Coverage for ipaserver/install/replication : 10%

# Authors: Karl MacMillan <kmacmillan@mentalrootkit.com> 

# 

# Copyright (C) 2007  Red Hat 

# see file 'COPYING' for use and warranty information 

# 

# 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/>. 

# 

import time 

import datetime 

import sys 

import os 

import ldap 

from ipalib import api, errors 

from ipapython import services as ipaservices 

from ipapython.ipa_log_manager import * 

from ipapython import ipautil, dogtag, ipaldap 

from ipapython.dn import DN 

CACERT = "/etc/ipa/ca.crt" 

# the default container used by AD for user entries 

WIN_USER_CONTAINER = DN(('cn', 'Users')) 

# the default container used by IPA for user entries 

IPA_USER_CONTAINER = DN(('cn', 'users'), ('cn', 'accounts')) 

PORT = 636 

TIMEOUT = 120 

REPL_MAN_DN = DN(('cn', 'replication manager'), ('cn', 'config')) 

DNA_DN = DN(('cn', 'Posix IDs'), ('cn', 'Distributed Numeric Assignment Plugin'), ('cn', 'plugins'), ('cn', 'config')) 

IPA_REPLICA = 1 

WINSYNC = 2 

# List of attributes that need to be excluded from replication initialization. 

TOTAL_EXCLUDES = ('entryusn', 

                 'krblastsuccessfulauth', 

                 'krblastfailedauth', 

                 'krbloginfailedcount') 

# List of attributes that need to be excluded from normal replication. 

EXCLUDES = ('memberof', 'idnssoaserial') + TOTAL_EXCLUDES 

# List of attributes that are not updated on empty replication 

STRIP_ATTRS = ('modifiersName', 

               'modifyTimestamp', 

               'internalModifiersName', 

               'internalModifyTimestamp') 

def replica_conn_check(master_host, host_name, realm, check_ca, 

                       dogtag_master_ds_port, admin_password=None): 

    """ 

    Check the ports used by the replica both locally and remotely to be sure 

    that replication will work. 

    Does not return a value, will sys.exit() on failure. 

    """ 

    print "Run connection check to master" 

    args = ["/usr/sbin/ipa-replica-conncheck", "--master", master_host, 

            "--auto-master-check", "--realm", realm, 

            "--principal", "admin", 

            "--hostname", host_name] 

    nolog=tuple() 

    if admin_password: 

        args.extend(["--password", admin_password]) 

        nolog=(admin_password,) 

    if check_ca and dogtag_master_ds_port == dogtag.Dogtag9Constants.DS_PORT: 

        args.append('--check-ca') 

    (stdin, stderr, returncode) = ipautil.run( 

        args, raiseonerr=False, capture_output=False, nolog=nolog) 

    if returncode != 0: 

        sys.exit("Connection check failed!" + 

                 "\nPlease fix your network settings according to error messages above." + 

                 "\nIf the check results are not valid it can be skipped with --skip-conncheck parameter.") 

    else: 

        print "Connection check OK" 

def enable_replication_version_checking(hostname, realm, dirman_passwd): 

    """ 

    Check the replication version checking plugin. If it is not 

    enabled then enable it and restart 389-ds. If it is enabled 

    the do nothing. 

    """ 

    conn = ipaldap.IPAdmin(hostname, realm=realm, ldapi=True) 

    if dirman_passwd: 

        conn.do_simple_bind(bindpw=dirman_passwd) 

    else: 

        conn.do_sasl_gssapi_bind() 

    entry = conn.get_entry(DN(('cn', 'IPA Version Replication'), 

                              ('cn', 'plugins'), 

                              ('cn', 'config'))) 

    if entry.single_value('nsslapd-pluginenabled', None) == 'off': 

        conn.modify_s(entry.dn, [(ldap.MOD_REPLACE, 'nsslapd-pluginenabled', 'on')]) 

        conn.unbind() 

        serverid = "-".join(realm.split(".")) 

        ipaservices.knownservices.dirsrv.restart(instance_name=serverid) 

    else: 

        conn.unbind() 

def wait_for_task(conn, dn): 

    """Check task status 

    Task is complete when the nsTaskExitCode attr is set. 

