ech_ossl.c revision 296465 
1/* crypto/ecdh/ech_ossl.c */
2/* ====================================================================
3 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
4 *
5 * The Elliptic Curve Public-Key Crypto Library (ECC Code) included
6 * herein is developed by SUN MICROSYSTEMS, INC., and is contributed
7 * to the OpenSSL project.
8 *
9 * The ECC Code is licensed pursuant to the OpenSSL open source
10 * license provided below.
11 *
12 * The ECDH software is originally written by Douglas Stebila of
13 * Sun Microsystems Laboratories.
14 *
15 */
16/* ====================================================================
17 * Copyright (c) 1998-2003 The OpenSSL Project.  All rights reserved.
18 *
19 * Redistribution and use in source and binary forms, with or without
20 * modification, are permitted provided that the following conditions
21 * are met:
22 *
23 * 1. Redistributions of source code must retain the above copyright
24 *    notice, this list of conditions and the following disclaimer.
25 *
26 * 2. Redistributions in binary form must reproduce the above copyright
27 *    notice, this list of conditions and the following disclaimer in
28 *    the documentation and/or other materials provided with the
29 *    distribution.
30 *
31 * 3. All advertising materials mentioning features or use of this
32 *    software must display the following acknowledgment:
33 *    "This product includes software developed by the OpenSSL Project
34 *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
35 *
36 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
37 *    endorse or promote products derived from this software without
38 *    prior written permission. For written permission, please contact
39 *    openssl-core@OpenSSL.org.
40 *
41 * 5. Products derived from this software may not be called "OpenSSL"
42 *    nor may "OpenSSL" appear in their names without prior written
43 *    permission of the OpenSSL Project.
44 *
45 * 6. Redistributions of any form whatsoever must retain the following
46 *    acknowledgment:
47 *    "This product includes software developed by the OpenSSL Project
48 *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
49 *
50 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
51 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
52 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
53 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
54 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
55 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
56 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
57 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
58 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
59 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
60 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
61 * OF THE POSSIBILITY OF SUCH DAMAGE.
62 * ====================================================================
63 *
64 * This product includes cryptographic software written by Eric Young
65 * (eay@cryptsoft.com).  This product includes software written by Tim
66 * Hudson (tjh@cryptsoft.com).
67 *
68 */
69
70#include <string.h>
71#include <limits.h>
72
73#include "cryptlib.h"
74
75#include "ech_locl.h"
76#include <openssl/err.h>
77#include <openssl/sha.h>
78#include <openssl/obj_mac.h>
79#include <openssl/bn.h>
80
81static int ecdh_compute_key(void *out, size_t len, const EC_POINT *pub_key,
82                            EC_KEY *ecdh,
83                            void *(*KDF) (const void *in, size_t inlen,
84                                          void *out, size_t *outlen));
85
86static ECDH_METHOD openssl_ecdh_meth = {
87    "OpenSSL ECDH method",
88    ecdh_compute_key,
89#if 0
90    NULL,                       /* init */
91    NULL,                       /* finish */
92#endif
93    0,                          /* flags */
94    NULL                        /* app_data */
95};
96
97const ECDH_METHOD *ECDH_OpenSSL(void)
98{
99    return &openssl_ecdh_meth;
100}
101
102/*-
103 * This implementation is based on the following primitives in the IEEE 1363 standard:
104 *  - ECKAS-DH1
105 *  - ECSVDP-DH
106 * Finally an optional KDF is applied.
107 */
108static int ecdh_compute_key(void *out, size_t outlen, const EC_POINT *pub_key,
109                            EC_KEY *ecdh,
110                            void *(*KDF) (const void *in, size_t inlen,
111                                          void *out, size_t *outlen))
112{
113    BN_CTX *ctx;
114    EC_POINT *tmp = NULL;
115    BIGNUM *x = NULL, *y = NULL;
116    const BIGNUM *priv_key;
117    const EC_GROUP *group;
118    int ret = -1;
119    size_t buflen, len;
120    unsigned char *buf = NULL;
121
122    if (outlen > INT_MAX) {
123        ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); /* sort of,
124                                                                 * anyway */
125        return -1;
126    }
127
128    if ((ctx = BN_CTX_new()) == NULL)
129        goto err;
130    BN_CTX_start(ctx);
131    x = BN_CTX_get(ctx);
132    y = BN_CTX_get(ctx);
133
134    priv_key = EC_KEY_get0_private_key(ecdh);
135    if (priv_key == NULL) {
136        ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_NO_PRIVATE_VALUE);
137        goto err;
138    }
139
140    group = EC_KEY_get0_group(ecdh);
141    if ((tmp = EC_POINT_new(group)) == NULL) {
142        ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
143        goto err;
144    }
145
146    if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv_key, ctx)) {
147        ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_POINT_ARITHMETIC_FAILURE);
148        goto err;
149    }
150
151    if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
152        NID_X9_62_prime_field) {
153        if (!EC_POINT_get_affine_coordinates_GFp(group, tmp, x, y, ctx)) {
154            ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_POINT_ARITHMETIC_FAILURE);
155            goto err;
156        }
157    } else {
158        if (!EC_POINT_get_affine_coordinates_GF2m(group, tmp, x, y, ctx)) {
159            ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_POINT_ARITHMETIC_FAILURE);
160            goto err;
161        }
162    }
163
164    buflen = (EC_GROUP_get_degree(group) + 7) / 8;
165    len = BN_num_bytes(x);
166    if (len > buflen) {
167        ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_INTERNAL_ERROR);
168        goto err;
169    }
170    if ((buf = OPENSSL_malloc(buflen)) == NULL) {
171        ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
172        goto err;
173    }
174
175    memset(buf, 0, buflen - len);
176    if (len != (size_t)BN_bn2bin(x, buf + buflen - len)) {
177        ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_BN_LIB);
178        goto err;
179    }
180
181    if (KDF != 0) {
182        if (KDF(buf, buflen, out, &outlen) == NULL) {
183            ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_KDF_FAILED);
184            goto err;
185        }
186        ret = outlen;
187    } else {
188        /* no KDF, just copy as much as we can */
189        if (outlen > buflen)
190            outlen = buflen;
191        memcpy(out, buf, outlen);
192        ret = outlen;
193    }
194
195 err:
196    if (tmp)
197        EC_POINT_free(tmp);
198    if (ctx)
199        BN_CTX_end(ctx);
200    if (ctx)
201        BN_CTX_free(ctx);
202    if (buf)
203        OPENSSL_free(buf);
204    return (ret);
205}
206