X-Git-Url: https://git.openssl.org/gitweb/?p=openssl.git;a=blobdiff_plain;f=crypto%2Fbn%2Fbn_exp.c;h=66feddcf962daf67bf21174f6caad2d86c3830c7;hp=462d4dbc4364c64fea091eabe3240fbd0dbe1e45;hb=a9009e518ca03f35a1e1a0858faf81865f8eff1e;hpb=d870740cd75dd4f0cb66fb8c32653a7d47369706 diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c index 462d4dbc43..66feddcf96 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 @@ -49,21 +49,21 @@ * 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) 1998-2000 The OpenSSL Project. All rights reserved. + * 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. + * 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 @@ -109,645 +109,1285 @@ * */ - -#include "cryptlib.h" +#include "internal/cryptlib.h" #include "bn_lcl.h" -#define TABLE_SIZE 32 +#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 + +/* 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; - - BN_CTX_start(ctx); - if ((r == a) || (r == p)) - rr = BN_CTX_get(ctx); - else - rr = r; - if ((v = BN_CTX_get(ctx)) == 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= 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_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,ts=0; - BIGNUM *aa; - BIGNUM val[TABLE_SIZE]; - BN_RECP_CTX recp; - - bits=BN_num_bits(p); - - if (bits == 0) - { - ret = BN_one(r); - return ret; - } - - BN_CTX_start(ctx); - if ((aa = BN_CTX_get(ctx)) == 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; - } - - BN_init(&(val[0])); - ts=1; - - if (!BN_nnmod(&(val[0]),a,m,ctx)) goto err; /* 1 */ - if (BN_is_zero(&(val[0]))) - { - ret = BN_zero(r); - 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>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); - for (i=0; ineg) { + /* 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,ts=0; - BIGNUM *d,*r; - const BIGNUM *aa; - BIGNUM val[TABLE_SIZE]; - BN_MONT_CTX *mont=NULL; - - bn_check_top(a); - bn_check_top(p); - bn_check_top(m); - - if (!(m->d[0] & 1)) - { - 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); - if (d == NULL || r == 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; - } - - BN_init(&val[0]); - ts=1; - 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)) - { - ret = BN_zero(rr); - 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>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); - for (i=0; ineg || BN_ucmp(a, m) >= 0) { + if (!BN_nnmod(val[0], a, m, ctx)) + goto err; + aa = val[0]; + } else + aa = a; + if (BN_is_zero(aa)) { + BN_zero(rr); + ret = 1; + goto err; + } + if (!BN_to_montgomery(val[0], aa, mont, ctx)) + goto err; /* 1 */ + + window = BN_window_bits_for_exponent_size(bits); + if (window > 1) { + if (!BN_mod_mul_montgomery(d, val[0], val[0], mont, ctx)) + goto err; /* 2 */ + j = 1 << (window - 1); + for (i = 1; i < j; i++) { + if (((val[i] = BN_CTX_get(ctx)) == NULL) || + !BN_mod_mul_montgomery(val[i], val[i - 1], d, mont, ctx)) + goto err; + } + } + + start = 1; /* This is used to avoid multiplication etc + * when there is only the value '1' in the + * buffer. */ + wvalue = 0; /* The 'value' of the window */ + wstart = bits - 1; /* The top bit of the window */ + wend = 0; /* The bottom bit of the window */ + +#if 1 /* by Shay Gueron's suggestion */ + j = m->top; /* borrow j */ + if (m->d[j - 1] & (((BN_ULONG)1) << (BN_BITS2 - 1))) { + if (bn_wexpand(r, j) == NULL) + goto err; + /* 2^(top*BN_BITS2) - m */ + r->d[0] = (0 - m->d[0]) & BN_MASK2; + for (i = 1; i < j; i++) + r->d[i] = (~m->d[i]) & BN_MASK2; + r->top = j; + /* + * Upper words will be zero if the corresponding words of 'm' were + * 0xfff[...], so decrement