456 lines
15 KiB
Python
456 lines
15 KiB
Python
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"""
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SSL with SNI_-support for Python 2. Follow these instructions if you would
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like to verify SSL certificates in Python 2. Note, the default libraries do
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*not* do certificate checking; you need to do additional work to validate
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certificates yourself.
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This needs the following packages installed:
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* pyOpenSSL (tested with 16.0.0)
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* cryptography (minimum 1.3.4, from pyopenssl)
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* idna (minimum 2.0, from cryptography)
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However, pyopenssl depends on cryptography, which depends on idna, so while we
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use all three directly here we end up having relatively few packages required.
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You can install them with the following command:
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pip install pyopenssl cryptography idna
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To activate certificate checking, call
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:func:`~urllib3.contrib.pyopenssl.inject_into_urllib3` from your Python code
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before you begin making HTTP requests. This can be done in a ``sitecustomize``
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module, or at any other time before your application begins using ``urllib3``,
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like this::
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try:
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import urllib3.contrib.pyopenssl
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urllib3.contrib.pyopenssl.inject_into_urllib3()
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except ImportError:
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pass
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Now you can use :mod:`urllib3` as you normally would, and it will support SNI
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when the required modules are installed.
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Activating this module also has the positive side effect of disabling SSL/TLS
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compression in Python 2 (see `CRIME attack`_).
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If you want to configure the default list of supported cipher suites, you can
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set the ``urllib3.contrib.pyopenssl.DEFAULT_SSL_CIPHER_LIST`` variable.
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.. _sni: https://en.wikipedia.org/wiki/Server_Name_Indication
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.. _crime attack: https://en.wikipedia.org/wiki/CRIME_(security_exploit)
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"""
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from __future__ import absolute_import
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import OpenSSL.SSL
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from cryptography import x509
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from cryptography.hazmat.backends.openssl import backend as openssl_backend
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from cryptography.hazmat.backends.openssl.x509 import _Certificate
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from socket import timeout, error as SocketError
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from io import BytesIO
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try: # Platform-specific: Python 2
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from socket import _fileobject
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except ImportError: # Platform-specific: Python 3
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_fileobject = None
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from ..packages.backports.makefile import backport_makefile
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import logging
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import ssl
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from ..packages import six
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import sys
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from .. import util
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__all__ = ['inject_into_urllib3', 'extract_from_urllib3']
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# SNI always works.
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HAS_SNI = True
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# Map from urllib3 to PyOpenSSL compatible parameter-values.
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_openssl_versions = {
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ssl.PROTOCOL_SSLv23: OpenSSL.SSL.SSLv23_METHOD,
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ssl.PROTOCOL_TLSv1: OpenSSL.SSL.TLSv1_METHOD,
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}
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if hasattr(ssl, 'PROTOCOL_TLSv1_1') and hasattr(OpenSSL.SSL, 'TLSv1_1_METHOD'):
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_openssl_versions[ssl.PROTOCOL_TLSv1_1] = OpenSSL.SSL.TLSv1_1_METHOD
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if hasattr(ssl, 'PROTOCOL_TLSv1_2') and hasattr(OpenSSL.SSL, 'TLSv1_2_METHOD'):
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_openssl_versions[ssl.PROTOCOL_TLSv1_2] = OpenSSL.SSL.TLSv1_2_METHOD
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try:
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_openssl_versions.update({ssl.PROTOCOL_SSLv3: OpenSSL.SSL.SSLv3_METHOD})
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except AttributeError:
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pass
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_stdlib_to_openssl_verify = {
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ssl.CERT_NONE: OpenSSL.SSL.VERIFY_NONE,
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ssl.CERT_OPTIONAL: OpenSSL.SSL.VERIFY_PEER,
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ssl.CERT_REQUIRED:
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OpenSSL.SSL.VERIFY_PEER + OpenSSL.SSL.VERIFY_FAIL_IF_NO_PEER_CERT,
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}
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_openssl_to_stdlib_verify = dict(
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(v, k) for k, v in _stdlib_to_openssl_verify.items()
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)
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# OpenSSL will only write 16K at a time
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SSL_WRITE_BLOCKSIZE = 16384
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orig_util_HAS_SNI = util.HAS_SNI
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orig_util_SSLContext = util.ssl_.SSLContext
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log = logging.getLogger(__name__)
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def inject_into_urllib3():
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'Monkey-patch urllib3 with PyOpenSSL-backed SSL-support.'
