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e172d60d BM |
1 | /* ==================================================================== |
2 | * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED. | |
3 | * | |
4 | * The Elliptic Curve Public-Key Crypto Library (ECC Code) included | |
5 | * herein is developed by SUN MICROSYSTEMS, INC., and is contributed | |
6 | * to the OpenSSL project. | |
7 | * | |
8 | * The ECC Code is licensed pursuant to the OpenSSL open source | |
9 | * license provided below. | |
10 | * | |
e172d60d BM |
11 | * The ECDH software is originally written by Douglas Stebila of |
12 | * Sun Microsystems Laboratories. | |
13 | * | |
14 | */ | |
15 | /* ==================================================================== | |
176f31dd | 16 | * Copyright (c) 1998-2003 The OpenSSL Project. All rights reserved. |
e172d60d BM |
17 | * |
18 | * Redistribution and use in source and binary forms, with or without | |
19 | * modification, are permitted provided that the following conditions | |
20 | * are met: | |
21 | * | |
22 | * 1. Redistributions of source code must retain the above copyright | |
0f113f3e | 23 | * notice, this list of conditions and the following disclaimer. |
e172d60d BM |
24 | * |
25 | * 2. Redistributions in binary form must reproduce the above copyright | |
26 | * notice, this list of conditions and the following disclaimer in | |
27 | * the documentation and/or other materials provided with the | |
28 | * distribution. | |
29 | * | |
30 | * 3. All advertising materials mentioning features or use of this | |
31 | * software must display the following acknowledgment: | |
32 | * "This product includes software developed by the OpenSSL Project | |
33 | * for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)" | |
34 | * | |
35 | * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to | |
36 | * endorse or promote products derived from this software without | |
37 | * prior written permission. For written permission, please contact | |
38 | * openssl-core@OpenSSL.org. | |
39 | * | |
40 | * 5. Products derived from this software may not be called "OpenSSL" | |
41 | * nor may "OpenSSL" appear in their names without prior written | |
42 | * permission of the OpenSSL Project. | |
43 | * | |
44 | * 6. Redistributions of any form whatsoever must retain the following | |
45 | * acknowledgment: | |
46 | * "This product includes software developed by the OpenSSL Project | |
47 | * for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)" | |
48 | * | |
49 | * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY | |
50 | * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
51 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR | |
52 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR | |
53 | * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
54 | * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
55 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; | |
56 | * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
57 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, | |
58 | * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) | |
59 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED | |
60 | * OF THE POSSIBILITY OF SUCH DAMAGE. | |
61 | * ==================================================================== | |
62 | * | |
63 | * This product includes cryptographic software written by Eric Young | |
64 | * (eay@cryptsoft.com). This product includes software written by Tim | |
65 | * Hudson (tjh@cryptsoft.com). | |
66 | * | |
67 | */ | |
68 | ||
8b5bcef7 | 69 | #include <string.h> |
176f31dd BM |
70 | #include <limits.h> |
71 | ||
b39fc560 | 72 | #include "internal/cryptlib.h" |
10a66ad3 | 73 | |
e172d60d | 74 | #include <openssl/err.h> |
0f814687 | 75 | #include <openssl/bn.h> |
647b2238 DSH |
76 | #include <openssl/objects.h> |
77 | #include <openssl/ec.h> | |
78 | #include "ec_lcl.h" | |
e172d60d | 79 | |
3a83462d MC |
80 | /*- |
81 | * This implementation is based on the following primitives in the IEEE 1363 standard: | |
e172d60d BM |
82 | * - ECKAS-DH1 |
