/usr/sbin/samba_dnsupdate is in samba 2:4.1.6+dfsg-1ubuntu2.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
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# vim: expandtab
#
# 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
import fcntl
import sys
import tempfile
import subprocess
# ensure we get messages out immediately, so they get in the samba logs,
# and don't get swallowed by a timeout
os.environ['PYTHONUNBUFFERED'] = '1'
# forcing GMT avoids a problem in some timezones with kerberos. Both MIT
# heimdal can get mutual authentication errors due to the 24 second difference
# between UTC and GMT when using some zone files (eg. the PDT zone from
# the US)
os.environ["TZ"] = "GMT"
# Find right directory when running from source tree
import samba
import optparse
from samba import getopt as options
from ldb import SCOPE_BASE
from samba.auth import system_session
from samba.samdb import SamDB
from samba.dcerpc import netlogon, winbind
samba.ensure_external_module("dns", "dnspython")
import dns.resolver
import dns.exception
default_ttl = 900
am_rodc = False
error_count = 0
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")
parser.add_option("--all-names", action="store_true")
parser.add_option("--all-interfaces", action="store_true")
parser.add_option("--use-file", type="string", help="Use a file, rather than real DNS calls")
parser.add_option("--update-list", type="string", help="Add DNS names from the given file")
parser.add_option("--fail-immediately", action='store_true', help="Exit on first failure")
parser.add_option("--no-credentials", dest='nocreds', action='store_true', help="don't try and get credentials")
parser.add_option("--no-substiutions", dest='nosubs', action='store_true', help="don't try and expands variables in file specified by --update-list")
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")
if opts.all_interfaces:
all_interfaces = True
else:
all_interfaces = False
IPs = samba.interface_ips(lp, all_interfaces)
nsupdate_cmd = lp.get('nsupdate command')
if len(IPs) == 0:
print "No IP interfaces - skipping DNS updates"
sys.exit(0)
IP6s = []
IP4s = []
for i in IPs:
if i.find(':') != -1:
IP6s.append(i)
else:
IP4s.append(i)
if opts.verbose:
print "IPs: %s" % IPs
def get_credentials(lp):
"""# get credentials if we haven't got them already."""
from samba import credentials
global ccachename, creds
if creds is not None:
return
creds = credentials.Credentials()
creds.guess(lp)
creds.set_machine_account(lp)
creds.set_krb_forwardable(credentials.NO_KRB_FORWARDABLE)
(tmp_fd, ccachename) = tempfile.mkstemp()
try:
creds.get_named_ccache(lp, ccachename)
except RuntimeError as e:
os.unlink(ccachename)
raise e
class dnsobj(object):
"""an object to hold a parsed DNS line"""
def __init__(self, string_form):
list = string_form.split()
if len(list) < 3:
raise Exception("Invalid DNS entry %r" % string_form)
self.dest = None
self.port = None
self.ip = None
self.existing_port = None
self.existing_weight = None
self.type = list[0]
self.name = list[1].lower()
if self.type == 'SRV':
if len(list) < 4:
raise Exception("Invalid DNS entry %r" % string_form)
self.dest = list[2].lower()
self.port = list[3]
elif self.type in ['A', 'AAAA']:
self.ip = list[2] # usually $IP, which gets replaced
elif self.type == 'CNAME':
self.dest = list[2].lower()
elif self.type == 'NS':
self.dest = list[2].lower()
else:
raise Exception("Received unexpected DNS reply of type %s" % self.type)
def __str__(self):
if d.type == "A":
return "%s %s %s" % (self.type, self.name, self.ip)
if d.type == "AAAA":
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)
if d.type == "NS":
return "%s %s %s" % (self.type, self.name, self.dest)
def parse_dns_line(line, sub_vars):
"""parse a DNS line from."""
if line.startswith("SRV _ldap._tcp.pdc._msdcs.") and not samdb.am_pdc():
if opts.verbose:
print "Skipping PDC entry (%s) as we are not a PDC" % line
return None
subline = samba.substitute_var(line, sub_vars)
return dnsobj(subline)
def hostname_match(h1, h2):
"""see if two hostnames match."""
h1 = str(h1)
h2 = str(h2)
return h1.lower().rstrip('.') == h2.lower().rstrip('.')
def check_dns_name(d):
"""check that a DNS entry exists."""
