475 lines
16 KiB
Python
475 lines
16 KiB
Python
from __future__ import absolute_import
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import hmac
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import os
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import sys
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import warnings
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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 (
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InsecurePlatformWarning,
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ProxySchemeUnsupported,
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SNIMissingWarning,
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SSLError,
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)
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from ..packages import six
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from .url import BRACELESS_IPV6_ADDRZ_RE, IPV4_RE
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SSLContext = None
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SSLTransport = 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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ALPN_PROTOCOLS = ["http/1.1"]
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# Maps the length of a digest to a possible hash function producing this digest
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HASHFUNC_MAP = {32: md5, 40: sha1, 64: sha256}
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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 left, right in zip(bytearray(a), bytearray(b)):
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result |= left ^ right
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return result == 0
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_const_compare_digest = getattr(hmac, "compare_digest", _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 CERT_REQUIRED, wrap_socket
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except ImportError:
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pass
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try:
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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 .ssltransport import SSLTransport
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except ImportError:
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pass
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try: # Platform-specific: Python 3.6
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from ssl import PROTOCOL_TLS
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PROTOCOL_SSLv23 = PROTOCOL_TLS
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except ImportError:
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try:
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from ssl import PROTOCOL_SSLv23 as PROTOCOL_TLS
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PROTOCOL_SSLv23 = PROTOCOL_TLS
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except ImportError:
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PROTOCOL_SSLv23 = PROTOCOL_TLS = 2
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try:
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from ssl import OP_NO_COMPRESSION, OP_NO_SSLv2, OP_NO_SSLv3
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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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try: # OP_NO_TICKET was added in Python 3.6
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from ssl import OP_NO_TICKET
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except ImportError:
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OP_NO_TICKET = 0x4000
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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 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, DSS, and other
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# insecure ciphers for security reasons.
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# - NOTE: TLS 1.3 cipher suites are managed through a different interface
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# not exposed by CPython (yet!) and are enabled by default if they're available.
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DEFAULT_CIPHERS = ":".join(
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[
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"ECDHE+AESGCM",
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"ECDHE+CHACHA20",
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"DHE+AESGCM",
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"DHE+CHACHA20",
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"ECDH+AESGCM",
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"DH+AESGCM",
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"ECDH+AES",
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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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"!DSS",
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]
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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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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, cadata=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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if cadata is not None:
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raise SSLError("CA data 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("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(
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'Fingerprints did not match. Expected "{0}", got "{1}".'.format(
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fingerprint, hexlify(cert_digest)
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)
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)
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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_REQUIRED`.
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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_REQUIRED
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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_TLS
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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(
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ssl_version=None, cert_reqs=None, options=None, ciphers=None
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):
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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``, and ``ssl.OP_NO_TICKET``.
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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 PROTOCOL_TLS)
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context.set_ciphers(ciphers or DEFAULT_CIPHERS)
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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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# TLSv1.2 only. Unless set explicitly, do not request tickets.
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# This may save some bandwidth on wire, and although the ticket is encrypted,
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# there is a risk associated with it being on wire,
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# if the server is not rotating its ticketing keys properly.
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options |= OP_NO_TICKET
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context.options |= options
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# Enable post-handshake authentication for TLS 1.3, see GH #1634. PHA is
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# necessary for conditional client cert authentication with TLS 1.3.
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# The attribute is None for OpenSSL <= 1.1.0 or does not exist in older
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# versions of Python. We only enable on Python 3.7.4+ or if certificate
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# verification is enabled to work around Python issue #37428
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# See: https://bugs.python.org/issue37428
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if (cert_reqs == ssl.CERT_REQUIRED or sys.version_info >= (3, 7, 4)) and getattr(
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context, "post_handshake_auth", None
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) is not None:
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context.post_handshake_auth = True
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context.verify_mode = cert_reqs
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if (
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getattr(context, "check_hostname", None) is not None
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): # 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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# Enable logging of TLS session keys via defacto standard environment variable
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# 'SSLKEYLOGFILE', if the feature is available (Python 3.8+). Skip empty values.
