path: root/ipaserver/dcerpc.py

# Authors:
#     Alexander Bokovoy <abokovoy@redhat.com>
#
# Copyright (C) 2011  Red Hat
# see file 'COPYING' for use and warranty information
#
# Portions (C) Andrew Tridgell, Andrew Bartlett
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# Make sure we only run this module at the server where samba4-python
# package is installed to avoid issues with unavailable modules

from ipalib.plugins.baseldap import *
from ipalib import api, Str, Password, DefaultFrom, _, ngettext, Object
from ipalib.parameters import Enum
from ipalib import Command
from ipalib import errors
from ipapython import ipautil
from ipapython.ipa_log_manager import *
from ipapython.dn import DN
from ipaserver.install import installutils

import os, string, struct, copy
import uuid
from samba import param
from samba import credentials
from samba.dcerpc import security, lsa, drsblobs, nbt, netlogon
from samba.ndr import ndr_pack
from samba import net
import samba
import random
from Crypto.Cipher import ARC4
try:
    from ldap.controls import RequestControl as LDAPControl #pylint: disable=F0401
except ImportError:
    from ldap.controls import LDAPControl as LDAPControl    #pylint: disable=F0401
import ldap as _ldap
from ipaserver.ipaldap import IPAdmin
from ipalib.session import krbccache_dir, krbccache_prefix
from dns import resolver, rdatatype
from dns.exception import DNSException

__doc__ = _("""
Classes to manage trust joins using DCE-RPC calls

The code in this module relies heavily on samba4-python package
and Samba4 python bindings.
""")

access_denied_error =  errors.ACIError(info=_('CIFS server denied your credentials'))
dcerpc_error_codes = {
    -1073741823:
        errors.RemoteRetrieveError(reason=_('communication with CIFS server was unsuccessful')),
    -1073741790: access_denied_error,
    -1073741715: access_denied_error,
    -1073741614: access_denied_error,
    -1073741603:
        errors.ValidationError(name=_('AD domain controller'), error=_('unsupported functional level')),
}

dcerpc_error_messages = {
    "NT_STATUS_OBJECT_NAME_NOT_FOUND":
         errors.NotFound(reason=_('Cannot find specified domain or server name')),
    "NT_STATUS_INVALID_PARAMETER_MIX":
         errors.RequirementError(name=_('At least the domain or IP address should be specified')),
}

def assess_dcerpc_exception(num=None,message=None):
    """
    Takes error returned by Samba bindings and converts it into
    an IPA error class.
    """
    if num and num in dcerpc_error_codes:
        return dcerpc_error_codes[num]
    if message and message in dcerpc_error_messages:
        return dcerpc_error_messages[message]
    reason = _('''CIFS server communication error: code "%(num)s",
                  message "%(message)s" (both may be "None")''') % dict(num=num, message=message)
    return errors.RemoteRetrieveError(reason=reason)

class ExtendedDNControl(LDAPControl):
    # This class attempts to implement LDAP control that would work
    # with both python-ldap 2.4.x and 2.3.x, thus there is mix of properties
    # from both worlds and encodeControlValue has default parameter
    def __init__(self):
        self.controlValue = 1
        self.controlType = "1.2.840.113556.1.4.529"
        self.criticality = False
        self.integerValue = 1

    def encodeControlValue(self, value=None):
        return '0\x03\x02\x01\x01'

class DomainValidator(object):
    ATTR_FLATNAME = 'ipantflatname'
    ATTR_SID = 'ipantsecurityidentifier'
    ATTR_TRUSTED_SID = 'ipanttrusteddomainsid'
    ATTR_TRUST_PARTNER = 'ipanttrustpartner'
    ATTR_TRUST_AUTHOUT = 'ipanttrustauthoutgoing'

    def __init__(self, api):
        self.api = api
        self.ldap = self.api.Backend.ldap2
        self.domain = None
        self.flatname = None
        self.dn = None
        self.sid = None
        self._domains = None
        self._info = dict()
        self._creds = None
        self._parm = None

