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Diffstat (limited to 'lib/dnspython/dns/resolver.py')
| -rw-r--r-- | lib/dnspython/dns/resolver.py | 761 |
1 files changed, 761 insertions, 0 deletions
diff --git a/lib/dnspython/dns/resolver.py b/lib/dnspython/dns/resolver.py new file mode 100644 index 0000000000..372d7d8361 --- /dev/null +++ b/lib/dnspython/dns/resolver.py @@ -0,0 +1,761 @@ +# Copyright (C) 2003-2007, 2009, 2010 Nominum, Inc. +# +# Permission to use, copy, modify, and distribute this software and its +# documentation for any purpose with or without fee is hereby granted, +# provided that the above copyright notice and this permission notice +# appear in all copies. +# +# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES +# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF +# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR +# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES +# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN +# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT +# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + +"""DNS stub resolver. + +@var default_resolver: The default resolver object +@type default_resolver: dns.resolver.Resolver object""" + +import socket +import sys +import time + +import dns.exception +import dns.message +import dns.name +import dns.query +import dns.rcode +import dns.rdataclass +import dns.rdatatype + +if sys.platform == 'win32': + import _winreg + +class NXDOMAIN(dns.exception.DNSException): + """The query name does not exist.""" + pass + +# The definition of the Timeout exception has moved from here to the +# dns.exception module. We keep dns.resolver.Timeout defined for +# backwards compatibility. + +Timeout = dns.exception.Timeout + +class NoAnswer(dns.exception.DNSException): + """The response did not contain an answer to the question.""" + pass + +class NoNameservers(dns.exception.DNSException): + """No non-broken nameservers are available to answer the query.""" + pass + +class NotAbsolute(dns.exception.DNSException): + """Raised if an absolute domain name is required but a relative name + was provided.""" + pass + +class NoRootSOA(dns.exception.DNSException): + """Raised if for some reason there is no SOA at the root name. + This should never happen!""" + pass + + +class Answer(object): + """DNS stub resolver answer + + Instances of this class bundle up the result of a successful DNS + resolution. + + For convenience, the answer object implements much of the sequence + protocol, forwarding to its rrset. E.g. "for a in answer" is + equivalent to "for a in answer.rrset", "answer[i]" is equivalent + to "answer.rrset[i]", and "answer[i:j]" is equivalent to + "answer.rrset[i:j]". + + Note that CNAMEs or DNAMEs in the response may mean that answer + node's name might not be the query name. + + @ivar qname: The query name + @type qname: dns.name.Name object + @ivar rdtype: The query type + @type rdtype: int + @ivar rdclass: The query class + @type rdclass: int + @ivar response: The response message + @type response: dns.message.Message object + @ivar rrset: The answer + @type rrset: dns.rrset.RRset object + @ivar expiration: The time when the answer expires + @type expiration: float (seconds since the epoch) + """ + def __init__(self, qname, rdtype, rdclass, response): + self.qname = qname + self.rdtype = rdtype + self.rdclass = rdclass + self.response = response + min_ttl = -1 + rrset = None + for count in xrange(0, 15): + try: + rrset = response.find_rrset(response.answer, qname, + rdclass, rdtype) + if min_ttl == -1 or rrset.ttl < min_ttl: + min_ttl = rrset.ttl + break + except KeyError: + if rdtype != dns.rdatatype.CNAME: + try: + crrset = response.find_rrset(response.answer, + qname, + rdclass, + dns.rdatatype.CNAME) + if min_ttl == -1 or crrset.ttl < min_ttl: + min_ttl = crrset.ttl + for rd in crrset: + qname = rd.target + break + continue + except KeyError: + raise NoAnswer + raise NoAnswer + if rrset is None: + raise NoAnswer + self.rrset = rrset + self.expiration = time.time() + min_ttl + + def __getattr__(self, attr): + if attr == 'name': + return self.rrset.name + elif attr == 'ttl': + return self.rrset.ttl + elif attr == 'covers': + return self.rrset.covers + elif attr == 'rdclass': + return self.rrset.rdclass + elif attr == 'rdtype': + return self.rrset.rdtype + else: + raise AttributeError(attr) + + def __len__(self): + return len(self.rrset) + + def __iter__(self): + return iter(self.rrset) + + def __getitem__(self, i): + return self.rrset[i] + + def __delitem__(self, i): + del self.rrset[i] + + def __getslice__(self, i, j): + return self.rrset[i:j] + + def __delslice__(self, i, j): + del self.rrset[i:j] + +class Cache(object): + """Simple DNS answer cache. + + @ivar data: A dictionary of cached data + @type data: dict + @ivar cleaning_interval: The number of seconds between cleanings. The + default is 300 (5 minutes). + @type cleaning_interval: float + @ivar next_cleaning: The time the cache should next be cleaned (in seconds + since the epoch.) + @type next_cleaning: float + """ + + def __init__(self, cleaning_interval=300.0): + """Initialize a DNS cache. + + @param cleaning_interval: the number of seconds between periodic + cleanings. The default is 300.0 + @type cleaning_interval: float. + """ + + self.data = {} + self.cleaning_interval = cleaning_interval + self.next_cleaning = time.time() + self.cleaning_interval + + def maybe_clean(self): + """Clean the cache if it's time to do so.""" + + now = time.time() + if self.next_cleaning <= now: + keys_to_delete = [] + for (k, v) in self.data.iteritems(): + if v.expiration <= now: + keys_to_delete.append(k) + for k in keys_to_delete: + del self.data[k] + now = time.time() + self.next_cleaning = now + self.cleaning_interval + + def get(self, key): + """Get the answer associated with I{key}. Returns None if + no answer is cached for the key. + @param key: the key + @type key: (dns.name.Name, int, int) tuple whose values are the + query name, rdtype, and rdclass. + @rtype: dns.resolver.Answer object or None + """ + + self.maybe_clean() + v = self.data.get(key) + if v is None or v.expiration <= time.time(): + return None + return v + + def put(self, key, value): + """Associate key and value in the cache. + @param key: the key + @type key: (dns.name.Name, int, int) tuple whose values are the + query name, rdtype, and rdclass. + @param value: The answer being cached + @type value: dns.resolver.Answer object + """ + + self.maybe_clean() + self.data[key] = value + + def flush(self, key=None): + """Flush the cache. + + If I{key} is specified, only that item is flushed. Otherwise + the entire cache is flushed. + + @param key: the key to flush + @type key: (dns.name.Name, int, int) tuple or None + """ + + if not key is None: + if self.data.has_key(key): + del self.data[key] + else: + self.data = {} + self.next_cleaning = time.time() + self.cleaning_interval + +class Resolver(object): + """DNS stub resolver + + @ivar domain: The domain of this host + @type domain: dns.name.Name object + @ivar nameservers: A list of nameservers to query. Each nameserver is + a string which contains the IP address of a nameserver. + @type nameservers: list of strings + @ivar search: The search list. If the query name is a relative name, + the resolver will construct an absolute query name by appending the search + names one by one to the query name. + @type search: list of dns.name.Name objects + @ivar port: The port to which to send queries. The default is 53. + @type port: int + @ivar timeout: The number of seconds to wait for a response from a + server, before timing out. + @type timeout: float + @ivar lifetime: The total number of seconds to spend trying to get an + answer to the question. If the lifetime expires, a Timeout exception + will occur. + @type lifetime: float + @ivar keyring: The TSIG keyring to use. The default is None. + @type keyring: dict + @ivar keyname: The TSIG keyname to use. The default is None. + @type keyname: dns.name.Name object + @ivar keyalgorithm: The TSIG key algorithm to use. The default is + dns.tsig.default_algorithm. + @type keyalgorithm: string + @ivar edns: The EDNS level to use. The default is -1, no Edns. + @type edns: int + @ivar ednsflags: The EDNS flags + @type ednsflags: int + @ivar payload: The EDNS payload size. The default is 0. + @type payload: int + @ivar cache: The cache to use. The default is None. + @type cache: dns.resolver.Cache object + """ + def __init__(self, filename='/etc/resolv.conf', configure=True): + """Initialize a resolver instance. + + @param filename: The filename of a configuration file in + standard /etc/resolv.conf format. This parameter is meaningful + only when I{configure} is true and the platform is POSIX. + @type filename: string or file object + @param configure: If True (the default), the resolver instance + is configured in the normal fashion for the operating system + the resolver is running on. (I.e. a /etc/resolv.conf file on + POSIX systems and from the registry on Windows systems.) + @type configure: bool""" + + self.reset() + if