source4/scripting/bin/samba_upgradedns

   1 #!/usr/bin/env python3
   2 #
   3 # Unix SMB/CIFS implementation.
   4 # Copyright (C) Amitay Isaacs <amitay@gmail.com> 2012
   5 #
   6 # Upgrade DNS provision from BIND9_FLATFILE to BIND9_DLZ or SAMBA_INTERNAL
   7 #
   8 # This program is free software; you can redistribute it and/or modify
   9 # it under the terms of the GNU General Public License as published by
  10 # the Free Software Foundation; either version 3 of the License, or
  11 # (at your option) any later version.
  12 #
  13 # This program is distributed in the hope that it will be useful,
  14 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 # GNU General Public License for more details.
  17 #
  18 # You should have received a copy of the GNU General Public License
  19 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20
  21 import sys
  22 import os
  23 import errno
  24 import optparse
  25 import logging
  26 import grp
  27 from base64 import b64encode
  28 import shlex
  29
  30 sys.path.insert(0, "bin/python")
  31
  32 import ldb
  33 import samba
  34 from samba import param
  35 from samba.auth import system_session
  36 from samba.ndr import (
  37     ndr_pack,
  38     ndr_unpack )
  39 import samba.getopt as options
  40 from samba.upgradehelpers import (
  41     get_paths,
  42     get_ldbs )
  43 from samba.dsdb import DS_DOMAIN_FUNCTION_2003
  44 from samba.provision import (
  45     find_provision_key_parameters,
  46     interface_ips_v4,
  47     interface_ips_v6 )
  48 from samba.provision.common import (
  49     setup_path,
  50     setup_add_ldif,
  51     FILL_FULL)
  52 from samba.provision.sambadns import (
  53     ARecord,
  54     AAAARecord,
  55     CNameRecord,
  56     NSRecord,
  57     SOARecord,
  58     SRVRecord,
  59     TXTRecord,
  60     get_dnsadmins_sid,
  61     add_dns_accounts,
  62     create_dns_partitions,
  63     fill_dns_data_partitions,
  64     create_dns_dir,
  65     secretsdb_setup_dns,
  66     create_samdb_copy,
  67     create_named_conf,
  68     create_named_txt )
  69 from samba.dcerpc import security
  70
  71 import dns.zone, dns.rdatatype
  72
  73 __docformat__ = 'restructuredText'
  74
  75
  76 def find_bind_gid():
  77     """Find system group id for bind9
  78     """
  79     for name in ["bind", "named"]:
  80         try:
  81             return grp.getgrnam(name)[2]
  82         except KeyError:
  83             pass
  84     return None
  85
  86
  87 def convert_dns_rdata(rdata, serial=1):
  88     """Convert resource records in dnsRecord format
  89     """
  90     if rdata.rdtype == dns.rdatatype.A:
  91         rec = ARecord(rdata.address, serial=serial)
  92     elif rdata.rdtype == dns.rdatatype.AAAA:
  93         rec = AAAARecord(rdata.address, serial=serial)
  94     elif rdata.rdtype == dns.rdatatype.CNAME:
  95         rec = CNameRecord(rdata.target.to_text(), serial=serial)
  96     elif rdata.rdtype == dns.rdatatype.NS:
  97         rec = NSRecord(rdata.target.to_text(), serial=serial)
  98     elif rdata.rdtype == dns.rdatatype.SRV:
  99         rec = SRVRecord(rdata.target.to_text(), int(rdata.port),
 100                         priority=int(rdata.priority), weight=int(rdata.weight),
 101                         serial=serial)
 102     elif rdata.rdtype == dns.rdatatype.TXT:
 103         slist = shlex.split(rdata.to_text())
 104         rec = TXTRecord(slist, serial=serial)
 105     elif rdata.rdtype == dns.rdatatype.SOA:
 106         rec = SOARecord(rdata.mname.to_text(), rdata.rname.to_text(),
 107                         serial=int(rdata.serial),
 108                         refresh=int(rdata.refresh), retry=int(rdata.retry),
 109                         expire=int(rdata.expire), minimum=int(rdata.minimum))
 110     else:
 111         rec = None
 112     return rec
 113
 114
 115 def import_zone_data(samdb, logger, zone, serial, domaindn, forestdn,
 116                      dnsdomain, dnsforest):
 117     """Insert zone data in DNS partitions
 118     """
 119     labels = dnsdomain.split('.')
