Do not zero cofactor on ec_guess_cofactor() success

The cofactor we tried to calculate should only be zeroed if we failed
to compute it.

ok inoguchi jsing

1 files changed, 6 insertions, 2 deletions

diff --git a/src/lib/libcrypto/ec/ec_lib.c b/src/lib/libcrypto/ec/ec_lib.c
index 45df1329ff..455d44a942 100644
--- a/src/lib/libcrypto/ec/ec_lib.c
+++ b/src/lib/libcrypto/ec/ec_lib.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ec_lib.c,v 1.42 2022/03/29 13:44:06 tb Exp $ */
+/* $OpenBSD: ec_lib.c,v 1.43 2022/03/29 13:48:40 tb Exp $ */
 /*
  * Originally written by Bodo Moeller for the OpenSSL project.
  */
@@ -321,10 +321,14 @@ ec_guess_cofactor(EC_GROUP *group)
                 goto err;
 
         ret = 1;
+
  err:
         BN_CTX_end(ctx);
         BN_CTX_free(ctx);
-        BN_zero(&group->cofactor);
+
+        if (ret != 1)
+                BN_zero(&group->cofactor);
+
         return ret;
 }