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Diffstat (limited to 'python/urllib3/util/ssl_.py')
| -rw-r--r-- | python/urllib3/util/ssl_.py | 381 |
1 files changed, 381 insertions, 0 deletions
diff --git a/python/urllib3/util/ssl_.py b/python/urllib3/util/ssl_.py new file mode 100644 index 0000000..64ea192 --- /dev/null +++ b/python/urllib3/util/ssl_.py @@ -0,0 +1,381 @@ +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 +from ..packages 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 + elif getattr(context, 'load_default_certs', None) is not None: + # 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 |