Add google-endpoints to third_party/.

third_party/google-endpoints/urllib3/util/ssl_.py

+from __future__ import absolute_import
+import errno
+import warnings
+import hmac
+
+from binascii import hexlify, unhexlify
+from hashlib import md5, sha1, sha256
+
+from ..exceptions import SSLError, InsecurePlatformWarning, SNIMissingWarning
+
+
+SSLContext = None
+HAS_SNI = False
+IS_PYOPENSSL = 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
+
+# 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 and DSS for security reasons.
+DEFAULT_CIPHERS = ':'.join([
+    '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 & 3.1
+        supports_set_ciphers = ((2, 7) <= sys.version_info < (3,) or
+                                (3, 2) <= sys.version_info)
+
+        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):
+            if not self.supports_set_ciphers:
+                raise TypeError(
+                    'Your version of Python does not support setting '
+                    'a custom cipher suite. Please upgrade to Python '
+                    '2.7, 3.2, or later if you need this functionality.'
+                )
+            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,
+            }
+            if self.supports_set_ciphers:  # Platform-specific: Python 2.7+
+                return wrap_socket(socket, ciphers=self.ciphers, **kwargs)
+            else:  # Platform-specific: Python 2.6
+                return wrap_socket(socket, **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 abbrevation.
+    (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)
+
+    # 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
+
+    if getattr(context, 'supports_set_ciphers', True):  # Platform-specific: Python 2.6
+        context.set_ciphers(ciphers or DEFAULT_CIPHERS)
+
+    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. This is not
+        supported on Python 2.6 as the ssl module does not support it.
+    :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 2.6, 2.7, 3.2
+            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 HAS_SNI:  # Platform-specific: OpenSSL with enabled SNI
+        return context.wrap_socket(sock, server_hostname=server_hostname)
+
+    warnings.warn(
+        'An HTTPS request has been made, but the SNI (Subject 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)