invirt-dns

   1 #!/usr/bin/python
   2 from twisted.internet import reactor
   3 from twisted.names import server
   4 from twisted.names import dns
   5 from twisted.names import common
   6 from twisted.names import authority
   7 from twisted.internet import defer
   8 from twisted.python import failure
   9
  10 from invirt.common import InvirtConfigError
  11 from invirt.config import structs as config
  12 import invirt.database
  13 import psycopg2
  14 import sqlalchemy
  15 import time
  16 import re
  17
  18 class DatabaseAuthority(common.ResolverBase):
  19     """An Authority that is loaded from a file."""
  20
  21     soa = None
  22
  23     def __init__(self, domains=None, database=None):
  24         common.ResolverBase.__init__(self)
  25         if database is not None:
  26             invirt.database.connect(database)
  27         else:
  28             invirt.database.connect()
  29         if domains is not None:
  30             self.domains = domains
  31         else:
  32             self.domains = config.dns.domains
  33         ns = config.dns.nameservers[0]
  34         self.soa = dns.Record_SOA(mname=ns.hostname,
  35                                   rname=config.dns.contact.replace('@','.',1),
  36                                   serial=1, refresh=3600, retry=900,
  37                                   expire=3600000, minimum=21600, ttl=3600)
  38         self.ns = dns.Record_NS(name=ns.hostname, ttl=3600)
  39         record = dns.Record_A(address=ns.ip, ttl=3600)
  40         self.ns1 = dns.RRHeader(ns.hostname, dns.A, dns.IN,
  41                                 3600, record, auth=True)
  42
  43
  44     def _lookup(self, name, cls, type, timeout = None):
  45         for i in range(3):
  46             try:
  47                 value = self._lookup_unsafe(name, cls, type, timeout = None)
  48             except (psycopg2.OperationalError, sqlalchemy.exceptions.SQLError):
  49                 if i == 2:
  50                     raise
  51                 print "Reloading database"
  52                 time.sleep(0.5)
  53                 continue
  54             else:
  55                 return value
  56
  57     def _lookup_unsafe(self, name, cls, type, timeout):
  58         invirt.database.clear_cache()
  59
  60         ttl = 900
  61         name = name.lower()
  62
  63         if name in self.domains:
  64             domain = name
  65         else:
  66             # Look for the longest-matching domain.
  67             best_domain = ''
  68             for domain in self.domains:
  69                 if name.endswith('.'+domain) and len(domain) > len(best_domain):
  70                     best_domain = domain
  71             if best_domain == '':
  72                 if name.endswith('.in-addr.arpa'):
  73                     # Act authoritative for the IP address for reverse resolution requests
  74                     best_domain = name
  75                 else:
  76                     return defer.fail(failure.Failure(dns.DomainError(name)))
  77             domain = best_domain
  78         results = []
  79         authority = []
  80         additional = [self.ns1]
  81         authority.append(dns.RRHeader(domain, dns.NS, dns.IN,
  82                                       3600, self.ns, auth=True))
  83
  84         # The order of logic:
  85         # - What class?
  86         # - What domain: in-addr.arpa, domain root, or subdomain?
  87         # - What query type: A, PTR, NS, ...?
  88
  89         if cls != dns.IN:
  90             # Hahaha.  No.
  91             return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
  92
  93         if name.endswith(".in-addr.arpa"):
  94             if type in (dns.PTR, dns.ALL_RECORDS):
  95                 ip = '.'.join(reversed(name.split('.')[:-2]))
  96                 value = invirt.database.NIC.query.filter_by(ip=ip).first()
  97                 if value and value.hostname:
  98                     hostname = value.hostname
  99                     if '.' not in hostname:
 100                         hostname = hostname + "." + config.dns.domains[0]
 101                     record = dns.Record_PTR(hostname, ttl)
 102                     results.append(dns.RRHeader(name, dns.PTR, dns.IN,
 103                                                 ttl, record, auth=True))
 104                 else: # IP address doesn't point to an active host
 105                     return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
 106             elif type == dns.SOA:
 107                 results.append(dns.RRHeader(domain, dns.SOA, dns.IN,
 108                                             ttl, self.soa, auth=True))
 109             # FIXME: Should only return success with no records if the name actually exists
 110
 111         elif name == domain or name == '.'+domain:
 112             if type in (dns.A, dns.ALL_RECORDS):
 113                 record = dns.Record_A(config.dns.nameservers[0].ip, ttl)
 114                 results.append(dns.RRHeader(name, dns.A, dns.IN,
 115                                             ttl, record, auth=True))
 116             elif type == dns.NS:
 117                 results.append(dns.RRHeader(domain, dns.NS, dns.IN,
 118                                             ttl, self.ns, auth=True))
 119                 authority = []
 120             elif type == dns.SOA:
 121                 results.append(dns.RRHeader(domain, dns.SOA, dns.IN,
 122                                             ttl, self.soa, auth=True))
 123
 124         else:
 125             host = name[:-len(domain)-1]
 126             value = invirt.database.NIC.query.filter_by(hostname=host).first()
 127             if value:
 128                 ip = value.ip
 129             else:
 130                 value = invirt.database.Machine.query().filter_by(name=host).first()
 131                 if value:
 132                     ip = value.nics[0].ip
 133                 else:
 134                     return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
 135             if ip is None:
 136                 return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
 137             if type in (dns.A, dns.ALL_RECORDS):
 138                 record = dns.Record_A(ip, ttl)
 139                 results.append(dns.RRHeader(name, dns.A, dns.IN,
 140                                             ttl, record, auth=True))
 141             elif type == dns.SOA:
 142                 results.append(dns.RRHeader(domain, dns.SOA, dns.IN,
 143                                             ttl, self.soa, auth=True))
 144
 145         if len(results) == 0:
 146             authority = []
 147             additional = []
 148         return defer.succeed((results, authority, additional))
 149
 150 class DelegatingQuotingBindAuthority(authority.BindAuthority):
 151     """
 152     A delegating BindAuthority that (almost) deals with quoting correctly
 153
 154     This will catch double quotes as marking the start or end of a
 155     quoted phrase, unless the double quote is escaped by a backslash
 156     """
 157     # Match either a quoted or unquoted string literal followed by
 158     # whitespace or the end of line.  This yields two groups, one of
 159     # which has a match, and the other of which is None, depending on
 160     # whether the string literal was quoted or unquoted; this is what
 161     # necessitates the subsequent filtering out of groups that are
 162     # None.
