fix subrepo break change

modules/crypto/ssh/handshake.go

@@ -0,0 +1,412 @@
+// 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
+
+// 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
+
+	// getSessionID returns the session ID. prepareKeyChange must
+	// have been called once.
+	getSessionID() []byte
+}
+
+// rekeyingTransport is the interface of handshakeTransport that we
+// (internally) expose to ClientConn and ServerConn.
+type rekeyingTransport interface {
+	packetConn
+
+	// requestKeyChange asks the remote side to change keys. All
+	// writes are blocked until the key change succeeds, which is
+	// signaled by reading a msgNewKeys.
+	requestKeyChange() error
+
+	// getSessionID returns the session ID. This is only valid
+	// after the first key change has completed.
+	getSessionID() []byte
+}
+
+// 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
+
+	// data for host key checking
+	hostKeyCallback func(hostname string, remote net.Addr, key PublicKey) error
+	dialAddress     string
+	remoteAddr      net.Addr
+
+	readSinceKex uint64
+
+	// Protects the writing side of the connection
+	mu              sync.Mutex
+	cond            *sync.Cond
+	sentInitPacket  []byte
+	sentInitMsg     *kexInitMsg
+	writtenSinceKex uint64
+	writeError      error
+}
+
+func newHandshakeTransport(conn keyingTransport, config *Config, clientVersion, serverVersion []byte) *handshakeTransport {
+	t := &handshakeTransport{
+		conn:          conn,
+		serverVersion: serverVersion,
+		clientVersion: clientVersion,
+		incoming:      make(chan []byte, 16),
+		config:        config,
+	}
+	t.cond = sync.NewCond(&t.mu)
+	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
+	if config.HostKeyAlgorithms != nil {
+		t.hostKeyAlgorithms = config.HostKeyAlgorithms
+	} else {
+		t.hostKeyAlgorithms = supportedHostKeyAlgos
+	}
+	go t.readLoop()
+	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()
+	return t
+}
+
+func (t *handshakeTransport) getSessionID() []byte {
+	return t.conn.getSessionID()
+}
+
+func (t *handshakeTransport) id() string {
+	if len(t.hostKeys) > 0 {
+		return "server"
+	}
+	return "client"
+}
+
+func (t *handshakeTransport) readPacket() ([]byte, error) {
+	p, ok := <-t.incoming
+	if !ok {
+		return nil, t.readError
+	}
+	return p, nil
+}
+
+func (t *handshakeTransport) readLoop() {
+	for {
+		p, err := t.readOnePacket()
+		if err != nil {
+			t.readError = err
+			close(t.incoming)
+			break
+		}
+		if p[0] == msgIgnore || p[0] == msgDebug {
+			continue
+		}
+		t.incoming <- p
+	}
+
+	// If we can't read, declare the writing part dead too.
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.writeError == nil {
+		t.writeError = t.readError
+	}
+	t.cond.Broadcast()
+}
+
+func (t *handshakeTransport) readOnePacket() ([]byte, error) {
+	if t.readSinceKex > t.config.RekeyThreshold {
+		if err := t.requestKeyChange(); err != nil {
+			return nil, err
+		}
+	}
+
+	p, err := t.conn.readPacket()
+	if err != nil {
+		return nil, err
+	}
+
+	t.readSinceKex += uint64(len(p))
+	if debugHandshake {
+		msg, err := decode(p)
+		log.Printf("%s got %T %v (%v)", t.id(), msg, msg, err)
+	}
+	if p[0] != msgKexInit {
+		return p, nil
+	}
+	err = t.enterKeyExchange(p)
+
+	t.mu.Lock()
+	if err != nil {
+		// drop connection
+		t.conn.Close()
+		t.writeError = err
+	}
+
+	if debugHandshake {
+		log.Printf("%s exited key exchange, err %v", t.id(), err)
+	}
+
+	// Unblock writers.
