'''SSL with SNI_-support for Python 2. Follow these instructions if you would
like to verify SSL certificates in Python 2. Note, the default libraries do
*not* do certificate checking; you need to do additional work to validate
certificates yourself.
This needs the following packages installed:
* pyOpenSSL (tested with 0.13)
* ndg-httpsclient (tested with 0.3.2)
* pyasn1 (tested with 0.1.6)
You can install them with the following command:
pip install pyopenssl ndg-httpsclient pyasn1
To activate certificate checking, call
:func:`~urllib3.contrib.pyopenssl.inject_into_urllib3` from your Python code
before you begin making HTTP requests. This can be done in a ``sitecustomize``
module, or at any other time before your application begins using ``urllib3``,
like this::
try:
import urllib3.contrib.pyopenssl
urllib3.contrib.pyopenssl.inject_into_urllib3()
except ImportError:
pass
Now you can use :mod:`urllib3` as you normally would, and it will support SNI
when the required modules are installed.
Activating this module also has the positive side effect of disabling SSL/TLS
encryption in Python 2 (see `CRIME attack`_).
If you want to configure the default list of supported cipher suites, you can
set the ``urllib3.contrib.pyopenssl.DEFAULT_SSL_CIPHER_LIST`` variable.
Module Variables
----------------
:var DEFAULT_SSL_CIPHER_LIST: The list of supported SSL/TLS cipher suites.
Default: ``ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:
ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+3DES:!aNULL:!MD5:!DSS``
.. _sni: https://en.wikipedia.org/wiki/Server_Name_Indication
.. _crime attack: https://en.wikipedia.org/wiki/CRIME_(security_exploit)
'''
try:
from ndg.httpsclient.ssl_peer_verification import SUBJ_ALT_NAME_SUPPORT
from ndg.httpsclient.subj_alt_name import SubjectAltName as BaseSubjectAltName
except SyntaxError as e:
raise ImportError(e)
import OpenSSL.SSL
from pyasn1.codec.der import decoder as der_decoder
from pyasn1.type import univ, constraint
from socket import _fileobject, timeout
import ssl
import select
from .. import connection
from .. import util
__all__ = ['inject_into_urllib3', 'extract_from_urllib3']
# SNI only *really* works if we can read the subjectAltName of certificates.
HAS_SNI = SUBJ_ALT_NAME_SUPPORT
# Map from urllib3 to PyOpenSSL compatible parameter-values.
_openssl_versions = {
ssl.PROTOCOL_SSLv23: OpenSSL.SSL.SSLv23_METHOD,
ssl.PROTOCOL_SSLv3: OpenSSL.SSL.SSLv3_METHOD,
ssl.PROTOCOL_TLSv1: OpenSSL.SSL.TLSv1_METHOD,
}
_openssl_verify = {
ssl.CERT_NONE: OpenSSL.SSL.VERIFY_NONE,
ssl.CERT_OPTIONAL: OpenSSL.SSL.VERIFY_PEER,
ssl.CERT_REQUIRED: OpenSSL.SSL.VERIFY_PEER
+ OpenSSL.SSL.VERIFY_FAIL_IF_NO_PEER_CERT,
}
# A secure default.
# Sources for more information on TLS ciphers:
#
# - https://wiki.mozilla.org/Security/Server_Side_TLS
# - https://www.ssllabs.com/projects/best-practices/index.html
# - https://hynek.me/articles/hardening-your-web-servers-ssl-ciphers/
#
# The general intent is:
# - Prefer cipher suites that offer perfect forward secrecy (DHE/ECDHE),
# - prefer ECDHE over DHE for better performance,
# - prefer any AES-GCM over any AES-CBC for better performance and security,
# - use 3DES as fallback which is secure but slow,
# - disable NULL authentication, MD5 MACs and DSS for security reasons.
DEFAULT_SSL_CIPHER_LIST = "ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:" + \
"ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+3DES:" + \
"!aNULL:!MD5:!DSS"
orig_util_HAS_SNI = util.HAS_SNI
orig_connection_ssl_wrap_socket = connection.ssl_wrap_socket
def inject_into_urllib3():
'Monkey-patch urllib3 with PyOpenSSL-backed SSL-support.'
connection.ssl_wrap_socket = ssl_wrap_socket
util.HAS_SNI = HAS_SNI
def extract_from_urllib3():
'Undo monkey-patching by :func:`inject_into_urllib3`.'
