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