Bug Summary

File:src/lib/libcrypto/bn/bn_exp.c
Warning:line 1064, column 3
Value stored to 'j' is never read

Annotated Source Code

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clang -cc1 -cc1 -triple amd64-unknown-openbsd7.4 -analyze -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name bn_exp.c -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -mrelocation-model pic -pic-level 1 -pic-is-pie -mframe-pointer=all -relaxed-aliasing -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -target-feature +retpoline-indirect-calls -target-feature +retpoline-indirect-branches -tune-cpu generic -debugger-tuning=gdb -fcoverage-compilation-dir=/usr/src/lib/libcrypto/obj -resource-dir /usr/local/llvm16/lib/clang/16 -D LIBRESSL_INTERNAL -D HAVE_FUNOPEN -I /usr/src/lib/libcrypto -I /usr/src/lib/libcrypto/arch/amd64 -I /usr/src/lib/libcrypto/asn1 -I /usr/src/lib/libcrypto/bio -I /usr/src/lib/libcrypto/bn -I /usr/src/lib/libcrypto/bn/arch/amd64 -I /usr/src/lib/libcrypto/bytestring -I /usr/src/lib/libcrypto/curve25519 -I /usr/src/lib/libcrypto/dh -I /usr/src/lib/libcrypto/dsa -I /usr/src/lib/libcrypto/ec -I /usr/src/lib/libcrypto/ecdsa -I /usr/src/lib/libcrypto/evp -I /usr/src/lib/libcrypto/hidden -I /usr/src/lib/libcrypto/hmac -I /usr/src/lib/libcrypto/kdf -I /usr/src/lib/libcrypto/modes -I /usr/src/lib/libcrypto/ocsp -I /usr/src/lib/libcrypto/pkcs12 -I /usr/src/lib/libcrypto/rsa -I /usr/src/lib/libcrypto/sha -I /usr/src/lib/libcrypto/ts -I /usr/src/lib/libcrypto/x509 -I /usr/src/lib/libcrypto/obj -D AES_ASM -D BSAES_ASM -D VPAES_ASM -D OPENSSL_IA32_SSE2 -D RSA_ASM -D OPENSSL_BN_ASM_MONT -D OPENSSL_BN_ASM_MONT5 -D MD5_ASM -D GHASH_ASM -D RC4_MD5_ASM -D SHA1_ASM -D SHA256_ASM -D SHA512_ASM -D WHIRLPOOL_ASM -D OPENSSL_CPUID_OBJ -internal-isystem /usr/local/llvm16/lib/clang/16/include -internal-externc-isystem /usr/include -O2 -fdebug-compilation-dir=/usr/src/lib/libcrypto/obj -ferror-limit 19 -fwrapv -D_RET_PROTECTOR -ret-protector -fcf-protection=branch -fno-jump-tables -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -fno-builtin-malloc -fno-builtin-calloc -fno-builtin-realloc -fno-builtin-valloc -fno-builtin-free -fno-builtin-strdup -fno-builtin-strndup -analyzer-output=html -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /home/ben/Projects/scan/2024-01-11-140451-98009-1 -x c /usr/src/lib/libcrypto/bn/bn_exp.c
1/* $OpenBSD: bn_exp.c,v 1.50 2023/10/19 10:27:27 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 * Copyright (c) 1998-2005 The OpenSSL Project. All rights reserved.
60 *
61 * Redistribution and use in source and binary forms, with or without
62 * modification, are permitted provided that the following conditions
63 * are met:
64 *
65 * 1. Redistributions of source code must retain the above copyright
66 * notice, this list of conditions and the following disclaimer.
67 *
68 * 2. Redistributions in binary form must reproduce the above copyright
69 * notice, this list of conditions and the following disclaimer in
70 * the documentation and/or other materials provided with the
71 * distribution.
72 *
73 * 3. All advertising materials mentioning features or use of this
74 * software must display the following acknowledgment:
75 * "This product includes software developed by the OpenSSL Project
76 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
77 *
78 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
79 * endorse or promote products derived from this software without
80 * prior written permission. For written permission, please contact
81 * openssl-core@openssl.org.
82 *
83 * 5. Products derived from this software may not be called "OpenSSL"
84 * nor may "OpenSSL" appear in their names without prior written
85 * permission of the OpenSSL Project.
86 *
87 * 6. Redistributions of any form whatsoever must retain the following
88 * acknowledgment:
89 * "This product includes software developed by the OpenSSL Project
90 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
91 *
92 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
93 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
94 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
95 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
96 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
97 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
98 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
99 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
100 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
101 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
102 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
103 * OF THE POSSIBILITY OF SUCH DAMAGE.
104 * ====================================================================
105 *
106 * This product includes cryptographic software written by Eric Young
107 * (eay@cryptsoft.com). This product includes software written by Tim
108 * Hudson (tjh@cryptsoft.com).
