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	"crypto/sha512"
14	"errors"
15	"fmt"
16	"hash"
17)
18
19// Split a premaster secret in two as specified in RFC 4346, section 5.
20func splitPreMasterSecret(secret []byte) (s1, s2 []byte) {
21	s1 = secret[0 : (len(secret)+1)/2]
22	s2 = secret[len(secret)/2:]
23	return
24}
25
26// pHash implements the P_hash function, as defined in RFC 4346, section 5.
27func pHash(result, secret, seed []byte, hash func() hash.Hash) {
28	h := hmac.New(hash, secret)
29	h.Write(seed)
30	a := h.Sum(nil)
31
32	j := 0
33	for j < len(result) {
34		h.Reset()
35		h.Write(a)
36		h.Write(seed)
37		b := h.Sum(nil)
38		copy(result[j:], b)
39		j += len(b)
40
41		h.Reset()
42		h.Write(a)
43		a = h.Sum(nil)
44	}
45}
46
47// prf10 implements the TLS 1.0 pseudo-random function, as defined in RFC 2246, section 5.
48func prf10(result, secret, label, seed []byte) {
49	hashSHA1 := sha1.New
50	hashMD5 := md5.New
51
52	labelAndSeed := make([]byte, len(label)+len(seed))
53	copy(labelAndSeed, label)
54	copy(labelAndSeed[len(label):], seed)
55
56	s1, s2 := splitPreMasterSecret(secret)
57	pHash(result, s1, labelAndSeed, hashMD5)
58	result2 := make([]byte, len(result))
59	pHash(result2, s2, labelAndSeed, hashSHA1)
60
61	for i, b := range result2 {
62		result[i] ^= b
63	}
64}
65
66// prf12 implements the TLS 1.2 pseudo-random function, as defined in RFC 5246, section 5.
67func prf12(hashFunc func() hash.Hash) func(result, secret, label, seed []byte) {
68	return func(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, hashFunc)
74	}
75}
76
77// prf30 implements the SSL 3.0 pseudo-random function, as defined in
78// www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt section 6.
79func prf30(result, secret, label, seed []byte) {
80	hashSHA1 := sha1.New()
81	hashMD5 := md5.New()
82
83	done := 0
84	i := 0
85	// RFC 5246 section 6.3 says that the largest PRF output needed is 128
86	// bytes. Since no more ciphersuites will be added to SSLv3, this will
87	// remain true. Each iteration gives us 16 bytes so 10 iterations will
88	// be sufficient.
89	var b [11]byte
90	for done < len(result) {
91		for j := 0; j <= i; j++ {
92			b[j] = 'A' + byte(i)
93		}
94
95		hashSHA1.Reset()
96		hashSHA1.Write(b[:i+1])
97		hashSHA1.Write(secret)
98		hashSHA1.Write(seed)
99		digest := hashSHA1.Sum(nil)
100
101		hashMD5.Reset()
102		hashMD5.Write(secret)
103		hashMD5.Write(digest)
104
105		done += copy(result[done:], hashMD5.Sum(nil))
106		i++
107	}
108}
109
110const (
111	tlsRandomLength      = 32 // Length of a random nonce in TLS 1.1.
112	masterSecretLength   = 48 // Length of a master secret in TLS 1.1.
113	finishedVerifyLength = 12 // Length of verify_data in a Finished message.
114)
115
116var masterSecretLabel = []byte("master secret")
117var keyExpansionLabel = []byte("key expansion")
118var clientFinishedLabel = []byte("client finished")
119var serverFinishedLabel = []byte("server finished")
120
121func prfAndHashForVersion(version uint16, suite *cipherSuite) (func(result, secret, label, seed []byte), crypto.Hash) {
122	switch version {
123	case VersionSSL30:
124		return prf30, crypto.Hash(0)
125	case VersionTLS10, VersionTLS11:
126		return prf10, crypto.Hash(0)
127	case VersionTLS12:
128		if suite.flags&suiteSHA384 != 0 {
129			return prf12(sha512.New384), crypto.SHA384
130		}
131		return prf12(sha256.New), crypto.SHA256
132	default:
133		panic("unknown version")
134	}
135}
136
137func prfForVersion(version uint16, suite *cipherSuite) func(result, secret, label, seed []byte) {
138	prf, _ := prfAndHashForVersion(version, suite)
139	return prf
140}
141
142// masterFromPreMasterSecret generates the master secret from the pre-master
143// secret. See http://tools.ietf.org/html/rfc5246#section-8.1
144func masterFromPreMasterSecret(version uint16, suite *cipherSuite, preMasterSecret, clientRandom, serverRandom []byte) []byte {
145	seed := make([]byte, 0, len(clientRandom)+len(serverRandom))
146	seed = append(seed, clientRandom...)
