from __future__ import absolute_import
import hmac
import os
import sys
import warnings
from binascii import hexlify, unhexlify
from hashlib import md5, sha1, sha256
from ..exceptions import (
InsecurePlatformWarning,
ProxySchemeUnsupported,
SNIMissingWarning,
SSLError,
)
from ..packages import six
from .url import BRACELESS_IPV6_ADDRZ_RE, IPV4_RE
SSLContext = None
SSLTransport = None
HAS_SNI = False
IS_PYOPENSSL = False
IS_SECURETRANSPORT = False
ALPN_PROTOCOLS = ["http/1.1"]
# Maps the length of a digest to a possible hash function producing this digest
HASHFUNC_MAP = {32: md5, 40: sha1, 64: sha256}
def _const_compare_digest_backport(a, b):
"""
Compare two digests of equal length in constant time.
The digests must be of type str/bytes.
Returns True if the digests match, and False otherwise.
"""
result = abs(len(a) - len(b))
for left, right in zip(bytearray(a), bytearray(b)):
result |= left ^ right
return result == 0
_const_compare_digest = getattr(hmac, "compare_digest", _const_compare_digest_backport)
try: # Test for SSL features
import ssl
from ssl import CERT_REQUIRED, wrap_socket
except ImportError:
pass
try:
from ssl import HAS_SNI # Has SNI?
except ImportError:
pass
try:
from .ssltransport import SSLTransport
except ImportError:
pass
try: # Platform-specific: Python 3.6
from ssl import PROTOCOL_TLS
PROTOCOL_SSLv23 = PROTOCOL_TLS
except ImportError:
try:
from ssl import PROTOCOL_SSLv23 as PROTOCOL_TLS
PROTOCOL_SSLv23 = PROTOCOL_TLS
except ImportError:
PROTOCOL_SSLv23 = PROTOCOL_TLS = 2
try:
from ssl import PROTOCOL_TLS_CLIENT
except ImportError:
PROTOCOL_TLS_CLIENT = PROTOCOL_TLS
try:
from ssl import OP_NO_COMPRESSION, OP_NO_SSLv2, OP_NO_SSLv3
except ImportError:
OP_NO_SSLv2, OP_NO_SSLv3 = 0x1000000, 0x2000000
OP_NO_COMPRESSION = 0x20000
try: # OP_NO_TICKET was added in Python 3.6
from ssl import OP_NO_TICKET
except ImportError:
OP_NO_TICKET = 0x4000
# 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 and ChaCha20 over any AES-CBC for better performance and
# security,
# - prefer AES-GCM over ChaCha20 because hardware-accelerated AES is common,
# - disable NULL authentication, MD5 MACs, DSS, and other
# insecure ciphers for security reasons.
# - NOTE: TLS 1.3 cipher suites are managed through a different interface
# not exposed by CPython (yet!) and are enabled by default if they're available.
DEFAULT_CIPHERS = ":".join(
[
"ECDHE+AESGCM",
"ECDHE+CHACHA20",
"DHE+AESGCM",
"DHE+CHACHA20",
"ECDH+AESGCM",
"DH+AESGCM",
"ECDH+AES",
"DH+AES",
"RSA+AESGCM",
"RSA+AES",
"!aNULL",
"!eNULL",
"!MD5",
"!DSS",
]
)
try:
from ssl import SSLContext # Modern SSL?