109 *
110 */
111
112#include <stdlib.h>
113#include <string.h>
114
115#include <openssl/err.h>
116
117#include "bn_local.h"
118#include "constant_time.h"
119
120/* maximum precomputation table size for *variable* sliding windows */
121#define TABLE_SIZE32 32
122
123/* Calculates r = a^p by successive squaring of a. Not constant time. */
124int
125BN_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
126{
127 BIGNUM *rr, *v;
128 int i;
129 int ret = 0;
130
131 if (BN_get_flags(p, BN_FLG_CONSTTIME0x04) != 0) {
132 BNerror(ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED)ERR_put_error(3,(0xfff),((2|64)),"/usr/src/lib/libcrypto/bn/bn_exp.c"
,132);
133 return -1;
134 }
135
136 BN_CTX_start(ctx);
137
138 if ((v = BN_CTX_get(ctx)) == NULL((void *)0))
139 goto err;
140
141 rr = r;
142 if (r == a || r == p)
143 rr = BN_CTX_get(ctx);
144 if (rr == NULL((void *)0))
145 goto err;
146
147 if (!BN_one(rr))
148 goto err;
149 if (BN_is_odd(p)) {
150 if (!bn_copy(rr, a))
151 goto err;
152 }
153
154 if (!bn_copy(v, a))
155 goto err;
156
157 for (i = 1; i < BN_num_bits(p); i++) {
158 if (!BN_sqr(v, v, ctx))
159 goto err;
160 if (!BN_is_bit_set(p, i))
161 continue;
162 if (!BN_mul(rr, rr, v, ctx))
163 goto err;
164 }
165
166 if (!bn_copy(r, rr))
167 goto err;
168
169 ret = 1;
170
171 err:
172 BN_CTX_end(ctx);
173
174 return ret;
175}
176LCRYPTO_ALIAS(BN_exp)asm("");
177
178/* The old fallback, simple version :-) */
179int
180BN_mod_exp_simple(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
181 BN_CTX *ctx)
182{
183 int i, j, bits, wstart, wend, window, wvalue;
184 int start = 1;
185 BIGNUM *d, *q;
186 /* Table of variables obtained from 'ctx' */
187 BIGNUM *val[TABLE_SIZE32];
188 int ret = 0;
189
190 if (BN_get_flags(p, BN_FLG_CONSTTIME0x04) != 0) {
191 /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
192 BNerror(ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED)ERR_put_error(3,(0xfff),((2|64)),"/usr/src/lib/libcrypto/bn/bn_exp.c"
,192);
193 return -1;
194 }
195
196 if (r == m) {
197 BNerror(BN_R_INVALID_ARGUMENT)ERR_put_error(3,(0xfff),(118),"/usr/src/lib/libcrypto/bn/bn_exp.c"
,197);
198 return 0;
199 }
200
201 bits = BN_num_bits(p);
202 if (bits == 0) {
203 /* x**0 mod 1 is still zero. */
204 if (BN_abs_is_word(m, 1)) {
205 ret = 1;
206 BN_zero(r);
207 } else
208 ret = BN_one(r);
209 return ret;
210 }
211
212 BN_CTX_start(ctx);
213 if ((d = BN_CTX_get(ctx)) == NULL((void *)0))
214 goto err;
215 if ((q = BN_CTX_get(ctx)) == NULL((void *)0))
216 goto err;
217 if ((val[0] = BN_CTX_get(ctx)) == NULL((void *)0))
218 goto err;
219
220 if (!BN_nnmod(val[0], a, m, ctx))
221 goto err;
222 if (BN_is_zero(val[0])) {
223 BN_zero(r);
224 goto done;
225 }
226 if (!bn_copy(q, p))
227 goto err;
228
229 window = BN_window_bits_for_exponent_size(bits)((bits) > 671 ? 6 : (bits) > 239 ? 5 : (bits) > 79 ?
4 : (bits) > 23 ? 3 : 1);
230 if (window > 1) {
231 if (!BN_mod_mul(d, val[0], val[0], m, ctx))
232 goto err;
233 j = 1 << (window - 1);
234 for (i = 1; i < j; i++) {
235 if (((val[i] = BN_CTX_get(ctx)) == NULL((void *)0)) ||
236 !BN_mod_mul(val[i], val[i - 1], d,m, ctx))
237 goto err;
238 }
239 }
240
241 start = 1; /* This is used to avoid multiplication etc
242 * when there is only the value '1' in the
243 * buffer. */
244 wvalue = 0; /* The 'value' of the window */
245 wstart = bits - 1; /* The top bit of the window */
246 wend = 0; /* The bottom bit of the window */
247
248 if (!BN_one(r))
249 goto err;
250
251 for (;;) {
252 if (BN_is_bit_set(q, wstart) == 0) {
253 if (!start)
254 if (!BN_mod_mul(r, r, r, m, ctx))
255 goto err;
256 if (wstart == 0)
257 break;
258 wstart--;
259 continue;
260 }
261 /* We now have wstart on a 'set' bit, we now need to work out
262 * how bit a window to do. To do this we need to scan
263 * forward until the last set bit before the end of the
264 * window */
265 j = wstart;
266 wvalue = 1;
267 wend = 0;
268 for (i = 1; i < window; i++) {
269 if (wstart - i < 0)
270 break;
271 if (BN_is_bit_set(q, wstart - i)) {
272 wvalue <<= (i - wend);
273 wvalue |= 1;
274 wend = i;
275 }
276 }
277
278 /* wend is the size of the current window */
279 j = wend + 1;
280 /* add the 'bytes above' */
281 if (!start)
282 for (i = 0; i < j; i++) {
283 if (!BN_mod_mul(r, r, r, m, ctx))
284 goto err;
285 }
286
287 /* wvalue will be an odd number < 2^window */
288 if (!BN_mod_mul(r, r, val[wvalue >> 1], m, ctx))
289 goto err;
290
291 /* move the 'window' down further */
292 wstart -= wend + 1;
293 wvalue = 0;
294 start = 0;
295 if (wstart < 0)
296 break;
297 }
298
299 done:
300 ret = 1;
301
302 err:
303 BN_CTX_end(ctx);
304
305 return ret;
306}
307LCRYPTO_ALIAS(BN_mod_exp_simple)asm("");
308
309/* BN_mod_exp_mont_consttime() stores the precomputed powers in a specific layout
310 * so that accessing any of these table values shows the same access pattern as far
311 * as cache lines are concerned. The following functions are used to transfer a BIGNUM
312 * from/to that table. */
313
314static int
315MOD_EXP_CTIME_COPY_TO_PREBUF(const BIGNUM *b, int top, unsigned char *buf,
316 int idx, int window)
317{
318 int i, j;
319 int width = 1 << window;
320 BN_ULONGunsigned long *table = (BN_ULONGunsigned long *)buf;
321
322 if (top > b->top)
323 top = b->top; /* this works because 'buf' is explicitly zeroed */
324
325 for (i = 0, j = idx; i < top; i++, j += width) {
326 table[j] = b->d[i];
327 }
328
329 return 1;
330}
331
332static int
333MOD_EXP_CTIME_COPY_FROM_PREBUF(BIGNUM *b, int top, unsigned char *buf, int idx,
334 int window)
335{
336 int i, j;
337 int width = 1 << window;
338 volatile BN_ULONGunsigned long *table = (volatile BN_ULONGunsigned long *)buf;
339
340 if (!bn_wexpand(b, top))
341 return 0;
342
343 if (window <= 3) {
344 for (i = 0; i < top; i++, table += width) {
345 BN_ULONGunsigned long acc = 0;
346
347 for (j = 0; j < width; j++) {
348 acc |= table[j] &
349 ((BN_ULONGunsigned long)0 - (constant_time_eq_int(j,idx)&1));