83 | * - ECSVDP-DH | |
176f31dd | 84 | * Finally an optional KDF is applied. |
e172d60d | 85 | */ |
647b2238 | 86 | int ossl_ecdh_compute_key(void *out, size_t outlen, const EC_POINT *pub_key, |
2c61a5ec | 87 | const EC_KEY *ecdh, |
647b2238 DSH |
88 | void *(*KDF) (const void *in, size_t inlen, |
89 | void *out, size_t *outlen)) | |
0f113f3e MC |
90 | { |
91 | BN_CTX *ctx; | |
92 | EC_POINT *tmp = NULL; | |
93 | BIGNUM *x = NULL, *y = NULL; | |
94 | const BIGNUM *priv_key; | |
95 | const EC_GROUP *group; | |
96 | int ret = -1; | |
97 | size_t buflen, len; | |
98 | unsigned char *buf = NULL; | |
99 | ||
100 | if (outlen > INT_MAX) { | |
647b2238 | 101 | ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); /* sort of, |
0f113f3e MC |
102 | * anyway */ |
103 | return -1; | |
104 | } | |
105 | ||
106 | if ((ctx = BN_CTX_new()) == NULL) | |
107 | goto err; | |
108 | BN_CTX_start(ctx); | |
109 | x = BN_CTX_get(ctx); | |
110 | y = BN_CTX_get(ctx); | |
111 | ||
112 | priv_key = EC_KEY_get0_private_key(ecdh); | |
113 | if (priv_key == NULL) { | |
647b2238 | 114 | ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, EC_R_NO_PRIVATE_VALUE); |
0f113f3e MC |
115 | goto err; |
116 | } | |
117 | ||
118 | group = EC_KEY_get0_group(ecdh); | |
119 | ||
120 | if (EC_KEY_get_flags(ecdh) & EC_FLAG_COFACTOR_ECDH) { | |
a773b52a | 121 | if (!EC_GROUP_get_cofactor(group, x, NULL) || |
0f113f3e | 122 | !BN_mul(x, x, priv_key, ctx)) { |
647b2238 | 123 | ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); |
0f113f3e MC |
124 | goto err; |
125 | } | |
126 | priv_key = x; | |
127 | } | |
128 | ||
129 | if ((tmp = EC_POINT_new(group)) == NULL) { | |
647b2238 | 130 | ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); |
0f113f3e MC |
131 | goto err; |
132 | } | |
133 | ||
134 | if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv_key, ctx)) { | |
647b2238 | 135 | ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, EC_R_POINT_ARITHMETIC_FAILURE); |
0f113f3e MC |
136 | goto err; |
137 | } | |
138 | ||
139 | if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) == | |
140 | NID_X9_62_prime_field) { | |
141 | if (!EC_POINT_get_affine_coordinates_GFp(group, tmp, x, y, ctx)) { | |
647b2238 | 142 | ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, EC_R_POINT_ARITHMETIC_FAILURE); |
0f113f3e MC |
143 | goto err; |
144 | } | |
145 | } | |
b3310161 | 146 | #ifndef OPENSSL_NO_EC2M |
0f113f3e MC |
147 | else { |
148 | if (!EC_POINT_get_affine_coordinates_GF2m(group, tmp, x, y, ctx)) { | |
647b2238 | 149 | ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, EC_R_POINT_ARITHMETIC_FAILURE); |
0f113f3e MC |
150 | goto err; |
151 | } | |
152 | } | |
b3310161 | 153 | #endif |
e172d60d | 154 | |
0f113f3e MC |
155 | buflen = (EC_GROUP_get_degree(group) + 7) / 8; |
156 | len = BN_num_bytes(x); | |
157 | if (len > buflen) { | |
647b2238 | 158 | ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, ERR_R_INTERNAL_ERROR); |
0f113f3e MC |
159 | goto err; |
160 | } | |
161 | if ((buf = OPENSSL_malloc(buflen)) == NULL) { | |
647b2238 | 162 | ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); |
0f113f3e MC |
163 | goto err; |
164 | } | |
165 | ||
166 | memset(buf, 0, buflen - len); | |
167 | if (len != (size_t)BN_bn2bin(x, buf + buflen - len)) { | |
647b2238 | 168 | ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, ERR_R_BN_LIB); |
0f113f3e MC |
169 | goto err; |
170 | } | |
171 | ||
172 | if (KDF != 0) { | |
173 | if (KDF(buf, buflen, out, &outlen) == NULL) { | |
647b2238 | 174 | ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, EC_R_KDF_FAILED); |
0f113f3e MC |
175 | goto err; |
176 | } | |
177 | ret = outlen; | |
178 | } else { | |
179 | /* no KDF, just copy as much as we can */ | |
180 | if (outlen > buflen) | |
181 | outlen = buflen; | |
182 | memcpy(out, buf, outlen); | |
183 | ret = outlen; | |
184 | } | |
185 | ||
186 | err: | |
8fdc3734 | 187 | EC_POINT_free(tmp); |
0f113f3e MC |
188 | if (ctx) |
189 | BN_CTX_end(ctx); | |
23a1d5e9 | 190 | BN_CTX_free(ctx); |
b548a1f1 | 191 | OPENSSL_free(buf); |
0f113f3e MC |
192 | return (ret); |
193 | } |