1 /* $OpenBSD: ech_key.c,v 1.9 2019/01/19 01:12:48 tb 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 #include "ec_lcl.h" 82 83 static int ecdh_compute_key(void *out, size_t len, const EC_POINT *pub_key, 84 EC_KEY *ecdh, 85 void *(*KDF)(const void *in, size_t inlen, void *out, size_t *outlen)); 86 87 /* 88 * This implementation is based on the following primitives in the IEEE 1363 89 * standard: 90 * - ECKAS-DH1 91 * - ECSVDP-DH 92 * Finally an optional KDF is applied. 93 */ 94 static int 95 ecdh_compute_key(void *out, size_t outlen, const EC_POINT *pub_key, 96 EC_KEY *ecdh, 97 void *(*KDF)(const void *in, size_t inlen, void *out, size_t *outlen)) 98 { 99 BN_CTX *ctx; 100 EC_POINT *tmp = NULL; 101 BIGNUM *x = NULL, *y = NULL; 102 const BIGNUM *priv_key; 103 const EC_GROUP* group; 104 int ret = -1; 105 size_t buflen, len; 106 unsigned char *buf = NULL; 107 108 if (outlen > INT_MAX) { 109 /* Sort of, anyway. */ 110 ECDHerror(ERR_R_MALLOC_FAILURE); 111 return -1; 112 } 113 114 if ((ctx = BN_CTX_new()) == NULL) 115 goto err; 116 BN_CTX_start(ctx); 117 if ((x = BN_CTX_get(ctx)) == NULL) 118 goto err; 119 if ((y = BN_CTX_get(ctx)) == NULL) 120 goto err; 121 122 priv_key = EC_KEY_get0_private_key(ecdh); 123 if (priv_key == NULL) { 124 ECDHerror(ECDH_R_NO_PRIVATE_VALUE); 125 goto err; 126 } 127 128 group = EC_KEY_get0_group(ecdh); 129 130 if (!EC_POINT_is_on_curve(group, pub_key, ctx)) 131 goto err; 132 133 if ((tmp = EC_POINT_new(group)) == NULL) { 134 ECDHerror(ERR_R_MALLOC_FAILURE); 135 goto err; 136 } 137 138 if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv_key, ctx)) { 139 ECDHerror(ECDH_R_POINT_ARITHMETIC_FAILURE); 140 goto err; 141 } 142 143 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) == 144 NID_X9_62_prime_field) { 145 if (!EC_POINT_get_affine_coordinates_GFp(group, tmp, x, y, 146 ctx)) { 147 ECDHerror(ECDH_R_POINT_ARITHMETIC_FAILURE); 148 goto err; 149 } 150 } 151 #ifndef OPENSSL_NO_EC2M 152 else { 153 if (!EC_POINT_get_affine_coordinates_GF2m(group, tmp, x, y, 154 ctx)) { 155 ECDHerror(ECDH_R_POINT_ARITHMETIC_FAILURE); 156 goto err; 157 } 158 } 159 #endif 160 161 buflen = ECDH_size(ecdh); 162 len = BN_num_bytes(x); 163 if (len > buflen) { 164 ECDHerror(ERR_R_INTERNAL_ERROR); 165 goto err; 166 } 167 if (KDF == NULL && outlen < buflen) { 168 /* The resulting key would be truncated. */ 169 ECDHerror(ECDH_R_KEY_TRUNCATION); 170 goto err; 171 } 172 if ((buf = malloc(buflen)) == NULL) { 173 ECDHerror(ERR_R_MALLOC_FAILURE); 174 goto err; 175 } 176 177 memset(buf, 0, buflen - len); 178 if (len != (size_t)BN_bn2bin(x, buf + buflen - len)) { 179 ECDHerror(ERR_R_BN_LIB); 180 goto err; 181 } 182 183 if (KDF != NULL) { 184 if (KDF(buf, buflen, out, &outlen) == NULL) { 185 ECDHerror(ECDH_R_KDF_FAILED); 186 goto err; 187 } 188 ret = outlen; 189 } else { 190 /* No KDF, just copy out the key and zero the rest. */ 191 if (outlen > buflen) { 192 memset((void *)((uintptr_t)out + buflen), 0, outlen - buflen); 193 outlen = buflen; 194 } 195 memcpy(out, buf, outlen); 196 ret = outlen; 197 } 198 199 err: 200 EC_POINT_free(tmp); 201 if (ctx) 202 BN_CTX_end(ctx); 203 BN_CTX_free(ctx); 204 free(buf); 205 return (ret); 206 } 207 208 static ECDH_METHOD openssl_ecdh_meth = { 209 .name = "OpenSSL ECDH method", 210 .compute_key = ecdh_compute_key 211 }; 212 213 const ECDH_METHOD * 214 ECDH_OpenSSL(void) 215 { 216 return &openssl_ecdh_meth; 217 } 218 219 /* replace w/ ecdh_compute_key() when ECDH_METHOD gets removed */ 220 int 221 ossl_ecdh_compute_key(void *out, size_t outlen, const EC_POINT *pub_key, 222 EC_KEY *eckey, 223 void *(*KDF)(const void *in, size_t inlen, void *out, size_t *outlen)) 224 { 225 ECDH_DATA *ecdh; 226 227 if ((ecdh = ecdh_check(eckey)) == NULL) 228 return 0; 229 return ecdh->meth->compute_key(out, outlen, pub_key, eckey, KDF); 230 } 231 232 int 233 ECDH_compute_key(void *out, size_t outlen, const EC_POINT *pub_key, 234 EC_KEY *eckey, 235 void *(*KDF)(const void *in, size_t inlen, void *out, size_t *outlen)) 236 { 237 if (eckey->meth->compute_key != NULL) 238 return eckey->meth->compute_key(out, outlen, pub_key, eckey, KDF); 239 ECerror(EC_R_NOT_IMPLEMENTED); 240 return 0; 241 } 242