350 }
351
352 b->d[i] = acc;
353 }
354 } else {
355 int xstride = 1 << (window - 2);
356 BN_ULONGunsigned long y0, y1, y2, y3;
357
358 i = idx >> (window - 2); /* equivalent of idx / xstride */
359 idx &= xstride - 1; /* equivalent of idx % xstride */
360
361 y0 = (BN_ULONGunsigned long)0 - (constant_time_eq_int(i,0)&1);
362 y1 = (BN_ULONGunsigned long)0 - (constant_time_eq_int(i,1)&1);
363 y2 = (BN_ULONGunsigned long)0 - (constant_time_eq_int(i,2)&1);
364 y3 = (BN_ULONGunsigned long)0 - (constant_time_eq_int(i,3)&1);
365
366 for (i = 0; i < top; i++, table += width) {
367 BN_ULONGunsigned long acc = 0;
368
369 for (j = 0; j < xstride; j++) {
370 acc |= ( (table[j + 0 * xstride] & y0) |
371 (table[j + 1 * xstride] & y1) |
372 (table[j + 2 * xstride] & y2) |
373 (table[j + 3 * xstride] & y3) )
374 & ((BN_ULONGunsigned long)0 - (constant_time_eq_int(j,idx)&1));
375 }
376
377 b->d[i] = acc;
378 }
379 }
380 b->top = top;
381 bn_correct_top(b);
382 return 1;
383}
384
385/* Given a pointer value, compute the next address that is a cache line multiple. */
386#define MOD_EXP_CTIME_ALIGN(x_)((unsigned char*)(x_) + (( 64 ) - (((size_t)(x_)) & ((( 64
) - 1))))) \
387 ((unsigned char*)(x_) + (MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH( 64 ) - (((size_t)(x_)) & (MOD_EXP_CTIME_MIN_CACHE_LINE_MASK(( 64 ) - 1)))))
388
389/* This variant of BN_mod_exp_mont() uses fixed windows and the special
390 * precomputation memory layout to limit data-dependency to a minimum
391 * to protect secret exponents (cf. the hyper-threading timing attacks
392 * pointed out by Colin Percival,
393 * http://www.daemonology.net/hyperthreading-considered-harmful/)
394 */
395int
396BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
397 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont)
398{
399 int i, bits, ret = 0, window, wvalue;
400 int top;
401 BN_MONT_CTX *mont = NULL((void *)0);
402 int numPowers;
403 unsigned char *powerbufFree = NULL((void *)0);
404 int powerbufLen = 0;
405 unsigned char *powerbuf = NULL((void *)0);
406 BIGNUM tmp, am;
407
408
409 if (!BN_is_odd(m)) {
410 BNerror(BN_R_CALLED_WITH_EVEN_MODULUS)ERR_put_error(3,(0xfff),(102),"/usr/src/lib/libcrypto/bn/bn_exp.c"
,410);
411 return (0);
412 }
413
414 top = m->top;
415
416 bits = BN_num_bits(p);
417 if (bits == 0) {
418 /* x**0 mod 1 is still zero. */
419 if (BN_abs_is_word(m, 1)) {
420 ret = 1;
421 BN_zero(rr);
422 } else
423 ret = BN_one(rr);
424 return ret;
425 }
426
427 BN_CTX_start(ctx);
428
429 /*
430 * Allocate a Montgomery context if it was not supplied by the caller.
431 * If this is not done, things will break in the montgomery part.
432 */
433 if (in_mont != NULL((void *)0))
434 mont = in_mont;
435 else {
436 if ((mont = BN_MONT_CTX_new()) == NULL((void *)0))
437 goto err;
438 if (!BN_MONT_CTX_set(mont, m, ctx))
439 goto err;
440 }
441
442 /* Get the window size to use with size of p. */
443 window = BN_window_bits_for_ctime_exponent_size(bits)((bits) > 937 ? 6 : (bits) > 306 ? 5 : (bits) > 89 ?
4 : (bits) > 22 ? 3 : 1);
444#if defined(OPENSSL_BN_ASM_MONT51)
445 if (window == 6 && bits <= 1024)
446 window = 5; /* ~5% improvement of 2048-bit RSA sign */
447#endif
448
449 /* Allocate a buffer large enough to hold all of the pre-computed
450 * powers of am, am itself and tmp.
451 */
452 numPowers = 1 << window;
453 powerbufLen = sizeof(m->d[0]) * (top * numPowers +
454 ((2*top) > numPowers ? (2*top) : numPowers));
455 if ((powerbufFree = calloc(powerbufLen +
456 MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH( 64 ), 1)) == NULL((void *)0))
457 goto err;
458 powerbuf = MOD_EXP_CTIME_ALIGN(powerbufFree)((unsigned char*)(powerbufFree) + (( 64 ) - (((size_t)(powerbufFree
)) & ((( 64 ) - 1)))));
459
460 /* lay down tmp and am right after powers table */
461 tmp.d = (BN_ULONGunsigned long *)(powerbuf + sizeof(m->d[0]) * top * numPowers);
462 am.d = tmp.d + top;
463 tmp.top = am.top = 0;
464 tmp.dmax = am.dmax = top;
465 tmp.neg = am.neg = 0;
466 tmp.flags = am.flags = BN_FLG_STATIC_DATA0x02;
467
468 /* prepare a^0 in Montgomery domain */
469#if 1
470 if (!BN_to_montgomery(&tmp, BN_value_one(), mont, ctx))
471 goto err;
472#else
473 tmp.d[0] = (0 - m - >d[0]) & BN_MASK2(0xffffffffffffffffL); /* 2^(top*BN_BITS2) - m */
474 for (i = 1; i < top; i++)
475 tmp.d[i] = (~m->d[i]) & BN_MASK2(0xffffffffffffffffL);
476 tmp.top = top;
477#endif
478
479 /* prepare a^1 in Montgomery domain */
480 if (!BN_nnmod(&am, a, m, ctx))
481 goto err;
482 if (!BN_to_montgomery(&am, &am, mont, ctx))
483 goto err;
484
485#if defined(OPENSSL_BN_ASM_MONT51)
486 /* This optimization uses ideas from http://eprint.iacr.org/2011/239,
487 * specifically optimization of cache-timing attack countermeasures
488 * and pre-computation optimization. */
489
490 /* Dedicated window==4 case improves 512-bit RSA sign by ~15%, but as
491 * 512-bit RSA is hardly relevant, we omit it to spare size... */
492 if (window == 5 && top > 1) {
493 void bn_mul_mont_gather5(BN_ULONGunsigned long *rp, const BN_ULONGunsigned long *ap,
494 const void *table, const BN_ULONGunsigned long *np,
495 const BN_ULONGunsigned long *n0, int num, int power);
496 void bn_scatter5(const BN_ULONGunsigned long *inp, size_t num,
497 void *table, size_t power);
498 void bn_gather5(BN_ULONGunsigned long *out, size_t num,
499 void *table, size_t power);
500
501 BN_ULONGunsigned long *np = mont->N.d, *n0 = mont->n0;
502
503 /* BN_to_montgomery can contaminate words above .top
504 * [in BN_DEBUG[_DEBUG] build]... */
505 for (i = am.top; i < top; i++)
506 am.d[i] = 0;
507 for (i = tmp.top; i < top; i++)
508 tmp.d[i] = 0;
509
510 bn_scatter5(tmp.d, top, powerbuf, 0);
511 bn_scatter5(am.d, am.top, powerbuf, 1);
512 bn_mul_mont(tmp.d, am.d, am.d, np, n0, top);
513 bn_scatter5(tmp.d, top, powerbuf, 2);
514
515#if 0
516 for (i = 3; i < 32; i++) {
517 /* Calculate a^i = a^(i-1) * a */
518 bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np,
