383 lines
12 KiB
Python
383 lines
12 KiB
Python
########################################################################
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# File name: connector.py
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# This file is part of: aioxmpp
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#
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# LICENSE
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Lesser General Public License as
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# published by the Free Software Foundation, either version 3 of the
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# License, or (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this program. If not, see
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# <http://www.gnu.org/licenses/>.
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#
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########################################################################
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"""
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:mod:`~aioxmpp.connector` --- Ways to establish XML streams
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###########################################################
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This module provides classes to establish XML streams. Currently, there are two
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different ways to establish XML streams: normal TCP connection which is then
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upgraded using STARTTLS, and directly using TLS.
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.. versionadded:: 0.6
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The whole module was added in version 0.6.
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Abstract base class
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===================
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The connectors share a common abstract base class, :class:`BaseConnector`:
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.. autoclass:: BaseConnector
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Specific connectors
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===================
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.. autoclass:: STARTTLSConnector
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.. autoclass:: XMPPOverTLSConnector
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"""
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import abc
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import asyncio
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import logging
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from datetime import timedelta
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import aioxmpp.errors as errors
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import aioxmpp.nonza as nonza
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import aioxmpp.protocol as protocol
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import aioxmpp.ssl_transport as ssl_transport
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def to_ascii(s):
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return s.encode("idna").decode("ascii")
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class BaseConnector(metaclass=abc.ABCMeta):
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"""
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This is the base class for connectors. It defines the public interface of
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all connectors.
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.. autoattribute:: tls_supported
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.. automethod:: connect
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Existing connectors:
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.. autosummary::
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STARTTLSConnector
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XMPPOverTLSConnector
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"""
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@abc.abstractproperty
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def tls_supported(self):
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"""
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Boolean which indicates whether TLS is supported by this connector.
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"""
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@abc.abstractproperty
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def dane_supported(self):
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"""
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Boolean which indicates whether DANE is supported by this connector.
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"""
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@abc.abstractmethod
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async def connect(self, loop, metadata, domain, host, port,
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negotiation_timeout,
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base_logger=None):
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"""
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Establish a :class:`.protocol.XMLStream` for `domain` with the given
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`host` at the given TCP `port`.
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`metadata` must be a :class:`.security_layer.SecurityLayer` instance to
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use for the connection. `loop` must be a :class:`asyncio.BaseEventLoop`
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to use.
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`negotiation_timeout` must be the maximum time in seconds to wait for
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the server to reply in each negotiation step. The `negotiation_timeout`
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is used as value for
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:attr:`~aioxmpp.protocol.XMLStream.deadtime_hard_limit` in the returned
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stream.
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Return a triple consisting of the :class:`asyncio.Transport`, the
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:class:`.protocol.XMLStream` and the
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:class:`aioxmpp.nonza.StreamFeatures` of the stream.
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To detect the use of TLS on the stream, check whether
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:meth:`asyncio.Transport.get_extra_info` returns a non-:data:`None`
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value for ``"ssl_object"``.
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`base_logger` is passed to :class:`aioxmpp.protocol.XMLStream`.
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.. versionchanged:: 0.10
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Assignment of
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:attr:`~aioxmpp.protocol.XMLStream.deadtime_hard_limit` was added.
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"""
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class STARTTLSConnector(BaseConnector):
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"""
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Establish an XML stream using STARTTLS.
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.. automethod:: connect
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"""
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@property
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def tls_supported(self):
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return True
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@property
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def dane_supported(self):
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return False
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async def connect(self, loop, metadata, domain: str, host, port,
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negotiation_timeout, base_logger=None):
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"""
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.. seealso::
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:meth:`BaseConnector.connect`
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For general information on the :meth:`connect` method.
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Connect to `host` at TCP port number `port`. The
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:class:`aioxmpp.security_layer.SecurityLayer` object `metadata` is used
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to determine the parameters of the TLS connection.
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First, a normal TCP connection is opened and the stream header is sent.
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The stream features are waited for, and then STARTTLS is negotiated if
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possible.
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:attr:`~.security_layer.SecurityLayer.tls_required` is honoured: if it
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is true and TLS negotiation fails, :class:`~.errors.TLSUnavailable` is
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raised. TLS negotiation is always attempted if
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:attr:`~.security_layer.SecurityLayer.tls_required` is true, even if
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the server does not advertise a STARTTLS stream feature. This might
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help to prevent trivial downgrade attacks, and we don’t have anything
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to lose at this point anymore anyways.
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:attr:`~.security_layer.SecurityLayer.ssl_context_factory` and
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:attr:`~.security_layer.SecurityLayer.certificate_verifier_factory` are
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used to configure the TLS connection.
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.. versionchanged:: 0.10
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The `negotiation_timeout` is set as
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:attr:`~.XMLStream.deadtime_hard_limit` on the returned XML stream.
