Make OBJ_obj2nid() work correctly with NID_undef.

Currently OBJ_obj2nid() with NID_undef returns NID_ccitt - this is due to
doing a lookup on an empty value and having NID_undef conflict with an
uninitialised NID value.

Somewhat based on OpenSSL 0fb99904809.

ok tb@

1 files changed, 3 insertions, 3 deletions

diff --git a/src/lib/libcrypto/objects/obj_dat.c b/src/lib/libcrypto/objects/obj_dat.c
index 4f7396f669..7aecda2641 100644
--- a/src/lib/libcrypto/objects/obj_dat.c
+++ b/src/lib/libcrypto/objects/obj_dat.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: obj_dat.c,v 1.45 2022/01/08 21:36:39 tb Exp $ */
+/* $OpenBSD: obj_dat.c,v 1.46 2022/02/11 16:39:16 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -458,9 +458,9 @@ OBJ_obj2nid(const ASN1_OBJECT *a)
         const unsigned int *op;
         ADDED_OBJ ad, *adp;
 
-        if (a == NULL)
+        if (a == NULL || a->length == 0)
                 return (NID_undef);
-        if (a->nid != 0)
+        if (a->nid != NID_undef)
                 return (a->nid);
 
         if (added != NULL) {