 120     labels.append('')
 121     domain_root = dns.name.Name(labels)
 122     domain_prefix = "DC=%s,CN=MicrosoftDNS,DC=DomainDnsZones,%s" % (dnsdomain,
 123                                                                     domaindn)
 124
 125     tmp = "_msdcs.%s" % dnsforest
 126     labels = tmp.split('.')
 127     labels.append('')
 128     forest_root = dns.name.Name(labels)
 129     dnsmsdcs = "_msdcs.%s" % dnsforest
 130     forest_prefix = "DC=%s,CN=MicrosoftDNS,DC=ForestDnsZones,%s" % (dnsmsdcs,
 131                                                                     forestdn)
 132
 133     # Extract @ record
 134     at_record = zone.get_node(domain_root)
 135     zone.delete_node(domain_root)
 136
 137     # SOA record
 138     rdset = at_record.get_rdataset(dns.rdataclass.IN, dns.rdatatype.SOA)
 139     soa_rec = ndr_pack(convert_dns_rdata(rdset[0]))
 140     at_record.delete_rdataset(dns.rdataclass.IN, dns.rdatatype.SOA)
 141
 142     # NS record
 143     rdset = at_record.get_rdataset(dns.rdataclass.IN, dns.rdatatype.NS)
 144     ns_rec = ndr_pack(convert_dns_rdata(rdset[0]))
 145     at_record.delete_rdataset(dns.rdataclass.IN, dns.rdatatype.NS)
 146
 147     # A/AAAA records
 148     ip_recs = []
 149     for rdset in at_record:
 150         for r in rdset:
 151             rec = convert_dns_rdata(r)
 152             ip_recs.append(ndr_pack(rec))
 153
 154     # Add @ record for domain
 155     dns_rec = [soa_rec, ns_rec] + ip_recs
 156     msg = ldb.Message(ldb.Dn(samdb, 'DC=@,%s' % domain_prefix))
 157     msg["objectClass"] = ["top", "dnsNode"]
 158     msg["dnsRecord"] = ldb.MessageElement(dns_rec, ldb.FLAG_MOD_ADD,
 159                                           "dnsRecord")
 160     try:
 161         samdb.add(msg)
 162     except Exception:
 163         logger.error("Failed to add @ record for domain")
 164         raise
 165     logger.debug("Added @ record for domain")
 166
 167     # Add @ record for forest
 168     dns_rec = [soa_rec, ns_rec]
 169     msg = ldb.Message(ldb.Dn(samdb, 'DC=@,%s' % forest_prefix))
 170     msg["objectClass"] = ["top", "dnsNode"]
 171     msg["dnsRecord"] = ldb.MessageElement(dns_rec, ldb.FLAG_MOD_ADD,
 172                                           "dnsRecord")
 173     try:
 174         samdb.add(msg)
 175     except Exception:
 176         logger.error("Failed to add @ record for forest")
 177         raise
 178     logger.debug("Added @ record for forest")
 179
 180     # Add remaining records in domain and forest
 181     for node in zone.nodes:
 182         name = node.relativize(forest_root).to_text()
 183         if name == node.to_text():
 184             name = node.relativize(domain_root).to_text()
 185             dn = "DC=%s,%s" % (name, domain_prefix)
 186             fqdn = "%s.%s" % (name, dnsdomain)
 187         else:
 188             dn = "DC=%s,%s" % (name, forest_prefix)
 189             fqdn = "%s.%s" % (name, dnsmsdcs)
 190
 191         dns_rec = []
 192         for rdataset in zone.nodes[node]:
 193             for rdata in rdataset:
 194                 rec = convert_dns_rdata(rdata, serial)
 195                 if not rec:
 196                     logger.warn("Unsupported record type (%s) for %s, ignoring" %
 197                                 dns.rdatatype.to_text(rdata.rdatatype), name)
 198                 else:
 199                     dns_rec.append(ndr_pack(rec))
 200
 201         msg = ldb.Message(ldb.Dn(samdb, dn))
 202         msg["objectClass"] = ["top", "dnsNode"]
 203         msg["dnsRecord"] = ldb.MessageElement(dns_rec, ldb.FLAG_MOD_ADD,
 204                                               "dnsRecord")
 205         try:
 206             samdb.add(msg)