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_validate_dependencies_met()
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util.ssl_.SSLContext = PyOpenSSLContext
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util.HAS_SNI = HAS_SNI
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util.ssl_.HAS_SNI = HAS_SNI
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util.IS_PYOPENSSL = True
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util.ssl_.IS_PYOPENSSL = True
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def extract_from_urllib3():
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'Undo monkey-patching by :func:`inject_into_urllib3`.'
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util.ssl_.SSLContext = orig_util_SSLContext
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util.HAS_SNI = orig_util_HAS_SNI
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util.ssl_.HAS_SNI = orig_util_HAS_SNI
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util.IS_PYOPENSSL = False
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util.ssl_.IS_PYOPENSSL = False
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def _validate_dependencies_met():
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"""
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Verifies that PyOpenSSL's package-level dependencies have been met.
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Throws `ImportError` if they are not met.
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"""
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# Method added in `cryptography==1.1`; not available in older versions
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from cryptography.x509.extensions import Extensions
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if getattr(Extensions, "get_extension_for_class", None) is None:
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raise ImportError("'cryptography' module missing required functionality. "
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"Try upgrading to v1.3.4 or newer.")
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# pyOpenSSL 0.14 and above use cryptography for OpenSSL bindings. The _x509
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# attribute is only present on those versions.
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from OpenSSL.crypto import X509
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x509 = X509()
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if getattr(x509, "_x509", None) is None:
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raise ImportError("'pyOpenSSL' module missing required functionality. "
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"Try upgrading to v0.14 or newer.")
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def _dnsname_to_stdlib(name):
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"""
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Converts a dNSName SubjectAlternativeName field to the form used by the
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standard library on the given Python version.
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Cryptography produces a dNSName as a unicode string that was idna-decoded
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from ASCII bytes. We need to idna-encode that string to get it back, and
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then on Python 3 we also need to convert to unicode via UTF-8 (the stdlib
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uses PyUnicode_FromStringAndSize on it, which decodes via UTF-8).
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"""
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def idna_encode(name):
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"""
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Borrowed wholesale from the Python Cryptography Project. It turns out
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that we can't just safely call `idna.encode`: it can explode for
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wildcard names. This avoids that problem.
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"""
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import idna
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for prefix in [u'*.', u'.']:
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if name.startswith(prefix):
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name = name[len(prefix):]
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return prefix.encode('ascii') + idna.encode(name)
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return idna.encode(name)
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name = idna_encode(name)
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if sys.version_info >= (3, 0):
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name = name.decode('utf-8')
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return name
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def get_subj_alt_name(peer_cert):
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"""
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Given an PyOpenSSL certificate, provides all the subject alternative names.
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"""
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# Pass the cert to cryptography, which has much better APIs for this.
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if hasattr(peer_cert, "to_cryptography"):
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cert = peer_cert.to_cryptography()
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else:
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# This is technically using private APIs, but should work across all
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# relevant versions before PyOpenSSL got a proper API for this.
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cert = _Certificate(openssl_backend, peer_cert._x509)
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# We want to find the SAN extension. Ask Cryptography to locate it (it's
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# faster than looping in Python)
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try:
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ext = cert.extensions.get_extension_for_class(
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x509.SubjectAlternativeName
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).value
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except x509.ExtensionNotFound:
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# No such extension, return the empty list.
