/* 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 #include #include #include #include #include #include "internal.h" #if !defined(OPENSSL_NO_ASM) && defined(OPENSSL_X86_64) #define OPENSSL_BN_ASM_MONT5 #define RSAZ_ENABLED #include "rsaz_exp.h" #endif int BN_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx) { int i, bits, ret = 0; BIGNUM *v, *rr; if ((p->flags & BN_FLG_CONSTTIME) != 0) { /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ OPENSSL_PUT_ERROR(BN, 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)) { goto err; } ret = 1; err: BN_CTX_end(ctx); return ret; } /* maximum precomputation table size for *variable* sliding windows */ #define TABLE_SIZE 32 typedef struct bn_recp_ctx_st { BIGNUM N; /* the divisor */ BIGNUM Nr; /* the reciprocal */ int num_bits; int shift; int flags; } BN_RECP_CTX; static void BN_RECP_CTX_init(BN_RECP_CTX *recp) { BN_init(&recp->N); BN_init(&recp->Nr); recp->num_bits = 0; recp->flags = 0; } static void BN_RECP_CTX_free(BN_RECP_CTX *recp) { if (recp == NULL) { return; } BN_free(&recp->N); BN_free(&recp->Nr); } static int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx) { if (!BN_copy(&(recp->N), d)) { return 0; } BN_zero(&recp->Nr); recp->num_bits = BN_num_bits(d); recp->shift = 0; return 1; } /* len is the expected size of the result We actually calculate with an extra * word of precision, so we can do faster division if the remainder is not * required. * r := 2^len / m */ static int BN_reciprocal(BIGNUM *r, const BIGNUM *m, int len, BN_CTX *ctx) { int ret = -1; BIGNUM *t; BN_CTX_start(ctx); t = BN_CTX_get(ctx); if (t == NULL) { goto err; } if (!BN_set_bit(t, len)) { goto err; } if (!BN_div(r, NULL, t, m, ctx)) { goto err; } ret = len; err: BN_CTX_end(ctx); return ret; } static int BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, BN_RECP_CTX *recp, BN_CTX *ctx) { int i, j, ret = 0; BIGNUM *a, *b, *d, *r; BN_CTX_start(ctx); a = BN_CTX_get(ctx); b = BN_CTX_get(ctx); if (dv != NULL) { d = dv; } else { d = BN_CTX_get(ctx); } if (rem != NULL) { r = rem; } else { r = BN_CTX_get(ctx); } if (a == NULL || b == NULL || d == NULL || r == NULL) { goto err; } if (BN_ucmp(m, &(recp->N)) < 0) { BN_zero(d); if (!BN_copy(r, m)) { return 0; } BN_CTX_end(ctx); return 1; } /* We want the remainder * Given input of ABCDEF / ab * we need multiply ABCDEF by 3 digests of the reciprocal of ab */ /* i := max(BN_num_bits(m), 2*BN_num_bits(N)) */ i = BN_num_bits(m); j = recp->num_bits << 1; if (j > i) { i = j; } /* Nr := round(2^i / N) */ if (i != recp->shift) { recp->shift = BN_reciprocal(&(recp->Nr), &(recp->N), i, ctx); /* BN_reciprocal returns i, or -1 for an error */ } if (recp->shift == -1) { goto err; } /* d := |round(round(m / 2^BN_num_bits(N)) * recp->Nr / 2^(i - * BN_num_bits(N)))| * = |round(round(m / 2^BN_num_bits(N)) * round(2^i / N) / 2^(i - * BN_num_bits(N)))| * <= |(m / 2^BN_num_bits(N)) * (2^i / N) * (2^BN_num_bits(N) / 2^i)| * = |m/N| */ if (!BN_rshift(a, m, recp->num_bits)) { goto err; } if (!BN_mul(b, a, &(recp->Nr), ctx)) { goto err; } if (!BN_rshift(d, b, i - recp->num_bits)) { goto err; } d->neg = 0; if (!BN_mul(b, &(recp->N), d, ctx)) { goto err; } if (!BN_usub(r, m, b)) { goto err; } r->neg = 0; j = 0; while (BN_ucmp(r, &(recp->N)) >= 0) { if (j++ > 2) { OPENSSL_PUT_ERROR(BN, BN_R_BAD_RECIPROCAL); goto err; } if (!BN_usub(r, r, &(recp->N))) { goto err; } if (!BN_add_word(d, 1)) { goto err; } } r->neg = BN_is_zero(r) ? 