    def is_configured(self):
        cn_trust_local = DN(('cn', self.api.env.domain), self.api.env.container_cifsdomains, self.api.env.basedn)
        try:
            (dn, entry_attrs) = self.ldap.get_entry(cn_trust_local, [self.ATTR_FLATNAME, self.ATTR_SID])
            self.flatname = entry_attrs[self.ATTR_FLATNAME][0]
            self.sid = entry_attrs[self.ATTR_SID][0]
            self.dn = dn
            self.domain = self.api.env.domain
        except errors.NotFound, e:
            return False
        return True

    def get_trusted_domains(self):
        """Returns dict of trusted domain tuples (flatname, sid, trust_auth_outgoing), keyed by domain name"""
        cn_trust = DN(('cn', 'ad'), self.api.env.container_trusts, self.api.env.basedn)
        try:
            search_kw = {'objectClass': 'ipaNTTrustedDomain'}
            filter = self.ldap.make_filter(search_kw, rules=self.ldap.MATCH_ALL)
            (entries, truncated) = self.ldap.find_entries(filter=filter, base_dn=cn_trust,
                                                          attrs_list=[self.ATTR_TRUSTED_SID,
                                                                      self.ATTR_FLATNAME,
                                                                      self.ATTR_TRUST_PARTNER,
                                                                      self.ATTR_TRUST_AUTHOUT])

            result = dict()
            for entry in entries:
                result[entry[1][self.ATTR_TRUST_PARTNER][0]] = (entry[1][self.ATTR_FLATNAME][0].lower(),
                                                                security.dom_sid(entry[1][self.ATTR_TRUSTED_SID][0]),
                                                                entry[1][self.ATTR_TRUST_AUTHOUT][0])
            return result
        except errors.NotFound, e:
            return []

    def is_trusted_sid_valid(self, sid):
        if not self.domain:
            # our domain is not configured or self.is_configured() never run
            # reject SIDs as we can't check correctness of them
            return False
        # Parse sid string to see if it is really in a SID format
        try:
            test_sid = security.dom_sid(sid)
        except TypeError, e:
            return False
        # At this point we have SID_NT_AUTHORITY family SID and really need to
        # check it against prefixes of domain SIDs we trust to
        if not self._domains:
            self._domains = self.get_trusted_domains()
        if len(self._domains) == 0:
            # Our domain is configured but no trusted domains are configured
            # This means we can't check the correctness of a trusted domain SIDs
            return False
        # We have non-zero list of trusted domains and have to go through them
        # one by one and check their sids as prefixes
        test_sid_subauths = test_sid.sub_auths
        for domain in self._domains:
            domsid = self._domains[domain][1]
            sub_auths = domsid.sub_auths
            num_auths = min(test_sid.num_auths, domsid.num_auths)
            if test_sid_subauths[:num_auths] == sub_auths[:num_auths]:
                return True
        return False

    def normalize_name(self, name):
        result = dict()
        components = name.split('@')
        if len(components) == 2:
            result['domain'] = unicode(components[1]).lower()
            result['name'] = unicode(components[0]).lower()
        else:
            components = name.split('\\')
            if len(components) == 2:
                result['flatname'] = unicode(components[0]).lower()
                result['name'] = unicode(components[1]).lower()
            else:
                result['name'] = unicode(name).lower()
        return result

    def get_sid_trusted_domain_object(self, object_name):
        """Returns SID for the trusted domain object (user or group only)"""
        if not self.domain:
            # our domain is not configured or self.is_configured() never run
            return None
        if not self._domains:
            self._domains = self.get_trusted_domains()
        if len(self._domains) == 0:
            # Our domain is configured but no trusted domains are configured
            return None
        components = self.normalize_name(object_name)
        if not ('domain' in components or 'flatname' in components):
            # No domain or realm specified, ambiguous search
            return False

        entry = None
        if 'domain' in components and components['domain'] in self._domains:
            # Now we have a name to check against our list of trusted domains
            entry = self.resolve_against_gc(components['domain'], components['name'])
        elif 'flatname' in components:
            # Flatname was specified, traverse through the list of trusted
            # domains first to find the proper one
            for domain in self._domains:
                if self._domains[domain][0] == components['flatname']:
                    entry = self.resolve_against_gc(domain, components['name'])
                    if entry:
                        break
        if entry:
            try:
                test_sid = security.dom_sid(entry)
                return unicode(test_sid)
            except TypeError, e:
                return False
        return False

