| File: | src/lib/libcrypto/bn/bn_exp.c |
| Warning: | line 494, column 3 Value stored to 'j' is never read |
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| 1 | /* $OpenBSD: bn_exp.c,v 1.31 2017/05/02 03:59:44 deraadt 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_lcl.h" |
| 118 | #include "constant_time_locl.h" |
| 119 | |
| 120 | /* maximum precomputation table size for *variable* sliding windows */ |
| 121 | #define TABLE_SIZE32 32 |
| 122 | |
| 123 | /* this one works - simple but works */ |
| 124 | int |
| 125 | BN_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx) |
| 126 | { |
| 127 | int i, bits, ret = 0; |
| 128 | BIGNUM *v, *rr; |
| 129 | |
| 130 | if (BN_get_flags(p, BN_FLG_CONSTTIME0x04) != 0) { |
| 131 | /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ |
| 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 | if ((r == a) || (r == p)) |
| 138 | rr = BN_CTX_get(ctx); |
| 139 | else |
| 140 | rr = r; |
| 141 | v = BN_CTX_get(ctx); |
| 142 | if (rr == NULL((void *)0) || v == NULL((void *)0)) |
| 143 | goto err; |
| 144 | |
| 145 | if (BN_copy(v, a) == NULL((void *)0)) |
| 146 | goto err; |
| 147 | bits = BN_num_bits(p); |
| 148 | |
| 149 | if (BN_is_odd(p)) { |
| 150 | if (BN_copy(rr, a) == NULL((void *)0)) |
| 151 | goto err; |
| 152 | } else { |
| 153 | if (!BN_one(rr)BN_set_word((rr), 1)) |
| 154 | goto err; |
| 155 | } |
| 156 | |
| 157 | for (i = 1; i < bits; i++) { |
| 158 | if (!BN_sqr(v, v, ctx)) |
| 159 | goto err; |
| 160 | if (BN_is_bit_set(p, i)) { |
| 161 | if (!BN_mul(rr, rr, v, ctx)) |
| 162 | goto err; |
| 163 | } |
| 164 | } |
| 165 | ret = 1; |
| 166 | |
| 167 | err: |
| 168 | if (r != rr && rr != NULL((void *)0)) |
| 169 | BN_copy(r, rr); |
| 170 | BN_CTX_end(ctx); |
| 171 | bn_check_top(r); |
| 172 | return (ret); |
| 173 | } |
| 174 | |
| 175 | static int |
| 176 | BN_mod_exp_internal(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, |
| 177 | BN_CTX *ctx, int ct) |
| 178 | { |
| 179 | int ret; |
| 180 | |
| 181 | bn_check_top(a); |
| 182 | bn_check_top(p); |
| 183 | bn_check_top(m); |
| 184 | |
| 185 | /* For even modulus m = 2^k*m_odd, it might make sense to compute |
| 186 | * a^p mod m_odd and a^p mod 2^k separately (with Montgomery |
| 187 | * exponentiation for the odd part), using appropriate exponent |
| 188 | * reductions, and combine the results using the CRT. |
| 189 | * |
| 190 | * For now, we use Montgomery only if the modulus is odd; otherwise, |
| 191 | * exponentiation using the reciprocal-based quick remaindering |
| 192 | * algorithm is used. |
| 193 | * |
| 194 | * (Timing obtained with expspeed.c [computations a^p mod m |
| 195 | * where a, p, m are of the same length: 256, 512, 1024, 2048, |
| 196 | * 4096, 8192 bits], compared to the running time of the |
| 197 | * standard algorithm: |
| 198 | * |
| 199 | * BN_mod_exp_mont 33 .. 40 % [AMD K6-2, Linux, debug configuration] |
| 200 | * 55 .. 77 % [UltraSparc processor, but |
| 201 | * debug-solaris-sparcv8-gcc conf.] |
| 202 | * |
| 203 | * BN_mod_exp_recp 50 .. 70 % [AMD K6-2, Linux, debug configuration] |
| 204 | * 62 .. 118 % [UltraSparc, debug-solaris-sparcv8-gcc] |
| 205 | * |
| 206 | * On the Sparc, BN_mod_exp_recp was faster than BN_mod_exp_mont |
| 207 | * at 2048 and more bits, but at 512 and 1024 bits, it was |
| 208 | * slower even than the standard algorithm! |
| 209 | * |
| 210 | * "Real" timings [linux-elf, solaris-sparcv9-gcc configurations] |
| 211 | * should be obtained when the new Montgomery reduction code |
| 212 | * has been integrated into OpenSSL.) |
| 213 | */ |
| 214 | |
| 215 | if (BN_is_odd(m)) { |
| 216 | if (a->top == 1 && !a->neg && !ct) { |
| 217 | BN_ULONGunsigned long A = a->d[0]; |
| 218 | ret = BN_mod_exp_mont_word(r, A,p, m,ctx, NULL((void *)0)); |
| 219 | } else |
| 220 | ret = BN_mod_exp_mont_ct(r, a,p, m,ctx, NULL((void *)0)); |
| 221 | } else { |
| 222 | ret = BN_mod_exp_recp(r, a,p, m, ctx); |
| 223 | } |
| 224 | |
| 225 | bn_check_top(r); |
| 226 | return (ret); |
| 227 | } |
| 228 | |
| 229 | int |
| 230 | BN_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, |
| 231 | BN_CTX *ctx) |
| 232 | { |
| 233 | return BN_mod_exp_internal(r, a, p, m, ctx, |
| 234 | (BN_get_flags(p, BN_FLG_CONSTTIME0x04) != 0)); |
| 235 | } |
| 236 | |
| 237 | int |
| 238 | BN_mod_exp_ct(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, |
| 239 | BN_CTX *ctx) |
| 240 | { |
| 241 | return BN_mod_exp_internal(r, a, p, m, ctx, 1); |
| 242 | } |
| 243 | |
| 244 | |
| 245 | int |
| 246 | BN_mod_exp_nonct(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, |
| 247 | BN_CTX *ctx) |
| 248 | { |
| 249 | return BN_mod_exp_internal(r, a, p, m, ctx, 0); |
| 250 | } |
| 251 | |
| 252 | |
| 253 | int |
| 254 | BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, |
