diff options
Diffstat (limited to 'openssl/crypto/bn/bn_exp.c')
| -rw-r--r-- | openssl/crypto/bn/bn_exp.c | 990 |
1 files changed, 990 insertions, 0 deletions
diff --git a/openssl/crypto/bn/bn_exp.c b/openssl/crypto/bn/bn_exp.c new file mode 100644 index 000000000..70a33f0d9 --- /dev/null +++ b/openssl/crypto/bn/bn_exp.c @@ -0,0 +1,990 @@ +/* crypto/bn/bn_exp.c */ +/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) + * All rights reserved. + * + * This package is an SSL implementation written + * by Eric Young (eay@cryptsoft.com). + * The implementation was written so as to conform with Netscapes SSL. + * + * This library is free for commercial and non-commercial use as long as + * the following conditions are aheared to. The following conditions + * apply to all code found in this distribution, be it the RC4, RSA, + * lhash, DES, etc., code; not just the SSL code. The SSL documentation + * included with this distribution is covered by the same copyright terms + * except that the holder is Tim Hudson (tjh@cryptsoft.com). + * + * Copyright remains Eric Young's, and as such any Copyright notices in + * the code are not to be removed. + * If this package is used in a product, Eric Young should be given attribution + * as the author of the parts of the library used. + * This can be in the form of a textual message at program startup or + * in documentation (online or textual) provided with the package. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * "This product includes cryptographic software written by + * Eric Young (eay@cryptsoft.com)" + * The word 'cryptographic' can be left out if the rouines from the library + * being used are not cryptographic related :-). + * 4. If you include any Windows specific code (or a derivative thereof) from + * the apps directory (application code) you must include an acknowledgement: + * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" + * + * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * The licence and distribution terms for any publically available version or + * derivative of this code cannot be changed. i.e. this code cannot simply be + * copied and put under another distribution licence + * [including the GNU Public Licence.] + */ +/* ==================================================================== + * Copyright (c) 1998-2005 The OpenSSL Project. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * + * 3. All advertising materials mentioning features or use of this + * software must display the following acknowledgment: + * "This product includes software developed by the OpenSSL Project + * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" + * + * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to + * endorse or promote products derived from this software without + * prior written permission. For written permission, please contact + * openssl-core@openssl.org. + * + * 5. Products derived from this software may not be called "OpenSSL" + * nor may "OpenSSL" appear in their names without prior written + * permission of the OpenSSL Project. + * + * 6. Redistributions of any form whatsoever must retain the following + * acknowledgment: + * "This product includes software developed by the OpenSSL Project + * for use in the OpenSSL Toolkit (http://www.openssl.org/)" + * + * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY + * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR + * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR + * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; + * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, + * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED + * OF THE POSSIBILITY OF SUCH DAMAGE. + * ==================================================================== + * + * This product includes cryptographic software written by Eric Young + * (eay@cryptsoft.com). This product includes software written by Tim + * Hudson (tjh@cryptsoft.com). + * + */ + + +#include "cryptlib.h" +#include "bn_lcl.h" + +/* 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_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; + 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<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] + * 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)) + { +# 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); } +#else + { 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_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)))) + +/* 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<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); + } + +int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p, + const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont) + { + BN_MONT_CTX *mont = NULL; + int b, bits, ret=0; + int r_is_one; + BN_ULONG w, next_w; + BIGNUM *d, *r, *t; + BIGNUM *swap_tmp; +#define BN_MOD_MUL_WORD(r, w, m) \ + (BN_mul_word(r, (w)) && \ + (/* BN_ucmp(r, (m)) < 0 ? 1 :*/ \ + (BN_mod(t, r, m, ctx) && (swap_tmp = r, r = t, t = swap_tmp, 1)))) + /* BN_MOD_MUL_WORD is only used with 'w' large, + * so the BN_ucmp test is probably more overhead + * than always using BN_mod (which uses BN_copy if + * a similar test returns true). */ + /* We can use BN_mod and do not need BN_nnmod because our + * accumulator is never negative (the result of BN_mod does + * not depend on the sign of the modulus). + */ +#define BN_TO_MONTGOMERY_WORD(r, w, mont) \ + (BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont), ctx)) + + if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0) + { + /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ + 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) + { + 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); + 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; + 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_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ + BNerr(BN_F_BN_MOD_EXP_SIMPLE,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); + d = BN_CTX_get(ctx); + val[0] = BN_CTX_get(ctx); + if(!d || !val[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(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); + } + |