    def __sid_to_str(self, sid):
        """
        Converts binary SID to string representation
        Returns unicode string
        """
        sid_rev_num = ord(sid[0])
        number_sub_id = ord(sid[1])
        ia = struct.unpack('!Q','\x00\x00'+sid[2:8])[0]
        subs = [
            struct.unpack('<I',sid[8+4*i:12+4*i])[0]
            for i in range(number_sub_id)
        ]
        return u'S-%d-%d-%s' % ( sid_rev_num, ia, '-'.join([str(s) for s in subs]),)

    def __extract_trusted_auth(self, info):
        """
        Returns in clear trusted domain account credentials
        """
        clear = None
        auth = drsblobs.trustAuthInOutBlob()
        auth.__ndr_unpack__(info['auth'])
        auth_array = auth.current.array[0]
        if auth_array.AuthType == lsa.TRUST_AUTH_TYPE_CLEAR:
            clear = ''.join(map(chr, auth_array.AuthInfo.password)).decode('utf-16-le')
        return clear

    def __kinit_as_trusted_account(self, info, password):
        """
        Initializes ccache with trusted domain account credentials.

        Applies session code defaults for ccache directory and naming prefix.
        Session code uses krbccache_prefix+<pid>, we use
        krbccache_prefix+<TD>+<domain netbios name> so there is no clash

        Returns tuple (ccache name, principal) where (None, None) signifes an error
        on ccache initialization
        """
        ccache_name = os.path.join(krbccache_dir, "%sTD%s" % (krbccache_prefix, info['name'][0]))
        principal = '%s$@%s' % (self.flatname, info['dns_domain'].upper())
        (stdout, stderr, returncode) = ipautil.run(['/usr/bin/kinit', principal],
                                                   env={'KRB5CCNAME':ccache_name},
                                                   stdin=password, raiseonerr=False)
        if returncode == 0:
            return (ccache_name, principal)
        else:
            return (None, None)

    def resolve_against_gc(self, domain, name):
        """
        Resolves `name' against trusted domain `domain' using Global Catalog
        Returns SID of the `name' or None
        """
        entry = None
        sid = None
        info = self.__retrieve_trusted_domain_gc_list(domain)
        if not info:
            return None
        for (host, port) in info['gc']:
            entry = self.__resolve_against_gc(info, host, port, name)
            if entry:
                break

        if entry:
            l = len(entry)
            if l > 2:
                # Treat non-unique entries as invalid
                return None
            sid = self.__sid_to_str(entry[0][1]['objectSid'][0])
        return sid

    def __resolve_against_gc(self, info, host, port, name):
        """
        Actual resolution against LDAP server, using SASL GSSAPI authentication
        Returns LDAP result or None
        """
        conn = IPAdmin(host=host, port=port)
        auth = self.__extract_trusted_auth(info)
        if auth:
            (ccache_name, principal) = self.__kinit_as_trusted_account(info, auth)
            if ccache_name:
                cb_info = dict()
                # pass empty dict, SASL GSSAPI is able to get all from the ccache
                sasl_auth = _ldap.sasl.sasl(cb_info,'GSSAPI')
                old_ccache = os.environ.get('KRB5CCNAME')
                os.environ["KRB5CCNAME"] = ccache_name
                # OPT_X_SASL_NOCANON is used to avoid hard requirement for PTR
                # records pointing back to the same host name
                conn.set_option(_ldap.OPT_X_SASL_NOCANON, _ldap.OPT_ON)
                conn.sasl_interactive_bind_s(None, sasl_auth)
                base = DN(*map(lambda p: ('dc', p), info['dns_domain'].split('.')))
                # We don't use conn.getEntry() because it will attempt to fetch schema from GC and that will fail
                filterstr = conn.encode('(&(sAMAccountName=%(name)s)(|(objectClass=user)(objectClass=group)))' % dict(name=name))
                attrlist = conn.encode(['sAMAccountName', 'sAMAccountType', 'objectSid', 'groupType', 'description'])
                entry = conn.conn.search_s(str(base), _ldap.SCOPE_SUBTREE, filterstr, attrlist, 0)
                os.environ["KRB5CCNAME"] = old_ccache
                return entry