| 255 | BN_CTX *ctx) |
| 256 | { |
| 257 | int i, j, bits, ret = 0, wstart, wend, window, wvalue; |
| 258 | int start = 1; |
| 259 | BIGNUM *aa; |
| 260 | /* Table of variables obtained from 'ctx' */ |
| 261 | BIGNUM *val[TABLE_SIZE32]; |
| 262 | BN_RECP_CTX recp; |
| 263 | |
| 264 | if (BN_get_flags(p, BN_FLG_CONSTTIME0x04) != 0) { |
| 265 | /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ |
| 266 | BNerror(ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED)ERR_put_error(3,(0xfff),((2|64)),"/usr/src/lib/libcrypto/bn/bn_exp.c" ,266); |
| 267 | return -1; |
| 268 | } |
| 269 | |
| 270 | bits = BN_num_bits(p); |
| 271 | if (bits == 0) { |
| 272 | /* x**0 mod 1 is still zero. */ |
| 273 | if (BN_is_one(m)) { |
| 274 | ret = 1; |
| 275 | BN_zero(r)(BN_set_word((r),0)); |
| 276 | } else |
| 277 | ret = BN_one(r)BN_set_word((r), 1); |
| 278 | return ret; |
| 279 | } |
| 280 | |
| 281 | BN_CTX_start(ctx); |
| 282 | if ((aa = BN_CTX_get(ctx)) == NULL((void *)0)) |
| 283 | goto err; |
| 284 | if ((val[0] = BN_CTX_get(ctx)) == NULL((void *)0)) |
| 285 | goto err; |
| 286 | |
| 287 | BN_RECP_CTX_init(&recp); |
| 288 | if (m->neg) { |
| 289 | /* ignore sign of 'm' */ |
| 290 | if (!BN_copy(aa, m)) |
| 291 | goto err; |
| 292 | aa->neg = 0; |
| 293 | if (BN_RECP_CTX_set(&recp, aa, ctx) <= 0) |
| 294 | goto err; |
| 295 | } else { |
| 296 | if (BN_RECP_CTX_set(&recp, m, ctx) <= 0) |
| 297 | goto err; |
| 298 | } |
| 299 | |
| 300 | if (!BN_nnmod(val[0], a, m, ctx)) |
| 301 | goto err; /* 1 */ |
| 302 | if (BN_is_zero(val[0])) { |
| 303 | BN_zero(r)(BN_set_word((r),0)); |
| 304 | ret = 1; |
| 305 | goto err; |
| 306 | } |
| 307 | |
| 308 | window = BN_window_bits_for_exponent_size(bits)((bits) > 671 ? 6 : (bits) > 239 ? 5 : (bits) > 79 ? 4 : (bits) > 23 ? 3 : 1); |
| 309 | if (window > 1) { |
| 310 | if (!BN_mod_mul_reciprocal(aa, val[0], val[0], &recp, ctx)) |
| 311 | goto err; /* 2 */ |
| 312 | j = 1 << (window - 1); |
| 313 | for (i = 1; i < j; i++) { |
| 314 | if (((val[i] = BN_CTX_get(ctx)) == NULL((void *)0)) || |
| 315 | !BN_mod_mul_reciprocal(val[i], val[i - 1], |
| 316 | aa, &recp, ctx)) |
| 317 | goto err; |
| 318 | } |
| 319 | } |
| 320 | |
| 321 | start = 1; /* This is used to avoid multiplication etc |
| 322 | * when there is only the value '1' in the |
| 323 | * buffer. */ |
| 324 | wvalue = 0; /* The 'value' of the window */ |
| 325 | wstart = bits - 1; /* The top bit of the window */ |
| 326 | wend = 0; /* The bottom bit of the window */ |
| 327 | |
| 328 | if (!BN_one(r)BN_set_word((r), 1)) |
| 329 | goto err; |
| 330 | |
| 331 | for (;;) { |
| 332 | if (BN_is_bit_set(p, wstart) == 0) { |
| 333 | if (!start) |
| 334 | if (!BN_mod_mul_reciprocal(r, r,r, &recp, ctx)) |
| 335 | goto err; |
| 336 | if (wstart == 0) |
| 337 | break; |
| 338 | wstart--; |
| 339 | continue; |
| 340 | } |
| 341 | /* We now have wstart on a 'set' bit, we now need to work out |
| 342 | * how bit a window to do. To do this we need to scan |
| 343 | * forward until the last set bit before the end of the |
| 344 | * window */ |
| 345 | j = wstart; |
| 346 | wvalue = 1; |
| 347 | wend = 0; |
| 348 | for (i = 1; i < window; i++) { |
| 349 | if (wstart - i < 0) |
| 350 | break; |
| 351 | if (BN_is_bit_set(p, wstart - i)) { |
| 352 | wvalue <<= (i - wend); |
| 353 | wvalue |= 1; |
| 354 | wend = i; |
| 355 | } |
| 356 | } |
| 357 | |
| 358 | /* wend is the size of the current window */ |
| 359 | j = wend + 1; |
| 360 | /* add the 'bytes above' */ |
| 361 | if (!start) |
| 362 | for (i = 0; i < j; i++) { |
| 363 | if (!BN_mod_mul_reciprocal(r, r,r, &recp, ctx)) |
| 364 | goto err; |
| 365 | } |
| 366 | |
| 367 | /* wvalue will be an odd number < 2^window */ |
| 368 | if (!BN_mod_mul_reciprocal(r, r,val[wvalue >> 1], &recp, ctx)) |
| 369 | goto err; |
| 370 | |
| 371 | /* move the 'window' down further */ |
| 372 | wstart -= wend + 1; |
| 373 | wvalue = 0; |
| 374 | start = 0; |
| 375 | if (wstart < 0) |
| 376 | break; |
| 377 | } |
| 378 | ret = 1; |
| 379 | |
| 380 | err: |
| 381 | BN_CTX_end(ctx); |
| 382 | BN_RECP_CTX_free(&recp); |
| 383 | bn_check_top(r); |
| 384 | return (ret); |
| 385 | } |
| 386 | |
| 387 | static int |
| 388 | BN_mod_exp_mont_internal(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, |
| 389 | BN_CTX *ctx, BN_MONT_CTX *in_mont, int ct) |
| 390 | { |
| 391 | int i, j, bits, ret = 0, wstart, wend, window, wvalue; |
| 392 | int start = 1; |
| 393 | BIGNUM *d, *r; |
| 394 | const BIGNUM *aa; |
| 395 | /* Table of variables obtained from 'ctx' */ |
| 396 | BIGNUM *val[TABLE_SIZE32]; |
| 397 | BN_MONT_CTX *mont = NULL((void *)0); |
| 398 | |
| 399 | if (ct) { |
| 400 | return BN_mod_exp_mont_consttime(rr, a, p, m, ctx, in_mont); |
| 401 | } |
| 402 | |
| 403 | bn_check_top(a); |
| 404 | bn_check_top(p); |