except ImportError:
class SSLContext(object): # Platform-specific: Python 2
def __init__(self, protocol_version):
self.protocol = protocol_version
# Use default values from a real SSLContext
self.check_hostname = False
self.verify_mode = ssl.CERT_NONE
self.ca_certs = None
self.options = 0
self.certfile = None
self.keyfile = None
self.ciphers = None
def load_cert_chain(self, certfile, keyfile):
self.certfile = certfile
self.keyfile = keyfile
def load_verify_locations(self, cafile=None, capath=None, cadata=None):
self.ca_certs = cafile
if capath is not None:
raise SSLError("CA directories not supported in older Pythons")
if cadata is not None:
raise SSLError("CA data not supported in older Pythons")
def set_ciphers(self, cipher_suite):
self.ciphers = cipher_suite
def wrap_socket(self, socket, server_hostname=None, server_side=False):
warnings.warn(
"A true SSLContext object is not available. This prevents "
"urllib3 from configuring SSL appropriately and may cause "
"certain SSL connections to fail. You can upgrade to a newer "
"version of Python to solve this. For more information, see "
"https://urllib3.readthedocs.io/en/1.26.x/advanced-usage.html"
"#ssl-warnings",
InsecurePlatformWarning,
)
kwargs = {
"keyfile": self.keyfile,
"certfile": self.certfile,
"ca_certs": self.ca_certs,
"cert_reqs": self.verify_mode,
"ssl_version": self.protocol,
"server_side": server_side,
}
return wrap_socket(socket, ciphers=self.ciphers, **kwargs)
def assert_fingerprint(cert, fingerprint):
"""
Checks if given fingerprint matches the supplied certificate.
:param cert:
Certificate as bytes object.
:param fingerprint:
Fingerprint as string of hexdigits, can be interspersed by colons.
"""
fingerprint = fingerprint.replace(":", "").lower()
digest_length = len(fingerprint)
hashfunc = HASHFUNC_MAP.get(digest_length)
if not hashfunc:
raise SSLError("Fingerprint of invalid length: {0}".format(fingerprint))
# We need encode() here for py32; works on py2 and p33.
fingerprint_bytes = unhexlify(fingerprint.encode())
cert_digest = hashfunc(cert).digest()
if not _const_compare_digest(cert_digest, fingerprint_bytes):
raise SSLError(
'Fingerprints did not match. Expected "{0}", got "{1}".'.format(
fingerprint, hexlify(cert_digest)
)
)
def resolve_cert_reqs(candidate):
"""
Resolves the argument to a numeric constant, which can be passed to
the wrap_socket function/method from the ssl module.
Defaults to :data:`ssl.CERT_REQUIRED`.
If given a string it is assumed to be the name of the constant in the
:mod:`ssl` module or its abbreviation.
(So you can specify `REQUIRED` instead of `CERT_REQUIRED`.
If it's neither `None` nor a string we assume it is already the numeric
constant which can directly be passed to wrap_socket.
"""
if candidate is None:
return CERT_REQUIRED
if isinstance(candidate, str):
res = getattr(ssl, candidate, None)
if res is None:
res = getattr(ssl, "CERT_" + candidate)
return res
return candidate
def resolve_ssl_version(candidate):
"""
like resolve_cert_reqs
"""
if candidate is None:
return PROTOCOL_TLS
if isinstance(candidate, str):
res = getattr(ssl, candidate, None)
if res is None:
res = getattr(ssl, "PROTOCOL_" + candidate)
return res
return candidate
def create_urllib3_context(
ssl_version=None, cert_reqs=None, options=None, ciphers=None
):
"""All arguments have the same meaning as ``ssl_wrap_socket``.
By default, this function does a lot of the same work that
``ssl.create_default_context`` does on Python 3.4+. It:
- Disables SSLv2, SSLv3, and compression
- Sets a restricted set of server ciphers
If you wish to enable SSLv3, you can do::
from urllib3.util import ssl_
context = ssl_.create_urllib3_context()
context.options &= ~ssl_.OP_NO_SSLv3
You can do the same to enable compression (substituting ``COMPRESSION``
for ``SSLv3`` in the last line above).
:param ssl_version:
The desired protocol version to use. This will default to
PROTOCOL_SSLv23 which will negotiate the highest protocol that both
the server and your installation of OpenSSL support.
:param cert_reqs:
Whether to require the certificate verification. This defaults to
``ssl.CERT_REQUIRED``.
:param options:
Specific OpenSSL options. These default to ``ssl.OP_NO_SSLv2``,
``ssl.OP_NO_SSLv3``, ``ssl.OP_NO_COMPRESSION``, and ``ssl.OP_NO_TICKET``.
