from __future__ import absolute_import import errno import warnings import hmac import socket from binascii import hexlify, unhexlify from hashlib import md5, sha1, sha256 from ..exceptions import SSLError, InsecurePlatformWarning, SNIMissingWarning import six SSLContext = None HAS_SNI = False IS_PYOPENSSL = False IS_SECURETRANSPORT = False # 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 l, r in zip(bytearray(a), bytearray(b)): result |= l ^ r return result == 0 _const_compare_digest = getattr(hmac, 'compare_digest', _const_compare_digest_backport) try: # Test for SSL features import ssl from ssl import wrap_socket, CERT_NONE, PROTOCOL_SSLv23 from ssl import HAS_SNI # Has SNI? except ImportError: pass try: from ssl import OP_NO_SSLv2, OP_NO_SSLv3, OP_NO_COMPRESSION except ImportError: OP_NO_SSLv2, OP_NO_SSLv3 = 0x1000000, 0x2000000 OP_NO_COMPRESSION = 0x20000 # Python 2.7 doesn't have inet_pton on non-Linux so we fallback on inet_aton in # those cases. This means that we can only detect IPv4 addresses in this case. if hasattr(socket, 'inet_pton'): inet_pton = socket.inet_pton else: # Maybe we can use ipaddress if the user has urllib3[secure]? try: import ipaddress def inet_pton(_, host): if isinstance(host, bytes): host = host.decode('ascii') return ipaddress.ip_address(host) except ImportError: # Platform-specific: Non-Linux def inet_pton(_, host): return socket.inet_aton(host) # 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 TLS 1.3 cipher suites # - 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 and DSS for security reasons. DEFAULT_CIPHERS = ':'.join([ 'TLS13-AES-256-GCM-SHA384', 'TLS13-CHACHA20-POLY1305-SHA256', 'TLS13-AES-128-GCM-SHA256', 'ECDH+AESGCM', 'ECDH+CHACHA20', 'DH+AESGCM', 'DH+CHACHA20', 'ECDH+AES256', 'DH+AES256', 'ECDH+AES128', 'DH+AES', 'RSA+AESGCM', 'RSA+AES', '!aNULL', '!eNULL', '!MD5', ]) try: from ssl import SSLContext # Modern SSL? except ImportError: import sys 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): self.ca_certs = cafile if capath is not None: raise SSLError("CA directories 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/latest/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_NONE`. 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_NONE 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_SSLv23 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``. :param ciphers: Which cipher suites to allow the server to select. :returns: Constructed SSLContext object with specified options :rtype: SSLContext """ context = SSLContext(ssl_version or ssl.PROTOCOL_SSLv23) 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 context.options |= options context.verify_mode = cert_reqs 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 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): """ 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(). """ 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: try: context.load_verify_locations(ca_certs, ca_cert_dir) except IOError as e: # Platform-specific: Python 2.7 raise SSLError(e) # Py33 raises FileNotFoundError which subclasses OSError # These are not equivalent unless we check the errno attribute except OSError as e: # Platform-specific: Python 3.3 and beyond if e.errno == errno.ENOENT: raise SSLError(e) raise # Don't load system certs unless there were no CA certs or # SSLContext object specified manually. 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() if certfile: context.load_cert_chain(certfile, keyfile) # If we detect server_hostname is an IP address then the SNI # extension should not be used according to RFC3546 Section 3.1 # We shouldn't warn the user if SNI isn't available but we would # not be using SNI anyways due to IP address for server_hostname. if ((server_hostname is not None and not is_ipaddress(server_hostname)) or IS_SECURETRANSPORT): if HAS_SNI and server_hostname is not None: return context.wrap_socket(sock, server_hostname=server_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/latest/advanced-usage.html' '#ssl-warnings', SNIMissingWarning ) return context.wrap_socket(sock) def is_ipaddress(hostname): """Detects whether the hostname given is an IP address. :param str hostname: Hostname to examine. :return: True if the hostname is an IP address, False otherwise. """ if six.PY3 and isinstance(hostname, bytes): # IDN A-label bytes are ASCII compatible. hostname = hostname.decode('ascii') families = [socket.AF_INET] if hasattr(socket, 'AF_INET6'): families.append(socket.AF_INET6) for af in families: try: inet_pton(af, hostname) except (socket.error, ValueError, OSError): pass else: return True return False