| 405 | bn_check_top(m); |
| 406 | |
| 407 | if (!BN_is_odd(m)) { |
| 408 | BNerror(BN_R_CALLED_WITH_EVEN_MODULUS)ERR_put_error(3,(0xfff),(102),"/usr/src/lib/libcrypto/bn/bn_exp.c" ,408); |
| 409 | return (0); |
| 410 | } |
| 411 | |
| 412 | bits = BN_num_bits(p); |
| 413 | if (bits == 0) { |
| 414 | /* x**0 mod 1 is still zero. */ |
| 415 | if (BN_is_one(m)) { |
| 416 | ret = 1; |
| 417 | BN_zero(rr)(BN_set_word((rr),0)); |
| 418 | } else |
| 419 | ret = BN_one(rr)BN_set_word((rr), 1); |
| 420 | return ret; |
| 421 | } |
| 422 | |
| 423 | BN_CTX_start(ctx); |
| 424 | if ((d = BN_CTX_get(ctx)) == NULL((void *)0)) |
| 425 | goto err; |
| 426 | if ((r = BN_CTX_get(ctx)) == NULL((void *)0)) |
| 427 | goto err; |
| 428 | if ((val[0] = BN_CTX_get(ctx)) == NULL((void *)0)) |
| 429 | goto err; |
| 430 | |
| 431 | /* If this is not done, things will break in the montgomery |
| 432 | * part */ |
| 433 | |
| 434 | if (in_mont != NULL((void *)0)) |
| 435 | mont = in_mont; |
| 436 | else { |
| 437 | if ((mont = BN_MONT_CTX_new()) == NULL((void *)0)) |
| 438 | goto err; |
| 439 | if (!BN_MONT_CTX_set(mont, m, ctx)) |
| 440 | goto err; |
| 441 | } |
| 442 | |
| 443 | if (a->neg || BN_ucmp(a, m) >= 0) { |
| 444 | if (!BN_nnmod(val[0], a,m, ctx)) |
| 445 | goto err; |
| 446 | aa = val[0]; |
| 447 | } else |
| 448 | aa = a; |
| 449 | if (BN_is_zero(aa)) { |
| 450 | BN_zero(rr)(BN_set_word((rr),0)); |
| 451 | ret = 1; |
| 452 | goto err; |
| 453 | } |
| 454 | if (!BN_to_montgomery(val[0], aa, mont, ctx)) |
| 455 | goto err; /* 1 */ |
| 456 | |
| 457 | window = BN_window_bits_for_exponent_size(bits)((bits) > 671 ? 6 : (bits) > 239 ? 5 : (bits) > 79 ? 4 : (bits) > 23 ? 3 : 1); |
| 458 | if (window > 1) { |
| 459 | if (!BN_mod_mul_montgomery(d, val[0], val[0], mont, ctx)) |
| 460 | goto err; /* 2 */ |
| 461 | j = 1 << (window - 1); |
| 462 | for (i = 1; i < j; i++) { |
| 463 | if (((val[i] = BN_CTX_get(ctx)) == NULL((void *)0)) || |
| 464 | !BN_mod_mul_montgomery(val[i], val[i - 1], |
| 465 | d, mont, ctx)) |
| 466 | goto err; |
| 467 | } |
| 468 | } |
| 469 | |
| 470 | start = 1; /* This is used to avoid multiplication etc |
| 471 | * when there is only the value '1' in the |
| 472 | * buffer. */ |
| 473 | wvalue = 0; /* The 'value' of the window */ |
| 474 | wstart = bits - 1; /* The top bit of the window */ |
| 475 | wend = 0; /* The bottom bit of the window */ |
| 476 | |
| 477 | if (!BN_to_montgomery(r, BN_value_one(), mont, ctx)) |
| 478 | goto err; |
| 479 | for (;;) { |
| 480 | if (BN_is_bit_set(p, wstart) == 0) { |
| 481 | if (!start) { |
| 482 | if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) |
| 483 | goto err; |
| 484 | } |
| 485 | if (wstart == 0) |
| 486 | break; |
| 487 | wstart--; |
| 488 | continue; |
| 489 | } |
| 490 | /* We now have wstart on a 'set' bit, we now need to work out |
| 491 | * how bit a window to do. To do this we need to scan |
| 492 | * forward until the last set bit before the end of the |
| 493 | * window */ |
| 494 | j = wstart; |
Value stored to 'j' is never read | |
| 495 | wvalue = 1; |
| 496 | wend = 0; |
| 497 | for (i = 1; i < window; i++) { |
| 498 | if (wstart - i < 0) |
| 499 | break; |
| 500 | if (BN_is_bit_set(p, wstart - i)) { |
| 501 | wvalue <<= (i - wend); |
| 502 | wvalue |= 1; |
| 503 | wend = i; |
| 504 | } |
| 505 | } |
| 506 | |
| 507 | /* wend is the size of the current window */ |
| 508 | j = wend + 1; |
| 509 | /* add the 'bytes above' */ |
| 510 | if (!start) |
| 511 | for (i = 0; i < j; i++) { |
| 512 | if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) |
| 513 | goto err; |
| 514 | } |
| 515 | |
| 516 | /* wvalue will be an odd number < 2^window */ |
| 517 | if (!BN_mod_mul_montgomery(r, r, val[wvalue >> 1], mont, ctx)) |
| 518 | goto err; |
| 519 | |
| 520 | /* move the 'window' down further */ |
| 521 | wstart -= wend + 1; |
| 522 | wvalue = 0; |
| 523 | start = 0; |
| 524 | if (wstart < 0) |
| 525 | break; |
| 526 | } |
| 527 | if (!BN_from_montgomery(rr, r,mont, ctx)) |
| 528 | goto err; |
| 529 | ret = 1; |
| 530 | |
| 531 | err: |
| 532 | if ((in_mont == NULL((void *)0)) && (mont != NULL((void *)0))) |
| 533 | BN_MONT_CTX_free(mont); |
| 534 | BN_CTX_end(ctx); |
| 535 | bn_check_top(rr); |
| 536 | return (ret); |
| 537 | } |
| 538 | |
| 539 | int |
| 540 | BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, |
| 541 | BN_CTX *ctx, BN_MONT_CTX *in_mont) |
| 542 | { |
| 543 | return BN_mod_exp_mont_internal(rr, a, p, m, ctx, in_mont, |
| 544 | (BN_get_flags(p, BN_FLG_CONSTTIME0x04) != 0)); |
| 545 | } |
| 546 | |
| 547 | int |
| 548 | BN_mod_exp_mont_ct(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, |
| 549 | BN_CTX *ctx, BN_MONT_CTX *in_mont) |
| 550 | { |
| 551 | return BN_mod_exp_mont_internal(rr, a, p, m, ctx, in_mont, 1); |
| 552 | } |
| 553 | |
