dh_key.c revision 337982
1/* crypto/dh/dh_key.c */ 2/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) 3 * All rights reserved. 4 * 5 * This package is an SSL implementation written 6 * by Eric Young (eay@cryptsoft.com). 7 * The implementation was written so as to conform with Netscapes SSL. 8 * 9 * This library is free for commercial and non-commercial use as long as 10 * the following conditions are aheared to. The following conditions 11 * apply to all code found in this distribution, be it the RC4, RSA, 12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation 13 * included with this distribution is covered by the same copyright terms 14 * except that the holder is Tim Hudson (tjh@cryptsoft.com). 15 * 16 * Copyright remains Eric Young's, and as such any Copyright notices in 17 * the code are not to be removed. 18 * If this package is used in a product, Eric Young should be given attribution 19 * as the author of the parts of the library used. 20 * This can be in the form of a textual message at program startup or 21 * in documentation (online or textual) provided with the package. 22 * 23 * Redistribution and use in source and binary forms, with or without 24 * modification, are permitted provided that the following conditions 25 * are met: 26 * 1. Redistributions of source code must retain the copyright 27 * notice, this list of conditions and the following disclaimer. 28 * 2. Redistributions in binary form must reproduce the above copyright 29 * notice, this list of conditions and the following disclaimer in the 30 * documentation and/or other materials provided with the distribution. 31 * 3. All advertising materials mentioning features or use of this software 32 * must display the following acknowledgement: 33 * "This product includes cryptographic software written by 34 * Eric Young (eay@cryptsoft.com)" 35 * The word 'cryptographic' can be left out if the rouines from the library 36 * being used are not cryptographic related :-). 37 * 4. If you include any Windows specific code (or a derivative thereof) from 38 * the apps directory (application code) you must include an acknowledgement: 39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" 40 * 41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND 42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 51 * SUCH DAMAGE. 52 * 53 * The licence and distribution terms for any publically available version or 54 * derivative of this code cannot be changed. i.e. this code cannot simply be 55 * copied and put under another distribution licence 56 * [including the GNU Public Licence.] 57 */ 58 59#include <stdio.h> 60#include "cryptlib.h" 61#include <openssl/bn.h> 62#include <openssl/rand.h> 63#include <openssl/dh.h> 64 65static int generate_key(DH *dh); 66static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh); 67static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, 68 const BIGNUM *a, const BIGNUM *p, 69 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx); 70static int dh_init(DH *dh); 71static int dh_finish(DH *dh); 72 73int DH_generate_key(DH *dh) 74{ 75#ifdef OPENSSL_FIPS 76 if (FIPS_mode() && !(dh->meth->flags & DH_FLAG_FIPS_METHOD) 77 && !(dh->flags & DH_FLAG_NON_FIPS_ALLOW)) { 78 DHerr(DH_F_DH_GENERATE_KEY, DH_R_NON_FIPS_METHOD); 79 return 0; 80 } 81#endif 82 return dh->meth->generate_key(dh); 83} 84 85int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 86{ 87#ifdef OPENSSL_FIPS 88 if (FIPS_mode() && !(dh->meth->flags & DH_FLAG_FIPS_METHOD) 89 && !(dh->flags & DH_FLAG_NON_FIPS_ALLOW)) { 90 DHerr(DH_F_DH_COMPUTE_KEY, DH_R_NON_FIPS_METHOD); 91 return 0; 92 } 93#endif 94 return dh->meth->compute_key(key, pub_key, dh); 95} 96 97int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh) 98{ 99 int rv, pad; 100 rv = dh->meth->compute_key(key, pub_key, dh); 101 if (rv <= 0) 102 return rv; 103 pad = BN_num_bytes(dh->p) - rv; 104 if (pad > 0) { 105 memmove(key + pad, key, rv); 106 memset(key, 0, pad); 107 } 108 return rv + pad; 109} 110 111static DH_METHOD dh_ossl = { 112 "OpenSSL DH Method", 113 generate_key, 114 compute_key, 115 dh_bn_mod_exp, 116 dh_init, 117 dh_finish, 118 0, 119 NULL, 