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