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f1ed123cad
freeipa/ipa-client/ipaclient/ipadiscovery.py
Martin Kosek f1ed123cad Replace DNS client based on acutil with python-dns 
IPA client and server tool set used authconfig acutil module to
for client DNS operations. This is not optimal DNS interface for
several reasons:
- does not provide native Python object oriented interface
  but but rather C-like interface based on functions and
  structures which is not easy to use and extend
- acutil is not meant to be used by third parties besides
  authconfig and thus can break without notice

Replace the acutil with python-dns package which has a feature rich
interface for dealing with all different aspects of DNS including
DNSSEC. The main target of this patch is to replace all uses of
acutil DNS library with a use python-dns. In most cases, even
though the larger parts of the code are changed, the actual
functionality is changed only in the following cases:
- redundant DNS checks were removed from verify_fqdn function
  in installutils to make the whole DNS check simpler and
  less error-prone. Logging was improves for the remaining
  checks
- improved logging for ipa-client-install DNS discovery

https://fedorahosted.org/freeipa/ticket/2730
https://fedorahosted.org/freeipa/ticket/1837
2012-05-24 13:55:56 +02:00

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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
class IPADiscovery:
def __init__(self):
self.realm = None
self.domain = None
self.server = None
self.basedn = None
def __get_resolver_domains(self):
"""
Read /etc/resolv.conf and return all the domains found in domain and
search.
Returns a list
"""
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(None)[-1]
elif line.lower().startswith('search'):
domains = domains + line.split(None)[1:]
except:
pass
if domain and not domain in domains:
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):
"""
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.
"""
server = None
root_logger.debug("Start searching for LDAP SRV record in %s and"
" its sub-domains", domain)
while not server:
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):
qname = ""
results = []
result = []
krbret = []
ldapret = []
if not server:
if not domain: #domain not provided do full DNS discovery
# get the local host name
if not hostname:
hostname = socket.getfqdn()
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,
# even if that means searching it twice. 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] + domains
for domain in domains:
(server, domain) = self.check_domain(domain)
if server:
self.server = server
self.domain = domain
break
if not self.domain: #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
else:
self.server = None
return NO_LDAP_SERVER
else: #server forced on us, this means DNS doesn't work :/
self.domain = domain
self.server = server
#search for kerberos
root_logger.debug("[ipadnssearchkrb]")
krbret = self.ipadnssearchkrb(self.domain)
if not server and not krbret[0]:
return REALM_NOT_FOUND
self.realm = krbret[0]
self.kdc = krbret[1]
root_logger.debug("[ipacheckldap]")
# 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]
elif ldapret[0] == NO_ACCESS_TO_LDAP:
ldapaccess = False
# If one of LDAP servers checked rejects access (may be 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()
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)
root_logger.debug("Generate basedn from realm: %s" % 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
"""
lret = []
lres = []
lattr = ""
linfo = ""
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.\n%s' % (thost, str(e)))
return [NOT_IPA_SERVER]
#now verify the server is really an IPA server
try:
root_logger.debug("Init ldap with: ldap://"+format_netloc(thost, 389))
lh = ldap.initialize("ldap://"+format_netloc(thost, 389))
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:
return [NOT_IPA_SERVER]
self.basedn = basedn
#search and return known realms
root_logger.debug("Search for (objectClass=krbRealmContainer) in "+self.basedn+"(sub)")
lret = lh.search_s("cn=kerberos,"+self.basedn, ldap.SCOPE_SUBTREE, "(objectClass=krbRealmContainer)")
if not lret:
#something very wrong
return [REALM_NOT_FOUND]
root_logger.debug("Found: "+str(lret))
for lres in lret:
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 string 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]
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