fix subrepo break change

modules/crypto/ssh/common.go

@@ -0,0 +1,354 @@
+// Copyright 2011 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"
+	"crypto/rand"
+	"fmt"
+	"io"
+	"sync"
+
+	_ "crypto/sha1"
+	_ "crypto/sha256"
+	_ "crypto/sha512"
+)
+
+// These are string constants in the SSH protocol.
+const (
+	compressionNone = "none"
+	serviceUserAuth = "ssh-userauth"
+	serviceSSH      = "ssh-connection"
+)
+
+// supportedCiphers specifies the supported ciphers in preference order.
+var supportedCiphers = []string{
+	"aes128-ctr", "aes192-ctr", "aes256-ctr",
+	"aes128-gcm@openssh.com",
+	"arcfour256", "arcfour128",
+}
+
+// supportedKexAlgos specifies the supported key-exchange algorithms in
+// preference order.
+var supportedKexAlgos = []string{
+	kexAlgoCurve25519SHA256,
+	// P384 and P521 are not constant-time yet, but since we don't
+	// reuse ephemeral keys, using them for ECDH should be OK.
+	kexAlgoECDH256, kexAlgoECDH384, kexAlgoECDH521,
+	kexAlgoDH14SHA1, kexAlgoDH1SHA1,
+}
+
+// supportedKexAlgos specifies the supported host-key algorithms (i.e. methods
+// of authenticating servers) in preference order.
+var supportedHostKeyAlgos = []string{
+	CertAlgoRSAv01, CertAlgoDSAv01, CertAlgoECDSA256v01,
+	CertAlgoECDSA384v01, CertAlgoECDSA521v01,
+
+	KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521,
+	KeyAlgoRSA, KeyAlgoDSA,
+}
+
+// supportedMACs specifies a default set of MAC algorithms in preference order.
+// This is based on RFC 4253, section 6.4, but with hmac-md5 variants removed
+// because they have reached the end of their useful life.
+var supportedMACs = []string{
+	"hmac-sha2-256", "hmac-sha1", "hmac-sha1-96",
+}
+
+var supportedCompressions = []string{compressionNone}
+
+// hashFuncs keeps the mapping of supported algorithms to their respective
+// hashes needed for signature verification.
+var hashFuncs = map[string]crypto.Hash{
+	KeyAlgoRSA:          crypto.SHA1,
+	KeyAlgoDSA:          crypto.SHA1,
+	KeyAlgoECDSA256:     crypto.SHA256,
+	KeyAlgoECDSA384:     crypto.SHA384,
+	KeyAlgoECDSA521:     crypto.SHA512,
+	CertAlgoRSAv01:      crypto.SHA1,
+	CertAlgoDSAv01:      crypto.SHA1,
+	CertAlgoECDSA256v01: crypto.SHA256,
+	CertAlgoECDSA384v01: crypto.SHA384,
+	CertAlgoECDSA521v01: crypto.SHA512,
+}
+
+// unexpectedMessageError results when the SSH message that we received didn't
+// match what we wanted.
+func unexpectedMessageError(expected, got uint8) error {
+	return fmt.Errorf("ssh: unexpected message type %d (expected %d)", got, expected)
+}
+
+// parseError results from a malformed SSH message.
+func parseError(tag uint8) error {
+	return fmt.Errorf("ssh: parse error in message type %d", tag)
+}
+
+func findCommon(what string, client []string, server []string) (common string, err error) {
+	for _, c := range client {
+		for _, s := range server {
+			if c == s {
+				return c, nil
+			}
+		}
+	}
+	return "", fmt.Errorf("ssh: no common algorithm for %s; client offered: %v, server offered: %v", what, client, server)
+}
+
+type directionAlgorithms struct {
+	Cipher      string
+	MAC         string
+	Compression string
+}
+
+type algorithms struct {
+	kex     string
+	hostKey string
+	w       directionAlgorithms
+	r       directionAlgorithms
+}
+
+func findAgreedAlgorithms(clientKexInit, serverKexInit *kexInitMsg) (algs *algorithms, err error) {
+	result := &algorithms{}
+
+	result.kex, err = findCommon("key exchange", clientKexInit.KexAlgos, serverKexInit.KexAlgos)
+	if err != nil {
+		return
+	}
+
+	result.hostKey, err = findCommon("host key", clientKexInit.ServerHostKeyAlgos, serverKexInit.ServerHostKeyAlgos)
+	if err != nil {
+		return
+	}
+
+	result.w.Cipher, err = findCommon("client to server cipher", clientKexInit.CiphersClientServer, serverKexInit.CiphersClientServer)
+	if err != nil {
+		return
+	}
+
+	result.r.Cipher, err = findCommon("server to client cipher", clientKexInit.CiphersServerClient, serverKexInit.CiphersServerClient)
+	if err != nil {
+		return
+	}
+
+	result.w.MAC, err = findCommon("client to server MAC", clientKexInit.MACsClientServer, serverKexInit.MACsClientServer)
+	if err != nil {
+		return
+	}
+
+	result.r.MAC, err = findCommon("server to client MAC", clientKexInit.MACsServerClient, serverKexInit.MACsServerClient)
+	if err != nil {
+		return
+	}
+
+	result.w.Compression, err = findCommon("client to server compression", clientKexInit.CompressionClientServer, serverKexInit.CompressionClientServer)
+	if err != nil {
+		return
+	}
+
+	result.r.Compression, err = findCommon("server to client compression", clientKexInit.CompressionServerClient, serverKexInit.CompressionServerClient)
+	if err != nil {
+		return
+	}
+
+	return result, nil
+}
+
+// If rekeythreshold is too small, we can't make any progress sending
+// stuff.
