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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 /* ====================================================================
58  * Copyright (c) 1998-2006 The OpenSSL Project.  All rights reserved.
59  *
60  * Redistribution and use in source and binary forms, with or without
61  * modification, are permitted provided that the following conditions
62  * are met:
63  *
64  * 1. Redistributions of source code must retain the above copyright
65  *    notice, this list of conditions and the following disclaimer.
66  *
67  * 2. Redistributions in binary form must reproduce the above copyright
68  *    notice, this list of conditions and the following disclaimer in
69  *    the documentation and/or other materials provided with the
70  *    distribution.
71  *
72  * 3. All advertising materials mentioning features or use of this
73  *    software must display the following acknowledgment:
74  *    "This product includes software developed by the OpenSSL Project
75  *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
76  *
77  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
78  *    endorse or promote products derived from this software without
79  *    prior written permission. For written permission, please contact
80  *    openssl-core@openssl.org.
81  *
82  * 5. Products derived from this software may not be called "OpenSSL"
83  *    nor may "OpenSSL" appear in their names without prior written
84  *    permission of the OpenSSL Project.
85  *
86  * 6. Redistributions of any form whatsoever must retain the following
87  *    acknowledgment:
88  *    "This product includes software developed by the OpenSSL Project
89  *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
90  *
91  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
92  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
93  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
94  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
95  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
96  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
97  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
98  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
99  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
100  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
101  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
102  * OF THE POSSIBILITY OF SUCH DAMAGE.
103  * ====================================================================
104  *
105  * This product includes cryptographic software written by Eric Young
106  * (eay@cryptsoft.com).  This product includes software written by Tim
107  * Hudson (tjh@cryptsoft.com). */
108 
109 #include <openssl/bn.h>
110 
111 #include <assert.h>
112 #include <stdio.h>
113 #include <stdlib.h>
114 #include <string.h>
115 
116 #include <openssl/err.h>
117 #include <openssl/mem.h>
118 #include <openssl/thread.h>
119 #include <openssl/type_check.h>
120 
121 #include "internal.h"
122 #include "../../internal.h"
123 
124 
BN_MONT_CTX_new(void)125 BN_MONT_CTX *BN_MONT_CTX_new(void) {
126   BN_MONT_CTX *ret = OPENSSL_malloc(sizeof(BN_MONT_CTX));
127 
128   if (ret == NULL) {
129     return NULL;
130   }
131 
132   OPENSSL_memset(ret, 0, sizeof(BN_MONT_CTX));
133   BN_init(&ret->RR);
134   BN_init(&ret->N);
135 
136   return ret;
137 }
138 
BN_MONT_CTX_free(BN_MONT_CTX * mont)139 void BN_MONT_CTX_free(BN_MONT_CTX *mont) {
140   if (mont == NULL) {
141     return;
142   }
143 
144   BN_free(&mont->RR);
145   BN_free(&mont->N);
146   OPENSSL_free(mont);
147 }
148 
BN_MONT_CTX_copy(BN_MONT_CTX * to,const BN_MONT_CTX * from)149 BN_MONT_CTX *BN_MONT_CTX_copy(BN_MONT_CTX *to, const BN_MONT_CTX *from) {
150   if (to == from) {
151     return to;
152   }
153 
154   if (!BN_copy(&to->RR, &from->RR) ||
155       !BN_copy(&to->N, &from->N)) {
156     return NULL;
157   }
158   to->n0[0] = from->n0[0];
159   to->n0[1] = from->n0[1];
160   return to;
161 }
162 
bn_mont_ctx_set_N_and_n0(BN_MONT_CTX * mont,const BIGNUM * mod)163 static int bn_mont_ctx_set_N_and_n0(BN_MONT_CTX *mont, const BIGNUM *mod) {
164   if (BN_is_zero(mod)) {
165     OPENSSL_PUT_ERROR(BN, BN_R_DIV_BY_ZERO);
166     return 0;
167   }
168   if (!BN_is_odd(mod)) {
169     OPENSSL_PUT_ERROR(BN, BN_R_CALLED_WITH_EVEN_MODULUS);
170     return 0;
171   }
172   if (BN_is_negative(mod)) {
173     OPENSSL_PUT_ERROR(BN, BN_R_NEGATIVE_NUMBER);
174     return 0;
175   }
176 
177   // Save the modulus.