 163     string_pat = \
 164             re.compile(r'"((?:[^"\\]|\\.)*)"|((?:[^\\\s]|\\.)+)(?:\s+|\s*$)')
 165
 166     # For interpreting escapes.
 167     escape_pat = re.compile(r'\\(.)')
 168
 169     def collapseContinuations(self, lines):
 170         L = []
 171         state = 0
 172         for line in lines:
 173             if state == 0:
 174                 if line.find('(') == -1:
 175                     L.append(line)
 176                 else:
 177                     L.append(line[:line.find('(')])
 178                     state = 1
 179             else:
 180                 if line.find(')') != -1:
 181                     L[-1] += ' ' + line[:line.find(')')]
 182                     state = 0
 183                 else:
 184                     L[-1] += ' ' + line
 185         lines = L
 186         L = []
 187
 188         for line in lines:
 189             in_quote = False
 190             split_line = []
 191             for m in self.string_pat.finditer(line):
 192                 [x] = [x for x in m.groups() if x is not None]
 193                 split_line.append(self.escape_pat.sub(r'\1', x))
 194             L.append(split_line)
 195         return filter(None, L)
 196
 197     def _lookup(self, name, cls, type, timeout = None):
 198         maybeDelegate = False
 199         deferredResult = authority.BindAuthority._lookup(self, name, cls,
 200                                                          type, timeout)
 201         # If we didn't find an exact match for the name we were seeking,
 202         # check if it's within a subdomain we're supposed to delegate to
 203         # some other DNS server.
 204         while (isinstance(deferredResult.result, failure.Failure)
 205                and '.' in name):
 206             maybeDelegate = True
 207             name = name[name.find('.') + 1 :]
 208             deferredResult = authority.BindAuthority._lookup(self, name, cls,
 209                                                              dns.NS, timeout)
 210         # If we found somewhere to delegate the query to, our _lookup()
 211         # for the NS record resulted in it being in the 'results' section.
 212         # We need to instead return that information in the 'authority'
 213         # section to delegate, and return an empty 'results' section
 214         # (because we didn't find the name we were asked about).  We
 215         # leave the 'additional' section as we received it because it
 216         # may contain A records for the DNS server we're delegating to.
 217         if maybeDelegate and not isinstance(deferredResult.result,
 218                                             failure.Failure):
 219             (nsResults, nsAuthority, nsAdditional) = deferredResult.result
 220             deferredResult = defer.succeed(([], nsResults, nsAdditional))
 221         return deferredResult
 222
 223 if '__main__' == __name__:
 224     resolvers = []
 225     try:
 226         for zone in config.dns.zone_files:
 227             for origin in config.dns.domains:
 228                 r = DelegatingQuotingBindAuthority(zone)
 229                 # This sucks, but if I want a generic zone file, I have to
 230                 # reload the information by hand
 231                 r.origin = origin
 232                 lines = open(zone).readlines()
 233                 lines = r.collapseContinuations(r.stripComments(lines))
 234                 r.parseLines(lines)
 235
 236                 resolvers.append(r)
 237     except InvirtConfigError:
 238         # Don't care if zone_files isn't defined
 239         pass
 240     resolvers.append(DatabaseAuthority())
 241
 242     verbosity = 0
 243     f = server.DNSServerFactory(authorities=resolvers, verbose=verbosity)
 244     p = dns.DNSDatagramProtocol(f)
 245     f.noisy = p.noisy = verbosity
 246
 247     reactor.listenUDP(53, p)
 248     reactor.listenTCP(53, f)
 249     reactor.run()