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380 lines
13 KiB
380 lines
13 KiB
from __future__ import absolute_import
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import errno
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import warnings
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import hmac
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import socket
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from binascii import hexlify, unhexlify
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from hashlib import md5, sha1, sha256
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from ..exceptions import SSLError, InsecurePlatformWarning, SNIMissingWarning
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from ..packages import six
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SSLContext = None
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HAS_SNI = False
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IS_PYOPENSSL = False
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IS_SECURETRANSPORT = False
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# Maps the length of a digest to a possible hash function producing this digest
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HASHFUNC_MAP = {
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32: md5,
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40: sha1,
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64: sha256,
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}
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def _const_compare_digest_backport(a, b):
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"""
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Compare two digests of equal length in constant time.
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The digests must be of type str/bytes.
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Returns True if the digests match, and False otherwise.
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"""
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result = abs(len(a) - len(b))
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for l, r in zip(bytearray(a), bytearray(b)):
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result |= l ^ r
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return result == 0
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_const_compare_digest = getattr(hmac, 'compare_digest',
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_const_compare_digest_backport)
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try: # Test for SSL features
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import ssl
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from ssl import wrap_socket, CERT_NONE, PROTOCOL_SSLv23
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from ssl import HAS_SNI # Has SNI?
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except ImportError:
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pass
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try:
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from ssl import OP_NO_SSLv2, OP_NO_SSLv3, OP_NO_COMPRESSION
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except ImportError:
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OP_NO_SSLv2, OP_NO_SSLv3 = 0x1000000, 0x2000000
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OP_NO_COMPRESSION = 0x20000
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# Python 2.7 doesn't have inet_pton on non-Linux so we fallback on inet_aton in
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# those cases. This means that we can only detect IPv4 addresses in this case.
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if hasattr(socket, 'inet_pton'):
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inet_pton = socket.inet_pton
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else:
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# Maybe we can use ipaddress if the user has urllib3[secure]?
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try:
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import ipaddress
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def inet_pton(_, host):
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if isinstance(host, bytes):
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host = host.decode('ascii')
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return ipaddress.ip_address(host)
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except ImportError: # Platform-specific: Non-Linux
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def inet_pton(_, host):
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return socket.inet_aton(host)
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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 TLS 1.3 cipher suites
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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 and ChaCha20 over any AES-CBC for better performance and
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# security,
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# - prefer AES-GCM over ChaCha20 because hardware-accelerated AES is common,
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# - disable NULL authentication, MD5 MACs and DSS for security reasons.
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DEFAULT_CIPHERS = ':'.join([
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'TLS13-AES-256-GCM-SHA384',
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'TLS13-CHACHA20-POLY1305-SHA256',
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'TLS13-AES-128-GCM-SHA256',
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'ECDH+AESGCM',
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'ECDH+CHACHA20',
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'DH+AESGCM',
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'DH+CHACHA20',
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'ECDH+AES256',
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'DH+AES256',
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'ECDH+AES128',
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'DH+AES',
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'RSA+AESGCM',
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'RSA+AES',
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'!aNULL',
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'!eNULL',
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'!MD5',
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])
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try:
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from ssl import SSLContext # Modern SSL?
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except ImportError:
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import sys
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class SSLContext(object): # Platform-specific: Python 2
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def __init__(self, protocol_version):
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self.protocol = protocol_version
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# Use default values from a real SSLContext
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self.check_hostname = False
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self.verify_mode = ssl.CERT_NONE
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self.ca_certs = None
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self.options = 0
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self.certfile = None
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self.keyfile = None
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self.ciphers = None
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def load_cert_chain(self, certfile, keyfile):
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self.certfile = certfile
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self.keyfile = keyfile
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def load_verify_locations(self, cafile=None, capath=None):
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self.ca_certs = cafile
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if capath is not None:
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raise SSLError("CA directories not supported in older Pythons")
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def set_ciphers(self, cipher_suite):
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self.ciphers = cipher_suite
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def wrap_socket(self, socket, server_hostname=None, server_side=False):
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warnings.warn(
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'A true SSLContext object is not available. This prevents '
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'urllib3 from configuring SSL appropriately and may cause '
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'certain SSL connections to fail. You can upgrade to a newer '
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'version of Python to solve this. For more information, see '
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'https://urllib3.readthedocs.io/en/latest/advanced-usage.html'
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'#ssl-warnings',
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InsecurePlatformWarning
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)
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kwargs = {
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'keyfile': self.keyfile,
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'certfile': self.certfile,
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'ca_certs': self.ca_certs,
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'cert_reqs': self.verify_mode,
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'ssl_version': self.protocol,
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'server_side': server_side,
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}
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return wrap_socket(socket, ciphers=self.ciphers, **kwargs)
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def assert_fingerprint(cert, fingerprint):
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"""
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Checks if given fingerprint matches the supplied certificate.
