freeipa/ipa-client/ipaclient/ipadiscovery.py

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# Authors: Simo Sorce <ssorce@redhat.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 socket
import os
from ipapython.ipa_log_manager import *
import tempfile
import ldap
from ldap import LDAPError
from dns import resolver, rdatatype
from dns.exception import DNSException
from ipapython.ipautil import run, CalledProcessError, valid_ip, get_ipa_basedn, \
realm_to_suffix, format_netloc
NOT_FQDN = -1
NO_LDAP_SERVER = -2
REALM_NOT_FOUND = -3
NOT_IPA_SERVER = -4
NO_ACCESS_TO_LDAP = -5
BAD_HOST_CONFIG = -10
UNKNOWN_ERROR = -15
error_names = {
0: 'Success',
NOT_FQDN: 'NOT_FQDN',
NO_LDAP_SERVER: 'NO_LDAP_SERVER',
REALM_NOT_FOUND: 'REALM_NOT_FOUND',
NOT_IPA_SERVER: 'NOT_IPA_SERVER',
NO_ACCESS_TO_LDAP: 'NO_ACCESS_TO_LDAP',
BAD_HOST_CONFIG: 'BAD_HOST_CONFIG',
UNKNOWN_ERROR: 'UNKNOWN_ERROR',
}
class IPADiscovery(object):
def __init__(self):
self.realm = None
self.domain = None
self.server = None
self.basedn = None
self.realm_source = None
self.domain_source = None
self.server_source = None
self.basedn_source = None
def __get_resolver_domains(self):
"""
Read /etc/resolv.conf and return all the domains found in domain and
search.
Returns a list of (domain, info) pairs. The info contains a reason why
the domain is returned.
"""
domains = []
domain = None
try:
fp = open('/etc/resolv.conf', 'r')
lines = fp.readlines()
fp.close()
for line in lines:
if line.lower().startswith('domain'):
domain = (line.split()[-1],
'local domain from /etc/resolv.conf')
elif line.lower().startswith('search'):
domains += [(d, 'search domain from /etc/resolv.conf') for
d in line.split()[1:]]
except:
pass
if domain:
domains = [domain] + domains
return domains
def getServerName(self):
return self.server
def getDomainName(self):
return self.domain
def getRealmName(self):
return self.realm
def getKDCName(self):
return self.kdc
def getBaseDN(self):
return self.basedn
def check_domain(self, domain, tried, reason):
"""
Given a domain search it for SRV records, breaking it down to search
all subdomains too.
Returns a tuple (server, domain) or (None,None) if a SRV record
isn't found.
:param tried: A set of domains that were tried already
:param reason: Reason this domain is searched (included in the log)
"""
server = None
root_logger.debug('Start searching for LDAP SRV record in "%s" (%s) ' +
'and its sub-domains', domain, reason)
while not server:
if domain in tried:
root_logger.debug("Already searched %s; skipping", domain)
break
tried.add(domain)
server = self.ipadns_search_srv(domain, '_ldap._tcp', 389)
if server:
return (server[0], domain)
else:
p = domain.find(".")
if p == -1: #no ldap server found and last component of the domain already tested
return (None, None)
domain = domain[p+1:]
return (None, None)
def search(self, domain = "", server = "", hostname=None):
root_logger.debug("[IPA Discovery]")
root_logger.debug(
'Starting IPA discovery with domain=%s, server=%s, hostname=%s',
domain, server, hostname)
if type(server) in (list, tuple):
server = server[0]
if not server:
if not domain: #domain not provided do full DNS discovery
# get the local host name
if not hostname:
hostname = socket.getfqdn()
root_logger.debug('Hostname: %s', hostname)
if not hostname:
return BAD_HOST_CONFIG
if valid_ip(hostname):
return NOT_FQDN
# first, check for an LDAP server for the local domain
p = hostname.find(".")
