1/* crypto/ecdh/ec_kdf.c */
2/*
3 * Written by Stephen Henson for the OpenSSL project.
4 */
5/* ====================================================================
6 * Copyright (c) 2013 The OpenSSL Project.  All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 *
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in
17 *    the documentation and/or other materials provided with the
18 *    distribution.
19 *
20 * 3. All advertising materials mentioning features or use of this
21 *    software must display the following acknowledgment:
22 *    "This product includes software developed by the OpenSSL Project
23 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
24 *
25 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
26 *    endorse or promote products derived from this software without
27 *    prior written permission. For written permission, please contact
28 *    openssl-core@openssl.org.
29 *
30 * 5. Products derived from this software may not be called "OpenSSL"
31 *    nor may "OpenSSL" appear in their names without prior written
32 *    permission of the OpenSSL Project.
33 *
34 * 6. Redistributions of any form whatsoever must retain the following
35 *    acknowledgment:
36 *    "This product includes software developed by the OpenSSL Project
37 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
38 *
39 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
40 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
41 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
42 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
43 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
44 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
45 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
46 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
48 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
49 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
50 * OF THE POSSIBILITY OF SUCH DAMAGE.
51 * ====================================================================
52 */
53
54#define OPENSSL_FIPSAPI
55
56#include <string.h>
57#include <openssl/ecdh.h>
58#include <openssl/evp.h>
59
60/* Key derivation function from X9.62/SECG */
61/* Way more than we will ever need */
62#define ECDH_KDF_MAX    (1 << 30)
63
64int ECDH_KDF_X9_62(unsigned char *out, size_t outlen,
65                   const unsigned char *Z, size_t Zlen,
66                   const unsigned char *sinfo, size_t sinfolen,
67                   const EVP_MD *md)
68{
69    EVP_MD_CTX mctx;
70    int rv = 0;
71    unsigned int i;
72    size_t mdlen;
73    unsigned char ctr[4];
74    if (sinfolen > ECDH_KDF_MAX || outlen > ECDH_KDF_MAX
75        || Zlen > ECDH_KDF_MAX)
76        return 0;
77    mdlen = EVP_MD_size(md);
78    EVP_MD_CTX_init(&mctx);
79    for (i = 1;; i++) {
80        unsigned char mtmp[EVP_MAX_MD_SIZE];
81        EVP_DigestInit_ex(&mctx, md, NULL);
82        ctr[3] = i & 0xFF;
83        ctr[2] = (i >> 8) & 0xFF;
84        ctr[1] = (i >> 16) & 0xFF;
85        ctr[0] = (i >> 24) & 0xFF;
86        if (!EVP_DigestUpdate(&mctx, Z, Zlen))
87            goto err;
88        if (!EVP_DigestUpdate(&mctx, ctr, sizeof(ctr)))
89            goto err;
90        if (!EVP_DigestUpdate(&mctx, sinfo, sinfolen))
91            goto err;
92        if (outlen >= mdlen) {
93            if (!EVP_DigestFinal(&mctx, out, NULL))
94                goto err;
95            outlen -= mdlen;
96            if (outlen == 0)
97                break;
98            out += mdlen;
99        } else {
100            if (!EVP_DigestFinal(&mctx, mtmp, NULL))
101                goto err;
102            memcpy(out, mtmp, outlen);
103            OPENSSL_cleanse(mtmp, mdlen);
104            break;
105        }
106    }
107    rv = 1;
108 err:
109    EVP_MD_CTX_cleanup(&mctx);
110    return rv;
111}
112