 207         except Exception:
 208             logger.error("Failed to add DNS record %s" % (fqdn))
 209             raise
 210         logger.debug("Added DNS record %s" % (fqdn))
 211
 212 def cleanup_remove_file(file_path):
 213     try:
 214         os.remove(file_path)
 215     except OSError as e:
 216         if e.errno not in [errno.EEXIST, errno.ENOENT]:
 217             pass
 218         else:
 219             logger.debug("Could not remove %s: %s" % (file_path, e.strerror))
 220
 221 def cleanup_remove_dir(dir_path):
 222     try:
 223         for root, dirs, files in os.walk(dir_path, topdown=False):
 224             for name in files:
 225                 os.remove(os.path.join(root, name))
 226             for name in dirs:
 227                 os.rmdir(os.path.join(root, name))
 228         os.rmdir(dir_path)
 229     except OSError as e:
 230         if e.errno not in [errno.EEXIST, errno.ENOENT]:
 231             pass
 232         else:
 233             logger.debug("Could not delete dir %s: %s" % (dir_path, e.strerror))
 234
 235 def cleanup_obsolete_dns_files(paths):
 236     cleanup_remove_file(os.path.join(paths.private_dir, "named.conf"))
 237     cleanup_remove_file(os.path.join(paths.private_dir, "named.conf.update"))
 238     cleanup_remove_file(os.path.join(paths.private_dir, "named.txt"))
 239
 240     cleanup_remove_dir(os.path.join(paths.private_dir, "dns"))
 241
 242
 243 # dnsprovision creates application partitions for AD based DNS mainly if the existing
 244 # provision was created using earlier snapshots of samba4 which did not have support
 245 # for DNS partitions
 246
 247 if __name__ == '__main__':
 248
 249     # Setup command line parser
 250     parser = optparse.OptionParser("upgradedns [options]")
 251     sambaopts = options.SambaOptions(parser)
 252     credopts = options.CredentialsOptions(parser)
 253
 254     parser.add_option_group(options.VersionOptions(parser))
 255     parser.add_option_group(sambaopts)
 256     parser.add_option_group(credopts)
 257
 258     parser.add_option("--dns-backend", type="choice", metavar="<BIND9_DLZ|SAMBA_INTERNAL>",
 259                       choices=["SAMBA_INTERNAL", "BIND9_DLZ"], default="SAMBA_INTERNAL",
 260                       help="The DNS server backend, default SAMBA_INTERNAL")
 261     parser.add_option("--migrate", type="choice", metavar="<yes|no>",
 262                       choices=["yes","no"], default="yes",
 263                       help="Migrate existing zone data, default yes")
 264     parser.add_option("--verbose", help="Be verbose", action="store_true")
 265
 266     opts = parser.parse_args()[0]
 267
 268     if opts.dns_backend is None:
 269         opts.dns_backend = 'SAMBA_INTERNAL'
 270
 271     if opts.migrate:
 272         autofill = False
 273     else:
 274         autofill = True
 275
 276     # Set up logger
 277     logger = logging.getLogger("upgradedns")
 278     logger.addHandler(logging.StreamHandler(sys.stdout))
 279     logger.setLevel(logging.INFO)
 280     if opts.verbose:
 281         logger.setLevel(logging.DEBUG)
 282
 283     lp = sambaopts.get_loadparm()
 284     lp.load(lp.configfile)
 285     creds = credopts.get_credentials(lp)
 286
 287     logger.info("Reading domain information")
 288     paths = get_paths(param, smbconf=lp.configfile)
 289     paths.bind_gid = find_bind_gid()
 290     ldbs = get_ldbs(paths, creds, system_session(), lp)
 291     names = find_provision_key_parameters(ldbs.sam, ldbs.secrets, ldbs.idmap,
 292                                            paths, lp.configfile, lp)
 293
 294     if names.domainlevel < DS_DOMAIN_FUNCTION_2003:
