source4/scripting/bin/samba_dnsupdate

   1 #!/usr/bin/env python
   2 #
   3 # update our DNS names using TSIG-GSS
   4 #
   5 # Copyright (C) Andrew Tridgell 2010
   6 #
   7 # This program is free software; you can redistribute it and/or modify
   8 # it under the terms of the GNU General Public License as published by
   9 # the Free Software Foundation; either version 3 of the License, or
  10 # (at your option) any later version.
  11 #
  12 # This program is distributed in the hope that it will be useful,
  13 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 # GNU General Public License for more details.
  16 #
  17 # You should have received a copy of the GNU General Public License
  18 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19
  20
  21 import os
  22 import fcntl
  23 import sys
  24 import tempfile
  25
  26 # ensure we get messages out immediately, so they get in the samba logs,
  27 # and don't get swallowed by a timeout
  28 os.putenv('PYTHONUNBUFFERED', '1')
  29
  30 # Find right directory when running from source tree
  31 sys.path.insert(0, "bin/python")
  32
  33 import samba
  34 import optparse
  35 from samba import getopt as options
  36 from ldb import SCOPE_BASE
  37 from samba.auth import system_session
  38 from samba.samdb import SamDB
  39
  40 samba.ensure_external_module("dns", "dnspython")
  41 import dns.resolver as resolver
  42
  43 default_ttl = 900
  44
  45 parser = optparse.OptionParser("samba_dnsupdate")
  46 sambaopts = options.SambaOptions(parser)
  47 parser.add_option_group(sambaopts)
  48 parser.add_option_group(options.VersionOptions(parser))
  49 parser.add_option("--verbose", action="store_true")
  50 parser.add_option("--all-interfaces", action="store_true")
  51 parser.add_option("--use-file", type="string", help="Use a file, rather than real DNS calls")
  52
  53 creds = None
  54 ccachename = None
  55
  56 opts, args = parser.parse_args()
  57
  58 if len(args) != 0:
  59     parser.print_usage()
  60     sys.exit(1)
  61
  62 lp = sambaopts.get_loadparm()
  63
  64 domain = lp.get("realm")
  65 host = lp.get("netbios name")
  66 if opts.all_interfaces:
  67     all_interfaces = True
  68 else:
  69     all_interfaces = False
  70
  71 IPs = samba.interface_ips(lp, all_interfaces)
  72 nsupdate_cmd = lp.get('nsupdate command')
  73
  74 if len(IPs) == 0:
  75     print "No IP interfaces - skipping DNS updates"
  76     sys.exit(0)
  77
  78
  79
  80 ########################################################
  81 # get credentials if we haven't got them already
  82 def get_credentials(lp):
  83     from samba.credentials import Credentials
  84     global ccachename, creds
  85     if creds is not None:
  86         return
  87     creds = Credentials()
  88     creds.guess(lp)
  89     creds.set_machine_account(lp)
  90     (tmp_fd, ccachename) = tempfile.mkstemp()
  91     creds.get_named_ccache(lp, ccachename)
  92
  93
  94 #############################################
  95 # an object to hold a parsed DNS line
  96 class dnsobj(object):
  97     def __init__(self, string_form):
  98         list = string_form.split()
  99         self.dest = None
 100         self.port = None
 101         self.ip = None
 102         self.existing_port = None
 103         self.existing_weight = None
 104         self.type = list[0]
 105         self.name = list[1]
 106         if self.type == 'SRV':
 107             self.dest = list[2]
 108             self.port = list[3]
 109         elif self.type == 'A':
 110             self.ip   = list[2] # usually $IP, which gets replaced
 111         elif self.type == 'CNAME':
 112             self.dest = list[2]
 113         else:
 114             print "Received unexpected DNS reply of type %s" % self.type
 115             raise
 116
 117     def __str__(self):
 118         if d.type == "A":     return "%s %s %s" % (self.type, self.name, self.ip)
 119         if d.type == "SRV":   return "%s %s %s %s" % (self.type, self.name, self.dest, self.port)
 120         if d.type == "CNAME": return "%s %s %s" % (self.type, self.name, self.dest)
 121
 122
 123 ################################################
 124 # parse a DNS line from
 125 def parse_dns_line(line, sub_vars):
 126     subline = samba.substitute_var(line, sub_vars)
 127     d = dnsobj(subline)
 128     return d
 129
 130 ############################################
 131 # see if two hostnames match
 132 def hostname_match(h1, h2):
 133     h1 = str(h1)
 134     h2 = str(h2)
 135     return h1.lower().rstrip('.') == h2.lower().rstrip('.')
 136
 137
 138 ############################################
 139 # check that a DNS entry exists
 140 def check_dns_name(d):
 141     normalised_name = d.name.rstrip('.') + '.'