0 : m->neg; d->neg = m->neg ^ recp->N.neg; ret = 1; err: BN_CTX_end(ctx); return ret; } static int BN_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *x, const BIGNUM *y, BN_RECP_CTX *recp, BN_CTX *ctx) { int ret = 0; BIGNUM *a; const BIGNUM *ca; BN_CTX_start(ctx); a = BN_CTX_get(ctx); if (a == NULL) { goto err; } if (y != NULL) { if (x == y) { if (!BN_sqr(a, x, ctx)) { goto err; } } else { if (!BN_mul(a, x, y, ctx)) { goto err; } } ca = a; } else { ca = x; /* Just do the mod */ } ret = BN_div_recp(NULL, r, ca, recp, ctx); err: BN_CTX_end(ctx); return ret; } /* BN_window_bits_for_exponent_size -- macro for sliding window mod_exp * functions * * For window size 'w' (w >= 2) and a random 'b' bits exponent, the number of * multiplications is a constant plus on average * * 2^(w-1) + (b-w)/(w+1); * * here 2^(w-1) is for precomputing the table (we actually need entries only * for windows that have the lowest bit set), and (b-w)/(w+1) is an * approximation for the expected number of w-bit windows, not counting the * first one. * * Thus we should use * * w >= 6 if b > 671 * w = 5 if 671 > b > 239 * w = 4 if 239 > b > 79 * w = 3 if 79 > b > 23 * w <= 2 if 23 > b * * (with draws in between). Very small exponents are often selected * with low Hamming weight, so we use w = 1 for b <= 23. */ #define BN_window_bits_for_exponent_size(b) \ ((b) > 671 ? 6 : \ (b) > 239 ? 5 : \ (b) > 79 ? 4 : \ (b) > 23 ? 3 : 1) static int mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx) { int i, j, bits, ret = 0, wstart, window; 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_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ OPENSSL_PUT_ERROR(BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED); return 0; } bits = BN_num_bits(p); if (bits == 0) { 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. */ wstart = bits - 1; /* The top bit of the window */ if (!BN_one(r)) { goto err; } for (;;) { int wvalue; /* The 'value' of the window */ int wend; /* The bottom bit of the window */ 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 */ 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; start = 0; if (wstart < 0) { break; } } ret = 1; err: BN_CTX_end(ctx); BN_RECP_CTX_free(&recp); return ret; } int BN_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx) { /* 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.) */ if (BN_is_odd(m)) { if (a->top == 1 && !a->neg && BN_get_flags(p, BN_FLG_CONSTTIME) == 0) { BN_ULONG A = a->d[0]; return BN_mod_exp_mont_word(r, A, p, m, ctx, NULL); } return BN_mod_exp_mont(r, a, p, m, ctx, NULL); } return mod_exp_recp(r, a, p, m, ctx); } 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, window; 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) { return BN_mod_exp_mont_consttime(rr, a, p, m, ctx, in_mont); } if (!BN_is_odd(m)) { OPENSSL_PUT_ERROR(BN, BN_R_CALLED_WITH_EVEN_MODULUS); return 0; } bits = BN_num_bits(p); if (bits == 0) { 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 { mont = BN_MONT_CTX_new(); if (mont == 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. */ wstart = bits - 1; /* The top bit of the window */ 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 if (!BN_to_montgomery(r, BN_value_one(), mont, ctx)) { goto err; } for (;;) { int wvalue; /* The 'value' of the window */ int wend; /* The bottom bit of the window */ if (BN_is_bit_set(p, wstart) == 0) { if (!start && !