147	seed = append(seed, serverRandom...)
148
149	masterSecret := make([]byte, masterSecretLength)
150	prfForVersion(version, suite)(masterSecret, preMasterSecret, masterSecretLabel, seed)
151	return masterSecret
152}
153
154// keysFromMasterSecret generates the connection keys from the master
155// secret, given the lengths of the MAC key, cipher key and IV, as defined in
156// RFC 2246, section 6.3.
157func keysFromMasterSecret(version uint16, suite *cipherSuite, masterSecret, clientRandom, serverRandom []byte, macLen, keyLen, ivLen int) (clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV []byte) {
158	seed := make([]byte, 0, len(serverRandom)+len(clientRandom))
159	seed = append(seed, serverRandom...)
160	seed = append(seed, clientRandom...)
161
162	n := 2*macLen + 2*keyLen + 2*ivLen
163	keyMaterial := make([]byte, n)
164	prfForVersion(version, suite)(keyMaterial, masterSecret, keyExpansionLabel, seed)
165	clientMAC = keyMaterial[:macLen]
166	keyMaterial = keyMaterial[macLen:]
167	serverMAC = keyMaterial[:macLen]
168	keyMaterial = keyMaterial[macLen:]
169	clientKey = keyMaterial[:keyLen]
170	keyMaterial = keyMaterial[keyLen:]
171	serverKey = keyMaterial[:keyLen]
172	keyMaterial = keyMaterial[keyLen:]
173	clientIV = keyMaterial[:ivLen]
174	keyMaterial = keyMaterial[ivLen:]
175	serverIV = keyMaterial[:ivLen]
176	return
177}
178
179// lookupTLSHash looks up the corresponding crypto.Hash for a given
180// hash from a TLS SignatureScheme.
181func lookupTLSHash(signatureAlgorithm SignatureScheme) (crypto.Hash, error) {
182	switch signatureAlgorithm {
183	case PKCS1WithSHA1, ECDSAWithSHA1:
184		return crypto.SHA1, nil
185	case PKCS1WithSHA256, PSSWithSHA256, ECDSAWithP256AndSHA256:
186		return crypto.SHA256, nil
187	case PKCS1WithSHA384, PSSWithSHA384, ECDSAWithP384AndSHA384:
188		return crypto.SHA384, nil
189	case PKCS1WithSHA512, PSSWithSHA512, ECDSAWithP521AndSHA512:
190		return crypto.SHA512, nil
191	default:
192		return 0, fmt.Errorf("tls: unsupported signature algorithm: %#04x", signatureAlgorithm)
193	}
194}
195
196func newFinishedHash(version uint16, cipherSuite *cipherSuite) finishedHash {
197	var buffer []byte
198	if version == VersionSSL30 || version >= VersionTLS12 {
199		buffer = []byte{}
200	}
201
202	prf, hash := prfAndHashForVersion(version, cipherSuite)
203	if hash != 0 {
204		return finishedHash{hash.New(), hash.New(), nil, nil, buffer, version, prf}
205	}
206
207	return finishedHash{sha1.New(), sha1.New(), md5.New(), md5.New(), buffer, version, prf}
208}
209
210// A finishedHash calculates the hash of a set of handshake messages suitable
211// for including in a Finished message.
212type finishedHash struct {
213	client hash.Hash
214	server hash.Hash
215
216	// Prior to TLS 1.2, an additional MD5 hash is required.
217	clientMD5 hash.Hash
218	serverMD5 hash.Hash
219
220	// In TLS 1.2, a full buffer is sadly required.
221	buffer []byte
222
223	version uint16
224	prf     func(result, secret, label, seed []byte)
225}
226
227func (h *finishedHash) Write(msg []byte) (n int, err error) {
228	h.client.Write(msg)
229	h.server.Write(msg)
230
231	if h.version < VersionTLS12 {
232		h.clientMD5.Write(msg)
233		h.serverMD5.Write(msg)
234	}
235
236	if h.buffer != nil {
237		h.buffer = append(h.buffer, msg...)
238	}
239
240	return len(msg), nil
241}
242
243func (h finishedHash) Sum() []byte {
244	if h.version >= VersionTLS12 {
245		return h.client.Sum(nil)
246	}
247
248	out := make([]byte, 0, md5.Size+sha1.Size)
249	out = h.clientMD5.Sum(out)
250	return h.client.Sum(out)
251}
252
253// finishedSum30 calculates the contents of the verify_data member of a SSLv3
254// Finished message given the MD5 and SHA1 hashes of a set of handshake
255// messages.
