* 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 <stdio.h>
#include "cryptlib.h"
#include "bn_lcl.h"
-#define TABLE_SIZE 16
-
-/* slow but works */
-int BN_mod_mul(BIGNUM *ret, BIGNUM *a, BIGNUM *b, const BIGNUM *m, BN_CTX *ctx)
- {
- BIGNUM *t;
- int r=0;
-
- bn_check_top(a);
- bn_check_top(b);
- bn_check_top(m);
-
- t= &(ctx->bn[ctx->tos++]);
- if (a == b)
- { if (!BN_sqr(t,a,ctx)) goto err; }
- else
- { if (!BN_mul(t,a,b,ctx)) goto err; }
- if (!BN_mod(ret,t,m,ctx)) goto err;
- r=1;
-err:
- ctx->tos--;
- return(r);
- }
+/* maximum precomputation table size for *variable* sliding windows */
+#define TABLE_SIZE 32
-#if 0
/* this one works - simple but works */
-int BN_mod_exp(BIGNUM *r, BIGNUM *a, BIGNUM *p, BIGNUM *m, BN_CTX *ctx)
+int BN_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
{
int i,bits,ret=0;
- BIGNUM *v,*tmp;
-
- v= &(ctx->bn[ctx->tos++]);
- tmp= &(ctx->bn[ctx->tos++]);
-
- if (BN_copy(v,a) == NULL) goto err;
- bits=BN_num_bits(p);
-
- if (BN_is_odd(p))
- { if (BN_copy(r,a) == NULL) goto err; }
- else { if (!BN_one(r)) goto err; }
+ BIGNUM *v,*rr;
- for (i=1; i<bits; i++)
+ if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0)
{
- if (!BN_sqr(tmp,v,ctx)) goto err;
- if (!BN_mod(v,tmp,m,ctx)) goto err;
- if (BN_is_bit_set(p,i))
- {
- if (!BN_mul(tmp,r,v,ctx)) goto err;
- if (!BN_mod(r,tmp,m,ctx)) goto err;
- }
+ /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
+ BNerr(BN_F_BN_EXP,ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
+ return -1;
}
- ret=1;
-err:
- ctx->tos-=2;
- return(ret);
- }
-#endif
-
-/* this one works - simple but works */
-int BN_exp(BIGNUM *r, BIGNUM *a, BIGNUM *p, BN_CTX *ctx)
- {
- int i,bits,ret=0,tos;
- BIGNUM *v,*rr;
-
- tos=ctx->tos;
- v= &(ctx->bn[ctx->tos++]);
+ BN_CTX_start(ctx);
if ((r == a) || (r == p))
- rr= &(ctx->bn[ctx->tos++]);
+ rr = BN_CTX_get(ctx);
else
- rr=r;
+ rr = r;
+ if ((v = BN_CTX_get(ctx)) == NULL) goto err;
if (BN_copy(v,a) == NULL) goto err;
bits=BN_num_bits(p);
}
ret=1;
err:
- ctx->tos=tos;
if (r != rr) BN_copy(r,rr);
+ BN_CTX_end(ctx);
+ bn_check_top(r);
return(ret);
}
-int BN_mod_exp(BIGNUM *r, BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
+
+int BN_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
BN_CTX *ctx)
{
int ret;
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
/* if ((m->d[m->top-1]&BN_TBIT) && BN_is_odd(m)) */
if (BN_is_odd(m))
- { ret=BN_mod_exp_mont(r,a,p,m,ctx,NULL); }
+ {
+# ifdef MONT_EXP_WORD
+ if (a->top == 1 && !a->neg && (BN_get_flags(p, BN_FLG_CONSTTIME) == 0))
+ {
+ BN_ULONG A = a->d[0];
+ ret=BN_mod_exp_mont_word(r,A,p,m,ctx,NULL);
+ }
+ else
+# endif
+ ret=BN_mod_exp_mont(r,a,p,m,ctx,NULL);
+ }
else
#endif
#ifdef RECP_MUL_MOD
{ ret=BN_mod_exp_simple(r,a,p,m,ctx); }
#endif
+ bn_check_top(r);
return(ret);
}
-/* #ifdef RECP_MUL_MOD */
+
int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
const BIGNUM *m, BN_CTX *ctx)
{
int i,j,bits,ret=0,wstart,wend,window,wvalue;
- int start=1,ts=0;
+ int start=1;
BIGNUM *aa;
- BIGNUM val[TABLE_SIZE];
+ /* Table of variables obtained from 'ctx' */
+ BIGNUM *val[TABLE_SIZE];