    def __retrieve_trusted_domain_gc_list(self, domain):
        """
        Retrieves domain information and preferred GC list
        Returns dictionary with following keys
             name       -- NetBIOS name of the trusted domain
             dns_domain -- DNS name of the trusted domain
             auth       -- encrypted credentials for trusted domain account
             gc         -- array of tuples (server, port) for Global Catalog
        """
        if domain in self._info:
            return self._info[domain]

        if not self._creds:
            self._parm = param.LoadParm()
            self._parm.load(os.path.join(ipautil.SHARE_DIR,"smb.conf.empty"))
            self._parm.set('netbios name', self.flatname)
            self._creds = credentials.Credentials()
            self._creds.set_kerberos_state(credentials.MUST_USE_KERBEROS)
            self._creds.guess(self._parm)
            self._creds.set_workstation(self.flatname)

        netrc = net.Net(creds=self._creds, lp=self._parm)
        finddc_error = None
        result = None
        try:
            result = netrc.finddc(domain=domain, flags=nbt.NBT_SERVER_LDAP | nbt.NBT_SERVER_GC)
        except RuntimeError, e:
            finddc_error = e

        info = dict()
        info['auth'] = self._domains[domain][2]
        servers = []
        if result:
            info['name'] = unicode(result.domain_name)
            info['dns_domain'] = unicode(result.dns_domain)
            servers = [(unicode(result.pdc_dns_name), 3268)]
        else:
            info['name'] = self._domains[domain]
            info['dns_domain'] = domain
            # Retrieve GC servers list
            gc_name = '_gc._tcp.%s.' % info['dns_domain']

            try:
                answers = resolver.query(gc_name, rdatatype.SRV)
            except DNSException, e:
                answers = []

            for answer in answers:
                server = str(answer.target).rstrip(".")
                servers.append((server, answer.port))

        info['gc'] = servers

        # Both methods should not fail at the same time
        if finddc_error and len(info['gc']) == 0:
            raise assess_dcerpc_exception(message=str(finddc_error))

        self._info[domain] = info
        return info


class TrustDomainInstance(object):

    def __init__(self, hostname, creds=None):
        self.parm = param.LoadParm()
        self.parm.load(os.path.join(ipautil.SHARE_DIR,"smb.conf.empty"))
        if len(hostname) > 0:
            self.parm.set('netbios name', hostname)
        self.creds = creds
        self.hostname = hostname
        self.info = {}
        self._pipe = None
        self._policy_handle = None
        self.read_only = False

    def __gen_lsa_connection(self, binding):
       if self.creds is None:
           raise errors.RequirementError(name=_('CIFS credentials object'))
       try:
           result = lsa.lsarpc(binding, self.parm, self.creds)
           return result
       except RuntimeError, (num, message):
           raise assess_dcerpc_exception(num=num, message=message)

    def __init_lsa_pipe(self, remote_host):
        """
        Try to initialize connection to the LSA pipe at remote host.
        This method tries consequently all possible transport options
        and selects one that works. See __gen_lsa_bindings() for details.

        The actual result may depend on details of existing credentials.
        For example, using signing causes NO_SESSION_KEY with Win2K8 and
        using kerberos against Samba with signing does not work.
        """
        # short-cut: if LSA pipe is initialized, skip completely
        if self._pipe:
            return

        attempts = 0
        bindings = self.__gen_lsa_bindings(remote_host)
        for binding in bindings:
            try:
                self._pipe = self.__gen_lsa_connection(binding)
                if self._pipe:
                    break
            except errors.ACIError, e:
                attempts = attempts + 1

        if self._pipe is None and attempts == len(bindings):
            raise errors.ACIError(
                info=_('CIFS server %(host)s denied your credentials') % dict(host=remote_host))

        if self._pipe is None:
            raise errors.RemoteRetrieveError(
                reason=_('Cannot establish LSA connection to %(host)s. Is CIFS server running?') % dict(host=remote_host))
        self.binding = binding

    def __gen_lsa_bindings(self, remote_host):
        """
        There are multiple transports to issue LSA calls. However, depending on a
        system in use they may be blocked by local operating system policies.
        Generate all we can use. __init_lsa_pipe() will try them one by one until
        there is one working.

