dsa_gen.c revision 1.18
1/* $OpenBSD: dsa_gen.c,v 1.18 2015/02/09 15:49:22 jsing 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 <stdlib.h> 65#include <string.h> 66 67#include <openssl/bn.h> 68#include <openssl/evp.h> 69#include <openssl/sha.h> 70 71#include "dsa_locl.h" 72 73int 74DSA_generate_parameters_ex(DSA *ret, int bits, const unsigned char *seed_in, 75 int seed_len, int *counter_ret, unsigned long *h_ret, BN_GENCB *cb) 76{ 77 if (ret->meth->dsa_paramgen) 78 return ret->meth->dsa_paramgen(ret, bits, seed_in, seed_len, 79 counter_ret, h_ret, cb); 80 else { 81 const EVP_MD *evpmd; 82 size_t qbits; 83 84 if (bits >= 2048) { 85 qbits = 256; 86 evpmd = EVP_sha256(); 87 } else { 88 qbits = 160; 89 evpmd = EVP_sha1(); 90 } 91 92 return dsa_builtin_paramgen(ret, bits, qbits, evpmd, seed_in, 93 seed_len, NULL, counter_ret, h_ret, cb); 94 } 95} 96 97int 98dsa_builtin_paramgen(DSA *ret, size_t bits, size_t qbits, const EVP_MD *evpmd, 99 const unsigned char *seed_in, size_t seed_len, unsigned char *seed_out, 100 int *counter_ret, unsigned long *h_ret, BN_GENCB *cb) 101{ 102 int ok = 0; 103 unsigned char seed[SHA256_DIGEST_LENGTH]; 104 unsigned char md[SHA256_DIGEST_LENGTH]; 105 unsigned char buf[SHA256_DIGEST_LENGTH], buf2[SHA256_DIGEST_LENGTH]; 106 BIGNUM *r0, *W, *X, *c, *test; 107 BIGNUM *g = NULL, *q = NULL, *p = NULL; 108 BN_MONT_CTX *mont = NULL; 109 int i, k, n = 0, m = 0, qsize = qbits >> 3; 110 int counter = 0; 111 int r = 0; 112 BN_CTX *ctx = NULL; 113 unsigned int h = 2; 114 115 if (qsize != SHA_DIGEST_LENGTH && qsize != SHA224_DIGEST_LENGTH && 116 qsize != SHA256_DIGEST_LENGTH) 117 /* invalid q size */ 118 return 0; 119 120 if (evpmd == NULL) 121 /* use SHA1 as default */ 122 evpmd = EVP_sha1(); 123 124 if (bits < 512) 125 bits = 512; 126 127 bits = (bits + 63) / 64 * 64; 128 129 /* 130 * NB: seed_len == 0 is special case: copy generated seed to 131 * seed_in if it is not NULL. 132 */ 133 if (seed_len && seed_len < (size_t)qsize) 134 seed_in = NULL; /* seed buffer too small -- ignore */ 135 /* 136 * App. 2.2 of FIPS PUB 186 allows larger SEED, 137 * but our internal buffers are restricted to 160 bits 138 */ 139 if (seed_len > (size_t)qsize) 140 seed_len = qsize; 141 if (seed_in != NULL) 142 memcpy(seed, seed_in, seed_len); 143 144 if ((ctx=BN_CTX_new()) == NULL) 145 goto err; 146 147 if ((mont=BN_MONT_CTX_new()) == NULL) 148 goto err; 149 150 BN_CTX_start(ctx); 151 if ((r0 = BN_CTX_get(ctx)) == NULL) 152 goto err; 153 if ((g = BN_CTX_get(ctx)) == NULL) 154 goto err; 155 if ((W = BN_CTX_get(ctx)) == NULL) 156 goto err; 157 if ((q = BN_CTX_get(ctx)) == NULL) 158 goto err; 159 if ((X = BN_CTX_get(ctx)) == NULL) 160 goto err; 161 if ((c = BN_CTX_get(ctx)) == NULL) 162 goto err; 163 if ((p = BN_CTX_get(ctx)) == NULL) 164 goto err; 165 if ((test = BN_CTX_get(ctx)) == NULL) 166 goto err; 167 168 if (!BN_lshift(test, BN_value_one(), bits - 1)) 169 goto err; 170 171 for (;;) { 172 for (;;) { /* find q */ 173 int seed_is_random; 174 175 /* step 1 */ 176 if (!BN_GENCB_call(cb, 0, m++)) 177 goto err; 178 179 if (!seed_len) { 180 arc4random_buf(seed, qsize); 181 seed_is_random = 1; 182 } else { 183 seed_is_random = 0; 184 /* use random seed if 'seed_in' turns out 185 to be bad */ 186 seed_len = 0; 187 } 188 memcpy(buf, seed, qsize); 189 memcpy(buf2, seed, qsize); 190 /* precompute "SEED + 1" for step 7: */ 191 for (i = qsize - 1; i >= 0; i--) { 192 buf[i]++; 193 if (buf[i] != 0) 194 break; 195 } 196 197 /* step 2 */ 198 if (!EVP_Digest(seed, qsize, md, NULL, evpmd, NULL)) 199 goto err; 200 if (!EVP_Digest(buf, qsize, buf2, NULL, evpmd, NULL)) 201 goto err; 202 for (i = 0; i < qsize; i++) 203 md[i] ^= buf2[i]; 204 205 /* step 3 */ 206 md[0] |= 0x80; 207 md[qsize - 1] |= 0x01; 208 if (!BN_bin2bn(md, qsize, q)) 209 goto err; 210 211 /* step 4 */ 212 r = BN_is_prime_fasttest_ex(q, DSS_prime_checks, ctx, 213 seed_is_random, cb); 214 if (r > 0) 215 break; 216 if (r != 0) 217 goto err; 218 219 /* do a callback call */ 220 /* step 5 */ 221 } 222 223 if (!BN_GENCB_call(cb, 2, 0)) 224 goto err; 225 if (!BN_GENCB_call(cb, 3, 0)) 226 goto err; 227 228 /* step 6 */ 229 counter = 0; 230 /* "offset = 2" */ 231 232 n = (bits - 1) / 160; 233 234 for (;;) { 235 if (counter != 0 && !BN_GENCB_call(cb, 0, counter)) 236 goto err; 237 238 /* step 7 */ 239 BN_zero(W); 240 /* now 'buf' contains "SEED + offset - 1" */ 241 for (k = 0; k <= n; k++) { 242 /* obtain "SEED + offset + k" by incrementing: */ 243 for (i = qsize - 1; i >= 0; i--) { 244 buf[i]++; 245 if (buf[i] != 0) 246 break; 247 } 248 249 if (!EVP_Digest(buf, qsize, md ,NULL, evpmd, 250 NULL)) 251 goto err; 252 253 /* step 8 */ 254 if (!BN_bin2bn(md, qsize, r0)) 255 goto err; 256 if (!BN_lshift(r0, r0, (qsize << 3) * k)) 257 goto err; 258 if (!BN_add(W, W, r0)) 259 goto err; 260 } 261 262 /* more of step 8 */ 263 if (!BN_mask_bits(W, bits - 1)) 264 goto err; 265 if (!BN_copy(X, W)) 266 goto err; 267 if (!BN_add(X, X, test)) 268 goto err; 269 270 /* step 9 */ 271 if (!BN_lshift1(r0, q)) 272 goto err; 273 if (!BN_mod(c, X, r0, ctx)) 274 goto err; 275 if (!BN_sub(r0, c, BN_value_one())) 276 goto err; 277 if (!BN_sub(p, X, r0)) 278 goto err; 279 280 /* step 10 */ 281 if (BN_cmp(p, test) >= 0) { 282 /* step 11 */ 283 r = BN_is_prime_fasttest_ex(p, DSS_prime_checks, 284 ctx, 1, cb); 285 if (r > 0) 286 goto end; /* found it */ 287 if (r != 0) 288 goto err; 289 } 290 291 /* step 13 */ 292 counter++; 293 /* "offset = offset + n + 1" */ 294 295 /* step 14 */ 296 if (counter >= 4096) 297 break; 298 } 299 } 300end: 301 if (!BN_GENCB_call(cb, 2, 1)) 302 goto err; 303 304 /* We now need to generate g */ 305 /* Set r0=(p-1)/q */ 306 if (!BN_sub(test, p, BN_value_one())) 307 goto err; 308 if (!BN_div(r0, NULL, test, q, ctx)) 309 goto err; 310 311 if (!BN_set_word(test, h)) 312 goto err; 313 if (!BN_MONT_CTX_set(mont, p, ctx)) 314 goto err; 315 316 for (;;) { 317 /* g=test^r0%p */ 318 if (!BN_mod_exp_mont(g, test, r0, p, ctx, mont)) 319 goto err; 320 if (!BN_is_one(g)) 321 break; 322 if (!BN_add(test, test, BN_value_one())) 323 goto err; 324 h++; 325 } 326 327 if (!BN_GENCB_call(cb, 3, 1)) 328 goto err; 329 330 ok = 1; 331err: 332 if (ok) { 333 BN_free(ret->p); 334 BN_free(ret->q); 335 BN_free(ret->g); 336 ret->p = BN_dup(p); 337 ret->q = BN_dup(q); 338 ret->g = BN_dup(g); 339 if (ret->p == NULL || ret->q == NULL || ret->g == NULL) { 340 ok = 0; 341 goto err; 342 } 343 if (counter_ret != NULL) 344 *counter_ret = counter; 345 if (h_ret != NULL) 346 *h_ret = h; 347 if (seed_out) 348 memcpy(seed_out, seed, qsize); 349 } 350 if (ctx) { 351 BN_CTX_end(ctx); 352 BN_CTX_free(ctx); 353 } 354 BN_MONT_CTX_free(mont); 355 return ok; 356} 357#endif 358