets = append(t.pendingPackets, cp)
+		return nil
+	}
+
+	if t.writeBytesLeft > 0 {
+		t.writeBytesLeft -= int64(len(p))
+	} else {
+		t.requestKeyExchange()
+	}
+
+	if t.writePacketsLeft > 0 {
+		t.writePacketsLeft--
+	} else {
+		t.requestKeyExchange()
+	}
+
+	if err := t.pushPacket(p); err != nil {
+		t.writeError = err
+	}
+
+	return nil
+}
+
+func (t *handshakeTransport) Close() error {
+	return t.conn.Close()
+}
+
+func (t *handshakeTransport) enterKeyExchange(otherInitPacket []byte) error {
+	if debugHandshake {
+		log.Printf("%s entered key exchange", t.id())
+	}
+
+	otherInit := &kexInitMsg{}
+	if err := Unmarshal(otherInitPacket, otherInit); err != nil {
+		return err
+	}
+
+	magics := handshakeMagics{
+		clientVersion: t.clientVersion,
+		serverVersion: t.serverVersion,
+		clientKexInit: otherInitPacket,
+		serverKexInit: t.sentInitPacket,
+	}
+
+	clientInit := otherInit
+	serverInit := t.sentInitMsg
+	if len(t.hostKeys) == 0 {
+		clientInit, serverInit = serverInit, clientInit
+
+		magics.clientKexInit = t.sentInitPacket
+		magics.serverKexInit = otherInitPacket
+	}
+
+	var err error
+	t.algorithms, err = findAgreedAlgorithms(clientInit, serverInit)
+	if err != nil {
+		return err
+	}
+
+	// We don't send FirstKexFollows, but we handle receiving it.
+	//
+	// RFC 4253 section 7 defines the kex and the agreement method for
+	// first_kex_packet_follows. It states that the guessed packet
+	// should be ignored if the "kex algorithm and/or the host
+	// key algorithm is guessed wrong (server and client have
+	// different preferred algorithm), or if any of the other
+	// algorithms cannot be agreed upon". The other algorithms have
+	// already been checked above so the kex algorithm and host key
+	// algorithm are checked here.
+	if otherInit.FirstKexFollows && (clientInit.KexAlgos[0] != serverInit.KexAlgos[0] || clientInit.ServerHostKeyAlgos[0] != serverInit.ServerHostKeyAlgos[0]) {
+		// other side sent a kex message for the wrong algorithm,
+		// which we have to ignore.
+		if _, err := t.conn.readPacket(); err != nil {
+			return err
+		}
+	}
+
+	kex, ok := kexAlgoMap[t.algorithms.kex]
+	if !ok {
+		return fmt.Errorf("ssh: unexpected key exchange algorithm %v", t.algorithms.kex)
+	}
+
+	var result *kexResult
+	if len(t.hostKeys) > 0 {
+		result, err = t.server(kex, t.algorithms, &magics)
+	} else {
+		result, err = t.client(kex, t.algorithms, &magics)
+	}
+
+	if err != nil {
+		return err
+	}
+
+	if t.sessionID == nil {
+		t.sessionID = result.H
+	}
+	result.SessionID = t.sessionID
+
+	if err := t.conn.prepareKeyChange(t.algorithms, result); err != nil {
+		return err
+	}
+	if err = t.conn.writePacket([]byte{msgNewKeys}); err != nil {
+		return err
+	}
+	if packet, err := t.conn.readPacket(); err != nil {
+		return err
+	} else if packet[0] != msgNewKeys {
+		return unexpectedMessageError(msgNewKeys, packet[0])
+	}
+
+	return nil
+}
+
+func (t *handshakeTransport) server(kex kexAlgorithm, algs *algorithms, magics *handshakeMagics) (*kexResult, error) {
+	var hostKey Signer
+	for _, k := range t.hostKeys {
+		if algs.hostKey == k.PublicKey().Type() {
+			hostKey = k
+		}
+	}
+
+	r, err := kex.Server(t.conn, t.config.Rand, magics, hostKey)
+	return r, err
+}
+
+func (t *handshakeTransport) client(kex kexAlgorithm, algs *algorithms, magics *handshakeMagics) (*kexResult, error) {
+	result, err := kex.Client(t.conn, t.config.Rand, magics)
+	if err != nil {
+		return nil, err
+	}
+
+	hostKey, err := ParsePublicKey(result.HostKey)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := verifyHostKeySignature(hostKey, result); err != nil {
+		return nil, err
+	}
+
+	err = t.hostKeyCallback(t.dialAddress, t.remoteAddr, hostKey)
+	if err != nil {
+		return nil, err
+	}
+
+	return result, nil
+}