:param ciphers:
Which cipher suites to allow the server to select.
:returns:
Constructed SSLContext object with specified options
:rtype: SSLContext
"""
# PROTOCOL_TLS is deprecated in Python 3.10
if not ssl_version or ssl_version == PROTOCOL_TLS:
ssl_version = PROTOCOL_TLS_CLIENT
context = SSLContext(ssl_version)
context.set_ciphers(ciphers or DEFAULT_CIPHERS)
# Setting the default here, as we may have no ssl module on import
cert_reqs = ssl.CERT_REQUIRED if cert_reqs is None else cert_reqs
if options is None:
options = 0
# SSLv2 is easily broken and is considered harmful and dangerous
options |= OP_NO_SSLv2
# SSLv3 has several problems and is now dangerous
options |= OP_NO_SSLv3
# Disable compression to prevent CRIME attacks for OpenSSL 1.0+
# (issue #309)
options |= OP_NO_COMPRESSION
# TLSv1.2 only. Unless set explicitly, do not request tickets.
# This may save some bandwidth on wire, and although the ticket is encrypted,
# there is a risk associated with it being on wire,
# if the server is not rotating its ticketing keys properly.
options |= OP_NO_TICKET
context.options |= options
# Enable post-handshake authentication for TLS 1.3, see GH #1634. PHA is
# necessary for conditional client cert authentication with TLS 1.3.
# The attribute is None for OpenSSL <= 1.1.0 or does not exist in older
# versions of Python. We only enable on Python 3.7.4+ or if certificate
# verification is enabled to work around Python issue #37428
# See: https://bugs.python.org/issue37428
if (cert_reqs == ssl.CERT_REQUIRED or sys.version_info >= (3, 7, 4)) and getattr(
context, "post_handshake_auth", None
) is not None:
context.post_handshake_auth = True
def disable_check_hostname():
if (
getattr(context, "check_hostname", None) is not None
): # Platform-specific: Python 3.2
# We do our own verification, including fingerprints and alternative
# hostnames. So disable it here
context.check_hostname = False
# The order of the below lines setting verify_mode and check_hostname
# matter due to safe-guards SSLContext has to prevent an SSLContext with
# check_hostname=True, verify_mode=NONE/OPTIONAL. This is made even more
# complex because we don't know whether PROTOCOL_TLS_CLIENT will be used
# or not so we don't know the initial state of the freshly created SSLContext.
if cert_reqs == ssl.CERT_REQUIRED:
context.verify_mode = cert_reqs
disable_check_hostname()
else:
disable_check_hostname()
context.verify_mode = cert_reqs
# Enable logging of TLS session keys via defacto standard environment variable
# 'SSLKEYLOGFILE', if the feature is available (Python 3.8+). Skip empty values.
if hasattr(context, "keylog_filename"):
sslkeylogfile = os.environ.get("SSLKEYLOGFILE")
if sslkeylogfile:
context.keylog_filename = sslkeylogfile
return context
def ssl_wrap_socket(
sock,
keyfile=None,
certfile=None,
cert_reqs=None,
ca_certs=None,
server_hostname=None,
ssl_version=None,
ciphers=None,
ssl_context=None,
ca_cert_dir=None,
key_password=None,
ca_cert_data=None,
tls_in_tls=False,
):
"""
All arguments except for server_hostname, ssl_context, and ca_cert_dir have
the same meaning as they do when using :func:`ssl.wrap_socket`.
:param server_hostname:
When SNI is supported, the expected hostname of the certificate
:param ssl_context:
A pre-made :class:`SSLContext` object. If none is provided, one will
be created using :func:`create_urllib3_context`.
:param ciphers:
A string of ciphers we wish the client to support.
:param ca_cert_dir:
A directory containing CA certificates in multiple separate files, as
supported by OpenSSL's -CApath flag or the capath argument to
SSLContext.load_verify_locations().
:param key_password:
Optional password if the keyfile is encrypted.