| 554 | int |
| 555 | BN_mod_exp_mont_nonct(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, |
| 556 | BN_CTX *ctx, BN_MONT_CTX *in_mont) |
| 557 | { |
| 558 | return BN_mod_exp_mont_internal(rr, a, p, m, ctx, in_mont, 0); |
| 559 | } |
| 560 | |
| 561 | /* BN_mod_exp_mont_consttime() stores the precomputed powers in a specific layout |
| 562 | * so that accessing any of these table values shows the same access pattern as far |
| 563 | * as cache lines are concerned. The following functions are used to transfer a BIGNUM |
| 564 | * from/to that table. */ |
| 565 | |
| 566 | static int |
| 567 | MOD_EXP_CTIME_COPY_TO_PREBUF(const BIGNUM *b, int top, unsigned char *buf, |
| 568 | int idx, int window) |
| 569 | { |
| 570 | int i, j; |
| 571 | int width = 1 << window; |
| 572 | BN_ULONGunsigned long *table = (BN_ULONGunsigned long *)buf; |
| 573 | |
| 574 | if (top > b->top) |
| 575 | top = b->top; /* this works because 'buf' is explicitly zeroed */ |
| 576 | |
| 577 | for (i = 0, j = idx; i < top; i++, j += width) { |
| 578 | table[j] = b->d[i]; |
| 579 | } |
| 580 | |
| 581 | return 1; |
| 582 | } |
| 583 | |
| 584 | static int |
| 585 | MOD_EXP_CTIME_COPY_FROM_PREBUF(BIGNUM *b, int top, unsigned char *buf, int idx, |
| 586 | int window) |
| 587 | { |
| 588 | int i, j; |
| 589 | int width = 1 << window; |
| 590 | volatile BN_ULONGunsigned long *table = (volatile BN_ULONGunsigned long *)buf; |
| 591 | |
| 592 | if (bn_wexpand(b, top)(((top) <= (b)->dmax)?(b):bn_expand2((b),(top))) == NULL((void *)0)) |
| 593 | return 0; |
| 594 | |
| 595 | if (window <= 3) { |
| 596 | for (i = 0; i < top; i++, table += width) { |
| 597 | BN_ULONGunsigned long acc = 0; |
| 598 | |
| 599 | for (j = 0; j < width; j++) { |
| 600 | acc |= table[j] & |
| 601 | ((BN_ULONGunsigned long)0 - (constant_time_eq_int(j,idx)&1)); |
| 602 | } |
| 603 | |
| 604 | b->d[i] = acc; |
| 605 | } |
| 606 | } else { |
| 607 | int xstride = 1 << (window - 2); |
| 608 | BN_ULONGunsigned long y0, y1, y2, y3; |
| 609 | |
| 610 | i = idx >> (window - 2); /* equivalent of idx / xstride */ |
| 611 | idx &= xstride - 1; /* equivalent of idx % xstride */ |
| 612 | |
| 613 | y0 = (BN_ULONGunsigned long)0 - (constant_time_eq_int(i,0)&1); |
| 614 | y1 = (BN_ULONGunsigned long)0 - (constant_time_eq_int(i,1)&1); |
| 615 | y2 = (BN_ULONGunsigned long)0 - (constant_time_eq_int(i,2)&1); |
| 616 | y3 = (BN_ULONGunsigned long)0 - (constant_time_eq_int(i,3)&1); |
| 617 | |
| 618 | for (i = 0; i < top; i++, table += width) { |
| 619 | BN_ULONGunsigned long acc = 0; |
| 620 | |
| 621 | for (j = 0; j < xstride; j++) { |
| 622 | acc |= ( (table[j + 0 * xstride] & y0) | |
| 623 | (table[j + 1 * xstride] & y1) | |
| 624 | (table[j + 2 * xstride] & y2) | |
| 625 | (table[j + 3 * xstride] & y3) ) |
| 626 | & ((BN_ULONGunsigned long)0 - (constant_time_eq_int(j,idx)&1)); |
| 627 | } |
| 628 | |
| 629 | b->d[i] = acc; |
| 630 | } |
| 631 | } |
| 632 | b->top = top; |
| 633 | bn_correct_top(b){ unsigned long *ftl; int tmp_top = (b)->top; if (tmp_top > 0) { for (ftl= &((b)->d[tmp_top-1]); tmp_top > 0; tmp_top --) if (*(ftl--)) break; (b)->top = tmp_top; } ; }; |
| 634 | return 1; |
| 635 | } |
| 636 | |
| 637 | /* Given a pointer value, compute the next address that is a cache line multiple. */ |
| 638 | #define MOD_EXP_CTIME_ALIGN(x_)((unsigned char*)(x_) + (( 64 ) - (((size_t)(x_)) & ((( 64 ) - 1))))) \ |
| 639 | ((unsigned char*)(x_) + (MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH( 64 ) - (((size_t)(x_)) & (MOD_EXP_CTIME_MIN_CACHE_LINE_MASK(( 64 ) - 1))))) |
| 640 | |
| 641 | /* This variant of BN_mod_exp_mont() uses fixed windows and the special |
| 642 | * precomputation memory layout to limit data-dependency to a minimum |
| 643 | * to protect secret exponents (cf. the hyper-threading timing attacks |
| 644 | * pointed out by Colin Percival, |
| 645 | * http://www.daemonology.net/hyperthreading-considered-harmful/) |
| 646 | */ |
| 647 | int |
| 648 | BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, |
| 649 | const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont) |
| 650 | { |
| 651 | int i, bits, ret = 0, window, wvalue; |
| 652 | int top; |
| 653 | BN_MONT_CTX *mont = NULL((void *)0); |
| 654 | int numPowers; |
| 655 | unsigned char *powerbufFree = NULL((void *)0); |
| 656 | int powerbufLen = 0; |
| 657 | unsigned char *powerbuf = NULL((void *)0); |
| 658 | BIGNUM tmp, am; |
| 659 | |
| 660 | bn_check_top(a); |
| 661 | bn_check_top(p); |
| 662 | bn_check_top(m); |
| 663 | |
| 664 | if (!BN_is_odd(m)) { |
| 665 | BNerror(BN_R_CALLED_WITH_EVEN_MODULUS)ERR_put_error(3,(0xfff),(102),"/usr/src/lib/libcrypto/bn/bn_exp.c" ,665); |
| 666 | return (0); |
| 667 | } |
| 668 | |
| 669 | top = m->top; |
| 670 | |
| 671 | bits = BN_num_bits(p); |
| 672 | if (bits == 0) { |
