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from binascii import hexlify, unhexlify 

from hashlib import md5, sha1, sha256 

 

from ..exceptions import SSLError, InsecurePlatformWarning 

 

 

SSLContext = None 

HAS_SNI = False 

create_default_context = None 

 

import errno 

import warnings 

 

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 over any AES-CBC for better performance and security, 

# - use 3DES as fallback which is secure but slow, 

# - disable NULL authentication, MD5 MACs and DSS for security reasons. 

DEFAULT_CIPHERS = ( 

    'ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+HIGH:' 

    'DH+HIGH:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+HIGH:RSA+3DES:!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, location): 

            self.ca_certs = location 

 

        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): 

            warnings.warn( 

                'A true SSLContext object is not available. This prevents ' 

                'urllib3 from configuring SSL appropriately and may cause ' 

                'certain SSL connections to fail. For more information, see ' 

                'https://urllib3.readthedocs.org/en/latest/security.html' 

                '#insecureplatformwarning.', 

                InsecurePlatformWarning 

            ) 

            kwargs = { 

                'keyfile': self.keyfile, 

                'certfile': self.certfile, 

                'ca_certs': self.ca_certs, 

                'cert_reqs': self.verify_mode, 

                'ssl_version': self.protocol, 

            } 

            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. 

    """ 

 

    # Maps the length of a digest to a possible hash function producing 

    # this digest. 

    hashfunc_map = { 

        16: md5, 

        20: sha1, 

        32: sha256, 

    } 

 

    fingerprint = fingerprint.replace(':', '').lower() 

    digest_length, odd = divmod(len(fingerprint), 2) 

 

    if odd or digest_length not in hashfunc_map: 

        raise SSLError('Fingerprint is of invalid length.') 

 

    # We need encode() here for py32; works on py2 and p33. 

    fingerprint_bytes = unhexlify(fingerprint.encode()) 

 

    hashfunc = hashfunc_map[digest_length] 

 

    cert_digest = hashfunc(cert).digest() 

 

    if not cert_digest == fingerprint_bytes: 

        raise SSLError('Fingerprints did not match. Expected "{0}", got "{1}".' 

                       .format(hexlify(fingerprint_bytes), 

                               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): 

    """ 

    All arguments except for server_hostname and ssl_context 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. 

    """ 

    context = ssl_context 

    if context is None: 

        context = create_urllib3_context(ssl_version, cert_reqs, 

                                         ciphers=ciphers) 

 

    if ca_certs: 

        try: 

            context.load_verify_locations(ca_certs) 

        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 

    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) 

    return context.wrap_socket(sock)