########################################################################
# File name: security_layer.py
# This file is part of: aioxmpp
#
# LICENSE
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this program. If not, see
# <http://www.gnu.org/licenses/>.
#
########################################################################
"""
:mod:`~aioxmpp.security_layer` --- Implementations to negotiate stream security
####################################################################################
This module provides different implementations of the security layer
(TLS+SASL).
These are coupled, as different SASL features might need different TLS features
(such as channel binding or client cert authentication). The preferred method
to construct a :class:`SecurityLayer` is using the :func:`make` function.
:class:`SecurityLayer` objects are needed to establish an XMPP connection,
for example using :class:`aioxmpp.Client`.
.. autofunction:: make
.. autoclass:: PinType
.. autofunction:: tls_with_password_based_authentication(password_provider, [ssl_context_factory], [max_auth_attempts=3])
.. autoclass:: SecurityLayer(ssl_context_factory, certificate_verifier_factory, tls_required, sasl_providers)
.. autofunction:: negotiate_sasl
Certificate verifiers
=====================
To verify the peer certificate provided by the server, different
:class:`CertificateVerifier`\ s are available:
.. autoclass:: PKIXCertificateVerifier
To implement your own verifiers, see the documentation at the base class for
certificate verifiers:
.. autoclass:: CertificateVerifier
Certificate and key pinning
---------------------------
Often in the XMPP world, we need certificate or public key pinning, as most
XMPP servers do not have certificates trusted by the usual certificate
stores. This module also provide certificate verifiers which can be used for
that purpose, as well as stores for saving the pinned information.
.. autoclass:: PinningPKIXCertificateVerifier
.. autoclass:: CertificatePinStore
.. autoclass:: PublicKeyPinStore
Base classes
^^^^^^^^^^^^
For future expansion or customization, the base classes of the above utilities
can be subclassed and extended:
.. autoclass:: HookablePKIXCertificateVerifier
.. autoclass:: AbstractPinStore
.. _sasl providers:
SASL providers
==============
As elements of the `sasl_providers` argument to :class:`SecurityLayer`,
instances of the following classes can be used:
.. autoclass:: PasswordSASLProvider
.. autoclass:: AnonymousSASLProvider
.. note::
Patches welcome for additional :class:`SASLProvider` implementations.
Abstract base classes
=====================
For implementation of custom SASL providers, the following base class can be
used:
.. autoclass:: SASLProvider
Deprecated functionality
========================
In pre-0.6 code, you might find use of the following things:
.. autofunction:: security_layer
.. autoclass:: STARTTLSProvider
""" # NOQA: E501
import abc
import asyncio
import base64
import collections
import enum
import logging
import ssl
import pyasn1
import pyasn1.codec.der.decoder
import pyasn1.codec.der.encoder
import pyasn1_modules.rfc2459
import OpenSSL.SSL
import aiosasl
from . import errors, sasl, nonza, xso, protocol
from .utils import namespaces
logger = logging.getLogger(__name__)
def extract_python_dict_from_x509(x509):
"""
Extract a python dictionary similar to the return value of
:meth:`ssl.SSLSocket.getpeercert` from the given
:class:`OpenSSL.crypto.X509` `x509` object.
Note that by far not all attributes are included; only those required to
use :func:`ssl.match_hostname` are extracted and put in the result.
In the future, more attributes may be added.
"""
result = {
"subject": (
(("commonName", x509.get_subject().commonName),),
)
}
for ext_idx in range(x509.get_extension_count()):
ext = x509.get_extension(ext_idx)
sn = ext.get_short_name()
if sn != b"subjectAltName":
continue
data = pyasn1.codec.der.decoder.decode(
ext.get_data(),
asn1Spec=pyasn1_modules.rfc2459.SubjectAltName())[0]
for name in data:
dNSName = name.getComponentByPosition(2)
if dNSName is None:
continue
if hasattr(dNSName, "isValue") and not dNSName.isValue:
continue
result.setdefault("subjectAltName", []).append(
("DNS", str(dNSName))
)
return result
def extract_blob(x509):
"""
Extract an ASN.1 blob from the given :class:`OpenSSL.crypto.X509`
certificate. Return the resulting :class:`bytes` object.
"""
return OpenSSL.crypto.dump_certificate(
OpenSSL.crypto.FILETYPE_ASN1,
x509)
def blob_to_pyasn1(blob):
"""
Convert an ASN.1 encoded certificate (such as obtained from
:func:`extract_blob`) to a :mod:`pyasn1` structure and return the result.
"""
return pyasn1.codec.der.decoder.decode(
blob,
asn1Spec=pyasn1_modules.rfc2459.Certificate()
)[0]
def extract_pk_blob_from_pyasn1(pyasn1_struct):
"""
Extract an ASN.1 encoded public key blob from the given :mod:`pyasn1`
structure (which must represent a certificate).
"""
pk = pyasn1_struct.getComponentByName(
"tbsCertificate"
).getComponentByName(
"subjectPublicKeyInfo"
)
return pyasn1.codec.der.encoder.encode(pk)
def check_x509_hostname(x509, hostname):
"""
Check whether the given :class:`OpenSSL.crypto.X509` certificate `x509`
matches the given `hostname`.
Return :data:`True` if the name matches and :data:`False` otherwise. This
uses :func:`ssl.match_hostname` and :func:`extract_python_dict_from_x509`.