+const minRekeyThreshold uint64 = 256
+
+// Config contains configuration data common to both ServerConfig and
+// ClientConfig.
+type Config struct {
+	// Rand provides the source of entropy for cryptographic
+	// primitives. If Rand is nil, the cryptographic random reader
+	// in package crypto/rand will be used.
+	Rand io.Reader
+
+	// The maximum number of bytes sent or received after which a
+	// new key is negotiated. It must be at least 256. If
+	// unspecified, 1 gigabyte is used.
+	RekeyThreshold uint64
+
+	// The allowed key exchanges algorithms. If unspecified then a
+	// default set of algorithms is used.
+	KeyExchanges []string
+
+	// The allowed cipher algorithms. If unspecified then a sensible
+	// default is used.
+	Ciphers []string
+
+	// The allowed MAC algorithms. If unspecified then a sensible default
+	// is used.
+	MACs []string
+}
+
+// SetDefaults sets sensible values for unset fields in config. This is
+// exported for testing: Configs passed to SSH functions are copied and have
+// default values set automatically.
+func (c *Config) SetDefaults() {
+	if c.Rand == nil {
+		c.Rand = rand.Reader
+	}
+	if c.Ciphers == nil {
+		c.Ciphers = supportedCiphers
+	}
+	var ciphers []string
+	for _, c := range c.Ciphers {
+		if cipherModes[c] != nil {
+			// reject the cipher if we have no cipherModes definition
+			ciphers = append(ciphers, c)
+		}
+	}
+	c.Ciphers = ciphers
+
+	if c.KeyExchanges == nil {
+		c.KeyExchanges = supportedKexAlgos
+	}
+
+	if c.MACs == nil {
+		c.MACs = supportedMACs
+	}
+
+	if c.RekeyThreshold == 0 {
+		// RFC 4253, section 9 suggests rekeying after 1G.
+		c.RekeyThreshold = 1 << 30
+	}
+	if c.RekeyThreshold < minRekeyThreshold {
+		c.RekeyThreshold = minRekeyThreshold
+	}
+}
+
+// buildDataSignedForAuth returns the data that is signed in order to prove
+// possession of a private key. See RFC 4252, section 7.
+func buildDataSignedForAuth(sessionId []byte, req userAuthRequestMsg, algo, pubKey []byte) []byte {
+	data := struct {
+		Session []byte
+		Type    byte
+		User    string
+		Service string
+		Method  string
+		Sign    bool
+		Algo    []byte
+		PubKey  []byte
+	}{
+		sessionId,
+		msgUserAuthRequest,
+		req.User,
+		req.Service,
+		req.Method,
+		true,
+		algo,
+		pubKey,
+	}
+	return Marshal(data)
+}
+
+func appendU16(buf []byte, n uint16) []byte {
+	return append(buf, byte(n>>8), byte(n))
+}
+
+func appendU32(buf []byte, n uint32) []byte {
+	return append(buf, byte(n>>24), byte(n>>16), byte(n>>8), byte(n))
+}
+
+func appendU64(buf []byte, n uint64) []byte {
+	return append(buf,
+		byte(n>>56), byte(n>>48), byte(n>>40), byte(n>>32),
+		byte(n>>24), byte(n>>16), byte(n>>8), byte(n))
+}
+
+func appendInt(buf []byte, n int) []byte {
+	return appendU32(buf, uint32(n))
+}
+
+func appendString(buf []byte, s string) []byte {
+	buf = appendU32(buf, uint32(len(s)))
+	buf = append(buf, s...)
+	return buf
+}
+
+func appendBool(buf []byte, b bool) []byte {
+	if b {
+		return append(buf, 1)
+	}
+	return append(buf, 0)
+}
+
+// newCond is a helper to hide the fact that there is no usable zero
+// value for sync.Cond.
+func newCond() *sync.Cond { return sync.NewCond(new(sync.Mutex)) }
+
+// window represents the buffer available to clients
+// wishing to write to a channel.
+type window struct {
+	*sync.Cond
+	win          uint32 // RFC 4254 5.2 says the window size can grow to 2^32-1
+	writeWaiters int
+	closed       bool
+}
+
+// add adds win to the amount of window available
+// for consumers.
+func (w *window) add(win uint32) bool {
+	// a zero sized window adjust is a noop.
+	if win == 0 {
+		return true
+	}
+	w.L.Lock()
+	if w.win+win < win {
+		w.L.Unlock()
+		return false
+	}
+	w.win += win
+	// It is unusual that multiple goroutines would be attempting to reserve
+	// window space, but not guaranteed. Use broadcast to notify all waiters
+	// that additional window is available.
+	w.Broadcast()
+	w.L.Unlock()
+	return true
+}
+
+// close sets the window to closed, so all reservations fail
+// immediately.
+func (w *window) close() {
+	w.L.Lock()
+	w.closed = true
+	w.Broadcast()
+	w.L.Unlock()
+}
+
+// reserve reserves win from the available window capacity.
+// If no capacity remains, reserve will block. reserve may
+// return less than requested.
+func (w *window) reserve(win uint32) (uint32, error) {
+	var err error
+	w.L.Lock()
+	w.writeWaiters++
+	w.Broadcast()
+	for w.win == 0 && !w.closed {
+		w.Wait()
+	}
+	w.writeWaiters--
+	if w.win < win {
+		win = w.win
+	}
+	w.win -= win
+	if w.closed {
+		err = io.EOF
+	}
+	w.L.Unlock()
+	return win, err
+}
+
+// waitWriterBlocked waits until some goroutine is blocked for further
+// writes. It is used in tests only.
+func (w *window) waitWriterBlocked() {
+	w.Cond.L.Lock()
+	for w.writeWaiters == 0 {
+		w.Cond.Wait()
+	}
+	w.Cond.L.Unlock()
+}