BN_RECP_CTX recp;
- aa= &(ctx->bn[ctx->tos++]);
+ if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0)
+ {
+ /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
+ BNerr(BN_F_BN_MOD_EXP_RECP,ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
+ return -1;
+ }
+
bits=BN_num_bits(p);
if (bits == 0)
{
- BN_one(r);
- return(1);
+ ret = BN_one(r);
+ return ret;
}
- BN_RECP_CTX_init(&recp);
- if (BN_RECP_CTX_set(&recp,m,ctx) <= 0) goto err;
- BN_init(&(val[0]));
- ts=1;
+ BN_CTX_start(ctx);
+ aa = BN_CTX_get(ctx);
+ val[0] = BN_CTX_get(ctx);
+ if(!aa || !val[0]) goto err;
- if (!BN_mod(&(val[0]),a,m,ctx)) goto err; /* 1 */
- if (!BN_mod_mul_reciprocal(aa,&(val[0]),&(val[0]),&recp,ctx))
- goto err; /* 2 */
-
- if (bits <= 17) /* This is probably 3 or 0x10001, so just do singles */
- window=1;
- else if (bits >= 256)
- window=5; /* max size of window */
- else if (bits >= 128)
- window=4;
+ 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
- window=3;
+ {
+ if (BN_RECP_CTX_set(&recp,m,ctx) <= 0) goto err;
+ }
- j=1<<(window-1);
- for (i=1; i<j; i++)
+ if (!BN_nnmod(val[0],a,m,ctx)) goto err; /* 1 */
+ if (BN_is_zero(val[0]))
{
- BN_init(&val[i]);
- if (!BN_mod_mul_reciprocal(&(val[i]),&(val[i-1]),aa,&recp,ctx))
- goto err;
+ BN_zero(r);
+ ret = 1;
+ goto err;
}
- ts=i;
+ 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 will be an odd number < 2^window */
- if (!BN_mod_mul_reciprocal(r,r,&(val[wvalue>>1]),&recp,ctx))
+ if (!BN_mod_mul_reciprocal(r,r,val[wvalue>>1],&recp,ctx))
goto err;
/* move the 'window' down further */
}
ret=1;
err:
- ctx->tos--;
- for (i=0; i<ts; i++)
- BN_clear_free(&(val[i]));
+ BN_CTX_end(ctx);
BN_RECP_CTX_free(&recp);
+ bn_check_top(r);
return(ret);
}
-/* #endif */
-/* #ifdef MONT_MUL_MOD */
-int BN_mod_exp_mont(BIGNUM *rr, BIGNUM *a, const BIGNUM *p,
+
+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;
+ int start=1;
BIGNUM *d,*r;
- BIGNUM *aa;
- BIGNUM val[TABLE_SIZE];
+ 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 (!(m->d[0] & 1))
+ if (!BN_is_odd(m))
{
BNerr(BN_F_BN_MOD_EXP_MONT,BN_R_CALLED_WITH_EVEN_MODULUS);
return(0);
}
- d= &(ctx->bn[ctx->tos++]);
- r= &(ctx->bn[ctx->tos++]);
bits=BN_num_bits(p);
if (bits == 0)
{
- BN_one(r);
- return(1);
+ 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 1
if (in_mont != NULL)
mont=in_mont;
else
-#endif
{
if ((mont=BN_MONT_CTX_new()) == NULL) goto err;
if (!BN_MONT_CTX_set(mont,m,ctx)) goto err;
}
- BN_init(&val[0]);
- ts=1;
- if (BN_ucmp(a,m) >= 0)
+ if (a->neg || BN_ucmp(a,m) >= 0)
{
- BN_mod(&(val[0]),a,m,ctx);
- aa= &(val[0]);
+ if (!BN_nnmod(val[0],a,m,ctx))
+ goto err;
+ aa= val[0];
}
else
aa=a;
- if (!BN_to_montgomery(&(val[0]),aa,mont,ctx)) goto err; /* 1 */
- if (!BN_mod_mul_montgomery(d,&(val[0]),&(val[0]),mont,ctx)) goto err; /* 2 */
-
- if (bits <= 20) /* This is probably 3 or 0x10001, so just do singles */
- window=1;
- else if (bits >= 256)
- window=5; /* max size of window */
- else if (bits >= 128)
- window=4;
- else
- window=3;
+ if (BN_is_zero(aa))
+ {
+ BN_zero(rr);
+ ret = 1;
+ goto err;
+ }
