diff options
Diffstat (limited to 'crypto/bn/bn_exp.c')
| -rw-r--r-- | crypto/bn/bn_exp.c | 1726 |
1 files changed, 867 insertions, 859 deletions
diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c index 3c043c79aa..b29df546d5 100644 --- a/crypto/bn/bn_exp.c +++ b/crypto/bn/bn_exp.c @@ -5,21 +5,21 @@ * 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: @@ -34,10 +34,10 @@ * 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 + * 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 @@ -49,7 +49,7 @@ * 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 @@ -63,7 +63,7 @@ * are met: * * 1. Redistributions of source code must retain the above copyright - * notice, this list of conditions and the following disclaimer. + * 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 @@ -109,891 +109,899 @@ * */ - #include "cryptlib.h" #include "bn_lcl.h" /* maximum precomputation table size for *variable* sliding windows */ -#define TABLE_SIZE 32 +#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_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ - BNerr(BN_F_BN_EXP,ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED); - return -1; - } - - 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; - } - } - ret=1; -err: - if (r != rr) BN_copy(r,rr); - BN_CTX_end(ctx); - bn_check_top(r); - return(ret); - } - +{ + int i, bits, ret = 0; + BIGNUM *v, *rr; + + if (BN_get_flags(p, 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 -1; + } + + 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; + } + } + ret = 1; + err: + if (r != rr) + BN_copy(r, rr); + 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] + 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.) - */ + * debug-solaris-sparcv8-gcc conf.] + * + * BN_mod_exp_recp 50 .. 70 % [AMD K6-2, Linux, debug configuration] + * 62 .. 118 % [UltraSparc, debug-solaris-sparcv8-gcc] + * + * On the Sparc, BN_mod_exp_recp was faster than BN_mod_exp_mont + * at 2048 and more bits, but at 512 and 1024 bits, it was + * slower even than the standard algorithm! + * + * "Real" timings [linux-elf, solaris-sparcv9-gcc configurations] + * should be obtained when the new Montgomery reduction code + * has been integrated into OpenSSL.) + */ #define MONT_MUL_MOD #define MONT_EXP_WORD #define RECP_MUL_MOD #ifdef MONT_MUL_MOD - /* I have finally been able to take out this pre-condition of - * the top bit being set. It was caused by an error in BN_div - * with negatives. There was also another problem when for a^b%m - * a >= m. eay 07-May-97 */ - /* if ((m->d[m->top-1]&BN_TBIT) && BN_is_odd(m)) */ - - if (BN_is_odd(m)) - { -# ifdef MONT_EXP_WORD - if (a->top == 1 && !a->neg && (BN_get_flags(p, BN_FLG_CONSTTIME) == 0)) - { - BN_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 + /* + * I have finally been able to take out this pre-condition of the top bit + * being set. It was caused by an error in BN_div with negatives. There + * was also another problem when for a^b%m a >= m. eay 07-May-97 + */ + /* if ((m->d[m->top-1]&BN_TBIT) && BN_is_odd(m)) */ + + if (BN_is_odd(m)) { +# ifdef MONT_EXP_WORD + if (a->top == 1 && !a->neg + && (BN_get_flags(p, BN_FLG_CONSTTIME) == 0)) { + BN_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); - } - + 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_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) - { - ret = BN_one(r); - return ret; - } - - BN_CTX_start(ctx); - aa = BN_CTX_get(ctx); - val[0] = BN_CTX_get(ctx); - if(!aa || !val[0]) goto err; - - BN_RECP_CTX_init(&recp); - if (m->neg) - { - /* ignore sign of 'm' */ - if (!BN_copy(aa, m)) goto err; - aa->neg = 0; - if (BN_RECP_CTX_set(&recp,aa,ctx) <= 0) goto err; - } - else - { - if (BN_RECP_CTX_set(&recp,m,ctx) <= 0) goto err; - } - - if (!BN_nnmod(val[0],a,m,ctx)) goto err; /* 1 */ - if (BN_is_zero(val[0])) - { - BN_zero(r); - ret = 1; - goto err; - } - - window = BN_window_bits_for_exponent_size(bits); - if (window > 1) - { - if (!BN_mod_mul_reciprocal(aa,val[0],val[0],&recp,ctx)) - goto err; /* 2 */ - j=1<<(window-1); - for (i=1; i<j; i++) - { - if(((val[i] = BN_CTX_get(ctx)) == NULL) || - !BN_mod_mul_reciprocal(val[i],val[i-1], - aa,&recp,ctx)) - goto err; - } - } - - start=1; /* This is used to avoid multiplication etc - * when there is only the value '1' in the - * buffer. */ - wvalue=0; /* The 'value' of the window */ - wstart=bits-1; /* The top bit of the window */ - wend=0; /* The bottom bit of the window */ - - if (!BN_one(r)) goto err; - - for (;;) - { - if (BN_is_bit_set(p,wstart) == 0) - { - if (!start) - if (!BN_mod_mul_reciprocal(r,r,r,&recp,ctx)) - goto err; - if (wstart == 0) break; - wstart--; - continue; - } - /* We now have wstart on a 'set' bit, we now need to work out - * how bit a window to do. To do this we need to scan - * forward until the last set bit before the end of the - * window */ - j=wstart; - wvalue=1; - wend=0; - for (i=1; i<window; i++) - { - if (wstart-i < 0) break; - if (BN_is_bit_set(p,wstart-i)) - { - wvalue<<=(i-wend); - wvalue|=1; - wend=i; - } - } - - /* wend is the size of the current window */ - j=wend+1; - /* add the 'bytes above' */ - if (!start) - for (i=0; i<j; i++) - { - if (!BN_mod_mul_reciprocal(r,r,r,&recp,ctx)) - goto err; - } - - /* wvalue will be an odd number < 2^window */ - if (!BN_mod_mul_reciprocal(r,r,val[wvalue>>1],&recp,ctx)) - goto err; - - /* move the 'window' down further */ - wstart-=wend+1; - wvalue=0; - start=0; - if (wstart < 0) break; - } - ret=1; -err: - BN_CTX_end(ctx); - BN_RECP_CTX_free(&recp); - bn_check_top(r); - return(ret); - } - + 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_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) { + ret = BN_one(r); + return ret; + } + + BN_CTX_start(ctx); + aa = BN_CTX_get(ctx); + val[0] = BN_CTX_get(ctx); + if (!aa || !val[0]) + goto err; + + BN_RECP_CTX_init(&recp); + if (m->neg) { + /* ignore sign of 'm' */ + if (!BN_copy(aa, m)) + goto err; + aa->neg = 0; + if (BN_RECP_CTX_set(&recp, aa, ctx) <= 0) + goto err; + } else { + if (BN_RECP_CTX_set(&recp, m, ctx) <= 0) + goto err; + } + + if (!BN_nnmod(val[0], a, m, ctx)) + goto err; /* 1 */ + if (BN_is_zero(val[0])) { + BN_zero(r); + ret = 1; + goto err; + } + + window = BN_window_bits_for_exponent_size(bits); + if (window > 1) { + if (!BN_mod_mul_reciprocal(aa, val[0], val[0], &recp, ctx)) + goto err; /* 2 */ + j = 1 << (window - 1); + for (i = 1; i < j; i++) { + if (((val[i] = BN_CTX_get(ctx)) == NULL) || + !BN_mod_mul_reciprocal(val[i], val[i - 1], aa, &recp, ctx)) + goto err; + } + } + + start = 1; /* This is used to avoid multiplication etc + * when there is only the value '1' in the + * buffer. */ + wvalue = 0; /* The 'value' of the window */ + wstart = bits - 1; /* The top bit of the window */ + wend = 0; /* The bottom bit of the window */ + + if (!BN_one(r)) + goto err; + + for (;;) { + if (BN_is_bit_set(p, wstart) == 0) { + if (!start) + if (!BN_mod_mul_reciprocal(r, r, r, &recp, ctx)) + goto err; + if (wstart == 0) + break; + wstart--; + continue; + } + /* + * We now have wstart on a 'set' bit, we now need to work out how bit + * a window to do. To do this we need to scan forward until the last + * set bit before the end of the window + */ + j = wstart; + wvalue = 1; + wend = 0; + for (i = 1; i < window; i++) { + if (wstart - i < 0) + break; + if (BN_is_bit_set(p, wstart - i)) { + wvalue <<= (i - wend); + wvalue |= 1; + wend = i; + } + } + + /* wend is the size of the current window */ + j = wend + 1; + /* add the 'bytes above' */ + if (!start) + for (i = 0; i < j; i++) { + if (!BN_mod_mul_reciprocal(r, r, r, &recp, ctx)) + goto err; + } + + /* wvalue will be an odd number < 2^window */ + if (!BN_mod_mul_reciprocal(r, r, val[wvalue >> 1], &recp, ctx)) + goto err; + + /* move the 'window' down further */ + wstart -= wend + 1; + wvalue = 0; + start = 0; + if (wstart < 0) + break; + } + ret = 1; + err: + BN_CTX_end(ctx); + BN_RECP_CTX_free(&recp); + bn_check_top(r); + return (ret); +} int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, - const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont) - { - int i,j,bits,ret=0,wstart,wend,window,wvalue; - int start=1; - BIGNUM *d,*r; - const BIGNUM *aa; - /* Table of variables obtained from 'ctx' */ - BIGNUM *val[TABLE_SIZE]; - BN_MONT_CTX *mont=NULL; - - if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0) - { - 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) - { - ret = BN_one(rr); - return ret; - } - - BN_CTX_start(ctx); - d = BN_CTX_get(ctx); - r = BN_CTX_get(ctx); - val[0] = BN_CTX_get(ctx); - if (!d || !r || !val[0]) goto err; - - /* If this is not done, things will break in the montgomery - * part */ - - if (in_mont != NULL) - mont=in_mont; - else - { - if ((mont=BN_MONT_CTX_new()) == NULL) goto err; - if (!BN_MONT_CTX_set(mont,m,ctx)) goto err; - } - - if (a->neg || BN_ucmp(a,m) >= 0) - { - if (!BN_nnmod(val[0],a,m,ctx)) - goto err; - aa= val[0]; - } - else - aa=a; - if (BN_is_zero(aa)) - { - BN_zero(rr); - ret = 1; - goto err; - } - if (!BN_to_montgomery(val[0],aa,mont,ctx)) goto err; /* 1 */ - - window = BN_window_bits_for_exponent_size(bits); - if (window > 1) - { - if (!BN_mod_mul_montgomery(d,val[0],val[0],mont,ctx)) goto err; /* 2 */ - j=1<<(window-1); - for (i=1; i<j; i++) - { - if(((val[i] = BN_CTX_get(ctx)) == NULL) || - !BN_mod_mul_montgomery(val[i],val[i-1], - d,mont,ctx)) - goto err; - } - } - - start=1; /* This is used to avoid multiplication etc - * when there is only the value '1' in the - * buffer. */ - wvalue=0; /* The 'value' of the window */ - wstart=bits-1; /* The top bit of the window */ - wend=0; /* The bottom bit of the window */ - - if (!BN_to_montgomery(r,BN_value_one(),mont,ctx)) goto err; - for (;;) - { - if (BN_is_bit_set(p,wstart) == 0) - { - if (!start) - { - if (!BN_mod_mul_montgomery(r,r,r,mont,ctx)) - goto err; - } - if (wstart == 0) break; - wstart--; - continue; - } - /* We now have wstart on a 'set' bit, we now need to work out - * how bit a window to do. To do this we need to scan - * forward until the last set bit before the end of the - * window */ - j=wstart; - wvalue=1; - wend=0; - for (i=1; i<window; i++) - { - if (wstart-i < 0) break; - if (BN_is_bit_set(p,wstart-i)) - { - wvalue<<=(i-wend); - wvalue|=1; - wend=i; - } - } - - /* wend is the size of the current window */ - j=wend+1; - /* add the 'bytes above' */ - if (!start) - for (i=0; i<j; i++) - { - if (!BN_mod_mul_montgomery(r,r,r,mont,ctx)) - goto err; - } - - /* wvalue will be an odd number < 2^window */ - if (!BN_mod_mul_montgomery(r,r,val[wvalue>>1],mont,ctx)) - goto err; - - /* move the 'window' down further */ - wstart-=wend+1; - wvalue=0; - start=0; - if (wstart < 0) break; - } - if (!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)))) + 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) { + 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) { + ret = BN_one(rr); + return ret; + } + + BN_CTX_start(ctx); + d = BN_CTX_get(ctx); + r = BN_CTX_get(ctx); + val[0] = BN_CTX_get(ctx); + if (!d || !r || !val[0]) + goto err; + + /* + * If this is not done, things will break in the montgomery part + */ + + if (in_mont != NULL) + mont = in_mont; + else { + if ((mont = BN_MONT_CTX_new()) == NULL) + goto err; + if (!BN_MONT_CTX_set(mont, m, ctx)) + goto err; + } + + if (a->neg || BN_ucmp(a, m) >= 0) { + if (!BN_nnmod(val[0], a, m, ctx)) + goto err; + aa = val[0]; + } else + aa = a; + if (BN_is_zero(aa)) { + BN_zero(rr); + ret = 1; + goto err; + } + if (!BN_to_montgomery(val[0], aa, mont, ctx)) + goto err; /* 1 */ + + window = BN_window_bits_for_exponent_size(bits); + if (window > 1) { + if (!BN_mod_mul_montgomery(d, val[0], val[0], mont, ctx)) + goto err; /* 2 */ + j = 1 << (window - 1); + for (i = 1; i < j; i++) { + if (((val[i] = BN_CTX_get(ctx)) == NULL) || + !BN_mod_mul_montgomery(val[i], val[i - 1], d, mont, ctx)) + goto err; + } + } + + start = 1; /* This is used to avoid multiplication etc + * when there is only the value '1' in the + * buffer. */ + wvalue = 0; /* The 'value' of the window */ + wstart = bits - 1; /* The top bit of the window */ + wend = 0; /* The bottom bit of the window */ + + if (!BN_to_montgomery(r, BN_value_one(), mont, ctx)) + goto err; + for (;;) { + if (BN_is_bit_set(p, wstart) == 0) { + if (!start) { + if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) + goto err; + } + if (wstart == 0) + break; + wstart--; + continue; + } + /* + * We now have wstart on a 'set' bit, we now need to work out how bit + * a window to do. To do this we need to scan forward until the last + * set bit before the end of the window + */ + j = wstart; + wvalue = 1; + wend = 0; + for (i = 1; i < window; i++) { + if (wstart - i < 0) + break; + if (BN_is_bit_set(p, wstart - i)) { + wvalue <<= (i - wend); + wvalue |= 1; + wend = i; + } + } + + /* wend is the size of the current window */ + j = wend + 1; + /* add the 'bytes above' */ + if (!start) + for (i = 0; i < j; i++) { + if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) + goto err; + } + + /* wvalue will be an odd number < 2^window */ + if (!BN_mod_mul_montgomery(r, r, val[wvalue >> 1], mont, ctx)) + goto err; + + /* move the 'window' down further */ + wstart -= wend + 1; + wvalue = 0; + start = 0; + if (wstart < 0) + break; + } + if (!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. + */ -/* 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/) +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.daemong-consideredperthreading-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<numPowers; i++) - { - /* Calculate a^i = a^(i-1) * a */ - if (!BN_mod_mul_montgomery(computeTemp,am,computeTemp,mont,ctx)) - goto err; - if (!MOD_EXP_CTIME_COPY_TO_PREBUF(computeTemp, top, powerbuf, i, numPowers)) goto err; - } - } - - /* Adjust the number of bits up to a multiple of the window size. - * If the exponent length is not a multiple of the window size, then - * this pads the most significant bits with zeros to normalize the - * scanning loop to there's no special cases. - * - * * NOTE: Making the window size a power of two less than the native - * * word size ensures that the padded bits won't go past the last - * * word in the internal BIGNUM structure. Going past the end will - * * still produce the correct result, but causes a different branch - * * to be taken in the BN_is_bit_set function. - */ - bits = ((bits+window-1)/window)*window; - idx=bits-1; /* The top bit of the window */ - - /* Scan the exponent one window at a time starting from the most - * significant bits. - */ - while (idx >= 0) - { - wvalue=0; /* The 'value' of the window */ - - /* Scan the window, squaring the result as we go */ - for (i=0; i<window; i++,idx--) - { - if (!BN_mod_mul_montgomery(r,r,r,mont,ctx)) goto err; - wvalue = (wvalue<<1)+BN_is_bit_set(p,idx); - } - - /* Fetch the appropriate pre-computed value from the pre-buf */ - if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(computeTemp, top, powerbuf, wvalue, numPowers)) goto err; - - /* Multiply the result into the intermediate result */ - if (!BN_mod_mul_montgomery(r,r,computeTemp,mont,ctx)) goto err; - } - - /* Convert the final result from montgomery to standard format */ - if (!BN_from_montgomery(rr,r,mont,ctx)) goto err; - ret=1; -err: - if ((in_mont == NULL) && (mont != NULL)) BN_MONT_CTX_free(mont); - if (powerbuf!=NULL) - { - OPENSSL_cleanse(powerbuf,powerbufLen); - OPENSSL_free(powerbufFree); - } - if (am!=NULL) BN_clear(am); - if (computeTemp!=NULL) BN_clear(computeTemp); - BN_CTX_end(ctx); - return(ret); - } + 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); + |