r->top accordingly. + */ + bn_correct_top(r); + } else +#endif + if (!BN_to_montgomery(r, BN_value_one(), mont, ctx)) + goto err; + for (;;) { + if (BN_is_bit_set(p, wstart) == 0) { + if (!start) { + if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) + goto err; + } + if (wstart == 0) + break; + wstart--; + continue; + } + /* + * We now have wstart on a 'set' bit, we now need to work out how bit + * a window to do. To do this we need to scan forward until the last + * set bit before the end of the window + */ + j = wstart; + wvalue = 1; + wend = 0; + for (i = 1; i < window; i++) { + if (wstart - i < 0) + break; + if (BN_is_bit_set(p, wstart - i)) { + wvalue <<= (i - wend); + wvalue |= 1; + wend = i; + } + } + + /* wend is the size of the current window */ + j = wend + 1; + /* add the 'bytes above' */ + if (!start) + for (i = 0; i < j; i++) { + if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) + goto err; + } + + /* wvalue will be an odd number < 2^window */ + if (!BN_mod_mul_montgomery(r, r, val[wvalue >> 1], mont, ctx)) + goto err; + + /* move the 'window' down further */ + wstart -= wend + 1; + wvalue = 0; + start = 0; + if (wstart < 0) + break; + } +#if defined(SPARC_T4_MONT) + if (OPENSSL_sparcv9cap_P[0] & (SPARCV9_VIS3 | SPARCV9_PREFER_FPU)) { + j = mont->N.top; /* borrow j */ + val[0]->d[0] = 1; /* borrow val[0] */ + for (i = 1; i < j; i++) + val[0]->d[i] = 0; + val[0]->top = j; + if (!BN_mod_mul_montgomery(rr, r, val[0], mont, ctx)) + goto err; + } else +#endif + if (!BN_from_montgomery(rr, r, mont, ctx)) + goto err; + ret = 1; + err: + if (in_mont == NULL) + BN_MONT_CTX_free(mont); + BN_CTX_end(ctx); + bn_check_top(rr); + return (ret); +} + +#if defined(SPARC_T4_MONT) +static BN_ULONG bn_get_bits(const BIGNUM *a, int bitpos) +{ + BN_ULONG ret = 0; + int wordpos; + + wordpos = bitpos / BN_BITS2; + bitpos %= BN_BITS2; + if (wordpos >= 0 && wordpos < a->top) { + ret = a->d[wordpos] & BN_MASK2; + if (bitpos) { + ret >>= bitpos; + if (++wordpos < a->top) + ret |= a->d[wordpos] << (BN_BITS2 - bitpos); + } + } + + return ret & BN_MASK2; +} +#endif + +/* + * BN_mod_exp_mont_consttime() stores the precomputed powers in a specific + * layout so that accessing any of these table values shows the same access + * pattern as far as cache lines are concerned. The following functions are + * used to transfer a BIGNUM from/to that table. + */ + +static int MOD_EXP_CTIME_COPY_TO_PREBUF(const BIGNUM *b, int top, + unsigned char *buf, int idx, + int 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 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 - (((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.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, window, wvalue; + int top; + BN_MONT_CTX *mont = NULL; + + int numPowers; + unsigned char *powerbufFree = NULL; + int powerbufLen = 0; + unsigned char *powerbuf = NULL; + BIGNUM tmp, am; +#if defined(SPARC_T4_MONT) + unsigned int t4 = 0; +#endif + + bn_check_top(a); + bn_check_top(p); + bn_check_top(m); + + if (!BN_is_odd(m)) { + BNerr(BN_F_BN_MOD_EXP_MONT_CONSTTIME, BN_R_CALLED_WITH_EVEN_MODULUS); + return (0); + } + + top = m->top; + + bits = BN_num_bits(p); + if (bits == 0) { + ret = BN_one(rr); + return ret; + } + + BN_CTX_start(ctx); + + /* + * Allocate a montgomery context if it was not supplied by the caller. If + * this is not done, things will break in the montgomery part. + */ + if (in_mont != NULL) + mont = in_mont; + else { + if ((mont = BN_MONT_CTX_new()) == NULL) + goto err; + if (!BN_MONT_CTX_set(mont, m, ctx)) + goto err; + } + +#ifdef RSAZ_ENABLED + /* + * If