"""
cert_structure = extract_python_dict_from_x509(x509)
try:
ssl.match_hostname(cert_structure, hostname)
except ssl.CertificateError:
return False
return True
[docs]class CertificateVerifier(metaclass=abc.ABCMeta):
"""
A certificate verifier hooks into the two mechanisms provided by
:class:`aioopenssl.STARTTLSTransport` for certificate verification.
On the one hand, the verify callback provided by
:class:`OpenSSL.SSL.Context` is used and forwarded to
:meth:`verify_callback`. On the other hand, the post handshake coroutine is
set to :meth:`post_handshake`. See the documentation of
:class:`aioopenssl.STARTTLSTransport` for the semantics of that
coroutine.
In addition to these two hooks into the TLS handshake, a third coroutine
which is called before STARTTLS is intiiated is provided.
This baseclass provides a bit of boilerplate.
"""
async def pre_handshake(self, metadata, domain, host, port):
pass
def setup_context(self, ctx, transport):
self.transport = transport
ctx.set_verify(OpenSSL.SSL.VERIFY_PEER, self.verify_callback)
@abc.abstractmethod
def verify_callback(self, conn, x509, errno, errdepth, returncode):
return returncode
@abc.abstractmethod
async def post_handshake(self, transport):
pass
class _NullVerifier(CertificateVerifier):
def setup_context(self, ctx, transport):
self.transport = transport
ctx.set_verify(OpenSSL.SSL.VERIFY_NONE, self.verify_callback)
def verify_callback(self, *args):
return True
async def post_handshake(self, transport):
pass
[docs]class PKIXCertificateVerifier(CertificateVerifier):
"""
This verifier enables the default PKIX based verification of certificates
as implemented by OpenSSL.
The :meth:`verify_callback` checks that the certificate subject matches the
domain name of the JID of the connection.
"""
def verify_callback(self, ctx, x509, errno, errdepth, returncode):
logger.info("verifying certificate (preverify=%s)", returncode)
if not returncode:
logger.warning("certificate verification failed (by OpenSSL)")
return returncode
if errdepth == 0:
hostname = self.transport.get_extra_info("server_hostname")
if not check_x509_hostname(
x509,
hostname):
logger.warning("certificate hostname mismatch "
"(doesn’t match for %r)",
hostname)
return False
return returncode
def setup_context(self, ctx, transport):
super().setup_context(ctx, transport)
ctx.set_default_verify_paths()
async def post_handshake(self, transport):
pass
[docs]class HookablePKIXCertificateVerifier(CertificateVerifier):
"""
This PKIX-based verifier has several hooks which allow overriding of the
checking process, for example to implement key or certificate pinning.
It provides three callbacks:
* `quick_check` is a synchronous callback (and must be a plain function)
which is called from :meth:`verify_callback`. It is only called if the
certificate fails full PKIX verification, and only for certain cases. For
example, expired certificates do not get a second chance and are rejected
immediately.
It is called with the leaf certificate as its only argument. It must
return :data:`True` if the certificate is known good and should pass the
verification. If the certificate is known bad and should fail the
verification immediately, it must return :data:`False`.
If the certificate is unknown and the check should be deferred to the
`post_handshake_deferred_failure` callback, :data:`None` must be
returned.
Passing :data:`None` to `quick_check` is the same as if a callable passed
to `quick_check` would return :data:`None` always (i.e. the decision is
deferred).
* `post_handshake_deferred_failure` must be a coroutine. It is called after
the handshake is done but before the STARTTLS negotiation has finished
and allows the application to take more time to decide on a certificate
and possibly request user input.
The coroutine receives the verifier instance as its argument and can make
use of all the verification attributes to present the user with a
sensible choice.
If `post_handshake_deferred_failure` is :data:`None`, the result is
identical to returning :data:`False` from the callback.
* `post_handshake_success` is only called if the certificate has passed the
verification (either because it flawlessly passed by OpenSSL or the
`quick_check` callback returned :data:`True`).
You may pass :data:`None` to this argument to disable the callback
without any further side effects.
The following attributes are available when the post handshake callbacks
are called:
.. attribute:: recorded_errors
This is a :class:`set` with tuples consisting of a
:class:`OpenSSL.crypto.X509` instance, an OpenSSL error number and the
depth of the certificate in the verification chain (0 is the leaf
certificate).
It is a collection of all errors which were passed into
:meth:`verify_callback` by OpenSSL.
.. attribute:: hostname_matches
This is :data:`True` if the host name in the leaf certificate matches
the domain part of the JID for which we are connecting (i.e. the usual
server name check).
.. attribute:: leaf_x509
The :class:`OpenSSL.crypto.X509` object which represents the leaf
certificate.
"""
# these are the errors for which we allow pinning the certificate
_DEFERRABLE_ERRORS = {
(20, None), # issuer certificate not available locally
(19, None), # self-signed cert in chain
(18, 0), # depth-zero self-signed cert
(27, 0), # cert untrusted
(21, 0), # leaf certificate not signed ...
