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 import glue
  38 from samba.auth import system_session
  39 from samba.samdb import SamDB
  40
  41 samba.ensure_external_module("dns", "dnspython")
  42 import dns.resolver as resolver
  43
  44 default_ttl = 900
  45
  46 parser = optparse.OptionParser("samba_dnsupdate")
  47 sambaopts = options.SambaOptions(parser)
  48 parser.add_option_group(sambaopts)
  49 parser.add_option_group(options.VersionOptions(parser))
  50 parser.add_option("--verbose", action="store_true")
  51 parser.add_option("--all-interfaces", action="store_true")
  52 parser.add_option("--use-file", type="string", help="Use a file, rather than real DNS calls")
  53
  54 creds = None
  55 ccachename = None
  56
  57 opts, args = parser.parse_args()
  58
  59 if len(args) != 0:
  60     parser.print_usage()
  61     sys.exit(1)
  62
  63 lp = sambaopts.get_loadparm()
  64
  65 domain = lp.get("realm")
  66 host = lp.get("netbios name")
  67 if opts.all_interfaces:
  68     all_interfaces = True
  69 else:
  70     all_interfaces = False
  71
  72 IPs = glue.interface_ips(lp, all_interfaces)
  73 nsupdate_cmd = lp.get('nsupdate command')
  74
  75 if len(IPs) == 0:
  76     print "No IP interfaces - skipping DNS updates"
  77     sys.exit(0)
  78
  79
  80
  81 ########################################################
  82 # get credentials if we haven't got them already
  83 def get_credentials(lp):
  84     from samba.credentials import Credentials
  85     global ccachename, creds
  86     if creds is not None:
  87         return
  88     creds = Credentials()
  89     creds.guess(lp)
  90     try:
  91         creds.set_machine_account(lp)
  92     except:
  93         print "Failed to set machine account"
  94         raise
  95
  96     (tmp_fd, ccachename) = tempfile.mkstemp()
  97     creds.get_named_ccache(lp, ccachename)
  98
  99
 100 #############################################
 101 # an object to hold a parsed DNS line
 102 class dnsobj(object):
 103     def __init__(self, string_form):
 104         list = string_form.split()
 105         self.dest = None
 106         self.port = None
 107         self.ip = None
 108         self.existing_port = None
 109         self.existing_weight = None
 110         self.type = list[0]
 111         self.name = list[1]
 112         if self.type == 'SRV':
 113             self.dest = list[2]
 114             self.port = list[3]
 115         elif self.type == 'A':
 116             self.ip   = list[2] # usually $IP, which gets replaced
 117         elif self.type == 'CNAME':
 118             self.dest = list[2]
 119         else:
 120             print "Received unexpected DNS reply of type %s" % self.type
 121             raise
 122
 123     def __str__(self):
 124         if d.type == "A":     return "%s %s %s" % (self.type, self.name, self.ip)
 125         if d.type == "SRV":   return "%s %s %s %s" % (self.type, self.name, self.dest, self.port)
 126         if d.type == "CNAME": return "%s %s %s" % (self.type, self.name, self.dest)
 127
 128
 129 ################################################
 130 # parse a DNS line from
 131 def parse_dns_line(line, sub_vars):
 132     subline = samba.substitute_var(line, sub_vars)
 133     d = dnsobj(subline)
 134     return d
 135
 136 ############################################
 137 # see if two hostnames match
 138 def hostname_match(h1, h2):
 139     h1 = str(h1)
 140     h2 = str(h2)
 141     return h1.lower().rstrip('.') == h2.lower().rstrip('.')
 142
 143
 144 ############################################
 145 # check that a DNS entry exists
 146 def check_dns_name(d):
 147     normalised_name = d.name.rstrip('.') + '.'