normalised_name = d.name.rstrip('.') + '.'
if opts.verbose:
print "Looking for DNS entry %s as %s" % (d, normalised_name)
if opts.use_file is not None:
try:
dns_file = open(opts.use_file, "r")
except IOError:
return False
for line in dns_file:
line = line.strip()
if line == '' or line[0] == "#":
continue
if line.lower() == str(d).lower():
return True
return False
resolver = dns.resolver.Resolver()
if d.type == "NS":
# we need to lookup the nameserver for the parent domain,
# and use that to check the NS record
parent_domain = '.'.join(normalised_name.split('.')[1:])
try:
ans = resolver.query(parent_domain, 'NS')
except dns.exception.DNSException:
if opts.verbose:
print "Failed to find parent NS for %s" % d
return False
nameservers = set()
for i in range(len(ans)):
try:
ns = resolver.query(str(ans[i]), 'A')
except dns.exception.DNSException:
continue
for j in range(len(ns)):
nameservers.add(str(ns[j]))
d.nameservers = list(nameservers)
try:
if getattr(d, 'nameservers', None):
resolver.nameservers = list(d.nameservers)
ans = resolver.query(normalised_name, d.type)
except dns.exception.DNSException:
if opts.verbose:
print "Failed to find DNS entry %s" % d
return False
if d.type in ['A', 'AAAA']:
# we need to be sure that our IP is there
for rdata in ans:
if str(rdata) == str(d.ip):
return True
elif d.type == 'CNAME':
for i in range(len(ans)):
if hostname_match(ans[i].target, d.dest):
return True
elif d.type == 'NS':
for i in range(len(ans)):
if hostname_match(ans[i].target, d.dest):
return True
elif d.type == 'SRV':
for rdata in ans:
if opts.verbose:
print "Checking %s against %s" % (rdata, d)
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)
if opts.verbose:
print "Failed to find matching DNS entry %s" % d
return False
def get_subst_vars(samdb):
"""get the list of substitution vars."""
global lp, am_rodc
vars = {}
vars['DNSDOMAIN'] = samdb.domain_dns_name()
vars['DNSFOREST'] = samdb.forest_dns_name()
vars['HOSTNAME'] = samdb.host_dns_name()
vars['NTDSGUID'] = samdb.get_ntds_GUID()
vars['SITE'] = samdb.server_site_name()
res = samdb.search(base=samdb.get_default_basedn(), scope=SCOPE_BASE, attrs=["objectGUID"])
guid = samdb.schema_format_value("objectGUID", res[0]['objectGUID'][0])
vars['DOMAINGUID'] = guid
am_rodc = samdb.am_rodc()
return vars
def call_nsupdate(d):
"""call nsupdate for an entry."""
global ccachename, nsupdate_cmd, krb5conf
if opts.verbose:
print "Calling nsupdate for %s" % d
if opts.use_file is not None:
try:
rfile = open(opts.use_file, 'r+')
except IOError:
# Perhaps create it
rfile = open(opts.use_file, 'w+')
# Open it for reading again, in case someone else got to it first
rfile = open(opts.use_file, 'r+')
fcntl.lockf(rfile, fcntl.LOCK_EX)
(file_dir, file_name) = os.path.split(opts.use_file)
(tmp_fd, tmpfile) = tempfile.mkstemp(dir=file_dir, prefix=file_name, suffix="XXXXXX")
wfile = os.fdopen(tmp_fd, 'a')
rfile.seek(0)
for line in rfile:
wfile.write(line)
wfile.write(str(d)+"\n")
os.rename(tmpfile, opts.use_file)
fcntl.lockf(rfile, fcntl.LOCK_UN)
return
normalised_name = d.name.rstrip('.') + '.'