 295         logger.error("Cannot create AD based DNS for OS level < 2003")
 296         sys.exit(1)
 297
 298     domaindn = names.domaindn
 299     forestdn = names.rootdn
 300
 301     dnsdomain = names.dnsdomain.lower()
 302     dnsforest = dnsdomain
 303
 304     site = names.sitename
 305     hostname = names.hostname
 306     dnsname = '%s.%s' % (hostname, dnsdomain)
 307
 308     domainsid = names.domainsid
 309     domainguid = names.domainguid
 310     ntdsguid = names.ntdsguid
 311
 312     # Check for DNS accounts and create them if required
 313     try:
 314         msg = ldbs.sam.search(base=domaindn, scope=ldb.SCOPE_DEFAULT,
 315                               expression='(sAMAccountName=DnsAdmins)',
 316                               attrs=['objectSid'])
 317         dnsadmins_sid = ndr_unpack(security.dom_sid, msg[0]['objectSid'][0])
 318     except IndexError:
 319         logger.info("Adding DNS accounts")
 320         add_dns_accounts(ldbs.sam, domaindn)
 321         dnsadmins_sid = get_dnsadmins_sid(ldbs.sam, domaindn)
 322     else:
 323         logger.info("DNS accounts already exist")
 324
 325     # Import dns records from zone file
 326     if os.path.exists(paths.dns):
 327         logger.info("Reading records from zone file %s" % paths.dns)
 328         try:
 329             zone = dns.zone.from_file(paths.dns, relativize=False)
 330             rrset = zone.get_rdataset("%s." % dnsdomain, dns.rdatatype.SOA)
 331             serial = int(rrset[0].serial)
 332         except Exception as e:
 333             logger.warn("Error parsing DNS data from '%s' (%s)" % (paths.dns, str(e)))
 334             logger.warn("DNS records will be automatically created")
 335             autofill = True
 336     else:
 337         logger.info("No zone file %s" % paths.dns)
 338         logger.warn("DNS records will be automatically created")
 339         autofill = True
 340
 341     # Create DNS partitions if missing and fill DNS information
 342     try:
 343         expression = '(|(dnsRoot=DomainDnsZones.%s)(dnsRoot=ForestDnsZones.%s))' % \
 344                      (dnsdomain, dnsforest)
 345         msg = ldbs.sam.search(base=names.configdn, scope=ldb.SCOPE_DEFAULT,
 346                               expression=expression, attrs=['nCName'])
 347         ncname = msg[0]['nCName'][0]
 348     except IndexError:
 349         logger.info("Creating DNS partitions")
 350
 351         logger.info("Looking up IPv4 addresses")
 352         hostip = interface_ips_v4(lp)
 353         try:
 354             hostip.remove('127.0.0.1')
 355         except ValueError:
 356             pass
 357         if not hostip:
 358             logger.error("No IPv4 addresses found")
 359             sys.exit(1)
 360         else:
 361             hostip = hostip[0]
 362             logger.debug("IPv4 addresses: %s" % hostip)
 363
 364         logger.info("Looking up IPv6 addresses")
 365         hostip6 = interface_ips_v6(lp)
 366         if not hostip6:
 367             hostip6 = None
 368         else:
 369             hostip6 = hostip6[0]
 370         logger.debug("IPv6 addresses: %s" % hostip6)
 371
 372         create_dns_partitions(ldbs.sam, domainsid, names, domaindn, forestdn,
 373                               dnsadmins_sid, FILL_FULL)
 374
 375         logger.info("Populating DNS partitions")
 376         fill_dns_data_partitions(ldbs.sam, domainsid, site, domaindn, forestdn,
 377                              dnsdomain, dnsforest, hostname, hostip, hostip6,
 378                              domainguid, ntdsguid, dnsadmins_sid,
 379                              autofill=autofill)
 380
 381         if not autofill:
 382             logger.info("Importing records from zone file")
