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
227
228
229
230
231
232
233
234
235
|
// Copyright 2009 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 tls
// The handshake goroutine reads handshake messages from the record processor
// and outputs messages to be written on another channel. It updates the record
// processor with the state of the connection via the control channel. In the
// case of handshake messages that need synchronous processing (because they
// affect the handling of the next record) the record processor knows about
// them and either waits for a control message (Finished) or includes a reply
// channel in the message (ChangeCipherSpec).
import (
"crypto/hmac";
"crypto/rc4";
"crypto/rsa";
"crypto/sha1";
"crypto/subtle";
"io";
)
type cipherSuite struct {
id uint16; // The number of this suite on the wire.
hashLength, cipherKeyLength int;
// TODO(agl): need a method to create the cipher and hash interfaces.
}
var cipherSuites = []cipherSuite{
cipherSuite{TLS_RSA_WITH_RC4_128_SHA, 20, 16},
}
// A serverHandshake performs the server side of the TLS 1.1 handshake protocol.
type serverHandshake struct {
writeChan chan<- interface{};
controlChan chan<- interface{};
msgChan <-chan interface{};
config *Config;
}
func (h *serverHandshake) loop(writeChan chan<- interface{}, controlChan chan<- interface{}, msgChan <-chan interface{}, config *Config) {
h.writeChan = writeChan;
h.controlChan = controlChan;
h.msgChan = msgChan;
h.config = config;
defer close(writeChan);
defer close(controlChan);
clientHello, ok := h.readHandshakeMsg().(*clientHelloMsg);
if !ok {
h.error(alertUnexpectedMessage);
return;
}
major, minor, ok := mutualVersion(clientHello.major, clientHello.minor);
if !ok {
h.error(alertProtocolVersion);
return;
}
finishedHash := newFinishedHash();
finishedHash.Write(clientHello.marshal());
hello := new(serverHelloMsg);
// We only support a single ciphersuite so we look for it in the list
// of client supported suites.
//
// TODO(agl): Add additional cipher suites.
var suite *cipherSuite;
for _, id := range clientHello.cipherSuites {
for _, supported := range cipherSuites {
if supported.id == id {
suite = &supported;
break;
}
}
}
foundCompression := false;
// We only support null compression, so check that the client offered it.
for _, compression := range clientHello.compressionMethods {
if compression == compressionNone {
foundCompression = true;
break;
}
}
if suite == nil || !foundCompression {
h.error(alertHandshakeFailure);
return;
}
hello.major = major;
hello.minor = minor;
hello.cipherSuite = suite.id;
currentTime := uint32(config.Time());
hello.random = make([]byte, 32);
hello.random[0] = byte(currentTime >> 24);
hello.random[1] = byte(currentTime >> 16);
hello.random[2] = byte(currentTime >> 8);
hello.random[3] = byte(currentTime);
_, err := io.ReadFull(config.Rand, hello.random[4:]);
if err != nil {
h.error(alertInternalError);
return;
}
hello.compressionMethod = compressionNone;
finishedHash.Write(hello.marshal());
writeChan <- writerSetVersion{major, minor};
writeChan <- hello;
if len(config.Certificates) == 0 {
h.error(alertInternalError);
return;
}
certMsg := new(certificateMsg);
certMsg.certificates = config.Certificates[0].Certificate;
finishedHash.Write(certMsg.marshal());
writeChan <- certMsg;
helloDone := new(serverHelloDoneMsg);
finishedHash.Write(helloDone.marshal());
writeChan <- helloDone;
ckx, ok := h.readHandshakeMsg().(*clientKeyExchangeMsg);
if !ok {
h.error(alertUnexpectedMessage);
return;
}
finishedHash.Write(ckx.marshal());
preMasterSecret := make([]byte, 48);
_, err = io.ReadFull(config.Rand, preMasterSecret[2:]);
if err != nil {
h.error(alertInternalError);
return;
}
err = rsa.DecryptPKCS1v15SessionKey(config.Rand, config.Certificates[0].PrivateKey, ckx.ciphertext, preMasterSecret);
if err != nil {
h.error(alertHandshakeFailure);
return;
}
// We don't check the version number in the premaster secret. For one,
// by checking it, we would leak information about the validity of the
// encrypted pre-master secret. Secondly, it provides only a small
// benefit against a downgrade attack and some implementations send the
// wrong version anyway. See the discussion at the end of section
// 7.4.7.1 of RFC 4346.
masterSecret, clientMAC, serverMAC, clientKey, serverKey :=
keysFromPreMasterSecret11(preMasterSecret, clientHello.random, hello.random, suite.hashLength, suite.cipherKeyLength);
_, ok = h.readHandshakeMsg().(changeCipherSpec);
if !ok {
h.error(alertUnexpectedMessage);
return;
}
cipher, _ := rc4.NewCipher(clientKey);
controlChan <- &newCipherSpec{cipher, hmac.New(sha1.New(), clientMAC)};
clientFinished, ok := h.readHandshakeMsg().(*finishedMsg);
if !ok {
h.error(alertUnexpectedMessage);
return;
}
verify := finishedHash.clientSum(masterSecret);
if len(verify) != len(clientFinished.verifyData) ||
subtle.ConstantTimeCompare(verify, clientFinished.verifyData) != 1 {
h.error(alertHandshakeFailure);
return;
}
controlChan <- ConnectionState{true, "TLS_RSA_WITH_RC4_128_SHA", 0};
finishedHash.Write(clientFinished.marshal());
cipher2, _ := rc4.NewCipher(serverKey);
writeChan <- writerChangeCipherSpec{cipher2, hmac.New(sha1.New(), serverMAC)};
finished := new(finishedMsg);
finished.verifyData = finishedHash.serverSum(masterSecret);
writeChan <- finished;
writeChan <- writerEnableApplicationData{};
for {
_, ok := h.readHandshakeMsg().(*clientHelloMsg);
if !ok {
h.error(alertUnexpectedMessage);
return;
}
// We reject all renegotication requests.
writeChan <- alert{alertLevelWarning, alertNoRenegotiation};
}
}
func (h *serverHandshake) readHandshakeMsg() interface{} {
v := <-h.msgChan;
if closed(h.msgChan) {
// If the channel closed then the processor received an error
// from the peer and we don't want to echo it back to them.
h.msgChan = nil;
return 0;
}
if _, ok := v.(alert); ok {
// We got an alert from the processor. We forward to the writer
// and shutdown.
h.writeChan <- v;
h.msgChan = nil;
return 0;
}
return v;
}
func (h *serverHandshake) error(e alertType) {
if h.msgChan != nil {
// If we didn't get an error from the processor, then we need
// to tell it about the error.
h.controlChan <- ConnectionState{false, "", e};
close(h.controlChan);
go func() {
for _ = range h.msgChan {
}
}();
h.writeChan <- alert{alertLevelError, e};
}
}
|