configure: + if sys.platform == 'win32': + self.read_registry() + elif filename: + self.read_resolv_conf(filename) + + def reset(self): + """Reset all resolver configuration to the defaults.""" + self.domain = \ + dns.name.Name(dns.name.from_text(socket.gethostname())[1:]) + if len(self.domain) == 0: + self.domain = dns.name.root + self.nameservers = [] + self.search = [] + self.port = 53 + self.timeout = 2.0 + self.lifetime = 30.0 + self.keyring = None + self.keyname = None + self.keyalgorithm = dns.tsig.default_algorithm + self.edns = -1 + self.ednsflags = 0 + self.payload = 0 + self.cache = None + + def read_resolv_conf(self, f): + """Process f as a file in the /etc/resolv.conf format. If f is + a string, it is used as the name of the file to open; otherwise it + is treated as the file itself.""" + if isinstance(f, str) or isinstance(f, unicode): + try: + f = open(f, 'r') + except IOError: + # /etc/resolv.conf doesn't exist, can't be read, etc. + # We'll just use the default resolver configuration. + self.nameservers = ['127.0.0.1'] + return + want_close = True + else: + want_close = False + try: + for l in f: + if len(l) == 0 or l[0] == '#' or l[0] == ';': + continue + tokens = l.split() + if len(tokens) == 0: + continue + if tokens[0] == 'nameserver': + self.nameservers.append(tokens[1]) + elif tokens[0] == 'domain': + self.domain = dns.name.from_text(tokens[1]) + elif tokens[0] == 'search': + for suffix in tokens[1:]: + self.search.append(dns.name.from_text(suffix)) + finally: + if want_close: + f.close() + if len(self.nameservers) == 0: + self.nameservers.append('127.0.0.1') + + def _determine_split_char(self, entry): + # + # The windows registry irritatingly changes the list element + # delimiter in between ' ' and ',' (and vice-versa) in various + # versions of windows. + # + if entry.find(' ') >= 0: + split_char = ' ' + elif entry.find(',') >= 0: + split_char = ',' + else: + # probably a singleton; treat as a space-separated list. + split_char = ' ' + return split_char + + def _config_win32_nameservers(self, nameservers): + """Configure a NameServer registry entry.""" + # we call str() on nameservers to convert it from unicode to ascii + nameservers = str(nameservers) + split_char = self._determine_split_char(nameservers) + ns_list = nameservers.split(split_char) + for ns in ns_list: + if not ns in self.nameservers: + self.nameservers.append(ns) + + def _config_win32_domain(self, domain): + """Configure a Domain registry entry.""" + # we call str() on domain to convert it from unicode to ascii + self.domain = dns.name.from_text(str(domain)) + + def _config_win32_search(self, search): + """Configure a Search registry entry.""" + # we call str() on search to convert it from unicode to ascii + search = str(search) + split_char = self._determine_split_char(search) + search_list = search.split(split_char) + for s in search_list: + if not s in self.search: + self.search.append(dns.name.from_text(s)) + + def _config_win32_fromkey(self, key): + """Extract DNS info from a registry key.""" + try: + servers, rtype = _winreg.QueryValueEx(key, 'NameServer') + except WindowsError: + servers = None + if servers: + self._config_win32_nameservers(servers) + try: + dom, rtype = _winreg.QueryValueEx(key, 'Domain') + if dom: + self._config_win32_domain(dom) + except WindowsError: + pass + else: + try: + servers, rtype = _winreg.QueryValueEx(key, 'DhcpNameServer') + except WindowsError: + servers = None + if servers: + self._config_win32_nameservers(servers) + try: + dom, rtype = _winreg.QueryValueEx(key, 'DhcpDomain') + if dom: + self._config_win32_domain(dom) + except WindowsError: + pass + try: + search, rtype = _winreg.QueryValueEx(key, 'SearchList') + except WindowsError: + search = None + if search: + self._config_win32_search(search) + + def read_registry(self): + """Extract resolver configuration from the Windows registry.""" + lm = _winreg.ConnectRegistry(None, _winreg.HKEY_LOCAL_MACHINE) + want_scan = False + try: + try: + # XP, 2000 + tcp_params = _winreg.OpenKey(lm, + r'SYSTEM\CurrentControlSet' + r'\Services\Tcpip\Parameters') + want_scan = True + except EnvironmentError: + # ME + tcp_params = _winreg.OpenKey(lm, + r'SYSTEM\CurrentControlSet' + r'\Services\VxD\MSTCP') + try: + self._config_win32_fromkey(tcp_params) + finally: + tcp_params.Close() + if want_scan: + interfaces = _winreg.OpenKey(lm, + r'SYSTEM\CurrentControlSet' + r'\Services\Tcpip\Parameters' + r'\Interfaces') + try: + i = 0 + while True: + try: + guid = _winreg.EnumKey(interfaces, i) + i += 1 + key = _winreg.OpenKey(interfaces, guid) + if not self._win32_is_nic_enabled(lm, guid, key): + continue + try: + self._config_win32_fromkey(key) + finally: + key.Close() + except EnvironmentError: + break + finally: + interfaces.Close() + finally: + lm.Close() + + def _win32_is_nic_enabled(self, lm, guid, interface_key): + # Look in the Windows Registry to determine whether the network + # interface corresponding to the given guid is enabled. + # + # (Code contributed by Paul Marks, thanks!) + # + try: + # This hard-coded location seems to be consistent, at least + # from Windows 2000 through Vista. + connection_key = _winreg.OpenKey( + lm, + r'SYSTEM\CurrentControlSet\Control\Network' + r'\{4D36E972-E325-11CE-BFC1-08002BE10318}' + r'\%s\Connection' % guid) + + try: + # The PnpInstanceID points to a key inside Enum + (pnp_id, ttype) = _winreg.QueryValueEx( + connection_key, 'PnpInstanceID') + + if ttype != _winreg.REG_SZ: + raise ValueError + + device_key = _winreg.OpenKey( + lm, r'SYSTEM\CurrentControlSet\Enum\%s' % pnp_id) + + try: + # Get ConfigFlags for this device + (flags, ttype) = _winreg.QueryValueEx( + device_key, 'ConfigFlags') + + if ttype != _winreg.REG_DWORD: + raise ValueError + + # Based on experimentation, bit 0x1 indicates that the + # device is disabled. + return not (flags & 0x1) + + finally: + device_key.Close() + finally: + connection_key.Close() + except (EnvironmentError, ValueError): + # Pre-vista, enabled interfaces seem to have a non-empty + # NTEContextList; this was how dnspython detected enabled + # nics before the code above was contributed. We've retained + # the old method since we don't know if the code above works + # on Windows 95/98/ME. + try: + (nte, ttype) = _winreg.QueryValueEx(interface_key, + 'NTEContextList') + return nte is not None + except WindowsError: + return False + + def _compute_timeout(self, start): + now = time.time() + if now < start: + if start - now > 1: + # Time going backwards is bad. Just give up. + raise Timeout + else: + # Time went backwards, but only a little. This can + # happen, e.g. under vmware with older linux kernels. + # Pretend it didn't happen. + now = start + duration = now - start + if duration >= self.lifetime: + raise Timeout + return min(self.lifetime - duration, self.timeout) + + def query(self, qname, rdtype=dns.rdatatype.A, rdclass=dns.rdataclass.IN, + tcp=False, source=None): + """Query nameservers to find the answer to the question. + + The I{qname}, I{rdtype}, and I{rdclass} parameters may be objects + of the appropriate type, or strings that can be converted into objects + of the appropriate type. E.g. For I{rdtype} the integer 2 and the + the string 'NS' both mean to query for records with DNS rdata type NS. + + @param qname: the query name + @type qname: dns.name.Name object or string + @param rdtype: the query type + @type rdtype: int or string + @param rdclass: the query class + @type rdclass: int or string + @param tcp: use TCP to make the query (default is False). + @type tcp: bool + @param source: bind to this IP address (defaults to machine default IP). + @type source: IP address in dotted quad notation + @rtype: dns.resolver.Answer instance + @raises Timeout: no answers could be found in the specified lifetime + @raises NXDOMAIN: the query name does not exist + @raises NoAnswer: the response did not contain an answer + @raises NoNameservers: no non-broken nameservers are available to + answer the question.""" + + if isinstance(qname, (str, unicode)): + qname = dns.name.from_text(qname, None) + if isinstance(rdtype, str): + rdtype = dns.rdatatype.from_text(rdtype) + if isinstance(rdclass, str): + rdclass = dns.rdataclass.from_text(rdclass) + qnames_to_try = [] + if qname.is_absolute(): + qnames_to_try.append(qname) + else: + if len(qname) > 1: + qnames_to_try.append(qname.concatenate(dns.name.root)) + if self.search: + for suffix in self.search: + qnames_to_try.append(qname.concatenate(suffix)) + else: + qnames_to_try.append(qname.concatenate(self.domain)) + all_nxdomain = True + start = time.time() + for qname in qnames_to_try: + if self.cache: + answer = self.cache.get((qname, rdtype, rdclass)) + if answer: + return answer + request = dns.message.make_query(qname, rdtype, rdclass) + if not self.keyname is None: + request.use_tsig(self.keyring, self.keyname, self.keyalgorithm) + request.use_edns(self.edns, self.ednsflags, self.payload) + response = None + # + # make a copy of the servers list so we can alter it later. + # + nameservers = self.nameservers[:] + backoff = 0.10 + while