if p == -1: #no domain name
return NOT_FQDN
domain = hostname[p+1:]
# Get the list of domains from /etc/resolv.conf, we'll search
# them all. We search the domain of our hostname first though.
# This is to avoid the situation where domain isn't set in
# /etc/resolv.conf and the search list has the hostname domain
# not first. We could end up with the wrong SRV record.
domains = self.__get_resolver_domains()
domains = [(domain, 'domain of the hostname')] + domains
tried = set()
for domain, reason in domains:
server, domain = self.check_domain(domain, tried, reason)
if server:
self.server = server
self.domain = domain
self.server_source = self.domain_source = (
'Discovered LDAP SRV records from %s (%s)' %
(domain, reason))
break
if not self.domain: #no ldap server found
root_logger.debug('No LDAP server found')
return NO_LDAP_SERVER
else:
root_logger.debug("Search for LDAP SRV record in %s", domain)
server = self.ipadns_search_srv(domain, '_ldap._tcp', 389)
if server:
self.server = server[0]
self.domain = domain
self.server_source = self.domain_source = (
'Discovered LDAP SRV records from %s' % domain)
else:
self.server = None
root_logger.debug('No LDAP server found')
return NO_LDAP_SERVER
else:
root_logger.debug("Server and domain forced")
self.domain = domain
self.server = server
self.domain_source = self.server_source = 'Forced'
#search for kerberos
root_logger.debug("[Kerberos realm search]")
krb_realm, kdc = self.ipadnssearchkrb(self.domain)
if not server and not krb_realm:
return REALM_NOT_FOUND
self.realm = krb_realm
self.kdc = kdc
self.realm_source = self.kdc_source = (
'Discovered Kerberos DNS records from %s' % self.domain)
root_logger.debug("[LDAP server check]")
root_logger.debug('Verifying that %s (realm %s) is an IPA server',
self.server, self.realm)
# We may have received multiple servers corresponding to the domain
# Iterate through all of those to check if it is IPA LDAP server
ldapret = [NOT_IPA_SERVER]
ldapaccess = True
if self.server:
# check ldap now
ldapret = self.ipacheckldap(self.server, self.realm)
if ldapret[0] == 0:
self.server = ldapret[1]
self.realm = ldapret[2]
self.server_source = self.realm_source = (
'Discovered from LDAP DNS records in %s' % self.server)
elif ldapret[0] == NO_ACCESS_TO_LDAP:
ldapaccess = False
# If one of LDAP servers checked rejects access (maybe anonymous
# bind is disabled), assume realm and basedn generated off domain.
# Note that in case ldapret[0] == 0 and ldapaccess == False (one of
# servers didn't provide access but another one succeeded), self.realm
# will be set already to a proper value above, self.basdn will be
# initialized during the LDAP check itself and we'll skip these two checks.
if not ldapaccess and self.realm is None:
# Assume realm is the same as domain.upper()
self.realm = self.domain.upper()
self.realm_source = 'Assumed same as domain'
root_logger.debug(
"Assuming realm is the same as domain: %s", self.realm)
if not ldapaccess and self.basedn is None:
# Generate suffix from realm
self.basedn = realm_to_suffix(self.realm)
self.basedn_source = 'Generated from Kerberos realm'
root_logger.debug("Generated basedn from realm: %s" % self.basedn)
root_logger.debug(
"Discovery result: %s; server=%s, domain=%s, kdc=%s, basedn=%s",
error_names.get(ldapret[0], ldapret[0]),
self.server, self.domain, self.kdc, self.basedn)
return ldapret[0]
def ipacheckldap(self, thost, trealm):
"""
Given a host and kerberos realm verify that it is an IPA LDAP
server hosting the realm. The connection is an SSL connection
so the remote IPA CA cert must be available at
http://HOST/ipa/config/ca.crt
Returns a list [errno, host, realm] or an empty list on error.