178   if (!BN_copy(&mont->N, mod)) {
179     OPENSSL_PUT_ERROR(BN, ERR_R_INTERNAL_ERROR);
180     return 0;
181   }
182   // |mont->N| is always stored minimally. Computing RR efficiently leaks the
183   // size of the modulus. While the modulus may be private in RSA (one of the
184   // primes), their sizes are public, so this is fine.
185   bn_set_minimal_width(&mont->N);
186 
187   // Find n0 such that n0 * N == -1 (mod r).
188   //
189   // Only certain BN_BITS2<=32 platforms actually make use of n0[1]. For the
190   // others, we could use a shorter R value and use faster |BN_ULONG|-based
191   // math instead of |uint64_t|-based math, which would be double-precision.
192   // However, currently only the assembler files know which is which.
193   OPENSSL_STATIC_ASSERT(BN_MONT_CTX_N0_LIMBS == 1 || BN_MONT_CTX_N0_LIMBS == 2,
194                         "BN_MONT_CTX_N0_LIMBS value is invalid");
195   OPENSSL_STATIC_ASSERT(
196       sizeof(BN_ULONG) * BN_MONT_CTX_N0_LIMBS == sizeof(uint64_t),
197       "uint64_t is insufficient precision for n0");
198   uint64_t n0 = bn_mont_n0(&mont->N);
199   mont->n0[0] = (BN_ULONG)n0;
200 #if BN_MONT_CTX_N0_LIMBS == 2
201   mont->n0[1] = (BN_ULONG)(n0 >> BN_BITS2);
202 #else
203   mont->n0[1] = 0;
204 #endif
205   return 1;
206 }
207 
BN_MONT_CTX_set(BN_MONT_CTX * mont,const BIGNUM * mod,BN_CTX * ctx)208 int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod, BN_CTX *ctx) {
209   if (!bn_mont_ctx_set_N_and_n0(mont, mod)) {
210     return 0;
211   }
212 
213   BN_CTX *new_ctx = NULL;
214   if (ctx == NULL) {
215     new_ctx = BN_CTX_new();
216     if (new_ctx == NULL) {
217       return 0;
218     }
219     ctx = new_ctx;
220   }
221 
222   // Save RR = R**2 (mod N). R is the smallest power of 2**BN_BITS2 such that R
223   // > mod. Even though the assembly on some 32-bit platforms works with 64-bit
224   // values, using |BN_BITS2| here, rather than |BN_MONT_CTX_N0_LIMBS *
225   // BN_BITS2|, is correct because R**2 will still be a multiple of the latter
226   // as |BN_MONT_CTX_N0_LIMBS| is either one or two.