    :return: the task's return code 

    """ 

    assert isinstance(dn, DN) 

    attrlist = [ 

        'nsTaskLog', 'nsTaskStatus', 'nsTaskExitCode', 'nsTaskCurrentItem', 

        'nsTaskTotalItems'] 

    while True: 

        entry = conn.get_entry(dn, attrlist) 

        if entry.single_value('nsTaskExitCode', None): 

            exit_code = int(entry.single_value('nsTaskExitCode')) 

            break 

        time.sleep(1) 

    return exit_code 

def wait_for_entry(connection, entry, timeout=7200, attr='', quiet=True): 

    """Wait for entry and/or attr to show up""" 

    filter = "(objectclass=*)" 

    attrlist = [] 

    if attr: 

        filter = "(%s=*)" % attr 

        attrlist.append(attr) 

    timeout += int(time.time()) 

    dn = entry.dn 

    if not quiet: 

        sys.stdout.write("Waiting for %s %s:%s " % (connection, dn, attr)) 

        sys.stdout.flush() 

    entry = None 

    while not entry and int(time.time()) < timeout: 

        try: 

            [entry] = connection.get_entries( 

                dn, ldap.SCOPE_BASE, filter, attrlist) 

        except errors.NotFound: 

            pass  # no entry yet 

        except Exception, e:  # badness 

            print "\nError reading entry", dn, e 

            break 

        if not entry: 

            if not quiet: 

                sys.stdout.write(".") 

                sys.stdout.flush() 

            time.sleep(1) 

    if not entry and int(time.time()) > timeout: 

        print "\nwait_for_entry timeout for %s for %s" % (connection, dn) 

    elif entry and not quiet: 

        print "\nThe waited for entry is:", entry 

    elif not entry: 

        print "\nError: could not read entry %s from %s" % (dn, connection) 

class ReplicationManager(object): 

    """Manage replication agreements between DS servers, and sync 

    agreements with Windows servers""" 

    def __init__(self, realm, hostname, dirman_passwd, port=PORT, starttls=False, conn=None): 

        self.hostname = hostname 

        self.port = port 

        self.dirman_passwd = dirman_passwd 

        self.realm = realm 

        self.starttls = starttls 

        self.suffix = ipautil.realm_to_suffix(realm) 

        self.need_memberof_fixup = False 

        # The caller is allowed to pass in an existing IPAdmin connection. 

        # Open a new one if not provided 

        if conn is None: 

            # If we are passed a password we'll use it as the DM password 

            # otherwise we'll do a GSSAPI bind. 

            if starttls: 

                self.conn = ipaldap.IPAdmin( 

                    hostname, port=port, cacert=CACERT, protocol='ldap', 

                    start_tls=True) 

            else: 

                self.conn = ipaldap.IPAdmin(hostname, port=port, cacert=CACERT) 

            if dirman_passwd: 

                self.conn.do_simple_bind(bindpw=dirman_passwd) 

            else: 

                self.conn.do_sasl_gssapi_bind() 

        else: 

            self.conn = conn 

        self.repl_man_passwd = dirman_passwd 

        # these are likely constant, but you could change them 

        # at runtime if you really want 

        self.repl_man_dn = REPL_MAN_DN 

        self.repl_man_cn = "replication manager" 

    def _get_replica_id(self, conn, master_conn): 

        """ 

        Returns the replica ID which is unique for each backend. 

        conn is the connection we are trying to get the replica ID for. 

        master_conn is the master we are going to replicate with. 