120 NULL 121}; 122 123const DH_METHOD *DH_OpenSSL(void) 124{ 125 return &dh_ossl; 126} 127 128static int generate_key(DH *dh) 129{ 130 int ok = 0; 131 int generate_new_key = 0; 132 unsigned l; 133 BN_CTX *ctx = NULL; 134 BN_MONT_CTX *mont = NULL; 135 BIGNUM *pub_key = NULL, *priv_key = NULL; 136 137 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 138 DHerr(DH_F_GENERATE_KEY, DH_R_MODULUS_TOO_LARGE); 139 return 0; 140 } 141 142 ctx = BN_CTX_new(); 143 if (ctx == NULL) 144 goto err; 145 146 if (dh->priv_key == NULL) { 147 priv_key = BN_new(); 148 if (priv_key == NULL) 149 goto err; 150 generate_new_key = 1; 151 } else 152 priv_key = dh->priv_key; 153 154 if (dh->pub_key == NULL) { 155 pub_key = BN_new(); 156 if (pub_key == NULL) 157 goto err; 158 } else 159 pub_key = dh->pub_key; 160 161 if (dh->flags & DH_FLAG_CACHE_MONT_P) { 162 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 163 CRYPTO_LOCK_DH, dh->p, ctx); 164 if (!mont) 165 goto err; 166 } 167 168 if (generate_new_key) { 169 if (dh->q) { 170 do { 171 if (!BN_rand_range(priv_key, dh->q)) 172 goto err; 173 } 174 while (BN_is_zero(priv_key) || BN_is_one(priv_key)); 175 } else { 176 /* secret exponent length */ 177 l = dh->length ? dh->length : BN_num_bits(dh->p) - 1; 178 if (!BN_rand(priv_key, l, 0, 0)) 179 goto err; 180 } 181 } 182 183 { 184 BIGNUM local_prk; 185 BIGNUM *prk; 186 187 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) { 188 BN_init(&local_prk); 189 prk = &local_prk; 190 BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME); 191 } else 192 prk = priv_key; 193 194 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) 195 goto err; 196 } 197 198 dh->pub_key = pub_key; 199 dh->priv_key = priv_key; 200 ok = 1; 201 err: 202 if (ok != 1) 203 DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB); 204 205 if ((pub_key != NULL) && (dh->pub_key == NULL)) 206 BN_free(pub_key); 207 if ((priv_key != NULL) && (dh->priv_key == NULL)) 208 BN_free(priv_key); 209 BN_CTX_free(ctx); 210 return (ok); 211} 212 213static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 214{ 215 BN_CTX *ctx = NULL; 216 BN_MONT_CTX *mont = NULL; 217 BIGNUM *tmp; 218 int ret = -1; 219 int check_result; 220 221 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 222 DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE); 223 goto err; 224 } 225 226 ctx = BN_CTX_new(); 227 if (ctx == NULL) 228 goto err; 229 BN_CTX_start(ctx); 230 tmp = BN_CTX_get(ctx); 231 if (tmp == NULL) 232 goto err; 233 234 if (dh->priv_key == NULL) { 235 DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE); 236 goto err; 237 } 238 239 if (dh->flags & DH_FLAG_CACHE_MONT_P) { 240 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 241 CRYPTO_LOCK_DH, dh->p, ctx); 242 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) { 243 /* XXX */ 244 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME); 245 } 246 if (!mont) 247 goto err; 248 } 249 250 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) { 251 DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY); 252 goto err; 253 } 254 255 if (!dh-> 256 meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, mont)) { 257 DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB); 258 goto err; 259 } 260 261 ret = BN_bn2bin(tmp, key); 262 err: 263 if (ctx != NULL) { 264 BN_CTX_end(ctx); 265 BN_CTX_free(ctx); 266 } 267 return (ret); 268} 269 270static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, 271 const BIGNUM *a, const BIGNUM *p, 272 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx) 273{ 274 /* 275 * If a is only one word long and constant time is false, use the faster 276 * exponenentiation function. 277 */ 278 if (a->top == 1 && ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0)) { 279 BN_ULONG A = a->d[0]; 280 return BN_mod_exp_mont_word(r, A, p, m, ctx, m_ctx); 281 } else 282 return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx); 283} 284 285static int dh_init(DH *dh) 286{ 287 dh->flags |= DH_FLAG_CACHE_MONT_P; 288 return (1); 289} 290 291static int dh_finish(DH *dh) 292{ 293 if (dh->method_mont_p) 294 BN_MONT_CTX_free(dh->method_mont_p); 295 return (1); 296} 297