Commit 12593e6f authored by Bodo Möller's avatar Bodo Möller
Browse files

Move zeroing from bn_expand_internal() to bn_expand2() so that it 

happens reliably, even if the BIGNUM is already sufficiently large.

[Note that the bn_expand()/bn_wexpand() macros call bn_expand2() only
if the BIGNUM actually has to grow, so this change does not add any
new overhead as currently bn_expand2() is never called directly.]
parent 819a040f

crypto/bn/bn_lib.c

+22 −12
Original line number Diff line number Diff line
@@ -363,17 +363,6 @@ static BN_ULONG *bn_expand_internal(const BIGNUM *b, int words) 
			}

		}



	/* Now need to zero any data between b->top and b->max */

	/* XXX Why? */



	A= &(a[b->top]);

	for (i=(words - b->top)>>3; i>0; i--,A+=8)

		{

		A[0]=0; A[1]=0; A[2]=0; A[3]=0;

		A[4]=0; A[5]=0; A[6]=0; A[7]=0;

		}

	for (i=(words - b->top)&7; i>0; i--,A++)

		A[0]=0;

#else

	memset(A,0,sizeof(BN_ULONG)*(words+1));

	memcpy(A,b->d,sizeof(b->d[0])*b->top);
@@ -397,6 +386,12 @@ BIGNUM *bn_dup_expand(const BIGNUM *b, int words) 
	{

	BIGNUM *r = NULL;



	/* This function does not work if

	 *      words <= b->dmax && top < words

	 * because BN_dup() does not preserve 'dmax'!

	 * (But bn_dup_expand() is not used anywhere yet.)

	 */

	

	if (words > b->dmax)

		{

		BN_ULONG *a = bn_expand_internal(b, words);
@@ -429,12 +424,16 @@ BIGNUM *bn_dup_expand(const BIGNUM *b, int words) 
	}



/* This is an internal function that should not be used in applications.

 * It ensures that 'b' has enough room for a 'words' word number number.

 * It ensures that 'b' has enough room for a 'words' word number

 * and initialises the unused part of b->d with leading zeros.

 * It is mostly used by the various BIGNUM routines. If there is an error,

 * NULL is returned. If not, 'b' is returned. */



BIGNUM *bn_expand2(BIGNUM *b, int words)

	{

	BN_ULONG *A;

	int i;



	if (words > b->dmax)

		{

		BN_ULONG *a = bn_expand_internal(b, words);
@@ -449,6 +448,17 @@ BIGNUM *bn_expand2(BIGNUM *b, int words) 
		else

			b = NULL;

		}

	

	/* NB: bn_wexpand() calls this only if the BIGNUM really has to grow */

	A = &(b->d[b->top]);

	for (i=(words - b->top)>>3; i>0; i--,A+=8)

		{

		A[0]=0; A[1]=0; A[2]=0; A[3]=0;

		A[4]=0; A[5]=0; A[6]=0; A[7]=0;

		}

	for (i=(words - b->top)&7; i>0; i--,A++)

		A[0]=0;

	

	return b;

	}