        """ 

        # First see if there is already one set 

        dn = self.replica_dn() 

        assert isinstance(dn, DN) 

        try: 

            replica = conn.get_entry(dn) 

        except errors.NotFound: 

            pass 

        else: 

            if replica.single_value('nsDS5ReplicaId', None): 

                return int(replica.single_value('nsDS5ReplicaId')) 

        # Ok, either the entry doesn't exist or the attribute isn't set 

        # so get it from the other master 

        retval = -1 

        dn = DN(('cn','replication'),('cn','etc'), self.suffix) 

        try: 

            replica = master_conn.get_entry(dn) 

        except errors.NotFound: 

            root_logger.debug("Unable to retrieve nsDS5ReplicaId from remote server") 

            raise 

        else: 

            if replica.single_value('nsDS5ReplicaId', None) is None: 

                root_logger.debug("Unable to retrieve nsDS5ReplicaId from remote server") 

                raise RuntimeError("Unable to retrieve nsDS5ReplicaId from remote server") 

        # Now update the value on the master 

        retval = int(replica.single_value('nsDS5ReplicaId')) 

        mod = [(ldap.MOD_REPLACE, 'nsDS5ReplicaId', str(retval + 1))] 

        try: 

            master_conn.modify_s(dn, mod) 

        except Exception, e: 

            root_logger.debug("Problem updating nsDS5ReplicaID %s" % e) 

            raise 

        return retval 

    def get_agreement_filter(self, agreement_types=None, host=None): 

        """ 

        Get an LDAP replication agreement filter with a possibility to filter 

        the agreements by their type and a host 

        """ 

        if agreement_types is None: 

            agreement_types = (IPA_REPLICA, WINSYNC) 

        elif not isinstance(agreement_types, (list, tuple)): 

            agreement_types = (agreement_types,) 

        agreement_types_filters = [] 

        if IPA_REPLICA in agreement_types: 

            agreement_types_filters.append('(&(objectclass=nsds5ReplicationAgreement)(nsDS5ReplicaRoot=%s))' 

                % self.suffix) 

        if WINSYNC in agreement_types: 

            agreement_types_filters.append('(objectclass=nsDSWindowsReplicationAgreement)') 

        if len(agreement_types_filters) > 1: 

            agreement_filter = '(|%s)' % ''.join(agreement_types_filters) 

        else: 

            agreement_filter = ''.join(agreement_types_filters) 

        if host is not None: 

            agreement_filter = '(&%s(nsDS5ReplicaHost=%s))' % (agreement_filter, host) 

        return agreement_filter 

    def find_replication_agreements(self): 

        """ 

        The replication agreements are stored in 

        cn="$SUFFIX",cn=mapping tree,cn=config 

        FIXME: Rather than failing with a read error if a user tries 

        to read this it simply returns zero entries. We need to use 

        GER to determine if we are allowed to read this to return a proper 

        response. For now just return "No entries" even if the user may 

        not be allowed to see them. 

        """ 

        filt = self.get_agreement_filter() 

        try: 

            ents = self.conn.get_entries( 

                DN(('cn', 'mapping tree'), ('cn', 'config')), 

                ldap.SCOPE_SUBTREE, filt) 

        except errors.NotFound: 

            ents = [] 

        return ents 

    def find_ipa_replication_agreements(self): 

        """ 

        The replication agreements are stored in 

        cn="$SUFFIX",cn=mapping tree,cn=config 

        Return the list of hosts we have replication agreements. 

        """ 

        filt = self.get_agreement_filter(IPA_REPLICA) 

        try: 

            ents = self.conn.get_entries( 

                DN(('cn', 'mapping tree'), ('cn', 'config')), 

                ldap.SCOPE_SUBTREE, filt) 

        except errors.NotFound: 

            ents = [] 

        return ents 

    def get_replication_agreement(self, hostname): 

        """ 

        The replication agreements are stored in 

        cn="$SUFFIX",cn=mapping tree,cn=config 

        Get the replication agreement for a specific host. 

