trusts: Add support for an external trust to Active Directory domain

External trust is a trust that can be created between Active Directory
domains that are in different forests or between an Active Directory
domain. Since FreeIPA does not support non-Kerberos means of
communication, external trust to Windows NT 4.0 or earlier domains is
not supported.

The external trust is not transitive and can be established to any
domain in another forest. This means no access beyond the external
domain is possible via the trust link.

Resolves: https://fedorahosted.org/freeipa/ticket/5743
Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>

API.txt

@@ -5208,12 +5208,13 @@ arg: Str('cn', cli_name='name')
 option: Str('version?')
 output: Output('result')
 command: trust_add
-args: 1,14,3
+args: 1,15,3
 arg: Str('cn', cli_name='realm')
 option: Str('addattr*', cli_name='addattr')
 option: Flag('all', autofill=True, cli_name='all', default=False)
 option: Int('base_id?', cli_name='base_id')
 option: Bool('bidirectional?', cli_name='two_way', default=False)
+option: Bool('external?', cli_name='external', default=False)
 option: Int('range_size?', cli_name='range_size')
 option: StrEnum('range_type?', cli_name='range_type', values=[u'ipa-ad-trust-posix', u'ipa-ad-trust'])
 option: Flag('raw', autofill=True, cli_name='raw', default=False)

ipaserver/dcerpc.py

@@ -77,6 +77,11 @@ and Samba4 python bindings.
 TRUST_ONEWAY        = 1
 TRUST_BIDIRECTIONAL = 3
 
+# Trust join behavior
+# External trust -- allow creating trust to a non-root domain in the forest
+TRUST_JOIN_EXTERNAL = 1
+
+
 def is_sid_valid(sid):
     try:
         security.dom_sid(sid)
@@ -1037,7 +1042,7 @@ class TrustDomainInstance(object):
             # We can ignore the error here -- setting up name suffix routes may fail
             pass
 
-    def establish_trust(self, another_domain, trustdom_secret, trust_type='bidirectional'):
+    def establish_trust(self, another_domain, trustdom_secret, trust_type='bidirectional', trust_external=False):
         """
         Establishes trust between our and another domain
         Input: another_domain -- instance of TrustDomainInstance, initialized with #retrieve call
@@ -1060,6 +1065,8 @@ class TrustDomainInstance(object):
             info.trust_direction |= lsa.LSA_TRUST_DIRECTION_OUTBOUND
         info.trust_type = lsa.LSA_TRUST_TYPE_UPLEVEL
         info.trust_attributes = 0
+        if trust_external:
+            info.trust_attributes |= lsa.LSA_TRUST_ATTRIBUTE_NON_TRANSITIVE
 
         try:
             dname = lsa.String()
@@ -1096,14 +1103,17 @@ class TrustDomainInstance(object):
             # server as that one doesn't support AES encryption types
             pass
 
-        try:
+        if not trust_external:
-            info = self._pipe.QueryTrustedDomainInfo(trustdom_handle, lsa.LSA_TRUSTED_DOMAIN_INFO_INFO_EX)
+            try:
-            info.trust_attributes |= lsa.LSA_TRUST_ATTRIBUTE_FOREST_TRANSITIVE
+                info = self._pipe.QueryTrustedDomainInfo(trustdom_handle,
-            self._pipe.SetInformationTrustedDomain(trustdom_handle, lsa.LSA_TRUSTED_DOMAIN_INFO_INFO_EX, info)
+                                                         lsa.LSA_TRUSTED_DOMAIN_INFO_INFO_EX)
-        except RuntimeError as e:
+                info.trust_attributes |= lsa.LSA_TRUST_ATTRIBUTE_FOREST_TRANSITIVE
-            root_logger.error('unable to set trust to transitive: %s' % (str(e)))
+                self._pipe.SetInformationTrustedDomain(trustdom_handle,
+                                                       lsa.LSA_TRUSTED_DOMAIN_INFO_INFO_EX, info)
+            except RuntimeError as e:
+                root_logger.error('unable to set trust transitivity status: %s' % (str(e)))
 
-        if self.info['is_pdc']:
+        if self.info['is_pdc'] or trust_external:
             self.update_ftinfo(another_domain)
 
     def verify_trust(self, another_domain):
@@ -1262,6 +1272,7 @@ class TrustDomainJoins(object):
         self.api = api
         self.local_domain = None
         self.remote_domain = None
+        self.__allow_behavior = 0
 
         domain_validator = DomainValidator(api)
         self.configured = domain_validator.is_configured()
@@ -1271,6 +1282,10 @@ class TrustDomainJoins(object):
             self.local_dn = domain_validator.dn
             self.__populate_local_domain()
 
+    def allow_behavior(self, *flags):
+        for f in flags:
+            self.__allow_behavior |= int(f)
+
     def __populate_local_domain(self):
         # Initialize local domain info using kerberos only
         ld = TrustDomainInstance(self.local_flatname)
@@ -1358,14 +1373,19 @@ class TrustDomainJoins(object):
                 realm_passwd
             )
 