}
def __init__(self,
quick_check,
post_handshake_deferred_failure,
post_handshake_success):
self._quick_check = quick_check
self._post_handshake_success = post_handshake_success
self._post_handshake_deferred_failure = post_handshake_deferred_failure
self.recorded_errors = set()
self.deferred = True
self.hostname_matches = False
self.leaf_x509 = None
def verify_callback(self, ctx, x509, errno, depth, preverify):
if errno != 0 and errno != 21:
self.recorded_errors.add((x509, errno, depth))
return True
if depth == 0:
if errno != 0:
logger.debug(
"unsigned certificate; this is odd to say the least"
)
self.recorded_errors.add((x509, errno, depth))
hostname = self.transport.get_extra_info("server_hostname")
self.hostname_matches = check_x509_hostname(x509, hostname)
self.leaf_x509 = x509
return self.verify_recorded(x509, self.recorded_errors)
return True
def verify_recorded(self, leaf_x509, records):
self.deferred = False
if not records:
return True
hostname = self.transport.get_extra_info("server_hostname")
self.hostname_matches = check_x509_hostname(leaf_x509, hostname)
for x509, errno, depth in records:
if ((errno, depth) not in self._DEFERRABLE_ERRORS and
(errno, None) not in self._DEFERRABLE_ERRORS):
logger.warning("non-deferrable certificate error: "
"depth=%d, errno=%d",
depth, errno)
return False
if self._quick_check is not None:
result = self._quick_check(leaf_x509)
logger.debug("certificate quick-check returned %r", result)
else:
result = None
logger.debug("no certificate quick-check")
if result is None:
self.deferred = True
return result is not False
async def post_handshake(self, transport):
if self.deferred:
if self._post_handshake_deferred_failure is not None:
result = await self._post_handshake_deferred_failure(self)
else:
result = False
if not result:
raise errors.TLSFailure("certificate verification failed")
else:
if self._post_handshake_success is not None:
await self._post_handshake_success()
[docs]class AbstractPinStore(metaclass=abc.ABCMeta):
"""
This is the abstract base class for both :class:`PublicKeyPinStore` and
:class:`CerificatePinStore`. The interface for both types of pinning is
identical; the only difference is in which information is stored.
.. automethod:: pin
.. automethod:: query
.. automethod:: get_pinned_for_host
.. automethod:: export_to_json
.. automethod:: import_from_json
For subclasses:
.. automethod:: _encode_key
.. automethod:: _decode_key
.. automethod:: _x509_key
"""
def __init__(self):
self._storage = {}
[docs] @abc.abstractmethod
def _x509_key(self, key):
"""
Return a hashable value which identifies the given `x509` certificate
for the purposes of the key store. See the implementations
:meth:`PublicKeyPinStore._x509_key` and
:meth:`CertificatePinStore._x509_key` for details on what is stored for
the respective subclasses.
This method is abstract and must be implemented in subclasses.
"""
[docs] def _encode_key(self, key):
"""
Encode the `key` (which has previously been obtained from
:meth:`_x509_key`) into a string which is both JSON compatible and can
be used as XML text (which means that it must not contain control
characters, for example).
The method is called by :meth:`export_to_json`. The default
implementation returns `key`.
"""
return key
[docs] def _decode_key(self, obj):
"""
Decode the `obj` into a key which is compatible to the values returned
by :meth:`_x509_key`.
The method is called by :meth:`import_from_json`. The default
implementation returns `obj`.
"""
return obj
[docs] def pin(self, hostname, x509):
"""
Pin an :class:`OpenSSL.crypto.X509` object `x509` for use with the
given `hostname`. Which information exactly is used to identify the
certificate depends :meth:`_x509_key`.
"""
key = self._x509_key(x509)
self._storage.setdefault(hostname, set()).add(key)
[docs] def query(self, hostname, x509):
"""
Return true if the given :class:`OpenSSL.crypto.X509` object `x509` has
previously been pinned for use with the given `hostname` and
:data:`None` otherwise.
Returning :data:`None` allows this method to be used with
:class:`PinningPKIXCertificateVerifier`.
"""
key = self._x509_key(x509)
try:
pins = self._storage[hostname]
except KeyError:
return None
if key in pins:
return True
return None
[docs] def get_pinned_for_host(self, hostname):
"""
Return the set of hashable values which are used to identify the X.509
certificates which are accepted for the given `hostname`.
If no values have previously been pinned, this returns the empty set.
"""
try:
return frozenset(self._storage[hostname])
except KeyError:
return frozenset()
[docs] def export_to_json(self):
"""
Return a JSON dictionary which contains all the pins stored in this
store.
"""
return {
hostname: sorted(self._encode_key(key) for key in pins)
for hostname, pins in self._storage.items()
}
[docs] def import_from_json(self, data, *, override=False):
"""
Import a JSON dictionary which must have the same format as exported by
:meth:`export`.
If *override* is true, the existing data in the pin store will be
overridden with the data from `data`. Otherwise, the `data` will be
merged into the store.
"""
if override:
self._storage = {
hostname: set(self._decode_key(key) for key in pins)
for hostname, pins in data.items()
}
return
for hostname, pins in data.items():
existing_pins = self._storage.setdefault(hostname, set())
existing_pins.update(self._decode_key(key) for key in pins)
[docs]class PublicKeyPinStore(AbstractPinStore):
"""
This pin store stores the public keys of the X.509 objects which are passed
to its :meth:`pin` method.
