source4/scripting/bin/samba_dnsupdate

   1 #!/usr/bin/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 getopt
  22 import os
  23 import fcntl
  24 import sys
  25 import tempfile
  26
  27 # ensure we get messages out immediately, so they get in the samba logs,
  28 # and don't get swallowed by a timeout
  29 os.putenv('PYTHONUNBUFFERED', '1')
  30
  31 # Find right directory when running from source tree
  32 sys.path.insert(0, "bin/python")
  33
  34 import samba
  35 import optparse
  36 from samba import getopt as options, Ldb
  37 from ldb import SCOPE_SUBTREE, SCOPE_BASE, LdbError
  38 import ldb
  39 from samba import glue
  40 from samba.auth import system_session
  41 from samba.samdb import SamDB
  42 import samba.external
  43
  44 resolver = samba.external.samba_external_dns_resolver()
  45
  46 default_ttl = 900
  47
  48 parser = optparse.OptionParser("samba_dnsupdate")
  49 sambaopts = options.SambaOptions(parser)
  50 parser.add_option_group(sambaopts)
  51 parser.add_option_group(options.VersionOptions(parser))
  52 parser.add_option("--verbose", action="store_true")
  53 parser.add_option("--all-interfaces", action="store_true")
  54 parser.add_option("--use-file", type="string", help="Use a file, rather than real DNS calls")
  55
  56 creds = None
  57 ccachename = None
  58
  59 opts, args = parser.parse_args()
  60
  61 if len(args) != 0:
  62     parser.print_usage()
  63     sys.exit(1)
  64
  65 lp = sambaopts.get_loadparm()
  66
  67 domain = lp.get("realm")
  68 host = lp.get("netbios name")
  69 if opts.all_interfaces:
  70     all_interfaces = True
  71 else:
  72     all_interfaces = False
  73
  74 IPs = glue.interface_ips(lp, all_interfaces)
  75 nsupdate_cmd = lp.get('nsupdate command')
  76
  77 if len(IPs) == 0:
  78     print "No IP interfaces - skipping DNS updates"
  79     sys.exit(0)
  80
  81
  82
  83 ########################################################
  84 # get credentials if we haven't got them already
  85 def get_credentials(lp):
  86     from samba.credentials import Credentials
  87     global ccachename, creds
  88     if creds is not None:
  89         return
  90     creds = Credentials()
  91     creds.guess(lp)
  92     try:
  93         creds.set_machine_account(lp)
  94     except:
  95         print "Failed to set machine account"
  96         raise
  97
  98     (tmp_fd, ccachename) = tempfile.mkstemp()
  99     creds.get_named_ccache(lp, ccachename)
 100
 101
 102 #############################################
 103 # an object to hold a parsed DNS line
 104 class dnsobj(object):
 105     def __init__(self, string_form):
 106         list = string_form.split()
 107         self.dest = None
 108         self.port = None
 109         self.ip = None
 110         self.existing_port = None
 111         self.existing_weight = None
 112         self.type = list[0]
 113         self.name = list[1]
 114         if self.type == 'SRV':
 115             self.dest = list[2]
 116             self.port = list[3]
 117         elif self.type == 'A':
 118             self.ip   = list[2] # usually $IP, which gets replaced
 119         elif self.type == 'CNAME':
 120             self.dest = list[2]
 121         else:
 122             print "Received unexpected DNS reply of type %s" % self.type
 123             raise
 124
 125     def __str__(self):
 126         if d.type == "A":     return "%s %s %s" % (self.type, self.name, self.ip)
 127         if d.type == "SRV":   return "%s %s %s %s" % (self.type, self.name, self.dest, self.port)
 128         if d.type == "CNAME": return "%s %s %s" % (self.type, self.name, self.dest)
 129
 130
 131 ################################################
 132 # parse a DNS line from
 133 def parse_dns_line(line, sub_vars):
 134     subline = samba.substitute_var(line, sub_vars)
 135     d = dnsobj(subline)
 136     return d
 137
 138 ############################################
 139 # see if two hostnames match
 140 def hostname_match(h1, h2):
 141     h1 = str(h1)
 142     h2 = str(h2)
 143     return h1.lower().rstrip('.') == h2.lower().rstrip('.')
 144
 145
 146 ############################################
 147 # check that a DNS entry exists
 148 def check_dns_name(d):
 149     normalised_name = d.name.rstrip('.') + '.'
