X-Git-Url: https://git.openssl.org/?p=openssl.git;a=blobdiff_plain;f=crypto%2Fbn%2Fbn_exp.c;h=70a33f0d936c81fab3f6a77e411f7e354c652edc;hp=0c11601675493bef66c3f88a6bf1c7c88f642b5c;hb=6343829a391df59e46e513c84b6264ee71ad9518;hpb=bd03b99b9bb860e062f08ec6d919c0841d951833 diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c index 0c11601675..70a33f0d93 100644 --- a/crypto/bn/bn_exp.c +++ b/crypto/bn/bn_exp.c @@ -55,84 +55,79 @@ * 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 "cryptlib.h" #include "bn_lcl.h" -#ifdef ATALLA -# include -# include -# include -# include -#endif - -#define TABLE_SIZE 16 -/* slow but works */ -int BN_mod_mul(BIGNUM *ret, BIGNUM *a, BIGNUM *b, const BIGNUM *m, BN_CTX *ctx) - { - BIGNUM *t; - int r=0; - - bn_check_top(a); - bn_check_top(b); - bn_check_top(m); - - BN_CTX_start(ctx); - if ((t = BN_CTX_get(ctx)) == NULL) goto err; - if (a == b) - { if (!BN_sqr(t,a,ctx)) goto err; } - else - { if (!BN_mul(t,a,b,ctx)) goto err; } - if (!BN_mod(ret,t,m,ctx)) goto err; - r=1; -err: - BN_CTX_end(ctx); - return(r); - } +/* maximum precomputation table size for *variable* sliding windows */ +#define TABLE_SIZE 32 -#if 0 /* this one works - simple but works */ -int BN_mod_exp(BIGNUM *r, BIGNUM *a, BIGNUM *p, BIGNUM *m, BN_CTX *ctx) +int BN_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx) { int i,bits,ret=0; - BIGNUM *v,*tmp; - - BN_CTX_start(ctx); - v = BN_CTX_get(ctx); - tmp = BN_CTX_get(ctx); - if (v == NULL || tmp == NULL) goto err; - - 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; } + BIGNUM *v,*rr; - for (i=1; id[m->top-1]&BN_TBIT) && BN_is_odd(m)) */ if (BN_is_odd(m)) - { ret=BN_mod_exp_mont(r,a,p,m,ctx,NULL); } + { +# ifdef MONT_EXP_WORD + if (a->top == 1 && !a->neg && (BN_get_flags(p, 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 @@ -363,62 +230,77 @@ int BN_mod_exp(BIGNUM *r, BIGNUM *a, const BIGNUM *p, const BIGNUM *m, { ret=BN_mod_exp_simple(r,a,p,m,ctx); } #endif -#ifdef ATALLA - tried_atalla=0; -#endif - + bn_check_top(r); return(ret); } -/* #ifdef RECP_MUL_MOD */ + 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,ts=0; + int start=1; BIGNUM *aa; - BIGNUM val[TABLE_SIZE]; + /* 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() */ + BNerr(BN_F_BN_MOD_EXP_RECP,ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED); + return -1; + } + bits=BN_num_bits(p); if (bits == 0) { - BN_one(r); - return(1); + ret = BN_one(r); + return ret; } BN_CTX_start(ctx); - if ((aa = BN_CTX_get(ctx)) == NULL) goto err; + aa = BN_CTX_get(ctx); + val[0] = BN_CTX_get(ctx); + if(!aa || !val[0]) goto err; BN_RECP_CTX_init(&recp); - if (BN_RECP_CTX_set(&recp,m,ctx) <= 0) goto err; - - BN_init(&(val[0])); - ts=1; - - if (!BN_mod(&(val[0]),a,m,ctx)) goto err; /* 1 */ - if (!BN_mod_mul_reciprocal(aa,&(val[0]),&(val[0]),&recp,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; + 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 - window=3; + { + if (BN_RECP_CTX_set(&recp,m,ctx) <= 0) goto err; + } - j=1<<(window-1); - for (i=1; i 1) + { + if (!BN_mod_mul_reciprocal(aa,val[0],val[0],&recp,ctx)) + goto err; /* 2 */ + j=1<<(window-1); + for (i=1; i>1]),&recp,ctx)) + if (!BN_mod_mul_reciprocal(r,r,val[wvalue>>1],&recp,ctx)) goto err; /* move the 'window' down further */ @@ -480,35 +362,33 @@ int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, ret=1; err: BN_CTX_end(ctx); - for (i=0; id[0] & 1)) + if (!BN_is_odd(m)) { BNerr(BN_F_BN_MOD_EXP_MONT,BN_R_CALLED_WITH_EVEN_MODULUS); return(0); @@ -516,56 +396,56 @@ int BN_mod_exp_mont(BIGNUM *rr, BIGNUM *a, const BIGNUM *p, bits=BN_num_bits(p); if (bits == 0) { - BN_one(rr); - return(1); + ret = BN_one(rr); + return ret; } + BN_CTX_start(ctx); d = BN_CTX_get(ctx); r = BN_CTX_get(ctx); - if (d == NULL || r == NULL) goto err; + 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 1 if (in_mont != NULL) mont=in_mont; else -#endif { if ((mont=BN_MONT_CTX_new()) == NULL) goto err; if (!BN_MONT_CTX_set(mont,m,ctx)) goto err; } - BN_init(&val[0]); - ts=1; - if (BN_ucmp(a,m) >= 0) + if (a->neg || BN_ucmp(a,m) >= 0) { - BN_mod(&(val[0]),a,m,ctx); - aa= &(val[0]); + if (!BN_nnmod(val[0],a,m,ctx)) + goto err; + 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 <= 20) /* 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; + if (BN_is_zero(aa)) + { + BN_zero(rr); + ret = 1; + goto err; + } + if (!BN_to_montgomery(val[0],aa,mont,ctx)) goto err; /* 1 */ - j=1<<(window-1); - for (i=1; i 1) { - BN_init(&(val[i])); - if (!BN_mod_mul_montgomery(&(val[i]),&(val[i-1]),d,mont,ctx)) - goto err; + if (!BN_mod_mul_montgomery(d,val[0],val[0],mont,ctx)) goto err; /* 2 */ + j=1<<(window-1); + for (i=1; i>1]),mont,ctx)) + if (!BN_mod_mul_montgomery(r,r,val[wvalue>>1],mont,ctx)) goto err; /* move the 'window' down further */ @@ -626,60 +506,422 @@ int BN_mod_exp_mont(BIGNUM *rr, BIGNUM *a, const BIGNUM *p, start=0; if (wstart < 0) break; } - BN_from_montgomery(rr,r,mont,ctx); + 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); + } + + +/* 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(BIGNUM *b, int top, unsigned char *buf, int idx, int width) + { + size_t i, j; + + if (bn_wexpand(b, top) == NULL) + return 0; + while (b->top < top) + { + b->d[b->top++] = 0; + } + + for (i = 0, j=idx; i < top * sizeof b->d[0]; i++, j+=width) + { + buf[j] = ((unsigned char*)b->d)[i]; + } + + bn_correct_top(b); + return 1; + } + +static int MOD_EXP_CTIME_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; + } + +/* 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 - (((BN_ULONG)(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,idx,window,wvalue; + int top; + BIGNUM *r; + const BIGNUM *aa; + BN_MONT_CTX *mont=NULL; + + int numPowers; + unsigned char *powerbufFree=NULL; + int powerbufLen = 0; + unsigned char *powerbuf=NULL; + BIGNUM *computeTemp=NULL, *am=NULL; + + bn_check_top(a); + bn_check_top(p); + bn_check_top(m); + + top = m->top; + + if (!(m->d[0] & 1)) + { + BNerr(BN_F_BN_MOD_EXP_MONT_CONSTTIME,BN_R_CALLED_WITH_EVEN_MODULUS); + return(0); + } + bits=BN_num_bits(p); + if (bits == 0) + { + ret = BN_one(rr); + return ret; + } + + /* Initialize BIGNUM context and allocate intermediate result */ + BN_CTX_start(ctx); + r = BN_CTX_get(ctx); + if (r == NULL) goto err; + + /* 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; + } + + /* Get the window size to use with size of p. */ + window = BN_window_bits_for_ctime_exponent_size(bits); + + /* Allocate a buffer large enough to hold all of the pre-computed + * powers of a. + */ + numPowers = 1 << window; + powerbufLen = sizeof(m->d[0])*top*numPowers; + 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); + + /* Initialize the intermediate result. Do this early to save double conversion, + * once each for a^0 and intermediate result. + */ + if (!BN_to_montgomery(r,BN_value_one(),mont,ctx)) goto err; + if (!MOD_EXP_CTIME_COPY_TO_PREBUF(r, top, powerbuf, 0, numPowers)) goto err; + + /* Initialize computeTemp as a^1 with montgomery precalcs */ + computeTemp = BN_CTX_get(ctx); + am = BN_CTX_get(ctx); + if (computeTemp==NULL || am==NULL) goto err; + + if (a->neg || BN_ucmp(a,m) >= 0) + { + if (!BN_mod(am,a,m,ctx)) + goto err; + aa= am; + } + else + aa=a; + if (!BN_to_montgomery(am,aa,mont,ctx)) goto err; + if (!BN_copy(computeTemp, am)) goto err; + if (!MOD_EXP_CTIME_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) + { + for (i=2; i= 0) + { + wvalue=0; /* The 'value' of the window */ + + /* Scan the window, squaring the result as we go */ + for (i=0; itop == 1) + a %= m->d[0]; /* make sure that 'a' is reduced */ + + bits = BN_num_bits(p); + if (bits == 0) + { + 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); - for (i=0; i= 256) - window=5; /* max size of window */ - else if (bits >= 128) - window=4; - else - window=3; + d = BN_CTX_get(ctx); + val[0] = BN_CTX_get(ctx); + if(!d || !val[0]) goto err; - j=1<<(window-1); - for (i=1; i 1) + { + if (!BN_mod_mul(d,val[0],val[0],m,ctx)) + goto err; /* 2 */ + j=1<<(window-1); + for (i=1; i>1]),m,ctx)) + if (!BN_mod_mul(r,r,val[wvalue>>1],m,ctx)) goto err; /* move the 'window' down further */ @@ -742,8 +984,7 @@ int BN_mod_exp_simple(BIGNUM *r, BIGNUM *a, BIGNUM *p, BIGNUM *m, ret=1; err: BN_CTX_end(ctx); - for (i=0; i