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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/digest.h>
56 #include <openssl/hmac.h>
57 #include <openssl/mem.h>
58 
59 #include "internal.h"
60 #include "../../internal.h"
61 
62 
63 // tls1_P_hash computes the TLS P_<hash> function as described in RFC 5246,
64 // section 5. It XORs |out_len| bytes to |out|, using |md| as the hash and
65 // |secret| as the secret. |label|, |seed1|, and |seed2| are concatenated to
66 // form the seed parameter. It returns true on success and false on failure.
tls1_P_hash(uint8_t * out,size_t out_len,const EVP_MD * md,const uint8_t * secret,size_t secret_len,const char * label,size_t label_len,const uint8_t * seed1,size_t seed1_len,const uint8_t * seed2,size_t seed2_len)67 static int tls1_P_hash(uint8_t *out, size_t out_len,
68                        const EVP_MD *md,
69                        const uint8_t *secret, size_t secret_len,
70                        const char *label, size_t label_len,
71                        const uint8_t *seed1, size_t seed1_len,
72                        const uint8_t *seed2, size_t seed2_len) {
73   HMAC_CTX ctx, ctx_tmp, ctx_init;
74   uint8_t A1[EVP_MAX_MD_SIZE];
75   unsigned A1_len;
76   int ret = 0;
77 
78   const size_t chunk = EVP_MD_size(md);
79   HMAC_CTX_init(&ctx);
80   HMAC_CTX_init(&ctx_tmp);
81   HMAC_CTX_init(&ctx_init);
82 
83   if (!HMAC_Init_ex(&ctx_init, secret, secret_len, md, NULL) ||
84       !HMAC_CTX_copy_ex(&ctx, &ctx_init) ||
85       !HMAC_Update(&ctx, (const uint8_t *) label, label_len) ||
86       !HMAC_Update(&ctx, seed1, seed1_len) ||
87       !HMAC_Update(&ctx, seed2, seed2_len) ||
88       !HMAC_Final(&ctx, A1, &A1_len)) {
89     goto err;
90   }
91 
92   for (;;) {
93     unsigned len;
94     uint8_t hmac[EVP_MAX_MD_SIZE];
95     if (!HMAC_CTX_copy_ex(&ctx, &ctx_init) ||
96         !HMAC_Update(&ctx, A1, A1_len) ||
97         // Save a copy of |ctx| to compute the next A1 value below.
98         (out_len > chunk && !HMAC_CTX_copy_ex(&ctx_tmp, &ctx)) ||
99         !HMAC_Update(&ctx, (const uint8_t *) label, label_len) ||
100         !HMAC_Update(&ctx, seed1, seed1_len) ||
101         !HMAC_Update(&ctx, seed2, seed2_len) ||
102         !HMAC_Final(&ctx, hmac, &len)) {
103       goto err;
104     }
105     assert(len == chunk);
106 
107     // XOR the result into |out|.
108     if (len > out_len) {
109       len = out_len;
110     }
111     for (unsigned i = 0; i < len; i++) {
112       out[i] ^= hmac[i];
113     }
114     out += len;
115     out_len -= len;
116 
117     if (out_len == 0) {
118       break;
119     }
120 
121     // Calculate the next A1 value.
122     if (!HMAC_Final(&ctx_tmp, A1, &A1_len)) {
123       goto err;
124     }
125   }
126 
127   ret = 1;
128 
129 err:
130   OPENSSL_cleanse(A1, sizeof(A1));
131   HMAC_CTX_cleanup(&ctx);
132   HMAC_CTX_cleanup(&ctx_tmp);
133   HMAC_CTX_cleanup(&ctx_init);
134   return ret;
135 }
136 
CRYPTO_tls1_prf(const EVP_MD * digest,uint8_t * out,size_t out_len,const uint8_t * secret,size_t secret_len,const char * label,size_t label_len,const uint8_t * seed1,size_t seed1_len,const uint8_t * seed2,size_t seed2_len)137 int CRYPTO_tls1_prf(const EVP_MD *digest,
138                     uint8_t *out, size_t out_len,
139                     const uint8_t *secret, size_t secret_len,
140                     const char *label, size_t label_len,
141                     const uint8_t *seed1, size_t seed1_len,
142                     const uint8_t *seed2, size_t seed2_len) {
143   if (out_len == 0) {
144     return 1;
145   }
146 
147   OPENSSL_memset(out, 0, out_len);
148 
149   if (digest == EVP_md5_sha1()) {
150     // If using the MD5/SHA1 PRF, |secret| is partitioned between MD5 and SHA-1.
151     size_t secret_half = secret_len - (secret_len / 2);
152     if (!tls1_P_hash(out, out_len, EVP_md5(), secret, secret_half, label,
153                      label_len, seed1, seed1_len, seed2, seed2_len)) {
154       return 0;
155     }
156 
157     // Note that, if |secret_len| is odd, the two halves share a byte.
158     secret += secret_len - secret_half;
159     secret_len = secret_half;
160     digest = EVP_sha1();
161   }
162 
163   return tls1_P_hash(out, out_len, digest, secret, secret_len, label, label_len,
164                      seed1, seed1_len, seed2, seed2_len);
165 }
166