"""
def _x509_key(self, x509):
blob = extract_blob(x509)
pyasn1_struct = blob_to_pyasn1(blob)
return extract_pk_blob_from_pyasn1(pyasn1_struct)
def _encode_key(self, key):
return base64.b64encode(key).decode("ascii")
def _decode_key(self, obj):
return base64.b64decode(obj.encode("ascii"))
[docs]class CertificatePinStore(AbstractPinStore):
"""
This pin store stores the whole certificates which are passed to its
:meth:`pin` method.
"""
def _x509_key(self, x509):
return extract_blob(x509)
def _encode_key(self, key):
return base64.b64encode(key).decode("ascii")
def _decode_key(self, obj):
return base64.b64decode(obj.encode("ascii"))
[docs]class PinningPKIXCertificateVerifier(HookablePKIXCertificateVerifier):
"""
The :class:`PinningPKIXCertificateVerifier` is a subclass of the
:class:`HookablePKIXCertificateVerifier` which uses the hooks to implement
certificate or public key pinning.
It does not store the pins itself. Instead, the user must pass a callable
to the `query_pin` argument. That callable will be called with two
arguments: the `servername` and the `x509`. The `x509` is a
:class:`OpenSSL.crypto.X509` instance, which is the leaf certificate which
attempts to identify the host. The `servername` is the name of the server
we try to connect to (the identifying name, like the domain part of the
JID). The callable must return :data:`True` (to accept the certificate),
:data:`False` (to reject the certificate) or :data:`None` (to defer the
decision to the `post_handshake_deferred_failure` callback). `query_pin`
must not block; if it needs to do blocking operations, it should defer.
The other two arguments are coroutines with semantics identical to those of
the same-named arguments in :class:`HookablePKIXCertificateVerifier`.
.. seealso::
:meth:`AbstractPinStore.query` is a method which can be passed as
`query_pin` callback.
"""
def __init__(self,
query_pin,
post_handshake_deferred_failure,
post_handshake_success=None):
super().__init__(
self._quick_check_query_pin,
post_handshake_deferred_failure,
post_handshake_success
)
self._query_pin = query_pin
def _quick_check_query_pin(self, leaf_x509):
hostname = self.transport.get_extra_info("server_hostname")
is_pinned = self._query_pin(hostname, leaf_x509)
if not is_pinned:
logger.debug(
"certificate for %r does not appear in pin store",
hostname,
)
return is_pinned
class ErrorRecordingVerifier(CertificateVerifier):
def __init__(self):
super().__init__()
self._errors = []
def _record_verify_info(self, x509, errno, depth):
self._errors.append((x509, errno, depth))
def verify_callback(self, x509, errno, depth, returncode):
self._record_verify_info(x509, errno, depth)
return True
async def post_handshake(self, transport):
if self._errors:
raise errors.TLSFailure(
"Peer certificate verification failure: {}".format(
", ".join(map(str, self._errors))))
class SASLMechanism(xso.XSO):
TAG = (namespaces.sasl, "mechanism")
name = xso.Text()
def __init__(self, name=None):
super().__init__()
self.name = name
@nonza.StreamFeatures.as_feature_class
class SASLMechanisms(xso.XSO):
TAG = (namespaces.sasl, "mechanisms")
mechanisms = xso.ChildList([SASLMechanism])
def get_mechanism_list(self):
return [
mechanism.name
for mechanism in self.mechanisms
]
[docs]class SASLProvider:
"""
Base class to implement a SASL provider.
SASL providers are used in :class:`SecurityLayer` to authenticate the local
user with a service. The credentials required depend on the specific SASL
provider, and it is recommended to acquire means to get these credentials
via constructor parameters (see for example :class:`PasswordSASLProvider`).
The following methods must be implemented by subclasses:
.. automethod:: execute
The following methods are intended to be re-used by subclasses:
.. automethod:: _execute
.. automethod:: _find_supported
"""
[docs] def _find_supported(self, features, mechanism_classes):
"""
Find the first mechanism class which supports a mechanism announced in
the given stream features.
:param features: Current XMPP stream features
:type features: :class:`~.nonza.StreamFeatures`
:param mechanism_classes: SASL mechanism classes to use
:type mechanism_classes: iterable of :class:`SASLMechanism`
sub\\ *classes*
:raises aioxmpp.errors.SASLUnavailable: if the peer does not announce
SASL support
:return: the :class:`SASLMechanism` subclass to use and a token
:rtype: pair
Return a supported SASL mechanism class, by looking the given
stream features `features`.
If no matching mechanism is found, ``(None, None)`` is
returned. Otherwise, a pair consisting of the mechanism class and the
value returned by the respective
:meth:`~.sasl.SASLMechanism.any_supported` method is returned. The
latter is an opaque token which must be passed to the `token` argument
of :meth:`_execute` or :meth:`aiosasl.SASLMechanism.authenticate`.
"""
try:
mechanisms = features[SASLMechanisms]
except KeyError:
logger.error("No sasl mechanisms: %r", list(features))
raise errors.SASLUnavailable(
"Remote side does not support SASL") from None
remote_mechanism_list = mechanisms.get_mechanism_list()
for our_mechanism in mechanism_classes:
token = our_mechanism.any_supported(remote_mechanism_list)
if token is not None:
return our_mechanism, token
return None, None
AUTHENTICATION_FAILURES = {
"credentials-expired",
"account-disabled",
"invalid-authzid",
"not-authorized",
"temporary-auth-failure",
}
MECHANISM_REJECTED_FAILURES = {
"invalid-mechanism",
"mechanism-too-weak",
"encryption-required",
}
[docs] async def _execute(self, intf, mechanism, token):
"""
Execute a SASL authentication process.