+ if (!BN_to_montgomery(val[0],aa,mont,ctx)) goto err; /* 1 */
- j=1<<(window-1);
- for (i=1; i<j; i++)
+ window = BN_window_bits_for_exponent_size(bits);
+ if (window > 1)
{
- BN_init(&(val[i]));
- if (!BN_mod_mul_montgomery(&(val[i]),&(val[i-1]),d,mont,ctx))
- goto err;
+ if (!BN_mod_mul_montgomery(d,val[0],val[0],mont,ctx)) goto err; /* 2 */
+ j=1<<(window-1);
+ for (i=1; i<j; i++)
+ {
+ if(((val[i] = BN_CTX_get(ctx)) == NULL) ||
+ !BN_mod_mul_montgomery(val[i],val[i-1],
+ d,mont,ctx))
+ goto err;
+ }
}
- ts=i;
start=1; /* This is used to avoid multiplication etc
* when there is only the value '1' in the
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;
+ if (!BN_to_montgomery(r,BN_value_one(),mont,ctx)) goto err;
for (;;)
{
if (BN_is_bit_set(p,wstart) == 0)
}
/* wvalue will be an odd number < 2^window */
- if (!BN_mod_mul_montgomery(r,r,&(val[wvalue>>1]),mont,ctx))
+ if (!BN_mod_mul_montgomery(r,r,val[wvalue>>1],mont,ctx))
goto err;
/* move the 'window' down further */
start=0;
if (wstart < 0) break;
}
- BN_from_montgomery(rr,r,mont,ctx);
+ if (!BN_from_montgomery(rr,r,mont,ctx)) goto err;
ret=1;
err:
if ((in_mont == NULL) && (mont != NULL)) BN_MONT_CTX_free(mont);
- ctx->tos-=2;
- for (i=0; i<ts; i++)
- BN_clear_free(&(val[i]));
+ BN_CTX_end(ctx);
+ bn_check_top(rr);
return(ret);
}
-/* #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(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, BIGNUM *a, BIGNUM *p, BIGNUM *m,
- BN_CTX *ctx)
+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 i,j,bits,ret=0,wstart,wend,window,wvalue;
int start=1;
BIGNUM *d;
- BIGNUM val[TABLE_SIZE];
+ /* 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;
+ }
- d= &(ctx->bn[ctx->tos++]);
bits=BN_num_bits(p);
if (bits == 0)
{
- BN_one(r);
- return(1);
+ ret = BN_one(r);
+ return ret;
}
- BN_init(&(val[0]));
- ts=1;
- if (!BN_mod(&(val[0]),a,m,ctx)) goto err; /* 1 */
- if (!BN_mod_mul(d,&(val[0]),&(val[0]),m,ctx))
- goto err; /* 2 */
+ BN_CTX_start(ctx);
+ d = BN_CTX_get(ctx);
+ val[0] = BN_CTX_get(ctx);
+ if(!d || !val[0]) goto err;
- if (bits <= 17) /* This is probably 3 or 0x10001, so just do singles */
- window=1;
- else if (bits >= 256)
- window=5; /* max size of window */
- else if (bits >= 128)
- window=4;
- else
- window=3;
+ if (!BN_nnmod(val[0],a,m,ctx)) goto err; /* 1 */
+ if (BN_is_zero(val[0]))
+ {
+ BN_zero(r);
+ ret = 1;
+ goto err;
+ }
- j=1<<(window-1);
- for (i=1; i<j; i++)
+ window = BN_window_bits_for_exponent_size(bits);
+ if (window > 1)
{
- BN_init(&(val[i]));
- if (!BN_mod_mul(&(val[i]),&(val[i-1]),d,m,ctx))
- goto err;
+ 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;
+ }
}
- ts=i;
start=1; /* This is used to avoid multiplication etc
* when there is only the value '1' in the
}
/* wvalue will be an odd number < 2^window */
- if (!BN_mod_mul(r,r,&(val[wvalue>>1]),m,ctx))
+ if (!BN_mod_mul(r,r,val[wvalue>>1],m,ctx))
goto err;
/* move the 'window' down further */
}
ret=1;
err:
- ctx->tos--;
- for (i=0; i<ts; i++)
- BN_clear_free(&(val[i]));
+ BN_CTX_end(ctx);
+ bn_check_top(r);
return(ret);
}
projects / openssl.git / blobdiff