 383             import_zone_data(ldbs.sam, logger, zone, serial, domaindn, forestdn,
 384                              dnsdomain, dnsforest)
 385     else:
 386         logger.info("DNS partitions already exist")
 387
 388     # Mark that we are hosting DNS partitions
 389     try:
 390         dns_nclist = [ 'DC=DomainDnsZones,%s' % domaindn,
 391                        'DC=ForestDnsZones,%s' % forestdn ]
 392
 393         msgs = ldbs.sam.search(base=names.serverdn, scope=ldb.SCOPE_DEFAULT,
 394                                expression='(objectclass=nTDSDSa)',
 395                                attrs=['hasPartialReplicaNCs',
 396                                       'msDS-hasMasterNCs'])
 397         msg = msgs[0]
 398
 399         master_nclist = []
 400         ncs = msg.get("msDS-hasMasterNCs")
 401         if ncs:
 402             for nc in ncs:
 403                 master_nclist.append(str(nc))
 404
 405         partial_nclist = []
 406         ncs = msg.get("hasPartialReplicaNCs")
 407         if ncs:
 408             for nc in ncs:
 409                 partial_nclist.append(str(nc))
 410
 411         modified_master = False
 412         modified_partial = False
 413
 414         for nc in dns_nclist:
 415             if nc not in master_nclist:
 416                 master_nclist.append(nc)
 417                 modified_master = True
 418             if nc in partial_nclist:
 419                 partial_nclist.remove(nc)
 420                 modified_partial = True
 421
 422         if modified_master or modified_partial:
 423             logger.debug("Updating msDS-hasMasterNCs and hasPartialReplicaNCs attributes")
 424             m = ldb.Message()
 425             m.dn = msg.dn
 426             if modified_master:
 427                 m["msDS-hasMasterNCs"] = ldb.MessageElement(master_nclist,
 428                                                             ldb.FLAG_MOD_REPLACE,
 429                                                             "msDS-hasMasterNCs")
 430             if modified_partial:
 431                 if partial_nclist:
 432                     m["hasPartialReplicaNCs"] = ldb.MessageElement(partial_nclist,
 433                                                                    ldb.FLAG_MOD_REPLACE,
 434                                                                    "hasPartialReplicaNCs")
 435                 else:
 436                     m["hasPartialReplicaNCs"] = ldb.MessageElement(ncs,
 437                                                                    ldb.FLAG_MOD_DELETE,
 438                                                                    "hasPartialReplicaNCs")
 439             ldbs.sam.modify(m)
 440     except Exception:
 441         raise
 442
 443     # Special stuff for DLZ backend
 444     if opts.dns_backend == "BIND9_DLZ":
 445         config_migration = False
 446
 447         if (paths.private_dir != paths.binddns_dir and
 448             os.path.isfile(os.path.join(paths.private_dir, "named.conf"))):
 449             config_migration = True
 450
 451         # Check if dns-HOSTNAME account exists and create it if required
 452         secrets_msgs = ldbs.secrets.search(expression='(samAccountName=dns-%s)' % hostname, attrs=['secret'])
 453         msg = ldbs.sam.search(base=domaindn, scope=ldb.SCOPE_DEFAULT,
 454                               expression='(sAMAccountName=dns-%s)' % (hostname),
 455                               attrs=[])
 456
 457         if len(secrets_msgs) == 0 or len(msg) == 0:
 458             logger.info("Adding dns-%s account" % hostname)
 459
 460             if len(secrets_msgs) == 1:
 461                 dn = secrets_msgs[0].dn
