dsa_gen.c revision 1.13
1/* $OpenBSD: dsa_gen.c,v 1.13 2014/07/09 10:16:24 miod Exp $ */ 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 <openssl/opensslconf.h> /* To see if OPENSSL_NO_SHA is defined */ 60 61#ifndef OPENSSL_NO_SHA 62 63#include <stdio.h> 64#include "cryptlib.h" 65#include <openssl/evp.h> 66#include <openssl/bn.h> 67#include <openssl/rand.h> 68#include <openssl/sha.h> 69#include "dsa_locl.h" 70 71int 72DSA_generate_parameters_ex(DSA *ret, int bits, const unsigned char *seed_in, 73 int seed_len, int *counter_ret, unsigned long *h_ret, BN_GENCB *cb) 74{ 75 if (ret->meth->dsa_paramgen) 76 return ret->meth->dsa_paramgen(ret, bits, seed_in, seed_len, 77 counter_ret, h_ret, cb); 78 else { 79 const EVP_MD *evpmd; 80 size_t qbits; 81 82 if (bits >= 2048) { 83 qbits = 256; 84 evpmd = EVP_sha256(); 85 } else { 86 qbits = 160; 87 evpmd = EVP_sha1(); 88 } 89 90 return dsa_builtin_paramgen(ret, bits, qbits, evpmd, seed_in, 91 seed_len, NULL, counter_ret, h_ret, cb); 92 } 93} 94 95int 96dsa_builtin_paramgen(DSA *ret, size_t bits, size_t qbits, const EVP_MD *evpmd, 97 const unsigned char *seed_in, size_t seed_len, unsigned char *seed_out, 98 int *counter_ret, unsigned long *h_ret, BN_GENCB *cb) 99{ 100 int ok = 0; 101 unsigned char seed[SHA256_DIGEST_LENGTH]; 102 unsigned char md[SHA256_DIGEST_LENGTH]; 103 unsigned char buf[SHA256_DIGEST_LENGTH], buf2[SHA256_DIGEST_LENGTH]; 104 BIGNUM *r0, *W, *X, *c, *test; 105 BIGNUM *g = NULL, *q = NULL, *p = NULL; 106 BN_MONT_CTX *mont = NULL; 107 int i, k, n = 0, m = 0, qsize = qbits >> 3; 108 int counter = 0; 109 int r = 0; 110 BN_CTX *ctx = NULL; 111 unsigned int h = 2; 112 113 if (qsize != SHA_DIGEST_LENGTH && qsize != SHA224_DIGEST_LENGTH && 114 qsize != SHA256_DIGEST_LENGTH) 115 /* invalid q size */ 116 return 0; 117 118 if (evpmd == NULL) 119 /* use SHA1 as default */ 120 evpmd = EVP_sha1(); 121 122 if (bits < 512) 123 bits = 512; 124 125 bits = (bits + 63) / 64 * 64; 126 127 /* 128 * NB: seed_len == 0 is special case: copy generated seed to 129 * seed_in if it is not NULL. 130 */ 131 if (seed_len && seed_len < (size_t)qsize) 132 seed_in = NULL; /* seed buffer too small -- ignore */ 133 /* 134 * App. 2.2 of FIPS PUB 186 allows larger SEED, 135 * but our internal buffers are restricted to 160 bits 136 */ 137 if (seed_len > (size_t)qsize) 138 seed_len = qsize; 139 if (seed_in != NULL) 140 memcpy(seed, seed_in, seed_len); 141 142 if ((ctx=BN_CTX_new()) == NULL) 143 goto err; 144 145 if ((mont=BN_MONT_CTX_new()) == NULL) 146 goto err; 147 148 BN_CTX_start(ctx); 149 r0 = BN_CTX_get(ctx); 150 g = BN_CTX_get(ctx); 151 W = BN_CTX_get(ctx); 152 q = BN_CTX_get(ctx); 153 X = BN_CTX_get(ctx); 154 c = BN_CTX_get(ctx); 155 p = BN_CTX_get(ctx); 156 test = BN_CTX_get(ctx); 157 158 if (!BN_lshift(test, BN_value_one(), bits - 1)) 159 goto err; 160 161 for (;;) { 162 for (;;) { /* find q */ 163 int seed_is_random; 164 165 /* step 1 */ 166 if (!BN_GENCB_call(cb, 0, m++)) 167 goto err; 168 169 if (!seed_len) { 170 RAND_pseudo_bytes(seed, qsize); 171 seed_is_random = 1; 172 } else { 173 seed_is_random = 0; 174 /* use random seed if 'seed_in' turns out 175 to be bad */ 176 seed_len = 0; 177 } 178 memcpy(buf, seed, qsize); 179 memcpy(buf2, seed, qsize); 180 /* precompute "SEED + 1" for step 7: */ 181 for (i = qsize - 1; i >= 0; i--) { 182 buf[i]++; 