304 lines
9.7 KiB
Python
304 lines
9.7 KiB
Python
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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 0.13)
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* ndg-httpsclient (tested with 0.3.2)
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* pyasn1 (tested with 0.1.6)
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You can install them with the following command:
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pip install pyopenssl ndg-httpsclient pyasn1
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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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Module Variables
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----------------
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:var DEFAULT_SSL_CIPHER_LIST: The list of supported SSL/TLS cipher suites.
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Default: ``ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:
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ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+3DES:!aNULL:!MD5:!DSS``
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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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try:
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from ndg.httpsclient.ssl_peer_verification import SUBJ_ALT_NAME_SUPPORT
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from ndg.httpsclient.subj_alt_name import SubjectAltName as BaseSubjectAltName
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except SyntaxError as e:
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raise ImportError(e)
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import OpenSSL.SSL
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from pyasn1.codec.der import decoder as der_decoder
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from pyasn1.type import univ, constraint
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from socket import _fileobject, timeout
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import ssl
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import select
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from .. import connection
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from .. import util
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__all__ = ['inject_into_urllib3', 'extract_from_urllib3']
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# SNI only *really* works if we can read the subjectAltName of certificates.
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HAS_SNI = SUBJ_ALT_NAME_SUPPORT
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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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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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_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: OpenSSL.SSL.VERIFY_PEER
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+ OpenSSL.SSL.VERIFY_FAIL_IF_NO_PEER_CERT,
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}
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# A secure default.
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# Sources for more information on TLS ciphers:
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#
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# - https://wiki.mozilla.org/Security/Server_Side_TLS
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# - https://www.ssllabs.com/projects/best-practices/index.html
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# - https://hynek.me/articles/hardening-your-web-servers-ssl-ciphers/
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#
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# The general intent is:
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# - Prefer cipher suites that offer perfect forward secrecy (DHE/ECDHE),
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# - prefer ECDHE over DHE for better performance,
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# - prefer any AES-GCM over any AES-CBC for better performance and security,
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# - use 3DES as fallback which is secure but slow,
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# - disable NULL authentication, MD5 MACs and DSS for security reasons.
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DEFAULT_SSL_CIPHER_LIST = "ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:" + \
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"ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+3DES:" + \
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"!aNULL:!MD5:!DSS"
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orig_util_HAS_SNI = util.HAS_SNI
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orig_connection_ssl_wrap_socket = connection.ssl_wrap_socket
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def inject_into_urllib3():
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'Monkey-patch urllib3 with PyOpenSSL-backed SSL-support.'
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connection.ssl_wrap_socket = ssl_wrap_socket
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util.HAS_SNI = HAS_SNI
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def extract_from_urllib3():
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'Undo monkey-patching by :func:`inject_into_urllib3`.'
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connection.ssl_wrap_socket = orig_connection_ssl_wrap_socket
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util.HAS_SNI = orig_util_HAS_SNI
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### Note: This is a slightly bug-fixed version of same from ndg-httpsclient.
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class SubjectAltName(BaseSubjectAltName):
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'''ASN.1 implementation for subjectAltNames support'''
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# There is no limit to how many SAN certificates a certificate may have,
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# however this needs to have some limit so we'll set an arbitrarily high
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# limit.
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sizeSpec = univ.SequenceOf.sizeSpec + \
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constraint.ValueSizeConstraint(1, 1024)
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### Note: This is a slightly bug-fixed version of same from ndg-httpsclient.
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def get_subj_alt_name(peer_cert):
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# Search through extensions
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dns_name = []
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if not SUBJ_ALT_NAME_SUPPORT:
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return dns_name
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general_names = SubjectAltName()
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for i in range(peer_cert.get_extension_count()):
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ext = peer_cert.get_extension(i)
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ext_name = ext.get_short_name()
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if ext_name != 'subjectAltName':
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continue
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# PyOpenSSL returns extension data in ASN.1 encoded form
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ext_dat = ext.get_data()
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decoded_dat = der_decoder.decode(ext_dat,
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asn1Spec=general_names)
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for name in decoded_dat:
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if not isinstance(name, SubjectAltName):
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continue
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for entry in range(len(name)):
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component = name.getComponentByPosition(entry)
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if component.getName() != 'dNSName':
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continue
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dns_name.append(str(component.getComponent()))
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return dns_name
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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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def fileno(self):
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return self.socket.fileno()
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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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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
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except OpenSSL.SSL.WantReadError:
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rd, wd, ed = select.select(
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[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 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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_, wlist, _ = select.select([], [self.socket], [],
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self.socket.gettimeout())
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if not wlist:
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raise timeout()
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continue
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def sendall(self, data):
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while len(data):
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sent = self._send_until_done(data)
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data = data[sent:]
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def close(self):
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if self._makefile_refs < 1:
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return self.connection.shutdown()
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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': [
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('DNS', value)
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for value in get_subj_alt_name(x509)
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]
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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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def _verify_callback(cnx, x509, err_no, err_depth, return_code):
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return err_no == 0
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def ssl_wrap_socket(sock, keyfile=None, certfile=None, cert_reqs=None,
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ca_certs=None, server_hostname=None,
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ssl_version=None):
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ctx = OpenSSL.SSL.Context(_openssl_versions[ssl_version])
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if certfile:
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keyfile = keyfile or certfile # Match behaviour of the normal python ssl library
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ctx.use_certificate_file(certfile)
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if keyfile:
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ctx.use_privatekey_file(keyfile)
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if cert_reqs != ssl.CERT_NONE:
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ctx.set_verify(_openssl_verify[cert_reqs], _verify_callback)
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if ca_certs:
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try:
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ctx.load_verify_locations(ca_certs, None)
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except OpenSSL.SSL.Error as e:
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raise ssl.SSLError('bad ca_certs: %r' % ca_certs, e)
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else:
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ctx.set_default_verify_paths()
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# Disable TLS compression to migitate CRIME attack (issue #309)
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OP_NO_COMPRESSION = 0x20000
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ctx.set_options(OP_NO_COMPRESSION)
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# Set list of supported ciphersuites.
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ctx.set_cipher_list(DEFAULT_SSL_CIPHER_LIST)
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cnx = OpenSSL.SSL.Connection(ctx, sock)
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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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select.select([sock], [], [])
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continue
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except OpenSSL.SSL.Error as e:
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raise ssl.SSLError('bad handshake', e)
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break
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return WrappedSocket(cnx, sock)
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