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 65 static int generate_key(DH *dh); 66 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh); 67 static 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); 70 static int dh_init(DH *dh); 71 static int dh_finish(DH *dh); 72 73 int 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 85 int 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 97 int 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 } 110 111 static 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 }; 122 123 const DH_METHOD *DH_OpenSSL(void) 124 { 125 return &dh_ossl; 126 } 127 128 static int generate_key(DH *dh) 129 { 130 int ok = 0; 131 int generate_new_key = 0; 132 unsigned l; 133 BN_CTX *ctx; 134 BN_MONT_CTX *mont = NULL; 135 BIGNUM *pub_key = NULL, *priv_key = NULL; 136 137 ctx = BN_CTX_new(); 138 if (ctx == NULL) 139 goto err; 140 141 if (dh->priv_key == NULL) { 142 priv_key = BN_new(); 143 if (priv_key == NULL) 144 goto err; 145 generate_new_key = 1; 146 } else 147 priv_key = dh->priv_key; 148 149 if (dh->pub_key == NULL) { 150 pub_key = BN_new(); 151 if (pub_key == NULL) 152 goto err; 153 } else 154 pub_key = dh->pub_key; 155 156 if (dh->flags & DH_FLAG_CACHE_MONT_P) { 157 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 158 CRYPTO_LOCK_DH, dh->p, ctx); 159 if (!mont) 160 goto err; 161 } 162 163 if (generate_new_key) { 164 if (dh->q) { 165 do { 166 if (!BN_rand_range(priv_key, dh->q)) 167 goto err; 168 } 169 while (BN_is_zero(priv_key) || BN_is_one(priv_key)); 170 } else { 171 /* secret exponent length */ 172 l = dh->length ? dh->length : BN_num_bits(dh->p) - 1; 173 if (!BN_rand(priv_key, l, 0, 0)) 174 goto err; 175 } 176 } 177 178 { 179 BIGNUM local_prk; 180 BIGNUM *prk; 181 182 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) { 183 BN_init(&local_prk); 184 prk = &local_prk; 185 BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME); 186 } else 187 prk = priv_key; 188 189 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) 190 goto err; 191 } 192 193 dh->pub_key = pub_key; 194 dh->priv_key = priv_key; 195 ok = 1; 196 err: 197 if (ok != 1) 198 DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB); 199 200 if ((pub_key != NULL) && (dh->pub_key == NULL)) 201 BN_free(pub_key); 202 if ((priv_key != NULL) && (dh->priv_key == NULL)) 203 BN_free(priv_key); 204 BN_CTX_free(ctx); 205 return (ok); 206 } 207 208 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 209 { 210 BN_CTX *ctx = NULL; 211 BN_MONT_CTX *mont = NULL; 212 BIGNUM *tmp; 213 int ret = -1; 214 int check_result; 215 216 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 217 DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE); 218 goto err; 219 } 220 221 ctx = BN_CTX_new(); 222 if (ctx == NULL) 223 goto err; 224 BN_CTX_start(ctx); 225 tmp = BN_CTX_get(ctx); 226 if (tmp == NULL) 227 goto err; 228 229 if (dh->priv_key == NULL) { 230 DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE); 231 goto err; 232 } 233 234 if (dh->flags & DH_FLAG_CACHE_MONT_P) { 235 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 236 CRYPTO_LOCK_DH, dh->p, ctx); 237 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) { 238 /* XXX */ 239 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME); 240 } 241 if (!mont) 242 goto err; 243 } 244 245 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) { 246 DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY); 247 goto err; 248 } 249 250 if (!dh-> 251 meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, mont)) { 252 DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB); 253 goto err; 254 } 255 256 ret = BN_bn2bin(tmp, key); 257 err: 258 if (ctx != NULL) { 259 BN_CTX_end(ctx); 260 BN_CTX_free(ctx); 261 } 262 return (ret); 263 } 264 265 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, 266 const BIGNUM *a, const BIGNUM *p, 267 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx) 268 { 269 /* 270 * If a is only one word long and constant time is false, use the faster 271 * exponenentiation function. 272 */ 273 if (a->top == 1 && ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0)) { 274 BN_ULONG A = a->d[0]; 275 return BN_mod_exp_mont_word(r, A, p, m, ctx, m_ctx); 276 } else 277 return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx); 278 } 279 280 static int dh_init(DH *dh) 281 { 282 dh->flags |= DH_FLAG_CACHE_MONT_P; 283 return (1); 284 } 285 286 static int dh_finish(DH *dh) 287 { 288 if (dh->method_mont_p) 289 BN_MONT_CTX_free(dh->method_mont_p); 290 return (1); 291 } 292