connection.ssl_wrap_socket = orig_connection_ssl_wrap_socket
util.HAS_SNI = orig_util_HAS_SNI
### Note: This is a slightly bug-fixed version of same from ndg-httpsclient.
class SubjectAltName(BaseSubjectAltName):
'''ASN.1 implementation for subjectAltNames support'''
# There is no limit to how many SAN certificates a certificate may have,
# however this needs to have some limit so we'll set an arbitrarily high
# limit.
sizeSpec = univ.SequenceOf.sizeSpec + \
constraint.ValueSizeConstraint(1, 1024)
### Note: This is a slightly bug-fixed version of same from ndg-httpsclient.
def get_subj_alt_name(peer_cert):
# Search through extensions
dns_name = []
if not SUBJ_ALT_NAME_SUPPORT:
return dns_name
general_names = SubjectAltName()
for i in range(peer_cert.get_extension_count()):
ext = peer_cert.get_extension(i)
ext_name = ext.get_short_name()
if ext_name != 'subjectAltName':
continue
# PyOpenSSL returns extension data in ASN.1 encoded form
ext_dat = ext.get_data()
decoded_dat = der_decoder.decode(ext_dat,
asn1Spec=general_names)
for name in decoded_dat:
if not isinstance(name, SubjectAltName):
continue
for entry in range(len(name)):
component = name.getComponentByPosition(entry)
if component.getName() != 'dNSName':
continue
dns_name.append(str(component.getComponent()))
return dns_name
class WrappedSocket(object):
'''API-compatibility wrapper for Python OpenSSL's Connection-class.
Note: _makefile_refs, _drop() and _reuse() are needed for the garbage
collector of pypy.
'''
def __init__(self, connection, socket, suppress_ragged_eofs=True):
self.connection = connection
self.socket = socket
self.suppress_ragged_eofs = suppress_ragged_eofs
self._makefile_refs = 0
def fileno(self):
return self.socket.fileno()
def makefile(self, mode, bufsize=-1):
self._makefile_refs += 1
return _fileobject(self, mode, bufsize, close=True)
def recv(self, *args, **kwargs):
try:
data = self.connection.recv(*args, **kwargs)
except OpenSSL.SSL.SysCallError as e:
if self.suppress_ragged_eofs and e.args == (-1, 'Unexpected EOF'):
return b''
else:
raise
except OpenSSL.SSL.WantReadError:
rd, wd, ed = select.select(
[self.socket], [], [], self.socket.gettimeout())
if not rd:
raise timeout('The read operation timed out')
else:
return self.recv(*args, **kwargs)
else:
return data
def settimeout(self, timeout):
return self.socket.settimeout(timeout)
def sendall(self, data):
return self.connection.sendall(data)
def close(self):
if self._makefile_refs < 1:
return self.connection.shutdown()
else:
self._makefile_refs -= 1
def getpeercert(self, binary_form=False):
x509 = self.connection.get_peer_certificate()
if not x509:
return x509
if binary_form:
return OpenSSL.crypto.dump_certificate(
OpenSSL.crypto.FILETYPE_ASN1,
x509)
return {
'subject': (
(('commonName', x509.get_subject().CN),),
),
'subjectAltName': [
('DNS', value)
for value in get_subj_alt_name(x509)
]
}
def _reuse(self):
self._makefile_refs += 1
def _drop(self):
if self._makefile_refs < 1:
self.close()
else:
self._makefile_refs -= 1
def _verify_callback(cnx, x509, err_no, err_depth, return_code):
return err_no == 0
def ssl_wrap_socket(sock, keyfile=None, certfile=None, cert_reqs=None,
ca_certs=None, server_hostname=None,
ssl_version=None):
ctx = OpenSSL.SSL.Context(_openssl_versions[ssl_version])
if certfile:
ctx.use_certificate_file(certfile)
if keyfile:
ctx.use_privatekey_file(keyfile)
if cert_reqs != ssl.CERT_NONE:
ctx.set_verify(_openssl_verify[cert_reqs], _verify_callback)
if ca_certs:
try:
ctx.load_verify_locations(ca_certs, None)
except OpenSSL.SSL.Error as e:
raise ssl.SSLError('bad ca_certs: %r' % ca_certs, e)
else:
ctx.set_default_verify_paths()
# Disable TLS compression to migitate CRIME attack (issue #309)
OP_NO_COMPRESSION = 0x20000
ctx.set_options(OP_NO_COMPRESSION)
# Set list of supported ciphersuites.
ctx.set_cipher_list(DEFAULT_SSL_CIPHER_LIST)
cnx = OpenSSL.SSL.Connection(ctx, sock)
cnx.set_tlsext_host_name(server_hostname)
cnx.set_connect_state()
while True:
try:
cnx.do_handshake()
except OpenSSL.SSL.WantReadError:
select.select([sock], [], [])
continue
except OpenSSL.SSL.Error as e:
raise ssl.SSLError('bad handshake', e)
break
return WrappedSocket(cnx, sock)