1 /* $OpenBSD: ech_key.c,v 1.5 2015/09/13 14:11:57 jsing Exp $ */ 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 <limits.h> 71 #include <string.h> 72 73 #include <openssl/opensslconf.h> 74 75 #include <openssl/bn.h> 76 #include <openssl/err.h> 77 #include <openssl/obj_mac.h> 78 #include <openssl/sha.h> 79 80 #include "ech_locl.h" 81 82 static int ecdh_compute_key(void *out, size_t len, const EC_POINT *pub_key, 83 EC_KEY *ecdh, 84 void *(*KDF)(const void *in, size_t inlen, void *out, size_t *outlen)); 85 86 /* 87 * This implementation is based on the following primitives in the IEEE 1363 88 * standard: 89 * - ECKAS-DH1 90 * - ECSVDP-DH 91 * Finally an optional KDF is applied. 92 */ 93 static int 94 ecdh_compute_key(void *out, size_t outlen, const EC_POINT *pub_key, 95 EC_KEY *ecdh, 96 void *(*KDF)(const void *in, size_t inlen, void *out, size_t *outlen)) 97 { 98 BN_CTX *ctx; 99 EC_POINT *tmp = NULL; 100 BIGNUM *x = NULL, *y = NULL; 101 const BIGNUM *priv_key; 102 const EC_GROUP* group; 103 int ret = -1; 104 size_t buflen, len; 105 unsigned char *buf = NULL; 106 107 if (outlen > INT_MAX) { 108 /* Sort of, anyway. */ 109 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); 110 return -1; 111 } 112 113 if ((ctx = BN_CTX_new()) == NULL) 114 goto err; 115 BN_CTX_start(ctx); 116 if ((x = BN_CTX_get(ctx)) == NULL) 117 goto err; 118 if ((y = BN_CTX_get(ctx)) == NULL) 119 goto err; 120 121 priv_key = EC_KEY_get0_private_key(ecdh); 122 if (priv_key == NULL) { 123 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_NO_PRIVATE_VALUE); 124 goto err; 125 } 126 127 group = EC_KEY_get0_group(ecdh); 128 if ((tmp = EC_POINT_new(group)) == NULL) { 129 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); 130 goto err; 131 } 132 133 if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv_key, ctx)) { 134 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, 135 ECDH_R_POINT_ARITHMETIC_FAILURE); 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, 142 ctx)) { 143 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, 144 ECDH_R_POINT_ARITHMETIC_FAILURE); 145 goto err; 146 } 147 } 148 #ifndef OPENSSL_NO_EC2M 149 else { 150 if (!EC_POINT_get_affine_coordinates_GF2m(group, tmp, x, y, 151 ctx)) { 152 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, 153 ECDH_R_POINT_ARITHMETIC_FAILURE); 154 goto err; 155 } 156 } 157 #endif 158 159 buflen = ECDH_size(ecdh); 160 len = BN_num_bytes(x); 161 if (len > buflen) { 162 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_INTERNAL_ERROR); 163 goto err; 164 } 165 if (KDF == NULL && outlen < buflen) { 166 /* The resulting key would be truncated. */ 167 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_KEY_TRUNCATION); 168 goto err; 169 } 170 if ((buf = 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 != NULL) { 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 out the key and zero the rest. */ 189 if (outlen > buflen) { 190 memset((void *)((uintptr_t)out + buflen), 0, outlen - buflen); 191 outlen = buflen; 192 } 193 memcpy(out, buf, outlen); 194 ret = outlen; 195 } 196 197 err: 198 EC_POINT_free(tmp); 199 if (ctx) 200 BN_CTX_end(ctx); 201 BN_CTX_free(ctx); 202 free(buf); 203 return (ret); 204 } 205 206 static ECDH_METHOD openssl_ecdh_meth = { 207 .name = "OpenSSL ECDH method", 208 .compute_key = ecdh_compute_key 209 }; 210 211 const ECDH_METHOD * 212 ECDH_OpenSSL(void) 213 { 214 return &openssl_ecdh_meth; 215 } 216 217 int 218 ECDH_compute_key(void *out, size_t outlen, const EC_POINT *pub_key, 219 EC_KEY *eckey, 220 void *(*KDF)(const void *in, size_t inlen, void *out, size_t *outlen)) 221 { 222 ECDH_DATA *ecdh = ecdh_check(eckey); 223 if (ecdh == NULL) 224 return 0; 225 return ecdh->meth->compute_key(out, outlen, pub_key, eckey, KDF); 226 } 227