 142     if opts.verbose:
 143         print "Looking for DNS entry %s as %s" % (d, normalised_name)
 144
 145     if opts.use_file is not None:
 146         try:
 147             dns_file = open(opts.use_file, "r")
 148         except IOError:
 149             return False
 150
 151         for line in dns_file:
 152             line = line.strip()
 153             if line == '' or line[0] == "#":
 154                 continue
 155             if line.lower() == str(d).lower():
 156                 return True
 157         return False
 158
 159     try:
 160         ans = resolver.query(normalised_name, d.type)
 161     except resolver.NXDOMAIN:
 162         return False
 163     if d.type == 'A':
 164         # we need to be sure that our IP is there
 165         for rdata in ans:
 166             if str(rdata) == str(d.ip):
 167                 return True
 168     if d.type == 'CNAME':
 169         for i in range(len(ans)):
 170             if hostname_match(ans[i].target, d.dest):
 171                 return True
 172     if d.type == 'SRV':
 173         for rdata in ans:
 174             if opts.verbose:
 175                 print "Checking %s against %s" % (rdata, d)
 176             if hostname_match(rdata.target, d.dest):
 177                 if str(rdata.port) == str(d.port):
 178                     return True
 179                 else:
 180                     d.existing_port     = str(rdata.port)
 181                     d.existing_weight = str(rdata.weight)
 182     if opts.verbose:
 183         print "Failed to find DNS entry %s" % d
 184
 185     return False
 186
 187
 188 ###########################################
 189 # get the list of substitution vars
 190 def get_subst_vars():
 191     global lp
 192     vars = {}
 193
 194     samdb = SamDB(url=lp.get("sam database"), session_info=system_session(),
 195                   lp=lp)
 196
 197     vars['DNSDOMAIN'] = lp.get('realm').lower()
 198     vars['HOSTNAME']  = lp.get('netbios name').lower() + "." + vars['DNSDOMAIN']
 199     vars['NTDSGUID']  = samdb.get_ntds_GUID()
 200     vars['SITE']      = samdb.server_site_name()
 201     res = samdb.search(base=None, scope=SCOPE_BASE, attrs=["objectGUID"])
 202     guid = samdb.schema_format_value("objectGUID", res[0]['objectGUID'][0])
 203     vars['DOMAINGUID'] = guid
 204     return vars
 205
 206
 207 ############################################
 208 # call nsupdate for an entry
 209 def call_nsupdate(d):
 210     global ccachename, nsupdate_cmd
 211
 212     if opts.verbose:
 213         print "Calling nsupdate for %s" % d
 214
 215     if opts.use_file is not None:
 216         wfile = open(opts.use_file, 'a')
 217         fcntl.lockf(wfile, fcntl.LOCK_EX)
 218         wfile.write(str(d)+"\n")
 219         fcntl.lockf(wfile, fcntl.LOCK_UN)
 220         return
 221
 222     (tmp_fd, tmpfile) = tempfile.mkstemp()
 223     f = os.fdopen(tmp_fd, 'w')
 224     if d.type == "A":
 225         f.write("update add %s %u A %s\n" % (d.name, default_ttl, d.ip))
 226     if d.type == "SRV":
 227         if d.existing_port is not None:
 228             f.write("update delete %s SRV 0 %s %s %s\n" % (d.name, d.existing_weight,
 229                                                            d.existing_port, d.dest))
 230         f.write("update add %s %u SRV 0 100 %s %s\n" % (d.name, default_ttl, d.port, d.dest))
 231     if d.type == "CNAME":
 232         f.write("update add %s %u CNAME %s\n" % (d.name, default_ttl, d.dest))
 233     if opts.verbose:
 234         f.write("show\n")
 235     f.write("send\n")
 236     f.close()
 237
 238     os.putenv("KRB5CCNAME", ccachename)
 239     os.system("%s %s" % (nsupdate_cmd, tmpfile))
 240     os.unlink(tmpfile)
 241
 242
 243 # get the list of DNS entries we should have
 244 dns_update_list = lp.private_path('dns_update_list')
 245
 246 file = open(dns_update_list, "r")
 247
 248 # get the substitution dictionary
 249 sub_vars = get_subst_vars()
 250
 251 # build up a list of update commands to pass to nsupdate
 252 update_list = []
 253 dns_list = []
 254
 255 # read each line, and check that the DNS name exists
 256 for line in file:
 257     line = line.strip()
 258     if line == '' or line[0] == "#":
 259         continue
 260     d = parse_dns_line(line, sub_vars)
 261     dns_list.append(d)
 262
 263 # now expand the entries, if any are A record with ip set to $IP
 264 # then replace with multiple entries, one for each interface IP
 265 for d in dns_list:
 266     if d.type == 'A' and d.ip == "$IP":
 267         d.ip = IPs[0]
 268         for i in range(len(IPs)-1):
 269             d2 = d
 270             d2.ip = IPs[i+1]
 271             dns_list.append(d2)
 272
 273 # now check if the entries already exist on the DNS server
 274 for d in dns_list:
 275     if not check_dns_name(d):
 276         update_list.append(d)
 277
 278 if len(update_list) == 0:
 279     if opts.verbose:
 280         print "No DNS updates needed"
 281     sys.exit(0)
 282
 283 # get our krb5 creds
 284 get_credentials(lp)
 285
 286 # ask nsupdate to add entries as needed
 287 for d in update_list:
 288     call_nsupdate(d)
 289
 290 # delete the ccache if we created it
 291 if ccachename is not None:
 292     os.unlink(ccachename)