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# Copyright 2014-2016 OpenMarket Ltd
# Copyright 2019 New Vector Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import logging
from zope.interface import implementer
from OpenSSL import SSL, crypto
from twisted.internet._sslverify import ClientTLSOptions, _defaultCurveName
from twisted.internet.abstract import isIPAddress, isIPv6Address
from twisted.internet.interfaces import IOpenSSLClientConnectionCreator
from twisted.internet.ssl import CertificateOptions, ContextFactory, platformTrust
from twisted.python.failure import Failure
logger = logging.getLogger(__name__)
class ServerContextFactory(ContextFactory):
"""Factory for PyOpenSSL SSL contexts that are used to handle incoming
connections."""
def __init__(self, config):
self._context = SSL.Context(SSL.SSLv23_METHOD)
self.configure_context(self._context, config)
@staticmethod
def configure_context(context, config):
try:
_ecCurve = crypto.get_elliptic_curve(_defaultCurveName)
context.set_tmp_ecdh(_ecCurve)
except Exception:
logger.exception("Failed to enable elliptic curve for TLS")
context.set_options(SSL.OP_NO_SSLv2 | SSL.OP_NO_SSLv3)
context.use_certificate_chain_file(config.tls_certificate_file)
context.use_privatekey(config.tls_private_key)
# https://hynek.me/articles/hardening-your-web-servers-ssl-ciphers/
context.set_cipher_list(
"ECDH+AESGCM:ECDH+CHACHA20:ECDH+AES256:ECDH+AES128:!aNULL:!SHA1"
)
def getContext(self):
return self._context
def _idnaBytes(text):
"""
Convert some text typed by a human into some ASCII bytes. This is a
copy of twisted.internet._idna._idnaBytes. For documentation, see the
twisted documentation.
"""
try:
import idna
except ImportError:
return text.encode("idna")
else:
return idna.encode(text)
def _tolerateErrors(wrapped):
"""
Wrap up an info_callback for pyOpenSSL so that if something goes wrong
the error is immediately logged and the connection is dropped if possible.
This is a copy of twisted.internet._sslverify._tolerateErrors. For
documentation, see the twisted documentation.
"""
def infoCallback(connection, where, ret):
try:
return wrapped(connection, where, ret)
except: # noqa: E722, taken from the twisted implementation
f = Failure()
logger.exception("Error during info_callback")
connection.get_app_data().failVerification(f)
return infoCallback
@implementer(IOpenSSLClientConnectionCreator)
class ClientTLSOptionsNoVerify(object):
"""
Client creator for TLS without certificate identity verification. This is a
copy of twisted.internet._sslverify.ClientTLSOptions with the identity
verification left out. For documentation, see the twisted documentation.
"""
def __init__(self, hostname, ctx):
self._ctx = ctx
if isIPAddress(hostname) or isIPv6Address(hostname):
self._hostnameBytes = hostname.encode('ascii')
self._sendSNI = False
else:
self._hostnameBytes = _idnaBytes(hostname)
self._sendSNI = True
ctx.set_info_callback(_tolerateErrors(self._identityVerifyingInfoCallback))
def clientConnectionForTLS(self, tlsProtocol):
context = self._ctx
connection = SSL.Connection(context, None)
connection.set_app_data(tlsProtocol)
return connection
def _identityVerifyingInfoCallback(self, connection, where, ret):
# Literal IPv4 and IPv6 addresses are not permitted
# as host names according to the RFCs
if where & SSL.SSL_CB_HANDSHAKE_START and self._sendSNI:
connection.set_tlsext_host_name(self._hostnameBytes)
class ClientTLSOptionsFactory(object):
"""Factory for Twisted ClientTLSOptions that are used to make connections
to remote servers for federation."""
def __init__(self, config):
self._config = config
self._options_noverify = CertificateOptions()
# Check if we're using a custom list of a CA certificates
trust_root = config.federation_ca_trust_root
if trust_root is None:
# Use CA root certs provided by OpenSSL
trust_root = platformTrust()
self._options_verify = CertificateOptions(trustRoot=trust_root)
def get_options(self, host):
# Use _makeContext so that we get a fresh OpenSSL CTX each time.
# Check if certificate verification has been enabled
should_verify = self._config.federation_verify_certificates
# Check if we've disabled certificate verification for this host
if (
should_verify and
host in self._config.federation_certificate_verification_whitelist
):
should_verify = False
if should_verify:
return ClientTLSOptions(host, self._options_verify._makeContext())
return ClientTLSOptionsNoVerify(host, self._options_noverify._makeContext())
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