+	t.sentInitMsg = nil
+	t.sentInitPacket = nil
+	t.cond.Broadcast()
+	t.writtenSinceKex = 0
+	t.mu.Unlock()
+
+	if err != nil {
+		return nil, err
+	}
+
+	t.readSinceKex = 0
+	return []byte{msgNewKeys}, nil
+}
+
+// sendKexInit sends a key change message, and returns the message
+// that was sent. After initiating the key change, all writes will be
+// blocked until the change is done, and a failed key change will
+// close the underlying transport. This function is safe for
+// concurrent use by multiple goroutines.
+func (t *handshakeTransport) sendKexInit() (*kexInitMsg, []byte, error) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	return t.sendKexInitLocked()
+}
+
+func (t *handshakeTransport) requestKeyChange() error {
+	_, _, err := t.sendKexInit()
+	return err
+}
+
+// sendKexInitLocked sends a key change message. t.mu must be locked
+// while this happens.
+func (t *handshakeTransport) sendKexInitLocked() (*kexInitMsg, []byte, error) {
+	// 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.
+	if t.sentInitMsg != nil {
+		return t.sentInitMsg, t.sentInitPacket, 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.conn.writePacket(packetCopy); err != nil {
+		return nil, nil, err
+	}
+
+	t.sentInitMsg = msg
+	t.sentInitPacket = packet
+	return msg, packet, nil
+}
+
+func (t *handshakeTransport) writePacket(p []byte) error {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+
+	if t.writtenSinceKex > t.config.RekeyThreshold {
+		t.sendKexInitLocked()
+	}
+	for t.sentInitMsg != nil && t.writeError == nil {
+		t.cond.Wait()
+	}
+	if t.writeError != nil {
+		return t.writeError
+	}
+	t.writtenSinceKex += uint64(len(p))
+
+	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")
+	default:
+		return t.conn.writePacket(p)
+	}
+}
+
+func (t *handshakeTransport) Close() error {
+	return t.conn.Close()
+}
+
+// enterKeyExchange runs the key exchange.
+func (t *handshakeTransport) enterKeyExchange(otherInitPacket []byte) error {
+	if debugHandshake {
+		log.Printf("%s entered key exchange", t.id())
+	}
+	myInit, myInitPacket, err := t.sendKexInit()
+	if err != nil {
+		return err
+	}
+
+	otherInit := &kexInitMsg{}
+	if err := Unmarshal(otherInitPacket, otherInit); err != nil {
+		return err
+	}
+
+	magics := handshakeMagics{
+		clientVersion: t.clientVersion,
+		serverVersion: t.serverVersion,
+		clientKexInit: otherInitPacket,
+		serverKexInit: myInitPacket,
+	}
+
+	clientInit := otherInit
+	serverInit := myInit
+	if len(t.hostKeys) == 0 {
+		clientInit = myInit
+		serverInit = otherInit
+
+		magics.clientKexInit = myInitPacket
+		magics.serverKexInit = otherInitPacket
+	}
+
+	algs, err := findAgreedAlgorithms(clientInit, serverInit)
+	if err != nil {
+		return err
+	}
+
+	// We don't send FirstKexFollows, but we handle receiving it.
+	if otherInit.FirstKexFollows && algs.kex != otherInit.KexAlgos[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[algs.kex]
+	if !ok {
+		return fmt.Errorf("ssh: unexpected key exchange algorithm %v", algs.kex)
+	}
+
+	var result *kexResult
+	if len(t.hostKeys) > 0 {
+		result, err = t.server(kex, algs, &magics)
+	} else {
+		result, err = t.client(kex, algs, &magics)
+	}
+
+	if err != nil {
+		return err
+	}
+
+	t.conn.prepareKeyChange(algs, result)
+	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
+	}
+
+	if t.hostKeyCallback != nil {
+		err = t.hostKeyCallback(t.dialAddress, t.remoteAddr, hostKey)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return result, nil
+}