X-Git-Url: https://git.openssl.org/gitweb/?p=openssl.git;a=blobdiff_plain;f=crypto%2Fbn%2Fbn_exp.c;h=88f2baf0e553cf6629644a9a415be643dd0f07c4;hp=0a0db370c35bcdced30a5d63ecf339ec35e69c71;hb=72a7a7021fa8bc82a11bc08bac1b0241a92143d0;hpb=d02b48c63a58ea4367a0e905979f140b7d090f86 diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c index 0a0db370c3..88f2baf0e5 100644 --- a/crypto/bn/bn_exp.c +++ b/crypto/bn/bn_exp.c @@ -1,510 +1,1395 @@ -/* crypto/bn/bn_exp.c */ -/* Copyright (C) 1995-1997 Eric Young (eay@cryptsoft.com) - * All rights reserved. +/* + * Copyright 1995-2019 The OpenSSL Project Authors. 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.] + * Licensed under the OpenSSL license (the "License"). You may not use + * this file except in compliance with the License. You can obtain a copy + * in the file LICENSE in the source distribution or at + * https://www.openssl.org/source/license.html */ -#include -#include "cryptlib.h" +#include "internal/cryptlib.h" +#include "internal/constant_time_locl.h" #include "bn_lcl.h" -/* slow but works */ -int BN_mod_mul(ret, a, b, m, ctx) -BIGNUM *ret; -BIGNUM *a; -BIGNUM *b; -BIGNUM *m; -BN_CTX *ctx; - { - BIGNUM *t; - int r=0; - - t=ctx->bn[ctx->tos++]; - if (a == b) - { if (!BN_sqr(t,a,ctx)) goto err; } - else - { if (!BN_mul(t,a,b)) goto err; } - if (!BN_mod(ret,t,m,ctx)) goto err; - r=1; -err: - ctx->tos--; - return(r); - } - -#if 0 -/* this one works - simple but works */ -int BN_mod_exp(r,a,p,m,ctx) -BIGNUM *r,*a,*p,*m; -BN_CTX *ctx; - { - int i,bits,ret=0; - BIGNUM *v,*tmp; - - v=ctx->bn[ctx->tos++]; - tmp=ctx->bn[ctx->tos++]; - - if (BN_copy(v,a) == NULL) goto err; - bits=BN_num_bits(p); - - if (BN_is_odd(p)) - { if (BN_copy(r,a) == NULL) goto err; } - else { if (BN_one(r)) goto err; } - - for (i=1; itos-=2; - return(ret); - } +#include +#ifdef _WIN32 +# include +# ifndef alloca +# define alloca _alloca +# endif +#elif defined(__GNUC__) +# ifndef alloca +# define alloca(s) __builtin_alloca((s)) +# endif +#elif defined(__sun) +# include +#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 -int BN_mod_exp(r,a,p,m,ctx) -BIGNUM *r; -BIGNUM *a; -BIGNUM *p; -BIGNUM *m; -BN_CTX *ctx; - { - int ret; +/* 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); + rr = ((r == a) || (r == p)) ? BN_CTX_get(ctx) : 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)) - { ret=BN_mod_exp_mont(r,a,p,m,ctx); } - else + 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); } + { + ret = BN_mod_exp_recp(r, a, p, m, ctx); + } #else - { ret=BN_mod_exp_simple(r,a,p,m,ctx); } + { + 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, or x**0 mod -1 is still zero. */ + if (BN_abs_is_word(m, 1)) { + 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 (val[0] == NULL) + 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, or x**0 mod -1 is still zero. */ + if (BN_abs_is_word(m, 1)) { + 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 (val[0] == NULL) + 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_to_mont_fixed_top(val[0], aa, mont, ctx)) + goto err; /* 1 */ + + window = BN_window_bits_for_exponent_size(bits); + if (window > 1) { + if (!bn_mul_mont_fixed_top(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_mul_mont_fixed_top(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; + r->flags |= BN_FLG_FIXED_TOP; + } else +#endif + if (!bn_to_mont_fixed_top(r, BN_value_one(), mont, ctx)) + goto err; + for (;;) { + if (BN_is_bit_set(p, wstart) == 0) { + if (!start) { + if (!bn_mul_mont_fixed_top(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_mul_mont_fixed_top(r, r, r, mont, ctx)) + goto err; + } + + /* wvalue will be an odd number < 2^window */ + if (!bn_mul_mont_fixed_top(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; + } + /* + * Done with zero-padded intermediate BIGNUMs. Final BN_from_montgomery + * removes padding [if any] and makes return value suitable for public + * API consumer. + */ +#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) + BN_MONT_CTX_free(mont); + BN_CTX_end(ctx); + bn_check_top(rr); + return ret; +} + +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; +} + +/* + * 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; + /* + * We declare table 'volatile' in order to discourage compiler + * from reordering