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 * 11 * The ECDH software is originally written by Douglas Stebila of 12 * Sun Microsystems Laboratories. 13 * 14 */ 15 /* ==================================================================== 16 * Copyright (c) 2000-2002 The OpenSSL Project. All rights reserved. 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 23 * notice, this list of conditions and the following disclaimer. 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 * licensing (at) 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 (at) cryptsoft.com). This product includes software written by Tim 65 * Hudson (tjh (at) cryptsoft.com). */ 66 67 #include <openssl/ecdh.h> 68 69 #include <openssl/bn.h> 70 #include <openssl/digest.h> 71 #include <openssl/err.h> 72 #include <openssl/mem.h> 73 74 75 int ECDH_compute_key(void *out, size_t outlen, const EC_POINT *pub_key, 76 EC_KEY *priv_key, void *(*KDF)(const void *in, size_t inlen, 77 void *out, size_t *outlen)) { 78 BN_CTX *ctx; 79 EC_POINT *tmp = NULL; 80 BIGNUM *x = NULL, *y = NULL; 81 const BIGNUM *priv; 82 const EC_GROUP *group; 83 int ret = -1; 84 size_t buflen, len; 85 uint8_t *buf = NULL; 86 87 if ((ctx = BN_CTX_new()) == NULL) { 88 goto err; 89 } 90 BN_CTX_start(ctx); 91 x = BN_CTX_get(ctx); 92 y = BN_CTX_get(ctx); 93 94 priv = EC_KEY_get0_private_key(priv_key); 95 if (priv == NULL) { 96 OPENSSL_PUT_ERROR(ECDH, ECDH_compute_key, ECDH_R_NO_PRIVATE_VALUE); 97 goto err; 98 } 99 100 group = EC_KEY_get0_group(priv_key); 101 102 tmp = EC_POINT_new(group); 103 if (tmp == NULL) { 104 OPENSSL_PUT_ERROR(ECDH, ECDH_compute_key, ERR_R_MALLOC_FAILURE); 105 goto err; 106 } 107 108 if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv, ctx)) { 109 OPENSSL_PUT_ERROR(ECDH, ECDH_compute_key, ECDH_R_POINT_ARITHMETIC_FAILURE); 110 goto err; 111 } 112 113 if (!EC_POINT_get_affine_coordinates_GFp(group, tmp, x, y, ctx)) { 114 OPENSSL_PUT_ERROR(ECDH, ECDH_compute_key, ECDH_R_POINT_ARITHMETIC_FAILURE); 115 goto err; 116 } 117 118 buflen = (EC_GROUP_get_degree(group) + 7) / 8; 119 len = BN_num_bytes(x); 120 if (len > buflen) { 121 OPENSSL_PUT_ERROR(ECDH, ECDH_compute_key, ERR_R_INTERNAL_ERROR); 122 goto err; 123 } 124 buf = OPENSSL_malloc(buflen); 125 if (buf == NULL) { 126 OPENSSL_PUT_ERROR(ECDH, ECDH_compute_key, ERR_R_MALLOC_FAILURE); 127 goto err; 128 } 129 130 memset(buf, 0, buflen - len); 131 if (len != (size_t)BN_bn2bin(x, buf + buflen - len)) { 132 OPENSSL_PUT_ERROR(ECDH, ECDH_compute_key, ERR_R_BN_LIB); 133 goto err; 134 } 135 136 if (KDF != 0) { 137 if (KDF(buf, buflen, out, &outlen) == NULL) { 138 OPENSSL_PUT_ERROR(ECDH, ECDH_compute_key, ECDH_R_KDF_FAILED); 139 goto err; 140 } 141 ret = outlen; 142 } else { 143 /* no KDF, just copy as much as we can */ 144 if (outlen > buflen) { 145 outlen = buflen; 146 } 147 memcpy(out, buf, outlen); 148 ret = outlen; 149 } 150 151 err: 152 if (tmp) 153 EC_POINT_free(tmp); 154 if (ctx) 155 BN_CTX_end(ctx); 156 if (ctx) 157 BN_CTX_free(ctx); 158 if (buf) 159 OPENSSL_free(buf); 160 return ret; 161 } 162 163 /* Key derivation function from X9.62/SECG */ 164 /* Way more than we will ever need */ 165 #define ECDH_KDF_MAX (1 << 30) 166 167 int ECDH_KDF_X9_62(uint8_t *out, size_t outlen, const uint8_t *Z, 168 size_t Zlen, const uint8_t *sinfo, size_t sinfolen, 169 const EVP_MD *md) { 170 EVP_MD_CTX mctx; 171 int rv = 0; 172 unsigned int i; 173 size_t mdlen; 174 uint8_t ctr[4]; 175 176 if (sinfolen > ECDH_KDF_MAX || outlen > ECDH_KDF_MAX || Zlen > ECDH_KDF_MAX) { 177 return 0; 178 } 179 mdlen = EVP_MD_size(md); 180 EVP_MD_CTX_init(&mctx); 181 182 for (i = 1;; i++) { 183 uint8_t mtmp[EVP_MAX_MD_SIZE]; 184 EVP_DigestInit_ex(&mctx, md, NULL); 185 ctr[3] = i & 0xFF; 186 ctr[2] = (i >> 8) & 0xFF; 187 ctr[1] = (i >> 16) & 0xFF; 188 ctr[0] = (i >> 24) & 0xFF; 189 if (!EVP_DigestUpdate(&mctx, Z, Zlen) || 190 !EVP_DigestUpdate(&mctx, ctr, sizeof(ctr)) || 191 !EVP_DigestUpdate(&mctx, sinfo, sinfolen)) { 192 goto err; 193 } 194 195 if (outlen >= mdlen) { 196 if (!EVP_DigestFinal(&mctx, out, NULL)) { 197 goto err; 198 } 199 outlen -= mdlen; 200 if (outlen == 0) { 201 break; 202 } 203 out += mdlen; 204 } else { 205 if (!EVP_DigestFinal(&mctx, mtmp, NULL)) { 206 goto err; 207 } 208 memcpy(out, mtmp, outlen); 209 OPENSSL_cleanse(mtmp, mdlen); 210 break; 211 } 212 } 213 rv = 1; 214 215 err: 216 EVP_MD_CTX_cleanup(&mctx); 217 return rv; 218 } 219
