diff options
Diffstat (limited to 'thirdparty/openssl/crypto/bn/bn_exp.c')
| -rw-r--r-- | thirdparty/openssl/crypto/bn/bn_exp.c | 1468 |
1 files changed, 0 insertions, 1468 deletions
diff --git a/thirdparty/openssl/crypto/bn/bn_exp.c b/thirdparty/openssl/crypto/bn/bn_exp.c deleted file mode 100644 index c4b63e44ba..0000000000 --- a/thirdparty/openssl/crypto/bn/bn_exp.c +++ /dev/null @@ -1,1468 +0,0 @@ -/* crypto/bn/bn_exp.c */ -/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) - * All rights reserved. - * - * This package is an SSL implementation written - * by Eric Young (eay@cryptsoft.com). - * The implementation was written so as to conform with Netscapes SSL. - * - * This library is free for commercial and non-commercial use as long as - * the following conditions are aheared to. The following conditions - * apply to all code found in this distribution, be it the RC4, RSA, - * lhash, DES, etc., code; not just the SSL code. The SSL documentation - * included with this distribution is covered by the same copyright terms - * except that the holder is Tim Hudson (tjh@cryptsoft.com). - * - * Copyright remains Eric Young's, and as such any Copyright notices in - * the code are not to be removed. - * If this package is used in a product, Eric Young should be given attribution - * as the author of the parts of the library used. - * This can be in the form of a textual message at program startup or - * in documentation (online or textual) provided with the package. - * - * Redistribution and use in source and binary forms, with or without - * modification, are permitted provided that the following conditions - * are met: - * 1. Redistributions of source code must retain the copyright - * notice, this list of conditions and the following disclaimer. - * 2. Redistributions in binary form must reproduce the above copyright - * notice, this list of conditions and the following disclaimer in the - * documentation and/or other materials provided with the distribution. - * 3. All advertising materials mentioning features or use of this software - * must display the following acknowledgement: - * "This product includes cryptographic software written by - * Eric Young (eay@cryptsoft.com)" - * The word 'cryptographic' can be left out if the rouines from the library - * being used are not cryptographic related :-). - * 4. If you include any Windows specific code (or a derivative thereof) from - * the apps directory (application code) you must include an acknowledgement: - * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" - * - * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND - * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE - * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE - * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE - * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL - * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS - * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) - * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT - * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY - * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF - * SUCH DAMAGE. - * - * The licence and distribution terms for any publically available version or - * derivative of this code cannot be changed. i.e. this code cannot simply be - * copied and put under another distribution licence - * [including the GNU Public Licence.] - */ -/* ==================================================================== - * Copyright (c) 1998-2005 The OpenSSL Project. All rights reserved. - * - * Redistribution and use in source and binary forms, with or without - * modification, are permitted provided that the following conditions - * are met: - * - * 1. Redistributions of source code must retain the above copyright - * notice, this list of conditions and the following disclaimer. - * - * 2. Redistributions in binary form must reproduce the above copyright - * notice, this list of conditions and the following disclaimer in - * the documentation and/or other materials provided with the - * distribution. - * - * 3. All advertising materials mentioning features or use of this - * software must display the following acknowledgment: - * "This product includes software developed by the OpenSSL Project - * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" - * - * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to - * endorse or promote products derived from this software without - * prior written permission. For written permission, please contact - * openssl-core@openssl.org. - * - * 5. Products derived from this software may not be called "OpenSSL" - * nor may "OpenSSL" appear in their names without prior written - * permission of the OpenSSL Project. - * - * 6. Redistributions of any form whatsoever must retain the following - * acknowledgment: - * "This product includes software developed by the OpenSSL Project - * for use in the OpenSSL Toolkit (http://www.openssl.org/)" - * - * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY - * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE - * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR - * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR - * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, - * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT - * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; - * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) - * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, - * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) - * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED - * OF THE POSSIBILITY OF SUCH DAMAGE. - * ==================================================================== - * - * This product includes cryptographic software written by Eric Young - * (eay@cryptsoft.com). This product includes software written by Tim - * Hudson (tjh@cryptsoft.com). - * - */ - -#include "cryptlib.h" -#include "constant_time_locl.h" -#include "bn_lcl.h" - -#include <stdlib.h> -#ifdef _WIN32 -# include <malloc.h> -# ifndef alloca -# define alloca _alloca -# endif -#elif defined(__GNUC__) -# ifndef alloca -# define alloca(s) __builtin_alloca((s)) -# endif -#elif defined(__sun) -# include <alloca.h> -#endif - -#include "rsaz_exp.h" - -#undef SPARC_T4_MONT -#if defined(OPENSSL_BN_ASM_MONT) && (defined(__sparc__) || defined(__sparc)) -# include "sparc_arch.h" -extern unsigned int OPENSSL_sparcv9cap_P[]; -# define SPARC_T4_MONT -#endif - -/* maximum precomputation table size for *variable* sliding windows */ -#define TABLE_SIZE 32 - -/* this one works - simple but works */ -int BN_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx) -{ - int i, bits, ret = 0; - BIGNUM *v, *rr; - - if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0 - || BN_get_flags(a, BN_FLG_CONSTTIME) != 0) { - /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ - BNerr(BN_F_BN_EXP, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED); - return 0; - } - - BN_CTX_start(ctx); - if ((r == a) || (r == p)) - rr = BN_CTX_get(ctx); - else - rr = r; - v = BN_CTX_get(ctx); - if (rr == NULL || v == NULL) - goto err; - - if (BN_copy(v, a) == NULL) - goto err; - bits = BN_num_bits(p); - - if (BN_is_odd(p)) { - if (BN_copy(rr, a) == NULL) - goto err; - } else { - if (!BN_one(rr)) - goto err; - } - - for (i = 1; i < bits; i++) { - if (!BN_sqr(v, v, ctx)) - goto err; - if (BN_is_bit_set(p, i)) { - if (!BN_mul(rr, rr, v, ctx)) - goto err; - } - } - if (r != rr && BN_copy(r, rr) == NULL) - goto err; - - ret = 1; - err: - BN_CTX_end(ctx); - bn_check_top(r); - return (ret); -} - -int BN_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, - BN_CTX *ctx) -{ - int ret; - - bn_check_top(a); - bn_check_top(p); - bn_check_top(m); - - /*- - * For even modulus m = 2^k*m_odd, it might make sense to compute - * a^p mod m_odd and a^p mod 2^k separately (with Montgomery - * exponentiation for the odd part), using appropriate exponent - * reductions, and combine the results using the CRT. - * - * For now, we use Montgomery only if the modulus is odd; otherwise, - * exponentiation using the reciprocal-based quick remaindering - * algorithm is used. - * - * (Timing obtained with expspeed.c [computations a^p mod m - * where a, p, m are of the same length: 256, 512, 1024, 2048, - * 4096, 8192 bits], compared to the running time of the - * standard algorithm: - * - * BN_mod_exp_mont 33 .. 40 % [AMD K6-2, Linux, debug configuration] - * 55 .. 77 % [UltraSparc processor, but - * debug-solaris-sparcv8-gcc conf.] - * - * BN_mod_exp_recp 50 .. 70 % [AMD K6-2, Linux, debug configuration] - * 62 .. 118 % [UltraSparc, debug-solaris-sparcv8-gcc] - * - * On the Sparc, BN_mod_exp_recp was faster than BN_mod_exp_mont - * at 2048 and more bits, but at 512 and 1024 bits, it was - * slower even than the standard algorithm! - * - * "Real" timings [linux-elf, solaris-sparcv9-gcc configurations] - * should be obtained when the new Montgomery reduction code - * has been integrated into OpenSSL.) - */ - -#define MONT_MUL_MOD -#define MONT_EXP_WORD -#define RECP_MUL_MOD - -#ifdef MONT_MUL_MOD - /* - * I have finally been able to take out this pre-condition of the top bit - * being set. It was caused by an error in BN_div with negatives. There - * was also another problem when for a^b%m a >= m. eay 07-May-97 - */ - /* if ((m->d[m->top-1]&BN_TBIT) && BN_is_odd(m)) */ - - if (BN_is_odd(m)) { -# ifdef MONT_EXP_WORD - if (a->top == 1 && !a->neg - && (BN_get_flags(p, BN_FLG_CONSTTIME) == 0) - && (BN_get_flags(a, BN_FLG_CONSTTIME) == 0) - && (BN_get_flags(m, BN_FLG_CONSTTIME) == 0)) { - BN_ULONG A = a->d[0]; - ret = BN_mod_exp_mont_word(r, A, p, m, ctx, NULL); - } else -# endif - ret = BN_mod_exp_mont(r, a, p, m, ctx, NULL); - } else -#endif -#ifdef RECP_MUL_MOD - { - ret = BN_mod_exp_recp(r, a, p, m, ctx); - } -#else - { - ret = BN_mod_exp_simple(r, a, p, m, ctx); - } -#endif - - bn_check_top(r); - return (ret); -} - -int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, - const BIGNUM *m, BN_CTX *ctx) -{ - int i, j, bits, ret = 0, wstart, wend, window, wvalue; - int start = 1; - BIGNUM *aa; - /* Table of variables obtained from 'ctx' */ - BIGNUM *val[TABLE_SIZE]; - BN_RECP_CTX recp; - - if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0 - || BN_get_flags(a, BN_FLG_CONSTTIME) != 0 - || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) { - /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ - BNerr(BN_F_BN_MOD_EXP_RECP, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED); - return 0; - } - - bits = BN_num_bits(p); - if (bits == 0) { - /* x**0 mod 1 is still zero. */ - if (BN_is_one(m)) { - ret = 1; - BN_zero(r); - } else { - ret = BN_one(r); - } - return ret; - } - - BN_CTX_start(ctx); - aa = BN_CTX_get(ctx); - val[0] = BN_CTX_get(ctx); - if (!aa || !val[0]) - goto err; - - BN_RECP_CTX_init(&recp); - if (m->neg) { - /* ignore sign of 'm' */ - if (!BN_copy(aa, m)) - goto err; - aa->neg = 0; - if (BN_RECP_CTX_set(&recp, aa, ctx) <= 0) - goto err; - } else { - if (BN_RECP_CTX_set(&recp, m, ctx) <= 0) - goto err; - } - - if (!BN_nnmod(val[0], a, m, ctx)) - goto err; /* 1 */ - if (BN_is_zero(val[0])) { - BN_zero(r); - ret = 1; - goto err; - } - - window = BN_window_bits_for_exponent_size(bits); - if (window > 1) { - if (!BN_mod_mul_reciprocal(aa, val[0], val[0], &recp, ctx)) - goto err; /* 2 */ - j = 1 << (window - 1); - for (i = 1; i < j; i++) { - if (((val[i] = BN_CTX_get(ctx)) == NULL) || - !BN_mod_mul_reciprocal(val[i], val[i - 1], aa, &recp, ctx)) - goto err; - } - } - - start = 1; /* This is used to avoid multiplication etc - * when there is only the value '1' in the - * buffer. */ - wvalue = 0; /* The 'value' of the window */ - wstart = bits - 1; /* The top bit of the window */ - wend = 0; /* The bottom bit of the window */ - - if (!BN_one(r)) - goto err; - - for (;;) { - if (BN_is_bit_set(p, wstart) == 0) { - if (!start) - if (!BN_mod_mul_reciprocal(r, r, r, &recp, ctx)) - goto err; - if (wstart == 0) - break; - wstart--; - continue; - } - /* - * We now have wstart on a 'set' bit, we now need to work out how bit - * a window to do. To do this we need to scan forward until the last - * set bit before the end of the window - */ - j = wstart; - wvalue = 1; - wend = 0; - for (i = 1; i < window; i++) { - if (wstart - i < 0) - break; - if (BN_is_bit_set(p, wstart - i)) { - wvalue <<= (i - wend); - wvalue |= 1; - wend = i; - } - } - - /* wend is the size of the current window */ - j = wend + 1; - /* add the 'bytes above' */ - if (!start) - for (i = 0; i < j; i++) { - if (!BN_mod_mul_reciprocal(r, r, r, &recp, ctx)) - goto err; - } - - /* wvalue will be an odd number < 2^window */ - if (!BN_mod_mul_reciprocal(r, r, val[wvalue >> 1], &recp, ctx)) - goto err; - - /* move the 'window' down further */ - wstart -= wend + 1; - wvalue = 0; - start = 0; - if (wstart < 0) - break; - } - ret = 1; - err: - BN_CTX_end(ctx); - BN_RECP_CTX_free(&recp); - bn_check_top(r); - return (ret); -} - -int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, - const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont) -{ - int i, j, bits, ret = 0, wstart, wend, window, wvalue; - int start = 1; - BIGNUM *d, *r; - const BIGNUM *aa; - /* Table of variables obtained from 'ctx' */ - BIGNUM *val[TABLE_SIZE]; - BN_MONT_CTX *mont = NULL; - - if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0 - || BN_get_flags(a, BN_FLG_CONSTTIME) != 0 - || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) { - return BN_mod_exp_mont_consttime(rr, a, p, m, ctx, in_mont); - } - - bn_check_top(a); - bn_check_top(p); - bn_check_top(m); - - if (!BN_is_odd(m)) { - BNerr(BN_F_BN_MOD_EXP_MONT, BN_R_CALLED_WITH_EVEN_MODULUS); - return (0); - } - bits = BN_num_bits(p); - if (bits == 0) { - /* x**0 mod 1 is still zero. */ - if (BN_is_one(m)) { - ret = 1; - BN_zero(rr); - } else { - ret = BN_one(rr); - } - return ret; - } - - BN_CTX_start(ctx); - d = BN_CTX_get(ctx); - r = BN_CTX_get(ctx); - val[0] = BN_CTX_get(ctx); - if (!d || !r || !val[0]) - goto err; - - /* - * If this is not done, things will break in the montgomery part - */ - - if (in_mont != NULL) - mont = in_mont; - else { - if ((mont = BN_MONT_CTX_new()) == NULL) - goto err; - if (!BN_MONT_CTX_set(mont, m, ctx)) - goto err; - } - - if (a->neg || BN_ucmp(a, m) >= 0) { - if (!BN_nnmod(val[0], a, m, ctx)) - goto err; - aa = val[0]; - } else - aa = a; - if (BN_is_zero(aa)) { - BN_zero(rr); - ret = 1; - goto err; - } - if (!BN_to_montgomery(val[0], aa, mont, ctx)) - goto err; /* 1 */ - - window = BN_window_bits_for_exponent_size(bits); - if (window > 1) { - if (!BN_mod_mul_montgomery(d, val[0], val[0], mont, ctx)) - goto err; /* 2 */ - j = 1 << (window - 1); - for (i = 1; i < j; i++) { - if (((val[i] = BN_CTX_get(ctx)) == NULL) || - !BN_mod_mul_montgomery(val[i], val[i - 1], d, mont, ctx)) - goto err; - } - } - - start = 1; /* This is used to avoid multiplication etc - * when there is only the value '1' in the - * buffer. */ - wvalue = 0; /* The 'value' of the window */ - wstart = bits - 1; /* The top bit of the window */ - wend = 0; /* The bottom bit of the window */ - -#if 1 /* by Shay Gueron's suggestion */ - j = m->top; /* borrow j */ - if (m->d[j - 1] & (((BN_ULONG)1) << (BN_BITS2 - 1))) { - if (bn_wexpand(r, j) == NULL) - goto err; - /* 2^(top*BN_BITS2) - m */ - r->d[0] = (0 - m->d[0]) & BN_MASK2; - for (i = 1; i < j; i++) - r->d[i] = (~m->d[i]) & BN_MASK2; - r->top = j; - /* - * Upper words will be zero if the corresponding words of 'm' were - * 0xfff[...], so decrement r->top accordingly. - */ - bn_correct_top(r); - } else -#endif - if (!BN_to_montgomery(r, BN_value_one(), mont, ctx)) - goto err; - for (;;) { - if (BN_is_bit_set(p, wstart) == 0) { - if (!start) { - if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) - goto err; - } - if (wstart == 0) - break; - wstart--; - continue; - } - /* - * We now have wstart on a 'set' bit, we now need to work out how bit - * a window to do. To do this we need to scan forward until the last - * set bit before the end of the window - */ - j = wstart; - wvalue = 1; - wend = 0; - for (i = 1; i < window; i++) { - if (wstart - i < 0) - break; - if (BN_is_bit_set(p, wstart - i)) { - wvalue <<= (i - wend); - wvalue |= 1; - wend = i; - } - } - - /* wend is the size of the current window */ - j = wend + 1; - /* add the 'bytes above' */ - if (!start) - for (i = 0; i < j; i++) { - if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) - goto err; - } - - /* wvalue will be an odd number < 2^window */ - if (!BN_mod_mul_montgomery(r, r, val[wvalue >> 1], mont, ctx)) - goto err; - - /* move the 'window' down further */ - wstart -= wend + 1; - wvalue = 0; - start = 0; - if (wstart < 0) - break; - } -#if defined(SPARC_T4_MONT) - if (OPENSSL_sparcv9cap_P[0] & (SPARCV9_VIS3 | SPARCV9_PREFER_FPU)) { - j = mont->N.top; /* borrow j */ - val[0]->d[0] = 1; /* borrow val[0] */ - for (i = 1; i < j; i++) - val[0]->d[i] = 0; - val[0]->top = j; - if (!BN_mod_mul_montgomery(rr, r, val[0], mont, ctx)) - goto err; - } else -#endif - if (!BN_from_montgomery(rr, r, mont, ctx)) - goto err; - ret = 1; - err: - if ((in_mont == NULL) && (mont != NULL)) - BN_MONT_CTX_free(mont); - BN_CTX_end(ctx); - bn_check_top(rr); - return (ret); -} - -#if defined(SPARC_T4_MONT) -static BN_ULONG bn_get_bits(const BIGNUM *a, int bitpos) -{ - BN_ULONG ret = 0; - int wordpos; - - wordpos = bitpos / BN_BITS2; - bitpos %= BN_BITS2; - if (wordpos >= 0 && wordpos < a->top) { - ret = a->d[wordpos] & BN_MASK2; - if (bitpos) { - ret >>= bitpos; - if (++wordpos < a->top) - ret |= a->d[wordpos] << (BN_BITS2 - bitpos); - } - } - - return ret & BN_MASK2; -} -#endif - -/* - * BN_mod_exp_mont_consttime() stores the precomputed powers in a specific - * layout so that accessing any of these table values shows the same access - * pattern as far as cache lines are concerned. The following functions are - * used to transfer a BIGNUM from/to that table. - */ - -static int MOD_EXP_CTIME_COPY_TO_PREBUF(const BIGNUM *b, int top, - unsigned char *buf, int idx, - int window) -{ - int i, j; - int width = 1 << window; - BN_ULONG *table = (BN_ULONG *)buf; - - if (top > b->top) - top = b->top; /* this works because 'buf' is explicitly - * zeroed */ - for (i = 0, j = idx; i < top; i++, j += width) { - table[j] = b->d[i]; - } - - return 1; -} - -static int MOD_EXP_CTIME_COPY_FROM_PREBUF(BIGNUM *b, int top, - unsigned char *buf, int idx, - int window) -{ - int i, j; - int width = 1 << window; - volatile BN_ULONG *table = (volatile BN_ULONG *)buf; - - if (bn_wexpand(b, top) == NULL) - return 0; - - if (window <= 3) { - for (i = 0; i < top; i++, table += width) { - BN_ULONG acc = 0; - - for (j = 0; j < width; j++) { - acc |= table[j] & - ((BN_ULONG)0 - (constant_time_eq_int(j,idx)&1)); - } - - b->d[i] = acc; - } - } else { - int xstride = 1 << (window - 2); - BN_ULONG y0, y1, y2, y3; - - i = idx >> (window - 2); /* equivalent of idx / xstride */ - idx &= xstride - 1; /* equivalent of idx % xstride */ - - y0 = (BN_ULONG)0 - (constant_time_eq_int(i,0)&1); - y1 = (BN_ULONG)0 - (constant_time_eq_int(i,1)&1); - y2 = (BN_ULONG)0 - (constant_time_eq_int(i,2)&1); - y3 = (BN_ULONG)0 - (constant_time_eq_int(i,3)&1); - - for (i = 0; i < top; i++, table += width) { - BN_ULONG acc = 0; - - for (j = 0; j < xstride; j++) { - acc |= ( (table[j + 0 * xstride] & y0) | - (table[j + 1 * xstride] & y1) | - (table[j + 2 * xstride] & y2) | - (table[j + 3 * xstride] & y3) ) - & ((BN_ULONG)0 - (constant_time_eq_int(j,idx)&1)); - } - - b->d[i] = acc; - } - } - - b->top = top; - bn_correct_top(b); - return 1; -} - -/* - * Given a pointer value, compute the next address that is a cache line - * multiple. - */ -#define MOD_EXP_CTIME_ALIGN(x_) \ - ((unsigned char*)(x_) + (MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH - (((size_t)(x_)) & (MOD_EXP_CTIME_MIN_CACHE_LINE_MASK)))) - -/* - * This variant of BN_mod_exp_mont() uses fixed windows and the special - * precomputation memory layout to limit data-dependency to a minimum to - * protect secret exponents (cf. the hyper-threading timing attacks pointed - * out by Colin Percival, - * http://www.daemonology.net/hyperthreading-considered-harmful/) - */ -int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, - const BIGNUM *m, BN_CTX *ctx, - BN_MONT_CTX *in_mont) -{ - int i, bits, ret = 0, window, wvalue; - int top; - BN_MONT_CTX *mont = NULL; - - int numPowers; - unsigned char *powerbufFree = NULL; - int powerbufLen = 0; - unsigned char *powerbuf = NULL; - BIGNUM tmp, am; -#if