Don't try and verify signatures if key is NULL (CVE-2013-0166)

Add additional check to catch this in ASN1_item_verify too.

CHANGES

@@ -4,6 +4,10 @@
 
  Changes between 0.9.8x and 0.9.8y [xx XXX xxxx]
 
+  *) Return an error when checking OCSP signatures when key is NULL.
+     This fixes a DoS attack. (CVE-2013-0166)
+     [Steve Henson]
+
   *) Call OCSP Stapling callback after ciphersuite has been chosen, so
      the right response is stapled. Also change SSL_get_certificate()
      so it returns the certificate actually sent.

crypto/asn1/a_verify.c

@@ -138,6 +138,12 @@ int ASN1_item_verify(const ASN1_ITEM *it, X509_ALGOR *a, ASN1_BIT_STRING *signat
 	unsigned char *buf_in=NULL;
 	int ret= -1,i,inl;
 
+	if (!pkey)
+		{
+		ASN1err(ASN1_F_ASN1_ITEM_VERIFY, ERR_R_PASSED_NULL_PARAMETER);
+		return -1;
+		}
+
 	EVP_MD_CTX_init(&ctx);
 	i=OBJ_obj2nid(a->algorithm);
 	type=EVP_get_digestbyname(OBJ_nid2sn(i));

crypto/ocsp/ocsp_vfy.c

@@ -91,9 +91,12 @@ int OCSP_basic_verify(OCSP_BASICRESP *bs, STACK_OF(X509) *certs,
 		{
 		EVP_PKEY *skey;
 		skey = X509_get_pubkey(signer);
-		ret = OCSP_BASICRESP_verify(bs, skey, 0);
-		EVP_PKEY_free(skey);
-		if(ret <= 0)
+		if (skey)
+			{
+			ret = OCSP_BASICRESP_verify(bs, skey, 0);
+			EVP_PKEY_free(skey);
+			}
+		if(!skey || ret <= 0)
 			{
 			OCSPerr(OCSP_F_OCSP_BASIC_VERIFY, OCSP_R_SIGNATURE_FAILURE);
 			goto end;