1 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
2 * All rights reserved.
3 *
4 * This package is an SSL implementation written
5 * by Eric Young (eay@cryptsoft.com).
6 * The implementation was written so as to conform with Netscapes SSL.
7 *
8 * This library is free for commercial and non-commercial use as long as
9 * the following conditions are aheared to. The following conditions
10 * apply to all code found in this distribution, be it the RC4, RSA,
11 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
12 * included with this distribution is covered by the same copyright terms
13 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
14 *
15 * Copyright remains Eric Young's, and as such any Copyright notices in
16 * the code are not to be removed.
17 * If this package is used in a product, Eric Young should be given attribution
18 * as the author of the parts of the library used.
19 * This can be in the form of a textual message at program startup or
20 * in documentation (online or textual) provided with the package.
21 *
22 * Redistribution and use in source and binary forms, with or without
23 * modification, are permitted provided that the following conditions
24 * are met:
25 * 1. Redistributions of source code must retain the copyright
26 * notice, this list of conditions and the following disclaimer.
27 * 2. Redistributions in binary form must reproduce the above copyright
28 * notice, this list of conditions and the following disclaimer in the
29 * documentation and/or other materials provided with the distribution.
30 * 3. All advertising materials mentioning features or use of this software
31 * must display the following acknowledgement:
32 * "This product includes cryptographic software written by
33 * Eric Young (eay@cryptsoft.com)"
34 * The word 'cryptographic' can be left out if the rouines from the library
35 * being used are not cryptographic related :-).
36 * 4. If you include any Windows specific code (or a derivative thereof) from
37 * the apps directory (application code) you must include an acknowledgement:
38 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
39 *
40 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
41 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
42 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
43 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
44 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
45 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
46 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
48 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
49 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50 * SUCH DAMAGE.
51 *
52 * The licence and distribution terms for any publically available version or
53 * derivative of this code cannot be changed. i.e. this code cannot simply be
54 * copied and put under another distribution licence
55 * [including the GNU Public Licence.] */
56
57 #include <openssl/dh.h>
58
59 #include <string.h>
60
61 #include <openssl/bn.h>
62 #include <openssl/buf.h>
63 #include <openssl/err.h>
64 #include <openssl/ex_data.h>
65 #include <openssl/mem.h>
66 #include <openssl/thread.h>
67
68 #include "internal.h"
69 #include "../internal.h"
70
71
72 #define OPENSSL_DH_MAX_MODULUS_BITS 10000
73
74 static CRYPTO_EX_DATA_CLASS g_ex_data_class = CRYPTO_EX_DATA_CLASS_INIT;
75
DH_new(void)76 DH *DH_new(void) {
77 DH *dh = (DH *)OPENSSL_malloc(sizeof(DH));
78 if (dh == NULL) {
79 OPENSSL_PUT_ERROR(DH, ERR_R_MALLOC_FAILURE);
80 return NULL;
81 }
82
83 memset(dh, 0, sizeof(DH));
84
85 CRYPTO_MUTEX_init(&dh->method_mont_p_lock);
86
87 dh->references = 1;
88 CRYPTO_new_ex_data(&dh->ex_data);
89
90 return dh;
91 }
92
DH_free(DH * dh)93 void DH_free(DH *dh) {
94 if (dh == NULL) {
95 return;
96 }
97
98 if (!CRYPTO_refcount_dec_and_test_zero(&dh->references)) {
99 return;
100 }
101
102 CRYPTO_free_ex_data(&g_ex_data_class, dh, &dh->ex_data);
103
104 BN_MONT_CTX_free(dh->method_mont_p);
105 BN_clear_free(dh->p);
106 BN_clear_free(dh->g);
107 BN_clear_free(dh->q);
108 BN_clear_free(dh->j);
109 OPENSSL_free(dh->seed);
110 BN_clear_free(dh->counter);
111 BN_clear_free(dh->pub_key);
112 BN_clear_free(dh->priv_key);
113 CRYPTO_MUTEX_cleanup(&dh->method_mont_p_lock);
114
115 OPENSSL_free(dh);
116 }
117
DH_generate_parameters_ex(DH * dh,int prime_bits,int generator,BN_GENCB * cb)118 int DH_generate_parameters_ex(DH *dh, int prime_bits, int generator, BN_GENCB *cb) {
119 /* We generate DH parameters as follows
120 * find a prime q which is prime_bits/2 bits long.
