1/* ====================================================================
2 * Copyright (c) 1998-2007 The OpenSSL Project.  All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 *
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in
13 *    the documentation and/or other materials provided with the
14 *    distribution.
15 *
16 * 3. All advertising materials mentioning features or use of this
17 *    software must display the following acknowledgment:
18 *    "This product includes software developed by the OpenSSL Project
19 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
20 *
21 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
22 *    endorse or promote products derived from this software without
23 *    prior written permission. For written permission, please contact
24 *    openssl-core@openssl.org.
25 *
26 * 5. Products derived from this software may not be called "OpenSSL"
27 *    nor may "OpenSSL" appear in their names without prior written
28 *    permission of the OpenSSL Project.
29 *
30 * 6. Redistributions of any form whatsoever must retain the following
31 *    acknowledgment:
32 *    "This product includes software developed by the OpenSSL Project
33 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
34 *
35 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
36 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
37 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
38 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
39 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
40 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
41 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
42 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
43 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
44 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
45 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
46 * OF THE POSSIBILITY OF SUCH DAMAGE.
47 * ====================================================================
48 *
49 * This product includes cryptographic software written by Eric Young
50 * (eay@cryptsoft.com).  This product includes software written by Tim
51 * Hudson (tjh@cryptsoft.com). */
52
53#include <assert.h>
54
55#include <openssl/hmac.h>
56#include <openssl/mem.h>
57
58#include "internal.h"
59#include "../crypto/internal.h"
60
61
62// tls1_P_hash computes the TLS P_<hash> function as described in RFC 5246,
63// section 5. It XORs |out_len| bytes to |out|, using |md| as the hash and
64// |secret| as the secret. |label|, |seed1|, and |seed2| are concatenated to
65// form the seed parameter. It returns true on success and false on failure.
66static int tls1_P_hash(uint8_t *out, size_t out_len,
67                       const EVP_MD *md,
68                       const uint8_t *secret, size_t secret_len,
69                       const char *label, size_t label_len,
70                       const uint8_t *seed1, size_t seed1_len,
71                       const uint8_t *seed2, size_t seed2_len) {
72  HMAC_CTX ctx, ctx_tmp, ctx_init;
73  uint8_t A1[EVP_MAX_MD_SIZE];
74  unsigned A1_len;
75  int ret = 0;
76
77  const size_t chunk = EVP_MD_size(md);
78  HMAC_CTX_init(&ctx);
79  HMAC_CTX_init(&ctx_tmp);
80  HMAC_CTX_init(&ctx_init);
81
82  if (!HMAC_Init_ex(&ctx_init, secret, secret_len, md, NULL) ||
83      !HMAC_CTX_copy_ex(&ctx, &ctx_init) ||
84      !HMAC_Update(&ctx, (const uint8_t *) label, label_len) ||
85      !HMAC_Update(&ctx, seed1, seed1_len) ||
86      !HMAC_Update(&ctx, seed2, seed2_len) ||
87      !HMAC_Final(&ctx, A1, &A1_len)) {
88    goto err;
89  }
90
91  for (;;) {
92    unsigned len;
93    uint8_t hmac[EVP_MAX_MD_SIZE];
94    if (!HMAC_CTX_copy_ex(&ctx, &ctx_init) ||
95        !HMAC_Update(&ctx, A1, A1_len) ||
96        // Save a copy of |ctx| to compute the next A1 value below.
97        (out_len > chunk && !HMAC_CTX_copy_ex(&ctx_tmp, &ctx)) ||
98        !HMAC_Update(&ctx, (const uint8_t *) label, label_len) ||
99        !HMAC_Update(&ctx, seed1, seed1_len) ||
100        !HMAC_Update(&ctx, seed2, seed2_len) ||
101        !HMAC_Final(&ctx, hmac, &len)) {
102      goto err;
103    }
104    assert(len == chunk);
105
106    // XOR the result into |out|.
107    if (len > out_len) {
108      len = out_len;
109    }
110    for (unsigned i = 0; i < len; i++) {
111      out[i] ^= hmac[i];
112    }
113    out += len;
114    out_len -= len;
115
116    if (out_len == 0) {
117      break;
118    }
119
120    // Calculate the next A1 value.
121    if (!HMAC_Final(&ctx_tmp, A1, &A1_len)) {
122      goto err;
123    }
124  }
125
126  ret = 1;
127
128err:
129  OPENSSL_cleanse(A1, sizeof(A1));
130  HMAC_CTX_cleanup(&ctx);
131  HMAC_CTX_cleanup(&ctx_tmp);
132  HMAC_CTX_cleanup(&ctx_init);
133  return ret;
134}
135
136int CRYPTO_tls1_prf(const EVP_MD *digest,
137                    uint8_t *out, size_t out_len,
138                    const uint8_t *secret, size_t secret_len,
139                    const char *label, size_t label_len,
140                    const uint8_t *seed1, size_t seed1_len,
141                    const uint8_t *seed2, size_t seed2_len) {
142  if (out_len == 0) {
143    return 1;
144  }
145
146  OPENSSL_memset(out, 0, out_len);
147
148  if (digest == EVP_md5_sha1()) {
149    // If using the MD5/SHA1 PRF, |secret| is partitioned between MD5 and SHA-1.
150    size_t secret_half = secret_len - (secret_len / 2);
151    if (!tls1_P_hash(out, out_len, EVP_md5(), secret, secret_half, label,
152                     label_len, seed1, seed1_len, seed2, seed2_len)) {
153      return 0;
154    }
155
156    // Note that, if |secret_len| is odd, the two halves share a byte.
157    secret += secret_len - secret_half;
158    secret_len = secret_half;
159    digest = EVP_sha1();
160  }
161
162  return tls1_P_hash(out, out_len, digest, secret, secret_len, label, label_len,
163                     seed1, seed1_len, seed2, seed2_len);
164}
165