| 673 | /* x**0 mod 1 is still zero. */ |
| 674 | if (BN_is_one(m)) { |
| 675 | ret = 1; |
| 676 | BN_zero(rr)(BN_set_word((rr),0)); |
| 677 | } else |
| 678 | ret = BN_one(rr)BN_set_word((rr), 1); |
| 679 | return ret; |
| 680 | } |
| 681 | |
| 682 | BN_CTX_start(ctx); |
| 683 | |
| 684 | /* Allocate a montgomery context if it was not supplied by the caller. |
| 685 | * If this is not done, things will break in the montgomery part. |
| 686 | */ |
| 687 | if (in_mont != NULL((void *)0)) |
| 688 | mont = in_mont; |
| 689 | else { |
| 690 | if ((mont = BN_MONT_CTX_new()) == NULL((void *)0)) |
| 691 | goto err; |
| 692 | if (!BN_MONT_CTX_set(mont, m, ctx)) |
| 693 | goto err; |
| 694 | } |
| 695 | |
| 696 | /* Get the window size to use with size of p. */ |
| 697 | window = BN_window_bits_for_ctime_exponent_size(bits)((bits) > 937 ? 6 : (bits) > 306 ? 5 : (bits) > 89 ? 4 : (bits) > 22 ? 3 : 1); |
| 698 | #if defined(OPENSSL_BN_ASM_MONT51) |
| 699 | if (window == 6 && bits <= 1024) |
| 700 | window = 5; /* ~5% improvement of 2048-bit RSA sign */ |
| 701 | #endif |
| 702 | |
| 703 | /* Allocate a buffer large enough to hold all of the pre-computed |
| 704 | * powers of am, am itself and tmp. |
| 705 | */ |
| 706 | numPowers = 1 << window; |
| 707 | powerbufLen = sizeof(m->d[0]) * (top * numPowers + |
| 708 | ((2*top) > numPowers ? (2*top) : numPowers)); |
| 709 | if ((powerbufFree = calloc(powerbufLen + |
| 710 | MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH( 64 ), 1)) == NULL((void *)0)) |
| 711 | goto err; |
| 712 | powerbuf = MOD_EXP_CTIME_ALIGN(powerbufFree)((unsigned char*)(powerbufFree) + (( 64 ) - (((size_t)(powerbufFree )) & ((( 64 ) - 1))))); |
| 713 | |
| 714 | /* lay down tmp and am right after powers table */ |
| 715 | tmp.d = (BN_ULONGunsigned long *)(powerbuf + sizeof(m->d[0]) * top * numPowers); |
| 716 | am.d = tmp.d + top; |
| 717 | tmp.top = am.top = 0; |
| 718 | tmp.dmax = am.dmax = top; |
| 719 | tmp.neg = am.neg = 0; |
| 720 | tmp.flags = am.flags = BN_FLG_STATIC_DATA0x02; |
| 721 | |
| 722 | /* prepare a^0 in Montgomery domain */ |
| 723 | #if 1 |
| 724 | if (!BN_to_montgomery(&tmp, BN_value_one(), mont, ctx)) |
| 725 | goto err; |
| 726 | #else |
| 727 | tmp.d[0] = (0 - m - >d[0]) & BN_MASK2(0xffffffffffffffffL); /* 2^(top*BN_BITS2) - m */ |
| 728 | for (i = 1; i < top; i++) |
| 729 | tmp.d[i] = (~m->d[i]) & BN_MASK2(0xffffffffffffffffL); |
| 730 | tmp.top = top; |
| 731 | #endif |
| 732 | |
| 733 | /* prepare a^1 in Montgomery domain */ |
| 734 | if (a->neg || BN_ucmp(a, m) >= 0) { |
| 735 | if (!BN_mod_ct(&am, a,m, ctx)BN_div_ct(((void *)0),(&am),(a),(m),(ctx))) |
| 736 | goto err; |
| 737 | if (!BN_to_montgomery(&am, &am, mont, ctx)) |
| 738 | goto err; |
| 739 | } else if (!BN_to_montgomery(&am, a,mont, ctx)) |
| 740 | goto err; |
| 741 | |
| 742 | #if defined(OPENSSL_BN_ASM_MONT51) |
| 743 | /* This optimization uses ideas from http://eprint.iacr.org/2011/239, |
| 744 | * specifically optimization of cache-timing attack countermeasures |
| 745 | * and pre-computation optimization. */ |
| 746 | |
| 747 | /* Dedicated window==4 case improves 512-bit RSA sign by ~15%, but as |
| 748 | * 512-bit RSA is hardly relevant, we omit it to spare size... */ |
| 749 | if (window == 5 && top > 1) { |
| 750 | void bn_mul_mont_gather5(BN_ULONGunsigned long *rp, const BN_ULONGunsigned long *ap, |
| 751 | const void *table, const BN_ULONGunsigned long *np, |
| 752 | const BN_ULONGunsigned long *n0, int num, int power); |
| 753 | void bn_scatter5(const BN_ULONGunsigned long *inp, size_t num, |
| 754 | void *table, size_t power); |
| 755 | void bn_gather5(BN_ULONGunsigned long *out, size_t num, |
| 756 | void *table, size_t power); |
| 757 | |
| 758 | BN_ULONGunsigned long *np = mont->N.d, *n0 = mont->n0; |
| 759 | |
| 760 | /* BN_to_montgomery can contaminate words above .top |
| 761 | * [in BN_DEBUG[_DEBUG] build]... */ |
| 762 | for (i = am.top; i < top; i++) |
| 763 | am.d[i] = 0; |
| 764 | for (i = tmp.top; i < top; i++) |
| 765 | tmp.d[i] = 0; |
| 766 | |
| 767 | bn_scatter5(tmp.d, top, powerbuf, 0); |
| 768 | bn_scatter5(am.d, am.top, powerbuf, 1); |
| 769 | bn_mul_mont(tmp.d, am.d, am.d, np, n0, top); |
| 770 | bn_scatter5(tmp.d, top, powerbuf, 2); |
| 771 | |
| 772 | #if 0 |
| 773 | for (i = 3; i < 32; i++) { |
| 774 | /* Calculate a^i = a^(i-1) * a */ |
| 775 | bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, |
| 776 | n0, top, i - 1); |
| 777 | bn_scatter5(tmp.d, top, powerbuf, i); |
| 778 | } |
| 779 | #else |
| 780 | /* same as above, but uses squaring for 1/2 of operations */ |
| 781 | for (i = 4; i < 32; i*=2) { |
| 782 | bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); |
| 783 | bn_scatter5(tmp.d, top, powerbuf, i); |
| 784 | } |
| 785 | for (i = 3; i < 8; i += 2) { |
