domainlevel-get: fix various issues when running as non-admin

Use proper filter that is caught up by the ACI for 'permission:System:
Read Domain Level' to allow any authenticated user to see the domain
level.

If the server doesn't have domain level set, callers in replica
installer expect errors.NotFound but never get it.

Return the right exception here and change the other caller to follow
the same convention.

Inability to retrieve ipaDomainLevel attribute due to a filter mismatch
casues ipa-replica-install to fail if run as a replica host principal.

Use DOMAIN_LEVEL_0 constant instead of 0 as used by the rest of the code.

Fixes: https://pagure.io/freeipa/issue/7876
Reviewed-By: Christian Heimes <cheimes@redhat.com>

ipaserver/plugins/domainlevel.py

@@ -10,6 +10,7 @@ from ipalib import errors
 from ipalib import output
 from ipalib.parameters import Int
 from ipalib.plugable import Registry
+from ipalib.constants import DOMAIN_LEVEL_0, MIN_DOMAIN_LEVEL
 
 from ipapython.dn import DN
 
@@ -45,7 +46,7 @@ def get_domainlevel_range(master_entry):
             int(master_entry['ipaMaxDomainLevel'][0])
         )
     except KeyError:
-        return DomainLevelRange(0, 0)
+        return DomainLevelRange(DOMAIN_LEVEL_0, DOMAIN_LEVEL_0)
 
 
 def check_conflict_entries(ldap, api, desired_value):
@@ -102,12 +103,20 @@ class domainlevel_get(Command):
 
     def execute(self, *args, **options):
         ldap = self.api.Backend.ldap2
-        entry = ldap.get_entry(
+        entry = ldap.get_entries(
             get_domainlevel_dn(self.api),
-            ['ipaDomainLevel']
-        )
+            scope=ldap.SCOPE_BASE,
+            filter='(objectclass=ipadomainlevelconfig)',
+            attrs_list=['ipaDomainLevel']
+        )[0]
 
-        return {'result': int(entry.single_value['ipaDomainLevel'])}
+        try:
+            value = int(entry.single_value['ipaDomainLevel'])
+            return {'result': value}
+        except KeyError:
+            raise errors.NotFound(
+                reason=_(
+                    'Server does not support domain level functionality'))
 
 
 @register()
@@ -120,7 +129,7 @@ class domainlevel_set(Command):
         Int('ipadomainlevel',
             cli_name='level',
             label=_('Domain Level'),
-            minvalue=0,
+            minvalue=MIN_DOMAIN_LEVEL,
         ),
     )
 

ipaserver/plugins/topology.py

@@ -12,7 +12,7 @@ from .baseldap import (
     LDAPRetrieve)
 from ipalib import _, ngettext
 from ipalib import output
-from ipalib.constants import DOMAIN_LEVEL_1
+from ipalib.constants import MIN_DOMAIN_LEVEL, DOMAIN_LEVEL_1
 from ipaserver.topology import (
     create_topology_graph, get_topology_connection_errors,
     map_masters_to_suffixes)
@@ -82,7 +82,11 @@ register = Registry()
 
 
 def validate_domain_level(api):
-    current = int(api.Command.domainlevel_get()['result'])
+    try:
+        current = int(api.Command.domainlevel_get()['result'])
+    except errors.NotFound:
+        current = MIN_DOMAIN_LEVEL
+
     if current < DOMAIN_LEVEL_1:
         raise errors.InvalidDomainLevelError(
             reason=_('Topology management requires minimum domain level {0} '