loads from the table. Concern is that if + * reordered in specific manner loads might give away the + * information we are trying to conceal. Some would argue that + * compiler can reorder them anyway, but it can as well be + * argued that doing so would be violation of standard... + */ + 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; + b->flags |= BN_FLG_FIXED_TOP; + 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, wmask, window0; + 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; + + /* + * Use all bits stored in |p|, rather than |BN_num_bits|, so we do not leak + * whether the top bits are zero. + */ + bits = p->top * BN_BITS2; + if (bits == 0) { + /* x**0 mod 1, or x**0 mod -1 is still zero. */ + if (BN_abs_is_word(m, 1)) { + 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; + } + + if (a->neg || BN_ucmp(a, m) >= 0) { + BIGNUM *reduced = BN_CTX_get(ctx); + if (reduced == NULL + || !BN_nnmod(reduced, a, m, ctx)) { + goto err; + } + a = reduced; + } + +#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 = + 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_mont_fixed_top(&tmp, BN_value_one(), mont, ctx)) + goto err; + + /* prepare a^1 in Montgomery domain */ + if (!bn_to_mont_fixed_top(&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); + + /* + * The exponent may not have a whole number of fixed-size windows. + * To simplify the main loop, the initial window has between 1 and + * full-window-size bits such that what remains is always a whole + * number of windows + */ + window0 = (bits - 1) % 5 + 1; + wmask = (1 << window0) - 1; + bits -= window0; + wvalue = bn_get_bits(p, bits) & wmask; + 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; + bits -= stride; + wvalue = bn_get_bits(p, bits); + + 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 + /* + * The exponent may not have a whole number of fixed-size windows. + * To simplify the main loop, the initial window has between 1 and + * full-window-size bits such that what remains is always a whole + * number of windows + */ + window0 = (bits - 1) % 5 + 1; + wmask = (1 << window0) - 1; + bits -= window0; + wvalue = bn_get_bits(p, bits) & wmask; + 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) { + 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, + bn_get_bits5(p->d, bits -= 5)); + } + } else { + while (bits > 0) { + bn_power5(tmp.d, tmp.d, powerbuf, np, n0, top, + bn_get_bits5(p->d, bits -= 5)); + } + } + + 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_mul_mont_fixed_top(&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_mul_mont_fixed_top(&tmp, &am, &tmp, mont, ctx)) + goto err; + if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, i, + window)) + goto err; + } + } + + /* + * The exponent may not have a whole number of fixed-size windows. + * To simplify the main loop, the initial window has between 1 and + * full-window-size bits such that what remains is always a whole + * number of windows + */ + window0 = (bits - 1) % window + 1; + wmask = (1 << window0) - 1; + bits -= window0; + wvalue = bn_get_bits(p, bits) & wmask; + if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&tmp, top, powerbuf, wvalue, + window)) + goto err; + + wmask = (1 << window) - 1; + /* + * Scan the exponent one window at a time starting from the most + * significant bits. + */ + while (bits > 0) { + + /* Square the result window-size times */ + for (i = 0; i < window; i++) + if (!bn_mul_mont_fixed_top(&tmp, &tmp, &tmp, mont, ctx)) + goto err; + + /* + * Get a window's worth of bits from the exponent + * This avoids calling BN_is_bit_set for each bit, which + * is not only slower but also makes each bit vulnerable to + * EM (and likely other) side-channel attacks like One&Done + * (for details see "One&Done: A Single-Decryption EM-Based + * Attack on OpenSSL's Constant-Time Blinded RSA" by M. Alam, + * H. Khan, M. Dey, N. Sinha, R. Callan, A. Zajic, and + * M. Prvulovic, in USENIX Security'18) + */ + bits -= window; + wvalue = bn_get_bits(p, bits) & wmask; + /* + * 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_mul_mont_fixed_top(&tmp, &tmp, &am, mont, ctx)) + goto err; + } + } + + /* + * Done with zero-padded intermediate BIGNUMs. Final BN_from_montgomery + * removes padding [if any] and