1 /* $OpenBSD: dsa_gen.c,v 1.24 2017/01/21 10:38:29 beck 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_lcl.h"
72 #include "dsa_locl.h"
73
74 int
DSA_generate_parameters_ex(DSA * ret,int bits,const unsigned char * seed_in,int seed_len,int * counter_ret,unsigned long * h_ret,BN_GENCB * cb)75 DSA_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
98 int
dsa_builtin_paramgen(DSA * ret,size_t bits,size_t qbits,const EVP_MD * evpmd,const unsigned char * seed_in,size_t seed_len,unsigned char * seed_out,int * counter_ret,unsigned long * h_ret,BN_GENCB * cb)99 dsa_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 BN_CTX_start(ctx);
151
152 if ((r0 = BN_CTX_get(ctx)) == NULL)
153 goto err;
154 if ((g = BN_CTX_get(ctx)) == NULL)
155 goto err;
156 if ((W = BN_CTX_get(ctx)) == NULL)
157 goto err;
158 if ((q = BN_CTX_get(ctx)) == NULL)
159 goto err;
160 if ((X = BN_CTX_get(ctx)) == NULL)
161 goto err;
162 if ((c = BN_CTX_get(ctx)) == NULL)
163 goto err;
164 if ((p = BN_CTX_get(ctx)) == NULL)
165 goto err;
166 if ((test = BN_CTX_get(ctx)) == NULL)
167 goto err;
168
169 if (!BN_lshift(test, BN_value_one(), bits - 1))
170 goto err;
171
172 for (;;) {
173 for (;;) { /* find q */
174 int seed_is_random;
175
176 /* step 1 */
177 if (!BN_GENCB_call(cb, 0, m++))
178 goto err;
179
180 if (seed_len == 0) {
181 arc4random_buf(seed, qsize);
182 seed_is_random = 1;
183 } else {
184 seed_is_random = 0;
185 /* use random seed if 'seed_in' turns out
186 to be bad */
187 seed_len = 0;
188 }
189 memcpy(buf, seed, qsize);
190 memcpy(buf2, seed, qsize);
191 /* precompute "SEED + 1" for step 7: */
192 for (i = qsize - 1; i >= 0; i--) {
193 buf[i]++;
194 if (buf[i] != 0)
195 break;
196 }
197
198 /* step 2 */
199 if (!EVP_Digest(seed, qsize, md, NULL, evpmd, NULL))
200 goto err;
201 if (!EVP_Digest(buf, qsize, buf2, NULL, evpmd, NULL))
202 goto err;
203 for (i = 0; i < qsize; i++)
204 md[i] ^= buf2[i];
205
206 /* step 3 */
207 md[0] |= 0x80;
208 md[qsize - 1] |= 0x01;
209 if (!BN_bin2bn(md, qsize, q))
210 goto err;
211
212 /* step 4 */
213 r = BN_is_prime_fasttest_ex(q, DSS_prime_checks, ctx,
214 seed_is_random, cb);
215 if (r > 0)
216 break;
217 if (r != 0)
218 goto err;
219
220 /* do a callback call */
221 /* step 5 */
222 }
223
224 if (!BN_GENCB_call(cb, 2, 0))
225 goto err;
226 if (!BN_GENCB_call(cb, 3, 0))
227 goto err;
228
229 /* step 6 */
230 counter = 0;
231 /* "offset = 2" */
232
233 n = (bits - 1) / 160;
234
235 for (;;) {
236 if (counter != 0 && !BN_GENCB_call(cb, 0, counter))
237 goto err;
238
239 /* step 7 */
240 BN_zero(W);
241 /* now 'buf' contains "SEED + offset - 1" */
242 for (k = 0; k <= n; k++) {
243 /* obtain "SEED + offset + k" by incrementing: */
244 for (i = qsize - 1; i >= 0; i--) {
245 buf[i]++;
246 if (buf[i] != 0)
247 break;
248 }
249
250 if (!EVP_Digest(buf, qsize, md ,NULL, evpmd,
251 NULL))
252 goto err;
253
254 /* step 8 */
255 if (!BN_bin2bn(md, qsize, r0))
256 goto err;
257 if (!BN_lshift(r0, r0, (qsize << 3) * k))
258 goto err;
259 if (!BN_add(W, W, r0))
260 goto err;
261 }
262
263 /* more of step 8 */
264 if (!BN_mask_bits(W, bits - 1))
265 goto err;
266 if (!BN_copy(X, W))
267 goto err;
268 if (!BN_add(X, X, test))
269 goto err;
270
271 /* step 9 */
272 if (!BN_lshift1(r0, q))
273 goto err;
274 if (!BN_mod_ct(c, X, r0, ctx))
275 goto err;
276 if (!BN_sub(r0, c, BN_value_one()))
277 goto err;
278 if (!BN_sub(p, X, r0))
279 goto err;
280
281 /* step 10 */
282 if (BN_cmp(p, test) >= 0) {
283 /* step 11 */
284 r = BN_is_prime_fasttest_ex(p, DSS_prime_checks,
285 ctx, 1, cb);
286 if (r > 0)
287 goto end; /* found it */
288 if (r != 0)
289 goto err;
290 }
291
292 /* step 13 */
293 counter++;
294 /* "offset = offset + n + 1" */
295
296 /* step 14 */
297 if (counter >= 4096)
298 break;
299 }
300 }
301 end:
302 if (!BN_GENCB_call(cb, 2, 1))
303 goto err;
304
305 /* We now need to generate g */
306 /* Set r0=(p-1)/q */
307 if (!BN_sub(test, p, BN_value_one()))
308 goto err;
309 if (!BN_div_ct(r0, NULL, test, q, ctx))
310 goto err;
311
312 if (!BN_set_word(test, h))
313 goto err;
314 if (!BN_MONT_CTX_set(mont, p, ctx))
315 goto err;
316
317 for (;;) {
318 /* g=test^r0%p */
319 if (!BN_mod_exp_mont_ct(g, test, r0, p, ctx, mont))
320 goto err;
321 if (!BN_is_one(g))
322 break;
323 if (!BN_add(test, test, BN_value_one()))
324 goto err;
325 h++;
326 }
327
328 if (!BN_GENCB_call(cb, 3, 1))
329 goto err;
330
331 ok = 1;
332 err:
333 if (ok) {
334 BN_free(ret->p);
335 BN_free(ret->q);
336 BN_free(ret->g);
337 ret->p = BN_dup(p);
338 ret->q = BN_dup(q);
339 ret->g = BN_dup(g);
340 if (ret->p == NULL || ret->q == NULL || ret->g == NULL) {
341 ok = 0;
342 goto err;
343 }
344 if (counter_ret != NULL)
345 *counter_ret = counter;
346 if (h_ret != NULL)
347 *h_ret = h;
348 if (seed_out != NULL)
349 memcpy(seed_out, seed, qsize);
350 }
351 if (ctx) {
352 BN_CTX_end(ctx);
353 BN_CTX_free(ctx);
354 }
355 BN_MONT_CTX_free(mont);
356 return ok;
357 }
358 #endif
359