        Returns None if not found. 

        """ 

        filt = self.get_agreement_filter(host=hostname) 

        try: 

            entries = self.conn.get_entries( 

                DN(('cn', 'mapping tree'), ('cn', 'config')), 

                ldap.SCOPE_SUBTREE, filt) 

        except errors.NotFound: 

            return None 

        if len(entries) == 0: 

            return None 

        else: 

            return entries[0] # There can be only one 

    def add_replication_manager(self, conn, dn, pw): 

        """ 

        Create a pseudo user to use for replication. 

        """ 

        assert isinstance(dn, DN) 

        rdn_attr = dn[0].attr 

        rdn_val = dn[0].value 

        ent = conn.make_entry( 

            dn, 

            { 

                'objectclass': ["top", "person"], 

                rdn_attr: [rdn_val], 

                'userpassword': [pw], 

                'sn': ["replication manager pseudo user"], 

            } 

        ) 

        try: 

            conn.add_entry(ent) 

        except errors.DuplicateEntry: 

            conn.modify_s(dn, [(ldap.MOD_REPLACE, "userpassword", pw)]) 

            pass 

    def delete_replication_manager(self, conn, dn=REPL_MAN_DN): 

        assert isinstance(dn, DN) 

        try: 

            conn.delete_entry(dn) 

        except errors.NotFound: 

            pass 

    def get_replica_type(self, master=True): 

        if master: 

            return "3" 

        else: 

            return "2" 

    def replica_dn(self): 

        return DN(('cn','replica'),('cn',self.suffix),('cn','mapping tree'),('cn','config')) 

    def replica_config(self, conn, replica_id, replica_binddn): 

        assert isinstance(replica_binddn, DN) 

        dn = self.replica_dn() 

        assert isinstance(dn, DN) 

        try: 

            entry = conn.get_entry(dn) 

            managers = entry.get('nsDS5ReplicaBindDN') 

            for m in managers: 

                if replica_binddn == DN(m): 

                    return 

            # Add the new replication manager 

            mod = [(ldap.MOD_ADD, 'nsDS5ReplicaBindDN', replica_binddn)] 

            conn.modify_s(dn, mod) 

            # replication is already configured 

            return 

        except errors.NotFound: 

            pass 

        replica_type = self.get_replica_type() 

        entry = conn.make_entry( 

            dn, 

            objectclass=["top", "nsds5replica", "extensibleobject"], 

            cn=["replica"], 

            nsds5replicaroot=[str(self.suffix)], 

            nsds5replicaid=[str(replica_id)], 

            nsds5replicatype=[replica_type], 

            nsds5flags=["1"], 

            nsds5replicabinddn=[replica_binddn], 

            nsds5replicalegacyconsumer=["off"], 

        ) 

        conn.add_entry(entry) 

    def setup_changelog(self, conn): 

        ent = conn.get_entry( 

            DN( 

                ('cn', 'config'), ('cn', 'ldbm database'), 

                ('cn', 'plugins'), ('cn', 'config')), 

            ['nsslapd-directory']) 

        dbdir = os.path.dirname(ent.single_value('nsslapd-directory', None)) 

        entry = conn.make_entry( 

            DN(('cn', 'changelog5'), ('cn', 'config')), 

            { 

                'objectclass': ["top", "extensibleobject"], 

                'cn': ["changelog5"], 

                'nsslapd-changelogdir': [os.path.join(dbdir, "cldb")], 

            } 

        ) 

        try: 

            conn.add_entry(entry) 

        except errors.DuplicateEntry: 

            return 

    def setup_chaining_backend(self, conn): 

        chaindn = DN(('cn', 'chaining database'), ('cn', 'plugins'), ('cn', 'config')) 

        benamebase = "chaindb" 

        urls = [self.to_ldap_url(conn)] 

        cn = "" 

        benum = 1 

        done = False 

        while not done: 

