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#!/usr/bin/env python
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#
# update our DNS names using TSIG-GSS
#
# Copyright (C) Andrew Tridgell 2010
#
# 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 os
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import fcntl
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import sys
import tempfile
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# ensure we get messages out immediately, so they get in the samba logs,
# and don't get swallowed by a timeout
os.putenv('PYTHONUNBUFFERED', '1')
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# Find right directory when running from source tree
sys.path.insert(0, "bin/python")
import samba
import optparse
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from samba import getopt as options
from ldb import SCOPE_BASE
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from samba.auth import system_session
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from samba.samdb import SamDB
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from samba.dcerpc import netlogon, winbind
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samba.ensure_external_module("dns", "dnspython")
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import dns.resolver as resolver
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default_ttl = 900
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am_rodc = False
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parser = optparse.OptionParser("samba_dnsupdate")
sambaopts = options.SambaOptions(parser)
parser.add_option_group(sambaopts)
parser.add_option_group(options.VersionOptions(parser))
parser.add_option("--verbose", action="store_true")
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parser.add_option("--all-names", action="store_true")
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parser.add_option("--all-interfaces", action="store_true")
parser.add_option("--use-file", type="string", help="Use a file, rather than real DNS calls")
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creds = None
ccachename = None
opts, args = parser.parse_args()
if len(args) != 0:
parser.print_usage()
sys.exit(1)
lp = sambaopts.get_loadparm()
domain = lp.get("realm")
host = lp.get("netbios name")
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if opts.all_interfaces:
all_interfaces = True
else:
all_interfaces = False
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IPs = samba.interface_ips(lp, all_interfaces)
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nsupdate_cmd = lp.get('nsupdate command')
if len(IPs) == 0:
print "No IP interfaces - skipping DNS updates"
sys.exit(0)
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if opts.verbose:
print "IPs: %s" % IPs
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########################################################
# get credentials if we haven't got them already
def get_credentials(lp):
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from samba import credentials
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global ccachename, creds
if creds is not None:
return
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creds = credentials.Credentials()
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creds.guess(lp)
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creds.set_machine_account(lp)
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creds.set_krb_forwardable(credentials.NO_KRB_FORWARDABLE)
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(tmp_fd, ccachename) = tempfile.mkstemp()
creds.get_named_ccache(lp, ccachename)
#############################################
# an object to hold a parsed DNS line
class dnsobj(object):
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def __init__(self, string_form):
list = string_form.split()
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self.dest = None
self.port = None
self.ip = None
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self.existing_port = None
self.existing_weight = None
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self.type = list[0]
self.name = list[1]
if self.type == 'SRV':
self.dest = list[2]
self.port = list[3]
elif self.type == 'A':
self.ip = list[2] # usually $IP, which gets replaced
elif self.type == 'CNAME':
self.dest = list[2]
else:
print "Received unexpected DNS reply of type %s" % self.type
raise
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def __str__(self):
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if d.type == "A": return "%s %s %s" % (self.type, self.name, self.ip)
if d.type == "SRV": return "%s %s %s %s" % (self.type, self.name, self.dest, self.port)
if d.type == "CNAME": return "%s %s %s" % (self.type, self.name, self.dest)
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################################################
# parse a DNS line from
def parse_dns_line(line, sub_vars):
subline = samba.substitute_var(line, sub_vars)
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d = dnsobj(subline)
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return d
############################################
# see if two hostnames match
def hostname_match(h1, h2):
h1 = str(h1)
h2 = str(h2)
return h1.lower().rstrip('.') == h2.lower().rstrip('.')
############################################
# check that a DNS entry exists
def check_dns_name(d):
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normalised_name = d.name.rstrip('.') + '.'