121 * p=(2*q)+1 or (p-1)/2 = q
122 * For this case, g is a generator if
123 * g^((p-1)/q) mod p != 1 for values of q which are the factors of p-1.
124 * Since the factors of p-1 are q and 2, we just need to check
125 * g^2 mod p != 1 and g^q mod p != 1.
126 *
127 * Having said all that,
128 * there is another special case method for the generators 2, 3 and 5.
129 * for 2, p mod 24 == 11
130 * for 3, p mod 12 == 5 <<<<< does not work for safe primes.
131 * for 5, p mod 10 == 3 or 7
132 *
133 * Thanks to Phil Karn <karn@qualcomm.com> for the pointers about the
134 * special generators and for answering some of my questions.
135 *
136 * I've implemented the second simple method :-).
137 * Since DH should be using a safe prime (both p and q are prime),
138 * this generator function can take a very very long time to run.
139 */
140
141 /* Actually there is no reason to insist that 'generator' be a generator.
142 * It's just as OK (and in some sense better) to use a generator of the
143 * order-q subgroup.
144 */
145
146 BIGNUM *t1, *t2;
147 int g, ok = 0;
148 BN_CTX *ctx = NULL;
149
150 ctx = BN_CTX_new();
151 if (ctx == NULL) {
152 goto err;
153 }
154 BN_CTX_start(ctx);
155 t1 = BN_CTX_get(ctx);
156 t2 = BN_CTX_get(ctx);
157 if (t1 == NULL || t2 == NULL) {
158 goto err;
159 }
160
161 /* Make sure |dh| has the necessary elements */
162 if (dh->p == NULL) {
163 dh->p = BN_new();
164 if (dh->p == NULL) {
165 goto err;
166 }
167 }
168 if (dh->g == NULL) {
169 dh->g = BN_new();
170 if (dh->g == NULL) {
171 goto err;
172 }
173 }
174
175 if (generator <= 1) {
176 OPENSSL_PUT_ERROR(DH, DH_R_BAD_GENERATOR);
177 goto err;
178 }
179 if (generator == DH_GENERATOR_2) {
180 if (!BN_set_word(t1, 24)) {
181 goto err;
182 }
183 if (!BN_set_word(t2, 11)) {
184 goto err;
185 }
186 g = 2;
187 } else if (generator == DH_GENERATOR_5) {
188 if (!BN_set_word(t1, 10)) {
189 goto err;
190 }
191 if (!BN_set_word(t2, 3)) {
192 goto err;
193 }
194 /* BN_set_word(t3,7); just have to miss
195 * out on these ones :-( */
196 g = 5;
197 } else {
198 /* in the general case, don't worry if 'generator' is a
199 * generator or not: since we are using safe primes,
200 * it will generate either an order-q or an order-2q group,
201 * which both is OK */
202 if (!BN_set_word(t1, 2)) {
203 goto err;
204 }
205 if (!BN_set_word(t2, 1)) {
206 goto err;
207 }
208 g = generator;
209 }
210
211 if (!BN_generate_prime_ex(dh->p, prime_bits, 1, t1, t2, cb)) {
212 goto err;
213 }
214 if (!BN_GENCB_call(cb, 3, 0)) {
215 goto err;
216 }
217 if (!BN_set_word(dh->g, g)) {
218 goto err;
219 }
220 ok = 1;
221
222 err:
223 if (!ok) {
224 OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB);
225 }
226
227 if (ctx != NULL) {
228 BN_CTX_end(ctx);
