netlogon: Allow zero-GUID to act the same as NULL in GetDCNameEx2

This matches Windows behaviour and allows rpcclient to work against
Samba without knowing the GUID ahead of time. Errors related to this
don't appear to occur within selftest.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13365

Signed-off-by: Garming Sam <garming@catalyst.net.nz>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Garming Sam <garming@samba.org>
Autobuild-Date(master): Fri May  4 09:11:19 CEST 2018 on sn-devel-144

diff --git a/source4/rpc_server/netlogon/dcerpc_netlogon.c b/source4/rpc_server/netlogon/dcerpc_netlogon.c
index d497364ea0da4d59b56599ece8fb67d0c63ec8b7..638dfc2b13a869c522041ad6e7dab2b64c8ac9ff 100644 (file)
--- a/source4/rpc_server/netlogon/dcerpc_netlogon.c
+++ b/source4/rpc_server/netlogon/dcerpc_netlogon.c
@@ -2845,6 +2845,14 @@ static WERROR dcesrv_netr_DsRGetDCName_base_call(struct dcesrv_netr_DsRGetDCName
                return WERR_INVALID_FLAGS;
        }
 
+       /*
+        * If we send an all-zero GUID, we should ignore it as winbind actually
+        * checks it with a DNS query. Windows also appears to ignore it.
+        */
+       if (r->in.domain_guid != NULL && GUID_all_zero(r->in.domain_guid)) {
+               r->in.domain_guid = NULL;
+       }
+
        /* Attempt winbind search only if we suspect the domain is incorrect */
        if (r->in.domain_name != NULL && strcmp("", r->in.domain_name) != 0) {
                if (r->in.flags & DS_IS_FLAT_NAME) {