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"""
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features_future = asyncio.Future(loop=loop)
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stream = protocol.XMLStream(
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to=domain,
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features_future=features_future,
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base_logger=base_logger,
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)
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if base_logger is not None:
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logger = base_logger.getChild(type(self).__name__)
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else:
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logger = logging.getLogger(".".join([
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__name__, type(self).__qualname__,
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]))
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try:
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transport, _ = await ssl_transport.create_starttls_connection(
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loop,
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lambda: stream,
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host=host,
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port=port,
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peer_hostname=host,
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server_hostname=to_ascii(domain),
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use_starttls=True,
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)
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except: # NOQA
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stream.abort()
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raise
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stream.deadtime_hard_limit = timedelta(seconds=negotiation_timeout)
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features = await features_future
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try:
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features[nonza.StartTLSFeature]
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except KeyError:
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if not metadata.tls_required:
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return transport, stream, await features_future
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logger.debug(
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"attempting STARTTLS despite not announced since it is"
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" required")
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try:
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response = await protocol.send_and_wait_for(
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stream,
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[
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nonza.StartTLS(),
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],
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[
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nonza.StartTLSFailure,
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nonza.StartTLSProceed,
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]
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)
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except errors.StreamError:
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raise errors.TLSUnavailable(
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"STARTTLS not supported by server, but required by client"
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)
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if not isinstance(response, nonza.StartTLSProceed):
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if metadata.tls_required:
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message = (
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"server failed to STARTTLS"
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)
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protocol.send_stream_error_and_close(
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stream,
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condition=errors.StreamErrorCondition.POLICY_VIOLATION,
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text=message,
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)
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raise errors.TLSUnavailable(message)
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return transport, stream, await features_future
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verifier = metadata.certificate_verifier_factory()
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await verifier.pre_handshake(
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domain,
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host,
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port,
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metadata,
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)
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ssl_context = metadata.ssl_context_factory()
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verifier.setup_context(ssl_context, transport)
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await stream.starttls(
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ssl_context=ssl_context,
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post_handshake_callback=verifier.post_handshake,
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)
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features = await protocol.reset_stream_and_get_features(
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stream,
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timeout=negotiation_timeout,
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)
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return transport, stream, features
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class XMPPOverTLSConnector(BaseConnector):
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"""
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Establish an XML stream using XMPP-over-TLS, as per :xep:`368`.
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.. automethod:: connect
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"""
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@property
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def dane_supported(self):
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return False
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@property
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def tls_supported(self):
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return True
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def _context_factory_factory(self, logger, metadata, verifier):
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def context_factory(transport):
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ssl_context = metadata.ssl_context_factory()
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if hasattr(ssl_context, "set_alpn_protos"):
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try:
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ssl_context.set_alpn_protos([b'xmpp-client'])
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except NotImplementedError:
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logger.warning(
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"the underlying OpenSSL library does not support ALPN"
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)
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else:
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logger.warning(
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"OpenSSL.SSL.Context lacks set_alpn_protos - "
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"please update pyOpenSSL to a recent version"
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)
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verifier.setup_context(ssl_context, transport)
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return ssl_context
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return context_factory
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async def connect(self, loop, metadata, domain, host, port,
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negotiation_timeout, base_logger=None):
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"""
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.. seealso::
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:meth:`BaseConnector.connect`
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For general information on the :meth:`connect` method.
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Connect to `host` at TCP port number `port`. The
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:class:`aioxmpp.security_layer.SecurityLayer` object `metadata` is used
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to determine the parameters of the TLS connection.
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The connector connects to the server by directly establishing TLS; no
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XML stream is started before TLS negotiation, in accordance to
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:xep:`368` and how legacy SSL was handled in the past.
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:attr:`~.security_layer.SecurityLayer.ssl_context_factory` and
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:attr:`~.security_layer.SecurityLayer.certificate_verifier_factory` are
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used to configure the TLS connection.
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.. versionchanged:: 0.10
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The `negotiation_timeout` is set as
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:attr:`~.XMLStream.deadtime_hard_limit` on the returned XML stream.
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"""
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features_future = asyncio.Future(loop=loop)
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stream = protocol.XMLStream(
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to=domain,
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features_future=features_future,
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base_logger=base_logger,
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)
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if base_logger is not None:
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logger = base_logger.getChild(type(self).__name__)
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else:
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logger = logging.getLogger(".".join([
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__name__, type(self).__qualname__,
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]))
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verifier = metadata.certificate_verifier_factory()
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await verifier.pre_handshake(
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domain,
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host,
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port,
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metadata,
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)
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context_factory = self._context_factory_factory(logger, metadata,
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verifier)
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try:
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transport, _ = await ssl_transport.create_starttls_connection(
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loop,
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lambda: stream,
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host=host,
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port=port,
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peer_hostname=host,
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server_hostname=to_ascii(domain),
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post_handshake_callback=verifier.post_handshake,
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ssl_context_factory=context_factory,
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use_starttls=False,
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)
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except: # NOQA
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stream.abort()
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raise
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stream.deadtime_hard_limit = timedelta(seconds=negotiation_timeout)
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return transport, stream, await features_future
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