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return []
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except (x509.DuplicateExtension, x509.UnsupportedExtension,
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x509.UnsupportedGeneralNameType, UnicodeError) as e:
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# A problem has been found with the quality of the certificate. Assume
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# no SAN field is present.
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log.warning(
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"A problem was encountered with the certificate that prevented "
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"urllib3 from finding the SubjectAlternativeName field. This can "
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"affect certificate validation. The error was %s",
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e,
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)
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return []
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# We want to return dNSName and iPAddress fields. We need to cast the IPs
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# back to strings because the match_hostname function wants them as
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# strings.
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# Sadly the DNS names need to be idna encoded and then, on Python 3, UTF-8
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# decoded. This is pretty frustrating, but that's what the standard library
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# does with certificates, and so we need to attempt to do the same.
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names = [
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('DNS', _dnsname_to_stdlib(name))
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for name in ext.get_values_for_type(x509.DNSName)
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]
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names.extend(
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('IP Address', str(name))
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for name in ext.get_values_for_type(x509.IPAddress)
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)
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return names
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class WrappedSocket(object):
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'''API-compatibility wrapper for Python OpenSSL's Connection-class.
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Note: _makefile_refs, _drop() and _reuse() are needed for the garbage
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collector of pypy.
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'''
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def __init__(self, connection, socket, suppress_ragged_eofs=True):
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self.connection = connection
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self.socket = socket
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self.suppress_ragged_eofs = suppress_ragged_eofs
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self._makefile_refs = 0
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self._closed = False
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def fileno(self):
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return self.socket.fileno()
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# Copy-pasted from Python 3.5 source code
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def _decref_socketios(self):
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if self._makefile_refs > 0:
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self._makefile_refs -= 1
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if self._closed:
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self.close()
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def recv(self, *args, **kwargs):
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try:
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data = self.connection.recv(*args, **kwargs)
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except OpenSSL.SSL.SysCallError as e:
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if self.suppress_ragged_eofs and e.args == (-1, 'Unexpected EOF'):
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return b''
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else:
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raise SocketError(str(e))
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except OpenSSL.SSL.ZeroReturnError as e:
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if self.connection.get_shutdown() == OpenSSL.SSL.RECEIVED_SHUTDOWN:
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return b''
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else:
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raise
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except OpenSSL.SSL.WantReadError:
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rd = util.wait_for_read(self.socket, self.socket.gettimeout())
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if not rd:
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raise timeout('The read operation timed out')
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else:
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return self.recv(*args, **kwargs)
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else:
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return data
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def recv_into(self, *args, **kwargs):
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try:
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return self.connection.recv_into(*args, **kwargs)
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except OpenSSL.SSL.SysCallError as e:
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if self.suppress_ragged_eofs and e.args == (-1, 'Unexpected EOF'):
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return 0
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else:
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raise SocketError(str(e))
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except OpenSSL.SSL.ZeroReturnError as e:
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if self.connection.get_shutdown() == OpenSSL.SSL.RECEIVED_SHUTDOWN:
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return 0
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else:
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raise
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except OpenSSL.SSL.WantReadError:
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rd = util.wait_for_read(self.socket, self.socket.gettimeout())
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if not rd:
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raise timeout('The read operation timed out')
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else:
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return self.recv_into(*args, **kwargs)
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def settimeout(self, timeout):
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return self.socket.settimeout(timeout)
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def _send_until_done(self, data):
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while True:
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try:
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return self.connection.send(data)
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except OpenSSL.SSL.WantWriteError:
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wr = util.wait_for_write(self.socket, self.socket.gettimeout())
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if not wr:
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raise timeout()
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continue
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except OpenSSL.SSL.SysCallError as e:
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raise SocketError(str(e))
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def sendall(self, data):
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total_sent = 0
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while total_sent < len(data):
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sent = self._send_until_done(data[total_sent:total_sent + SSL_WRITE_BLOCKSIZE])
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total_sent += sent
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def shutdown(self):
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# FIXME rethrow compatible exceptions should we ever use this
