dsa_gen.c revision 1.28
1/* $OpenBSD: dsa_gen.c,v 1.28 2023/03/27 10:25:02 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 if (ret->meth->dsa_paramgen) 79 return ret->meth->dsa_paramgen(ret, bits, seed_in, seed_len, 80 counter_ret, h_ret, cb); 81 else { 82 const EVP_MD *evpmd; 83 size_t qbits; 84 85 if (bits >= 2048) { 86 qbits = 256; 87 evpmd = EVP_sha256(); 88 } else { 89 qbits = 160; 90 evpmd = EVP_sha1(); 91 } 92 93 return dsa_builtin_paramgen(ret, bits, qbits, evpmd, seed_in, 94 seed_len, NULL, counter_ret, h_ret, cb); 95 } 96} 97 98int 99dsa_builtin_paramgen(DSA *ret, size_t bits, size_t qbits, const EVP_MD *evpmd, 100 const unsigned char *seed_in, size_t seed_len, unsigned char *seed_out, 101 int *counter_ret, unsigned long *h_ret, BN_GENCB *cb) 102{ 103 int ok = 0; 104 unsigned char seed[SHA256_DIGEST_LENGTH]; 105 unsigned char md[SHA256_DIGEST_LENGTH]; 106 unsigned char buf[SHA256_DIGEST_LENGTH], buf2[SHA256_DIGEST_LENGTH]; 107 BIGNUM *r0, *W, *X, *c, *test; 108 BIGNUM *g = NULL, *q = NULL, *p = NULL; 109 BN_MONT_CTX *mont = NULL; 110 int i, k, n = 0, m = 0, qsize = qbits >> 3; 111 int counter = 0; 112 int r = 0; 113 BN_CTX *ctx = NULL; 114 unsigned int h = 2; 115 116 if (qsize != SHA_DIGEST_LENGTH && qsize != SHA224_DIGEST_LENGTH && 117 qsize != SHA256_DIGEST_LENGTH) 118 /* invalid q size */ 119 return 0; 120 121 if (evpmd == NULL) 122 /* use SHA1 as default */ 123 evpmd = EVP_sha1(); 124 125 if (bits < 512) 126 bits = 512; 127 128 bits = (bits + 63) / 64 * 64; 129 130 if (seed_len < (size_t)qsize) { 131 seed_in = NULL; /* seed buffer too small -- ignore */ 132 seed_len = 0; 133 } 134 /* 135 * App. 2.2 of FIPS PUB 186 allows larger SEED, 136 * but our internal buffers are restricted to 160 bits 137 */ 138 if (seed_len > (size_t)qsize) 139 seed_len = qsize; 140 if (seed_in != NULL) 141 memcpy(seed, seed_in, seed_len); 142 else if (seed_len != 0) 143 goto err; 144 145 if ((mont = BN_MONT_CTX_new()) == NULL) 146 goto err; 147 148 if ((ctx = BN_CTX_new()) == NULL) 149 goto err; 150 151 BN_CTX_start(ctx); 152 153 if ((r0 = BN_CTX_get(ctx)) == NULL) 154 goto err; 155 if ((g = BN_CTX_get(ctx)) == NULL) 156 goto err; 157 if ((W = BN_CTX_get(ctx)) == NULL) 158 goto err; 159 if ((q = BN_CTX_get(ctx)) == NULL) 160 goto err; 161 if ((X = BN_CTX_get(ctx)) == NULL) 162 goto err; 163 if ((c = BN_CTX_get(ctx)) == NULL) 164 goto err; 165 if ((p = BN_CTX_get(ctx)) == NULL) 166 goto err; 167 if ((test = BN_CTX_get(ctx)) == NULL) 168 goto err; 169 170 if (!BN_lshift(test, BN_value_one(), bits - 1)) 171 goto err; 172 173 for (;;) { 174 for (;;) { /* find q */ 175 int seed_is_random; 176 177 /* step 1 */ 178 if (!BN_GENCB_call(cb, 0, m++)) 179 goto err; 180 181 if (seed_len == 0) { 182 arc4random_buf(seed, qsize); 183 seed_is_random = 1; 184 } else { 185 seed_is_random = 0; 186 /* use random seed if 'seed_in' turns out 187 to be bad */ 188 seed_len = 0; 189 } 190 memcpy(buf, seed, qsize); 191 memcpy(buf2, seed, qsize); 192 /* precompute "SEED + 1" for step 7: */ 193 for (i = qsize - 1; i >= 0; i--) { 194 buf[i]++; 195 if (buf[i] != 0) 196 break; 197 } 198 199 /* step 2 */ 200 if (!EVP_Digest(seed, qsize, md, NULL, evpmd, NULL)) 