227   unsigned lgBigR = mont->N.width * BN_BITS2;
228   BN_zero(&mont->RR);
229   int ok = BN_set_bit(&mont->RR, lgBigR * 2) &&
230            BN_mod(&mont->RR, &mont->RR, &mont->N, ctx) &&
231            bn_resize_words(&mont->RR, mont->N.width);
232   BN_CTX_free(new_ctx);
233   return ok;
234 }
235 
BN_MONT_CTX_new_for_modulus(const BIGNUM * mod,BN_CTX * ctx)236 BN_MONT_CTX *BN_MONT_CTX_new_for_modulus(const BIGNUM *mod, BN_CTX *ctx) {
237   BN_MONT_CTX *mont = BN_MONT_CTX_new();
238   if (mont == NULL ||
239       !BN_MONT_CTX_set(mont, mod, ctx)) {
240     BN_MONT_CTX_free(mont);
241     return NULL;
242   }
243   return mont;
244 }
245 
BN_MONT_CTX_new_consttime(const BIGNUM * mod,BN_CTX * ctx)246 BN_MONT_CTX *BN_MONT_CTX_new_consttime(const BIGNUM *mod, BN_CTX *ctx) {
247   BN_MONT_CTX *mont = BN_MONT_CTX_new();
248   if (mont == NULL ||
249       !bn_mont_ctx_set_N_and_n0(mont, mod)) {
250     goto err;
251   }
252   unsigned lgBigR = mont->N.width * BN_BITS2;
253   if (!bn_mod_exp_base_2_consttime(&mont->RR, lgBigR * 2, &mont->N, ctx) ||
254       !bn_resize_words(&mont->RR, mont->N.width)) {
255     goto err;
256   }
257   return mont;
258 
259 err:
260   BN_MONT_CTX_free(mont);
261   return NULL;
262 }
263 
BN_MONT_CTX_set_locked(BN_MONT_CTX ** pmont,CRYPTO_MUTEX * lock,const BIGNUM * mod,BN_CTX * bn_ctx)264 int BN_MONT_CTX_set_locked(BN_MONT_CTX **pmont, CRYPTO_MUTEX *lock,
265                            const BIGNUM *mod, BN_CTX *bn_ctx) {
266   CRYPTO_MUTEX_lock_read(lock);
267   BN_MONT_CTX *ctx = *pmont;
268   CRYPTO_MUTEX_unlock_read(lock);
269 
270   if (ctx) {
271     return 1;
272   }
273 
274   CRYPTO_MUTEX_lock_write(lock);
275   if (*pmont == NULL) {
276     *pmont = BN_MONT_CTX_new_for_modulus(mod, bn_ctx);
277   }
278   const int ok = *pmont != NULL;
279   CRYPTO_MUTEX_unlock_write(lock);
280   return ok;
281 }
282 
BN_to_montgomery(BIGNUM * ret,const BIGNUM * a,const BN_MONT_CTX * mont,BN_CTX * ctx)283 int BN_to_montgomery(BIGNUM *ret, const BIGNUM *a, const BN_MONT_CTX *mont,
284                      BN_CTX *ctx) {
285   return BN_mod_mul_montgomery(ret, a, &mont->RR, mont, ctx);
286 }
287 
bn_from_montgomery_in_place(BN_ULONG * r,size_t num_r,BN_ULONG * a,size_t num_a,const BN_MONT_CTX * mont)288 static int bn_from_montgomery_in_place(BN_ULONG *r, size_t num_r, BN_ULONG *a,
289                                        size_t num_a, const BN_MONT_CTX *mont) {
290   const BN_ULONG *n = mont->N.d;
291   size_t num_n = mont->N.width;
292   if (num_r != num_n || num_a != 2 * num_n) {
293     OPENSSL_PUT_ERROR(BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
294     return 0;
295   }
296 
297   // Add multiples of |n| to |r| until R = 2^(nl * BN_BITS2) divides it. On
298   // input, we had |r| < |n| * R, so now |r| < 2 * |n| * R. Note that |r|
299   // includes |carry| which is stored separately.
300   BN_ULONG n0 = mont->n0[0];
301   BN_ULONG carry = 0;
302   for (size_t i = 0; i < num_n; i++) {
303     BN_ULONG v = bn_mul_add_words(a + i, n, num_n, a[i] * n0);
304     v += carry + a[i + num_n];
305     carry |= (v != a[i + num_n]);
306     carry &= (v <= a[i + num_n]);
307     a[i + num_n] = v;
308   }
309 
310   // Shift |num_n| words to divide by R. We have |a| < 2 * |n|. Note that |a|
311   // includes |carry| which is stored separately.
312   a += num_n;
313 
314   // |a| thus requires at most one additional subtraction |n| to be reduced.