(tmp_fd, tmpfile) = tempfile.mkstemp()
f = os.fdopen(tmp_fd, 'w')
if getattr(d, 'nameservers', None):
f.write('server %s\n' % d.nameservers[0])
if d.type == "A":
f.write("update add %s %u A %s\n" % (normalised_name, default_ttl, d.ip))
if d.type == "AAAA":
f.write("update add %s %u AAAA %s\n" % (normalised_name, default_ttl, d.ip))
if d.type == "SRV":
if d.existing_port is not None:
f.write("update delete %s SRV 0 %s %s %s\n" % (normalised_name, d.existing_weight,
d.existing_port, d.dest))
f.write("update add %s %u SRV 0 100 %s %s\n" % (normalised_name, default_ttl, d.port, d.dest))
if d.type == "CNAME":
f.write("update add %s %u CNAME %s\n" % (normalised_name, default_ttl, d.dest))
if d.type == "NS":
f.write("update add %s %u NS %s\n" % (normalised_name, default_ttl, d.dest))
if opts.verbose:
f.write("show\n")
f.write("send\n")
f.close()
global error_count
if ccachename:
os.environ["KRB5CCNAME"] = ccachename
try:
cmd = nsupdate_cmd[:]
cmd.append(tmpfile)
env = {}
if krb5conf:
env["KRB5_CONFIG"] = krb5conf
if ccachename:
env["KRB5CCNAME"] = ccachename
ret = subprocess.call(cmd, shell=False, env=env)
if ret != 0:
if opts.fail_immediately:
if opts.verbose:
print("Failed update with %s" % tmpfile)
sys.exit(1)
error_count = error_count + 1
if opts.verbose:
print("Failed nsupdate: %d" % ret)
except Exception, estr:
if opts.fail_immediately:
sys.exit(1)
error_count = error_count + 1
if opts.verbose:
print("Failed nsupdate: %s : %s" % (str(d), estr))
os.unlink(tmpfile)
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
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
}
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
name.dns_domain_info_type = typemap[t]
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')
global error_count
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))
error_count = error_count + 1
except RuntimeError, reason:
print("Error setting DNS entry of type %u: %s: %s" % (t, d, reason))
error_count = error_count + 1
if error_count != 0 and opts.fail_immediately:
sys.exit(1)
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 = {
netlogon.NlDnsLdapAtSite : '_ldap._tcp.${SITE}._sites.${DNSDOMAIN}',
netlogon.NlDnsGcAtSite : '_ldap._tcp.${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)
# get the list of DNS entries we should have
if opts.update_list:
dns_update_list = opts.update_list
else:
dns_update_list = lp.private_path('dns_update_list')
# 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.environ['KRB5_CONFIG'] = krb5conf
file = open(dns_update_list, "r")
if opts.nosubs:
sub_vars = {}
else:
samdb = SamDB(url=lp.samdb_url(), session_info=system_session(), lp=lp)
# get the substitution dictionary
sub_vars = get_subst_vars(samdb)
# build up a list of update commands to pass to nsupdate
update_list = []
dns_list = []
dup_set = set()
# read each line, and check that the DNS name exists
for line in file:
line = line.strip()
if line == '' or line[0] == "#":
continue
d = parse_dns_line(line, sub_vars)
if d is None:
continue
if d.type == 'A' and len(IP4s) == 0:
continue
if d.type == 'AAAA' and len(IP6s) == 0:
continue
if str(d) not in dup_set:
dns_list.append(d)
dup_set.add(str(d))
# now expand the entries, if any are A record with ip set to $IP
# then replace with multiple entries, one for each interface IP
for d in dns_list:
if d.ip != "$IP":
continue
if d.type == 'A':
d.ip = IP4s[0]
for i in range(len(IP4s)-1):
d2 = dnsobj(str(d))
d2.ip = IP4s[i+1]
dns_list.append(d2)
if d.type == 'AAAA':
d.ip = IP6s[0]
for i in range(len(IP6s)-1):
d2 = dnsobj(str(d))
d2.ip = IP6s[i+1]
dns_list.append(d2)
# now check if the entries already exist on the DNS server
for d in dns_list:
if opts.all_names or not check_dns_name(d):
update_list.append(d)
if len(update_list) == 0:
if opts.verbose:
print "No DNS updates needed"
sys.exit(0)
# get our krb5 creds
if not opts.nocreds:
get_credentials(lp)
# ask nsupdate to add entries as needed
for d in update_list:
if am_rodc:
if d.name.lower() == domain.lower():
continue
if not d.type in [ 'A', 'AAAA' ]:
call_rodc_update(d)
else:
call_nsupdate(d)
else:
call_nsupdate(d)
# delete the ccache if we created it
if ccachename is not None:
os.unlink(ccachename)
if error_count != 0:
print("Failed update of %u entries" % error_count)
sys.exit(error_count)
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