samba-mirror/source4/scripting/bin/samba_dnsupdate

#!/usr/bin/env python
# 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
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
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:
        if i.find('%') == -1:
            # we don't want link local addresses for DNS updates
            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()
    creds.get_named_ccache(lp, ccachename)


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)