229 BN_CTX_free(ctx);
230 }
231 return ok;
232 }
233
DH_generate_key(DH * dh)234 int DH_generate_key(DH *dh) {
235 int ok = 0;
236 int generate_new_key = 0;
237 unsigned l;
238 BN_CTX *ctx = NULL;
239 BN_MONT_CTX *mont = NULL;
240 BIGNUM *pub_key = NULL, *priv_key = NULL;
241 BIGNUM local_priv;
242
243 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
244 OPENSSL_PUT_ERROR(DH, DH_R_MODULUS_TOO_LARGE);
245 goto err;
246 }
247
248 ctx = BN_CTX_new();
249 if (ctx == NULL) {
250 goto err;
251 }
252
253 if (dh->priv_key == NULL) {
254 priv_key = BN_new();
255 if (priv_key == NULL) {
256 goto err;
257 }
258 generate_new_key = 1;
259 } else {
260 priv_key = dh->priv_key;
261 }
262
263 if (dh->pub_key == NULL) {
264 pub_key = BN_new();
265 if (pub_key == NULL) {
266 goto err;
267 }
268 } else {
269 pub_key = dh->pub_key;
270 }
271
272 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, &dh->method_mont_p_lock,
273 dh->p, ctx);
274 if (!mont) {
275 goto err;
276 }
277
278 if (generate_new_key) {
279 if (dh->q) {
280 do {
281 if (!BN_rand_range(priv_key, dh->q)) {
282 goto err;
283 }
284 } while (BN_is_zero(priv_key) || BN_is_one(priv_key));
285 } else {
286 /* secret exponent length */
287 DH_check_standard_parameters(dh);
288 l = dh->priv_length ? dh->priv_length : BN_num_bits(dh->p) - 1;
289 if (!BN_rand(priv_key, l, 0, 0)) {
290 goto err;
291 }
292 }
293 }
294
295 BN_with_flags(&local_priv, priv_key, BN_FLG_CONSTTIME);
296 if (!BN_mod_exp_mont(pub_key, dh->g, &local_priv, dh->p, ctx, mont)) {
297 goto err;
298 }
299
300 dh->pub_key = pub_key;
301 dh->priv_key = priv_key;
302 ok = 1;
303
304 err:
305 if (ok != 1) {
306 OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB);
307 }
308
309 if (dh->pub_key == NULL) {
310 BN_free(pub_key);
311 }
312 if (dh->priv_key == NULL) {
313 BN_free(priv_key);
314 }
315 BN_CTX_free(ctx);
316 return ok;
317 }
318
DH_compute_key(unsigned char * out,const BIGNUM * peers_key,DH * dh)319 int DH_compute_key(unsigned char *out, const BIGNUM *peers_key, DH *dh) {
320 BN_CTX *ctx = NULL;
321 BN_MONT_CTX *mont = NULL;
322 BIGNUM *shared_key;
323 int ret = -1;
324 int check_result;
325 BIGNUM local_priv;
326
327 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
328 OPENSSL_PUT_ERROR(DH, DH_R_MODULUS_TOO_LARGE);
329 goto err;
330 }
331
332 ctx = BN_CTX_new();
333 if (ctx == NULL) {
334 goto err;
335 }
336 BN_CTX_start(ctx);
337 shared_key = BN_CTX_get(ctx);
338 if (shared_key == NULL) {
339 goto err;
340 }
341
342 if (dh->priv_key == NULL) {
343 OPENSSL_PUT_ERROR(DH, DH_R_NO_PRIVATE_VALUE);
344 goto err;
345 }
346
347 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, &dh->method_mont_p_lock,
348 dh->p, ctx);
349 if (!mont) {
350 goto err;
351 }
352