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:param cert:
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Certificate as bytes object.
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:param fingerprint:
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Fingerprint as string of hexdigits, can be interspersed by colons.
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"""
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fingerprint = fingerprint.replace(':', '').lower()
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digest_length = len(fingerprint)
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hashfunc = HASHFUNC_MAP.get(digest_length)
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if not hashfunc:
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raise SSLError(
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'Fingerprint of invalid length: {0}'.format(fingerprint))
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# We need encode() here for py32; works on py2 and p33.
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fingerprint_bytes = unhexlify(fingerprint.encode())
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cert_digest = hashfunc(cert).digest()
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if not _const_compare_digest(cert_digest, fingerprint_bytes):
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raise SSLError('Fingerprints did not match. Expected "{0}", got "{1}".'
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.format(fingerprint, hexlify(cert_digest)))
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def resolve_cert_reqs(candidate):
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"""
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Resolves the argument to a numeric constant, which can be passed to
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the wrap_socket function/method from the ssl module.
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Defaults to :data:`ssl.CERT_NONE`.
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If given a string it is assumed to be the name of the constant in the
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:mod:`ssl` module or its abbreviation.
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(So you can specify `REQUIRED` instead of `CERT_REQUIRED`.
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If it's neither `None` nor a string we assume it is already the numeric
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constant which can directly be passed to wrap_socket.
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"""
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if candidate is None:
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return CERT_NONE
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if isinstance(candidate, str):
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res = getattr(ssl, candidate, None)
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if res is None:
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res = getattr(ssl, 'CERT_' + candidate)
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return res
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return candidate
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def resolve_ssl_version(candidate):
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"""
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like resolve_cert_reqs
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"""
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if candidate is None:
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return PROTOCOL_SSLv23
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if isinstance(candidate, str):
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res = getattr(ssl, candidate, None)
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if res is None:
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res = getattr(ssl, 'PROTOCOL_' + candidate)
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return res
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return candidate
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def create_urllib3_context(ssl_version=None, cert_reqs=None,
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options=None, ciphers=None):
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"""All arguments have the same meaning as ``ssl_wrap_socket``.
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By default, this function does a lot of the same work that
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``ssl.create_default_context`` does on Python 3.4+. It:
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- Disables SSLv2, SSLv3, and compression
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- Sets a restricted set of server ciphers
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If you wish to enable SSLv3, you can do::
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from urllib3.util import ssl_
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context = ssl_.create_urllib3_context()
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context.options &= ~ssl_.OP_NO_SSLv3
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You can do the same to enable compression (substituting ``COMPRESSION``
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for ``SSLv3`` in the last line above).
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:param ssl_version:
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The desired protocol version to use. This will default to
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PROTOCOL_SSLv23 which will negotiate the highest protocol that both
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the server and your installation of OpenSSL support.
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:param cert_reqs:
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Whether to require the certificate verification. This defaults to
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``ssl.CERT_REQUIRED``.
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:param options:
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Specific OpenSSL options. These default to ``ssl.OP_NO_SSLv2``,
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``ssl.OP_NO_SSLv3``, ``ssl.OP_NO_COMPRESSION``.
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:param ciphers:
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Which cipher suites to allow the server to select.
