path: root/source4/scripting/bin/samba_dnsupdate

#!/usr/bin/env python
#
# 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

# 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')

# Find right directory when running from source tree
sys.path.insert(0, "bin/python")

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

samba.ensure_external_module("dns", "dnspython")
import dns.resolver as resolver

default_ttl = 900

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-interfaces", action="store_true")
parser.add_option("--use-file", type="string", help="Use a file, rather than real DNS calls")

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)



########################################################
# get credentials if we haven't got them already
def get_credentials(lp):
    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()
    creds.get_named_ccache(lp, ccachename)


#############################################
# an object to hold a parsed DNS line
class dnsobj(object):
    def __init__(self, string_form):
        list = string_form.split()
        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]
        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

    def __str__(self):
        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)


################################################
# parse a DNS line from
def parse_dns_line(line, sub_vars):
    subline = samba.substitute_var(line, sub_vars)
    d = dnsobj(subline)
    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):
    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

    try:
        ans = resolver.query(normalised_name, d.type)
    except resolver.NXDOMAIN:
        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':
        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 DNS entry %s" % d

    return False


###########################################
# get the list of substitution vars
def get_subst_vars():
    global lp
    vars = {}

    samdb = SamDB(url=lp.get("sam database"), session_info=system_session(),
                  lp=lp)

    vars['DNSDOMAIN'] = lp.get('realm').lower()
    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
    return vars


############################################
# call nsupdate for an entry
def call_nsupdate(d):
    global ccachename, nsupdate_cmd

    if opts.verbose:
        print "Calling nsupdate for %s" % d

    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

    (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":
        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))
        f.write("update add %s %u SRV 0 100 %s %s\n" % (d.name, default_ttl, d.port, d.dest))
    if d.type == "CNAME":
        f.write("update add %s %u CNAME %s\n" % (d.name, default_ttl, d.dest))
    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)


# get the list of DNS entries we should have
dns_update_list = lp.private_path('dns_update_list')

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
for line in file:
    line = line.strip()
    if line == '' or line[0] == "#":
        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:
    if 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
get_credentials(lp)

# ask nsupdate to add entries as needed
for d in update_list:
    call_nsupdate(d)

# delete the ccache if we created it
if ccachename is not None:
    os.unlink(ccachename)