+        trust_external = bool(self.__allow_behavior & TRUST_JOIN_EXTERNAL)
         if self.remote_domain.info['dns_domain'] != self.remote_domain.info['dns_forest']:
-            raise errors.NotAForestRootError(forest=self.remote_domain.info['dns_forest'], domain=self.remote_domain.info['dns_domain'])
+            if not trust_external:
+                raise errors.NotAForestRootError(forest=self.remote_domain.info['dns_forest'],
+                                                 domain=self.remote_domain.info['dns_domain'])
 
         if not self.remote_domain.read_only:
             trustdom_pass = samba.generate_random_password(128, 128)
             self.get_realmdomains()
-            self.remote_domain.establish_trust(self.local_domain, trustdom_pass, trust_type)
+            self.remote_domain.establish_trust(self.local_domain,
-            self.local_domain.establish_trust(self.remote_domain, trustdom_pass, trust_type)
+                                               trustdom_pass, trust_type, trust_external)
+            self.local_domain.establish_trust(self.remote_domain,
+                                              trustdom_pass, trust_type, trust_external)
             # if trust is inbound, we don't need to verify it because AD DC will respond
             # with WERR_NO_SUCH_DOMAIN -- in only does verification for outbound trusts.
             result = True
@@ -1381,8 +1401,12 @@ class TrustDomainJoins(object):
         if not(isinstance(self.remote_domain, TrustDomainInstance)):
             self.populate_remote_domain(realm, realm_server, realm_passwd=None)
 
+        trust_external = bool(self.__allow_behavior & TRUST_JOIN_EXTERNAL)
         if self.remote_domain.info['dns_domain'] != self.remote_domain.info['dns_forest']:
-            raise errors.NotAForestRootError(forest=self.remote_domain.info['dns_forest'], domain=self.remote_domain.info['dns_domain'])
+            if not trust_external:
+                raise errors.NotAForestRootError(forest=self.remote_domain.info['dns_forest'],
+                                                 domain=self.remote_domain.info['dns_domain'])
 
-        self.local_domain.establish_trust(self.remote_domain, trustdom_passwd, trust_type)
+        self.local_domain.establish_trust(self.remote_domain,
+                                          trustdom_passwd, trust_type, trust_external)
         return dict(local=self.local_domain, remote=self.remote_domain, verified=False)

ipaserver/plugins/trust.py

@@ -62,8 +62,10 @@ except Exception as e:
 
 if api.env.in_server and api.env.context in ['lite', 'server']:
     try:
-        import ipaserver.dcerpc #pylint: disable=F0401
+        import ipaserver.dcerpc  # pylint: disable=F0401
-        from ipaserver.dcerpc import TRUST_ONEWAY, TRUST_BIDIRECTIONAL
+        from ipaserver.dcerpc import (TRUST_ONEWAY,
+                                      TRUST_BIDIRECTIONAL,
+                                      TRUST_JOIN_EXTERNAL)
         import dbus
         import dbus.mainloop.glib
         _bindings_installed = True
@@ -162,11 +164,18 @@ trust_output_params = (
         label=_('Trust type')),
     Str('truststatus',
         label=_('Trust status')),
+    Str('ipantadditionalsuffixes*',
+        label=_('UPN suffixes')),
 )
 
+# Trust type is a combination of ipanttrusttype and ipanttrustattributes
+# We shift trust attributes by 3 bits to left so bit 0 becomes bit 3 and
+# 2+(1 << 3) becomes 10.
 _trust_type_dict = {1 : _('Non-Active Directory domain'),
                     2 : _('Active Directory domain'),
-                    3 : _('RFC4120-compliant Kerberos realm')}
+                    3 : _('RFC4120-compliant Kerberos realm'),
+                    10: _('Non-transitive external trust to a domain in another Active Directory forest')}
+
 _trust_direction_dict = {1 : _('Trusting forest'),
                          2 : _('Trusted forest'),
                          3 : _('Two-way trust')}
@@ -189,14 +198,17 @@ DBUS_IFACE_TRUST = 'com.redhat.idm.trust'
 CRED_STYLE_SAMBA = 1
 CRED_STYLE_KERBEROS = 2
 
-def trust_type_string(level):
+LSA_TRUST_ATTRIBUTE_NON_TRANSITIVE = 0x00000001
+
+def trust_type_string(level, attrs):
     """
     Returns a string representing a type of the trust. The original field is an enum:
       LSA_TRUST_TYPE_DOWNLEVEL  = 0x00000001,
       LSA_TRUST_TYPE_UPLEVEL    = 0x00000002,
       LSA_TRUST_TYPE_MIT        = 0x00000003
     """
-    string = _trust_type_dict.get(int(level), _trust_type_dict_unknown)
+    transitive = int(attrs) & LSA_TRUST_ATTRIBUTE_NON_TRANSITIVE
+    string = _trust_type_dict.get(int(level) | (transitive << 3), _trust_type_dict_unknown)
     return unicode(string)
 
 def trust_direction_string(level):
@@ -677,6 +689,12 @@ sides.
              doc=(_('Establish bi-directional trust. By default trust is inbound one-way only.')),
              default=False,
         ),
+        Bool('external?',
+             label=_('External trust'),
+             cli_name='external',
+             doc=(_('Establish external trust to a domain in another forest. The trust is not transitive beyond the domain.')),
+             default=False,
+        ),
     )
 
     msg_summary = _('Added Active Directory trust for realm "%(value)s"')
@@ -735,12 +753,15 @@ sides.
                 fetch_trusted_domains_over_dbus(self.api, self.log, result['value'])
 