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:returns:
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Constructed SSLContext object with specified options
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:rtype: SSLContext
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"""
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context = SSLContext(ssl_version or ssl.PROTOCOL_SSLv23)
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# Setting the default here, as we may have no ssl module on import
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cert_reqs = ssl.CERT_REQUIRED if cert_reqs is None else cert_reqs
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if options is None:
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options = 0
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# SSLv2 is easily broken and is considered harmful and dangerous
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options |= OP_NO_SSLv2
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# SSLv3 has several problems and is now dangerous
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options |= OP_NO_SSLv3
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# Disable compression to prevent CRIME attacks for OpenSSL 1.0+
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# (issue #309)
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options |= OP_NO_COMPRESSION
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context.options |= options
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context.verify_mode = cert_reqs
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if getattr(context, 'check_hostname', None) is not None: # Platform-specific: Python 3.2
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# We do our own verification, including fingerprints and alternative
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# hostnames. So disable it here
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context.check_hostname = False
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return context
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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, ciphers=None, ssl_context=None,
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ca_cert_dir=None):
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"""
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All arguments except for server_hostname, ssl_context, and ca_cert_dir have
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the same meaning as they do when using :func:`ssl.wrap_socket`.
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:param server_hostname:
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When SNI is supported, the expected hostname of the certificate
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:param ssl_context:
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A pre-made :class:`SSLContext` object. If none is provided, one will
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be created using :func:`create_urllib3_context`.
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:param ciphers:
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A string of ciphers we wish the client to support.
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:param ca_cert_dir:
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A directory containing CA certificates in multiple separate files, as
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supported by OpenSSL's -CApath flag or the capath argument to
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SSLContext.load_verify_locations().
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"""
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context = ssl_context
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if context is None:
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# Note: This branch of code and all the variables in it are no longer
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# used by urllib3 itself. We should consider deprecating and removing
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# this code.
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context = create_urllib3_context(ssl_version, cert_reqs,
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ciphers=ciphers)
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if ca_certs or ca_cert_dir:
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try:
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context.load_verify_locations(ca_certs, ca_cert_dir)
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except IOError as e: # Platform-specific: Python 2.7
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raise SSLError(e)
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# Py33 raises FileNotFoundError which subclasses OSError
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# These are not equivalent unless we check the errno attribute
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except OSError as e: # Platform-specific: Python 3.3 and beyond
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if e.errno == errno.ENOENT:
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raise SSLError(e)
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raise
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elif getattr(context, 'load_default_certs', None) is not None:
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# try to load OS default certs; works well on Windows (require Python3.4+)
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context.load_default_certs()
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if certfile:
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context.load_cert_chain(certfile, keyfile)
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# If we detect server_hostname is an IP address then the SNI
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# extension should not be used according to RFC3546 Section 3.1
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# We shouldn't warn the user if SNI isn't available but we would
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# not be using SNI anyways due to IP address for server_hostname.
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if ((server_hostname is not None and not is_ipaddress(server_hostname))
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or IS_SECURETRANSPORT):
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if HAS_SNI and server_hostname is not None:
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return context.wrap_socket(sock, server_hostname=server_hostname)
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warnings.warn(
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'An HTTPS request has been made, but the SNI (Server Name '
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'Indication) extension to TLS is not available on this platform. '
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'This may cause the server to present an incorrect TLS '
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'certificate, which can cause validation failures. You can upgrade to '
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'a newer version of Python to solve this. For more information, see '
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'https://urllib3.readthedocs.io/en/latest/advanced-usage.html'
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'#ssl-warnings',
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SNIMissingWarning
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)
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return context.wrap_socket(sock)
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def is_ipaddress(hostname):
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"""Detects whether the hostname given is an IP address.
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:param str hostname: Hostname to examine.
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:return: True if the hostname is an IP address, False otherwise.
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"""
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if six.PY3 and isinstance(hostname, bytes):
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# IDN A-label bytes are ASCII compatible.
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hostname = hostname.decode('ascii')
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families = [socket.AF_INET]
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if hasattr(socket, 'AF_INET6'):
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families.append(socket.AF_INET6)
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for af in families:
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try:
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inet_pton(af, hostname)
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except (socket.error, ValueError, OSError):
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pass
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else:
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return True
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return False
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