# Wrapper module for _ssl, providing some additional facilities

# implemented in Python.  Written by Bill Janssen.

"""This module provides some more Pythonic support for SSL.

Object types:

  SSLSocket -- subtype of socket.socket which does SSL over the socket

Exceptions:

  SSLError -- exception raised for I/O errors

Functions:

  cert_time_to_seconds -- convert time string used for certificate

                          notBefore and notAfter functions to integer

                          seconds past the Epoch (the time values

                          returned from time.time())

  fetch_server_certificate (HOST, PORT) -- fetch the certificate provided

                          by the server running on HOST at port PORT.  No

                          validation of the certificate is performed.

Integer constants:

SSL_ERROR_ZERO_RETURN

SSL_ERROR_WANT_READ

SSL_ERROR_WANT_WRITE

SSL_ERROR_WANT_X509_LOOKUP

SSL_ERROR_SYSCALL

SSL_ERROR_SSL

SSL_ERROR_WANT_CONNECT

SSL_ERROR_EOF

SSL_ERROR_INVALID_ERROR_CODE

The following group define certificate requirements that one side is

allowing/requiring from the other side:

CERT_NONE - no certificates from the other side are required (or will

            be looked at if provided)

CERT_OPTIONAL - certificates are not required, but if provided will be

                validated, and if validation fails, the connection will

                also fail

CERT_REQUIRED - certificates are required, and will be validated, and

                if validation fails, the connection will also fail

The following constants identify various SSL protocol variants:

PROTOCOL_SSLv2

PROTOCOL_SSLv3

PROTOCOL_SSLv23

PROTOCOL_TLS

PROTOCOL_TLS_CLIENT

PROTOCOL_TLS_SERVER

PROTOCOL_TLSv1

PROTOCOL_TLSv1_1

PROTOCOL_TLSv1_2

The following constants identify various SSL alert message descriptions as per

http://www.iana.org/assignments/tls-parameters/tls-parameters.xml#tls-parameters-6

ALERT_DESCRIPTION_CLOSE_NOTIFY

ALERT_DESCRIPTION_UNEXPECTED_MESSAGE

ALERT_DESCRIPTION_BAD_RECORD_MAC

ALERT_DESCRIPTION_RECORD_OVERFLOW

ALERT_DESCRIPTION_DECOMPRESSION_FAILURE

ALERT_DESCRIPTION_HANDSHAKE_FAILURE

ALERT_DESCRIPTION_BAD_CERTIFICATE

ALERT_DESCRIPTION_UNSUPPORTED_CERTIFICATE

ALERT_DESCRIPTION_CERTIFICATE_REVOKED

ALERT_DESCRIPTION_CERTIFICATE_EXPIRED

ALERT_DESCRIPTION_CERTIFICATE_UNKNOWN

ALERT_DESCRIPTION_ILLEGAL_PARAMETER

ALERT_DESCRIPTION_UNKNOWN_CA

ALERT_DESCRIPTION_ACCESS_DENIED

ALERT_DESCRIPTION_DECODE_ERROR

ALERT_DESCRIPTION_DECRYPT_ERROR

ALERT_DESCRIPTION_PROTOCOL_VERSION

ALERT_DESCRIPTION_INSUFFICIENT_SECURITY

ALERT_DESCRIPTION_INTERNAL_ERROR

ALERT_DESCRIPTION_USER_CANCELLED

ALERT_DESCRIPTION_NO_RENEGOTIATION

ALERT_DESCRIPTION_UNSUPPORTED_EXTENSION

ALERT_DESCRIPTION_CERTIFICATE_UNOBTAINABLE

ALERT_DESCRIPTION_UNRECOGNIZED_NAME

ALERT_DESCRIPTION_BAD_CERTIFICATE_STATUS_RESPONSE

ALERT_DESCRIPTION_BAD_CERTIFICATE_HASH_VALUE

ALERT_DESCRIPTION_UNKNOWN_PSK_IDENTITY

"""

import ipaddress

import textwrap

import re

import sys

import os

from collections import namedtuple

from enum import Enum as _Enum, IntEnum as _IntEnum, IntFlag as _IntFlag

import _ssl             # if we can't import it, let the error propagate

from _ssl import OPENSSL_VERSION_NUMBER, OPENSSL_VERSION_INFO, OPENSSL_VERSION

from _ssl import _SSLContext, MemoryBIO, SSLSession

from _ssl import (

    SSLError, SSLZeroReturnError, SSLWantReadError, SSLWantWriteError,

    SSLSyscallError, SSLEOFError,

    )

from _ssl import txt2obj as _txt2obj, nid2obj as _nid2obj

from _ssl import RAND_status, RAND_add, RAND_bytes, RAND_pseudo_bytes

try:

    from _ssl import RAND_egd

except ImportError:

    # LibreSSL does not provide RAND_egd

    pass

from _ssl import HAS_SNI, HAS_ECDH, HAS_NPN, HAS_ALPN, HAS_TLSv1_3

from _ssl import _OPENSSL_API_VERSION

_IntEnum._convert(

    '_SSLMethod', __name__,

    lambda name: name.startswith('PROTOCOL_') and name != 'PROTOCOL_SSLv23',

    source=_ssl)

_IntFlag._convert(

    'Options', __name__,

    lambda name: name.startswith('OP_'),

    source=_ssl)

_IntEnum._convert(

    'AlertDescription', __name__,

    lambda name: name.startswith('ALERT_DESCRIPTION_'),

    source=_ssl)

_IntEnum._convert(

    'SSLErrorNumber', __name__,

    lambda name: name.startswith('SSL_ERROR_'),

    source=_ssl)

_IntFlag._convert(

    'VerifyFlags', __name__,

    lambda name: name.startswith('VERIFY_'),

    source=_ssl)

