Preserve user principal aliases during rename operation

When a MODRDN is performed on the user entry, the MODRDN plugin resets both
krbPrincipalName and krbCanonicalName to the value constructed from uid. In
doing so, hovewer, any principal aliases added to the krbPrincipalName are
wiped clean. In this patch old aliases are fetched before the MODRDN operation
takes place and inserted back after it is performed.

This also preserves previous user logins which can be used further for
authentication as aliases.

https://fedorahosted.org/freeipa/ticket/6028

Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
Reviewed-By: Simo Sorce <ssorce@redhat.com>

ipaserver/plugins/baseuser.py

@@ -498,6 +498,50 @@ class baseuser_mod(LDAPUpdate):
                             len = int(config.get('ipamaxusernamelength')[0])
                         )
                     )
+
+    def preserve_krbprincipalname_pre(self, ldap, entry_attrs, *keys, **options):
+        """
+        preserve user principal aliases during rename operation. This is the
+        pre-callback part of this. Another method called during post-callback
+        shall insert the principals back
+        """
+        if options.get('rename', None) is None:
+            return
+
+        try:
+            old_entry = ldap.get_entry(
+                entry_attrs.dn, attrs_list=(
+                    'krbprincipalname', 'krbcanonicalname'))
+
+            if 'krbcanonicalname' not in old_entry:
+                return
+        except errors.NotFound:
+            self.obj.handle_not_found(*keys)
+
+        self.context.krbprincipalname = old_entry.get(
+            'krbprincipalname', [])
+
+    def preserve_krbprincipalname_post(self, ldap, entry_attrs, **options):
+        """
+        Insert the preserved aliases back to the user entry during rename
+        operation
+        """
+        if options.get('rename', None) is None or not hasattr(
+                self.context, 'krbprincipalname'):
+            return
+
+        obj_pkey = self.obj.get_primary_key_from_dn(entry_attrs.dn)
+        canonical_name = entry_attrs['krbcanonicalname'][0]
+
+        principals_to_add = tuple(p for p in self.context.krbprincipalname if
+                                  p != canonical_name)
+
+        if principals_to_add:
+            result = self.api.Command.user_add_principal(
+                obj_pkey, principals_to_add)['result']
+
+            entry_attrs['krbprincipalname'] = result.get('krbprincipalname', [])
+
     def check_mail(self, entry_attrs):
         if 'mail' in entry_attrs:
             entry_attrs['mail'] = self.obj.normalize_and_validate_email(entry_attrs['mail'])
@@ -557,9 +601,11 @@ class baseuser_mod(LDAPUpdate):
 
         self.check_objectclass(ldap, dn, entry_attrs)
         self.obj.convert_usercertificate_pre(entry_attrs)
+        self.preserve_krbprincipalname_pre(ldap, entry_attrs, *keys, **options)
 
     def post_common_callback(self, ldap, dn, entry_attrs, *keys, **options):
         assert isinstance(dn, DN)
+        self.preserve_krbprincipalname_post(ldap, entry_attrs, **options)
         if options.get('random', False):
             try:
                 entry_attrs['randompassword'] = unicode(getattr(context, 'randompassword'))