 462                 ldbs.secrets.delete(dn)
 463
 464             if len(msg) == 1:
 465                 dn = msg[0].dn
 466                 ldbs.sam.delete(dn)
 467
 468             dnspass = samba.generate_random_password(128, 255)
 469             setup_add_ldif(ldbs.sam, setup_path("provision_dns_add_samba.ldif"), {
 470                     "DNSDOMAIN": dnsdomain,
 471                     "DOMAINDN": domaindn,
 472                     "DNSPASS_B64": b64encode(dnspass.encode('utf-16-le')).decode('utf8'),
 473                     "HOSTNAME" : hostname,
 474                     "DNSNAME" : dnsname }
 475                            )
 476
 477             res = ldbs.sam.search(base=domaindn, scope=ldb.SCOPE_DEFAULT,
 478                                   expression='(sAMAccountName=dns-%s)' % (hostname),
 479                                   attrs=["msDS-KeyVersionNumber"])
 480             if "msDS-KeyVersionNumber" in res[0]:
 481                 dns_key_version_number = int(res[0]["msDS-KeyVersionNumber"][0])
 482             else:
 483                 dns_key_version_number = None
 484
 485             secretsdb_setup_dns(ldbs.secrets, names,
 486                                 paths.private_dir, paths.binddns_dir, realm=names.realm,
 487                                 dnsdomain=names.dnsdomain,
 488                                 dns_keytab_path=paths.dns_keytab, dnspass=dnspass,
 489                                 key_version_number=dns_key_version_number)
 490
 491         else:
 492             logger.info("dns-%s account already exists" % hostname)
 493
 494         private_dns_keytab_path = os.path.join(paths.private_dir, paths.dns_keytab)
 495         bind_dns_keytab_path = os.path.join(paths.binddns_dir, paths.dns_keytab)
 496
 497         if os.path.isfile(private_dns_keytab_path):
 498             if os.path.isfile(bind_dns_keytab_path):
 499                 try:
 500                     os.unlink(bind_dns_keytab_path)
 501                 except OSError as e:
 502                     logger.error("Failed to remove %s: %s" %
 503                                  (bind_dns_keytab_path, e.strerror))
 504
 505             # link the dns.keytab to the bind-dns directory
 506             try:
 507                 os.link(private_dns_keytab_path, bind_dns_keytab_path)
 508             except OSError as e:
 509                 logger.error("Failed to create link %s -> %s: %s" %
 510                              (private_dns_keytab_path, bind_dns_keytab_path, e.strerror))
 511
 512             # chown the dns.keytab in the bind-dns directory
 513             if paths.bind_gid is not None:
 514                 try:
 515                     os.chmod(paths.binddns_dir, 0o770)
 516                     os.chown(paths.binddns_dir, -1, paths.bind_gid)
 517                 except OSError:
 518                     if 'SAMBA_SELFTEST' not in os.environ:
 519                         logger.info("Failed to chown %s to bind gid %u",
 520                                     paths.binddns_dir, paths.bind_gid)
 521                 try:
 522                     os.chmod(bind_dns_keytab_path, 0o640)
 523                     os.chown(bind_dns_keytab_path, -1, paths.bind_gid)
 524                 except OSError:
 525                     if 'SAMBA_SELFTEST' not in os.environ:
 526                         logger.info("Failed to chown %s to bind gid %u",
 527                                     bind_dns_keytab_path, paths.bind_gid)
 528
 529
 530         # This forces a re-creation of dns directory and all the files within
 531         # It's an overkill, but it's easier to re-create a samdb copy, rather
 532         # than trying to fix a broken copy.