315   bn_reduce_once(r, a, carry, n, num_n);
316   return 1;
317 }
318 
BN_from_montgomery_word(BIGNUM * ret,BIGNUM * r,const BN_MONT_CTX * mont)319 static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r,
320                                    const BN_MONT_CTX *mont) {
321   if (r->neg) {
322     OPENSSL_PUT_ERROR(BN, BN_R_NEGATIVE_NUMBER);
323     return 0;
324   }
325 
326   const BIGNUM *n = &mont->N;
327   if (n->width == 0) {
328     ret->width = 0;
329     return 1;
330   }
331 
332   int max = 2 * n->width;  // carry is stored separately
333   if (!bn_resize_words(r, max) ||
334       !bn_wexpand(ret, n->width)) {
335     return 0;
336   }
337 
338   ret->width = n->width;
339   ret->neg = 0;
340   return bn_from_montgomery_in_place(ret->d, ret->width, r->d, r->width, mont);
341 }
342 
BN_from_montgomery(BIGNUM * r,const BIGNUM * a,const BN_MONT_CTX * mont,BN_CTX * ctx)343 int BN_from_montgomery(BIGNUM *r, const BIGNUM *a, const BN_MONT_CTX *mont,
344                        BN_CTX *ctx) {
345   int ret = 0;
346   BIGNUM *t;
347 
348   BN_CTX_start(ctx);
349   t = BN_CTX_get(ctx);
350   if (t == NULL ||
351       !BN_copy(t, a)) {
352     goto err;
353   }
354 
355   ret = BN_from_montgomery_word(r, t, mont);
356 
357 err:
358   BN_CTX_end(ctx);
359 
360   return ret;
361 }
362 
bn_one_to_montgomery(BIGNUM * r,const BN_MONT_CTX * mont,BN_CTX * ctx)363 int bn_one_to_montgomery(BIGNUM *r, const BN_MONT_CTX *mont, BN_CTX *ctx) {
364   // If the high bit of |n| is set, R = 2^(width*BN_BITS2) < 2 * |n|, so we
365   // compute R - |n| rather than perform Montgomery reduction.
366   const BIGNUM *n = &mont->N;
367   if (n->width > 0 && (n->d[n->width - 1] >> (BN_BITS2 - 1)) != 0) {
368     if (!bn_wexpand(r, n->width)) {
369       return 0;
370     }
371     r->d[0] = 0 - n->d[0];
372     for (int i = 1; i < n->width; i++) {
373       r->d[i] = ~n->d[i];
374     }
375     r->width = n->width;
376     r->neg = 0;
377     return 1;
378   }
379 
380   return BN_from_montgomery(r, &mont->RR, mont, ctx);
381 }
382 
bn_mod_mul_montgomery_fallback(BIGNUM * r,const BIGNUM * a,const BIGNUM * b,const BN_MONT_CTX * mont,BN_CTX * ctx)383 static int bn_mod_mul_montgomery_fallback(BIGNUM *r, const BIGNUM *a,
384                                           const BIGNUM *b,
385                                           const BN_MONT_CTX *mont,
386                                           BN_CTX *ctx) {
387   int ret = 0;
388 
389   BN_CTX_start(ctx);
390   BIGNUM *tmp = BN_CTX_get(ctx);
391   if (tmp == NULL) {
392     goto err;
393   }
394 
395   if (a == b) {
396     if (!bn_sqr_consttime(tmp, a, ctx)) {
397       goto err;
398     }
399   } else {
400     if (!bn_mul_consttime(tmp, a, b, ctx)) {
401       goto err;
402     }
403   }
404 
405   // reduce from aRR to aR
406   if (!BN_from_montgomery_word(r, tmp, mont)) {
407     goto err;
408   }
409 
410   ret = 1;
411 
412 err:
413   BN_CTX_end(ctx);
414   return ret;
415 }
416 
BN_mod_mul_montgomery(BIGNUM * r,const BIGNUM * a,const BIGNUM * b,const BN_MONT_CTX * mont,BN_CTX * ctx)417 int BN_mod_mul_montgomery(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
418                           const BN_MONT_CTX *mont, BN_CTX *ctx) {
419   if (a->neg || b->neg) {
420     OPENSSL_PUT_ERROR(BN, BN_R_NEGATIVE_NUMBER);
421     return 0;
422   }
423 
424 #if defined(OPENSSL_BN_ASM_MONT)
425   // |bn_mul_mont| requires at least 128 bits of limbs, at least for x86.