defined(SPARC_T4_MONT) - unsigned int t4 = 0; -#endif - - bn_check_top(a); - bn_check_top(p); - bn_check_top(m); - - if (!BN_is_odd(m)) { - BNerr(BN_F_BN_MOD_EXP_MONT_CONSTTIME, BN_R_CALLED_WITH_EVEN_MODULUS); - return (0); - } - - top = m->top; - - bits = BN_num_bits(p); - if (bits == 0) { - /* x**0 mod 1 is still zero. */ - if (BN_is_one(m)) { - ret = 1; - BN_zero(rr); - } else { - ret = BN_one(rr); - } - return ret; - } - - BN_CTX_start(ctx); - - /* - * Allocate a montgomery context if it was not supplied by the caller. If - * this is not done, things will break in the montgomery part. - */ - if (in_mont != NULL) - mont = in_mont; - else { - if ((mont = BN_MONT_CTX_new()) == NULL) - goto err; - if (!BN_MONT_CTX_set(mont, m, ctx)) - goto err; - } - -#ifdef RSAZ_ENABLED - /* - * If the size of the operands allow it, perform the optimized - * RSAZ exponentiation. For further information see - * crypto/bn/rsaz_exp.c and accompanying assembly modules. - */ - if ((16 == a->top) && (16 == p->top) && (BN_num_bits(m) == 1024) - && rsaz_avx2_eligible()) { - if (NULL == bn_wexpand(rr, 16)) - goto err; - RSAZ_1024_mod_exp_avx2(rr->d, a->d, p->d, m->d, mont->RR.d, - mont->n0[0]); - rr->top = 16; - rr->neg = 0; - bn_correct_top(rr); - ret = 1; - goto err; - } else if ((8 == a->top) && (8 == p->top) && (BN_num_bits(m) == 512)) { - if (NULL == bn_wexpand(rr, 8)) - goto err; - RSAZ_512_mod_exp(rr->d, a->d, p->d, m->d, mont->n0[0], mont->RR.d); - rr->top = 8; - rr->neg = 0; - bn_correct_top(rr); - ret = 1; - goto err; - } -#endif - - /* Get the window size to use with size of p. */ - window = BN_window_bits_for_ctime_exponent_size(bits); -#if defined(SPARC_T4_MONT) - if (window >= 5 && (top & 15) == 0 && top <= 64 && - (OPENSSL_sparcv9cap_P[1] & (CFR_MONTMUL | CFR_MONTSQR)) == - (CFR_MONTMUL | CFR_MONTSQR) && (t4 = OPENSSL_sparcv9cap_P[0])) - window = 5; - else -#endif -#if defined(OPENSSL_BN_ASM_MONT5) - if (window >= 5) { - window = 5; /* ~5% improvement for RSA2048 sign, and even - * for RSA4096 */ - /* reserve space for mont->N.d[] copy */ - powerbufLen += top * sizeof(mont->N.d[0]); - } -#endif - (void)0; - - /* - * Allocate a buffer large enough to hold all of the pre-computed powers - * of am, am itself and tmp. - */ - numPowers = 1 << window; - powerbufLen += sizeof(m->d[0]) * (top * numPowers + - ((2 * top) > - numPowers ? (2 * top) : numPowers)); -#ifdef alloca - if (powerbufLen < 3072) - powerbufFree = - alloca(powerbufLen + MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH); - else -#endif - if ((powerbufFree = - (unsigned char *)OPENSSL_malloc(powerbufLen + - MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH)) - == NULL) - goto err; - - powerbuf = MOD_EXP_CTIME_ALIGN(powerbufFree); - memset(powerbuf, 0, powerbufLen); - -#ifdef alloca - if (powerbufLen < 3072) - powerbufFree = NULL; -#endif - - /* lay down tmp and am right after powers table */ - tmp.d = (BN_ULONG *)(powerbuf + sizeof(m->d[0]) * top * numPowers); - am.d = tmp.d + top; - tmp.top = am.top = 0; - tmp.dmax = am.dmax = top; - tmp.neg = am.neg = 0; - tmp.flags = am.flags = BN_FLG_STATIC_DATA; - - /* prepare a^0 in Montgomery domain */ -#if 1 /* by Shay Gueron's suggestion */ - if (m->d[top - 1] & (((BN_ULONG)1) << (BN_BITS2 - 1))) { - /* 2^(top*BN_BITS2) - m */ - tmp.d[0] = (0 - m->d[0]) & BN_MASK2; - for (i = 1; i < top; i++) - tmp.d[i] = (~m->d[i]) & BN_MASK2; - tmp.top = top; - } else -#endif - if (!BN_to_montgomery(&tmp, BN_value_one(), mont, ctx)) - goto err; - - /* prepare a^1 in Montgomery domain */ - if (a->neg || BN_ucmp(a, m) >= 0) { - if (!BN_mod(&am, a, m, ctx)) - goto err; - if (!BN_to_montgomery(&am, &am, mont, ctx)) - goto err; - } else if (!BN_to_montgomery(&am, a, mont, ctx)) - goto err; - -#if defined(SPARC_T4_MONT) - if (t4) { - typedef int (*bn_pwr5_mont_f) (BN_ULONG *tp, const BN_ULONG *np, - const BN_ULONG *n0, const void *table, - int power, int bits); - int bn_pwr5_mont_t4_8(BN_ULONG *tp, const BN_ULONG *np, - const BN_ULONG *n0, const void *table, - int power, int bits); - int bn_pwr5_mont_t4_16(BN_ULONG *tp, const BN_ULONG *np, - const BN_ULONG *n0, const void *table, - int power, int bits); - int bn_pwr5_mont_t4_24(BN_ULONG *tp, const BN_ULONG *np, - const BN_ULONG *n0, const void *table, - int power, int bits); - int bn_pwr5_mont_t4_32(BN_ULONG *tp, const BN_ULONG *np, - const BN_ULONG *n0, const void *table, - int power, int bits); - static const bn_pwr5_mont_f pwr5_funcs[4] = { - bn_pwr5_mont_t4_8, bn_pwr5_mont_t4_16, - bn_pwr5_mont_t4_24, bn_pwr5_mont_t4_32 - }; - bn_pwr5_mont_f pwr5_worker = pwr5_funcs[top / 16 - 1]; - - typedef int (*bn_mul_mont_f) (BN_ULONG *rp, const BN_ULONG *ap, - const void *bp, const BN_ULONG *np, - const BN_ULONG *n0); - int bn_mul_mont_t4_8(BN_ULONG *rp, const BN_ULONG *ap, const void *bp, - const BN_ULONG *np, const BN_ULONG *n0); - int bn_mul_mont_t4_16(BN_ULONG *rp, const BN_ULONG *ap, - const void *bp, const BN_ULONG *np, - const BN_ULONG *n0); - int bn_mul_mont_t4_24(BN_ULONG *rp, const BN_ULONG *ap, - const void *bp, const BN_ULONG *np, - const BN_ULONG *n0); - int bn_mul_mont_t4_32(BN_ULONG *rp, const BN_ULONG *ap, - const