 148     if opts.verbose:
 149         print "Looking for DNS entry %s as %s" % (d, normalised_name)
 150
 151     if opts.use_file is not None:
 152         try:
 153             dns_file = open(opts.use_file, "r")
 154         except IOError:
 155             return False
 156
 157         line = dns_file.readline()
 158         while line:
 159             line = line.rstrip().lstrip()
 160             if line[0] == "#":
 161                 line = dns_file.readline()
 162                 continue
 163             if line.lower() == str(d).lower():
 164                 return True
 165             line = dns_file.readline()
 166         return False
 167
 168     try:
 169         ans = resolver.query(normalised_name, d.type)
 170     except resolver.NXDOMAIN:
 171         return False
 172     if d.type == 'A':
 173         # we need to be sure that our IP is there
 174         for rdata in ans:
 175             if str(rdata) == str(d.ip):
 176                 return True
 177     if d.type == 'CNAME':
 178         for i in range(len(ans)):
 179             if hostname_match(ans[i].target, d.dest):
 180                 return True
 181     if d.type == 'SRV':
 182         for rdata in ans:
 183             if opts.verbose:
 184                 print "Checking %s against %s" % (rdata, d)
 185             if hostname_match(rdata.target, d.dest):
 186                 if str(rdata.port) == str(d.port):
 187                     return True
 188                 else:
 189                     d.existing_port     = str(rdata.port)
 190                     d.existing_weight = str(rdata.weight)
 191     if opts.verbose:
 192         print "Failed to find DNS entry %s" % d
 193
 194     return False
 195
 196
 197 ###########################################
 198 # get the list of substitution vars
 199 def get_subst_vars():
 200     global lp
 201     vars = {}
 202
 203     samdb = SamDB(url=lp.get("sam database"), session_info=system_session(), lp=lp)
 204
 205     vars['DNSDOMAIN'] = lp.get('realm').lower()
 206     vars['HOSTNAME']  = lp.get('netbios name').lower() + "." + vars['DNSDOMAIN']
 207     vars['NTDSGUID']  = samdb.get_ntds_GUID()
 208     vars['SITE']      = samdb.server_site_name()
 209     res = samdb.search(base=None, scope=SCOPE_BASE, attrs=["objectGUID"])
 210     guid = samdb.schema_format_value("objectGUID", res[0]['objectGUID'][0])
 211     vars['DOMAINGUID'] = guid
 212     return vars
 213
 214
 215 ############################################
 216 # call nsupdate for an entry
 217 def call_nsupdate(d):
 218     global ccachename, nsupdate_cmd
 219
 220     if opts.verbose:
 221         print "Calling nsupdate for %s" % d
 222
 223     if opts.use_file is not None:
 224         wfile = open(opts.use_file, 'a')
 225         fcntl.lockf(wfile, fcntl.LOCK_EX)
 226         wfile.write(str(d)+"\n")
 227         fcntl.lockf(wfile, fcntl.LOCK_UN)
 228         return
 229
 230     (tmp_fd, tmpfile) = tempfile.mkstemp()
 231     f = os.fdopen(tmp_fd, 'w')
 232     if d.type == "A":
 233         f.write("update add %s %u A %s\n" % (d.name, default_ttl, d.ip))
 234     if d.type == "SRV":
 235         if d.existing_port is not None:
 236             f.write("update delete %s SRV 0 %s %s %s\n" % (d.name, d.existing_weight,
 237                                                            d.existing_port, d.dest))
 238         f.write("update add %s %u SRV 0 100 %s %s\n" % (d.name, default_ttl, d.port, d.dest))
 239     if d.type == "CNAME":
 240         f.write("update add %s %u CNAME %s\n" % (d.name, default_ttl, d.dest))
 241     if opts.verbose:
 242         f.write("show\n")
 243     f.write("send\n")
 244     f.close()
 245
 246     os.putenv("KRB5CCNAME", ccachename)
 247     os.system("%s %s" % (nsupdate_cmd, tmpfile))
 248     os.unlink(tmpfile)
 249
 250
 251 # get the list of DNS entries we should have
 252 dns_update_list = lp.private_path('dns_update_list')
 253
 254 file = open(dns_update_list, "r")
 255
 256 # get the substitution dictionary
 257 sub_vars = get_subst_vars()
 258
 259 # build up a list of update commands to pass to nsupdate
 260 update_list = []
 261 dns_list = []
 262
 263 # read each line, and check that the DNS name exists
 264 line = file.readline()
 265 while line:
 266     line = line.rstrip().lstrip()
 267     if line[0] == "#":
 268         line = file.readline()
 269         continue
 270     d = parse_dns_line(line, sub_vars)
 271     dns_list.append(d)
 272     line = file.readline()
 273
 274 # now expand the entries, if any are A record with ip set to $IP
 275 # then replace with multiple entries, one for each interface IP
 276 for d in dns_list:
 277     if d.type == 'A' and d.ip == "$IP":
 278         d.ip = IPs[0]
 279         for i in range(len(IPs)-1):
 280             d2 = d
 281             d2.ip = IPs[i+1]
 282             dns_list.append(d2)
 283
 284 # now check if the entries already exist on the DNS server
 285 for d in dns_list:
 286     if not check_dns_name(d):
 287         update_list.append(d)
 288
 289 if len(update_list) == 0:
 290     if opts.verbose:
 291         print "No DNS updates needed"
 292     sys.exit(0)
 293
 294 # get our krb5 creds
 295 get_credentials(lp)
 296
 297 # ask nsupdate to add entries as needed
 298 for d in update_list:
 299     call_nsupdate(d)
 300
 301 # delete the ccache if we created it
 302 if ccachename is not None:
 303     os.unlink(ccachename)
 304
 305