:param ca_cert_data:
Optional string containing CA certificates in PEM format suitable for
passing as the cadata parameter to SSLContext.load_verify_locations()
:param tls_in_tls:
Use SSLTransport to wrap the existing socket.
"""
context = ssl_context
if context is None:
# Note: This branch of code and all the variables in it are no longer
# used by urllib3 itself. We should consider deprecating and removing
# this code.
context = create_urllib3_context(ssl_version, cert_reqs, ciphers=ciphers)
if ca_certs or ca_cert_dir or ca_cert_data:
try:
context.load_verify_locations(ca_certs, ca_cert_dir, ca_cert_data)
except (IOError, OSError) as e:
raise SSLError(e)
elif ssl_context is None and hasattr(context, "load_default_certs"):
# try to load OS default certs; works well on Windows (require Python3.4+)
context.load_default_certs()
# Attempt to detect if we get the goofy behavior of the
# keyfile being encrypted and OpenSSL asking for the
# passphrase via the terminal and instead error out.
if keyfile and key_password is None and _is_key_file_encrypted(keyfile):
raise SSLError("Client private key is encrypted, password is required")
if certfile:
if key_password is None:
context.load_cert_chain(certfile, keyfile)
else:
context.load_cert_chain(certfile, keyfile, key_password)
try:
if hasattr(context, "set_alpn_protocols"):
context.set_alpn_protocols(ALPN_PROTOCOLS)
except NotImplementedError: # Defensive: in CI, we always have set_alpn_protocols
pass
# If we detect server_hostname is an IP address then the SNI
# extension should not be used according to RFC3546 Section 3.1
use_sni_hostname = server_hostname and not is_ipaddress(server_hostname)
# SecureTransport uses server_hostname in certificate verification.
send_sni = (use_sni_hostname and HAS_SNI) or (
IS_SECURETRANSPORT and server_hostname
)
# Do not warn the user if server_hostname is an invalid SNI hostname.
if not HAS_SNI and use_sni_hostname:
warnings.warn(
"An HTTPS request has been made, but the SNI (Server Name "
"Indication) extension to TLS is not available on this platform. "
"This may cause the server to present an incorrect TLS "
"certificate, which can cause validation failures. You can upgrade to "
"a newer version of Python to solve this. For more information, see "
"https://urllib3.readthedocs.io/en/1.26.x/advanced-usage.html"
"#ssl-warnings",
SNIMissingWarning,
)
if send_sni:
ssl_sock = _ssl_wrap_socket_impl(
sock, context, tls_in_tls, server_hostname=server_hostname
)
else:
ssl_sock = _ssl_wrap_socket_impl(sock, context, tls_in_tls)
return ssl_sock
def is_ipaddress(hostname):
"""Detects whether the hostname given is an IPv4 or IPv6 address.
Also detects IPv6 addresses with Zone IDs.
:param str hostname: Hostname to examine.
:return: True if the hostname is an IP address, False otherwise.
"""
if not six.PY2 and isinstance(hostname, bytes):
# IDN A-label bytes are ASCII compatible.
hostname = hostname.decode("ascii")
return bool(IPV4_RE.match(hostname) or BRACELESS_IPV6_ADDRZ_RE.match(hostname))
def _is_key_file_encrypted(key_file):
"""Detects if a key file is encrypted or not."""
with open(key_file, "r") as f:
for line in f:
# Look for Proc-Type: 4,ENCRYPTED
if "ENCRYPTED" in line:
return True
return False
def _ssl_wrap_socket_impl(sock, ssl_context, tls_in_tls, server_hostname=None):
if tls_in_tls:
if not SSLTransport:
# Import error, ssl is not available.
raise ProxySchemeUnsupported(
"TLS in TLS requires support for the 'ssl' module"
)
SSLTransport._validate_ssl_context_for_tls_in_tls(ssl_context)
return SSLTransport(sock, ssl_context, server_hostname)
if server_hostname:
return ssl_context.wrap_socket(sock, server_hostname=server_hostname)
else:
return ssl_context.wrap_socket(sock)