void *bp, const BN_ULONG *np, - const BN_ULONG *n0); - static const bn_mul_mont_f mul_funcs[4] = { - bn_mul_mont_t4_8, bn_mul_mont_t4_16, - bn_mul_mont_t4_24, bn_mul_mont_t4_32 - }; - bn_mul_mont_f mul_worker = mul_funcs[top / 16 - 1]; - - void bn_mul_mont_vis3(BN_ULONG *rp, const BN_ULONG *ap, - const void *bp, const BN_ULONG *np, - const BN_ULONG *n0, int num); - void bn_mul_mont_t4(BN_ULONG *rp, const BN_ULONG *ap, - const void *bp, const BN_ULONG *np, - const BN_ULONG *n0, int num); - void bn_mul_mont_gather5_t4(BN_ULONG *rp, const BN_ULONG *ap, - const void *table, const BN_ULONG *np, - const BN_ULONG *n0, int num, int power); - void bn_flip_n_scatter5_t4(const BN_ULONG *inp, size_t num, - void *table, size_t power); - void bn_gather5_t4(BN_ULONG *out, size_t num, - void *table, size_t power); - void bn_flip_t4(BN_ULONG *dst, BN_ULONG *src, size_t num); - - BN_ULONG *np = mont->N.d, *n0 = mont->n0; - int stride = 5 * (6 - (top / 16 - 1)); /* multiple of 5, but less - * than 32 */ - - /* - * BN_to_montgomery can contaminate words above .top [in - * BN_DEBUG[_DEBUG] build]... - */ - for (i = am.top; i < top; i++) - am.d[i] = 0; - for (i = tmp.top; i < top; i++) - tmp.d[i] = 0; - - bn_flip_n_scatter5_t4(tmp.d, top, powerbuf, 0); - bn_flip_n_scatter5_t4(am.d, top, powerbuf, 1); - if (!(*mul_worker) (tmp.d, am.d, am.d, np, n0) && - !(*mul_worker) (tmp.d, am.d, am.d, np, n0)) - bn_mul_mont_vis3(tmp.d, am.d, am.d, np, n0, top); - bn_flip_n_scatter5_t4(tmp.d, top, powerbuf, 2); - - for (i = 3; i < 32; i++) { - /* Calculate a^i = a^(i-1) * a */ - if (!(*mul_worker) (tmp.d, tmp.d, am.d, np, n0) && - !(*mul_worker) (tmp.d, tmp.d, am.d, np, n0)) - bn_mul_mont_vis3(tmp.d, tmp.d, am.d, np, n0, top); - bn_flip_n_scatter5_t4(tmp.d, top, powerbuf, i); - } - - /* switch to 64-bit domain */ - np = alloca(top * sizeof(BN_ULONG)); - top /= 2; - bn_flip_t4(np, mont->N.d, top); - - bits--; - for (wvalue = 0, i = bits % 5; i >= 0; i--, bits--) - wvalue = (wvalue << 1) + BN_is_bit_set(p, bits); - bn_gather5_t4(tmp.d, top, powerbuf, wvalue); - - /* - * Scan the exponent one window at a time starting from the most - * significant bits. - */ - while (bits >= 0) { - if (bits < stride) - stride = bits + 1; - bits -= stride; - wvalue = bn_get_bits(p, bits + 1); - - if ((*pwr5_worker) (tmp.d, np, n0, powerbuf, wvalue, stride)) - continue; - /* retry once and fall back */ - if ((*pwr5_worker) (tmp.d, np, n0, powerbuf, wvalue, stride)) - continue; - - bits += stride - 5; - wvalue >>= stride - 5; - wvalue &= 31; - bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top); - bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top); - bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top); - bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top); - bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top); - bn_mul_mont_gather5_t4(tmp.d, tmp.d, powerbuf, np, n0, top, - wvalue); - } - - bn_flip_t4(tmp.d, tmp.d, top); - top *= 2; - /* back to 32-bit domain */ - tmp.top = top; - bn_correct_top(&tmp); - OPENSSL_cleanse(np, top * sizeof(BN_ULONG)); - } else -#endif -#if defined(OPENSSL_BN_ASM_MONT5) - if (window == 5 && top > 1) { - /* - * This optimization uses ideas from http://eprint.iacr.org/2011/239, - * specifically optimization of cache-timing attack countermeasures - * and pre-computation optimization. - */ - - /* - * Dedicated window==4 case improves 512-bit RSA sign by ~15%, but as - * 512-bit RSA is hardly relevant, we omit it to spare size... - */ - void bn_mul_mont_gather5(BN_ULONG *rp, const BN_ULONG *ap, - const void *table, const BN_ULONG *np, - const BN_ULONG *n0, int num, int power); - void bn_scatter5(const BN_ULONG *inp, size_t num, - void *table, size_t power); - void bn_gather5(BN_ULONG *out, size_t num, void *table, size_t power); - void bn_power5(BN_ULONG *rp, const BN_ULONG *ap, - const void *table, const BN_ULONG *np, - const BN_ULONG *n0, int num, int power); - int bn_get_bits5(const BN_ULONG *ap, int off); - int bn_from_montgomery(BN_ULONG *rp, const BN_ULONG *ap, - const BN_ULONG *not_used, const BN_ULONG *np, - const BN_ULONG *n0, int num); - - BN_ULONG *n0 = mont->n0, *np; - - /* - * BN_to_montgomery can contaminate words above .top [in - * BN_DEBUG[_DEBUG] build]... - */ - for (i = am.top; i < top; i++) - am.d[i] = 0; - for (i = tmp.top; i < top; i++) - tmp.d[i] = 0; - - /* - * copy mont->N.d[] to improve cache locality - */ - for (np = am.d + top, i = 0; i < top; i++) - np[i] = mont->N.d[i]; - - bn_scatter5(tmp.d, top, powerbuf, 0); - bn_scatter5(am.d, am.top, powerbuf, 1); - bn_mul_mont(tmp.d, am.d, am.d, np, n0, top); - bn_scatter5(tmp.d, top, powerbuf, 2); - -# if 0 - for (i = 3; i < 32; i++) { - /* Calculate a^i = a^(i-1) * a */ - bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1); - bn_scatter5(tmp.d, top, powerbuf, i); - } -# else - /* same as above, but uses squaring for 1/2 of operations */ - for (i = 4; i < 32; i *= 2) { - bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); - bn_scatter5(tmp.d, top, powerbuf, i); - } - for (i = 3; i < 8; i += 2) { - int j; - bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1); - bn_scatter5(tmp.d, top, powerbuf, i); - for (j = 2 * i; j < 32; j *= 2) { - bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); - bn_scatter5(tmp.d, top, powerbuf, j); - } - } - for (; i < 16; i += 2) { - bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1); - bn_scatter5(tmp.d, top, powerbuf, i); - bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); - bn_scatter5(tmp.d, top, powerbuf, 2 * i); - } - for (; i < 32; i += 2) { - bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1); - bn_scatter5(tmp.d, top, powerbuf, i); - } -# endif - bits--; - for (wvalue = 0, i = bits % 5; i >= 0; i--, bits--) - wvalue = (wvalue << 1) + BN_is_bit_set(p, bits); - bn_gather5(tmp.d, top, powerbuf, wvalue); - - /* - * Scan the exponent one window at a time starting from the most - * significant bits. - */ - if (top & 7) - while (bits >= 0) { - for (wvalue = 0, i = 0; i < 5; i++, bits--) - wvalue = (wvalue << 1) + BN_is_bit_set(p, bits); - - bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); - bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); - bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); - bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); - bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); - bn_mul_mont_gather5(tmp.d, tmp.d, powerbuf, np, n0, top, - wvalue); - } else { - while (bits >= 0) { - wvalue = bn_get_bits5(p->d, bits - 4); - bits -= 5; - bn_power5(tmp.d, tmp.d, powerbuf, np, n0, top, wvalue); - } - } - - ret = bn_from_montgomery(tmp.d, tmp.d, NULL, np, n0, top); - tmp.top = top; - bn_correct_top(&tmp); - if (ret) { - if (!BN_copy(rr, &tmp)) - ret = 0; - goto err; /* non-zero ret means it's not error */ - } - } else -#endif - { - if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 0, window)) - goto err; - if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&am, top, powerbuf, 1, window)) - goto err; - - /* - * If the window size is greater than 1, then calculate - * val[i=2..2^winsize-1]. Powers are computed as a*a^(i-1) (even - * powers could instead be computed as (a^(i/2))^2 to use the slight - * performance advantage of sqr over mul). - */ - if (window > 1) { - if (!BN_mod_mul_montgomery(&tmp, &am, &am, mont, ctx)) - goto err; - if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 2, - window)) - goto err; - for (i = 3; i < numPowers; i++) { - /* Calculate a^i = a^(i-1) * a */ - if (!BN_mod_mul_montgomery(&tmp, &am, &tmp, mont, ctx)) - goto err; - if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, i, - window)) - goto err; - } - } - - bits--; - for (wvalue = 0, i = bits % window; i >= 0; i--, bits--) - wvalue = (wvalue << 1) + BN_is_bit_set(p, bits); - if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&tmp, top, powerbuf, wvalue, - window)) - goto err; - - /* - * Scan the exponent one window at a time starting from the most - * significant bits. - */ - while (bits >= 0) { - wvalue = 0; /* The 'value' of the window */ - - /* Scan the window, squaring the result as we go */ - for (i = 0; i < window; i++, bits--) { - if (!BN_mod_mul_montgomery(&tmp, &tmp, &tmp, mont, ctx)) - goto err; - wvalue = (wvalue << 1) + BN_is_bit_set(p, bits); - } - - /* - * Fetch the appropriate pre-computed value from the pre-buf - */ - if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&am, top, powerbuf, wvalue, - window)) - goto err; - - /* Multiply the result into the intermediate result */ - if (!BN_mod_mul_montgomery(&tmp, &tmp, &am, mont, ctx)) - goto err; - } - } - - /* Convert the final result from montgomery to standard format */ -#if defined(SPARC_T4_MONT) - if (OPENSSL_sparcv9cap_P[0] & (SPARCV9_VIS3 | SPARCV9_PREFER_FPU)) { - am.d[0] = 1; /* borrow am */ - for (i = 1; i < top; i++) - am.d[i] = 0; - if (!BN_mod_mul_montgomery(rr, &tmp, &am, mont, ctx)) - goto err; - } else -#endif - if (!BN_from_montgomery(rr, &tmp, mont, ctx)) - goto err; - ret = 1; - err: - if ((in_mont == NULL) && (mont != NULL)) - BN_MONT_CTX_free(mont); - if (powerbuf != NULL) { - OPENSSL_cleanse(powerbuf, powerbufLen); - if (powerbufFree) - OPENSSL_free(powerbufFree); - } - BN_CTX_end(ctx); - return (ret); -} - -int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p, - const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont) -{ - BN_MONT_CTX *mont = NULL; - int b, bits, ret = 0; - int r_is_one; - BN_ULONG w, next_w; - BIGNUM *d, *r, *t; - BIGNUM *swap_tmp; -#define BN_MOD_MUL_WORD(r, w, m) \ - (BN_mul_word(r, (w)) && \ - (/* BN_ucmp(r, (m)) < 0 ? 