1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
|
// 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
}
|