makes return value suitable for public + * API consumer. + */ +#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) + 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 *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 */ - return(ret); - } - -/* #ifdef RECP_MUL_MOD */ -int BN_mod_exp_recp(r,a,p,m,ctx) -BIGNUM *r; -BIGNUM *a; -BIGNUM *p; -BIGNUM *m; -BN_CTX *ctx; - { - int nb,i,j,bits,ret=0,wstart,wend,window,wvalue; - int start=1; - BIGNUM *d,*aa; - BIGNUM *val[16]; - - d=ctx->bn[ctx->tos++]; - aa=ctx->bn[ctx->tos++]; - bits=BN_num_bits(p); - - if (bits == 0) - { - BN_one(r); - return(1); - } - nb=BN_reciprocal(d,m,ctx); - if (nb == -1) goto err; - - val[0]=BN_new(); - if (!BN_mod(val[0],a,m,ctx)) goto err; /* 1 */ - if (!BN_mod_mul_reciprocal(aa,val[0],val[0],m,d,nb,ctx)) - goto err; /* 2 */ - - if (bits <= 17) /* This is probably 3 or 0x10001, so just do singles */ - window=1; - else if (bits >= 256) - window=5; /* max size of window */ - else if (bits >= 128) - window=4; - else - window=3; - - j=1<<(window-1); - for (i=1; i>1],m,d,nb,ctx)) - goto err; - - /* move the 'window' down further */ - wstart-=wend+1; - wvalue=0; - start=0; - if (wstart < 0) break; - } - ret=1; -err: - ctx->tos-=2; - for (i=0; i<16; i++) - if (val[i] != NULL) BN_clear_free(val[i]); - return(ret); - } -/* #endif */ - -/* #ifdef MONT_MUL_MOD */ -int BN_mod_exp_mont(r,a,p,m,ctx) -BIGNUM *r; -BIGNUM *a; -BIGNUM *p; -BIGNUM *m; -BN_CTX *ctx; - { - int i,j,bits,ret=0,wstart,wend,window,wvalue; - int start=1; - BIGNUM *d,*aa; - BIGNUM *val[16]; - BN_MONT_CTX *mont=NULL; - - if (!(m->d[0] & 1)) - { - BNerr(BN_F_BN_MOD_EXP_MONT,BN_R_CALLED_WITH_EVEN_MODULUS); - return(0); - } - d=ctx->bn[ctx->tos++]; - bits=BN_num_bits(p); - if (bits == 0) - { - BN_one(r); - return(1); - } - - /* If this is not done, things will break in the montgomery - * part */ - - if ((mont=BN_MONT_CTX_new()) == NULL) goto err; - if (!BN_MONT_CTX_set(mont,m,ctx)) goto err; - - val[0]=BN_new(); - if (BN_ucmp(a,m) >= 0) - { - BN_mod(val[0],a,m,ctx); - aa=val[0]; - } - else - aa=a; - if (!BN_to_montgomery(val[0],aa,mont,ctx)) goto err; /* 1 */ - if (!BN_mod_mul_montgomery(d,val[0],val[0],mont,ctx)) goto err; /* 2 */ - - if (bits <= 17) /* This is probably 3 or 0x10001, so just do singles */ - window=1; - else if (bits >= 256) - window=5; /* max size of window */ - else if (bits >= 128) - window=4; - else - window=3; - - j=1<<(window-1); - for (i=1; i>1],mont,ctx)) - goto err; - - /* move the 'window' down further */ - wstart-=wend+1; - wvalue=0; - start=0; - if (wstart < 0) break; - } - BN_from_montgomery(r,r,mont,ctx); - ret=1; -err: - if (mont != NULL) BN_MONT_CTX_free(mont); - ctx->tos--; - for (i=0; i<16; i++) - if (val[i] != NULL) BN_clear_free(val[i]); - return(ret); - } -/* #endif */ + bits = BN_num_bits(p); + if (bits == 0) { + /* x**0 mod 1, or x**0 mod -1 is still zero. */ + if (BN_abs_is_word(m, 1)) { + 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); + r = BN_CTX_get(ctx); + t = BN_CTX_get(ctx); + if (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) + 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(r,a,p,m,ctx) -BIGNUM *r; -BIGNUM *a; -BIGNUM *p; -BIGNUM *m; -BN_CTX *ctx; - { - int i,j,bits,ret=0,wstart,wend,window,wvalue; - int start=1; - BIGNUM *d; - BIGNUM *val[16]; - - d=ctx->bn[ctx->tos++]; - bits=BN_num_bits(p); - - if (bits == 0) - { - BN_one(r); - return(1); - } - - val[0]=BN_new(); - if (!BN_mod(val[0],a,m,ctx)) goto err; /* 1 */ - if (!BN_mod_mul(d,val[0],val[0],m,ctx)) - goto err; /* 2 */ - - if (bits <= 17) /* This is probably 3 or 0x10001, so just do singles */ - window=1; - else if (bits >= 256) - window=5; /* max size of window */ - else if (bits >= 128) - window=4; - else - window=3; - - j=1<<(window-1); - for (i=1; i>1],m,ctx)) - goto err; - - /* move the 'window' down further */ - wstart-=wend+1; - wvalue=0; - start=0; - if (wstart < 0) break; - } - ret=1; -err: - ctx->tos--; - for (i=0; i<16; i++) - if (val[i] != NULL) BN_clear_free(val[i]); - return(ret); - } +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, or x**0 mod -1 is still zero. */ + if (BN_abs_is_word(m, 1)) { + 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 (val[0] == NULL) + 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; +}