| 786 | int j; |
| 787 | bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, |
| 788 | n0, top, i - 1); |
| 789 | bn_scatter5(tmp.d, top, powerbuf, i); |
| 790 | for (j = 2 * i; j < 32; j *= 2) { |
| 791 | bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); |
| 792 | bn_scatter5(tmp.d, top, powerbuf, j); |
| 793 | } |
| 794 | } |
| 795 | for (; i < 16; i += 2) { |
| 796 | bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, |
| 797 | n0, top, i - 1); |
| 798 | bn_scatter5(tmp.d, top, powerbuf, i); |
| 799 | bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); |
| 800 | bn_scatter5(tmp.d, top, powerbuf, 2*i); |
| 801 | } |
| 802 | for (; i < 32; i += 2) { |
| 803 | bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, |
| 804 | n0, top, i - 1); |
| 805 | bn_scatter5(tmp.d, top, powerbuf, i); |
| 806 | } |
| 807 | #endif |
| 808 | bits--; |
| 809 | for (wvalue = 0, i = bits % 5; i >= 0; i--, bits--) |
| 810 | wvalue = (wvalue << 1) + BN_is_bit_set(p, bits); |
| 811 | bn_gather5(tmp.d, top, powerbuf, wvalue); |
| 812 | |
| 813 | /* Scan the exponent one window at a time starting from the most |
| 814 | * significant bits. |
| 815 | */ |
| 816 | while (bits >= 0) { |
| 817 | for (wvalue = 0, i = 0; i < 5; i++, bits--) |
| 818 | wvalue = (wvalue << 1) + BN_is_bit_set(p, bits); |
| 819 | |
| 820 | bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); |
| 821 | bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); |
| 822 | bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); |
| 823 | bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); |
| 824 | bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); |
| 825 | bn_mul_mont_gather5(tmp.d, tmp.d, powerbuf, np, n0, top, wvalue); |
| 826 | } |
| 827 | |
| 828 | tmp.top = top; |
| 829 | bn_correct_top(&tmp){ unsigned long *ftl; int tmp_top = (&tmp)->top; if (tmp_top > 0) { for (ftl= &((&tmp)->d[tmp_top-1]); tmp_top > 0; tmp_top--) if (*(ftl--)) break; (&tmp)->top = tmp_top; } ; }; |
| 830 | } else |
| 831 | #endif |
| 832 | { |
| 833 | if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 0, |
| 834 | window)) |
| 835 | goto err; |
| 836 | if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&am, top, powerbuf, 1, |
| 837 | window)) |
| 838 | goto err; |
| 839 | |
| 840 | /* If the window size is greater than 1, then calculate |
| 841 | * val[i=2..2^winsize-1]. Powers are computed as a*a^(i-1) |
| 842 | * (even powers could instead be computed as (a^(i/2))^2 |
| 843 | * to use the slight performance advantage of sqr over mul). |
| 844 | */ |
| 845 | if (window > 1) { |
| 846 | if (!BN_mod_mul_montgomery(&tmp, &am, &am, mont, ctx)) |
| 847 | goto err; |
| 848 | if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, |
| 849 | 2, window)) |
| 850 | goto err; |
| 851 | for (i = 3; i < numPowers; i++) { |
| 852 | /* Calculate a^i = a^(i-1) * a */ |
| 853 | if (!BN_mod_mul_montgomery(&tmp, &am, &tmp, |
| 854 | mont, ctx)) |
| 855 | goto err; |
| 856 | if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, |
| 857 | powerbuf, i, window)) |
| 858 | goto err; |
| 859 | } |
| 860 | } |
| 861 | |
| 862 | bits--; |
| 863 | for (wvalue = 0, i = bits % window; i >= 0; i--, bits--) |
| 864 | wvalue = (wvalue << 1) + BN_is_bit_set(p, bits); |
| 865 | if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&tmp, top, powerbuf, |
| 866 | wvalue, window)) |
| 867 | goto err; |
| 868 | |
| 869 | /* Scan the exponent one window at a time starting from the most |
| 870 | * significant bits. |
| 871 | */ |
| 872 | while (bits >= 0) { |
| 873 | wvalue = 0; /* The 'value' of the window */ |
| 874 | |
| 875 | /* Scan the window, squaring the result as we go */ |
| 876 | for (i = 0; i < window; i++, bits--) { |
| 877 | if (!BN_mod_mul_montgomery(&tmp, &tmp, &tmp, |
| 878 | mont, ctx)) |
| 879 | goto err; |
| 880 | wvalue = (wvalue << 1) + BN_is_bit_set(p, bits); |
| 881 | } |
| 882 | |
| 883 | /* Fetch the appropriate pre-computed value from the pre-buf */ |
| 884 | if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&am, top, powerbuf, |
| 885 | wvalue, window)) |
| 886 | goto err; |
| 887 | |
| 888 | /* Multiply the result into the intermediate result */ |
| 889 | if (!BN_mod_mul_montgomery(&tmp, &tmp, &am, mont, ctx)) |
| 890 | goto err; |
| 891 | } |
| 892 | } |
| 893 | |
| 894 | /* Convert the final result from montgomery to standard format */ |
| 895 | if (!BN_from_montgomery(rr, &tmp, mont, ctx)) |
| 896 | goto err; |
| 897 | ret = 1; |
| 898 | |
| 899 | err: |
| 900 | if ((in_mont == NULL((void *)0)) && (mont != NULL((void *)0))) |
| 901 | BN_MONT_CTX_free(mont); |
| 902 | freezero(powerbufFree, powerbufLen + MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH( 64 )); |
| 903 | BN_CTX_end(ctx); |
| 904 | return (ret); |
| 905 | } |