 150     if opts.verbose:
 151         print "Looking for DNS entry %s as %s" % (d, normalised_name)
 152
 153     if opts.use_file is not None:
 154         try:
 155             dns_file = open(opts.use_file, "r")
 156         except IOError:
 157             return False
 158
 159         line = dns_file.readline()
 160         while line:
 161             line = line.rstrip().lstrip()
 162             if line[0] == "#":
 163                 line = dns_file.readline()
 164                 continue
 165             if line.lower() == str(d).lower():
 166                 return True
 167             line = dns_file.readline()
 168         return False
 169
 170     try:
 171         ans = resolver.query(normalised_name, d.type)
 172     except resolver.NXDOMAIN:
 173         return False
 174     if d.type == 'A':
 175         # we need to be sure that our IP is there
 176         for rdata in ans:
 177             if str(rdata) == str(d.ip):
 178                 return True
 179     if d.type == 'CNAME':
 180         for i in range(len(ans)):
 181             if hostname_match(ans[i].target, d.dest):
 182                 return True
 183     if d.type == 'SRV':
 184         for rdata in ans:
 185             if opts.verbose:
 186                 print "Checking %s against %s" % (rdata, d)
 187             if hostname_match(rdata.target, d.dest):
 188                 if str(rdata.port) == str(d.port):
 189                     return True
 190                 else:
 191                     d.existing_port     = str(rdata.port)
 192                     d.existing_weight = str(rdata.weight)
 193     if opts.verbose:
 194         print "Failed to find DNS entry %s" % d
 195
 196     return False
 197
 198
 199 ###########################################
 200 # get the list of substitution vars
 201 def get_subst_vars():
 202     global lp
 203     vars = {}
 204
 205     samdb = SamDB(url=lp.get("sam database"), session_info=system_session(), lp=lp)
 206
 207     vars['DNSDOMAIN'] = lp.get('realm').lower()
 208     vars['HOSTNAME']  = lp.get('netbios name').lower() + "." + vars['DNSDOMAIN']
 209     vars['NTDSGUID']  = samdb.get_ntds_GUID()
 210     vars['SITE']      = samdb.server_site_name()
 211     res = samdb.search(base=None, scope=SCOPE_BASE, attrs=["objectGUID"])
 212     guid = samdb.schema_format_value("objectGUID", res[0]['objectGUID'][0])
 213     vars['DOMAINGUID'] = guid
 214     return vars
 215
 216
 217 ############################################
 218 # call nsupdate for an entry
 219 def call_nsupdate(d):
 220     global ccachename, nsupdate_cmd
 221
 222     if opts.verbose:
 223         print "Calling nsupdate for %s" % d
 224
 225     if opts.use_file is not None:
 226         wfile = open(opts.use_file, 'a')
 227         fcntl.lockf(wfile, fcntl.LOCK_EX)
 228         wfile.write(str(d)+"\n")
 229         fcntl.lockf(wfile, fcntl.LOCK_UN)
 230         return
 231
 232     (tmp_fd, tmpfile) = tempfile.mkstemp()
 233     f = os.fdopen(tmp_fd, 'w')
 234     if d.type == "A":
 235         f.write("update add %s %u A %s\n" % (d.name, default_ttl, d.ip))
 236     if d.type == "SRV":
 237         if d.existing_port is not None:
 238             f.write("update delete %s SRV 0 %s %s %s\n" % (d.name, d.existing_weight,
 239                                                            d.existing_port, d.dest))
 240         f.write("update add %s %u SRV 0 100 %s %s\n" % (d.name, default_ttl, d.port, d.dest))
 241     if d.type == "CNAME":
 242         f.write("update add %s %u CNAME %s\n" % (d.name, default_ttl, d.dest))
 243     if opts.verbose:
 244         f.write("show\n")
 245     f.write("send\n")
 246     f.close()
 247
 248     os.putenv("KRB5CCNAME", ccachename)
 249     os.system("%s %s" % (nsupdate_cmd, tmpfile))
 250     os.unlink(tmpfile)
 251
 252
 253 # get the list of DNS entries we should have
 254 dns_update_list = lp.private_path('dns_update_list')
 255
 256 file = open(dns_update_list, "r")
 257
 258 # get the substitution dictionary
 259 sub_vars = get_subst_vars()
 260
 261 # build up a list of update commands to pass to nsupdate
 262 update_list = []
 263 dns_list = []
 264
 265 # read each line, and check that the DNS name exists
 266 line = file.readline()
 267 while line:
 268     line = line.rstrip().lstrip()
 269     if line[0] == "#":
 270         line = file.readline()
 271         continue
 272     d = parse_dns_line(line, sub_vars)
 273     dns_list.append(d)
 274     line = file.readline()
 275
 276 # now expand the entries, if any are A record with ip set to $IP
 277 # then replace with multiple entries, one for each interface IP
 278 for d in dns_list:
 279     if d.type == 'A' and d.ip == "$IP":
 280         d.ip = IPs[0]
 281         for i in range(len(IPs)-1):
 282             d2 = d
 283             d2.ip = IPs[i+1]
 284             dns_list.append(d2)
 285
 286 # now check if the entries already exist on the DNS server
 287 for d in dns_list:
 288     if not check_dns_name(d):
 289         update_list.append(d)
 290
 291 if len(update_list) == 0:
 292     if opts.verbose:
 293         print "No DNS updates needed"
 294     sys.exit(0)
 295
 296 # get our krb5 creds
 297 get_credentials(lp)
 298
 299 # ask nsupdate to add entries as needed
 300 for d in update_list:
 301     call_nsupdate(d)
 302
 303 # delete the ccache if we created it
 304 if ccachename is not None:
 305     os.unlink(ccachename)
 306
 307