Avoid undefined behavior with memcmp(NULL, x, 0) in ASN1_STRING_cmp()

ok jsing miod

diff --git a/lib/libcrypto/asn1/a_string.c b/lib/libcrypto/asn1/a_string.c
index bfd2abf..ca03008 100644 (file)
--- a/lib/libcrypto/asn1/a_string.c
+++ b/lib/libcrypto/asn1/a_string.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: a_string.c,v 1.14 2023/07/05 21:23:36 beck Exp $ */
+/* $OpenBSD: a_string.c,v 1.15 2023/08/15 17:38:00 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -119,10 +119,12 @@ ASN1_STRING_cmp(const ASN1_STRING *a, const ASN1_STRING *b)
                return -1;
        if ((cmp = (a->length - b->length)) != 0)
                return cmp;
-       if ((cmp = memcmp(a->data, b->data, a->length)) != 0)
-               return cmp;
+       if (a->length != 0) {
+               if ((cmp = memcmp(a->data, b->data, a->length)) != 0)
+                       return 0;
+       }
 
-       return (a->type - b->type);
+       return a->type - b->type;
 }
 LCRYPTO_ALIAS(ASN1_STRING_cmp);