        We try NCACN_NP before NCACN_IP_TCP and signed sessions before unsigned.
        """
        transports = (u'ncacn_np', u'ncacn_ip_tcp')
        options = ( u',', u'')
        binding_template=lambda x,y,z: u'%s:%s[%s]' % (x, y, z)
        return [binding_template(t, remote_host, o) for t in transports for o in options]

    def retrieve_anonymously(self, remote_host, discover_srv=False):
        """
        When retrieving DC information anonymously, we can't get SID of the domain
        """
        netrc = net.Net(creds=self.creds, lp=self.parm)
        try:
            if discover_srv:
                result = netrc.finddc(domain=remote_host, flags=nbt.NBT_SERVER_LDAP | nbt.NBT_SERVER_DS)
            else:
                result = netrc.finddc(address=remote_host, flags=nbt.NBT_SERVER_LDAP | nbt.NBT_SERVER_DS)
        except RuntimeError, e:
            raise assess_dcerpc_exception(message=str(e))

        if not result:
            return False
        self.info['name'] = unicode(result.domain_name)
        self.info['dns_domain'] = unicode(result.dns_domain)
        self.info['dns_forest'] = unicode(result.forest)
        self.info['guid'] = unicode(result.domain_uuid)
        self.info['dc'] = unicode(result.pdc_dns_name)

        # Netlogon response doesn't contain SID of the domain.
        # We need to do rootDSE search with LDAP_SERVER_EXTENDED_DN_OID control to reveal the SID
        ldap_uri = 'ldap://%s' % (result.pdc_dns_name)
        conn = _ldap.initialize(ldap_uri)
        conn.set_option(_ldap.OPT_SERVER_CONTROLS, [ExtendedDNControl()])
        result = None
        try:
            (objtype, res) = conn.search_s('', _ldap.SCOPE_BASE)[0]
            result = res['defaultNamingContext'][0]
            self.info['dns_hostname'] = res['dnsHostName'][0]
        except _ldap.LDAPError, e:
            root_logger.error(
                "LDAP error when connecting to %(host)s: %(error)s" %
                    dict(host=unicode(result.pdc_name), error=str(e)))

        if result:
           self.info['sid'] = self.parse_naming_context(result)
        return True

    def parse_naming_context(self, context):
        naming_ref = re.compile('.*<SID=(S-.*)>.*')
        return naming_ref.match(context).group(1)

    def retrieve(self, remote_host):
        self.__init_lsa_pipe(remote_host)

        objectAttribute = lsa.ObjectAttribute()
        objectAttribute.sec_qos = lsa.QosInfo()
        try:
            self._policy_handle = self._pipe.OpenPolicy2(u"", objectAttribute, security.SEC_FLAG_MAXIMUM_ALLOWED)
            result = self._pipe.QueryInfoPolicy2(self._policy_handle, lsa.LSA_POLICY_INFO_DNS)
        except RuntimeError, (num, message):
            raise assess_dcerpc_exception(num=num, message=message)

        self.info['name'] = unicode(result.name.string)
        self.info['dns_domain'] = unicode(result.dns_domain.string)
        self.info['dns_forest'] = unicode(result.dns_forest.string)
        self.info['guid'] = unicode(result.domain_guid)
        self.info['sid'] = unicode(result.sid)
        self.info['dc'] = remote_host

    def generate_auth(self, trustdom_secret):
        def arcfour_encrypt(key, data):
            c = ARC4.new(key)
            return c.encrypt(data)
        def string_to_array(what):
            blob = [0] * len(what)

            for i in range(len(what)):
                blob[i] = ord(what[i])
            return blob