            try: 

                cn = benamebase + str(benum) # e.g. localdb1 

                dn = DN(('cn', cn), chaindn) 

                entry = conn.make_entry( 

                    dn, 

                    { 

                        'objectclass': [ 

                            'top', 'extensibleObject', 'nsBackendInstance'], 

                        'cn': [cn], 

                        'nsslapd-suffix': [str(self.suffix)], 

                        'nsfarmserverurl': urls, 

                        'nsmultiplexorbinddn': [self.repl_man_dn], 

                        'nsmultiplexorcredentials': [self.repl_man_passwd], 

                    } 

                ) 

                self.conn.add_entry(entry) 

                done = True 

            except errors.DuplicateEntry: 

                benum += 1 

            except errors.ExecutionError, e: 

                print "Could not add backend entry " + dn, e 

                raise 

        return cn 

    def to_ldap_url(self, conn): 

        return "ldap://%s/" % ipautil.format_netloc(conn.host, conn.port) 

    def setup_chaining_farm(self, conn): 

        try: 

            conn.modify_s(self.suffix, [(ldap.MOD_ADD, 'aci', 

                                    [ "(targetattr = \"*\")(version 3.0; acl \"Proxied authorization for database links\"; allow (proxy) userdn = \"ldap:///%s\";)" % self.repl_man_dn ])]) 

        except ldap.TYPE_OR_VALUE_EXISTS: 

            root_logger.debug("proxy aci already exists in suffix %s on %s" % (self.suffix, conn.host)) 

    def get_mapping_tree_entry(self): 

        try: 

            entries = self.conn.get_entries( 

                DN(('cn', 'mapping tree'), ('cn', 'config')), 

                ldap.SCOPE_ONELEVEL, 

                "(cn=\"%s\")" % (self.suffix)) 

            # TODO: Check we got only one entry 

            return entries[0] 

        except errors.NotFound: 

            root_logger.debug( 

                "failed to find mapping tree entry for %s", self.suffix) 

            raise 

    def enable_chain_on_update(self, bename): 

        mtent = self.get_mapping_tree_entry() 

        dn = mtent.dn 

        plgent = self.conn.get_entry( 

            DN(('cn', 'Multimaster Replication Plugin'), ('cn', 'plugins'), 

               ('cn', 'config')), 

            ['nsslapd-pluginPath']) 

        path = plgent.single_value('nsslapd-pluginPath', None) 

        mod = [(ldap.MOD_REPLACE, 'nsslapd-state', 'backend'), 

               (ldap.MOD_ADD, 'nsslapd-backend', bename), 

               (ldap.MOD_ADD, 'nsslapd-distribution-plugin', path), 

               (ldap.MOD_ADD, 'nsslapd-distribution-funct', 'repl_chain_on_update')] 

        try: 

            self.conn.modify_s(dn, mod) 

        except ldap.TYPE_OR_VALUE_EXISTS: 

            root_logger.debug("chainOnUpdate already enabled for %s" % self.suffix) 

    def setup_chain_on_update(self, other_conn): 

        chainbe = self.setup_chaining_backend(other_conn) 

        self.enable_chain_on_update(chainbe) 

    def add_passsync_user(self, conn, password): 

        pass_dn = DN(('uid', 'passsync'), ('cn', 'sysaccounts'), ('cn', 'etc'), self.suffix) 

        print "The user for the Windows PassSync service is %s" % pass_dn 

        try: 

            conn.get_entry(pass_dn) 

            print "Windows PassSync entry exists, not resetting password" 

            return 

        except errors.NotFound: 

            pass 

        # The user doesn't exist, add it 

        entry = conn.make_entry( 

            pass_dn, 

            objectclass=["account", "simplesecurityobject"], 

            uid=["passsync"], 

            userPassword=[password], 

        ) 

        conn.add_entry(entry) 