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 */ 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; start = 0; if (wstart < 0) { break; } } if (!BN_from_montgomery(rr, r, mont, ctx)) { goto err; } ret = 1; err: if (in_mont == NULL) { BN_MONT_CTX_free(mont); } BN_CTX_end(ctx); return ret; } /* 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 copy_to_prebuf(const BIGNUM *b, int top, unsigned char *buf, int idx, int width) { size_t i, j; if (top > b->top) { top = b->top; /* this works because 'buf' is explicitly zeroed */ } for (i = 0, j = idx; i < top * sizeof b->d[0]; i++, j += width) { buf[j] = ((unsigned char *)b->d)[i]; } return 1; } static int copy_from_prebuf(BIGNUM *b, int top, unsigned char *buf, int idx, int width) { size_t i, j; if (bn_wexpand(b, top) == NULL) { return 0; } for (i = 0, j = idx; i < top * sizeof b->d[0]; i++, j += width) { ((unsigned char *)b->d)[i] = buf[j]; } b->top = top; bn_correct_top(b); return 1; } /* BN_mod_exp_mont_conttime is based on the assumption that the L1 data cache * line width of the target processor is at least the following value. */ #define MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH (64) #define MOD_EXP_CTIME_MIN_CACHE_LINE_MASK \ (MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH - 1) /* Window sizes optimized for fixed window size modular exponentiation * algorithm (BN_mod_exp_mont_consttime). * * To achieve the security goals of BN_mode_exp_mont_consttime, the maximum * size of the window must not exceed * log_2(MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH). * * Window size thresholds are defined for cache line sizes of 32 and 64, cache * line sizes where log_2(32)=5 and log_2(64)=6 respectively. A window size of * 7 should only be used on processors that have a 128 byte or greater cache * line size. */ #if MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH == 64 #define BN_window_bits_for_ctime_exponent_size(b) \ ((b) > 937 ? 6 : (b) > 306 ? 5 : (b) > 89 ? 4 : (b) > 22 ? 3 : 1) #define BN_MAX_WINDOW_BITS_FOR_CTIME_EXPONENT_SIZE (6) #elif MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH == 32 #define BN_window_bits_for_ctime_exponent_size(b) \ ((b) > 306 ? 5 : (b) > 89 ? 4 : (b) > 22 ? 3 : 1) #define BN_MAX_WINDOW_BITS_FOR_CTIME_EXPONENT_SIZE (5) #endif /* 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; top = m->top; if (!(m->d[0] & 1)) { OPENSSL_PUT_ERROR(BN, BN_R_CALLED_WITH_EVEN_MODULUS); return 0; } bits = BN_num_bits(p); if (bits == 0) { 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 { mont = BN_MONT_CTX_new(); if (mont == NULL || !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(OPENSSL_BN_ASM_MONT5) if (window >= 5) { window = 5; /* ~5% improvement for RSA2048 sign, and even for RSA4096 */ if ((top & 7) == 0) { powerbufLen += 2 * top * sizeof(m->d[0]); } } #endif /* 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 */ /* 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 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) || !BN_to_montgomery(&am, &am, mont, ctx)) { goto err; } } else if (!BN_to_montgomery(&am, a, mont, ctx)) { goto err; } #if defined(OPENSSL_BN_ASM_MONT5) /* 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... */ if (window == 5 && top > 1) { 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_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 *np = mont->N.d, *n0 = mont->n0, *np2; /* 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; } if (top & 7) { np2 = np; } else { for (np2 = am.d + top, i = 0; i < top; i++) { np2[2 * i] = np[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); /* 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, np2, 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, np2, 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, np2, n0, top, i - 1); bn_scatter5(tmp.d, top, powerbuf, i); } 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); /* At this point |bits| is 4 mod 5 and at least -1. (|bits| is the first bit * that has not been read yet.) */ assert(bits >= -1 && (bits == -1 || bits % 5 == 4)); /* 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 { const uint8_t *p_bytes = (const uint8_t *)p->d; int max_bits = p->top * BN_BITS2; assert(bits < max_bits); /* |p = 0| has been handled as a special case, so |max_bits| is at least * one word. */ assert(max_bits >= 64); /* If the first bit to be read lands in the last byte, unroll the first * iteration to avoid reading past the bounds of |p->d|. (After the first * iteration, we are guaranteed to be past the last byte.) Note |bits| * here is the top bit, inclusive. */ if (bits - 4 >= max_bits - 8) { /* Read five bits from |bits-4| through |bits|, inclusive. */ wvalue = p_bytes[p->top * BN_BYTES - 1]; wvalue >>= (bits - 4) & 7; wvalue &= 0x1f; bits -= 5; bn_power5(tmp.d, tmp.d, powerbuf, np2, n0, top, wvalue); } while (bits >= 0) { /* Read five bits from |bits-4| through |bits|, inclusive. */ int first_bit = bits - 4; wvalue = *(const uint16_t *) (p_bytes + (first_bit >> 3)); wvalue >>= first_bit & 7; wvalue &= 0x1f; bits -= 5; bn_power5(tmp.d, tmp.d, powerbuf, np2, n0, top, wvalue); } } ret = bn_from_montgomery(tmp.d, tmp.d, NULL, np2, 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 (!copy_to_prebuf(&tmp, top, powerbuf, 0, numPowers) || !copy_to_prebuf(&am, top, powerbuf, 1, numPowers)) { 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) || !copy_to_prebuf(&tmp, top, powerbuf, 2, numPowers)) { 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) || !copy_to_prebuf(&tmp, top, powerbuf, i, numPowers)) { goto err; } } } bits--; for (wvalue = 0, i = bits % window; i >= 0; i--, bits--) { wvalue = (wvalue << 1) + BN_is_bit_set(p, bits); } if (!copy_from_prebuf(&tmp, top, powerbuf, wvalue, numPowers)) { 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 (!copy_from_prebuf(&am, top, powerbuf, wvalue, numPowers)) { 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 (!BN_from_montgomery(rr, &tmp, mont, ctx)) { goto err; } ret = 1; err: if (in_mont == NULL) { BN_MONT_CTX_free(mont); } if (powerbuf != NULL) { OPENSSL_cleanse(powerbuf, powerbufLen); 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_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ OPENSSL_PUT_ERROR(BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED); return 0; } if (!BN_is_odd(m)) { OPENSSL_PUT_ERROR(BN, 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 { mont = BN_MONT_CTX_new(); if (mont == NULL || !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) { BN_MONT_CTX_free(mont); } BN_CTX_end(ctx); return ret; } #define TABLE_SIZE 32 int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1, const BIGNUM *a2, const BIGNUM *p2, const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont) { int i, j, bits, b, bits1, bits2, ret = 0, wpos1, wpos2, window1, window2, wvalue1, wvalue2; int r_is_one = 1; BIGNUM *d, *r; const BIGNUM *a_mod_m; /* Tables of variables obtained from 'ctx' */ BIGNUM *val1[TABLE_SIZE], *val2[TABLE_SIZE]; BN_MONT_CTX *mont = NULL; if (!