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// 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/dsa"
"crypto/rsa"
"math/big"
"strconv"
"sync"
)
// These are string constants in the SSH protocol.
const (
kexAlgoDH14SHA1 = "diffie-hellman-group14-sha1"
hostAlgoRSA = "ssh-rsa"
macSHA196 = "hmac-sha1-96"
compressionNone = "none"
serviceUserAuth = "ssh-userauth"
serviceSSH = "ssh-connection"
)
var supportedKexAlgos = []string{kexAlgoDH14SHA1}
var supportedHostKeyAlgos = []string{hostAlgoRSA}
var supportedMACs = []string{macSHA196}
var supportedCompressions = []string{compressionNone}
// dhGroup is a multiplicative group suitable for implementing Diffie-Hellman key agreement.
type dhGroup struct {
g, p *big.Int
}
// dhGroup14 is the group called diffie-hellman-group14-sha1 in RFC 4253 and
// Oakley Group 14 in RFC 3526.
var dhGroup14 *dhGroup
var dhGroup14Once sync.Once
func initDHGroup14() {
p, _ := new(big.Int).SetString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
dhGroup14 = &dhGroup{
g: new(big.Int).SetInt64(2),
p: p,
}
}
// UnexpectedMessageError results when the SSH message that we received didn't
// match what we wanted.
type UnexpectedMessageError struct {
expected, got uint8
}
func (u UnexpectedMessageError) Error() string {
return "ssh: unexpected message type " + strconv.Itoa(int(u.got)) + " (expected " + strconv.Itoa(int(u.expected)) + ")"
}
// ParseError results from a malformed SSH message.
type ParseError struct {
msgType uint8
}
func (p ParseError) Error() string {
return "ssh: parse error in message type " + strconv.Itoa(int(p.msgType))
}
type handshakeMagics struct {
clientVersion, serverVersion []byte
clientKexInit, serverKexInit []byte
}
func findCommonAlgorithm(clientAlgos []string, serverAlgos []string) (commonAlgo string, ok bool) {
for _, clientAlgo := range clientAlgos {
for _, serverAlgo := range serverAlgos {
if clientAlgo == serverAlgo {
return clientAlgo, true
}
}
}
return
}
func findAgreedAlgorithms(transport *transport, clientKexInit, serverKexInit *kexInitMsg) (kexAlgo, hostKeyAlgo string, ok bool) {
kexAlgo, ok = findCommonAlgorithm(clientKexInit.KexAlgos, serverKexInit.KexAlgos)
if !ok {
return
}
hostKeyAlgo, ok = findCommonAlgorithm(clientKexInit.ServerHostKeyAlgos, serverKexInit.ServerHostKeyAlgos)
if !ok {
return
}
transport.writer.cipherAlgo, ok = findCommonAlgorithm(clientKexInit.CiphersClientServer, serverKexInit.CiphersClientServer)
if !ok {
return
}
transport.reader.cipherAlgo, ok = findCommonAlgorithm(clientKexInit.CiphersServerClient, serverKexInit.CiphersServerClient)
if !ok {
return
}
transport.writer.macAlgo, ok = findCommonAlgorithm(clientKexInit.MACsClientServer, serverKexInit.MACsClientServer)
if !ok {
return
}
transport.reader.macAlgo, ok = findCommonAlgorithm(clientKexInit.MACsServerClient, serverKexInit.MACsServerClient)
if !ok {
return
}
transport.writer.compressionAlgo, ok = findCommonAlgorithm(clientKexInit.CompressionClientServer, serverKexInit.CompressionClientServer)
if !ok {
return
}
transport.reader.compressionAlgo, ok = findCommonAlgorithm(clientKexInit.CompressionServerClient, serverKexInit.CompressionServerClient)
if !ok {
return
}
ok = true
return
}
// Cryptographic configuration common to both ServerConfig and ClientConfig.
type CryptoConfig struct {
// The allowed cipher algorithms. If unspecified then DefaultCipherOrder is
// used.
Ciphers []string
}
func (c *CryptoConfig) ciphers() []string {
if c.Ciphers == nil {
return DefaultCipherOrder
}
return c.Ciphers
}
// serialize a signed slice according to RFC 4254 6.6.
func serializeSignature(algoname string, sig []byte) []byte {
length := stringLength([]byte(algoname))
length += stringLength(sig)
ret := make([]byte, length)
r := marshalString(ret, []byte(algoname))
r = marshalString(r, sig)
return ret
}
// serialize an rsa.PublicKey or dsa.PublicKey according to RFC 4253 6.6.
func serializePublickey(key interface{}) []byte {
algoname := algoName(key)
switch key := key.(type) {
case rsa.PublicKey:
e := new(big.Int).SetInt64(int64(key.E))
length := stringLength([]byte(algoname))
length += intLength(e)
length += intLength(key.N)
ret := make([]byte, length)
r := marshalString(ret, []byte(algoname))
r = marshalInt(r, e)
marshalInt(r, key.N)
return ret
case dsa.PublicKey:
length := stringLength([]byte(algoname))
length += intLength(key.P)
length += intLength(key.Q)
length += intLength(key.G)
length += intLength(key.Y)
ret := make([]byte, length)
r := marshalString(ret, []byte(algoname))
r = marshalInt(r, key.P)
r = marshalInt(r, key.Q)
r = marshalInt(r, key.G)
marshalInt(r, key.Y)
return ret
}
panic("unexpected key type")
}
func algoName(key interface{}) string {
switch key.(type) {
case rsa.PublicKey:
return "ssh-rsa"
case dsa.PublicKey:
return "ssh-dss"
}
panic("unexpected key type")
}
// buildDataSignedForAuth returns the data that is signed in order to prove
// posession of a private key. See RFC 4252, section 7.
func buildDataSignedForAuth(sessionId []byte, req userAuthRequestMsg, algo, pubKey []byte) []byte {
user := []byte(req.User)
service := []byte(req.Service)
method := []byte(req.Method)
length := stringLength(sessionId)
length += 1
length += stringLength(user)
length += stringLength(service)
length += stringLength(method)
length += 1
length += stringLength(algo)
length += stringLength(pubKey)
ret := make([]byte, length)
r := marshalString(ret, sessionId)
r[0] = msgUserAuthRequest
r = r[1:]
r = marshalString(r, user)
r = marshalString(r, service)
r = marshalString(r, method)
r[0] = 1
r = r[1:]
r = marshalString(r, algo)
r = marshalString(r, pubKey)
return ret
}
// safeString sanitises s according to RFC 4251, section 9.2.
// All control characters except tab, carriage return and newline are
// replaced by 0x20.
func safeString(s string) string {
out := []byte(s)
for i, c := range out {
if c < 0x20 && c != 0xd && c != 0xa && c != 0x9 {
out[i] = 0x20
}
}
return string(out)
}
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