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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 
70 
71 #define OPENSSL_DH_MAX_MODULUS_BITS 10000
72 
73 static CRYPTO_EX_DATA_CLASS g_ex_data_class = CRYPTO_EX_DATA_CLASS_INIT;
74 
DH_new(void)75 DH *DH_new(void) {
76   DH *dh = OPENSSL_malloc(sizeof(DH));
77   if (dh == NULL) {
78     OPENSSL_PUT_ERROR(DH, ERR_R_MALLOC_FAILURE);
79     return NULL;
80   }
81 
82   OPENSSL_memset(dh, 0, sizeof(DH));
83 
84   CRYPTO_MUTEX_init(&dh->method_mont_p_lock);
85 
86   dh->references = 1;
87   CRYPTO_new_ex_data(&dh->ex_data);
88 
89   return dh;
90 }
91 
DH_free(DH * dh)92 void DH_free(DH *dh) {
93   if (dh == NULL) {
94     return;
95   }
96 
97   if (!CRYPTO_refcount_dec_and_test_zero(&dh->references)) {
98     return;
99   }
100 
101   CRYPTO_free_ex_data(&g_ex_data_class, dh, &dh->ex_data);
102 
103   BN_MONT_CTX_free(dh->method_mont_p);
104   BN_clear_free(dh->p);
105   BN_clear_free(dh->g);
106   BN_clear_free(dh->q);
107   BN_clear_free(dh->j);
108   OPENSSL_free(dh->seed);
109   BN_clear_free(dh->counter);
110   BN_clear_free(dh->pub_key);
111   BN_clear_free(dh->priv_key);
112   CRYPTO_MUTEX_cleanup(&dh->method_mont_p_lock);
113 
114   OPENSSL_free(dh);
115 }
116 
DH_get0_key(const DH * dh,const BIGNUM ** out_pub_key,const BIGNUM ** out_priv_key)117 void DH_get0_key(const DH *dh, const BIGNUM **out_pub_key,
118                  const BIGNUM **out_priv_key) {
119   if (out_pub_key != NULL) {
120     *out_pub_key = dh->pub_key;
121   }
122   if (out_priv_key != NULL) {
123     *out_priv_key = dh->priv_key;
124   }
125 }
126 
DH_set0_key(DH * dh,BIGNUM * pub_key,BIGNUM * priv_key)127 int DH_set0_key(DH *dh, BIGNUM *pub_key, BIGNUM *priv_key) {
128   if (pub_key != NULL) {
129     BN_free(dh->pub_key);
130     dh->pub_key = pub_key;
131   }
132 
133   if (priv_key != NULL) {
134     BN_free(dh->priv_key);
135     dh->priv_key = priv_key;
136   }
137 
138   return 1;
139 }
140 
DH_get0_pqg(const DH * dh,const BIGNUM ** out_p,const BIGNUM ** out_q,const BIGNUM ** out_g)141 void DH_get0_pqg(const DH *dh, const BIGNUM **out_p, const BIGNUM **out_q,
142                  const BIGNUM **out_g) {
143   if (out_p != NULL) {
144     *out_p = dh->p;
145   }
146   if (out_q != NULL) {
147     *out_q = dh->q;
148   }
149   if (out_g != NULL) {
150     *out_g = dh->g;
151   }
152 }
153 
DH_set0_pqg(DH * dh,BIGNUM * p,BIGNUM * q,BIGNUM * g)154 int DH_set0_pqg(DH *dh, BIGNUM *p, BIGNUM *q, BIGNUM *g) {
155   if ((dh->p == NULL && p == NULL) ||
156       (dh->g == NULL && g == NULL)) {
157     return 0;
158   }
159 
160   if (p != NULL) {
161     BN_free(dh->p);
162     dh->p = p;
163   }
164 
165   if (q != NULL) {
166     BN_free(dh->q);
167     dh->q = q;
168   }
169 
170   if (g != NULL) {
171     BN_free(dh->g);
172     dh->g = g;
173   }
174 
175   return 1;
176 }
177 
DH_generate_parameters_ex(DH * dh,int prime_bits,int generator,BN_GENCB * cb)178 int DH_generate_parameters_ex(DH *dh, int prime_bits, int generator, BN_GENCB *cb) {
179   // We generate DH parameters as follows
180   // find a prime q which is prime_bits/2 bits long.
181   // p=(2*q)+1 or (p-1)/2 = q
182   // For this case, g is a generator if
183   // g^((p-1)/q) mod p != 1 for values of q which are the factors of p-1.
184   // Since the factors of p-1 are q and 2, we just need to check
185   // g^2 mod p != 1 and g^q mod p != 1.
186   //
187   // Having said all that,
188   // there is another special case method for the generators 2, 3 and 5.
189   // for 2, p mod 24 == 11
190   // for 3, p mod 12 == 5  <<<<< does not work for safe primes.
191   // for 5, p mod 10 == 3 or 7
192   //
193   // Thanks to Phil Karn <karn@qualcomm.com> for the pointers about the
194   // special generators and for answering some of my questions.
195   //
196   // I've implemented the second simple method :-).