        # Add it to the list of users allowed to bypass password policy 

        extop_dn = DN(('cn', 'ipa_pwd_extop'), ('cn', 'plugins'), ('cn', 'config')) 

        entry = conn.get_entry(extop_dn) 

        pass_mgrs = entry.get('passSyncManagersDNs') 

        if not pass_mgrs: 

            pass_mgrs = [] 

        if not isinstance(pass_mgrs, list): 

            pass_mgrs = [pass_mgrs] 

        pass_mgrs.append(pass_dn) 

        mod = [(ldap.MOD_REPLACE, 'passSyncManagersDNs', pass_mgrs)] 

        conn.modify_s(extop_dn, mod) 

        # And finally grant it permission to write passwords 

        mod = [(ldap.MOD_ADD, 'aci', 

            ['(targetattr = "userPassword || krbPrincipalKey || sambaLMPassword || sambaNTPassword || passwordHistory")(version 3.0; acl "Windows PassSync service can write passwords"; allow (write) userdn="ldap:///%s";)' % pass_dn])] 

        try: 

            conn.modify_s(self.suffix, mod) 

        except ldap.TYPE_OR_VALUE_EXISTS: 

            root_logger.debug("passsync aci already exists in suffix %s on %s" % (self.suffix, conn.host)) 

    def setup_winsync_agmt(self, entry, win_subtree=None): 

        if win_subtree is None: 

            win_subtree = DN(WIN_USER_CONTAINER, self.ad_suffix) 

        ds_subtree = DN(IPA_USER_CONTAINER, self.suffix) 

        windomain = ipautil.suffix_to_realm(self.suffix) 

        entry["objectclass"] = ["nsDSWindowsReplicationAgreement"] 

        entry["nsds7WindowsReplicaSubtree"] = [win_subtree] 

        entry["nsds7DirectoryReplicaSubtree"] = [ds_subtree] 

        # for now, just sync users and ignore groups 

        entry["nsds7NewWinUserSyncEnabled"] = ['true'] 

        entry["nsds7NewWinGroupSyncEnabled"] = ['false'] 

        entry["nsds7WindowsDomain"] = [windomain] 

    def agreement_dn(self, hostname, master=None): 

        """ 

        IPA agreement use the same dn on both sides, dogtag does not. 

        master is not used for IPA agreements but for dogtag it will 

        tell which side we want. 

        """ 

        cn = "meTo%s" % (hostname) 

        dn = DN(('cn', cn), self.replica_dn()) 

        return (cn, dn) 

    def setup_agreement(self, a_conn, b_hostname, port=389, 

                        repl_man_dn=None, repl_man_passwd=None, 

                        iswinsync=False, win_subtree=None, isgssapi=False, 

                        master=None): 

        """ 

        master is used to determine which side of the agreement we are 

        creating. This is only needed for dogtag replication agreements 

        which use a different name on each side. If master is None then 

        isn't a dogtag replication agreement. 

        """ 

        if repl_man_dn is not None: 

            assert isinstance(repl_man_dn, DN) 

        cn, dn = self.agreement_dn(b_hostname, master=master) 

        try: 

            a_conn.get_entry(dn) 

            return 

        except errors.NotFound: 

            pass 

        entry = a_conn.make_entry( 

            dn, 

            objectclass=["nsds5replicationagreement"], 

            cn=[cn], 

            nsds5replicahost=[b_hostname], 

            nsds5replicaport=[str(port)], 

            nsds5replicatimeout=[str(TIMEOUT)], 

            nsds5replicaroot=[str(self.suffix)], 

            description=["me to %s" % b_hostname], 

        ) 

        if master is None: 

            entry['nsDS5ReplicatedAttributeList'] = [ 

                '(objectclass=*) $ EXCLUDE %s' % " ".join(EXCLUDES)] 

        if isgssapi: 

            entry['nsds5replicatransportinfo'] = ['LDAP'] 