 533         create_dns_dir(logger, paths)
 534
 535         # Setup a copy of SAM for BIND9
 536         create_samdb_copy(ldbs.sam, logger, paths, names, domainsid,
 537                           domainguid)
 538
 539         create_named_conf(paths, names.realm, dnsdomain, opts.dns_backend, logger)
 540
 541         create_named_txt(paths.namedtxt, names.realm, dnsdomain, dnsname,
 542                          paths.binddns_dir, paths.dns_keytab)
 543
 544         cleanup_obsolete_dns_files(paths)
 545
 546         if config_migration:
 547             logger.info("ATTENTION: The BIND configuration and keytab has been moved to: %s",
 548                         paths.binddns_dir)
 549             logger.info("           Please update your BIND configuration accordingly.")
 550         else:
 551             logger.info("See %s for an example configuration include file for BIND", paths.namedconf)
 552             logger.info("and %s for further documentation required for secure DNS "
 553                         "updates", paths.namedtxt)
 554
 555     elif opts.dns_backend == "SAMBA_INTERNAL":
 556         # Make sure to remove everything from the bind-dns directory to avoid
 557         # possible security issues with the named group having write access
 558         # to all AD partions
 559         cleanup_remove_file(os.path.join(paths.binddns_dir, "dns.keytab"))
 560         cleanup_remove_file(os.path.join(paths.binddns_dir, "named.conf"))
 561         cleanup_remove_file(os.path.join(paths.binddns_dir, "named.conf.update"))
 562         cleanup_remove_file(os.path.join(paths.binddns_dir, "named.txt"))
 563
 564         cleanup_remove_dir(os.path.dirname(paths.dns))
 565
 566         try:
 567             os.chmod(paths.private_dir, 0o700)
 568             os.chown(paths.private_dir, -1, 0)
 569         except:
 570             logger.warn("Failed to restore owner and permissions for %s",
 571                         (paths.private_dir))
 572
 573         # Check if dns-HOSTNAME account exists and delete it if required
 574         try:
 575             dn_str = 'samAccountName=dns-%s,CN=Principals' % hostname
 576             msg = ldbs.secrets.search(expression='(dn=%s)' % dn_str, attrs=[])
 577             dn = msg[0].dn
 578         except IndexError:
 579             dn = None
 580
 581         if dn is not None:
 582             try:
 583                 ldbs.secrets.delete(dn)
 584             except Exception:
 585                 logger.info("Failed to delete %s from secrets.ldb" % dn)
 586
 587         try:
 588             msg = ldbs.sam.search(base=domaindn, scope=ldb.SCOPE_DEFAULT,
 589                                   expression='(sAMAccountName=dns-%s)' % (hostname),
 590                                   attrs=[])
 591             dn = msg[0].dn
 592         except IndexError:
 593             dn = None
 594
 595         if dn is not None:
 596             try:
 597                 ldbs.sam.delete(dn)
 598             except Exception:
 599                 logger.info("Failed to delete %s from sam.ldb" % dn)
 600
 601     logger.info("Finished upgrading DNS")
 602
 603     services = lp.get("server services")
 604     for service in services:
 605         if service == "dns":
 606             if opts.dns_backend.startswith("BIND"):
 607                 logger.info("You have switched to using %s as your dns backend,"
 608                         " but still have the internal dns starting. Please"
 609                         " make sure you add '-dns' to your server services"
 610                         " line in your smb.conf." % opts.dns_backend)
 611             break
 612     else:
 613         if opts.dns_backend == "SAMBA_INTERNAL":
 614             logger.info("You have switched to using %s as your dns backend,"
 615                     " but you still have samba starting looking for a"
 616                     " BIND backend. Please remove the -dns from your"
 617                     " server services line." % opts.dns_backend)