Commit 953937bd authored by Dr. Stephen Henson's avatar Dr. Stephen Henson
Browse files

Fix a horrible BN bug in bn_expand2 which caused BN_add_word() et al to fail 

when they cause the destination to expand.

To see how evil this is try this:

#include <pem.h>
main()
{
	BIGNUM *bn = NULL;
        int i;
	bn = BN_new();
	BN_hex2bn(&bn, "FFFFFFFF");
	BN_add_word(bn, 1);
	printf("Value %s\n", BN_bn2hex(bn));
}

This would typically fail before the patch.

It also screws up if you comment out the BN_hex2bn line above or in any
situation where BN_add_word() causes the number of BN_ULONGs in the result
to change (try doubling the number of FFs).
parent abed0b8a

CHANGES

+4 −0
Original line number Original line Diff line number Diff line
@@ -5,6 +5,10 @@ 




 Changes between 0.9.2b and 0.9.3

 Changes between 0.9.2b and 0.9.3





  *) Fix an evil bug in bn_expand2() which caused various BN functions to

     fail when they extended the size of a BIGNUM.

     [Steve Henson]



  *) Various utility functions to handle SXNet extension. Modify mkdef.pl to

  *) Various utility functions to handle SXNet extension. Modify mkdef.pl to

     support typesafe stack.

     support typesafe stack.

     [Steve Henson]

     [Steve Henson]

crypto/bn/bn_lib.c

+26 −17
Original line number Original line Diff line number Diff line
@@ -376,8 +376,12 @@ int words; 
memset(A,0x5c,sizeof(BN_ULONG)*(words+1));

memset(A,0x5c,sizeof(BN_ULONG)*(words+1));

#if 1

#if 1

		B=b->d;

		B=b->d;

		/* Check if the previous number needs to be copied */

		if (B != NULL)

		if (B != NULL)

			{

			{

			/* This lot is an unrolled loop to copy b->top 

			 * BN_ULONGs from B to A

			 */

			for (i=b->top&(~7); i>0; i-=8)

			for (i=b->top&(~7); i>0; i-=8)

				{

				{

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

				A[0]=B[0]; A[1]=B[1]; A[2]=B[2]; A[3]=B[3];
@@ -414,15 +418,24 @@ memset(A,0x5c,sizeof(BN_ULONG)*(words+1)); 
				 */

				 */

				;

				;

				}

				}

			Free(b->d);

			}



		b->d=a;

		b->max=words;



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



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

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

			j=b->max-8;

		j=(b->max - b->top) & ~7;

			for (i=b->top; i<j; i+=8)

		for (i=0; i<j; i+=8)

			{

			{

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

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

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

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

			B+=8;

			B+=8;

			}

			}

			for (j+=8; i<j; i++)

		j=(b->max - b->top) & 7;

		for (i=0; i<j; i++)

			{

			{

			B[0]=0;

			B[0]=0;

			B++;

			B++;
@@ -433,11 +446,7 @@ memset(A,0x5c,sizeof(BN_ULONG)*(words+1)); 
		

		

/*		memset(&(p[b->max]),0,((words+1)-b->max)*sizeof(BN_ULONG)); */

/*		memset(&(p[b->max]),0,((words+1)-b->max)*sizeof(BN_ULONG)); */

/*	{ int i; for (i=b->max; i<words+1; i++) p[i]=i;} */

/*	{ int i; for (i=b->max; i<words+1; i++) p[i]=i;} */

			Free(b->d);

			}





		b->d=a;

		b->max=words;

		}

		}

	return(b);

	return(b);

	}

	}