426   int num = mont->N.width;
427   if (num >= (128 / BN_BITS2) &&
428       a->width == num &&
429       b->width == num) {
430     if (!bn_wexpand(r, num)) {
431       return 0;
432     }
433     if (!bn_mul_mont(r->d, a->d, b->d, mont->N.d, mont->n0, num)) {
434       // The check above ensures this won't happen.
435       assert(0);
436       OPENSSL_PUT_ERROR(BN, ERR_R_INTERNAL_ERROR);
437       return 0;
438     }
439     r->neg = 0;
440     r->width = num;
441     return 1;
442   }
443 #endif
444 
445   return bn_mod_mul_montgomery_fallback(r, a, b, mont, ctx);
446 }
447 
bn_less_than_montgomery_R(const BIGNUM * bn,const BN_MONT_CTX * mont)448 int bn_less_than_montgomery_R(const BIGNUM *bn, const BN_MONT_CTX *mont) {
449   return !BN_is_negative(bn) &&
450          bn_fits_in_words(bn, mont->N.width);
451 }
452 
bn_to_montgomery_small(BN_ULONG * r,const BN_ULONG * a,size_t num,const BN_MONT_CTX * mont)453 void bn_to_montgomery_small(BN_ULONG *r, const BN_ULONG *a, size_t num,
454                             const BN_MONT_CTX *mont) {
455   bn_mod_mul_montgomery_small(r, a, mont->RR.d, num, mont);
456 }
457 
bn_from_montgomery_small(BN_ULONG * r,const BN_ULONG * a,size_t num,const BN_MONT_CTX * mont)458 void bn_from_montgomery_small(BN_ULONG *r, const BN_ULONG *a, size_t num,
459                               const BN_MONT_CTX *mont) {
460   if (num != (size_t)mont->N.width || num > BN_SMALL_MAX_WORDS) {
461     abort();
462   }
463   BN_ULONG tmp[BN_SMALL_MAX_WORDS * 2];
464   OPENSSL_memcpy(tmp, a, num * sizeof(BN_ULONG));
465   OPENSSL_memset(tmp + num, 0, num * sizeof(BN_ULONG));
466   if (!bn_from_montgomery_in_place(r, num, tmp, 2 * num, mont)) {
467     abort();
468   }
469   OPENSSL_cleanse(tmp, 2 * num * sizeof(BN_ULONG));
470 }
471 
bn_mod_mul_montgomery_small(BN_ULONG * r,const BN_ULONG * a,const BN_ULONG * b,size_t num,const BN_MONT_CTX * mont)472 void bn_mod_mul_montgomery_small(BN_ULONG *r, const BN_ULONG *a,
473                                  const BN_ULONG *b, size_t num,
474                                  const BN_MONT_CTX *mont) {
475   if (num != (size_t)mont->N.width || num > BN_SMALL_MAX_WORDS) {
476     abort();
477   }
478 
479 #if defined(OPENSSL_BN_ASM_MONT)
480   // |bn_mul_mont| requires at least 128 bits of limbs, at least for x86.
481   if (num >= (128 / BN_BITS2)) {
482     if (!bn_mul_mont(r, a, b, mont->N.d, mont->n0, num)) {
483       abort();  // The check above ensures this won't happen.
484     }
485     return;
486   }
487 #endif
488 
489   // Compute the product.
490   BN_ULONG tmp[2 * BN_SMALL_MAX_WORDS];
491   if (a == b) {
492     bn_sqr_small(tmp, 2 * num, a, num);
493   } else {
494     bn_mul_small(tmp, 2 * num, a, num, b, num);
495   }
496 
497   // Reduce.
498   if (!bn_from_montgomery_in_place(r, num, tmp, 2 * num, mont)) {
499     abort();
500   }
501   OPENSSL_cleanse(tmp, 2 * num * sizeof(BN_ULONG));
502 }
503