* [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
#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 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);
if (BN_is_odd(m))
{
# ifdef MONT_EXP_WORD
- if (a->top == 1 && !a->neg)
+ 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);
const BIGNUM *m, BN_CTX *ctx)
{
int i,j,bits,ret=0,wstart,wend,window,wvalue;
- int start=1,ts=0;
+ int start=1;
BIGNUM *aa;
- BIGNUM val[TABLE_SIZE];
+ /* Table of variables obtained from 'ctx' */
+ BIGNUM *val[TABLE_SIZE];
BN_RECP_CTX recp;
+ if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0)
+ {
+ /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
+ BNerr(BN_F_BN_MOD_EXP_RECP,ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
+ return -1;
+ }
+
bits=BN_num_bits(p);
if (bits == 0)
}
BN_CTX_start(ctx);
- if ((aa = BN_CTX_get(ctx)) == NULL) goto err;
+ aa = BN_CTX_get(ctx);
+ val[0] = BN_CTX_get(ctx);
+ if(!aa || !val[0]) goto err;
BN_RECP_CTX_init(&recp);
if (m->neg)
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])))
+ if (!BN_nnmod(val[0],a,m,ctx)) goto err; /* 1 */
+ if (BN_is_zero(val[0]))
{
- ret = BN_zero(r);
+ 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))
+ 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++)
{
- BN_init(&val[i]);
- if (!BN_mod_mul_reciprocal(&(val[i]),&(val[i-1]),aa,&recp,ctx))
+ if(((val[i] = BN_CTX_get(ctx)) == NULL) ||
+ !BN_mod_mul_reciprocal(val[i],val[i-1],
+ aa,&recp,ctx))
goto err;
}
- ts=i;
}
start=1; /* This is used to avoid multiplication etc
}
/* 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:
BN_CTX_end(ctx);
- for (i=0; i<ts; i++)
- BN_clear_free(&(val[i]));
BN_RECP_CTX_free(&recp);
bn_check_top(r);
return(ret);
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;
const BIGNUM *aa;
- /* TODO: BN_CTX??? */
- BIGNUM val[TABLE_SIZE];
+ /* 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);
BN_CTX_start(ctx);
d = BN_CTX_get(ctx);
r = BN_CTX_get(ctx);
- if (d == NULL || r == NULL) goto err;
+ val[0] = BN_CTX_get(ctx);
+ if (!d || !r || !val[0]) goto err;
/* If this is not done, things will break in the montgomery
* part */
if (!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))
+ if (!BN_nnmod(val[0],a,m,ctx))
goto err;
- aa= &(val[0]);
+ aa= val[0];
}
else
aa=a;
if (BN_is_zero(aa))
{
- ret = BN_zero(rr);
+ BN_zero(rr);
+ ret = 1;
goto err;
}
- if (!BN_to_montgomery(&(val[0]),aa,mont,ctx)) goto err; /* 1 */
+ 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 */
+ 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++)
{
- BN_init(&(val[i]));
- if (!BN_mod_mul_montgomery(&(val[i]),&(val[i-1]),d,mont,ctx))
+ 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
}
/* 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 */
err:
if ((in_mont == NULL) && (mont != NULL)) BN_MONT_CTX_free(mont);
BN_CTX_end(ctx);
- for (i=0; i<ts; i++)
- BN_clear_free(&(val[i]));
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)
{
#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 (a == 0)
{
- ret = BN_zero(rr);
+ BN_zero(rr);
+ ret = 1;
return ret;
}
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;
- /* TODO: BN_CTX?? */
- 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;
+ }
bits=BN_num_bits(p);
}
BN_CTX_start(ctx);
- if ((d = BN_CTX_get(ctx)) == NULL) goto err;
+ d = BN_CTX_get(ctx);
+ val[0] = BN_CTX_get(ctx);
+ if(!d || !val[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])))
+ if (!BN_nnmod(val[0],a,m,ctx)) goto err; /* 1 */
+ if (BN_is_zero(val[0]))
{
- ret = BN_zero(r);
+ 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))
+ if (!BN_mod_mul(d,val[0],val[0],m,ctx))
goto err; /* 2 */
j=1<<(window-1);
for (i=1; i<j; i++)
{
- BN_init(&(val[i]));
- if (!BN_mod_mul(&(val[i]),&(val[i-1]),d,m,ctx))
+ 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
}
/* 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:
BN_CTX_end(ctx);
- for (i=0; i<ts; i++)
- BN_clear_free(&(val[i]));
bn_check_top(r);
return(ret);
}
projects / openssl.git / blobdiff