519 n0, top, i - 1);
520 bn_scatter5(tmp.d, top, powerbuf, i);
521 }
522#else
523 /* same as above, but uses squaring for 1/2 of operations */
524 for (i = 4; i < 32; i*=2) {
525 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
526 bn_scatter5(tmp.d, top, powerbuf, i);
527 }
528 for (i = 3; i < 8; i += 2) {
529 int j;
530 bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np,
531 n0, top, i - 1);
532 bn_scatter5(tmp.d, top, powerbuf, i);
533 for (j = 2 * i; j < 32; j *= 2) {
534 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
535 bn_scatter5(tmp.d, top, powerbuf, j);
536 }
537 }
538 for (; i < 16; i += 2) {
539 bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np,
540 n0, top, i - 1);
541 bn_scatter5(tmp.d, top, powerbuf, i);
542 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
543 bn_scatter5(tmp.d, top, powerbuf, 2*i);
544 }
545 for (; i < 32; i += 2) {
546 bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np,
547 n0, top, i - 1);
548 bn_scatter5(tmp.d, top, powerbuf, i);
549 }
550#endif
551 bits--;
552 for (wvalue = 0, i = bits % 5; i >= 0; i--, bits--)
553 wvalue = (wvalue << 1) + BN_is_bit_set(p, bits);
554 bn_gather5(tmp.d, top, powerbuf, wvalue);
555
556 /* Scan the exponent one window at a time starting from the most
557 * significant bits.
558 */
559 while (bits >= 0) {
560 for (wvalue = 0, i = 0; i < 5; i++, bits--)
561 wvalue = (wvalue << 1) + BN_is_bit_set(p, bits);
562
563 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
564 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
565 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
566 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
567 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
568 bn_mul_mont_gather5(tmp.d, tmp.d, powerbuf, np, n0, top, wvalue);
569 }
570
571 tmp.top = top;
572 bn_correct_top(&tmp);
573 } else
574#endif
575 {
576 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 0,
577 window))
578 goto err;
579 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&am, top, powerbuf, 1,
580 window))
581 goto err;
582
583 /* If the window size is greater than 1, then calculate
584 * val[i=2..2^winsize-1]. Powers are computed as a*a^(i-1)
585 * (even powers could instead be computed as (a^(i/2))^2
586 * to use the slight performance advantage of sqr over mul).
587 */
588 if (window > 1) {
589 if (!BN_mod_mul_montgomery(&tmp, &am, &am, mont, ctx))
590 goto err;
591 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf,
592 2, window))
593 goto err;
594 for (i = 3; i < numPowers; i++) {
595 /* Calculate a^i = a^(i-1) * a */
596 if (!BN_mod_mul_montgomery(&tmp, &am, &tmp,
597 mont, ctx))
598 goto err;
599 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top,
600 powerbuf, i, window))
601 goto err;
602 }
603 }
604
605 bits--;
606 for (wvalue = 0, i = bits % window; i >= 0; i--, bits--)
607 wvalue = (wvalue << 1) + BN_is_bit_set(p, bits);
608 if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&tmp, top, powerbuf,
609 wvalue, window))
610 goto err;
611
612 /* Scan the exponent one window at a time starting from the most
613 * significant bits.
614 */
615 while (bits >= 0) {
616 wvalue = 0; /* The 'value' of the window */
617
618 /* Scan the window, squaring the result as we go */
619 for (i = 0; i < window; i++, bits--) {
620 if (!BN_mod_mul_montgomery(&tmp, &tmp, &tmp,
621 mont, ctx))
622 goto err;
623 wvalue = (wvalue << 1) + BN_is_bit_set(p, bits);
624 }
625
626 /* Fetch the appropriate pre-computed value from the pre-buf */
627 if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&am, top, powerbuf,
628 wvalue, window))
629 goto err;
630
631 /* Multiply the result into the intermediate result */
632 if (!BN_mod_mul_montgomery(&tmp, &tmp, &am, mont, ctx))
633 goto err;
634 }
635 }
636
637 /* Convert the final result from montgomery to standard format */
638 if (!BN_from_montgomery(rr, &tmp, mont, ctx))
639 goto err;
640 ret = 1;
641
642err:
643 if ((in_mont == NULL((void *)0)) && (mont != NULL((void *)0)))
644 BN_MONT_CTX_free(mont);
645 freezero(powerbufFree, powerbufLen + MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH( 64 ));
646 BN_CTX_end(ctx);
647 return (ret);
648}
649LCRYPTO_ALIAS(BN_mod_exp_mont_consttime)asm("");
650
651static int
652BN_mod_exp_mont_internal(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
653 BN_CTX *ctx, BN_MONT_CTX *in_mont, int ct)
654{
655 int i, j, bits, ret = 0, wstart, wend, window, wvalue;
656 int start = 1;
657 BIGNUM *d, *r;
658 const BIGNUM *aa;
659 /* Table of variables obtained from 'ctx' */
660 BIGNUM *val[TABLE_SIZE32];
661 BN_MONT_CTX *mont = NULL((void *)0);
662
663 if (ct) {
664 return BN_mod_exp_mont_consttime(rr, a, p, m, ctx, in_mont);
665 }
666
667
668 if (!BN_is_odd(m)) {
669 BNerror(BN_R_CALLED_WITH_EVEN_MODULUS)ERR_put_error(3,(0xfff),(102),"/usr/src/lib/libcrypto/bn/bn_exp.c"
,669);
670 return (0);
671 }
672
673 bits = BN_num_bits(p);
674 if (bits == 0) {
675 /* x**0 mod 1 is still zero. */
676 if (BN_abs_is_word(m, 1)) {
677 ret = 1;
678 BN_zero(rr);
679 } else
680 ret = BN_one(rr);
681 return ret;
682 }
683
684 BN_CTX_start(ctx);
685 if ((d = BN_CTX_get(ctx)) == NULL((void *)0))
686 goto err;
687 if ((r = BN_CTX_get(ctx)) == NULL((void *)0))
688 goto err;
689 if ((val[0] = BN_CTX_get(ctx)) == NULL((void *)0))
690 goto err;
691
692 /* If this is not done, things will break in the montgomery
693 * part */
694
695 if (in_mont != NULL((void *)0))
696 mont = in_mont;
697 else {
698 if ((mont = BN_MONT_CTX_new()) == NULL((void *)0))
699 goto err;
700 if (!BN_MONT_CTX_set(mont, m, ctx))
701 goto err;
702 }
703
704 if (!BN_nnmod(val[0], a,m, ctx))
705 goto err;
706 aa = val[0];
707 if (BN_is_zero(aa)) {
708 BN_zero(rr);
709 ret = 1;
710 goto err;
711 }
712 if (!BN_to_montgomery(val[0], aa, mont, ctx))
713 goto err;
714
715 window = BN_window_bits_for_exponent_size(bits)((bits) > 671 ? 6 : (bits) > 239 ? 5 : (bits) > 79 ?