the size of the operands allow it, perform the optimized + * RSAZ exponentiation. For further information see + * crypto/bn/rsaz_exp.c and accompanying assembly modules. + */ + if ((16 == a->top) && (16 == p->top) && (BN_num_bits(m) == 1024) + && rsaz_avx2_eligible()) { + if (NULL == bn_wexpand(rr, 16)) + goto err; + RSAZ_1024_mod_exp_avx2(rr->d, a->d, p->d, m->d, mont->RR.d, + mont->n0[0]); + rr->top = 16; + rr->neg = 0; + bn_correct_top(rr); + ret = 1; + goto err; + } else if ((8 == a->top) && (8 == p->top) && (BN_num_bits(m) == 512)) { + if (NULL == bn_wexpand(rr, 8)) + goto err; + RSAZ_512_mod_exp(rr->d, a->d, p->d, m->d, mont->n0[0], mont->RR.d); + rr->top = 8; + rr->neg = 0; + bn_correct_top(rr); + ret = 1; + goto err; + } +#endif + + /* Get the window size to use with size of p. */ + window = BN_window_bits_for_ctime_exponent_size(bits); +#if defined(SPARC_T4_MONT) + if (window >= 5 && (top & 15) == 0 && top <= 64 && + (OPENSSL_sparcv9cap_P[1] & (CFR_MONTMUL | CFR_MONTSQR)) == + (CFR_MONTMUL | CFR_MONTSQR) && (t4 = OPENSSL_sparcv9cap_P[0])) + window = 5; + else +#endif +#if defined(OPENSSL_BN_ASM_MONT5) + if (window >= 5) { + window = 5; /* ~5% improvement for RSA2048 sign, and even + * for RSA4096 */ + if ((top & 7) == 0) + powerbufLen += 2 * top * sizeof(m->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_montgomery(&tmp, BN_value_one(), mont, ctx)) + goto err; + + /* prepare a^1 in Montgomery domain */ + if (a->neg || BN_ucmp(a, m) >= 0) { + if (!BN_mod(&am, a, m, ctx)) + goto err; + if (!BN_to_montgomery(&am, &am, mont, ctx)) + goto err; + } else if (!BN_to_montgomery(&am, a, mont, ctx)) + goto err; + +#if defined(SPARC_T4_MONT) + if (t4) { + typedef int (*bn_pwr5_mont_f) (BN_ULONG *tp, const BN_ULONG *np, + const BN_ULONG *n0, const void *table, + int power, int bits); + int bn_pwr5_mont_t4_8(BN_ULONG *tp, const BN_ULONG *np, + const BN_ULONG *n0, const void *table, + int power, int bits); + int bn_pwr5_mont_t4_16(BN_ULONG *tp, const BN_ULONG *np, + const BN_ULONG *n0, const void *table, + int power, int bits); + int bn_pwr5_mont_t4_24(BN_ULONG *tp, const BN_ULONG *np, + const BN_ULONG *n0, const void *table, + int power, int bits); + int bn_pwr5_mont_t4_32(BN_ULONG *tp, const BN_ULONG *np, + const BN_ULONG *n0, const void *table, + int power, int bits); + static const bn_pwr5_mont_f pwr5_funcs[4] = { + bn_pwr5_mont_t4_8, bn_pwr5_mont_t4_16, + bn_pwr5_mont_t4_24, bn_pwr5_mont_t4_32 + }; + bn_pwr5_mont_f pwr5_worker = pwr5_funcs[top / 16 - 1]; + + typedef int (*bn_mul_mont_f) (BN_ULONG *rp, const BN_ULONG *ap, + const void *bp, const BN_ULONG *np, + const BN_ULONG *n0); + int bn_mul_mont_t4_8(BN_ULONG *rp, const BN_ULONG *ap, const void *bp, + const BN_ULONG *np, const BN_ULONG *n0); + int bn_mul_mont_t4_16(BN_ULONG *rp, const BN_ULONG *ap, + const void *bp, const BN_ULONG *np, + const BN_ULONG *n0); + int bn_mul_mont_t4_24(BN_ULONG *rp, const BN_ULONG *ap, + const void *bp, const BN_ULONG *np, + const BN_ULONG *n0); + int bn_mul_mont_t4_32(BN_ULONG *rp, const BN_ULONG *ap, + const void *bp, const BN_ULONG *np, + const BN_ULONG *n0); + static const bn_mul_mont_f mul_funcs[4] = { + bn_mul_mont_t4_8, bn_mul_mont_t4_16, + bn_mul_mont_t4_24, bn_mul_mont_t4_32 + }; + bn_mul_mont_f mul_worker = mul_funcs[top / 16 - 1]; + + void bn_mul_mont_vis3(BN_ULONG *rp, const BN_ULONG *ap, + const void *bp, const BN_ULONG *np, + const BN_ULONG *n0, int num); + void bn_mul_mont_t4(BN_ULONG *rp, const BN_ULONG *ap, + const void *bp, const BN_ULONG *np, + const BN_ULONG *n0, int num); + void bn_mul_mont_gather5_t4(BN_ULONG *rp, const BN_ULONG *ap, + const void *table, const BN_ULONG *np, + const BN_ULONG *n0, int num, int power); + void bn_flip_n_scatter5_t4(const BN_ULONG *inp, size_t num, + void *table, size_t power); + void bn_gather5_t4(BN_ULONG *out, size_t num, + void *table, size_t power); + void bn_flip_t4(BN_ULONG *dst, BN_ULONG *src, size_t num); + + BN_ULONG *np = mont->N.d, *n0 = mont->n0; + int stride = 5 * (6 - (top / 16 - 1)); /* multiple of 5, but less + * than 32 */ + + /* + * BN_to_montgomery can contaminate words above .top [in + * BN_DEBUG[_DEBUG] build]... + */ + for (i = am.top; i < top; i++) + am.d[i] = 0; + for (i = tmp.top; i < top; i++) + tmp.d[i] = 0; + + bn_flip_n_scatter5_t4(tmp.d, top, powerbuf, 0); + bn_flip_n_scatter5_t4(am.d, top, powerbuf, 1); + if (!(*mul_worker) (tmp.d, am.d, am.d, np, n0) && + !(*mul_worker) (tmp.d, am.d, am.d, np, n0)) + bn_mul_mont_vis3(tmp.d, am.d, am.d, np, n0, top); + bn_flip_n_scatter5_t4(tmp.d, top, powerbuf, 2); + + for (i = 3; i < 32; i++) { + /* Calculate a^i = a^(i-1) * a */ + if (!(*mul_worker) (tmp.d, tmp.d, am.d, np, n0) && + !(*mul_worker) (tmp.d, tmp.d, am.d, np, n0)) + bn_mul_mont_vis3(tmp.d, tmp.d, am.d, np, n0, top); + bn_flip_n_scatter5_t4(tmp.d, top, powerbuf, i); + } + + /* switch to 64-bit domain */ + np = alloca(top * sizeof(BN_ULONG)); + top /= 2; + bn_flip_t4(np, mont->N.d, top); + + bits--; + for (wvalue = 0, i = bits % 5; i >= 0; i--, bits--) + wvalue = (wvalue << 1) + BN_is_bit_set(p, bits); + bn_gather5_t4(tmp.d, top, powerbuf, wvalue); + + /* + * Scan the exponent one window at a time starting from the most + * significant bits. + */ + while (bits >= 0) { + if (bits < stride) + stride = bits + 1; + bits -= stride; + wvalue = bn_get_bits(p, bits + 1); + + if ((*pwr5_worker) (tmp.d, np, n0, powerbuf, wvalue, stride)) + continue; + /* retry once and fall back */ + if ((*pwr5_worker) (tmp.d, np, n0, powerbuf, wvalue, stride)) + continue; + + bits += stride - 5; + wvalue >>= stride - 5; + wvalue &= 31; + bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top); + bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top); + bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top); + bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top); + bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top); + bn_mul_mont_gather5_t4(tmp.d, tmp.d, powerbuf, np, n0, top, + wvalue); + } + + bn_flip_t4(tmp.d, tmp.d, top); + top *= 2; + /* back to 32-bit domain */ + tmp.top = top; + bn_correct_top(&tmp); + OPENSSL_cleanse(np, top * sizeof(BN_ULONG)); + } else +#endif +#if defined(OPENSSL_BN_ASM_MONT5) + if (window == 5 && top > 1) { + /* + * This optimization uses ideas from http://eprint.iacr.org/2011/239, + * specifically optimization of cache-timing attack countermeasures + * and pre-computation optimization. + */ + + /* + * Dedicated window==4 case improves 512-bit RSA sign by ~15%, but as + * 512-bit RSA is hardly relevant, we omit it to spare size... + */ + void bn_mul_mont_gather5(BN_ULONG *rp, const BN_ULONG *ap, + const void *table, const BN_ULONG *np, + const BN_ULONG *n0, int num, int power); + void bn_scatter5(const BN_ULONG *inp, size_t num, + void *table, size_t power); + void bn_gather5(BN_ULONG *out, size_t num, void *table, size_t power); + void bn_power5(BN_ULONG *rp, const BN_ULONG *ap, + const void *table, const BN_ULONG *np, + const BN_ULONG *n0, int num, int power); + int bn_get_bits5(const BN_ULONG *ap, int off); + int bn_from_montgomery(BN_ULONG *rp, const BN_ULONG *ap, + const BN_ULONG *not_used, const BN_ULONG *np, + const BN_ULONG *n0, int num); + + BN_ULONG *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); + +# if 0 + for (i = 3; i < 32; i++) { + /* Calculate a^i = a^(i-1) * a */ + bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np2, 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, 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); + } +# endif + bits--; + for (wvalue = 0, i = bits % 5; i >= 0; i--, bits--) + wvalue = (wvalue << 1) + BN_is_bit_set(p, bits); + bn_gather5(tmp.d, top, powerbuf, wvalue); + + /* + * Scan the exponent one window at a time starting from the most + * significant bits. + */ + if (top & 7) + while (bits >= 0) { + for (wvalue = 0, i = 0; i < 5; i++, bits--) + wvalue = (wvalue << 1) + BN_is_bit_set(p, bits); + + bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); + bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); + bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); + bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); + bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); + bn_mul_mont_gather5(tmp.d, tmp.d, powerbuf, np, n0, top, + wvalue); + } else { + while (bits >= 0) { + wvalue = bn_get_bits5(p->d, bits - 4); + bits -= 5; + bn_power5(tmp.d, tmp.d, powerbuf, 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 (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 0, numPowers)) + 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) { + if (!BN_mod_mul_montgomery(&tmp, &am, &am, mont, ctx)) + goto err; + if (!MOD_EXP_CTIME_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)) + goto err; + if (!MOD_EXP_CTIME_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 (!MOD_EXP_CTIME_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 (!MOD_EXP_CTIME_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 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 *d, *r, *t; - BIGNUM *swap_tmp; +{ + 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). - */ + (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)) - - bn_check_top(p); - bn_check_top(m); - - if (m->top == 0 || !(m->d[0] & 1)) - { - BNerr(BN_F_BN_MOD_EXP_MONT_WORD,BN_R_CALLED_WITH_EVEN_MODULUS); - return(0); - } - if (m->top == 1) - a %= m->d[0]; /* make sure that 'a' is reduced */ - - bits = BN_num_bits(p); - if (bits == 0) - { - ret = BN_one(rr); - return ret; - } - if (a == 0) - { - ret = BN_zero(rr); - return ret; - } - - BN_CTX_start(ctx); - d = BN_CTX_get(ctx); - r = BN_CTX_get(ctx); - t = BN_CTX_get(ctx); - if (d == NULL || r == NULL || t == NULL) goto err; - - if (in_mont != NULL) - mont=in_mont; - else - { - if ((mont = BN_MONT_CTX_new()) == NULL) goto err; - if (!BN_MONT_CTX_set(mont, m, ctx)) goto err; - } - - r_is_one = 1; /* except for Montgomery factor */ - - /* bits-1 >= 0 */ - - /* The result is accumulated in the product r*w. */ - w = a; /* bit 'bits-1' of 'p' is always set */ - for (b = bits-2; b >= 0; b--) - { - /* First, square r*w. */ - next_w = w*w; - if ((next_w/w) != w) /* overflow */ - { - if (r_is_one) - { - if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) goto err; - r_is_one = 0; - } - else - { - if (!BN_MOD_MUL_WORD(r, w, m)) goto err; - } - next_w = 1; - } - w = next_w; - if (!r_is_one) - { - if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) goto err; - } - - /* Second, multiply r*w by 'a' if exponent bit is set. */ - if (BN_is_bit_set(p, b)) - { - next_w = w*a; - if ((next_w/a) != w) /* overflow */ - { - if (r_is_one) - { - if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) goto err; - r_is_one = 0; - } - else - { - if (!BN_MOD_MUL_WORD(r, w, m)) goto err; - } - next_w = a; - } - w = next_w; - } - } - - /* Finally, set r:=r*w. */ - if (w != 1) - { - if (r_is_one) - { - if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) goto err; - r_is_one = 0; - } - else - { - if (!BN_MOD_MUL_WORD(r, w, m)) goto err; - } - } - - if (r_is_one) /* can happen only if a == 1*/ - { - if (!BN_one(rr)) goto err; - } - else - { - if (!BN_from_montgomery(rr, r, mont, ctx)) goto err; - } - ret = 1; -err: - if ((in_mont == NULL) && (mont != NULL)) BN_MONT_CTX_free(mont); - BN_CTX_end(ctx); - bn_check_top(rr); - return(ret); - } - + (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() */ + BNerr(BN_F_BN_MOD_EXP_MONT_WORD, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED); + return -1; + } + + bn_check_top(p); + bn_check_top(m); + + if (!BN_is_odd(m)) { + BNerr(BN_F_BN_MOD_EXP_MONT_WORD, BN_R_CALLED_WITH_EVEN_MODULUS); + return (0); + } + if (m->top == 1) + a %= m->d[0]; /* make sure that 'a' is reduced */ + + bits = BN_num_bits(p); + if (bits == 0) { + /* x**0 mod 1 is still zero. */ + if (BN_is_one(m)) { + ret = 1; + BN_zero(rr); + } else + ret = BN_one(rr); + return ret; + } + if (a == 0) { + BN_zero(rr); + ret = 1; + return ret; + } + + BN_CTX_start(ctx); + d = BN_CTX_get(ctx); + r = BN_CTX_get(ctx); + t = BN_CTX_get(ctx); + if (d == NULL || r == NULL || t == NULL) + goto err; + + if (in_mont != NULL) + mont = in_mont; + else { + if ((mont = BN_MONT_CTX_new()) == NULL) + goto err; + if (!BN_MONT_CTX_set(mont, m, ctx)) + goto err; + } + + r_is_one = 1; /* except for Montgomery factor */ + + /* bits-1 >= 0 */ + + /* The result is accumulated in the product r*w. */ + w = a; /* bit 'bits-1' of 'p' is always set */ + for (b = bits - 2; b >= 0; b--) { + /* First, square r*w. */ + next_w = w * w; + if ((next_w / w) != w) { /* overflow */ + if (r_is_one) { + if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) + goto err; + r_is_one = 0; + } else { + if (!BN_MOD_MUL_WORD(r, w, m)) + goto err; + } + next_w = 1; + } + w = next_w; + if (!r_is_one) { + if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) + goto err; + } + + /* Second, multiply r*w by 'a' if exponent bit is set. */ + if (BN_is_bit_set(p, b)) { + next_w = w * a; + if ((next_w / a) != w) { /* overflow */ + if (r_is_one) { + if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) + goto err; + r_is_one = 0; + } else { + if (!BN_MOD_MUL_WORD(r, w, m)) + goto err; + } + next_w = a; + } + w = next_w; + } + } + + /* Finally, set r:=r*w. */ + if (w != 1) { + if (r_is_one) { + if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) + goto err; + r_is_one = 0; + } else { + if (!BN_MOD_MUL_WORD(r, w, m)) + goto err; + } + } + + if (r_is_one) { /* can happen only if a == 1 */ + if (!BN_one(rr)) + goto err; + } else { + if (!BN_from_montgomery(rr, r, mont, ctx)) + goto err; + } + ret = 1; + err: + if (in_mont == NULL) + BN_MONT_CTX_free(mont); + BN_CTX_end(ctx); + bn_check_top(rr); + return (ret); +} /* The old fallback, simple version :-) */ -int BN_mod_exp_simple(BIGNUM *r, - const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, - BN_CTX *ctx) - { - int i,j,bits,ret=0,wstart,wend,window,wvalue,ts=0; - int start=1; - BIGNUM *d; - BIGNUM val[TABLE_SIZE]; - - bits=BN_num_bits(p); - - if (bits == 0) - { - ret = BN_one(r); - return ret; - } - - BN_CTX_start(ctx); - if ((d = BN_CTX_get(ctx)) == NULL) goto err; - - BN_init(&(val[0])); - ts=1; - if (!BN_nnmod(&(val[0]),a,m,ctx)) goto err; /* 1 */ - if (BN_is_zero(&(val[0]))) - { - ret = BN_zero(r); - 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>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); - for (i=0; i 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); +}