        password_blob = string_to_array(trustdom_secret.encode('utf-16-le'))

        clear_value = drsblobs.AuthInfoClear()
        clear_value.size = len(password_blob)
        clear_value.password = password_blob

        clear_authentication_information = drsblobs.AuthenticationInformation()
        clear_authentication_information.LastUpdateTime = samba.unix2nttime(int(time.time()))
        clear_authentication_information.AuthType = lsa.TRUST_AUTH_TYPE_CLEAR
        clear_authentication_information.AuthInfo = clear_value

        authentication_information_array = drsblobs.AuthenticationInformationArray()
        authentication_information_array.count = 1
        authentication_information_array.array = [clear_authentication_information]

        outgoing = drsblobs.trustAuthInOutBlob()
        outgoing.count = 1
        outgoing.current = authentication_information_array

        confounder = [3]*512
        for i in range(512):
            confounder[i] = random.randint(0, 255)

        trustpass = drsblobs.trustDomainPasswords()
        trustpass.confounder = confounder

        trustpass.outgoing = outgoing
        trustpass.incoming = outgoing

        trustpass_blob = ndr_pack(trustpass)

        encrypted_trustpass = arcfour_encrypt(self._pipe.session_key, trustpass_blob)

        auth_blob = lsa.DATA_BUF2()
        auth_blob.size = len(encrypted_trustpass)
        auth_blob.data = string_to_array(encrypted_trustpass)

        auth_info = lsa.TrustDomainInfoAuthInfoInternal()
        auth_info.auth_blob = auth_blob
        self.auth_info = auth_info



    def establish_trust(self, another_domain, trustdom_secret):
        """
        Establishes trust between our and another domain
        Input: another_domain -- instance of TrustDomainInstance, initialized with #retrieve call
               trustdom_secret -- shared secred used for the trust
        """
        self.generate_auth(trustdom_secret)

        info = lsa.TrustDomainInfoInfoEx()
        info.domain_name.string = another_domain.info['dns_domain']
        info.netbios_name.string = another_domain.info['name']
        info.sid = security.dom_sid(another_domain.info['sid'])
        info.trust_direction = lsa.LSA_TRUST_DIRECTION_INBOUND | lsa.LSA_TRUST_DIRECTION_OUTBOUND
        info.trust_type = lsa.LSA_TRUST_TYPE_UPLEVEL
        info.trust_attributes = lsa.LSA_TRUST_ATTRIBUTE_FOREST_TRANSITIVE

        try:
            dname = lsa.String()
            dname.string = another_domain.info['dns_domain']
            res = self._pipe.QueryTrustedDomainInfoByName(self._policy_handle, dname, lsa.LSA_TRUSTED_DOMAIN_INFO_FULL_INFO)
            self._pipe.DeleteTrustedDomain(self._policy_handle, res.info_ex.sid)
        except RuntimeError, e:
            pass
        try:
            trustdom_handle = self._pipe.CreateTrustedDomainEx2(self._policy_handle, info, self.auth_info, security.SEC_STD_DELETE)
        except RuntimeError, (num, message):
            raise assess_dcerpc_exception(num=num, message=message)

        try:
            infoclass = lsa.TrustDomainInfoSupportedEncTypes()
            infoclass.enc_types = security.KERB_ENCTYPE_RC4_HMAC_MD5
            infoclass.enc_types |= security.KERB_ENCTYPE_AES128_CTS_HMAC_SHA1_96
            infoclass.enc_types |= security.KERB_ENCTYPE_AES256_CTS_HMAC_SHA1_96
            self._pipe.SetInformationTrustedDomain(trustdom_handle, lsa.LSA_TRUSTED_DOMAIN_SUPPORTED_ENCRYPTION_TYPES, infoclass)
        except RuntimeError, e:
            pass

    def verify_trust(self, another_domain):
        def retrieve_netlogon_info_2(domain, function_code, data):
            try:
                netr_pipe = netlogon.netlogon(domain.binding, domain.parm, domain.creds)
                result = netr_pipe.netr_LogonControl2Ex(logon_server=None,
                                           function_code=function_code,
                                           level=2,
                                           data=data
                                           )
                return result
            except RuntimeError, (num, message):
                raise assess_dcerpc_exception(num=num, message=message)

