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Editing: asyncresolver.py
# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license # Copyright (C) 2003-2017 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. """Asynchronous DNS stub resolver.""" import socket import time from typing import Any, Dict, List, Optional, Union import dns._ddr import dns.asyncbackend import dns.asyncquery import dns.exception import dns.name import dns.query import dns.rdataclass import dns.rdatatype import dns.resolver # lgtm[py/import-and-import-from] # import some resolver symbols for brevity from dns.resolver import NXDOMAIN, NoAnswer, NoRootSOA, NotAbsolute # for indentation purposes below _udp = dns.asyncquery.udp _tcp = dns.asyncquery.tcp class Resolver(dns.resolver.BaseResolver): """Asynchronous DNS stub resolver.""" async def resolve( self, qname: Union[dns.name.Name, str], rdtype: Union[dns.rdatatype.RdataType, str] = dns.rdatatype.A, rdclass: Union[dns.rdataclass.RdataClass, str] = dns.rdataclass.IN, tcp: bool = False, source: Optional[str] = None, raise_on_no_answer: bool = True, source_port: int = 0, lifetime: Optional[float] = None, search: Optional[bool] = None, backend: Optional[dns.asyncbackend.Backend] = None, ) -> dns.resolver.Answer: """Query nameservers asynchronously to find the answer to the question. *backend*, a ``dns.asyncbackend.Backend``, or ``None``. If ``None``, the default, then dnspython will use the default backend. See :py:func:`dns.resolver.Resolver.resolve()` for the documentation of the other parameters, exceptions, and return type of this method. """ resolution = dns.resolver._Resolution( self, qname, rdtype, rdclass, tcp, raise_on_no_answer, search ) if not backend: backend = dns.asyncbackend.get_default_backend() start = time.time() while True: (request, answer) = resolution.next_request() # Note we need to say "if answer is not None" and not just # "if answer" because answer implements __len__, and python # will call that. We want to return if we have an answer # object, including in cases where its length is 0. if answer is not None: # cache hit! return answer assert request is not None # needed for type checking done = False while not done: (nameserver, tcp, backoff) = resolution.next_nameserver() if backoff: await backend.sleep(backoff) timeout = self._compute_timeout(start, lifetime, resolution.errors) try: response = await nameserver.async_query( request, timeout=timeout, source=source, source_port=source_port, max_size=tcp, backend=backend, ) except Exception as ex: (_, done) = resolution.query_result(None, ex) continue (answer, done) = resolution.query_result(response, None) # Note we need to say "if answer is not None" and not just # "if answer" because answer implements __len__, and python # will call that. We want to return if we have an answer # object, including in cases where its length is 0. if answer is not None: return answer async def resolve_address( self, ipaddr: str, *args: Any, **kwargs: Any ) -> dns.resolver.Answer: """Use an asynchronous resolver to run a reverse query for PTR records. This utilizes the resolve() method to perform a PTR lookup on the specified IP address. *ipaddr*, a ``str``, the IPv4 or IPv6 address you want to get the PTR record for. All other arguments that can be passed to the resolve() function except for rdtype and rdclass are also supported by this function. """ # We make a modified kwargs for type checking happiness, as otherwise # we get a legit warning about possibly having rdtype and rdclass # in the kwargs more than once. modified_kwargs: Dict[str, Any] = {} modified_kwargs.update(kwargs) modified_kwargs["rdtype"] = dns.rdatatype.PTR modified_kwargs["rdclass"] = dns.rdataclass.IN return await self.resolve( dns.reversename.from_address(ipaddr), *args, **modified_kwargs ) async def resolve_name( self, name: Union[dns.name.Name, str], family: int = socket.AF_UNSPEC, **kwargs: Any, ) -> dns.resolver.HostAnswers: """Use an asynchronous resolver to query for address records. This utilizes the resolve() method to perform A and/or AAAA lookups on the specified name. *qname*, a ``dns.name.Name`` or ``str``, the name to resolve. *family*, an ``int``, the address family. If socket.AF_UNSPEC (the default), both A and AAAA records will be retrieved. All other arguments that can be passed to the resolve() function except for rdtype and rdclass are also supported by this function. """ # We make a modified kwargs for type checking happiness, as otherwise # we get a legit warning about possibly having rdtype and rdclass # in the kwargs more than once. modified_kwargs: Dict[str, Any] = {} modified_kwargs.update(kwargs) modified_kwargs.pop("rdtype", None) modified_kwargs["rdclass"] = dns.rdataclass.IN if family == socket.AF_INET: v4 = await self.resolve(name, dns.rdatatype.A, **modified_kwargs) return dns.resolver.HostAnswers.make(v4=v4) elif family == socket.AF_INET6: v6 = await self.resolve(name, dns.rdatatype.AAAA, **modified_kwargs) return dns.resolver.HostAnswers.make(v6=v6) elif family != socket.AF_UNSPEC: raise NotImplementedError(f"unknown address family {family}") raise_on_no_answer = modified_kwargs.pop("raise_on_no_answer", True) lifetime = modified_kwargs.pop("lifetime", None) start = time.time() v6 = await self.resolve( name, dns.rdatatype.AAAA, raise_on_no_answer=False, lifetime=self._compute_timeout(start, lifetime), **modified_kwargs, ) # Note that setting name ensures we query the same name # for A as we did for AAAA. (This is just in case search lists # are active by default in the resolver configuration and # we might be talking to a server that says NXDOMAIN when it # wants to say NOERROR no data. name = v6.qname v4 = await self.resolve( name, dns.rdatatype.A, raise_on_no_answer=False, lifetime=self._compute_timeout(start, lifetime), **modified_kwargs, ) answers = dns.resolver.HostAnswers.make( v6=v6, v4=v4, add_empty=not raise_on_no_answer ) if not answers: raise NoAnswer(response=v6.response) return answers # pylint: disable=redefined-outer-name async def canonical_name(self, name: Union[dns.name.Name, str]) -> dns.name.Name: """Determine the canonical name of *name*. The canonical name is the name the resolver uses for queries after all CNAME and DNAME renamings have been applied. *name*, a ``dns.name.Name`` or ``str``, the query name. This method can raise any exception that ``resolve()`` can raise, other than ``dns.resolver.NoAnswer`` and ``dns.resolver.NXDOMAIN``. Returns a ``dns.name.Name``. """ try: answer = await self.resolve(name, raise_on_no_answer=False) canonical_name = answer.canonical_name except dns.resolver.NXDOMAIN as e: canonical_name = e.canonical_name return canonical_name async def try_ddr(self, lifetime: float = 5.0) -> None: """Try to update the resolver's nameservers using Discovery of Designated Resolvers (DDR). If successful, the resolver will subsequently use DNS-over-HTTPS or DNS-over-TLS for future queries. *lifetime*, a float, is the maximum time to spend attempting DDR. The default is 5 seconds. If the SVCB query is successful and results in a non-empty list of nameservers, then the resolver's nameservers are set to the returned servers in priority order. The current implementation does not use any address hints from the SVCB record, nor does it resolve addresses for the SCVB target name, rather it assumes that the bootstrap nameserver will always be one of the addresses and uses it. A future revision to the code may offer fuller support. The code verifies that the bootstrap nameserver is in the Subject Alternative Name field of the TLS certficate. """ try: expiration = time.time() + lifetime answer = await self.resolve( dns._ddr._local_resolver_name, "svcb", lifetime=lifetime ) timeout = dns.query._remaining(expiration) nameservers = await dns._ddr._get_nameservers_async(answer, timeout) if len(nameservers) > 0: self.nameservers = nameservers except Exception: pass default_resolver = None def get_default_resolver() -> Resolver: """Get the default asynchronous resolver, initializing it if necessary.""" if default_resolver is None: reset_default_resolver() assert default_resolver is not None return default_resolver def reset_default_resolver() -> None: """Re-initialize default asynchronous resolver. Note that the resolver configuration (i.e. /etc/resolv.conf on UNIX systems) will be re-read immediately. """ global default_resolver default_resolver = Resolver() async def resolve( qname: Union[dns.name.Name, str], rdtype: Union[dns.rdatatype.RdataType, str] = dns.rdatatype.A, rdclass: Union[dns.rdataclass.RdataClass, str] = dns.rdataclass.IN, tcp: bool = False, source: Optional[str] = None, raise_on_no_answer: bool = True, source_port: int = 0, lifetime: Optional[float] = None, search: Optional[bool] = None, backend: Optional[dns.asyncbackend.Backend] = None, ) -> dns.resolver.Answer: """Query nameservers asynchronously to find the answer to the question. This is a convenience function that uses the default resolver object to make the query. See :py:func:`dns.asyncresolver.Resolver.resolve` for more information on the parameters. """ return await get_default_resolver().resolve( qname, rdtype, rdclass, tcp, source, raise_on_no_answer, source_port, lifetime, search, backend, ) async def resolve_address( ipaddr: str, *args: Any, **kwargs: Any ) -> dns.resolver.Answer: """Use a resolver to run a reverse query for PTR records. See :py:func:`dns.asyncresolver.Resolver.resolve_address` for more information on the parameters. """ return await