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if opts.verbose:
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print "Looking for DNS entry %s as %s" % (d, normalised_name)
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if opts.use_file is not None:
try:
dns_file = open(opts.use_file, "r")
except IOError:
return False
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for line in dns_file:
line = line.strip()
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if line == '' or line[0] == "#":
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continue
if line.lower() == str(d).lower():
return True
return False
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try:
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ans = resolver.query(normalised_name, d.type)
except resolver.NXDOMAIN:
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return False
if d.type == 'A':
# we need to be sure that our IP is there
for rdata in ans:
if str(rdata) == str(d.ip):
return True
if d.type == 'CNAME':
for i in range(len(ans)):
if hostname_match(ans[i].target, d.dest):
return True
if d.type == 'SRV':
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for rdata in ans:
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if opts.verbose:
print "Checking %s against %s" % (rdata, d)
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if hostname_match(rdata.target, d.dest):
if str(rdata.port) == str(d.port):
return True
else:
d.existing_port = str(rdata.port)
d.existing_weight = str(rdata.weight)
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if opts.verbose:
print "Failed to find DNS entry %s" % d
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return False
###########################################
# get the list of substitution vars
def get_subst_vars():
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global lp, am_rodc
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vars = {}
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samdb = SamDB(url=lp.get("sam database"), session_info=system_session(),
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lp=lp)
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vars['DNSDOMAIN'] = lp.get('realm').lower()
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vars['DNSFOREST'] = lp.get('realm').lower()
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vars['HOSTNAME'] = lp.get('netbios name').lower() + "." + vars['DNSDOMAIN']
vars['NTDSGUID'] = samdb.get_ntds_GUID()
vars['SITE'] = samdb.server_site_name()
res = samdb.search(base=None, scope=SCOPE_BASE, attrs=["objectGUID"])
guid = samdb.schema_format_value("objectGUID", res[0]['objectGUID'][0])
vars['DOMAINGUID'] = guid
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am_rodc = samdb.am_rodc()
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return vars
############################################
# call nsupdate for an entry
def call_nsupdate(d):
global ccachename, nsupdate_cmd
if opts.verbose:
print "Calling nsupdate for %s" % d
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if opts.use_file is not None:
wfile = open(opts.use_file, 'a')
fcntl.lockf(wfile, fcntl.LOCK_EX)
wfile.write(str(d)+"\n")
fcntl.lockf(wfile, fcntl.LOCK_UN)
return
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(tmp_fd, tmpfile) = tempfile.mkstemp()
f = os.fdopen(tmp_fd, 'w')
if d.type == "A":
f.write("update add %s %u A %s\n" % (d.name, default_ttl, d.ip))
if d.type == "SRV":
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if d.existing_port is not None:
f.write("update delete %s SRV 0 %s %s %s\n" % (d.name, d.existing_weight,
d.existing_port, d.dest))
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f.write("update add %s %u SRV 0 100 %s %s\n" % (d.name, default_ttl, d.port, d.dest))
if d.type == "CNAME":
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f.write("update add %s %u CNAME %s\n" % (d.name, default_ttl, d.dest))
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if opts.verbose:
f.write("show\n")
f.write("send\n")
f.close()
os.putenv("KRB5CCNAME", ccachename)
os.system("%s %s" % (nsupdate_cmd, tmpfile))
os.unlink(tmpfile)
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def rodc_dns_update(d, t):
'''a single DNS update via the RODC netlogon call'''
global sub_vars
if opts.verbose:
print "Calling netlogon RODC update for %s" % d