4 : (bits) > 23 ? 3 : 1);
716 if (window > 1) {
717 if (!BN_mod_mul_montgomery(d, val[0], val[0], mont, ctx))
718 goto err;
719 j = 1 << (window - 1);
720 for (i = 1; i < j; i++) {
721 if (((val[i] = BN_CTX_get(ctx)) == NULL((void *)0)) ||
722 !BN_mod_mul_montgomery(val[i], val[i - 1],
723 d, mont, ctx))
724 goto err;
725 }
726 }
727
728 start = 1; /* This is used to avoid multiplication etc
729 * when there is only the value '1' in the
730 * buffer. */
731 wvalue = 0; /* The 'value' of the window */
732 wstart = bits - 1; /* The top bit of the window */
733 wend = 0; /* The bottom bit of the window */
734
735 if (!BN_to_montgomery(r, BN_value_one(), mont, ctx))
736 goto err;
737 for (;;) {
738 if (BN_is_bit_set(p, wstart) == 0) {
739 if (!start) {
740 if (!BN_mod_mul_montgomery(r, r, r, mont, ctx))
741 goto err;
742 }
743 if (wstart == 0)
744 break;
745 wstart--;
746 continue;
747 }
748 /* We now have wstart on a 'set' bit, we now need to work out
749 * how bit a window to do. To do this we need to scan
750 * forward until the last set bit before the end of the
751 * window */
752 j = wstart;
753 wvalue = 1;
754 wend = 0;
755 for (i = 1; i < window; i++) {
756 if (wstart - i < 0)
757 break;
758 if (BN_is_bit_set(p, wstart - i)) {
759 wvalue <<= (i - wend);
760 wvalue |= 1;
761 wend = i;
762 }
763 }
764
765 /* wend is the size of the current window */
766 j = wend + 1;
767 /* add the 'bytes above' */
768 if (!start)
769 for (i = 0; i < j; i++) {
770 if (!BN_mod_mul_montgomery(r, r, r, mont, ctx))
771 goto err;
772 }
773
774 /* wvalue will be an odd number < 2^window */
775 if (!BN_mod_mul_montgomery(r, r, val[wvalue >> 1], mont, ctx))
776 goto err;
777
778 /* move the 'window' down further */
779 wstart -= wend + 1;
780 wvalue = 0;
781 start = 0;
782 if (wstart < 0)
783 break;
784 }
785 if (!BN_from_montgomery(rr, r,mont, ctx))
786 goto err;
787 ret = 1;
788
789err:
790 if ((in_mont == NULL((void *)0)) && (mont != NULL((void *)0)))
791 BN_MONT_CTX_free(mont);
792 BN_CTX_end(ctx);
793 return (ret);
794}
795
796int
797BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
798 BN_CTX *ctx, BN_MONT_CTX *in_mont)
799{
800 return BN_mod_exp_mont_internal(rr, a, p, m, ctx, in_mont,
801 (BN_get_flags(p, BN_FLG_CONSTTIME0x04) != 0));
802}
803
804int
805BN_mod_exp_mont_ct(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
806 BN_CTX *ctx, BN_MONT_CTX *in_mont)
807{
808 return BN_mod_exp_mont_internal(rr, a, p, m, ctx, in_mont, 1);
809}
810
811int
812BN_mod_exp_mont_nonct(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
813 BN_CTX *ctx, BN_MONT_CTX *in_mont)
814{
815 return BN_mod_exp_mont_internal(rr, a, p, m, ctx, in_mont, 0);
816}
817
818int
819BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONGunsigned long a, const BIGNUM *p, const BIGNUM *m,
820 BN_CTX *ctx, BN_MONT_CTX *in_mont)
821{
822 BN_MONT_CTX *mont = NULL((void *)0);
823 int b, bits, ret = 0;
824 int r_is_one;
825 BN_ULONGunsigned long w, next_w;
826 BIGNUM *d, *r, *t;
827 BIGNUM *swap_tmp;
828
829#define BN_MOD_MUL_WORD(r, w, m)(BN_mul_word(r, (w)) && ( (BN_mod_ct(t, r, m, ctx) &&
(swap_tmp = r, r = t, t = swap_tmp, 1)))) \
830 (BN_mul_word(r, (w)) && \
831 (/* BN_ucmp(r, (m)) < 0 ? 1 :*/ \
832 (BN_mod_ct(t, r, m, ctx) && (swap_tmp = r, r = t, t = swap_tmp, 1))))
833 /* BN_MOD_MUL_WORD is only used with 'w' large,
834 * so the BN_ucmp test is probably more overhead
835 * than always using BN_mod (which uses bn_copy if
836 * a similar test returns true). */
837 /* We can use BN_mod and do not need BN_nnmod because our
838 * accumulator is never negative (the result of BN_mod does
839 * not depend on the sign of the modulus).
