dsa_gen.c revision 291721 
1/* crypto/dsa/dsa_gen.c */
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#undef GENUINE_DSA
60
61#ifdef GENUINE_DSA
62/*
63 * Parameter generation follows the original release of FIPS PUB 186,
64 * Appendix 2.2 (i.e. use SHA as defined in FIPS PUB 180)
65 */
66# define HASH    EVP_sha()
67#else
68/*
69 * Parameter generation follows the updated Appendix 2.2 for FIPS PUB 186,
70 * also Appendix 2.2 of FIPS PUB 186-1 (i.e. use SHA as defined in FIPS PUB
71 * 180-1)
72 */
73# define HASH    EVP_sha1()
74#endif
75
76#include <openssl/opensslconf.h> /* To see if OPENSSL_NO_SHA is defined */
77
78#ifndef OPENSSL_NO_SHA
79
80# include <stdio.h>
81# include "cryptlib.h"
82# include <openssl/evp.h>
83# include <openssl/bn.h>
84# include <openssl/rand.h>
85# include <openssl/sha.h>
86# include "dsa_locl.h"
87
88# ifdef OPENSSL_FIPS
89#  include <openssl/fips.h>
90# endif
91
92int DSA_generate_parameters_ex(DSA *ret, int bits,
93                               const unsigned char *seed_in, int seed_len,
94                               int *counter_ret, unsigned long *h_ret,
95                               BN_GENCB *cb)
96{
97# ifdef OPENSSL_FIPS
98    if (FIPS_mode() && !(ret->meth->flags & DSA_FLAG_FIPS_METHOD)
99        && !(ret->flags & DSA_FLAG_NON_FIPS_ALLOW)) {
100        DSAerr(DSA_F_DSA_GENERATE_PARAMETERS_EX, DSA_R_NON_FIPS_DSA_METHOD);
101        return 0;
102    }
103# endif
104    if (ret->meth->dsa_paramgen)
105        return ret->meth->dsa_paramgen(ret, bits, seed_in, seed_len,
106                                       counter_ret, h_ret, cb);
107# ifdef OPENSSL_FIPS
108    else if (FIPS_mode()) {
109        return FIPS_dsa_generate_parameters_ex(ret, bits,
110                                               seed_in, seed_len,
111                                               counter_ret, h_ret, cb);
112    }
113# endif
114    else {
115        const EVP_MD *evpmd = bits >= 2048 ? EVP_sha256() : EVP_sha1();
116        size_t qbits = EVP_MD_size(evpmd) * 8;
117
118        return dsa_builtin_paramgen(ret, bits, qbits, evpmd,
119                                    seed_in, seed_len, NULL, counter_ret,
120                                    h_ret, cb);
121    }
122}
123
124int dsa_builtin_paramgen(DSA *ret, size_t bits, size_t qbits,
125                         const EVP_MD *evpmd, const unsigned char *seed_in,
126                         size_t seed_len, unsigned char *seed_out,
127                         int *counter_ret, unsigned long *h_ret, BN_GENCB *cb)
128{
129    int ok = 0;
130    unsigned char seed[SHA256_DIGEST_LENGTH];
131    unsigned char md[SHA256_DIGEST_LENGTH];
132    unsigned char buf[SHA256_DIGEST_LENGTH], buf2[SHA256_DIGEST_LENGTH];
133    BIGNUM *r0, *W, *X, *c, *test;
134    BIGNUM *g = NULL, *q = NULL, *p = NULL;
135    BN_MONT_CTX *mont = NULL;
136    int i, k, n = 0, m = 0, qsize = qbits >> 3;
137    int counter = 0;
138    int r = 0;
139    BN_CTX *ctx = NULL;
140    unsigned int h = 2;
141
142    if (qsize != SHA_DIGEST_LENGTH && qsize != SHA224_DIGEST_LENGTH &&
143        qsize != SHA256_DIGEST_LENGTH)
144        /* invalid q size */
145        return 0;
146
147    if (evpmd == NULL)
148        /* use SHA1 as default */
149        evpmd = EVP_sha1();
150
151    if (bits < 512)
152        bits = 512;
153
154    bits = (bits + 63) / 64 * 64;
155
156    /*
157     * NB: seed_len == 0 is special case: copy generated seed to seed_in if
158     * it is not NULL.