:param intf: SASL interface to use
:type intf: :class:`~.sasl.SASLXMPPInterface`
:param mechanism: SASL mechanism to use
:type mechanism: :class:`aiosasl.SASLMechanism`
:param token: The opaque token argument for the mechanism
:type token: not :data:`None`
:raises aiosasl.AuthenticationFailure: if authentication failed due to
bad credentials
:raises aiosasl.SASLFailure: on other SASL error conditions (such as
protocol violations)
:return: true if authentication succeeded, false if the mechanism has
to be disabled
:rtype: :class:`bool`
This executes the SASL authentication process. The more specific
exceptions are generated by inspecting the
:attr:`aiosasl.SASLFailure.opaque_error` on exceptinos raised from the
:class:`~.sasl.SASLXMPPInterface`. Other :class:`aiosasl.SASLFailure`
exceptions are re-raised without modification.
"""
sm = aiosasl.SASLStateMachine(intf)
try:
await mechanism.authenticate(sm, token)
return True
except aiosasl.SASLFailure as err:
if err.opaque_error in self.AUTHENTICATION_FAILURES:
raise aiosasl.AuthenticationFailure(
opaque_error=err.opaque_error,
text=err.text)
elif err.opaque_error in self.MECHANISM_REJECTED_FAILURES:
return False
raise
[docs] @abc.abstractmethod
async def execute(self, client_jid, features, xmlstream, tls_transport):
"""
Perform SASL negotiation.
:param client_jid: The JID the client attempts to authenticate for
:type client_jid: :class:`aioxmpp.JID`
:param features: Current stream features nonza
:type features: :class:`~.nonza.StreamFeatures`
:param xmlstream: The XML stream to authenticate over
:type xmlstream: :class:`~.protocol.XMLStream`
:param tls_transport: The TLS transport or :data:`None` if no TLS has
been negotiated
:type tls_transport: :class:`asyncio.Transport` or :data:`None`
:raise aiosasl.AuthenticationFailure: if authentication failed due to
bad credentials
:raise aiosasl.SASLFailure: on other SASL-related errors
:return: true if the negotiation was successful, false if no common
mechanisms could be found or all mechanisms failed for reasons
unrelated to the credentials themselves.
:rtype: :class:`bool`
The implementation depends on the specific :class:`SASLProvider`
subclass in use.
This coroutine returns :data:`True` if the negotiation was
successful. If no common mechanisms could be found, :data:`False` is
returned. This is useful to chain several SASL providers (e.g. a
provider supporting ``EXTERNAL`` in front of password-based providers).
Any other error case, such as no SASL support on the remote side or
authentication failure results in an :class:`aiosasl.SASLFailure`
exception to be raised.
"""
[docs]class PasswordSASLProvider(SASLProvider):
"""
Perform password-based SASL authentication.
:param password_provider: A coroutine function returning the password to
authenticate with.
:type password_provider: coroutine function
:param max_auth_attempts: Maximum number of authentication attempts with a
single mechanism.
:type max_auth_attempts: positive :class:`int`
`password_provider` must be a coroutine taking two arguments, a JID and an
integer number. The first argument is the JID which is trying to
authenticate and the second argument is the number of the authentication
attempt, starting at 0. On each attempt, the number is increased, up to
`max_auth_attempts`\\ -1. If the coroutine returns :data:`None`, the
authentication process is aborted. If the number of attempts are exceeded,
the authentication process is also aborted. In both cases, an
:class:`aiosasl.AuthenticationFailure` error will be raised.
The SASL mechanisms used depend on whether TLS has been negotiated
successfully before. In any case, :class:`aiosasl.SCRAM` is used. If TLS
has been negotiated, :class:`aiosasl.PLAIN` is also supported.
.. seealso::
:class:`SASLProvider`
for the public interface of this class.
"""
def __init__(self, password_provider, *,
max_auth_attempts=3, **kwargs):
super().__init__(**kwargs)
self._password_provider = password_provider
self._max_auth_attempts = max_auth_attempts
async def execute(self, client_jid, features, xmlstream, tls_transport):
client_jid = client_jid.bare()
password_signalled_abort = False
nattempt = 0
cached_credentials = None
async def credential_provider():
nonlocal password_signalled_abort, nattempt, cached_credentials
if cached_credentials is not None:
return client_jid.localpart, cached_credentials
password = await self._password_provider(client_jid, nattempt)
if password is None:
password_signalled_abort = True
raise aiosasl.AuthenticationFailure(
"user intervention",
text="authentication aborted by user")
cached_credentials = password
return client_jid.localpart, password
classes = [
aiosasl.SCRAM
]
if tls_transport is not None:
classes.append(aiosasl.PLAIN)
intf = sasl.SASLXMPPInterface(xmlstream)
while classes:
# go over all mechanisms available. some errors disable a mechanism
# (like encryption-required or mechansim-too-weak)
mechanism_class, token = self._find_supported(features, classes)
if mechanism_class is None:
return False
mechanism = mechanism_class(credential_provider)
last_auth_error = None
for nattempt in range(self._max_auth_attempts):
try:
mechanism_worked = await self._execute(
intf, mechanism, token)
except (ValueError, aiosasl.AuthenticationFailure) as err:
if password_signalled_abort:
# immediately re-raise
raise
last_auth_error = err
# allow the user to re-try
cached_credentials = None
continue
else:
break
else:
raise last_auth_error
if mechanism_worked:
return True
classes.remove(mechanism_class)
return False
[docs]class AnonymousSASLProvider(SASLProvider):
"""
Perform the ``ANONYMOUS`` SASL mechanism (:rfc:`4505`).