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self.connection.shutdown()
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def close(self):
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if self._makefile_refs < 1:
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try:
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self._closed = True
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return self.connection.close()
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except OpenSSL.SSL.Error:
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return
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else:
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self._makefile_refs -= 1
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def getpeercert(self, binary_form=False):
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x509 = self.connection.get_peer_certificate()
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if not x509:
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return x509
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if binary_form:
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return OpenSSL.crypto.dump_certificate(
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OpenSSL.crypto.FILETYPE_ASN1,
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x509)
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return {
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'subject': (
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(('commonName', x509.get_subject().CN),),
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),
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'subjectAltName': get_subj_alt_name(x509)
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}
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def _reuse(self):
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self._makefile_refs += 1
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def _drop(self):
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if self._makefile_refs < 1:
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self.close()
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else:
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self._makefile_refs -= 1
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if _fileobject: # Platform-specific: Python 2
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def makefile(self, mode, bufsize=-1):
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self._makefile_refs += 1
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return _fileobject(self, mode, bufsize, close=True)
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else: # Platform-specific: Python 3
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makefile = backport_makefile
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WrappedSocket.makefile = makefile
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class PyOpenSSLContext(object):
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"""
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I am a wrapper class for the PyOpenSSL ``Context`` object. I am responsible
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for translating the interface of the standard library ``SSLContext`` object
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to calls into PyOpenSSL.
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"""
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def __init__(self, protocol):
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self.protocol = _openssl_versions[protocol]
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self._ctx = OpenSSL.SSL.Context(self.protocol)
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self._options = 0
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self.check_hostname = False
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@property
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def options(self):
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return self._options
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@options.setter
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def options(self, value):
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self._options = value
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self._ctx.set_options(value)
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@property
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def verify_mode(self):
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return _openssl_to_stdlib_verify[self._ctx.get_verify_mode()]
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@verify_mode.setter
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def verify_mode(self, value):
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self._ctx.set_verify(
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_stdlib_to_openssl_verify[value],
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_verify_callback
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)
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def set_default_verify_paths(self):
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self._ctx.set_default_verify_paths()
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def set_ciphers(self, ciphers):
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if isinstance(ciphers, six.text_type):
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ciphers = ciphers.encode('utf-8')
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self._ctx.set_cipher_list(ciphers)
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def load_verify_locations(self, cafile=None, capath=None, cadata=None):
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if cafile is not None:
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cafile = cafile.encode('utf-8')
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if capath is not None:
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capath = capath.encode('utf-8')
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self._ctx.load_verify_locations(cafile, capath)
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if cadata is not None:
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self._ctx.load_verify_locations(BytesIO(cadata))
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def load_cert_chain(self, certfile, keyfile=None, password=None):
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self._ctx.use_certificate_file(certfile)
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if password is not None:
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self._ctx.set_passwd_cb(lambda max_length, prompt_twice, userdata: password)
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self._ctx.use_privatekey_file(keyfile or certfile)
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def wrap_socket(self, sock, server_side=False,
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do_handshake_on_connect=True, suppress_ragged_eofs=True,
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server_hostname=None):
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cnx = OpenSSL.SSL.Connection(self._ctx, sock)
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if isinstance(server_hostname, six.text_type): # Platform-specific: Python 3
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server_hostname = server_hostname.encode('utf-8')
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if server_hostname is not None:
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cnx.set_tlsext_host_name(server_hostname)
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cnx.set_connect_state()
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while True:
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try:
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cnx.do_handshake()
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except OpenSSL.SSL.WantReadError:
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rd = util.wait_for_read(sock, sock.gettimeout())
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if not rd:
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raise timeout('select timed out')
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continue
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except OpenSSL.SSL.Error as e:
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raise ssl.SSLError('bad handshake: %r' % e)
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break
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return WrappedSocket(cnx, sock)
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def _verify_callback(cnx, x509, err_no, err_depth, return_code):
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return err_no == 0
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