Provide API for management of host, service, and user principal aliases

New commands (*-{add,remove}-principal [PKEY] [PRINCIPAL ...])
were added to manage principal aliases.

'add' commands will check the following:
* the correct principal type is supplied as an alias
* the principals have correct realm and the realm/alternative suffix (e.g.
  e-mail) do not overlap with those of trusted AD domains

If the entry does not have canonical principal name, the first returned
principal name will be set as one. This is mostly to smoothly operate on
entries created on older servers.

'remove' commands will check that there is at least one principal alias equal
to the canonical name left on the entry.

See also: http://www.freeipa.org/page/V4/Kerberos_principal_aliases

https://fedorahosted.org/freeipa/ticket/1365
https://fedorahosted.org/freeipa/ticket/3961
https://fedorahosted.org/freeipa/ticket/5413

Reviewed-By: David Kupka <dkupka@redhat.com>
Reviewed-By: Jan Cholasta <jcholast@redhat.com>

ipaserver/plugins/baseuser.py

@@ -27,7 +27,8 @@ from ipalib.parameters import Principal
 from ipalib.plugable import Registry
 from .baseldap import (
     DN, LDAPObject, LDAPCreate, LDAPUpdate, LDAPSearch, LDAPDelete,
-    LDAPRetrieve, LDAPAddMember, LDAPRemoveMember)
+    LDAPRetrieve, LDAPAddAttribute, LDAPRemoveAttribute, LDAPAddMember,
+    LDAPRemoveMember)
 from ipaserver.plugins.service import (
    validate_certificate, validate_realm, normalize_principal)
 from ipalib.request import context
@@ -42,7 +43,10 @@ from ipalib.util import (
     remove_sshpubkey_from_output_post,
     remove_sshpubkey_from_output_list_post,
     add_sshpubkey_to_attrs_pre,
-    set_krbcanonicalname
+    set_krbcanonicalname,
+    check_principal_realm_in_trust_namespace,
+    ensure_last_krbprincipalname,
+    ensure_krbcanonicalname_set
 )
 
 if six.PY3:
@@ -212,14 +216,20 @@ class baseuser(LDAPObject):
             label=_('Login shell'),
         ),
         Principal(
-            'krbprincipalname?',
+            'krbcanonicalname?',
+            validate_realm,
+            label=_('Principal name'),
+            flags={'no_option', 'no_create', 'no_update', 'no_search'},
+            normalizer=normalize_user_principal
+        ),
+        Principal(
+            'krbprincipalname*',
             validate_realm,
             cli_name='principal',
-            label=_('Kerberos principal'),
-            default_from=lambda uid: kerberos.Principal.from_text(
+            label=_('Principal alias'),
+            default_from=lambda uid: kerberos.Principal(
                 uid.lower(), realm=api.env.realm),
             autofill=True,
-            flags=['no_update'],
             normalizer=normalize_user_principal,
         ),
         DateTime('krbprincipalexpiration?',
@@ -621,3 +631,20 @@ class baseuser_add_manager(LDAPAddMember):
 
 class baseuser_remove_manager(LDAPRemoveMember):
     member_attributes = ['manager']
+
+
+class baseuser_add_principal(LDAPAddAttribute):
+    attribute = 'krbprincipalname'
+
+    def pre_callback(self, ldap, dn, entry_attrs, attrs_list, *keys, **options):
+        check_principal_realm_in_trust_namespace(self.api, *keys)
+        ensure_krbcanonicalname_set(ldap, entry_attrs)
+        return dn
+
+
+class baseuser_remove_principal(LDAPRemoveAttribute):
+    attribute = 'krbprincipalname'
+
+    def pre_callback(self, ldap, dn, entry_attrs, attrs_list, *keys, **options):
+        ensure_last_krbprincipalname(ldap, entry_attrs, *keys)
+        return dn