:param token: The trace token for the ``ANONYMOUS`` mechanism
:type token: :class:`str`
`token` SHOULD be the empty string in the XMPP context (see :xep:`175`).
.. seealso::
:class:`SASLProvider`
for the public interface of this class.
.. warning::
Take the security and privacy considerations from :rfc:`4505` (which
specifies the ANONYMOUS SASL mechanism) and :xep:`175` (which discusses
the ANONYMOUS SASL mechanism in the XMPP context) into account before
using this provider.
.. note::
This class requires :class:`aiosasl.ANONYMOUS`, which is available with
:mod:`aiosasl` 0.3 or newer. If :class:`aiosasl.ANONYMOUS` is not
provided, this class is replaced with :data:`None`.
.. versionadded:: 0.8
"""
def __init__(self, token):
super().__init__()
self._token = token
async def execute(self, client_jid, features, xmlstream, tls_transport):
mechanism_class, token = self._find_supported(
features,
[aiosasl.ANONYMOUS]
)
if mechanism_class is None:
return False
intf = sasl.SASLXMPPInterface(xmlstream)
mechanism = aiosasl.ANONYMOUS(self._token)
return await self._execute(
intf,
mechanism,
token,
)
if not hasattr(aiosasl, "ANONYMOUS"):
AnonymousSASLProvider = None # NOQA
[docs]class SecurityLayer(collections.namedtuple(
"SecurityLayer",
[
"ssl_context_factory",
"certificate_verifier_factory",
"tls_required",
"sasl_providers",
])):
"""
A security layer defines the security properties used for an XML stream.
This includes TLS settings and SASL providers. The arguments are used to
initialise the attributes of the same name.
:class:`SecurityLayer` instances are required to construct a
:class:`aioxmpp.Client`.
.. versionadded:: 0.6
.. seealso::
:func:`make`
A powerful function which can be used to create a configured
:class:`SecurityLayer` instance.
.. attribute:: ssl_context_factory
This is a callable returning a :class:`OpenSSL.SSL.Context` instance
which is to be used for any SSL operations for the connection.
The :class:`OpenSSL.SSL.Context` instances should not be reused between
connection attempts, as the certificate verifiers may set options which
cannot be disabled anymore.
.. attribute:: certificate_verifier_factory
This is a callable which returns a fresh
:class:`CertificateVerifier` on each call (it must be a fresh instance
since :class:`CertificateVerifier` objects are allowed to keep state and
:class:`SecurityLayer` objects are reusable between connection
attempts).
.. attribute:: tls_required
A boolean which indicates whether TLS is required. If it is set to true,
connectors (see :mod:`aioxmpp.connector`) will abort the connection if
TLS (or something equivalent) is not available on the transport.
.. note::
Disabling this makes your application vulnerable to STARTTLS
stripping attacks.
.. attribute:: sasl_providers
A sequence of :class:`SASLProvider` instances. As SASL providers are
stateless, it is not necessary to create new providers for each
connection.
"""
def default_verify_callback(conn, x509, errno, errdepth, returncode):
return errno == 0
def default_ssl_context():
"""
Return a sensibly configured :class:`OpenSSL.SSL.Context` context.
The context has SSLv2 and SSLv3 disabled, and supports TLS 1.0+ (depending
on the version of the SSL library).
Tries to negotiate an XMPP c2s connection via ALPN (:rfc:`7301`).
"""
ctx = OpenSSL.SSL.Context(OpenSSL.SSL.SSLv23_METHOD)
ctx.set_options(OpenSSL.SSL.OP_NO_SSLv2 | OpenSSL.SSL.OP_NO_SSLv3)
ctx.set_verify(OpenSSL.SSL.VERIFY_PEER, default_verify_callback)
return ctx
[docs]async def negotiate_sasl(transport, xmlstream,
sasl_providers,
negotiation_timeout,
jid, features):
"""
Perform SASL authentication on the given :class:`.protocol.XMLStream`
`stream`. `transport` must be the :class:`asyncio.Transport` over which the
`stream` runs. It is used to detect whether TLS is used and may be required
by some SASL mechanisms.
`sasl_providers` must be an iterable of :class:`SASLProvider` objects. They
will be tried in iteration order to authenticate against the server. If one
of the `sasl_providers` fails with a :class:`aiosasl.AuthenticationFailure`
exception, the other providers are still tried; only if all providers fail,
the last :class:`aiosasl.AuthenticationFailure` exception is re-raised.
If no mechanism was able to authenticate but not due to authentication
failures (other failures include no matching mechanism on the server side),
:class:`aiosasl.SASLUnavailable` is raised.
