join: Use a specific attribute order for the DsAddEntry nTDSDSA object

Joining a Windows domain can throw an error if the HasMasterNCs
attribute occurs before msDS-HasMasterNCs. This patch changes the
attribute order so that msDS-HasMasterNCs is always first.

Previously on python2, the dictionary hash order was arbitrary but
constant. By luck, msDS-HasMasterNCs was always before HasMasterNCs, so
we never noticed any problem. With python3, the dictionary hash order
now changes everytime you run the command, so the order is
unpredictable.

To enforce a order, we can change to use an OrderedDict, which will
return the keys in the order they're added.

I've asked Microsoft to clarify the protocol requirement here WRT
attribute order. However, in the meantime we may as well fix the problem
for users.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14046
RN: When trying to join a Windows domain (with functional level 2008R2)
as an AD domain controller, the 'samba-tool domain join' command could
throw a python exception: 'RuntimeError ("DsAddEntry failed")'. When
this problem occurred, you would also see the message "DsAddEntry failed
with status WERR_ACCESS_DENIED info (8363, 'WERR_DS_NO_CROSSREF_FOR_NC')"
in the command output. This issue has now been resolved. Note that this
problem would only occur on Samba v4.10 when using the Python3 packages.

Signed-off-by: Tim Beale <[email protected]>
Reviewed-by: Andrew Bartlett <[email protected]>

Autobuild-User(master): Andrew Bartlett <[email protected]>
Autobuild-Date(master): Wed Jul 24 04:18:21 UTC 2019 on sn-devel-184

python/samba/join.py

@@ -48,6 +48,7 @@
 import re
 import os
 import tempfile
+from collections import OrderedDict
 from samba.compat import text_type
 from samba.compat import get_string
 from samba.netcmd import CommandError
@@ -555,11 +556,14 @@ def join_ntdsdsa_obj(ctx):
         '''return the ntdsdsa object to add'''
 
         print("Adding %s" % ctx.ntds_dn)
-        rec = {
-            "dn": ctx.ntds_dn,
-            "objectclass": "nTDSDSA",
-            "systemFlags": str(samba.dsdb.SYSTEM_FLAG_DISALLOW_MOVE_ON_DELETE),
-            "dMDLocation": ctx.schema_dn}
+
+        # When joining Windows, the order of certain attributes (mostly only
+        # msDS-HasMasterNCs and HasMasterNCs) seems to matter
+        rec = OrderedDict([
+            ("dn", ctx.ntds_dn),
+            ("objectclass", "nTDSDSA"),
+            ("systemFlags", str(samba.dsdb.SYSTEM_FLAG_DISALLOW_MOVE_ON_DELETE)),
+            ("dMDLocation", ctx.schema_dn)])
 
         nc_list = [ctx.base_dn, ctx.config_dn, ctx.schema_dn]
 
@@ -575,12 +579,17 @@ def join_ntdsdsa_obj(ctx):
             rec["options"] = "37"
         else:
             rec["objectCategory"] = "CN=NTDS-DSA,%s" % ctx.schema_dn
+
+            # Note that Windows seems to have an undocumented requirement that
+            # the msDS-HasMasterNCs attribute occurs before HasMasterNCs
+            if ctx.behavior_version >= samba.dsdb.DS_DOMAIN_FUNCTION_2003:
+                rec["msDS-HasMasterNCs"] = ctx.full_nc_list
+
             rec["HasMasterNCs"]      = []
             for nc in nc_list:
                 if nc in ctx.full_nc_list:
                     rec["HasMasterNCs"].append(nc)
-            if ctx.behavior_version >= samba.dsdb.DS_DOMAIN_FUNCTION_2003:
-                rec["msDS-HasMasterNCs"] = ctx.full_nc_list
+
             rec["options"] = "1"
             rec["invocationId"] = ndr_pack(ctx.invocation_id)