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 <string.h> 70 71 #include <openssl/bn.h> 72 #include <openssl/digest.h> 73 #include <openssl/err.h> 74 #include <openssl/mem.h> 75 76 77 int ECDH_compute_key(void *out, size_t outlen, const EC_POINT *pub_key, 78 EC_KEY *priv_key, 79 void *(*kdf)(const void *in, size_t inlen, void *out, 80 size_t *outlen)) { 81 const BIGNUM *const priv = EC_KEY_get0_private_key(priv_key); 82 if (priv == NULL) { 83 OPENSSL_PUT_ERROR(ECDH, ECDH_R_NO_PRIVATE_VALUE); 84 return -1; 85 } 86 87 BN_CTX *ctx = BN_CTX_new(); 88 if (ctx == NULL) { 89 return -1; 90 } 91 BN_CTX_start(ctx); 92 93 int ret = -1; 94 size_t buflen = 0; 95 uint8_t *buf = NULL; 96 97 const EC_GROUP *const group = EC_KEY_get0_group(priv_key); 98 EC_POINT *tmp = EC_POINT_new(group); 99 if (tmp == NULL) { 100 OPENSSL_PUT_ERROR(ECDH, ERR_R_MALLOC_FAILURE); 101 goto err; 102 } 103 104 if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv, ctx)) { 105 OPENSSL_PUT_ERROR(ECDH, ECDH_R_POINT_ARITHMETIC_FAILURE); 106 goto err; 107 } 108 109 BIGNUM *x = BN_CTX_get(ctx); 110 if (!x) { 111 OPENSSL_PUT_ERROR(ECDH, ERR_R_MALLOC_FAILURE); 112 goto err; 113 } 114 115 if (!EC_POINT_get_affine_coordinates_GFp(group, tmp, x, NULL, ctx)) { 116 OPENSSL_PUT_ERROR(ECDH, ECDH_R_POINT_ARITHMETIC_FAILURE); 117 goto err; 118 } 119 120 buflen = (EC_GROUP_get_degree(group) + 7) / 8; 121 buf = OPENSSL_malloc(buflen); 122 if (buf == NULL) { 123 OPENSSL_PUT_ERROR(ECDH, ERR_R_MALLOC_FAILURE); 124 goto err; 125 } 126 127 if (!BN_bn2bin_padded(buf, buflen, x)) { 128 OPENSSL_PUT_ERROR(ECDH, ERR_R_INTERNAL_ERROR); 129 goto err; 130 } 131 132 if (kdf != NULL) { 133 if (kdf(buf, buflen, out, &outlen) == NULL) { 134 OPENSSL_PUT_ERROR(ECDH, ECDH_R_KDF_FAILED); 135 goto err; 136 } 137 } else { 138 /* no KDF, just copy as much as we can */ 139 if (buflen < outlen) { 140 outlen = buflen; 141 } 142 memcpy(out, buf, outlen); 143 } 144 145 ret = outlen; 146 147 err: 148 OPENSSL_free(buf); 149 EC_POINT_free(tmp); 150 BN_CTX_end(ctx); 151 BN_CTX_free(ctx); 152 return ret; 153 } 154
