1 /* $OpenBSD: dsa_gen.c,v 1.33 2024/12/05 19:34:46 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 74 /* 75 * Primality test according to FIPS PUB 186-4, Appendix C.3. Set the number 76 * to 64 rounds of Miller-Rabin, which corresponds to 128 bits of security. 77 * This is necessary for keys of size >= 3072. 78 * XXX - now that we do BPSW the recommendation is to do 2 for p and 27 for q. 79 */ 80 #define DSA_prime_checks 64 81 82 int 83 DSA_generate_parameters_ex(DSA *ret, int bits, const unsigned char *seed_in, 84 int seed_len, int *counter_ret, unsigned long *h_ret, BN_GENCB *cb) 85 { 86 const EVP_MD *evpmd; 87 size_t qbits; 88 89 if (bits >= 2048) { 90 qbits = 256; 91 evpmd = EVP_sha256(); 92 } else { 93 qbits = 160; 94 evpmd = EVP_sha1(); 95 } 96 97 return dsa_builtin_paramgen(ret, bits, qbits, evpmd, seed_in, seed_len, 98 NULL, counter_ret, h_ret, cb); 99 } 100 LCRYPTO_ALIAS(DSA_generate_parameters_ex); 101 102 int 103 dsa_builtin_paramgen(DSA *ret, size_t bits, size_t qbits, const EVP_MD *evpmd, 104 const unsigned char *seed_in, size_t seed_len, unsigned char *seed_out, 105 int *counter_ret, unsigned long *h_ret, BN_GENCB *cb) 106 { 107 int ok = 0; 108 unsigned char seed[SHA256_DIGEST_LENGTH]; 109 unsigned char md[SHA256_DIGEST_LENGTH]; 110 unsigned char buf[SHA256_DIGEST_LENGTH], buf2[SHA256_DIGEST_LENGTH]; 111 BIGNUM *r0, *W, *X, *c, *test; 112 BIGNUM *g = NULL, *q = NULL, *p = NULL; 113 BN_MONT_CTX *mont = NULL; 114 int i, k, n = 0, m = 0, qsize = qbits >> 3; 115 int counter = 0; 116 int r = 0; 117 BN_CTX *ctx = NULL; 118 unsigned int h = 2; 119 120 if (qsize != SHA_DIGEST_LENGTH && qsize != SHA224_DIGEST_LENGTH && 121 qsize != SHA256_DIGEST_LENGTH) 122 /* invalid q size */ 123 return 0; 124 125 if (evpmd == NULL) 126 /* use SHA1 as default */ 127 evpmd = EVP_sha1(); 128 129 if (bits < 512) 130 bits = 512; 131 132 bits = (bits + 63) / 64 * 64; 133 134 if (seed_len < (size_t)qsize) { 135 seed_in = NULL; /* seed buffer too small -- ignore */ 136 seed_len = 0; 137 } 138 /* 139 * App. 2.2 of FIPS PUB 186 allows larger SEED, 140 * but our internal buffers are restricted to 160 bits 141 */ 142 if (seed_len > (size_t)qsize) 143 seed_len = qsize; 144 if (seed_in != NULL) 145 memcpy(seed, seed_in, seed_len); 146 else if (seed_len != 0) 147 goto err; 148 149 if ((mont = BN_MONT_CTX_new()) == NULL) 150 goto err; 151 152 if ((ctx = BN_CTX_new()) == NULL) 153 goto err; 154 155 BN_CTX_start(ctx); 156 157 if ((r0 = BN_CTX_get(ctx)) == NULL) 158 goto err; 159 if ((g = BN_CTX_get(ctx)) == NULL) 160 goto err; 161 if ((W = BN_CTX_get(ctx)) == NULL) 162 goto err; 163 if ((q = BN_CTX_get(ctx)) == NULL) 164 goto err; 165 if ((X = BN_CTX_get(ctx)) == NULL) 166 goto err; 167 if ((c = BN_CTX_get(ctx)) == NULL) 168 goto err; 169 if ((p = BN_CTX_get(ctx)) == NULL) 170 goto err; 171 if ((test = BN_CTX_get(ctx)) == NULL) 172 goto err; 173 174 if (!BN_lshift(test, BN_value_one(), bits - 1)) 175 goto err; 176 177 for (;;) { 178 for (;;) { /* find q */ 179 int seed_is_random; 180 181 /* step 1 */ 182 if (!BN_GENCB_call(cb, 0, m++)) 183 goto err; 184 185 if (seed_len == 0) { 186 arc4random_buf(seed, qsize); 187 seed_is_random = 1; 188 } else { 189 seed_is_random = 0; 190 /* use random seed if 'seed_in' turns out 191 to be bad */ 192 seed_len = 0; 193 } 194 memcpy(buf, seed, qsize); 195 memcpy(buf2, seed, qsize); 196 /* precompute "SEED + 1" for step 7: */ 197 for (i = qsize - 1; i >= 0; i--) { 198 buf[i]++; 199 if (buf[i] != 0) 200 break; 201 } 202 203 /* step 2 */ 204 if (!EVP_Digest(seed, qsize, md, NULL, evpmd, NULL)) 205 goto err; 206 if (!EVP_Digest(buf, qsize, buf2, NULL, evpmd, NULL)) 207 goto err; 208 for (i = 0; i < qsize; i++) 209 md[i] ^= buf2[i]; 210 211 /* step 3 */ 212 md[0] |= 0x80; 213 md[qsize - 1] |= 0x01; 214 if (!BN_bin2bn(md, qsize, q)) 215 goto err; 216 217 /* step 4 */ 218 r = BN_is_prime_fasttest_ex(q, DSA_prime_checks, ctx, 219 seed_is_random, cb); 220 if (r > 0) 221 break; 222 if (r != 0) 223 goto err; 224 225 /* do a callback call */ 226 /* step 5 */ 227 } 228 229 if (!BN_GENCB_call(cb, 2, 0)) 230 goto err; 231 if (!BN_GENCB_call(cb, 3, 0)) 232 goto err; 233 234 /* step 6 */ 235 counter = 0; 236 /* "offset = 2" */ 237 238 n = (bits - 1) / 160; 239 240 for (;;) { 241 if (counter != 0 && !BN_GENCB_call(cb, 0, counter)) 242 goto err; 243 244 /* step 7 */ 245 BN_zero(W); 246 /* now 'buf' contains "SEED + offset - 1" */ 247 for (k = 0; k <= n; k++) { 248 /* obtain "SEED + offset + k" by incrementing: */ 249 for (i = qsize - 1; i >= 0; i--) { 250 buf[i]++; 251 if (buf[i] != 0) 252 break; 253 } 254 255 if (!EVP_Digest(buf, qsize, md ,NULL, evpmd, 256 NULL)) 257 goto err; 258 259 /* step 8 */ 260 if (!BN_bin2bn(md, qsize, r0)) 261 goto err; 262 if (!BN_lshift(r0, r0, (qsize << 3) * k)) 263 goto err; 264 if (!BN_add(W, W, r0)) 265 goto err; 266 } 267 268 /* more of step 8 */ 269 if (!BN_mask_bits(W, bits - 1)) 270 goto err; 271 if (!bn_copy(X, W)) 272 goto err; 273 if (!BN_add(X, X, test)) 274 goto err; 275 276 /* step 9 */ 277 if (!BN_lshift1(r0, q)) 278 goto err; 279 if (!BN_mod_ct(c, X, r0, ctx)) 280 goto err; 281 if (!BN_sub(r0, c, BN_value_one())) 282 goto err; 283 if (!BN_sub(p, X, r0)) 284 goto err; 285 286 /* step 10 */ 287 if (BN_cmp(p, test) >= 0) { 288 /* step 11 */ 289 r = BN_is_prime_fasttest_ex(p, DSA_prime_checks, 290 ctx, 1, cb); 291 if (r > 0) 292 goto end; /* found it */ 293 if (r != 0) 294 goto err; 295 } 296 297 /* step 13 */ 298 counter++; 299 /* "offset = offset + n + 1" */ 300 301 /* step 14 */ 302 if (counter >= 4096) 303 break; 304 } 305 } 306 end: 307 if (!BN_GENCB_call(cb, 2, 1)) 308 goto err; 309 310 /* We now need to generate g */ 311 /* Set r0=(p-1)/q */ 312 if (!BN_sub(test, p, BN_value_one())) 313 goto err; 314 if (!BN_div_ct(r0, NULL, test, q, ctx)) 315 goto err; 316 317 if (!BN_set_word(test, h)) 318 goto err; 319 if (!BN_MONT_CTX_set(mont, p, ctx)) 320 goto err; 321 322 for (;;) { 323 /* g=test^r0%p */ 324 if (!BN_mod_exp_mont_ct(g, test, r0, p, ctx, mont)) 325 goto err; 326 if (!BN_is_one(g)) 327 break; 328 if (!BN_add(test, test, BN_value_one())) 329 goto err; 330 h++; 331 } 332 333 if (!BN_GENCB_call(cb, 3, 1)) 334 goto err; 335 336 ok = 1; 337 err: 338 if (ok) { 339 BN_free(ret->p); 340 BN_free(ret->q); 341 BN_free(ret->g); 342 ret->p = BN_dup(p); 343 ret->q = BN_dup(q); 344 ret->g = BN_dup(g); 345 if (ret->p == NULL || ret->q == NULL || ret->g == NULL) { 346 ok = 0; 347 goto err; 348 } 349 if (counter_ret != NULL) 350 *counter_ret = counter; 351 if (h_ret != NULL) 352 *h_ret = h; 353 if (seed_out != NULL) 354 memcpy(seed_out, seed, qsize); 355 } 356 BN_CTX_end(ctx); 357 BN_CTX_free(ctx); 358 BN_MONT_CTX_free(mont); 359 360 return ok; 361 } 362 363 #endif 364