1 :*/ \ - (BN_mod(t, r, m, ctx) && (swap_tmp = r, r = t, t = swap_tmp, 1)))) - /* - * BN_MOD_MUL_WORD is only used with 'w' large, so the BN_ucmp test is - * probably more overhead than always using BN_mod (which uses BN_copy if - * a similar test returns true). - */ - /* - * We can use BN_mod and do not need BN_nnmod because our accumulator is - * never negative (the result of BN_mod does not depend on the sign of - * the modulus). - */ -#define BN_TO_MONTGOMERY_WORD(r, w, mont) \ - (BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont), ctx)) - - if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0 - || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) { - /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ - BNerr(BN_F_BN_MOD_EXP_MONT_WORD, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED); - return 0; - } - - bn_check_top(p); - bn_check_top(m); - - if (!BN_is_odd(m)) { - BNerr(BN_F_BN_MOD_EXP_MONT_WORD, BN_R_CALLED_WITH_EVEN_MODULUS); - return (0); - } - if (m->top == 1) - a %= m->d[0]; /* make sure that 'a' is reduced */ - - bits = BN_num_bits(p); - if (bits == 0) { - /* x**0 mod 1 is still zero. */ - if (BN_is_one(m)) { - ret = 1; - BN_zero(rr); - } else { - ret = BN_one(rr); - } - return ret; - } - if (a == 0) { - BN_zero(rr); - ret = 1; - return ret; - } - - BN_CTX_start(ctx); - d = BN_CTX_get(ctx); - r = BN_CTX_get(ctx); - t = BN_CTX_get(ctx); - if (d == NULL || r == NULL || t == NULL) - goto err; - - if (in_mont != NULL) - mont = in_mont; - else { - if ((mont = BN_MONT_CTX_new()) == NULL) - goto err; - if (!BN_MONT_CTX_set(mont, m, ctx)) - goto err; - } - - r_is_one = 1; /* except for Montgomery factor */ - - /* bits-1 >= 0 */ - - /* The result is accumulated in the product r*w. */ - w = a; /* bit 'bits-1' of 'p' is always set */ - for (b = bits - 2; b >= 0; b--) { - /* First, square r*w. */ - next_w = w * w; - if ((next_w / w) != w) { /* overflow */ - if (r_is_one) { - if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) - goto err; - r_is_one = 0; - } else { - if (!BN_MOD_MUL_WORD(r, w, m)) - goto err; - } - next_w = 1; - } - w = next_w; - if (!r_is_one) { - if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) - goto err; - } - - /* Second, multiply r*w by 'a' if exponent bit is set. */ - if (BN_is_bit_set(p, b)) { - next_w = w * a; - if ((next_w / a) != w) { /* overflow */ - if (r_is_one) { - if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) - goto err; - r_is_one = 0; - } else { - if (!BN_MOD_MUL_WORD(r, w, m)) - goto err; - } - next_w = a; - } - w = next_w; - } - } - - /* Finally, set r:=r*w. */ - if (w != 1) { - if (r_is_one) { - if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) - goto err; - r_is_one = 0; - } else { - if (!BN_MOD_MUL_WORD(r, w, m)) - goto err; - } - } - - if (r_is_one) { /* can happen only if a == 1 */ - if (!BN_one(rr)) - goto err; - } else { - if (!BN_from_montgomery(rr, r, mont, ctx)) - goto err; - } - ret = 1; - err: - if ((in_mont == NULL) && (mont != NULL)) - BN_MONT_CTX_free(mont); - BN_CTX_end(ctx); - bn_check_top(rr); - return (ret); -} - -/* The old fallback, simple version :-) */ -int BN_mod_exp_simple(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, - const BIGNUM *m, BN_CTX *ctx) -{ - int i, j, bits, ret = 0, wstart, wend, window, wvalue; - int start = 1; - BIGNUM *d; - /* Table of variables obtained from 'ctx' */ - BIGNUM *val[TABLE_SIZE]; - - if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0 - || BN_get_flags(a, BN_FLG_CONSTTIME) != 0 - || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) { - /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ - BNerr(BN_F_BN_MOD_EXP_SIMPLE, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED); - return 0; - } - - bits = BN_num_bits(p); - if (bits == 0) { - /* x**0 mod 1 is still zero. */ - if (BN_is_one(m)) { - ret = 1; - BN_zero(r); - } else { - ret = BN_one(r); - } - return ret; - } - - BN_CTX_start(ctx); - d = BN_CTX_get(ctx); - val[0] = BN_CTX_get(ctx); - if (!d || !val[0]) - goto err; - - if (!BN_nnmod(val[0], a, m, ctx)) - goto err; /* 1 */ - if (BN_is_zero(val[0])) { - BN_zero(r); - ret = 1; - goto err; - } - - window = BN_window_bits_for_exponent_size(bits); - if (window > 1) { - if (!BN_mod_mul(d, val[0], val[0], m, ctx)) - goto err; /* 2 */ - j = 1 << (window - 1); - for (i = 1; i < j; i++) { - if (((val[i] = BN_CTX_get(ctx)) == NULL) || - !BN_mod_mul(val[i], val[i - 1], d, m, ctx)) - goto err; - } - } - - start = 1; /* This is used to avoid multiplication etc - * when there is only the value '1' in the - * buffer. */ - wvalue = 0; /* The 'value' of the window */ - wstart = bits - 1; /* The top bit of the window */ - wend = 0; /* The bottom bit of the window */ - - if (!BN_one(r)) - goto err; - - for (;;) { - if (BN_is_bit_set(p, wstart) == 0) { - if (!start) - if (!BN_mod_mul(r, r, r, m, ctx)) - goto err; - if (wstart == 0) - break; - wstart--; - continue; - } - /* - * We now have wstart on a 'set' bit, we now need to work out how bit - * a window to do. To do this we need to scan forward until the last - * set bit before the end of the window - */ - j = wstart; - wvalue = 1; - wend = 0; - for (i = 1; i < window; i++) { - if (wstart - i < 0) - break; - if (BN_is_bit_set(p, wstart - i)) { - wvalue <<= (i - wend); - wvalue |= 1; - wend = i; - } - } - - /* wend is the size of the current window */ - j = wend + 1; - /* add the 'bytes above' */ - if (!start) - for (i = 0; i < j; i++) { - if (!BN_mod_mul(r, r, r, m, ctx)) - goto err; - } - - /* wvalue will be an odd number < 2^window */ - if (!BN_mod_mul(r, r, val[wvalue >> 1], m, ctx)) - goto err; - - /* move the 'window' down further */ - wstart -= wend + 1; - wvalue = 0; - start = 0; - if (wstart < 0) - break; - } - ret = 1; - err: - BN_CTX_end(ctx); - bn_check_top(r); - return (ret); -} |