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if hasattr(context, "keylog_filename"):
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sslkeylogfile = os.environ.get("SSLKEYLOGFILE")
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if sslkeylogfile:
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context.keylog_filename = sslkeylogfile
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return context
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def ssl_wrap_socket(
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sock,
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keyfile=None,
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certfile=None,
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cert_reqs=None,
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ca_certs=None,
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server_hostname=None,
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ssl_version=None,
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ciphers=None,
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ssl_context=None,
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ca_cert_dir=None,
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key_password=None,
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ca_cert_data=None,
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tls_in_tls=False,
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):
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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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:param key_password:
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Optional password if the keyfile is encrypted.
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:param ca_cert_data:
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Optional string containing CA certificates in PEM format suitable for
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passing as the cadata parameter to SSLContext.load_verify_locations()
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:param tls_in_tls:
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Use SSLTransport to wrap the existing socket.
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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, ciphers=ciphers)
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if ca_certs or ca_cert_dir or ca_cert_data:
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try:
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context.load_verify_locations(ca_certs, ca_cert_dir, ca_cert_data)
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except (IOError, OSError) as e:
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raise SSLError(e)
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elif ssl_context is None and hasattr(context, "load_default_certs"):
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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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# Attempt to detect if we get the goofy behavior of the
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# keyfile being encrypted and OpenSSL asking for the
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# passphrase via the terminal and instead error out.
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if keyfile and key_password is None and _is_key_file_encrypted(keyfile):
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raise SSLError("Client private key is encrypted, password is required")
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if certfile:
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if key_password is None:
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context.load_cert_chain(certfile, keyfile)
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else:
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context.load_cert_chain(certfile, keyfile, key_password)
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try:
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if hasattr(context, "set_alpn_protocols"):
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context.set_alpn_protocols(ALPN_PROTOCOLS)
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except NotImplementedError:
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pass
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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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use_sni_hostname = server_hostname and not is_ipaddress(server_hostname)
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# SecureTransport uses server_hostname in certificate verification.
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send_sni = (use_sni_hostname and HAS_SNI) or (
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IS_SECURETRANSPORT and server_hostname
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)
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# Do not warn the user if server_hostname is an invalid SNI hostname.
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if not HAS_SNI and use_sni_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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if send_sni:
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ssl_sock = _ssl_wrap_socket_impl(
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sock, context, tls_in_tls, server_hostname=server_hostname
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)
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else:
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ssl_sock = _ssl_wrap_socket_impl(sock, context, tls_in_tls)
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return ssl_sock
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def is_ipaddress(hostname):
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"""Detects whether the hostname given is an IPv4 or IPv6 address.
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Also detects IPv6 addresses with Zone IDs.
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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 not six.PY2 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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return bool(IPV4_RE.match(hostname) or BRACELESS_IPV6_ADDRZ_RE.match(hostname))
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def _is_key_file_encrypted(key_file):
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"""Detects if a key file is encrypted or not."""
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with open(key_file, "r") as f:
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for line in f:
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# Look for Proc-Type: 4,ENCRYPTED
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if "ENCRYPTED" in line:
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return True
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return False
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def _ssl_wrap_socket_impl(sock, ssl_context, tls_in_tls, server_hostname=None):
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if tls_in_tls:
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if not SSLTransport:
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# Import error, ssl is not available.
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raise ProxySchemeUnsupported(
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"TLS in TLS requires support for the 'ssl' module"
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)
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SSLTransport._validate_ssl_context_for_tls_in_tls(ssl_context)
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return SSLTransport(sock, ssl_context, server_hostname)
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if server_hostname:
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return ssl_context.wrap_socket(sock, server_hostname=server_hostname)
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else:
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return ssl_context.wrap_socket(sock)
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