Return the :class:`.nonza.StreamFeatures` obtained after resetting the
stream after successful SASL authentication.
.. versionadded:: 0.6
.. deprecated:: 0.10
The `negotiation_timeout` argument is ignored. The timeout is
controlled using the :attr:`~.XMLStream.deadtime_hard_limit` timeout
of the stream.
The argument will be removed in version 1.0. To prepare for this,
please pass `jid` and `features` as keyword arguments.
"""
if not transport.get_extra_info("sslcontext"):
transport = None
last_auth_error = None
for sasl_provider in sasl_providers:
try:
result = await sasl_provider.execute(
jid, features, xmlstream, transport)
except ValueError as err:
raise errors.StreamNegotiationFailure(
"invalid credentials: {}".format(err)
) from err
except aiosasl.AuthenticationFailure as err:
last_auth_error = err
continue
if result:
features = await protocol.reset_stream_and_get_features(
xmlstream
)
break
else:
if last_auth_error:
raise last_auth_error
else:
raise errors.SASLUnavailable("No common mechanisms")
return features
[docs]class STARTTLSProvider:
"""
.. deprecated:: 0.6
Do **not** use this. This is a shim class which provides
backward-compatibility for versions older than 0.6.
"""
def __init__(self, ssl_context_factory,
certificate_verifier_factory=PKIXCertificateVerifier,
*,
require_starttls=True):
self.ssl_context_factory = ssl_context_factory
self.certificate_verifier_factory = certificate_verifier_factory
self.tls_required = require_starttls
[docs]def security_layer(tls_provider, sasl_providers):
"""
.. deprecated:: 0.6
Replaced by :class:`SecurityLayer`.
Return a configured :class:`SecurityLayer`. `tls_provider` must be a
:class:`STARTTLSProvider`.
The return value can be passed to the constructor of
:class:`~.node.Client`.
Some very basic checking on the input is also performed.
"""
sasl_providers = tuple(sasl_providers)
if not sasl_providers:
raise ValueError("At least one SASL provider must be given.")
for sasl_provider in sasl_providers:
sasl_provider.execute # check that sasl_provider has execute method
result = SecurityLayer(
tls_provider.ssl_context_factory,
tls_provider.certificate_verifier_factory,
tls_provider.tls_required,
sasl_providers
)
return result
[docs]def tls_with_password_based_authentication(
password_provider,
ssl_context_factory=default_ssl_context,
max_auth_attempts=3,
certificate_verifier_factory=PKIXCertificateVerifier):
"""
Produce a commonly used :class:`SecurityLayer`, which uses TLS and
password-based SASL authentication. If `ssl_context_factory` is not
provided, an SSL context with TLSv1+ is used.
`password_provider` must be a coroutine which is called with the jid
as first and the number of attempt as second argument. It must return the
password to us, or :data:`None` to abort.
Return a :class:`SecurityLayer` instance.
.. deprecated:: 0.7
Use :func:`make` instead.
"""
tls_kwargs = {}
if certificate_verifier_factory is not None:
tls_kwargs["certificate_verifier_factory"] = \
certificate_verifier_factory
return SecurityLayer(
ssl_context_factory,
certificate_verifier_factory,
True,
(
PasswordSASLProvider(
password_provider,
max_auth_attempts=max_auth_attempts),
)
)
[docs]class PinType(enum.Enum):
"""
Enumeration to control which pinning is used by :meth:`make`.
.. attribute:: PUBLIC_KEY
Public keys are stored in the pin store. :class:`PublicKeyPinStore` is
used.
.. attribute:: CERTIFICATE
Whole certificates are stored in the pin store.
:class:`CertificatePinStore` is used.
"""
PUBLIC_KEY = 0
CERTIFICATE = 1
[docs]def make(
password_provider,
*,
pin_store=None,
pin_type=PinType.PUBLIC_KEY,
post_handshake_deferred_failure=None,
anonymous=False,
ssl_context_factory=default_ssl_context,
no_verify=False):
"""
Construct a :class:`SecurityLayer`. Depending on the arguments passed,
different features are enabled or disabled.
.. warning::
When using any argument except `password_provider`, be sure to read
its documentation below the following overview **carefully**. Many
arguments can be used to shoot yourself in the foot easily, while
violating all security expectations.
Args:
password_provider (:class:`str` or coroutine function):
Password source to authenticate with.
Keyword Args:
pin_store (:class:`dict` or :class:`AbstractPinStore`):
Enable use of certificate/public key pinning. `pin_type` controls
the type of store used when a dict is passed instead of a pin store
object.
pin_type (:class:`~aioxmpp.security_layer.PinType`):
Type of pin store to create when `pin_store` is a dict.
post_handshake_deferred_failure (coroutine function):
Coroutine callback to invoke when using certificate pinning and the
verification of the certificate was not possible using either PKIX
or the pin store.
anonymous (:class:`str`, :data:`None` or :data:`False`):
trace token for SASL ANONYMOUS (:rfc:`4505`); passing a
non-:data:`False` value enables ANONYMOUS authentication.
ssl_context_factory (function): Factory function to create the SSL
context used to establish transport layer security. Defaults to
:func:`aioxmpp.security_layer.default_ssl_context`.
no_verify (:class:`bool`): *Disable* all certificate verification.
