bn_exp.c: fix corner case in new constant-time code.
authorAndy Polyakov <appro@openssl.org>
Sat, 29 Oct 2011 19:25:13 +0000 (19:25 +0000)
committerAndy Polyakov <appro@openssl.org>
Sat, 29 Oct 2011 19:25:13 +0000 (19:25 +0000)
Submitted by: Emilia Kasper

crypto/bn/bn_exp.c

index 5c49236..8454d42 100644 (file)
@@ -693,6 +693,11 @@ int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
 
        BN_ULONG *np=mont->N.d, *n0=mont->n0;
 
+       /* BN_to_montgomery can contaminate words above .top
+        * [in BN_DEBUG[_DEBUG] build]... */
+       for (i=am.top; i<top; i++)      am.d[i]=0;
+       for (i=tmp.top; i<top; i++)     tmp.d[i]=0;
+
        bn_scatter5(tmp.d,top,powerbuf,0);
        bn_scatter5(am.d,am.top,powerbuf,1);
        bn_mul_mont(tmp.d,am.d,am.d,np,n0,top);