353 if (!DH_check_pub_key(dh, peers_key, &check_result) || check_result) {
354 OPENSSL_PUT_ERROR(DH, DH_R_INVALID_PUBKEY);
355 goto err;
356 }
357
358 BN_with_flags(&local_priv, dh->priv_key, BN_FLG_CONSTTIME);
359 if (!BN_mod_exp_mont(shared_key, peers_key, &local_priv, dh->p, ctx,
360 mont)) {
361 OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB);
362 goto err;
363 }
364
365 ret = BN_bn2bin(shared_key, out);
366
367 err:
368 if (ctx != NULL) {
369 BN_CTX_end(ctx);
370 BN_CTX_free(ctx);
371 }
372
373 return ret;
374 }
375
DH_size(const DH * dh)376 int DH_size(const DH *dh) { return BN_num_bytes(dh->p); }
377
DH_num_bits(const DH * dh)378 unsigned DH_num_bits(const DH *dh) { return BN_num_bits(dh->p); }
379
DH_up_ref(DH * dh)380 int DH_up_ref(DH *dh) {
381 CRYPTO_refcount_inc(&dh->references);
382 return 1;
383 }
384
int_dh_bn_cpy(BIGNUM ** dst,const BIGNUM * src)385 static int int_dh_bn_cpy(BIGNUM **dst, const BIGNUM *src) {
386 BIGNUM *a = NULL;
387
388 if (src) {
389 a = BN_dup(src);
390 if (!a) {
391 return 0;
392 }
393 }
394
395 BN_free(*dst);
396 *dst = a;
397 return 1;
398 }
399
int_dh_param_copy(DH * to,const DH * from,int is_x942)400 static int int_dh_param_copy(DH *to, const DH *from, int is_x942) {
401 if (is_x942 == -1) {
402 is_x942 = !!from->q;
403 }
404 if (!int_dh_bn_cpy(&to->p, from->p) ||
405 !int_dh_bn_cpy(&to->g, from->g)) {
406 return 0;
407 }
408
409 if (!is_x942) {
410 return 1;
411 }
412
413 if (!int_dh_bn_cpy(&to->q, from->q) ||
414 !int_dh_bn_cpy(&to->j, from->j)) {
415 return 0;
416 }
417
418 OPENSSL_free(to->seed);
419 to->seed = NULL;
420 to->seedlen = 0;
421
422 if (from->seed) {
423 to->seed = BUF_memdup(from->seed, from->seedlen);
424 if (!to->seed) {
425 return 0;
426 }
427 to->seedlen = from->seedlen;
428 }
429
430 return 1;
431 }
432
DHparams_dup(const DH * dh)433 DH *DHparams_dup(const DH *dh) {
434 DH *ret = DH_new();
435 if (!ret) {
436 return NULL;
437 }
438
439 if (!int_dh_param_copy(ret, dh, -1)) {
440 DH_free(ret);
441 return NULL;
442 }
443
444 return ret;
445 }
446
DH_get_ex_new_index(long argl,void * argp,CRYPTO_EX_unused * unused,CRYPTO_EX_dup * dup_func,CRYPTO_EX_free * free_func)447 int DH_get_ex_new_index(long argl, void *argp, CRYPTO_EX_unused *unused,
448 CRYPTO_EX_dup *dup_func, CRYPTO_EX_free *free_func) {
449 int index;
450 if (!CRYPTO_get_ex_new_index(&g_ex_data_class, &index, argl, argp, dup_func,
451 free_func)) {
452 return -1;
453 }
454 return index;
455 }
456
DH_set_ex_data(DH * d,int idx,void * arg)457 int DH_set_ex_data(DH *d, int idx, void *arg) {
458 return CRYPTO_set_ex_data(&d->ex_data, idx, arg);
459 }
460
DH_get_ex_data(DH * d,int idx)461 void *DH_get_ex_data(DH *d, int idx) {
462 return CRYPTO_get_ex_data(&d->ex_data, idx);
463 }
464