| 906 | |
| 907 | int |
| 908 | BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONGunsigned long a, const BIGNUM *p, const BIGNUM *m, |
| 909 | BN_CTX *ctx, BN_MONT_CTX *in_mont) |
| 910 | { |
| 911 | BN_MONT_CTX *mont = NULL((void *)0); |
| 912 | int b, bits, ret = 0; |
| 913 | int r_is_one; |
| 914 | BN_ULONGunsigned long w, next_w; |
| 915 | BIGNUM *d, *r, *t; |
| 916 | BIGNUM *swap_tmp; |
| 917 | |
| 918 | #define BN_MOD_MUL_WORD(r, w, m)(BN_mul_word(r, (w)) && ( (BN_div_ct(((void *)0),(t), (r),(m),(ctx)) && (swap_tmp = r, r = t, t = swap_tmp, 1)))) \ |
| 919 | (BN_mul_word(r, (w)) && \ |
| 920 | (/* BN_ucmp(r, (m)) < 0 ? 1 :*/ \ |
| 921 | (BN_mod_ct(t, r, m, ctx)BN_div_ct(((void *)0),(t),(r),(m),(ctx)) && (swap_tmp = r, r = t, t = swap_tmp, 1)))) |
| 922 | /* BN_MOD_MUL_WORD is only used with 'w' large, |
| 923 | * so the BN_ucmp test is probably more overhead |
| 924 | * than always using BN_mod (which uses BN_copy if |
| 925 | * a similar test returns true). */ |
| 926 | /* We can use BN_mod and do not need BN_nnmod because our |
| 927 | * accumulator is never negative (the result of BN_mod does |
| 928 | * not depend on the sign of the modulus). |
| 929 | */ |
| 930 | #define BN_TO_MONTGOMERY_WORD(r, w, mont)(BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont) , ctx)) \ |
| 931 | (BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont), ctx)) |
| 932 | |
| 933 | if (BN_get_flags(p, BN_FLG_CONSTTIME0x04) != 0) { |
| 934 | /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ |
| 935 | BNerror(ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED)ERR_put_error(3,(0xfff),((2|64)),"/usr/src/lib/libcrypto/bn/bn_exp.c" ,935); |
| 936 | return -1; |
| 937 | } |
| 938 | |
| 939 | bn_check_top(p); |
| 940 | bn_check_top(m); |
| 941 | |
| 942 | if (!BN_is_odd(m)) { |
| 943 | BNerror(BN_R_CALLED_WITH_EVEN_MODULUS)ERR_put_error(3,(0xfff),(102),"/usr/src/lib/libcrypto/bn/bn_exp.c" ,943); |
| 944 | return (0); |
| 945 | } |
| 946 | if (m->top == 1) |
| 947 | a %= m->d[0]; /* make sure that 'a' is reduced */ |
| 948 | |
| 949 | bits = BN_num_bits(p); |
| 950 | if (bits == 0) { |
| 951 | /* x**0 mod 1 is still zero. */ |
| 952 | if (BN_is_one(m)) { |
| 953 | ret = 1; |
| 954 | BN_zero(rr)(BN_set_word((rr),0)); |
| 955 | } else |
| 956 | ret = BN_one(rr)BN_set_word((rr), 1); |
| 957 | return ret; |
| 958 | } |
| 959 | if (a == 0) { |
| 960 | BN_zero(rr)(BN_set_word((rr),0)); |
| 961 | ret = 1; |
| 962 | return ret; |
| 963 | } |
| 964 | |
| 965 | BN_CTX_start(ctx); |
| 966 | if ((d = BN_CTX_get(ctx)) == NULL((void *)0)) |
| 967 | goto err; |
| 968 | if ((r = BN_CTX_get(ctx)) == NULL((void *)0)) |
| 969 | goto err; |
| 970 | if ((t = BN_CTX_get(ctx)) == NULL((void *)0)) |
| 971 | goto err; |
| 972 | |
| 973 | if (in_mont != NULL((void *)0)) |
| 974 | mont = in_mont; |
| 975 | else { |
| 976 | if ((mont = BN_MONT_CTX_new()) == NULL((void *)0)) |
| 977 | goto err; |
| 978 | if (!BN_MONT_CTX_set(mont, m, ctx)) |
| 979 | goto err; |
| 980 | } |
| 981 | |
| 982 | r_is_one = 1; /* except for Montgomery factor */ |
| 983 | |
| 984 | /* bits-1 >= 0 */ |
| 985 | |
| 986 | /* The result is accumulated in the product r*w. */ |
| 987 | w = a; /* bit 'bits-1' of 'p' is always set */ |
| 988 | for (b = bits - 2; b >= 0; b--) { |
| 989 | /* First, square r*w. */ |
| 990 | next_w = w * w; |
| 991 | if ((next_w / w) != w) /* overflow */ |
| 992 | { |
| 993 | if (r_is_one) { |
| 994 | if (!BN_TO_MONTGOMERY_WORD(r, w, mont)(BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont) , ctx))) |
| 995 | goto err; |
| 996 | r_is_one = 0; |
| 997 | } else { |
| 998 | if (!BN_MOD_MUL_WORD(r, w, m)(BN_mul_word(r, (w)) && ( (BN_div_ct(((void *)0),(t), (r),(m),(ctx)) && (swap_tmp = r, r = t, t = swap_tmp, 1))))) |
| 999 | goto err; |
| 1000 | } |
| 1001 | next_w = 1; |
| 1002 | } |
| 1003 | w = next_w; |
| 1004 | if (!r_is_one) { |
| 1005 | if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) |
| 1006 | goto err; |
| 1007 | } |
| 1008 | |
| 1009 | /* Second, multiply r*w by 'a' if exponent bit is set. */ |
| 1010 | if (BN_is_bit_set(p, b)) { |
| 1011 | next_w = w * a; |
| 1012 | if ((next_w / a) != w) /* overflow */ |
| 1013 | { |
| 1014 | if (r_is_one) { |
| 1015 | if (!BN_TO_MONTGOMERY_WORD(r, w, mont)(BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont) , ctx))) |
| 1016 | goto err; |
| 1017 | r_is_one = 0; |
| 1018 | } else { |
| 1019 | if (!BN_MOD_MUL_WORD(r, w, m)(BN_mul_word(r, (w)) && ( (BN_div_ct(((void *)0),(t), (r),(m),(ctx)) && (swap_tmp = r, r = t, t = swap_tmp, 1))))) |
| 1020 | goto err; |
| 1021 | } |
| 1022 | next_w = a; |
| 1023 | } |
| 1024 | w = next_w; |
| 1025 | } |
| 1026 | } |
| 1027 | |
| 1028 | /* Finally, set r:=r*w. */ |
| 1029 | if (w != 1) { |
| 1030 | if (r_is_one) { |