840 */
841#define BN_TO_MONTGOMERY_WORD(r, w, mont)(BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont)
, ctx)) \
842 (BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont), ctx))
843
844 if (BN_get_flags(p, BN_FLG_CONSTTIME0x04) != 0) {
845 /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
846 BNerror(ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED)ERR_put_error(3,(0xfff),((2|64)),"/usr/src/lib/libcrypto/bn/bn_exp.c"
,846);
847 return -1;
848 }
849
850
851 if (!BN_is_odd(m)) {
852 BNerror(BN_R_CALLED_WITH_EVEN_MODULUS)ERR_put_error(3,(0xfff),(102),"/usr/src/lib/libcrypto/bn/bn_exp.c"
,852);
853 return (0);
854 }
855 if (m->top == 1)
856 a %= m->d[0]; /* make sure that 'a' is reduced */
857
858 bits = BN_num_bits(p);
859 if (bits == 0) {
860 /* x**0 mod 1 is still zero. */
861 if (BN_abs_is_word(m, 1)) {
862 ret = 1;
863 BN_zero(rr);
864 } else
865 ret = BN_one(rr);
866 return ret;
867 }
868 if (a == 0) {
869 BN_zero(rr);
870 ret = 1;
871 return ret;
872 }
873
874 BN_CTX_start(ctx);
875 if ((d = BN_CTX_get(ctx)) == NULL((void *)0))
876 goto err;
877 if ((r = BN_CTX_get(ctx)) == NULL((void *)0))
878 goto err;
879 if ((t = BN_CTX_get(ctx)) == NULL((void *)0))
880 goto err;
881
882 if (in_mont != NULL((void *)0))
883 mont = in_mont;
884 else {
885 if ((mont = BN_MONT_CTX_new()) == NULL((void *)0))
886 goto err;
887 if (!BN_MONT_CTX_set(mont, m, ctx))
888 goto err;
889 }
890
891 r_is_one = 1; /* except for Montgomery factor */
892
893 /* bits-1 >= 0 */
894
895 /* The result is accumulated in the product r*w. */
896 w = a; /* bit 'bits-1' of 'p' is always set */
897 for (b = bits - 2; b >= 0; b--) {
898 /* First, square r*w. */
899 next_w = w * w;
900 if ((next_w / w) != w) /* overflow */
901 {
902 if (r_is_one) {
903 if (!BN_TO_MONTGOMERY_WORD(r, w, mont)(BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont)
, ctx)))
904 goto err;
905 r_is_one = 0;
906 } else {
907 if (!BN_MOD_MUL_WORD(r, w, m)(BN_mul_word(r, (w)) && ( (BN_mod_ct(t, r, m, ctx) &&
(swap_tmp = r, r = t, t = swap_tmp, 1)))))
908 goto err;
909 }
910 next_w = 1;
911 }
912 w = next_w;
913 if (!r_is_one) {
914 if (!BN_mod_mul_montgomery(r, r, r, mont, ctx))
915 goto err;
916 }
917
918 /* Second, multiply r*w by 'a' if exponent bit is set. */
919 if (BN_is_bit_set(p, b)) {
920 next_w = w * a;
921 if ((next_w / a) != w) /* overflow */
922 {
923 if (r_is_one) {
924 if (!BN_TO_MONTGOMERY_WORD(r, w, mont)(BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont)
, ctx)))
925 goto err;
926 r_is_one = 0;
927 } else {
928 if (!BN_MOD_MUL_WORD(r, w, m)(BN_mul_word(r, (w)) && ( (BN_mod_ct(t, r, m, ctx) &&
(swap_tmp = r, r = t, t = swap_tmp, 1)))))
929 goto err;
930 }
931 next_w = a;
932 }
933 w = next_w;
934 }
935 }
936
937 /* Finally, set r:=r*w. */
938 if (w != 1) {
939 if (r_is_one) {
940 if (!BN_TO_MONTGOMERY_WORD(r, w, mont)(BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont)
, ctx)))
941 goto err;
942 r_is_one = 0;
943 } else {
944 if (!BN_MOD_MUL_WORD(r, w, m)(BN_mul_word(r, (w)) && ( (BN_mod_ct(t, r, m, ctx) &&
(swap_tmp = r, r = t, t = swap_tmp, 1)))))
945 goto err;
946 }
947 }
948
949 if (r_is_one) /* can happen only if a == 1*/
950 {
951 if (!BN_one(rr))
952 goto err;
953 } else {
954 if (!BN_from_montgomery(rr, r, mont, ctx))
955 goto err;
956 }
957 ret = 1;
958
959err:
960 if ((in_mont == NULL((void *)0)) && (mont != NULL((void *)0)))
961 BN_MONT_CTX_free(mont);
962 BN_CTX_end(ctx);
963 return (ret);
964}
965LCRYPTO_ALIAS(BN_mod_exp_mont_word)asm("");
966
967int
968BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
969 BN_CTX *ctx)
970{
971 int i, j, bits, wstart, wend, window, wvalue;
972 int start = 1;
973 BIGNUM *aa, *q;
974 /* Table of variables obtained from 'ctx' */
975 BIGNUM *val[TABLE_SIZE32];
976 BN_RECP_CTX recp;
977 int ret = 0;
978
979 if (BN_get_flags(p, BN_FLG_CONSTTIME0x04) != 0) {
980 /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
981 BNerror(ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED)ERR_put_error(3,(0xfff),((2|64)),"/usr/src/lib/libcrypto/bn/bn_exp.c"
,981);
982 return -1;
983 }
984
985 bits = BN_num_bits(p);
986 if (bits == 0) {
987 /* x**0 mod 1 is still zero. */
988 if (BN_abs_is_word(m, 1)) {
989 ret = 1;
990 BN_zero(r);
991 } else
992 ret = BN_one(r);
993 return ret;
994 }
995
996 BN_RECP_CTX_init(&recp);
997
998 BN_CTX_start(ctx);
999 if ((aa = BN_CTX_get(ctx)) == NULL((void *)0))
1000 goto err;
1001 if ((q = BN_CTX_get(ctx)) == NULL((void *)0))
1002 goto err;
1003 if ((val[0] = BN_CTX_get(ctx)) == NULL((void *)0))
1004 goto err;
1005
1006 if (m->neg) {
1007 /* ignore sign of 'm' */
1008 if (!bn_copy(aa, m))
1009 goto err;
1010 aa->neg = 0;
1011 if (BN_RECP_CTX_set(&recp, aa, ctx) <= 0)
1012 goto err;
1013 } else {
1014 if (BN_RECP_CTX_set(&recp, m, ctx) <= 0)
1015 goto err;
1016 }
1017
1018 if (!BN_nnmod(val[0], a, m, ctx))
1019 goto err;
1020 if (BN_is_zero(val[0])) {
1021 BN_zero(r);
1022 goto done;
1023 }
1024 if (!bn_copy(q, p))
1025 goto err;
1026
1027 window = BN_window_bits_for_exponent_size(bits)((bits) > 671 ? 6 : (bits) > 239 ? 5 : (bits) > 79 ?