response is None: + if len(nameservers) == 0: + raise NoNameservers + for nameserver in nameservers[:]: + timeout = self._compute_timeout(start) + try: + if tcp: + response = dns.query.tcp(request, nameserver, + timeout, self.port, + source=source) + else: + response = dns.query.udp(request, nameserver, + timeout, self.port, + source=source) + except (socket.error, dns.exception.Timeout): + # + # Communication failure or timeout. Go to the + # next server + # + response = None + continue + except dns.query.UnexpectedSource: + # + # Who knows? Keep going. + # + response = None + continue + except dns.exception.FormError: + # + # We don't understand what this server is + # saying. Take it out of the mix and + # continue. + # + nameservers.remove(nameserver) + response = None + continue + rcode = response.rcode() + if rcode == dns.rcode.NOERROR or \ + rcode == dns.rcode.NXDOMAIN: + break + # + # We got a response, but we're not happy with the + # rcode in it. Remove the server from the mix if + # the rcode isn't SERVFAIL. + # + if rcode != dns.rcode.SERVFAIL: + nameservers.remove(nameserver) + response = None + if not response is None: + break + # + # All nameservers failed! + # + if len(nameservers) > 0: + # + # But we still have servers to try. Sleep a bit + # so we don't pound them! + # + timeout = self._compute_timeout(start) + sleep_time = min(timeout, backoff) + backoff *= 2 + time.sleep(sleep_time) + if response.rcode() == dns.rcode.NXDOMAIN: + continue + all_nxdomain = False + break + if all_nxdomain: + raise NXDOMAIN + answer = Answer(qname, rdtype, rdclass, response) + if self.cache: + self.cache.put((qname, rdtype, rdclass), answer) + return answer + + def use_tsig(self, keyring, keyname=None, + algorithm=dns.tsig.default_algorithm): + """Add a TSIG signature to the query. + + @param keyring: The TSIG keyring to use; defaults to None. + @type keyring: dict + @param keyname: The name of the TSIG key to use; defaults to None. + The key must be defined in the keyring. If a keyring is specified + but a keyname is not, then the key used will be the first key in the + keyring. Note that the order of keys in a dictionary is not defined, + so applications should supply a keyname when a keyring is used, unless + they know the keyring contains only one key. + @param algorithm: The TSIG key algorithm to use. The default + is dns.tsig.default_algorithm. + @type algorithm: string""" + self.keyring = keyring + if keyname is None: + self.keyname = self.keyring.keys()[0] + else: + self.keyname = keyname + self.keyalgorithm = algorithm + + def use_edns(self, edns, ednsflags, payload): + """Configure Edns. + + @param edns: The EDNS level to use. The default is -1, no Edns. + @type edns: int + @param ednsflags: The EDNS flags + @type ednsflags: int + @param payload: The EDNS payload size. The default is 0. + @type payload: int""" + + if edns is None: + edns = -1 + self.edns = edns + self.ednsflags = ednsflags + self.payload = payload + +default_resolver = None + +def get_default_resolver(): + """Get the default resolver, initializing it if necessary.""" + global default_resolver + if default_resolver is None: + default_resolver = Resolver() + return default_resolver + +def query(qname, rdtype=dns.rdatatype.A, rdclass=dns.rdataclass.IN, + tcp=False, source=None): + """Query nameservers to find the answer to the question. + + This is a convenience function that uses the default resolver + object to make the query. + @see: L{dns.resolver.Resolver.query} for more information on the + parameters.""" + return get_default_resolver().query(qname, rdtype, rdclass, tcp, source) + +def zone_for_name(name, rdclass=dns.rdataclass.IN, tcp=False, resolver=None): + """Find the name of the zone which contains the specified name. + + @param name: the query name + @type name: absolute dns.name.Name object or string + @param rdclass: The query class + @type rdclass: int + @param tcp: use TCP to make the query (default is False). + @type tcp: bool + @param resolver: the resolver to use + @type resolver: dns.resolver.Resolver object or None + @rtype: dns.name.Name""" + + if isinstance(name, (str, unicode)): + name = dns.name.from_text(name, dns.name.root) + if resolver is None: + resolver = get_default_resolver() + if not name.is_absolute(): + raise NotAbsolute(name) + while 1: + try: + answer = resolver.query(name, dns.rdatatype.SOA, rdclass, tcp) + return name + except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer): + try: + name = name.parent() + except dns.name.NoParent: + raise NoRootSOA |