Adjust various bignum functions to use BN_CTX for variables instead of

locally initialising their own.

NB: I've removed the "BN_clear_free()" loops for the exit-paths in some of
these functions, and that may be a major part of the performance
improvements we're seeing. The "free" part can be removed because we're
using BN_CTX. The "clear" part OTOH can be removed because BN_CTX
destruction automatically performs this task, so performing it inside
functions that may be called repeatedly is wasteful. This is currently safe
within openssl due to the fact that BN_CTX objects are never created for
longer than a single high-level operation. However, that is only because
there's currently no mechanism in openssl for thread-local storage. Beyond
that, this might be an issue for applications using the bignum API directly
and caching their own BN_CTX objects. The solution is to introduce a flag
to BN_CTX_start() that allows its variables to be automatically sanitised
on release during BN_CTX_end(). This way any higher-level function (and
perhaps the application) can specify this flag in its own
BN_CTX_start()/BN_CTX_end() pair, and this will cause inner-loop functions
specifying the flag to be ignored so that sanitisation is handled only once
back out at the higher level. I will be implementing this in the near
future.

1 files changed, 22 insertions, 28 deletions

diff --git a/crypto/bn/bn_exp2.c b/crypto/bn/bn_exp2.c
index 1223c678ce..b3f43cec8c 100644
--- a/crypto/bn/bn_exp2.c
+++ b/crypto/bn/bn_exp2.c
@@ -120,11 +120,11 @@ int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,
 	BN_CTX *ctx, BN_MONT_CTX *in_mont)
 	{
 	int i,j,bits,b,bits1,bits2,ret=0,wpos1,wpos2,window1,window2,wvalue1,wvalue2;
-	int r_is_one=1,ts1=0,ts2=0;
+	int r_is_one=1;
 	BIGNUM *d,*r;
 	const BIGNUM *a_mod_m;
-	/* TODO: BN_CTX??? */
-	BIGNUM val1[TABLE_SIZE], val2[TABLE_SIZE];
+	/* Tables of variables obtained from 'ctx' */
+	BIGNUM *val1[TABLE_SIZE], *val2[TABLE_SIZE];
 	BN_MONT_CTX *mont=NULL;
 
 	bn_check_top(a1);
@@ -151,7 +151,9 @@ int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,
 	BN_CTX_start(ctx);
 	d = BN_CTX_get(ctx);
 	r = BN_CTX_get(ctx);
-	if (d == NULL || r == NULL) goto err;
+	val1[0] = BN_CTX_get(ctx);
+	val2[0] = BN_CTX_get(ctx);
+	if(!d || !r || !val1[0] || !val2[0]) goto err;
 
 	if (in_mont != NULL)
 		mont=in_mont;
@@ -167,13 +169,11 @@ int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,
 	/*
 	 * Build table for a1:   val1[i] := a1^(2*i + 1) mod m  for i = 0 .. 2^(window1-1)
 	 */
-	BN_init(&val1[0]);
-	ts1=1;
 	if (a1->neg || BN_ucmp(a1,m) >= 0)
 		{
-		if (!BN_mod(&(val1[0]),a1,m,ctx))
+		if (!BN_mod(val1[0],a1,m,ctx))
 			goto err;
-		a_mod_m = &(val1[0]);
+		a_mod_m = val1[0];
 		}
 	else
 		a_mod_m = a1;
@@ -184,32 +184,30 @@ int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,
 		goto err;
 		}
 
-	if (!BN_to_montgomery(&(val1[0]),a_mod_m,mont,ctx)) goto err;
+	if (!BN_to_montgomery(val1[0],a_mod_m,mont,ctx)) goto err;
 	if (window1 > 1)
 		{
-		if (!BN_mod_mul_montgomery(d,&(val1[0]),&(val1[0]),mont,ctx)) goto err;
+		if (!BN_mod_mul_montgomery(d,val1[0],val1[0],mont,ctx)) goto err;
 
 		j=1<<(window1-1);
 		for (i=1; i<j; i++)
 			{
-			BN_init(&(val1[i]));
-			if (!BN_mod_mul_montgomery(&(val1[i]),&(val1[i-1]),d,mont,ctx))
+			if(((val1[i] = BN_CTX_get(ctx)) == NULL) ||
+					!BN_mod_mul_montgomery(val1[i],val1[i-1],
+						d,mont,ctx))
 				goto err;
 			}
-		ts1=i;
 		}
 
 
 	/*
 	 * Build table for a2:   val2[i] := a2^(2*i + 1) mod m  for i = 0 .. 2^(window2-1)
 	 */
-	BN_init(&val2[0]);
-	ts2=1;
 	if (a2->neg || BN_ucmp(a2,m) >= 0)
 		{
-		if (!BN_mod(&(val2[0]),a2,m,ctx))
+		if (!BN_mod(val2[0],a2,m,ctx))
 			goto err;
-		a_mod_m = &(val2[0]);
+		a_mod_m = val2[0];
 		}
 	else
 		a_mod_m = a2;
@@ -219,19 +217,19 @@ int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,
 		ret = 1;
 		goto err;
 		}
-	if (!BN_to_montgomery(&(val2[0]),a_mod_m,mont,ctx)) goto err;
+	if (!BN_to_montgomery(val2[0],a_mod_m,mont,ctx)) goto err;
 	if (window2 > 1)
 		{
-		if (!BN_mod_mul_montgomery(d,&(val2[0]),&(val2[0]),mont,ctx)) goto err;
+		if (!BN_mod_mul_montgomery(d,val2[0],val2[0],mont,ctx)) goto err;
 
 		j=1<<(window2-1);
 		for (i=1; i<j; i++)
 			{
-			BN_init(&(val2[i]));
-			if (!BN_mod_mul_montgomery(&(val2[i]),&(val2[i-1]),d,mont,ctx))
+			if(((val2[i] = BN_CTX_get(ctx)) == NULL) ||
+					!BN_mod_mul_montgomery(val2[i],val2[i-1],
+						d,mont,ctx))
 				goto err;
 			}
-		ts2=i;
 		}
 
 
@@ -288,7 +286,7 @@ int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,
 		if (wvalue1 && b == wpos1)
 			{
 			/* wvalue1 is odd and < 2^window1 */
-			if (!BN_mod_mul_montgomery(r,r,&(val1[wvalue1>>1]),mont,ctx))
+			if (!BN_mod_mul_montgomery(r,r,val1[wvalue1>>1],mont,ctx))
 				goto err;
 			wvalue1 = 0;
 			r_is_one = 0;
@@ -297,7 +295,7 @@ int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,
 		if (wvalue2 && b == wpos2)
 			{
 			/* wvalue2 is odd and < 2^window2 */
-			if (!BN_mod_mul_montgomery(r,r,&(val2[wvalue2>>1]),mont,ctx))
+			if (!BN_mod_mul_montgomery(r,r,val2[wvalue2>>1],mont,ctx))
 				goto err;
 			wvalue2 = 0;
 			r_is_one = 0;
@@ -308,10 +306,6 @@ int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,
 err:
 	if ((in_mont == NULL) && (mont != NULL)) BN_MONT_CTX_free(mont);
 	BN_CTX_end(ctx);
-	for (i=0; i<ts1; i++)
-		BN_clear_free(&(val1[i]));
-	for (i=0; i<ts2; i++)
-		BN_clear_free(&(val2[i]));
 	bn_check_top(rr);
 	return(ret);
 	}