159     */
160    if (seed_len && (seed_len < (size_t)qsize))
161        seed_in = NULL;         /* seed buffer too small -- ignore */
162    if (seed_len > (size_t)qsize)
163        seed_len = qsize;       /* App. 2.2 of FIPS PUB 186 allows larger
164                                 * SEED, but our internal buffers are
165                                 * restricted to 160 bits */
166    if (seed_in != NULL)
167        memcpy(seed, seed_in, seed_len);
168
169    if ((mont = BN_MONT_CTX_new()) == NULL)
170        goto err;
171
172    if ((ctx = BN_CTX_new()) == NULL)
173        goto err;
174
175    BN_CTX_start(ctx);
176
177    r0 = BN_CTX_get(ctx);
178    g = BN_CTX_get(ctx);
179    W = BN_CTX_get(ctx);
180    q = BN_CTX_get(ctx);
181    X = BN_CTX_get(ctx);
182    c = BN_CTX_get(ctx);
183    p = BN_CTX_get(ctx);
184    test = BN_CTX_get(ctx);
185
186    if (!BN_lshift(test, BN_value_one(), bits - 1))
187        goto err;
188
189    for (;;) {
190        for (;;) {              /* find q */
191            int seed_is_random;
192
193            /* step 1 */
194            if (!BN_GENCB_call(cb, 0, m++))
195                goto err;
196
197            if (!seed_len || !seed_in) {
198                if (RAND_pseudo_bytes(seed, qsize) < 0)
199                    goto err;
200                seed_is_random = 1;
201            } else {
202                seed_is_random = 0;
203                seed_len = 0;   /* use random seed if 'seed_in' turns out to
204                                 * be bad */
205            }
206            memcpy(buf, seed, qsize);
207            memcpy(buf2, seed, qsize);
208            /* precompute "SEED + 1" for step 7: */
209            for (i = qsize - 1; i >= 0; i--) {
210                buf[i]++;
211                if (buf[i] != 0)
212                    break;
213            }
214
215            /* step 2 */
216            if (!EVP_Digest(seed, qsize, md, NULL, evpmd, NULL))
217                goto err;
218            if (!EVP_Digest(buf, qsize, buf2, NULL, evpmd, NULL))
219                goto err;
220            for (i = 0; i < qsize; i++)
221                md[i] ^= buf2[i];
222
223            /* step 3 */
224            md[0] |= 0x80;
225            md[qsize - 1] |= 0x01;
226            if (!BN_bin2bn(md, qsize, q))
227                goto err;
228
229            /* step 4 */
230            r = BN_is_prime_fasttest_ex(q, DSS_prime_checks, ctx,
231                                        seed_is_random, cb);
232            if (r > 0)
233                break;
234            if (r != 0)
235                goto err;
236
237            /* do a callback call */
238            /* step 5 */
239        }
240
241        if (!BN_GENCB_call(cb, 2, 0))
242            goto err;
243        if (!BN_GENCB_call(cb, 3, 0))
244            goto err;
245
246        /* step 6 */
247        counter = 0;
248        /* "offset = 2" */
249
250        n = (bits - 1) / 160;
251
252        for (;;) {
253            if ((counter != 0) && !BN_GENCB_call(cb, 0, counter))
254                goto err;
255
256            /* step 7 */
257            BN_zero(W);
258            /* now 'buf' contains "SEED + offset - 1" */
259            for (k = 0; k <= n; k++) {
260                /*
261                 * obtain "SEED + offset + k" by incrementing:
262                 */
263                for (i = qsize - 1; i >= 0; i--) {
264                    buf[i]++;
265                    if (buf[i] != 0)
266                        break;
267                }
268
269                if (!EVP_Digest(buf, qsize, md, NULL, evpmd, NULL))
270                    goto err;
271
272                /* step 8 */
273                if (!BN_bin2bn(md, qsize, r0))
274                    goto err;
275                if (!BN_lshift(r0, r0, (qsize << 3) * k))
276                    goto err;
277                if (!BN_add(W, W, r0))
278                    goto err;
279            }
280
281            /* more of step 8 */
282            if (!BN_mask_bits(W, bits - 1))
283                goto err;
284            if (!BN_copy(X, W))
285                goto err;
286            if (!BN_add(X, X, test))
287                goto err;
288
289            /* step 9 */
290            if (!BN_lshift1(r0, q))
291                goto err;
292            if (!BN_mod(c, X, r0, ctx))
293                goto err;
294            if (!BN_sub(r0, c, BN_value_one()))
295                goto err;
296            if (!BN_sub(p, X, r0))
297                goto err;
298
299            /* step 10 */
300            if (BN_cmp(p, test) >= 0) {
301                /* step 11 */
302                r = BN_is_prime_fasttest_ex(p, DSS_prime_checks, ctx, 1, cb);
303                if (r > 0)
304                    goto end;   /* found it */
305                if (r != 0)
306                    goto err;
307            }
308
309            /* step 13 */
310            counter++;
311            /* "offset = offset + n + 1" */
312
313            /* step 14 */
314            if (counter >= 4096)
315                break;
316        }
317    }
318 end:
319    if (!BN_GENCB_call(cb, 2, 1))
320        goto err;
321
322    /* We now need to generate g */
323    /* Set r0=(p-1)/q */
324    if (!BN_sub(test, p, BN_value_one()))
325        goto err;
326    if (!BN_div(r0, NULL, test, q, ctx))
327        goto err;
328
329    if (!BN_set_word(test, h))
330        goto err;
331    if (!BN_MONT_CTX_set(mont, p, ctx))
332        goto err;
333
334    for (;;) {
335        /* g=test^r0%p */
336        if (!BN_mod_exp_mont(g, test, r0, p, ctx, mont))
337            goto err;
338        if (!BN_is_one(g))
339            break;
340        if (!BN_add(test, test, BN_value_one()))
341            goto err;
342        h++;
343    }
344
345    if (!BN_GENCB_call(cb, 3, 1))
346        goto err;
347
348    ok = 1;
349 err:
350    if (ok) {
351        if (ret->p)
352            BN_free(ret->p);
353        if (ret->q)
354            BN_free(ret->q);
355        if (ret->g)
356            BN_free(ret->g);
357        ret->p = BN_dup(p);
358        ret->q = BN_dup(q);
359        ret->g = BN_dup(g);
360        if (ret->p == NULL || ret->q == NULL || ret->g == NULL) {
361            ok = 0;
362            goto err;
363        }
364        if (counter_ret != NULL)
365            *counter_ret = counter;
366        if (h_ret != NULL)
367            *h_ret = h;
368        if (seed_out)
369            memcpy(seed_out, seed, qsize);
370    }
371    if (ctx) {
372        BN_CTX_end(ctx);
373        BN_CTX_free(ctx);
374    }
375    if (mont != NULL)
376        BN_MONT_CTX_free(mont);
377    return ok;
378}
379#endif
380