256func finishedSum30(md5, sha1 hash.Hash, masterSecret []byte, magic []byte) []byte {
257	md5.Write(magic)
258	md5.Write(masterSecret)
259	md5.Write(ssl30Pad1[:])
260	md5Digest := md5.Sum(nil)
261
262	md5.Reset()
263	md5.Write(masterSecret)
264	md5.Write(ssl30Pad2[:])
265	md5.Write(md5Digest)
266	md5Digest = md5.Sum(nil)
267
268	sha1.Write(magic)
269	sha1.Write(masterSecret)
270	sha1.Write(ssl30Pad1[:40])
271	sha1Digest := sha1.Sum(nil)
272
273	sha1.Reset()
274	sha1.Write(masterSecret)
275	sha1.Write(ssl30Pad2[:40])
276	sha1.Write(sha1Digest)
277	sha1Digest = sha1.Sum(nil)
278
279	ret := make([]byte, len(md5Digest)+len(sha1Digest))
280	copy(ret, md5Digest)
281	copy(ret[len(md5Digest):], sha1Digest)
282	return ret
283}
284
285var ssl3ClientFinishedMagic = [4]byte{0x43, 0x4c, 0x4e, 0x54}
286var ssl3ServerFinishedMagic = [4]byte{0x53, 0x52, 0x56, 0x52}
287
288// clientSum returns the contents of the verify_data member of a client's
289// Finished message.
290func (h finishedHash) clientSum(masterSecret []byte) []byte {
291	if h.version == VersionSSL30 {
292		return finishedSum30(h.clientMD5, h.client, masterSecret, ssl3ClientFinishedMagic[:])
293	}
294
295	out := make([]byte, finishedVerifyLength)
296	h.prf(out, masterSecret, clientFinishedLabel, h.Sum())
297	return out
298}
299
300// serverSum returns the contents of the verify_data member of a server's
301// Finished message.
302func (h finishedHash) serverSum(masterSecret []byte) []byte {
303	if h.version == VersionSSL30 {
304		return finishedSum30(h.serverMD5, h.server, masterSecret, ssl3ServerFinishedMagic[:])
305	}
306
307	out := make([]byte, finishedVerifyLength)
308	h.prf(out, masterSecret, serverFinishedLabel, h.Sum())
309	return out
310}
311
312// selectClientCertSignatureAlgorithm returns a SignatureScheme to sign a
313// client's CertificateVerify with, or an error if none can be found.
314func (h finishedHash) selectClientCertSignatureAlgorithm(serverList []SignatureScheme, sigType uint8) (SignatureScheme, error) {
315	for _, v := range serverList {
316		if signatureFromSignatureScheme(v) == sigType && isSupportedSignatureAlgorithm(v, supportedSignatureAlgorithms) {
317			return v, nil
318		}
319	}
320	return 0, errors.New("tls: no supported signature algorithm found for signing client certificate")
321}
322
323// hashForClientCertificate returns a digest, hash function, and TLS 1.2 hash
324// id suitable for signing by a TLS client certificate.
325func (h finishedHash) hashForClientCertificate(sigType uint8, signatureAlgorithm SignatureScheme, masterSecret []byte) ([]byte, crypto.Hash, error) {
326	if (h.version == VersionSSL30 || h.version >= VersionTLS12) && h.buffer == nil {
327		panic("a handshake hash for a client-certificate was requested after discarding the handshake buffer")
328	}
329
330	if h.version == VersionSSL30 {
331		if sigType != signatureRSA {
332			return nil, 0, errors.New("tls: unsupported signature type for client certificate")
333		}
334
335		md5Hash := md5.New()
336		md5Hash.Write(h.buffer)
337		sha1Hash := sha1.New()
338		sha1Hash.Write(h.buffer)
339		return finishedSum30(md5Hash, sha1Hash, masterSecret, nil), crypto.MD5SHA1, nil
340	}
341	if h.version >= VersionTLS12 {
342		hashAlg, err := lookupTLSHash(signatureAlgorithm)
343		if err != nil {
344			return nil, 0, err
345		}
346		hash := hashAlg.New()
347		hash.Write(h.buffer)
348		return hash.Sum(nil), hashAlg, nil
349	}
350
351	if sigType == signatureECDSA {
352		return h.server.Sum(nil), crypto.SHA1, nil
353	}
354
355	return h.Sum(), crypto.MD5SHA1, nil
356}
357
358// discardHandshakeBuffer is called when there is no more need to
359// buffer the entirety of the handshake messages.
360func (h *finishedHash) discardHandshakeBuffer() {
361	h.buffer = nil
362}
363