1// Copyright 2009 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package tls
6
7import (
8	"crypto"
9	"crypto/hmac"
10	"crypto/md5"
11	"crypto/sha1"
12	"crypto/sha256"
13	"hash"
14)
15
16// Split a premaster secret in two as specified in RFC 4346, section 5.
17func splitPreMasterSecret(secret []byte) (s1, s2 []byte) {
18	s1 = secret[0 : (len(secret)+1)/2]
19	s2 = secret[len(secret)/2:]
20	return
21}
22
23// pHash implements the P_hash function, as defined in RFC 4346, section 5.
24func pHash(result, secret, seed []byte, hash func() hash.Hash) {
25	h := hmac.New(hash, secret)
26	h.Write(seed)
27	a := h.Sum(nil)
28
29	j := 0
30	for j < len(result) {
31		h.Reset()
32		h.Write(a)
33		h.Write(seed)
34		b := h.Sum(nil)
35		todo := len(b)
36		if j+todo > len(result) {
37			todo = len(result) - j
38		}
39		copy(result[j:j+todo], b)
40		j += todo
41
42		h.Reset()
43		h.Write(a)
44		a = h.Sum(nil)
45	}
46}
47
48// prf10 implements the TLS 1.0 pseudo-random function, as defined in RFC 2246, section 5.
49func prf10(result, secret, label, seed []byte) {
50	hashSHA1 := sha1.New
51	hashMD5 := md5.New
52
53	labelAndSeed := make([]byte, len(label)+len(seed))
54	copy(labelAndSeed, label)
55	copy(labelAndSeed[len(label):], seed)
56
57	s1, s2 := splitPreMasterSecret(secret)
58	pHash(result, s1, labelAndSeed, hashMD5)
59	result2 := make([]byte, len(result))
60	pHash(result2, s2, labelAndSeed, hashSHA1)
61
62	for i, b := range result2 {
63		result[i] ^= b
64	}
65}
66
67// prf12 implements the TLS 1.2 pseudo-random function, as defined in RFC 5246, section 5.
68func prf12(result, secret, label, seed []byte) {
69	labelAndSeed := make([]byte, len(label)+len(seed))
70	copy(labelAndSeed, label)
71	copy(labelAndSeed[len(label):], seed)
72
73	pHash(result, secret, labelAndSeed, sha256.New)
74}
75
76// prf30 implements the SSL 3.0 pseudo-random function, as defined in
77// www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt section 6.
78func prf30(result, secret, label, seed []byte) {
79	hashSHA1 := sha1.New()
80	hashMD5 := md5.New()
81
82	done := 0
83	i := 0
84	// RFC5246 section 6.3 says that the largest PRF output needed is 128
85	// bytes. Since no more ciphersuites will be added to SSLv3, this will
86	// remain true. Each iteration gives us 16 bytes so 10 iterations will
87	// be sufficient.
88	var b [11]byte
89	for done < len(result) {
90		for j := 0; j <= i; j++ {
91			b[j] = 'A' + byte(i)
92		}
93
94		hashSHA1.Reset()
95		hashSHA1.Write(b[:i+1])
96		hashSHA1.Write(secret)
97		hashSHA1.Write(seed)
98		digest := hashSHA1.Sum(nil)
99
100		hashMD5.Reset()
101		hashMD5.Write(secret)
102		hashMD5.Write(digest)
103
104		done += copy(result[done:], hashMD5.Sum(nil))
105		i++
106	}
107}
108
109const (
110	tlsRandomLength      = 32 // Length of a random nonce in TLS 1.1.
111	masterSecretLength   = 48 // Length of a master secret in TLS 1.1.
112	finishedVerifyLength = 12 // Length of verify_data in a Finished message.
113)
114
115var masterSecretLabel = []byte("master secret")
116var keyExpansionLabel = []byte("key expansion")
117var clientFinishedLabel = []byte("client finished")
118var serverFinishedLabel = []byte("server finished")
119
120func prfForVersion(version uint16) func(result, secret, label, seed []byte) {
121	switch version {
122	case VersionSSL30:
123		return prf30
124	case VersionTLS10, VersionTLS11:
125		return prf10
126	case VersionTLS12:
127		return prf12
128	default:
129		panic("unknown version")
130	}
131}
132
133// masterFromPreMasterSecret generates the master secret from the pre-master
134// secret. See http://tools.ietf.org/html/rfc5246#section-8.1
135func masterFromPreMasterSecret(version uint16, preMasterSecret, clientRandom, serverRandom []byte) []byte {
136	var seed [tlsRandomLength * 2]byte
137	copy(seed[0:len(clientRandom)], clientRandom)
138	copy(seed[len(clientRandom):], serverRandom)
139	masterSecret := make([]byte, masterSecretLength)
140	prfForVersion(version)(masterSecret, preMasterSecret, masterSecretLabel, seed[0:])
141	return masterSecret
142}
143
144// keysFromMasterSecret generates the connection keys from the master
145// secret, given the lengths of the MAC key, cipher key and IV, as defined in
146// RFC 2246, section 6.3.