get_default_resolver().resolve_address(ipaddr, *args, **kwargs) async def resolve_name( name: Union[dns.name.Name, str], family: int = socket.AF_UNSPEC, **kwargs: Any ) -> dns.resolver.HostAnswers: """Use a resolver to asynchronously query for address records. See :py:func:`dns.asyncresolver.Resolver.resolve_name` for more information on the parameters. """ return await get_default_resolver().resolve_name(name, family, **kwargs) async def canonical_name(name: Union[dns.name.Name, str]) -> dns.name.Name: """Determine the canonical name of *name*. See :py:func:`dns.resolver.Resolver.canonical_name` for more information on the parameters and possible exceptions. """ return await get_default_resolver().canonical_name(name) async def try_ddr(timeout: float = 5.0) -> None: """Try to update the default resolver's nameservers using Discovery of Designated Resolvers (DDR). If successful, the resolver will subsequently use DNS-over-HTTPS or DNS-over-TLS for future queries. See :py:func:`dns.resolver.Resolver.try_ddr` for more information. """ return await get_default_resolver().try_ddr(timeout) async def zone_for_name( name: Union[dns.name.Name, str], rdclass: dns.rdataclass.RdataClass = dns.rdataclass.IN, tcp: bool = False, resolver: Optional[Resolver] = None, backend: Optional[dns.asyncbackend.Backend] = None, ) -> dns.name.Name: """Find the name of the zone which contains the specified name. See :py:func:`dns.resolver.Resolver.zone_for_name` for more information on the parameters and possible exceptions. """ if isinstance(name, str): 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 True: try: answer = await resolver.resolve( name, dns.rdatatype.SOA, rdclass, tcp, backend=backend ) assert answer.rrset is not None if answer.rrset.name == name: return name # otherwise we were CNAMEd or DNAMEd and need to look higher except (NXDOMAIN, NoAnswer): pass try: name = name.parent() except dns.name.NoParent: # pragma: no cover raise NoRootSOA async def make_resolver_at( where: Union[dns.name.Name, str], port: int = 53, family: int = socket.AF_UNSPEC, resolver: Optional[Resolver] = None, ) -> Resolver: """Make a stub resolver using the specified destination as the full resolver. *where*, a ``dns.name.Name`` or ``str`` the domain name or IP address of the full resolver. *port*, an ``int``, the port to use. If not specified, the default is 53. *family*, an ``int``, the address family to use. This parameter is used if *where* is not an address. The default is ``socket.AF_UNSPEC`` in which case the first address returned by ``resolve_name()`` will be used, otherwise the first address of the specified family will be used. *resolver*, a ``dns.asyncresolver.Resolver`` or ``None``, the resolver to use for resolution of hostnames. If not specified, the default resolver will be used. Returns a ``dns.resolver.Resolver`` or raises an exception. """ if resolver is None: resolver = get_default_resolver() nameservers: List[Union[str, dns.nameserver.Nameserver]] = [] if isinstance(where, str) and dns.inet.is_address(where): nameservers.append(dns.nameserver.Do53Nameserver(where, port)) else: answers = await resolver.resolve_name(where, family) for address in answers.addresses(): nameservers.append(dns.nameserver.Do53Nameserver(address, port)) res = dns.asyncresolver.Resolver(configure=False) res.nameservers = nameservers return res async def resolve_at( where: Union[dns.name.Name, str], qname: Union[dns.name.Name, str], rdtype: Union[dns.rdatatype.RdataType, str] = dns.rdatatype.A, rdclass: Union[dns.rdataclass.RdataClass, str] = dns.rdataclass.IN, tcp: bool = False, source: Optional[str] = None, raise_on_no_answer: bool = True, source_port: int = 0, lifetime: Optional[float] = None, search: Optional[bool] = None, backend: Optional[dns.asyncbackend.Backend] = None, port: int = 53, family: int = socket.AF_UNSPEC, resolver: Optional[Resolver] = None, ) -> dns.resolver.Answer: """Query nameservers to find the answer to the question. This is a convenience function that calls ``dns.asyncresolver.make_resolver_at()`` to make a resolver, and then uses it to resolve the query. See ``dns.asyncresolver.Resolver.resolve`` for more information on the resolution parameters, and ``dns.asyncresolver.make_resolver_at`` for information about the resolver parameters *where*, *port*, *family*, and *resolver*. If making more than one query, it is more efficient to call ``dns.asyncresolver.make_resolver_at()`` and then use that resolver for the queries instead of calling ``resolve_at()`` multiple times. """ res = await make_resolver_at(where, port, family, resolver) return await res.resolve( qname, rdtype, rdclass, tcp, source, raise_on_no_answer, source_port, lifetime, search, backend, )
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