dsa_gen.c revision 1.32
1/* $OpenBSD: dsa_gen.c,v 1.32 2024/05/11 06:43:50 tb 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 "bn_local.h" 72#include "dsa_local.h" 73 74int 75DSA_generate_parameters_ex(DSA *ret, int bits, const unsigned char *seed_in, 76 int seed_len, int *counter_ret, unsigned long *h_ret, BN_GENCB *cb) 77{ 78 const EVP_MD *evpmd; 79 size_t qbits; 80 81 if (bits >= 2048) { 82 qbits = 256; 83 evpmd = EVP_sha256(); 84 } else { 85 qbits = 160; 86 evpmd = EVP_sha1(); 87 } 88 89 return dsa_builtin_paramgen(ret, bits, qbits, evpmd, seed_in, seed_len, 90 NULL, counter_ret, h_ret, cb); 91} 92LCRYPTO_ALIAS(DSA_generate_parameters_ex); 93 94int 95dsa_builtin_paramgen(DSA *ret, size_t bits, size_t qbits, const EVP_MD *evpmd, 96 const unsigned char *seed_in, size_t seed_len, unsigned char *seed_out, 97 int *counter_ret, unsigned long *h_ret, BN_GENCB *cb) 98{ 99 int ok = 0; 100 unsigned char seed[SHA256_DIGEST_LENGTH]; 101 unsigned char md[SHA256_DIGEST_LENGTH]; 102 unsigned char buf[SHA256_DIGEST_LENGTH], buf2[SHA256_DIGEST_LENGTH]; 103 BIGNUM *r0, *W, *X, *c, *test; 104 BIGNUM *g = NULL, *q = NULL, *p = NULL; 105 BN_MONT_CTX *mont = NULL; 106 int i, k, n = 0, m = 0, qsize = qbits >> 3; 107 int counter = 0; 108 int r = 0; 109 BN_CTX *ctx = NULL; 110 unsigned int h = 2; 111 112 if (qsize != SHA_DIGEST_LENGTH && qsize != SHA224_DIGEST_LENGTH && 113 qsize != SHA256_DIGEST_LENGTH) 114 /* invalid q size */ 115 return 0; 116 117 if (evpmd == NULL) 118 /* use SHA1 as default */ 119 evpmd = EVP_sha1(); 120 121 if (bits < 512) 122 bits = 512; 123 124 bits = (bits + 63) / 64 * 64; 125 126 if (seed_len < (size_t)qsize) { 127 seed_in = NULL; /* seed buffer too small -- ignore */ 128 seed_len = 0; 129 } 130 /* 131 * App. 2.2 of FIPS PUB 186 allows larger SEED, 132 * but our internal buffers are restricted to 160 bits 133 */ 134 if (seed_len > (size_t)qsize) 135 seed_len = qsize; 136 if (seed_in != NULL) 137 memcpy(seed, seed_in, seed_len); 138 else if (seed_len != 0) 139 goto err; 140 141 if ((mont = BN_MONT_CTX_new()) == NULL) 142 goto err; 143 144 if ((ctx = BN_CTX_new()) == NULL) 145 goto err; 146 147 BN_CTX_start(ctx); 148 149 if ((r0 = BN_CTX_get(ctx)) == NULL) 150 goto err; 151 if ((g = BN_CTX_get(ctx)) == NULL) 152 goto err; 153 if ((W = BN_CTX_get(ctx)) == NULL) 154 goto err; 155 if ((q = BN_CTX_get(ctx)) == NULL) 156 goto err; 157 if ((X = BN_CTX_get(ctx)) == NULL) 158 goto err; 159 if ((c = BN_CTX_get(ctx)) == NULL) 160 goto err; 161 if ((p = BN_CTX_get(ctx)) == NULL) 162 goto err; 163 if ((test = BN_CTX_get(ctx)) == NULL) 164 goto err; 165 166 if (!BN_lshift(test, BN_value_one(), bits - 1)) 167 goto err; 168 169 for (;;) { 170 for (;;) { /* find q */ 171 int seed_is_random; 172 173 /* step 1 */ 174 if (!BN_GENCB_call(cb, 0, m++)) 175 goto err; 176 177 if (seed_len == 0) { 178 arc4random_buf(seed, qsize); 179 seed_is_random = 1; 180 } else { 181 seed_is_random = 0; 182 /* use random seed if 'seed_in' turns out 183 to be bad */ 184 seed_len = 0; 185 } 186 memcpy(buf, seed, qsize); 187 memcpy(buf2, seed, qsize); 188 /* precompute "SEED + 1" for step 7: */ 189 for (i = qsize - 1; i >= 0; i--) { 190 buf[i]++; 191 if (buf[i] != 0) 192 break; 193 } 194 195 /* step 2 */ 196 if (!EVP_Digest(seed, qsize, md, NULL, evpmd, NULL)) 197 goto err; 198 if (!EVP_Digest(buf, qsize, buf2, NULL, evpmd, NULL)) 199 goto err; 200 for (i = 0; i < qsize; i++) 201 md[i] ^= buf2[i]; 202 203 /* step 3 */ 204 md[0] |= 0x80; 205 md[qsize - 1] |= 0x01; 206 if (!BN_bin2bn(md, qsize, q)) 207 goto err; 208 209 /* step 4 */ 210 r = BN_is_prime_fasttest_ex(q, DSS_prime_checks, ctx, 211 seed_is_random, cb); 212 if (r > 0) 213 break; 214 if (r != 0) 215 goto err; 216 217 /* do a callback call */ 218 /* step 5 */ 219 } 220 221 if (!BN_GENCB_call(cb, 2, 0)) 222 goto err; 223 if (!BN_GENCB_call(cb, 3, 0)) 224 goto err; 225 226 /* step 6 */ 227 counter = 0; 228 /* "offset = 2" */ 229 230 n = (bits - 1) / 160; 231 232 for (;;) { 233 if (counter != 0 && !BN_GENCB_call(cb, 0, counter)) 234 goto err; 235 236 /* step 7 */ 237 BN_zero(W); 238 /* now 'buf' contains "SEED + offset - 1" */ 239 for (k = 0; k <= n; k++) { 240 /* obtain "SEED + offset + k" by incrementing: */ 241 for (i = qsize - 1; i >= 0; i--) { 242 buf[i]++; 243 if (buf[i] != 0) 244 break; 245 } 246 247 if (!EVP_Digest(buf, qsize, md ,NULL, evpmd, 248 NULL)) 249 goto err; 250 251 /* step 8 */ 252 if (!BN_bin2bn(md, qsize, r0)) 253 goto err; 254 if (!BN_lshift(r0, r0, (qsize << 3) * k)) 255 goto err; 256 if (!BN_add(W, W, r0)) 257 goto err; 258 } 259 260 /* more of step 8 */ 261 if (!BN_mask_bits(W, bits - 1)) 262 goto err; 263 if (!bn_copy(X, W)) 264 goto err; 265 if (!BN_add(X, X, test)) 266 goto err; 267 268 /* step 9 */ 269 if (!BN_lshift1(r0, q)) 270 goto err; 271 if (!BN_mod_ct(c, X, r0, ctx)) 272 goto err; 273 if (!BN_sub(r0, c, BN_value_one())) 274 goto err; 275 if (!BN_sub(p, X, r0)) 276 goto err; 277 278 /* step 10 */ 279 if (BN_cmp(p, test) >= 0) { 280 /* step 11 */ 281 r = BN_is_prime_fasttest_ex(p, DSS_prime_checks, 282 ctx, 1, cb); 283 if (r > 0) 284 goto end; /* found it */ 285 if (r != 0) 286 goto err; 287 } 288 289 /* step 13 */ 290 counter++; 291 /* "offset = offset + n + 1" */ 292 293 /* step 14 */ 294 if (counter >= 4096) 295 break; 296 } 297 } 298end: 299 if (!BN_GENCB_call(cb, 2, 1)) 300 goto err; 301 302 /* We now need to generate g */ 303 /* Set r0=(p-1)/q */ 304 if (!BN_sub(test, p, BN_value_one())) 305 goto err; 306 if (!BN_div_ct(r0, NULL, test, q, ctx)) 307 goto err; 308 309 if (!BN_set_word(test, h)) 310 goto err; 311 if (!BN_MONT_CTX_set(mont, p, ctx)) 312 goto err; 313 314 for (;;) { 315 /* g=test^r0%p */ 316 if (!BN_mod_exp_mont_ct(g, test, r0, p, ctx, mont)) 317 goto err; 318 if (!BN_is_one(g)) 319 break; 320 if (!BN_add(test, test, BN_value_one())) 321 goto err; 322 h++; 323 } 324 325 if (!BN_GENCB_call(cb, 3, 1)) 326 goto err; 327 328 ok = 1; 329err: 330 if (ok) { 331 BN_free(ret->p); 332 BN_free(ret->q); 333 BN_free(ret->g); 334 ret->p = BN_dup(p); 335 ret->q = BN_dup(q); 336 ret->g = BN_dup(g); 337 if (ret->p == NULL || ret->q == NULL || ret->g == NULL) { 338 ok = 0; 339 goto err; 340 } 341 if (counter_ret != NULL) 342 *counter_ret = counter; 343 if (h_ret != NULL) 344 *h_ret = h; 345 if (seed_out != NULL) 346 memcpy(seed_out, seed, qsize); 347 } 348 BN_CTX_end(ctx); 349 BN_CTX_free(ctx); 350 BN_MONT_CTX_free(mont); 351 352 return ok; 353} 354 355#endif 356