4 : (bits) > 23 ? 3 : 1);
1028 if (window > 1) {
1029 if (!BN_mod_mul_reciprocal(aa, val[0], val[0], &recp, ctx))
1030 goto err;
1031 j = 1 << (window - 1);
1032 for (i = 1; i < j; i++) {
1033 if (((val[i] = BN_CTX_get(ctx)) == NULL((void *)0)) ||
1034 !BN_mod_mul_reciprocal(val[i], val[i - 1],
1035 aa, &recp, ctx))
1036 goto err;
1037 }
1038 }
1039
1040 start = 1; /* This is used to avoid multiplication etc
1041 * when there is only the value '1' in the
1042 * buffer. */
1043 wvalue = 0; /* The 'value' of the window */
1044 wstart = bits - 1; /* The top bit of the window */
1045 wend = 0; /* The bottom bit of the window */
1046
1047 if (!BN_one(r))
1048 goto err;
1049
1050 for (;;) {
1051 if (BN_is_bit_set(q, wstart) == 0) {
1052 if (!start)
1053 if (!BN_mod_mul_reciprocal(r, r, r, &recp, ctx))
1054 goto err;
1055 if (wstart == 0)
1056 break;
1057 wstart--;
1058 continue;
1059 }
1060 /* We now have wstart on a 'set' bit, we now need to work out
1061 * how bit a window to do. To do this we need to scan
1062 * forward until the last set bit before the end of the
1063 * window */
1064 j = wstart;
Value stored to 'j' is never read
1065 wvalue = 1;
1066 wend = 0;
1067 for (i = 1; i < window; i++) {
1068 if (wstart - i < 0)
1069 break;
1070 if (BN_is_bit_set(q, wstart - i)) {
1071 wvalue <<= (i - wend);
1072 wvalue |= 1;
1073 wend = i;
1074 }
1075 }
1076
1077 /* wend is the size of the current window */
1078 j = wend + 1;
1079 /* add the 'bytes above' */
1080 if (!start)
1081 for (i = 0; i < j; i++) {
1082 if (!BN_mod_mul_reciprocal(r, r, r, &recp, ctx))
1083 goto err;
1084 }
1085
1086 /* wvalue will be an odd number < 2^window */
1087 if (!BN_mod_mul_reciprocal(r, r, val[wvalue >> 1], &recp, ctx))
1088 goto err;
1089
1090 /* move the 'window' down further */
1091 wstart -= wend + 1;
1092 wvalue = 0;
1093 start = 0;
1094 if (wstart < 0)
1095 break;
1096 }
1097
1098 done:
1099 ret = 1;
1100
1101 err:
1102 BN_CTX_end(ctx);
1103 BN_RECP_CTX_free(&recp);
1104
1105 return ret;
1106}
1107
1108static int
1109BN_mod_exp_internal(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
1110 BN_CTX *ctx, int ct)
1111{
1112 int ret;
1113
1114
1115 /* For even modulus m = 2^k*m_odd, it might make sense to compute
1116 * a^p mod m_odd and a^p mod 2^k separately (with Montgomery
1117 * exponentiation for the odd part), using appropriate exponent
1118 * reductions, and combine the results using the CRT.
1119 *
1120 * For now, we use Montgomery only if the modulus is odd; otherwise,
1121 * exponentiation using the reciprocal-based quick remaindering
1122 * algorithm is used.
1123 *
1124 * (Timing obtained with expspeed.c [computations a^p mod m
1125 * where a, p, m are of the same length: 256, 512, 1024, 2048,
1126 * 4096, 8192 bits], compared to the running time of the
1127 * standard algorithm:
1128 *
1129 * BN_mod_exp_mont 33 .. 40 % [AMD K6-2, Linux, debug configuration]
1130 * 55 .. 77 % [UltraSparc processor, but
1131 * debug-solaris-sparcv8-gcc conf.]
1132 *
1133 * BN_mod_exp_recp 50 .. 70 % [AMD K6-2, Linux, debug configuration]
1134 * 62 .. 118 % [UltraSparc, debug-solaris-sparcv8-gcc]
1135 *
1136 * On the Sparc, BN_mod_exp_recp was faster than BN_mod_exp_mont
1137 * at 2048 and more bits, but at 512 and 1024 bits, it was
1138 * slower even than the standard algorithm!
1139 *
1140 * "Real" timings [linux-elf, solaris-sparcv9-gcc configurations]
1141 * should be obtained when the new Montgomery reduction code
1142 * has been integrated into OpenSSL.)
1143 */
1144
1145 if (BN_is_odd(m)) {
1146 if (a->top == 1 && !a->neg && !ct) {
1147 BN_ULONGunsigned long A = a->d[0];
1148 ret = BN_mod_exp_mont_word(r, A,p, m,ctx, NULL((void *)0));
1149 } else
1150 ret = BN_mod_exp_mont_ct(r, a,p, m,ctx, NULL((void *)0));
1151 } else {
1152 ret = BN_mod_exp_recp(r, a,p, m, ctx);
1153 }
1154
1155 return (ret);
1156}
1157
1158int
1159BN_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
1160 BN_CTX *ctx)
1161{
1162 return BN_mod_exp_internal(r, a, p, m, ctx,
1163 (BN_get_flags(p, BN_FLG_CONSTTIME0x04) != 0));
1164}
1165
1166int
1167BN_mod_exp_ct(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
1168 BN_CTX *ctx)
1169{
1170 return BN_mod_exp_internal(r, a, p, m, ctx, 1);
1171}
1172
1173int
1174BN_mod_exp_nonct(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
1175 BN_CTX *ctx)
1176{
1177 return BN_mod_exp_internal(r, a, p, m, ctx, 0);
1178}
1179
1180int
1181BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,
1182 const BIGNUM *a2, const BIGNUM *p2, const BIGNUM *m, BN_CTX *ctx,
1183 BN_MONT_CTX *in_mont)
1184{
1185 int i, j, bits, b, bits1, bits2, ret = 0, wpos1, wpos2, window1, window2, wvalue1, wvalue2;
1186 int r_is_one = 1;
