1 /*
2 * Written by Stephen Henson for the OpenSSL project.
3 */
4 /* ====================================================================
5 * Copyright (c) 2013 The OpenSSL Project. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 *
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in
16 * the documentation and/or other materials provided with the
17 * distribution.
18 *
19 * 3. All advertising materials mentioning features or use of this
20 * software must display the following acknowledgment:
21 * "This product includes software developed by the OpenSSL Project
22 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
23 *
24 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
25 * endorse or promote products derived from this software without
26 * prior written permission. For written permission, please contact
27 * openssl-core@openssl.org.
28 *
29 * 5. Products derived from this software may not be called "OpenSSL"
30 * nor may "OpenSSL" appear in their names without prior written
31 * permission of the OpenSSL Project.
32 *
33 * 6. Redistributions of any form whatsoever must retain the following
34 * acknowledgment:
35 * "This product includes software developed by the OpenSSL Project
36 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
37 *
38 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
39 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
40 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
41 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
42 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
43 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
44 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
45 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
46 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
47 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
48 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
49 * OF THE POSSIBILITY OF SUCH DAMAGE.
50 * ====================================================================
51 */
52
53 #include <string.h>
54
55 #include <openssl/ec.h>
56 #include <openssl/evp.h>
57
58 #include "ech_locl.h"
59
60 /*
61 * Key derivation function from X9.63/SECG.
62 */
63
64 /* Way more than we will ever need */
65 #define ECDH_KDF_MAX (1 << 30)
66
67 int
ecdh_KDF_X9_63(unsigned char * out,size_t outlen,const unsigned char * Z,size_t Zlen,const unsigned char * sinfo,size_t sinfolen,const EVP_MD * md)68 ecdh_KDF_X9_63(unsigned char *out, size_t outlen, const unsigned char *Z,
69 size_t Zlen, const unsigned char *sinfo, size_t sinfolen, const EVP_MD *md)
70 {
71 EVP_MD_CTX *mctx = NULL;
72 unsigned int i;
73 size_t mdlen;
74 unsigned char ctr[4];
75 int rv = 0;
76
77 if (sinfolen > ECDH_KDF_MAX || outlen > ECDH_KDF_MAX ||
78 Zlen > ECDH_KDF_MAX)
79 return 0;
80 mctx = EVP_MD_CTX_new();
81 if (mctx == NULL)
82 return 0;
83 mdlen = EVP_MD_size(md);
84 for (i = 1;; i++) {
85 unsigned char mtmp[EVP_MAX_MD_SIZE];
86 if (!EVP_DigestInit_ex(mctx, md, NULL))
87 goto err;
88 ctr[3] = i & 0xFF;
89 ctr[2] = (i >> 8) & 0xFF;
90 ctr[1] = (i >> 16) & 0xFF;
91 ctr[0] = (i >> 24) & 0xFF;
92 if (!EVP_DigestUpdate(mctx, Z, Zlen))
93 goto err;
94 if (!EVP_DigestUpdate(mctx, ctr, sizeof(ctr)))
95 goto err;
96 if (!EVP_DigestUpdate(mctx, sinfo, sinfolen))
97 goto err;
98 if (outlen >= mdlen) {
99 if (!EVP_DigestFinal(mctx, out, NULL))
100 goto err;
101 outlen -= mdlen;
102 if (outlen == 0)
103 break;
104 out += mdlen;
105 } else {
106 if (!EVP_DigestFinal(mctx, mtmp, NULL))
107 goto err;
108 memcpy(out, mtmp, outlen);
109 explicit_bzero(mtmp, mdlen);
110 break;
111 }
112 }
113 rv = 1;
114
115 err:
116 EVP_MD_CTX_free(mctx);
117
118 return rv;
119 }
120