         # Format the output into human-readable values
+        attributes = int(result['result'].get('ipanttrustattributes', [0])[0])
         result['result']['trusttype'] = [trust_type_string(
-            result['result']['ipanttrusttype'][0])]
+            result['result']['ipanttrusttype'][0], attributes)]
         result['result']['trustdirection'] = [trust_direction_string(
             result['result']['ipanttrustdirection'][0])]
         result['result']['truststatus'] = [trust_status_string(
             result['verified'])]
+        if attributes:
+            result['result'].pop('ipanttrustattributes', None)
 
         del result['verified']
         result['result'].pop('ipanttrustauthoutgoing', None)
@@ -929,6 +950,11 @@ sides.
         trust_type = TRUST_ONEWAY
         if options.get('bidirectional', False):
             trust_type = TRUST_BIDIRECTIONAL
+
+        # If we are forced to establish external trust, allow it
+        if options.get('external', False):
+            self.trustinstance.allow_behavior(TRUST_JOIN_EXTERNAL)
+
         # 1. Full access to the remote domain. Use admin credentials and
         # generate random trustdom password to do work on both sides
         if full_join:
@@ -1033,7 +1059,7 @@ class trust_mod(LDAPUpdate):
 class trust_find(LDAPSearch):
     __doc__ = _('Search for trusts.')
     has_output_params = LDAPSearch.has_output_params + trust_output_params +\
-                        (Str('ipanttrusttype'),)
+                        (Str('ipanttrusttype'), Str('ipanttrustattributes'))
 
     msg_summary = ngettext(
         '%(count)d trust matched', '%(count)d trusts matched', 0
@@ -1043,7 +1069,7 @@ class trust_find(LDAPSearch):
     # search needs to be done on a sub-tree scope
     def pre_callback(self, ldap, filters, attrs_list, base_dn, scope, *args, **options):
         # list only trust, not trust domains
-        trust_filter = '(ipaNTTrustPartner=*)'
+        trust_filter = '(&(ipaNTTrustPartner=*)(&(objectclass=ipaIDObject)(objectclass=ipaNTTrustedDomain)))'
         filter = ldap.combine_filters((filters, trust_filter), rules=ldap.MATCH_ALL)
         return (filter, base_dn, ldap.SCOPE_SUBTREE)
 
@@ -1060,10 +1086,13 @@ class trust_find(LDAPSearch):
 
         for attrs in entries:
             # Translate ipanttrusttype to trusttype if --raw not used
-            trust_type = attrs.get('ipanttrusttype', [None])[0]
+            trust_type = attrs.single_value.get('ipanttrusttype', None)
+            attributes = attrs.single_value.get('ipanttrustattributes', 0)
             if not options.get('raw', False) and trust_type is not None:
-                attrs['trusttype'] = trust_type_string(attrs['ipanttrusttype'][0])
+                attrs['trusttype'] = [trust_type_string(trust_type, attributes)]
                 del attrs['ipanttrusttype']
+                if attributes:
+                    del attrs['ipanttrustattributes']
 
         return truncated
 
@@ -1071,7 +1100,7 @@ class trust_find(LDAPSearch):
 class trust_show(LDAPRetrieve):
     __doc__ = _('Display information about a trust.')
     has_output_params = LDAPRetrieve.has_output_params + trust_output_params +\
-                        (Str('ipanttrusttype'), Str('ipanttrustdirection'))
+                        (Str('ipanttrusttype'), Str('ipanttrustdirection'), Str('ipanttrustattributes'))
 
     def execute(self, *keys, **options):
         result = super(trust_show, self).execute(*keys, **options)
@@ -1088,16 +1117,20 @@ class trust_show(LDAPRetrieve):
         # if --raw not used
 
         if not options.get('raw', False):
-            trust_type = entry_attrs.get('ipanttrusttype', [None])[0]
+            trust_type = entry_attrs.single_value.get('ipanttrusttype', None)
+            attributes = entry_attrs.single_value.get('ipanttrustattributes', 0)
             if trust_type is not None:
-                entry_attrs['trusttype'] = trust_type_string(trust_type)
+                entry_attrs['trusttype'] = [trust_type_string(trust_type, attributes)]
                 del entry_attrs['ipanttrusttype']
 
-            dir_str = entry_attrs.get('ipanttrustdirection', [None])[0]
+            dir_str = entry_attrs.single_value.get('ipanttrustdirection', None)
             if dir_str is not None:
                 entry_attrs['trustdirection'] = [trust_direction_string(dir_str)]
                 del entry_attrs['ipanttrustdirection']
 
+            if attributes:
+                del entry_attrs['ipanttrustattributes']
+
         return dn