197   // Since DH should be using a safe prime (both p and q are prime),
198   // this generator function can take a very very long time to run.
199 
200   // Actually there is no reason to insist that 'generator' be a generator.
201   // It's just as OK (and in some sense better) to use a generator of the
202   // order-q subgroup.
203 
204   BIGNUM *t1, *t2;
205   int g, ok = 0;
206   BN_CTX *ctx = NULL;
207 
208   ctx = BN_CTX_new();
209   if (ctx == NULL) {
210     goto err;
211   }
212   BN_CTX_start(ctx);
213   t1 = BN_CTX_get(ctx);
214   t2 = BN_CTX_get(ctx);
215   if (t1 == NULL || t2 == NULL) {
216     goto err;
217   }
218 
219   // Make sure |dh| has the necessary elements
220   if (dh->p == NULL) {
221     dh->p = BN_new();
222     if (dh->p == NULL) {
223       goto err;
224     }
225   }
226   if (dh->g == NULL) {
227     dh->g = BN_new();
228     if (dh->g == NULL) {
229       goto err;
230     }
231   }
232 
233   if (generator <= 1) {
234     OPENSSL_PUT_ERROR(DH, DH_R_BAD_GENERATOR);
235     goto err;
236   }
237   if (generator == DH_GENERATOR_2) {
238     if (!BN_set_word(t1, 24)) {
239       goto err;
240     }
241     if (!BN_set_word(t2, 11)) {
242       goto err;
243     }
244     g = 2;
245   } else if (generator == DH_GENERATOR_5) {
246     if (!BN_set_word(t1, 10)) {
247       goto err;
248     }
249     if (!BN_set_word(t2, 3)) {
250       goto err;
251     }
252     // BN_set_word(t3,7); just have to miss
253     // out on these ones :-(
254     g = 5;
255   } else {
256     // in the general case, don't worry if 'generator' is a
257     // generator or not: since we are using safe primes,
258     // it will generate either an order-q or an order-2q group,
259     // which both is OK
260     if (!BN_set_word(t1, 2)) {
261       goto err;
262     }
263     if (!BN_set_word(t2, 1)) {
264       goto err;
265     }
266     g = generator;
267   }
268 
269   if (!BN_generate_prime_ex(dh->p, prime_bits, 1, t1, t2, cb)) {
270     goto err;
271   }
272   if (!BN_GENCB_call(cb, 3, 0)) {
273     goto err;
274   }
275   if (!BN_set_word(dh->g, g)) {
276     goto err;
277   }
278   ok = 1;
279 
280 err:
281   if (!ok) {
282     OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB);
283   }
284 
285   if (ctx != NULL) {
286     BN_CTX_end(ctx);
287     BN_CTX_free(ctx);
288   }
289   return ok;
290 }
291 
DH_generate_key(DH * dh)292 int DH_generate_key(DH *dh) {
293   int ok = 0;
294   int generate_new_key = 0;
295   BN_CTX *ctx = NULL;
296   BIGNUM *pub_key = NULL, *priv_key = NULL;
297 
298   if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
299     OPENSSL_PUT_ERROR(DH, DH_R_MODULUS_TOO_LARGE);
300     goto err;
301   }
302 
303   ctx = BN_CTX_new();
304   if (ctx == NULL) {
305     goto err;
306   }
307 
308   if (dh->priv_key == NULL) {
309     priv_key = BN_new();
310     if (priv_key == NULL) {
311       goto err;
312     }
313     generate_new_key = 1;
314   } else {
315     priv_key = dh->priv_key;
316   }
317 
318   if (dh->pub_key == NULL) {
319     pub_key = BN_new();
320     if (pub_key == NULL) {
321       goto err;
322     }
323   } else {
324     pub_key = dh->pub_key;
325   }
326 
327   if (!BN_MONT_CTX_set_locked(&dh->method_mont_p, &dh->method_mont_p_lock,
328                               dh->p, ctx)) {
329     goto err;
330   }
331 
332   if (generate_new_key) {
333     if (dh->q) {
334       if (!BN_rand_range_ex(priv_key, 2, dh->q)) {
335         goto err;
336       }
337     } else {
338       // secret exponent length
339       unsigned priv_bits = dh->priv_length;
340       if (priv_bits == 0) {
341         const unsigned p_bits = BN_num_bits(dh->p);
342         if (p_bits == 0) {
343           goto err;
344         }
345 
346         priv_bits = p_bits - 1;
347       }
348 
349       if (!BN_rand(priv_key, priv_bits, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY)) {
350         goto err;
351       }
352     }
353   }
354 
355   if (!BN_mod_exp_mont_consttime(pub_key, dh->g, priv_key, dh->p, ctx,
356                                  dh->method_mont_p)) {
357     goto err;
358   }
359 
360   dh->pub_key = pub_key;
361   dh->priv_key = priv_key;
362   ok = 1;