| 1031 | if (!BN_TO_MONTGOMERY_WORD(r, w, mont)(BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont) , ctx))) |
| 1032 | goto err; |
| 1033 | r_is_one = 0; |
| 1034 | } else { |
| 1035 | if (!BN_MOD_MUL_WORD(r, w, m)(BN_mul_word(r, (w)) && ( (BN_div_ct(((void *)0),(t), (r),(m),(ctx)) && (swap_tmp = r, r = t, t = swap_tmp, 1))))) |
| 1036 | goto err; |
| 1037 | } |
| 1038 | } |
| 1039 | |
| 1040 | if (r_is_one) /* can happen only if a == 1*/ |
| 1041 | { |
| 1042 | if (!BN_one(rr)BN_set_word((rr), 1)) |
| 1043 | goto err; |
| 1044 | } else { |
| 1045 | if (!BN_from_montgomery(rr, r, mont, ctx)) |
| 1046 | goto err; |
| 1047 | } |
| 1048 | ret = 1; |
| 1049 | |
| 1050 | err: |
| 1051 | if ((in_mont == NULL((void *)0)) && (mont != NULL((void *)0))) |
| 1052 | BN_MONT_CTX_free(mont); |
| 1053 | BN_CTX_end(ctx); |
| 1054 | bn_check_top(rr); |
| 1055 | return (ret); |
| 1056 | } |
| 1057 | |
| 1058 | |
| 1059 | /* The old fallback, simple version :-) */ |
| 1060 | int |
| 1061 | BN_mod_exp_simple(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, |
| 1062 | BN_CTX *ctx) |
| 1063 | { |
| 1064 | int i, j, bits, ret = 0, wstart, wend, window, wvalue; |
| 1065 | int start = 1; |
| 1066 | BIGNUM *d; |
| 1067 | /* Table of variables obtained from 'ctx' */ |
| 1068 | BIGNUM *val[TABLE_SIZE32]; |
| 1069 | |
| 1070 | if (BN_get_flags(p, BN_FLG_CONSTTIME0x04) != 0) { |
| 1071 | /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ |
| 1072 | BNerror(ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED)ERR_put_error(3,(0xfff),((2|64)),"/usr/src/lib/libcrypto/bn/bn_exp.c" ,1072); |
| 1073 | return -1; |
| 1074 | } |
| 1075 | |
| 1076 | bits = BN_num_bits(p); |
| 1077 | if (bits == 0) { |
| 1078 | /* x**0 mod 1 is still zero. */ |
| 1079 | if (BN_is_one(m)) { |
| 1080 | ret = 1; |
| 1081 | BN_zero(r)(BN_set_word((r),0)); |
| 1082 | } else |
| 1083 | ret = BN_one(r)BN_set_word((r), 1); |
| 1084 | return ret; |
| 1085 | } |
| 1086 | |
| 1087 | BN_CTX_start(ctx); |
| 1088 | if ((d = BN_CTX_get(ctx)) == NULL((void *)0)) |
| 1089 | goto err; |
| 1090 | if ((val[0] = BN_CTX_get(ctx)) == NULL((void *)0)) |
| 1091 | goto err; |
| 1092 | |
| 1093 | if (!BN_nnmod(val[0],a,m,ctx)) |
| 1094 | goto err; /* 1 */ |
| 1095 | if (BN_is_zero(val[0])) { |
| 1096 | BN_zero(r)(BN_set_word((r),0)); |
| 1097 | ret = 1; |
| 1098 | goto err; |
| 1099 | } |
| 1100 | |
| 1101 | window = BN_window_bits_for_exponent_size(bits)((bits) > 671 ? 6 : (bits) > 239 ? 5 : (bits) > 79 ? 4 : (bits) > 23 ? 3 : 1); |
| 1102 | if (window > 1) { |
| 1103 | if (!BN_mod_mul(d, val[0], val[0], m, ctx)) |
| 1104 | goto err; /* 2 */ |
| 1105 | j = 1 << (window - 1); |
| 1106 | for (i = 1; i < j; i++) { |
| 1107 | if (((val[i] = BN_CTX_get(ctx)) == NULL((void *)0)) || |
| 1108 | !BN_mod_mul(val[i], val[i - 1], d,m, ctx)) |
| 1109 | goto err; |
| 1110 | } |
| 1111 | } |
| 1112 | |
| 1113 | start = 1; /* This is used to avoid multiplication etc |
| 1114 | * when there is only the value '1' in the |
| 1115 | * buffer. */ |
| 1116 | wvalue = 0; /* The 'value' of the window */ |
| 1117 | wstart = bits - 1; /* The top bit of the window */ |
| 1118 | wend = 0; /* The bottom bit of the window */ |
| 1119 | |
| 1120 | if (!BN_one(r)BN_set_word((r), 1)) |
| 1121 | goto err; |
| 1122 | |
| 1123 | for (;;) { |
| 1124 | if (BN_is_bit_set(p, wstart) == 0) { |
| 1125 | if (!start) |
| 1126 | if (!BN_mod_mul(r, r, r, m, ctx)) |
| 1127 | goto err; |
| 1128 | if (wstart == 0) |
| 1129 | break; |
| 1130 | wstart--; |
| 1131 | continue; |
| 1132 | } |
| 1133 | /* We now have wstart on a 'set' bit, we now need to work out |
| 1134 | * how bit a window to do. To do this we need to scan |
| 1135 | * forward until the last set bit before the end of the |
| 1136 | * window */ |
| 1137 | j = wstart; |
| 1138 | wvalue = 1; |
| 1139 | wend = 0; |
| 1140 | for (i = 1; i < window; i++) { |
| 1141 | if (wstart - i < 0) |
| 1142 | break; |
| 1143 | if (BN_is_bit_set(p, wstart - i)) { |
| 1144 | wvalue <<= (i - wend); |
| 1145 | wvalue |= 1; |
| 1146 | wend = i; |
| 1147 | } |
| 1148 | } |
| 1149 | |
| 1150 | /* wend is the size of the current window */ |
| 1151 | j = wend + 1; |
| 1152 | /* add the 'bytes above' */ |
| 1153 | if (!start) |
| 1154 | for (i = 0; i < j; i++) { |
| 1155 | if (!BN_mod_mul(r, r, r, m, ctx)) |
| 1156 | goto err; |
| 1157 | } |
| 1158 | |
| 1159 | /* wvalue will be an odd number < 2^window */ |
| 1160 | if (!BN_mod_mul(r, r, val[wvalue >> 1], m, ctx)) |
| 1161 | goto err; |
| 1162 | |
| 1163 | /* move the 'window' down further */ |
| 1164 | wstart -= wend + 1; |
| 1165 | wvalue = 0; |
| 1166 | start = 0; |
| 1167 | if (wstart < 0) |
| 1168 | break; |
| 1169 | } |
| 1170 | ret = 1; |
| 1171 | |
| 1172 | err: |
| 1173 | BN_CTX_end(ctx); |
| 1174 | bn_check_top(r); |
| 1175 | return (ret); |
| 1176 | } |