        result = retrieve_netlogon_info_2(self,
                                          netlogon.NETLOGON_CONTROL_TC_VERIFY,
                                          another_domain.info['dns_domain'])
        if (result and (result.flags and netlogon.NETLOGON_VERIFY_STATUS_RETURNED)):
            # netr_LogonControl2Ex() returns non-None result only if overall call
            # result was WERR_OK which means verification was correct.
            # We only check that it was indeed status for verification process
            return True
        return False

class TrustDomainJoins(object):
    def __init__(self, api):
        self.api = api
        self.local_domain = None
        self.remote_domain = None

        domain_validator = DomainValidator(api)
        self.configured = domain_validator.is_configured()

        if self.configured:
            self.local_flatname = domain_validator.flatname
            self.local_dn = domain_validator.dn
            self.__populate_local_domain()

    def __populate_local_domain(self):
        # Initialize local domain info using kerberos only
        ld = TrustDomainInstance(self.local_flatname)
        ld.creds = credentials.Credentials()
        ld.creds.set_kerberos_state(credentials.MUST_USE_KERBEROS)
        ld.creds.guess(ld.parm)
        ld.creds.set_workstation(ld.hostname)
        ld.retrieve(installutils.get_fqdn())
        self.local_domain = ld

    def __populate_remote_domain(self, realm, realm_server=None, realm_admin=None, realm_passwd=None):
        def get_instance(self):
            # Fetch data from foreign domain using password only
            rd = TrustDomainInstance('')
            rd.parm.set('workgroup', self.local_domain.info['name'])
            rd.creds = credentials.Credentials()
            rd.creds.set_kerberos_state(credentials.DONT_USE_KERBEROS)
            rd.creds.guess(rd.parm)
            return rd

        rd = get_instance(self)
        rd.creds.set_anonymous()
        rd.creds.set_workstation(self.local_domain.hostname)
        if realm_server is None:
            rd.retrieve_anonymously(realm, discover_srv=True)
        else:
            rd.retrieve_anonymously(realm_server, discover_srv=False)
        rd.read_only = True
        if realm_admin and realm_passwd:
            if 'name' in rd.info:
                names = realm_admin.split('\\')
                if len(names) > 1:
                    # realm admin is in DOMAIN\user format
                    # strip DOMAIN part as we'll enforce the one discovered
                    realm_admin = names[-1]
                auth_string = u"%s\%s%%%s" % (rd.info['name'], realm_admin, realm_passwd)
                td = get_instance(self)
                td.creds.parse_string(auth_string)
                td.creds.set_workstation(self.local_domain.hostname)
                if realm_server is None:
                    # we must have rd.info['dns_hostname'] then, part of anonymous discovery
                    td.retrieve(rd.info['dns_hostname'])
                else:
                    td.retrieve(realm_server)
                td.read_only = False
                self.remote_domain = td
                return
        # Otherwise, use anonymously obtained data
        self.remote_domain = rd

    def join_ad_full_credentials(self, realm, realm_server, realm_admin, realm_passwd):
        if not self.configured:
            return None

        self.__populate_remote_domain(realm, realm_server, realm_admin, realm_passwd)
        if not self.remote_domain.read_only:
            trustdom_pass = samba.generate_random_password(128, 128)
            self.remote_domain.establish_trust(self.local_domain, trustdom_pass)
            self.local_domain.establish_trust(self.remote_domain, trustdom_pass)
            result = self.remote_domain.verify_trust(self.local_domain)
            return dict(local=self.local_domain, remote=self.remote_domain, verified=result)
        return None

    def join_ad_ipa_half(self, realm, realm_server, trustdom_passwd):
        if not self.configured:
            return None

        self.__populate_remote_domain(realm, realm_server, realm_passwd=None)
        self.local_domain.establish_trust(self.remote_domain, trustdom_passwd)
        return dict(local=self.local_domain, remote=self.remote_domain, verified=False)