147func keysFromMasterSecret(version uint16, masterSecret, clientRandom, serverRandom []byte, macLen, keyLen, ivLen int) (clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV []byte) {
148	var seed [tlsRandomLength * 2]byte
149	copy(seed[0:len(clientRandom)], serverRandom)
150	copy(seed[len(serverRandom):], clientRandom)
151
152	n := 2*macLen + 2*keyLen + 2*ivLen
153	keyMaterial := make([]byte, n)
154	prfForVersion(version)(keyMaterial, masterSecret, keyExpansionLabel, seed[0:])
155	clientMAC = keyMaterial[:macLen]
156	keyMaterial = keyMaterial[macLen:]
157	serverMAC = keyMaterial[:macLen]
158	keyMaterial = keyMaterial[macLen:]
159	clientKey = keyMaterial[:keyLen]
160	keyMaterial = keyMaterial[keyLen:]
161	serverKey = keyMaterial[:keyLen]
162	keyMaterial = keyMaterial[keyLen:]
163	clientIV = keyMaterial[:ivLen]
164	keyMaterial = keyMaterial[ivLen:]
165	serverIV = keyMaterial[:ivLen]
166	return
167}
168
169func newFinishedHash(version uint16) finishedHash {
170	if version >= VersionTLS12 {
171		return finishedHash{sha256.New(), sha256.New(), nil, nil, version}
172	}
173	return finishedHash{sha1.New(), sha1.New(), md5.New(), md5.New(), version}
174}
175
176// A finishedHash calculates the hash of a set of handshake messages suitable
177// for including in a Finished message.
178type finishedHash struct {
179	client hash.Hash
180	server hash.Hash
181
182	// Prior to TLS 1.2, an additional MD5 hash is required.
183	clientMD5 hash.Hash
184	serverMD5 hash.Hash
185
186	version uint16
187}
188
189func (h finishedHash) Write(msg []byte) (n int, err error) {
190	h.client.Write(msg)
191	h.server.Write(msg)
192
193	if h.version < VersionTLS12 {
194		h.clientMD5.Write(msg)
195		h.serverMD5.Write(msg)
196	}
197	return len(msg), nil
198}
199
200// finishedSum30 calculates the contents of the verify_data member of a SSLv3
201// Finished message given the MD5 and SHA1 hashes of a set of handshake
202// messages.
203func finishedSum30(md5, sha1 hash.Hash, masterSecret []byte, magic [4]byte) []byte {
204	md5.Write(magic[:])
205	md5.Write(masterSecret)
206	md5.Write(ssl30Pad1[:])
207	md5Digest := md5.Sum(nil)
208
209	md5.Reset()
210	md5.Write(masterSecret)
211	md5.Write(ssl30Pad2[:])
212	md5.Write(md5Digest)
213	md5Digest = md5.Sum(nil)
214
215	sha1.Write(magic[:])
216	sha1.Write(masterSecret)
217	sha1.Write(ssl30Pad1[:40])
218	sha1Digest := sha1.Sum(nil)
219
220	sha1.Reset()
221	sha1.Write(masterSecret)
222	sha1.Write(ssl30Pad2[:40])
223	sha1.Write(sha1Digest)
224	sha1Digest = sha1.Sum(nil)
225
226	ret := make([]byte, len(md5Digest)+len(sha1Digest))
227	copy(ret, md5Digest)
228	copy(ret[len(md5Digest):], sha1Digest)
229	return ret
230}
231
232var ssl3ClientFinishedMagic = [4]byte{0x43, 0x4c, 0x4e, 0x54}
233var ssl3ServerFinishedMagic = [4]byte{0x53, 0x52, 0x56, 0x52}
234
235// clientSum returns the contents of the verify_data member of a client's
236// Finished message.
237func (h finishedHash) clientSum(masterSecret []byte) []byte {
238	if h.version == VersionSSL30 {
239		return finishedSum30(h.clientMD5, h.client, masterSecret, ssl3ClientFinishedMagic)
240	}
241
242	out := make([]byte, finishedVerifyLength)
243	if h.version >= VersionTLS12 {
244		seed := h.client.Sum(nil)
245		prf12(out, masterSecret, clientFinishedLabel, seed)
246	} else {
247		seed := make([]byte, 0, md5.Size+sha1.Size)
248		seed = h.clientMD5.Sum(seed)
249		seed = h.client.Sum(seed)
250		prf10(out, masterSecret, clientFinishedLabel, seed)
251	}
252	return out
253}
254
255// serverSum returns the contents of the verify_data member of a server's
256// Finished message.
257func (h finishedHash) serverSum(masterSecret []byte) []byte {
258	if h.version == VersionSSL30 {
259		return finishedSum30(h.serverMD5, h.server, masterSecret, ssl3ServerFinishedMagic)
260	}
261
262	out := make([]byte, finishedVerifyLength)
263	if h.version >= VersionTLS12 {
264		seed := h.server.Sum(nil)
265		prf12(out, masterSecret, serverFinishedLabel, seed)
266	} else {
267		seed := make([]byte, 0, md5.Size+sha1.Size)
268		seed = h.serverMD5.Sum(seed)
269		seed = h.server.Sum(seed)
270		prf10(out, masterSecret, serverFinishedLabel, seed)
271	}
272	return out
273}
274
275// hashForClientCertificate returns a digest, hash function, and TLS 1.2 hash
276// id suitable for signing by a TLS client certificate.
277func (h finishedHash) hashForClientCertificate(sigType uint8) ([]byte, crypto.Hash, uint8) {
278	if h.version >= VersionTLS12 {
279		digest := h.server.Sum(nil)
280		return digest, crypto.SHA256, hashSHA256
281	}
282	if sigType == signatureECDSA {
283		digest := h.server.Sum(nil)
284		return digest, crypto.SHA1, hashSHA1
285	}
286
287	digest := make([]byte, 0, 36)
288	digest = h.serverMD5.Sum(digest)
289	digest = h.server.Sum(digest)
290	return digest, crypto.MD5SHA1, 0 /* not specified in TLS 1.2. */
291}
292