363 
364 err:
365   if (ok != 1) {
366     OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB);
367   }
368 
369   if (dh->pub_key == NULL) {
370     BN_free(pub_key);
371   }
372   if (dh->priv_key == NULL) {
373     BN_free(priv_key);
374   }
375   BN_CTX_free(ctx);
376   return ok;
377 }
378 
DH_compute_key(unsigned char * out,const BIGNUM * peers_key,DH * dh)379 int DH_compute_key(unsigned char *out, const BIGNUM *peers_key, DH *dh) {
380   BN_CTX *ctx = NULL;
381   BIGNUM *shared_key;
382   int ret = -1;
383   int check_result;
384 
385   if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
386     OPENSSL_PUT_ERROR(DH, DH_R_MODULUS_TOO_LARGE);
387     goto err;
388   }
389 
390   ctx = BN_CTX_new();
391   if (ctx == NULL) {
392     goto err;
393   }
394   BN_CTX_start(ctx);
395   shared_key = BN_CTX_get(ctx);
396   if (shared_key == NULL) {
397     goto err;
398   }
399 
400   if (dh->priv_key == NULL) {
401     OPENSSL_PUT_ERROR(DH, DH_R_NO_PRIVATE_VALUE);
402     goto err;
403   }
404 
405   if (!BN_MONT_CTX_set_locked(&dh->method_mont_p, &dh->method_mont_p_lock,
406                               dh->p, ctx)) {
407     goto err;
408   }
409 
410   if (!DH_check_pub_key(dh, peers_key, &check_result) || check_result) {
411     OPENSSL_PUT_ERROR(DH, DH_R_INVALID_PUBKEY);
412     goto err;
413   }
414 
415   if (!BN_mod_exp_mont_consttime(shared_key, peers_key, dh->priv_key, dh->p,
416                                  ctx, dh->method_mont_p)) {
417     OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB);
418     goto err;
419   }
420 
421   ret = BN_bn2bin(shared_key, out);
422 
423 err:
424   if (ctx != NULL) {
425     BN_CTX_end(ctx);
426     BN_CTX_free(ctx);
427   }
428 
429   return ret;
430 }
431 
DH_size(const DH * dh)432 int DH_size(const DH *dh) { return BN_num_bytes(dh->p); }
433 
DH_num_bits(const DH * dh)434 unsigned DH_num_bits(const DH *dh) { return BN_num_bits(dh->p); }
435 
DH_up_ref(DH * dh)436 int DH_up_ref(DH *dh) {
437   CRYPTO_refcount_inc(&dh->references);
438   return 1;
439 }
440 
int_dh_bn_cpy(BIGNUM ** dst,const BIGNUM * src)441 static int int_dh_bn_cpy(BIGNUM **dst, const BIGNUM *src) {
442   BIGNUM *a = NULL;
443 
444   if (src) {
445     a = BN_dup(src);
446     if (!a) {
447       return 0;
448     }
449   }
450 
451   BN_free(*dst);
452   *dst = a;
453   return 1;
454 }
455 
int_dh_param_copy(DH * to,const DH * from,int is_x942)456 static int int_dh_param_copy(DH *to, const DH *from, int is_x942) {
457   if (is_x942 == -1) {
458     is_x942 = !!from->q;
459   }
460   if (!int_dh_bn_cpy(&to->p, from->p) ||
461       !int_dh_bn_cpy(&to->g, from->g)) {
462     return 0;
463   }
464 
465   if (!is_x942) {
466     return 1;
467   }
468 
469   if (!int_dh_bn_cpy(&to->q, from->q) ||
470       !int_dh_bn_cpy(&to->j, from->j)) {
471     return 0;
472   }
473 
474   OPENSSL_free(to->seed);
475   to->seed = NULL;
476   to->seedlen = 0;
477 
478   if (from->seed) {
479     to->seed = BUF_memdup(from->seed, from->seedlen);
480     if (!to->seed) {
481       return 0;
482     }
483     to->seedlen = from->seedlen;
484   }
485 
486   return 1;
487 }
488 
DHparams_dup(const DH * dh)489 DH *DHparams_dup(const DH *dh) {
490   DH *ret = DH_new();
491   if (!ret) {
492     return NULL;
493   }
494 
495   if (!int_dh_param_copy(ret, dh, -1)) {
496     DH_free(ret);
497     return NULL;
498   }
499 
500   return ret;
501 }
502 
DH_get_ex_new_index(long argl,void * argp,CRYPTO_EX_unused * unused,CRYPTO_EX_dup * dup_unused,CRYPTO_EX_free * free_func)503 int DH_get_ex_new_index(long argl, void *argp, CRYPTO_EX_unused *unused,
504                         CRYPTO_EX_dup *dup_unused, CRYPTO_EX_free *free_func) {
505   int index;
506   if (!CRYPTO_get_ex_new_index(&g_ex_data_class, &index, argl, argp,
507                                free_func)) {
508     return -1;
509   }
510   return index;
511 }
512 
DH_set_ex_data(DH * d,int idx,void * arg)513 int DH_set_ex_data(DH *d, int idx, void *arg) {
514   return CRYPTO_set_ex_data(&d->ex_data, idx, arg);
515 }
516 
DH_get_ex_data(DH * d,int idx)517 void *DH_get_ex_data(DH *d, int idx) {
518   return CRYPTO_get_ex_data(&d->ex_data, idx);
519 }
520