201 goto err; 202 if (!EVP_Digest(buf, qsize, buf2, NULL, evpmd, NULL)) 203 goto err; 204 for (i = 0; i < qsize; i++) 205 md[i] ^= buf2[i]; 206 207 /* step 3 */ 208 md[0] |= 0x80; 209 md[qsize - 1] |= 0x01; 210 if (!BN_bin2bn(md, qsize, q)) 211 goto err; 212 213 /* step 4 */ 214 r = BN_is_prime_fasttest_ex(q, DSS_prime_checks, ctx, 215 seed_is_random, cb); 216 if (r > 0) 217 break; 218 if (r != 0) 219 goto err; 220 221 /* do a callback call */ 222 /* step 5 */ 223 } 224 225 if (!BN_GENCB_call(cb, 2, 0)) 226 goto err; 227 if (!BN_GENCB_call(cb, 3, 0)) 228 goto err; 229 230 /* step 6 */ 231 counter = 0; 232 /* "offset = 2" */ 233 234 n = (bits - 1) / 160; 235 236 for (;;) { 237 if (counter != 0 && !BN_GENCB_call(cb, 0, counter)) 238 goto err; 239 240 /* step 7 */ 241 BN_zero(W); 242 /* now 'buf' contains "SEED + offset - 1" */ 243 for (k = 0; k <= n; k++) { 244 /* obtain "SEED + offset + k" by incrementing: */ 245 for (i = qsize - 1; i >= 0; i--) { 246 buf[i]++; 247 if (buf[i] != 0) 248 break; 249 } 250 251 if (!EVP_Digest(buf, qsize, md ,NULL, evpmd, 252 NULL)) 253 goto err; 254 255 /* step 8 */ 256 if (!BN_bin2bn(md, qsize, r0)) 257 goto err; 258 if (!BN_lshift(r0, r0, (qsize << 3) * k)) 259 goto err; 260 if (!BN_add(W, W, r0)) 261 goto err; 262 } 263 264 /* more of step 8 */ 265 if (!BN_mask_bits(W, bits - 1)) 266 goto err; 267 if (!bn_copy(X, W)) 268 goto err; 269 if (!BN_add(X, X, test)) 270 goto err; 271 272 /* step 9 */ 273 if (!BN_lshift1(r0, q)) 274 goto err; 275 if (!BN_mod_ct(c, X, r0, ctx)) 276 goto err; 277 if (!BN_sub(r0, c, BN_value_one())) 278 goto err; 279 if (!BN_sub(p, X, r0)) 280 goto err; 281 282 /* step 10 */ 283 if (BN_cmp(p, test) >= 0) { 284 /* step 11 */ 285 r = BN_is_prime_fasttest_ex(p, DSS_prime_checks, 286 ctx, 1, cb); 287 if (r > 0) 288 goto end; /* found it */ 289 if (r != 0) 290 goto err; 291 } 292 293 /* step 13 */ 294 counter++; 295 /* "offset = offset + n + 1" */ 296 297 /* step 14 */ 298 if (counter >= 4096) 299 break; 300 } 301 } 302end: 303 if (!BN_GENCB_call(cb, 2, 1)) 304 goto err; 305 306 /* We now need to generate g */ 307 /* Set r0=(p-1)/q */ 308 if (!BN_sub(test, p, BN_value_one())) 309 goto err; 310 if (!BN_div_ct(r0, NULL, test, q, ctx)) 311 goto err; 312 313 if (!BN_set_word(test, h)) 314 goto err; 315 if (!BN_MONT_CTX_set(mont, p, ctx)) 316 goto err; 317 318 for (;;) { 319 /* g=test^r0%p */ 320 if (!BN_mod_exp_mont_ct(g, test, r0, p, ctx, mont)) 321 goto err; 322 if (!BN_is_one(g)) 323 break; 324 if (!BN_add(test, test, BN_value_one())) 325 goto err; 326 h++; 327 } 328 329 if (!BN_GENCB_call(cb, 3, 1)) 330 goto err; 331 332 ok = 1; 333err: 334 if (ok) { 335 BN_free(ret->p); 336 BN_free(ret->q); 337 BN_free(ret->g); 338 ret->p = BN_dup(p); 339 ret->q = BN_dup(q); 340 ret->g = BN_dup(g); 341 if (ret->p == NULL || ret->q == NULL || ret->g == NULL) { 342 ok = 0; 343 goto err; 344 } 345 if (counter_ret != NULL) 346 *counter_ret = counter; 347 if (h_ret != NULL) 348 *h_ret = h; 349 if (seed_out != NULL) 350 memcpy(seed_out, seed, qsize); 351 } 352 BN_CTX_end(ctx); 353 BN_CTX_free(ctx); 354 BN_MONT_CTX_free(mont); 355 356 return ok; 357} 358#endif 359