Errno is an error number:
0 means all ok
1 means we could not check the info in LDAP (may happend when
anonymous binds are disabled)
2 means the server is certainly not an IPA server
"""
lrealms = []
i = 0
# Get the CA certificate
try:
# Create TempDir
temp_ca_dir = tempfile.mkdtemp()
except OSError, e:
raise RuntimeError("Creating temporary directory failed: %s" % str(e))
try:
run(["/usr/bin/wget", "-O", "%s/ca.crt" % temp_ca_dir, "-T", "15", "-t", "2",
"http://%s/ipa/config/ca.crt" % format_netloc(thost)])
except CalledProcessError, e:
root_logger.debug('Retrieving CA from %s failed: %s', thost, str(e))
return [NOT_IPA_SERVER]
#now verify the server is really an IPA server
try:
ldap_url = "ldap://" + format_netloc(thost, 389)
root_logger.debug("Init LDAP connection with: %s", ldap_url)
lh = ldap.initialize(ldap_url)
ldap.set_option(ldap.OPT_X_TLS_REQUIRE_CERT, True)
ldap.set_option(ldap.OPT_X_TLS_CACERTFILE, "%s/ca.crt" % temp_ca_dir)
lh.set_option(ldap.OPT_PROTOCOL_VERSION, 3)
lh.set_option(ldap.OPT_X_TLS_DEMAND, True)
lh.start_tls_s()
lh.simple_bind_s("","")
# get IPA base DN
root_logger.debug("Search LDAP server for IPA base DN")
basedn = get_ipa_basedn(lh)
if basedn is None:
root_logger.debug("The server is not an IPA server")
return [NOT_IPA_SERVER]
self.basedn = basedn
self.basedn_source = 'From IPA server %s' % ldap_url
#search and return known realms
root_logger.debug(
"Search for (objectClass=krbRealmContainer) in %s (sub)",
self.basedn)
lret = lh.search_s("cn=kerberos,"+self.basedn, ldap.SCOPE_SUBTREE, "(objectClass=krbRealmContainer)")
if not lret:
#something very wrong
return [REALM_NOT_FOUND]
for lres in lret:
root_logger.debug("Found: %s", lres[0])
for lattr in lres[1]:
if lattr.lower() == "cn":
lrealms.append(lres[1][lattr][0])
if trealm:
for r in lrealms:
if trealm == r:
return [0, thost, trealm]
# must match or something is very wrong
return [REALM_NOT_FOUND]
else:
if len(lrealms) != 1:
#which one? we can't attach to a multi-realm server without DNS working
return [REALM_NOT_FOUND]
else:
return [0, thost, lrealms[0]]
#we shouldn't get here
return [UNKNOWN_ERROR]
except LDAPError, err:
if isinstance(err, ldap.TIMEOUT):
root_logger.error("LDAP Error: timeout")
return [NO_LDAP_SERVER]
if isinstance(err, ldap.INAPPROPRIATE_AUTH):
root_logger.debug("LDAP Error: Anonymous acces not allowed")
return [NO_ACCESS_TO_LDAP]
root_logger.error("LDAP Error: %s: %s" %
(err.args[0]['desc'], err.args[0].get('info', '')))
return [UNKNOWN_ERROR]
finally:
os.remove("%s/ca.crt" % temp_ca_dir)
os.rmdir(temp_ca_dir)
def ipadns_search_srv(self, domain, srv_record_name, default_port,
break_on_first=True):
"""
Search for SRV records in given domain. When no record is found,
en empty list is returned
:param domain: Search domain name
:param srv_record_name: SRV record name, e.g. "_ldap._tcp"
:param default_port: When default_port is not None, it is being
checked with the port in SRV record and if they don't
match, the port from SRV record is appended to
found hostname in this format: "hostname:port"
:param break_on_first: break on the first find and return just one
entry
"""
servers = []
qname = '%s.%s' % (srv_record_name, domain)
root_logger.debug("Search DNS for SRV record of %s", qname)
try:
answers = resolver.query(qname, rdatatype.SRV)
except DNSException, e:
root_logger.debug("DNS record not found: %s", e.__class__.__name__)
answers = []
for answer in answers:
root_logger.debug("DNS record found: %s", answer)
server = str(answer.target).rstrip(".")
if not server:
root_logger.debug("Cannot parse the hostname from SRV record: %s", answer)
continue
if default_port is not None and answer.port != default_port:
server = "%s:%s" % (server, str(answer.port))
servers.append(server)
if break_on_first:
break
return servers
def ipadnssearchkrb(self, tdomain):
realm = None
kdc = None
# now, check for a Kerberos realm the local host or domain is in
qname = "_kerberos." + tdomain
root_logger.debug("Search DNS for TXT record of %s", qname)
try:
answers = resolver.query(qname, rdatatype.TXT)
except DNSException, e:
root_logger.debug("DNS record not found: %s", e.__class__.__name__)
answers = []
for answer in answers:
root_logger.debug("DNS record found: %s", answer)
if answer.strings:
realm = answer.strings[0]
if realm:
break
if realm:
# now fetch server information for the realm
domain = realm.lower()
kdc = self.ipadns_search_srv(domain, '_kerberos._udp', 88,
break_on_first=False)
if not kdc:
root_logger.debug("SRV record for KDC not found! Realm: %s, SRV record: %s" % (realm, qname))
kdc = None
kdc = ','.join(kdc)
return realm, kdc