Usage is **strongly discouraged** outside controlled test
environments. See below for alternatives.
Raises:
RuntimeError: if `anonymous` is not :data:`False` and the version of
:mod:`aiosasl` does not support ANONYMOUS authentication.
Returns:
:class:`SecurityLayer`: object holding the entire security layer
configuration
`password_provider` must either be a coroutine function or a :class:`str`.
As a coroutine function, it is called during authentication with the JID we
are trying to authenticate against as the first, and the sequence number of
the authentication attempt as second argument. The sequence number starts
at 0. The coroutine is expected to return :data:`None` or a password. See
:class:`PasswordSASLProvider` for details. If `password_provider` is a
:class:`str`, a coroutine which returns the string on the first and
:data:`None` on subsequent attempts is created and used.
If `pin_store` is not :data:`None`, :class:`PinningPKIXCertificateVerifier`
is used instead of the default :class:`PKIXCertificateVerifier`. The
`pin_store` argument determines the pinned certificates: if it is a
dictionary, a :class:`AbstractPinStore` according to the :class:`PinType`
passed as `pin_type` argument is created and initialised with the data from
the dictionary using its :meth:`~AbstractPinStore.import_from_json` method.
Otherwise, `pin_store` must be a :class:`AbstractPinStore` instance which
is passed to the verifier.
`post_handshake_deferred_callback` is used only if `pin_store` is not
:data:`None`. It is passed to the equally-named argument of
:class:`PinningPKIXCertificateVerifier`, see the documentation there for
details on the semantics. If `post_handshake_deferred_callback` is
:data:`None` while `pin_store` is not, a coroutine which returns
:data:`False` is substituted.
`ssl_context_factory` can be a callable taking no arguments and returning
a :class:`OpenSSL.SSL.Context` object. If given, the factory will be used
to obtain an SSL context when the stream negotiates transport layer
security via TLS. By default,
:func:`aioxmpp.security_layer.default_ssl_context` is used, which should be
fine for most applications.
.. warning::
The :func:`~.default_ssl_context` implementation sets important
defaults. It is **strongly recommended** to use the context returned
by :func:`~.default_ssl_context` and modify it, instead of creating
a new context from scratch when implementing your own factory.
If `no_verify` is true, none of the above regarding certificate verifiers
matters. The internal null verifier is used, which **disables certificate
verification completely**.
.. warning::
Disabling certificate verification makes your application vulnerable to
trivial Man-in-the-Middle attacks. Do **not** use this outside
controlled test environments or when you know **exactly** what you’re
doing!
If you need to handle certificates which cannot be verified using the
public key infrastructure, consider making use of the `pin_store`
argument instead.
`anonymous` may be a string or :data:`False`. If it is not :data:`False`,
:class:`AnonymousSASLProvider` is used before password based authentication
is attempted. In addition, it is allowed to set `password_provider` to
:data:`None`. `anonymous` is the trace token to use, and SHOULD be the
empty string (as specified by :xep:`175`). This requires :mod:`aiosasl` 0.3
or newer.
.. note::
:data:`False` and ``""`` are treated differently for the `anonymous`
argument, despite both being false-y values!
.. note::
If `anonymous` is not :data:`False` and `password_provider` is not
:data:`None`, both authentication types are attempted. Anonymous
authentication is, in that case, preferred over password-based
authentication.
If you need to reverse the order, you have to construct your own
:class:`SecurityLayer` object.
.. warning::
Take the security and privacy considerations from :rfc:`4505` (which
specifies the ANONYMOUS SASL mechanism) and :xep:`175` (which discusses
the ANONYMOUS SASL mechanism in the XMPP context) into account before
using `anonymous`.
The versatility and simplicity of use of this function make (pun intended)
it the preferred way to construct :class:`SecurityLayer` instances.
.. versionadded:: 0.8
Support for SASL ANONYMOUS was added.
.. versionadded:: 0.11
Support for `ssl_context_factory`.
"""
if isinstance(password_provider, str):
static_password = password_provider
async def password_provider(jid, nattempt):
if nattempt == 0:
return static_password
return None
if pin_store is not None:
if post_handshake_deferred_failure is None:
async def post_handshake_deferred_failure(verifier):
return False
if not isinstance(pin_store, AbstractPinStore):
pin_data = pin_store
if pin_type == PinType.PUBLIC_KEY:
logger.debug("using PublicKeyPinStore")
pin_store = PublicKeyPinStore()
else:
logger.debug("using CertificatePinStore")
pin_store = CertificatePinStore()
pin_store.import_from_json(pin_data)
def certificate_verifier_factory():
return PinningPKIXCertificateVerifier(
pin_store.query,
post_handshake_deferred_failure,
)
elif no_verify:
certificate_verifier_factory = _NullVerifier
else:
certificate_verifier_factory = PKIXCertificateVerifier
sasl_providers = []
if anonymous is not False:
if AnonymousSASLProvider is None:
raise RuntimeError(
"aiosasl does not support ANONYMOUS, please upgrade"
)
sasl_providers.append(
AnonymousSASLProvider(anonymous)
)
if password_provider is not None:
sasl_providers.append(
PasswordSASLProvider(
password_provider,
),
)
return SecurityLayer(
ssl_context_factory,
certificate_verifier_factory,
True,
tuple(sasl_providers),
)