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typemap = {
netlogon.NlDnsLdapAtSite : netlogon.NlDnsInfoTypeNone,
netlogon.NlDnsGcAtSite : netlogon.NlDnsDomainNameAlias,
netlogon.NlDnsDsaCname : netlogon.NlDnsDomainNameAlias,
netlogon.NlDnsKdcAtSite : netlogon.NlDnsInfoTypeNone,
netlogon.NlDnsDcAtSite : netlogon.NlDnsInfoTypeNone,
netlogon.NlDnsRfc1510KdcAtSite : netlogon.NlDnsInfoTypeNone,
netlogon.NlDnsGenericGcAtSite : netlogon.NlDnsDomainNameAlias
}
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w = winbind.winbind("irpc:winbind_server", lp)
dns_names = netlogon.NL_DNS_NAME_INFO_ARRAY()
dns_names.count = 1
name = netlogon.NL_DNS_NAME_INFO()
name.type = t
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name.dns_domain_info_type = typemap[t]
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name.priority = 0
name.weight = 0
if d.port is not None:
name.port = int(d.port)
name.dns_register = True
dns_names.names = [ name ]
site_name = sub_vars['SITE'].decode('utf-8')
try:
ret_names = w.DsrUpdateReadOnlyServerDnsRecords(site_name, default_ttl, dns_names)
if ret_names.names[0].status != 0:
print("Failed to set DNS entry: %s (status %u)" % (d, ret_names.names[0].status))
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except RuntimeError, reason:
print("Error setting DNS entry of type %u: %s: %s" % (t, d, reason))
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def call_rodc_update(d):
'''RODCs need to use the netlogon API for nsupdate'''
global lp, sub_vars
# we expect failure for 3268 if we aren't a GC
if d.port is not None and int(d.port) == 3268:
return
# map the DNS request to a netlogon update type
map = {
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netlogon.NlDnsLdapAtSite : '_ldap._tcp.${SITE}._sites.${DNSDOMAIN}',
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netlogon.NlDnsGcAtSite : '_ldap._tcp.${SITE}._sites.gc._msdcs.${DNSDOMAIN}',
netlogon.NlDnsDsaCname : '${NTDSGUID}._msdcs.${DNSFOREST}',
netlogon.NlDnsKdcAtSite : '_kerberos._tcp.${SITE}._sites.dc._msdcs.${DNSDOMAIN}',
netlogon.NlDnsDcAtSite : '_ldap._tcp.${SITE}._sites.dc._msdcs.${DNSDOMAIN}',
netlogon.NlDnsRfc1510KdcAtSite : '_kerberos._tcp.${SITE}._sites.${DNSDOMAIN}',
netlogon.NlDnsGenericGcAtSite : '_gc._tcp.${SITE}._sites.${DNSFOREST}'
}
for t in map:
subname = samba.substitute_var(map[t], sub_vars)
if subname.lower() == d.name.lower():
# found a match - do the update
rodc_dns_update(d, t)
return
if opts.verbose:
print("Unable to map to netlogon DNS update: %s" % d)
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# get the list of DNS entries we should have
dns_update_list = lp.private_path('dns_update_list')
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# use our private krb5.conf to avoid problems with the wrong domain
# bind9 nsupdate wants the default domain set
krb5conf = lp.private_path('krb5.conf')
os.putenv('KRB5_CONFIG', krb5conf)
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file = open(dns_update_list, "r")
# get the substitution dictionary
sub_vars = get_subst_vars()
# build up a list of update commands to pass to nsupdate
update_list = []
dns_list = []
# read each line, and check that the DNS name exists
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for line in file:
line = line.strip()
if line == '' or line[0] == "#":
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continue
d = parse_dns_line(line, sub_vars)
dns_list.append(d)
# now expand the entries, if any are A record with ip set to $IP
# then replace with multiple entries, one for each interface IP
for d in dns_list:
if d.type == 'A' and d.ip == "$IP":
d.ip = IPs[0]
for i in range(len(IPs)-1):
d2 = d
d2.ip = IPs[i+1]
dns_list.append(d2)
# now check if the entries already exist on the DNS server
for d in dns_list:
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if opts.all_names or not check_dns_name(d):
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update_list.append(d)
if len(update_list) == 0:
if opts.verbose:
print "No DNS updates needed"
sys.exit(0)
# get our krb5 creds
get_credentials(lp)
# ask nsupdate to add entries as needed
for d in update_list:
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if am_rodc:
call_rodc_update(d)
else:
call_nsupdate(d)
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# delete the ccache if we created it
if ccachename is not None:
os.unlink(ccachename)