183 if (buf[i] != 0) 184 break; 185 } 186 187 /* step 2 */ 188 if (!EVP_Digest(seed, qsize, md, NULL, evpmd, NULL)) 189 goto err; 190 if (!EVP_Digest(buf, qsize, buf2, NULL, evpmd, NULL)) 191 goto err; 192 for (i = 0; i < qsize; i++) 193 md[i] ^= buf2[i]; 194 195 /* step 3 */ 196 md[0] |= 0x80; 197 md[qsize - 1] |= 0x01; 198 if (!BN_bin2bn(md, qsize, q)) 199 goto err; 200 201 /* step 4 */ 202 r = BN_is_prime_fasttest_ex(q, DSS_prime_checks, ctx, 203 seed_is_random, cb); 204 if (r > 0) 205 break; 206 if (r != 0) 207 goto err; 208 209 /* do a callback call */ 210 /* step 5 */ 211 } 212 213 if (!BN_GENCB_call(cb, 2, 0)) 214 goto err; 215 if (!BN_GENCB_call(cb, 3, 0)) 216 goto err; 217 218 /* step 6 */ 219 counter = 0; 220 /* "offset = 2" */ 221 222 n = (bits - 1) / 160; 223 224 for (;;) { 225 if (counter != 0 && !BN_GENCB_call(cb, 0, counter)) 226 goto err; 227 228 /* step 7 */ 229 BN_zero(W); 230 /* now 'buf' contains "SEED + offset - 1" */ 231 for (k = 0; k <= n; k++) { 232 /* obtain "SEED + offset + k" by incrementing: */ 233 for (i = qsize - 1; i >= 0; i--) { 234 buf[i]++; 235 if (buf[i] != 0) 236 break; 237 } 238 239 if (!EVP_Digest(buf, qsize, md ,NULL, evpmd, 240 NULL)) 241 goto err; 242 243 /* step 8 */ 244 if (!BN_bin2bn(md, qsize, r0)) 245 goto err; 246 if (!BN_lshift(r0, r0, (qsize << 3) * k)) 247 goto err; 248 if (!BN_add(W, W, r0)) 249 goto err; 250 } 251 252 /* more of step 8 */ 253 if (!BN_mask_bits(W, bits - 1)) 254 goto err; 255 if (!BN_copy(X, W)) 256 goto err; 257 if (!BN_add(X, X, test)) 258 goto err; 259 260 /* step 9 */ 261 if (!BN_lshift1(r0, q)) 262 goto err; 263 if (!BN_mod(c, X, r0, ctx)) 264 goto err; 265 if (!BN_sub(r0, c, BN_value_one())) 266 goto err; 267 if (!BN_sub(p, X, r0)) 268 goto err; 269 270 /* step 10 */ 271 if (BN_cmp(p, test) >= 0) { 272 /* step 11 */ 273 r = BN_is_prime_fasttest_ex(p, DSS_prime_checks, 274 ctx, 1, cb); 275 if (r > 0) 276 goto end; /* found it */ 277 if (r != 0) 278 goto err; 279 } 280 281 /* step 13 */ 282 counter++; 283 /* "offset = offset + n + 1" */ 284 285 /* step 14 */ 286 if (counter >= 4096) 287 break; 288 } 289 } 290end: 291 if (!BN_GENCB_call(cb, 2, 1)) 292 goto err; 293 294 /* We now need to generate g */ 295 /* Set r0=(p-1)/q */ 296 if (!BN_sub(test, p, BN_value_one())) 297 goto err; 298 if (!BN_div(r0, NULL, test, q, ctx)) 299 goto err; 300 301 if (!BN_set_word(test, h)) 302 goto err; 303 if (!BN_MONT_CTX_set(mont, p, ctx)) 304 goto err; 305 306 for (;;) { 307 /* g=test^r0%p */ 308 if (!BN_mod_exp_mont(g, test, r0, p, ctx, mont)) 309 goto err; 310 if (!BN_is_one(g)) 311 break; 312 if (!BN_add(test, test, BN_value_one())) 313 goto err; 314 h++; 315 } 316 317 if (!BN_GENCB_call(cb, 3, 1)) 318 goto err; 319 320 ok = 1; 321err: 322 if (ok) { 323 if (ret->p) 324 BN_free(ret->p); 325 if (ret->q) 326 BN_free(ret->q); 327 if (ret->g) 328 BN_free(ret->g); 329 ret->p = BN_dup(p); 330 ret->q = BN_dup(q); 331 ret->g = BN_dup(g); 332 if (ret->p == NULL || ret->q == NULL || ret->g == NULL) { 333 ok = 0; 334 goto err; 335 } 336 if (counter_ret != NULL) 337 *counter_ret = counter; 338 if (h_ret != NULL) 339 *h_ret = h; 340 if (seed_out) 341 memcpy(seed_out, seed, qsize); 342 } 343 if (ctx) { 344 BN_CTX_end(ctx); 345 BN_CTX_free(ctx); 346 } 347 if (mont != NULL) 348 BN_MONT_CTX_free(mont); 349 return ok; 350} 351#endif 352