(m->d[0] & 1)) { OPENSSL_PUT_ERROR(BN, BN_R_CALLED_WITH_EVEN_MODULUS); return 0; } bits1 = BN_num_bits(p1); bits2 = BN_num_bits(p2); if (bits1 == 0 && bits2 == 0) { ret = BN_one(rr); return ret; } bits = (bits1 > bits2) ? bits1 : bits2; BN_CTX_start(ctx); d = BN_CTX_get(ctx); r = BN_CTX_get(ctx); val1[0] = BN_CTX_get(ctx); val2[0] = BN_CTX_get(ctx); if (!d || !r || !val1[0] || !val2[0]) { goto err; } if (in_mont != NULL) { mont = in_mont; } else { mont = BN_MONT_CTX_new(); if (mont == NULL) { goto err; } if (!BN_MONT_CTX_set(mont, m, ctx)) { goto err; } } window1 = BN_window_bits_for_exponent_size(bits1); window2 = BN_window_bits_for_exponent_size(bits2); /* Build table for a1: val1[i] := a1^(2*i + 1) mod m for i = 0 .. * 2^(window1-1) */ if (a1->neg || BN_ucmp(a1, m) >= 0) { if (!BN_mod(val1[0], a1, m, ctx)) { goto err; } a_mod_m = val1[0]; } else { a_mod_m = a1; } if (BN_is_zero(a_mod_m)) { BN_zero(rr); ret = 1; goto err; } if (!BN_to_montgomery(val1[0], a_mod_m, mont, ctx)) { goto err; } if (window1 > 1) { if (!BN_mod_mul_montgomery(d, val1[0], val1[0], mont, ctx)) { goto err; } j = 1 << (window1 - 1); for (i = 1; i < j; i++) { if (((val1[i] = BN_CTX_get(ctx)) == NULL) || !BN_mod_mul_montgomery(val1[i], val1[i - 1], d, mont, ctx)) { goto err; } } } /* Build table for a2: val2[i] := a2^(2*i + 1) mod m for i = 0 .. * 2^(window2-1) */ if (a2->neg || BN_ucmp(a2, m) >= 0) { if (!BN_mod(val2[0], a2, m, ctx)) { goto err; } a_mod_m = val2[0]; } else { a_mod_m = a2; } if (BN_is_zero(a_mod_m)) { BN_zero(rr); ret = 1; goto err; } if (!BN_to_montgomery(val2[0], a_mod_m, mont, ctx)) { goto err; } if (window2 > 1) { if (!BN_mod_mul_montgomery(d, val2[0], val2[0], mont, ctx)) { goto err; } j = 1 << (window2 - 1); for (i = 1; i < j; i++) { if (((val2[i] = BN_CTX_get(ctx)) == NULL) || !BN_mod_mul_montgomery(val2[i], val2[i - 1], d, mont, ctx)) { goto err; } } } /* Now compute the power product, using independent windows. */ r_is_one = 1; wvalue1 = 0; /* The 'value' of the first window */ wvalue2 = 0; /* The 'value' of the second window */ wpos1 = 0; /* If wvalue1 > 0, the bottom bit of the first window */ wpos2 = 0; /* If wvalue2 > 0, the bottom bit of the second window */ if (!BN_to_montgomery(r, BN_value_one(), mont, ctx)) { goto err; } for (b = bits - 1; b >= 0; b--) { if (!r_is_one) { if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) { goto err; } } if (!wvalue1 && BN_is_bit_set(p1, b)) { /* consider bits b-window1+1 .. b for this window */ i = b - window1 + 1; /* works for i<0 */ while (!BN_is_bit_set(p1, i)) { i++; } wpos1 = i; wvalue1 = 1; for (i = b - 1; i >= wpos1; i--) { wvalue1 <<= 1; if (BN_is_bit_set(p1, i)) { wvalue1++; } } } if (!wvalue2 && BN_is_bit_set(p2, b)) { /* consider bits b-window2+1 .. b for this window */ i = b - window2 + 1; while (!BN_is_bit_set(p2, i)) { i++; } wpos2 = i; wvalue2 = 1; for (i = b - 1; i >= wpos2; i--) { wvalue2 <<= 1; if (BN_is_bit_set(p2, i)) { wvalue2++; } } } if (wvalue1 && b == wpos1) { /* wvalue1 is odd and < 2^window1 */ if (!BN_mod_mul_montgomery(r, r, val1[wvalue1 >> 1], mont, ctx)) { goto err; } wvalue1 = 0; r_is_one = 0; } if (wvalue2 && b == wpos2) { /* wvalue2 is odd and < 2^window2 */ if (!BN_mod_mul_montgomery(r, r, val2[wvalue2 >> 1], mont, ctx)) { goto err; } wvalue2 = 0; r_is_one = 0; } } if (!BN_from_montgomery(rr, r, mont, ctx)) { goto err; } ret = 1; err: if (in_mont == NULL) { BN_MONT_CTX_free(mont); } BN_CTX_end(ctx); return ret; }