            entry['nsds5replicabindmethod'] = ['SASL/GSSAPI'] 

        else: 

            entry['nsds5replicabinddn'] = [repl_man_dn] 

            entry['nsds5replicacredentials'] = [repl_man_passwd] 

            entry['nsds5replicatransportinfo'] = ['TLS'] 

            entry['nsds5replicabindmethod'] = ['simple'] 

        if iswinsync: 

            self.setup_winsync_agmt(entry, win_subtree) 

        a_conn.add_entry(entry) 

        try: 

            mod = [(ldap.MOD_ADD, 'nsDS5ReplicatedAttributeListTotal', 

                   '(objectclass=*) $ EXCLUDE %s' % " ".join(TOTAL_EXCLUDES))] 

            a_conn.modify_s(dn, mod) 

        except ldap.LDAPError, e: 

            # Apparently there are problems set the total list 

            # Probably the master is an old 389-ds server, tell the caller 

            # that we will have to set the memberof fixup task 

            self.need_memberof_fixup = True 

        entry['nsds5ReplicaStripAttrs'] = [" ".join(STRIP_ATTRS)] 

        wait_for_entry(a_conn, entry) 

    def needs_memberof_fixup(self): 

        return self.need_memberof_fixup 

    def get_replica_principal_dns(self, a, b, retries): 

        """ 

        Get the DNs of the ldap principals we are going to convert 

        to using GSSAPI replication. 

        Arguments a and b are LDAP connections. retries is the number 

        of attempts that should be made to find the entries. It could 

        be that replication is slow. 

        If successful this returns a tuple (dn_a, dn_b). 

        If either of the DNs doesn't exist after the retries are 

        exhausted an exception is raised. 

        """ 

        filter_a = '(krbprincipalname=ldap/%s@%s)' % (a.host, self.realm) 

        filter_b = '(krbprincipalname=ldap/%s@%s)' % (b.host, self.realm) 

        a_entry = None 

        b_entry = None 

        error_message = '' 

        while (retries > 0 ): 

            root_logger.info('Getting ldap service principals for conversion: %s and %s' % (filter_a, filter_b)) 

            try: 

                a_entry = b.get_entries(self.suffix, ldap.SCOPE_SUBTREE, 

                                        filter=filter_a) 

            except errors.NotFound: 

                pass 

            try: 

                b_entry = a.get_entries(self.suffix, ldap.SCOPE_SUBTREE, 

                                        filter=filter_b) 

            except errors.NotFound: 

                pass 

            if a_entry and b_entry: 

                root_logger.debug('Found both principals.') 

                break 

            # One or both is missing, force sync again 

            if not a_entry: 

                root_logger.debug('Unable to find entry for %s on %s' 

                    % (filter_a, str(b))) 

                self.force_sync(a, b.host) 

                cn, dn = self.agreement_dn(b.host) 

                haserror, error_message = self.wait_for_repl_update(a, dn, 60) 

            if not b_entry: 

                root_logger.debug('Unable to find entry for %s on %s' 

                    % (filter_b, str(a))) 

                self.force_sync(b, a.host) 

                cn, dn = self.agreement_dn(a.host) 

                haserror, error_message = self.wait_for_repl_update(b, dn, 60) 

            retries -= 1 

        if not a_entry or not b_entry: 

            error = 'One of the ldap service principals is missing. ' \ 

                    'Replication agreement cannot be converted.' 

            if error_message: 

                error += '\nReplication error message: %s' % error_message 

            raise RuntimeError(error) 

        return (a_entry[0].dn, b_entry[0].dn) 

    def setup_krb_princs_as_replica_binddns(self, a, b): 

        """ 

        Search the appropriate principal names so we can get 

        the correct DNs to store in the replication agreements. 

        Then modify the replica object to allow these DNs to act 

        as replication agents. 

        """ 

        rep_dn = self.replica_dn() 

        assert isinstance(rep_dn, DN)