1187 BIGNUM *d, *r;
1188 const BIGNUM *a_mod_m;
1189 /* Tables of variables obtained from 'ctx' */
1190 BIGNUM *val1[TABLE_SIZE32], *val2[TABLE_SIZE32];
1191 BN_MONT_CTX *mont = NULL((void *)0);
1192
1193
1194 if (!BN_is_odd(m)) {
1195 BNerror(BN_R_CALLED_WITH_EVEN_MODULUS)ERR_put_error(3,(0xfff),(102),"/usr/src/lib/libcrypto/bn/bn_exp.c"
,1195);
1196 return (0);
1197 }
1198 bits1 = BN_num_bits(p1);
1199 bits2 = BN_num_bits(p2);
1200 if ((bits1 == 0) && (bits2 == 0)) {
1201 ret = BN_one(rr);
1202 return ret;
1203 }
1204
1205 bits = (bits1 > bits2) ? bits1 : bits2;
1206
1207 BN_CTX_start(ctx);
1208 if ((d = BN_CTX_get(ctx)) == NULL((void *)0))
1209 goto err;
1210 if ((r = BN_CTX_get(ctx)) == NULL((void *)0))
1211 goto err;
1212 if ((val1[0] = BN_CTX_get(ctx)) == NULL((void *)0))
1213 goto err;
1214 if ((val2[0] = BN_CTX_get(ctx)) == NULL((void *)0))
1215 goto err;
1216
1217 if (in_mont != NULL((void *)0))
1218 mont = in_mont;
1219 else {
1220 if ((mont = BN_MONT_CTX_new()) == NULL((void *)0))
1221 goto err;
1222 if (!BN_MONT_CTX_set(mont, m, ctx))
1223 goto err;
1224 }
1225
1226 window1 = BN_window_bits_for_exponent_size(bits1)((bits1) > 671 ? 6 : (bits1) > 239 ? 5 : (bits1) > 79
? 4 : (bits1) > 23 ? 3 : 1);
1227 window2 = BN_window_bits_for_exponent_size(bits2)((bits2) > 671 ? 6 : (bits2) > 239 ? 5 : (bits2) > 79
? 4 : (bits2) > 23 ? 3 : 1);
1228
1229 /*
1230 * Build table for a1: val1[i] := a1^(2*i + 1) mod m for i = 0 .. 2^(window1-1)
1231 */
1232 if (!BN_nnmod(val1[0], a1, m, ctx))
1233 goto err;
1234 a_mod_m = val1[0];
1235 if (BN_is_zero(a_mod_m)) {
1236 BN_zero(rr);
1237 ret = 1;
1238 goto err;
1239 }
1240
1241 if (!BN_to_montgomery(val1[0], a_mod_m, mont, ctx))
1242 goto err;
1243 if (window1 > 1) {
1244 if (!BN_mod_mul_montgomery(d, val1[0], val1[0], mont, ctx))
1245 goto err;
1246
1247 j = 1 << (window1 - 1);
1248 for (i = 1; i < j; i++) {
1249 if (((val1[i] = BN_CTX_get(ctx)) == NULL((void *)0)) ||
1250 !BN_mod_mul_montgomery(val1[i], val1[i - 1],
1251 d, mont, ctx))
1252 goto err;
1253 }
1254 }
1255
1256
1257 /*
1258 * Build table for a2: val2[i] := a2^(2*i + 1) mod m for i = 0 .. 2^(window2-1)
1259 */
1260 if (!BN_nnmod(val2[0], a2, m, ctx))
1261 goto err;
1262 a_mod_m = val2[0];
1263 if (BN_is_zero(a_mod_m)) {
1264 BN_zero(rr);
1265 ret = 1;
1266 goto err;
1267 }
1268 if (!BN_to_montgomery(val2[0], a_mod_m, mont, ctx))
1269 goto err;
1270 if (window2 > 1) {
1271 if (!BN_mod_mul_montgomery(d, val2[0], val2[0], mont, ctx))
1272 goto err;
1273
1274 j = 1 << (window2 - 1);
1275 for (i = 1; i < j; i++) {
1276 if (((val2[i] = BN_CTX_get(ctx)) == NULL((void *)0)) ||
1277 !BN_mod_mul_montgomery(val2[i], val2[i - 1],
1278 d, mont, ctx))
1279 goto err;
1280 }
1281 }
1282
1283
1284 /* Now compute the power product, using independent windows. */
1285 r_is_one = 1;
1286 wvalue1 = 0; /* The 'value' of the first window */
1287 wvalue2 = 0; /* The 'value' of the second window */
1288 wpos1 = 0; /* If wvalue1 > 0, the bottom bit of the first window */
1289 wpos2 = 0; /* If wvalue2 > 0, the bottom bit of the second window */
1290
1291 if (!BN_to_montgomery(r, BN_value_one(), mont, ctx))
1292 goto err;
1293 for (b = bits - 1; b >= 0; b--) {
1294 if (!r_is_one) {
1295 if (!BN_mod_mul_montgomery(r, r,r, mont, ctx))
1296 goto err;
1297 }
1298
1299 if (!wvalue1)
1300 if (BN_is_bit_set(p1, b)) {
1301 /* consider bits b-window1+1 .. b for this window */
1302 i = b - window1 + 1;
1303 while (!BN_is_bit_set(p1, i)) /* works for i<0 */
1304 i++;
1305 wpos1 = i;
1306 wvalue1 = 1;
1307 for (i = b - 1; i >= wpos1; i--) {
1308 wvalue1 <<= 1;
1309 if (BN_is_bit_set(p1, i))
1310 wvalue1++;
1311 }
1312 }
1313
1314 if (!wvalue2)
1315 if (BN_is_bit_set(p2, b)) {
1316 /* consider bits b-window2+1 .. b for this window */
1317 i = b - window2 + 1;
1318 while (!BN_is_bit_set(p2, i))
1319 i++;
1320 wpos2 = i;
1321 wvalue2 = 1;
1322 for (i = b - 1; i >= wpos2; i--) {
1323 wvalue2 <<= 1;
1324 if (BN_is_bit_set(p2, i))
1325 wvalue2++;
1326 }
1327 }
1328
1329 if (wvalue1 && b == wpos1) {
1330 /* wvalue1 is odd and < 2^window1 */
1331 if (!BN_mod_mul_montgomery(r, r, val1[wvalue1 >> 1],
1332 mont, ctx))
1333 goto err;
1334 wvalue1 = 0;
1335 r_is_one = 0;
1336 }
1337
1338 if (wvalue2 && b == wpos2) {
1339 /* wvalue2 is odd and < 2^window2 */
1340 if (!BN_mod_mul_montgomery(r, r, val2[wvalue2 >> 1],
1341 mont, ctx))
1342 goto err;
1343 wvalue2 = 0;
1344 r_is_one = 0;
1345 }
1346 }
1347 if (!BN_from_montgomery(rr, r,mont, ctx))
1348 goto err;
1349 ret = 1;
1350
1351err:
1352 if ((in_mont == NULL((void *)0)) && (mont != NULL((void *)0)))
1353 BN_MONT_CTX_free(mont);
1354 BN_CTX_end(ctx);
1355 return (ret);
1356}
1357LCRYPTO_ALIAS(BN_mod_exp2_mont)asm("");