prevent last admin from being disabled

We prevent the last member of the admin group from being deleted. The
same check needs to be performed when disabling a user.

* Moved the code in del_user to the common subroutine
  check_protected_member() and call it from both user_del and
  user_disable. Note, unlike user_del user_disable does not have a
  'pre' callback therefore the check function is called in
  user_disable's execute routine.

* Make check_protected_member() aware of disabled members. It's not
  sufficient to check which members of the protected group are
  present, one must only consider those members which are enabled.

* Add tests to test_user_plugin.py.

  - verify you cannot delete nor disable the last member of the admin
    group

  - verify when the admin group contains disabled users in addition to
    enabled users only the enabled users are considered when
    determining if the last admin is about to be disabled or deleted.

* Replace duplicated hardcoded values in the tests with variables or
  subroutines, this makes the individual tests a bit more succinct and
  easier to copy/modify.

* Update error msg to reflect either deleting or disabling is an error.

https://fedorahosted.org/freeipa/ticket/2979

ipalib/errors.py

@@ -1627,18 +1627,18 @@ class DependentEntry(ExecutionError):
 
 class LastMemberError(ExecutionError):
     """
-    **4308** Raised when an entry being deleted is last member of a protected group
+    **4308** Raised when an entry being deleted or disabled is last member of a protected group
 
     For example:
     >>> raise LastMemberError(key=u'admin', label=u'group', container=u'admins')
     Traceback (most recent call last):
       ...
-    LastMemberError: admin cannot be deleted because it is the last member of group admins
+    LastMemberError: admin cannot be deleted or disabled because it is the last member of group admins
 
     """
 
     errno = 4308
-    format = _('%(key)s cannot be deleted because it is the last member of %(label)s %(container)s')
+    format = _('%(key)s cannot be deleted or disabled because it is the last member of %(label)s %(container)s')
 
 
 class ProtectedEntryError(ExecutionError):

ipalib/plugins/user.py

@@ -166,6 +166,24 @@ def normalize_principal(principal):
     return unicode('%s@%s' % (user, realm))
 
 
+def check_protected_member(user, protected_group_name=u'admins'):
+    '''
+    Ensure the last enabled member of a protected group cannot be deleted or
+    disabled by raising LastMemberError.
+    '''
+
+    # Get all users in the protected group
+    result = api.Command.user_find(in_group=protected_group_name)
+
+    # Build list of users in the protected group who are enabled
+    result = result['result']
+    enabled_users = [entry['uid'][0] for entry in result if not entry['nsaccountlock']]
+
+    # If the user is the last enabled user raise LastMemberError exception
+    if enabled_users == [user]:
+        raise errors.LastMemberError(key=user, label=_(u'group'),
+            container=protected_group_name)
+
 class user(LDAPObject):
     """
     User object.
@@ -550,11 +568,7 @@ class user_del(LDAPDelete):
 
     def pre_callback(self, ldap, dn, *keys, **options):
         assert isinstance(dn, DN)
-        protected_group_name = u'admins'
-        result = api.Command.group_show(protected_group_name)
-        if result['result'].get('member_user', []) == [keys[-1]]:
-            raise errors.LastMemberError(key=keys[-1], label=_(u'group'),
-                container=protected_group_name)
+        check_protected_member(keys[-1])
         return dn
 
 api.register(user_del)
@@ -686,8 +700,9 @@ class user_disable(LDAPQuery):
     def execute(self, *keys, **options):
         ldap = self.obj.backend
 
-        dn = self.obj.get_dn(*keys, **options)
+        check_protected_member(keys[-1])
 
+        dn = self.obj.get_dn(*keys, **options)
         ldap.deactivate_entry(dn)
 
         return dict(