_IntEnum._convert(

    'VerifyMode', __name__,

    lambda name: name.startswith('CERT_'),

    source=_ssl)

PROTOCOL_SSLv23 = _SSLMethod.PROTOCOL_SSLv23 = _SSLMethod.PROTOCOL_TLS

_PROTOCOL_NAMES = {value: name for name, value in _SSLMethod.__members__.items()}

_SSLv2_IF_EXISTS = getattr(_SSLMethod, 'PROTOCOL_SSLv2', None)

if sys.platform == "win32":

    from _ssl import enum_certificates, enum_crls

from socket import socket, AF_INET, SOCK_STREAM, create_connection

from socket import SOL_SOCKET, SO_TYPE

import base64        # for DER-to-PEM translation

import errno

import warnings

socket_error = OSError  # keep that public name in module namespace

if _ssl.HAS_TLS_UNIQUE:

    CHANNEL_BINDING_TYPES = ['tls-unique']

else:

    CHANNEL_BINDING_TYPES = []

# Disable weak or insecure ciphers by default

# (OpenSSL's default setting is 'DEFAULT:!aNULL:!eNULL')

# Enable a better set of ciphers by default

# This list has been explicitly chosen to:

#   * TLS 1.3 ChaCha20 and AES-GCM cipher suites

#   * Prefer cipher suites that offer perfect forward secrecy (DHE/ECDHE)

#   * Prefer ECDHE over DHE for better performance

#   * Prefer AEAD over CBC for better performance and security

#   * Prefer AES-GCM over ChaCha20 because most platforms have AES-NI

#     (ChaCha20 needs OpenSSL 1.1.0 or patched 1.0.2)

#   * Prefer any AES-GCM and ChaCha20 over any AES-CBC for better

#     performance and security

#   * Then Use HIGH cipher suites as a fallback

#   * Disable NULL authentication, NULL encryption, 3DES and MD5 MACs

#     for security reasons

_DEFAULT_CIPHERS = (

    '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:ECDH+HIGH:DH+HIGH:RSA+AESGCM:RSA+AES:RSA+HIGH:'

    '!aNULL:!eNULL:!MD5:!3DES'

    )

# Restricted and more secure ciphers for the server side

# This list has been explicitly chosen to:

#   * TLS 1.3 ChaCha20 and AES-GCM cipher suites

#   * Prefer cipher suites that offer perfect forward secrecy (DHE/ECDHE)

#   * Prefer ECDHE over DHE for better performance

#   * Prefer AEAD over CBC for better performance and security

#   * Prefer AES-GCM over ChaCha20 because most platforms have AES-NI

#   * Prefer any AES-GCM and ChaCha20 over any AES-CBC for better

#     performance and security

#   * Then Use HIGH cipher suites as a fallback

#   * Disable NULL authentication, NULL encryption, MD5 MACs, DSS, RC4, and

#     3DES for security reasons

_RESTRICTED_SERVER_CIPHERS = (

    '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:ECDH+HIGH:DH+HIGH:RSA+AESGCM:RSA+AES:RSA+HIGH:'

    '!aNULL:!eNULL:!MD5:!DSS:!RC4:!3DES'

)

class CertificateError(ValueError):

    pass

def _dnsname_match(dn, hostname, max_wildcards=1):

    """Matching according to RFC 6125, section 6.4.3

    http://tools.ietf.org/html/rfc6125#section-6.4.3

    """

    pats = []

    if not dn:

        return False

    leftmost, *remainder = dn.split(r'.')

    wildcards = leftmost.count('*')

    if wildcards > max_wildcards:

        # Issue #17980: avoid denials of service by refusing more

        # than one wildcard per fragment.  A survey of established

        # policy among SSL implementations showed it to be a

        # reasonable choice.

        raise CertificateError(

            "too many wildcards in certificate DNS name: " + repr(dn))

    # speed up common case w/o wildcards

    if not wildcards:

        return dn.lower() == hostname.lower()

    # RFC 6125, section 6.4.3, subitem 1.

    # The client SHOULD NOT attempt to match a presented identifier in which

    # the wildcard character comprises a label other than the left-most label.

    if leftmost == '*':

        # When '*' is a fragment by itself, it matches a non-empty dotless

        # fragment.

        pats.append('[^.]+')

    elif leftmost.startswith('xn--') or hostname.startswith('xn--'):

        # RFC 6125, section 6.4.3, subitem 3.

        # The client SHOULD NOT attempt to match a presented identifier

        # where the wildcard character is embedded within an A-label or

        # U-label of an internationalized domain name.

        pats.append(re.escape(leftmost))

    else:

        # Otherwise, '*' matches any dotless string, e.g. www*

        pats.append(re.escape(leftmost).replace(r'\*', '[^.]*'))

    # add the remaining fragments, ignore any wildcards

    for frag in remainder:

        pats.append(re.escape(frag))

    pat = re.compile(r'\A' + r'\.'.join(pats) + r'\Z', re.IGNORECASE)

    return pat.match(hostname)

def _ipaddress_match(ipname, host_ip):

    """Exact matching of IP addresses.

    RFC 6125 explicitly doesn't define an algorithm for this

    (section 1.7.2 - "Out of Scope").

    """

    # OpenSSL may add a trailing newline to a subjectAltName's IP address

    ip = ipaddress.ip_address(ipname.rstrip())

    return ip == host_ip

def match_hostname(cert, hostname):

    """Verify that *cert* (in decoded format as returned by

    SSLSocket.getpeercert()) matches the *hostname*.  RFC 2818 and RFC 6125

    rules are followed, but IP addresses are not accepted for *hostname*.

    CertificateError is raised on failure. On success, the function

    returns nothing.

    """

    if not cert:

        raise ValueError("empty or no certificate, match_hostname needs a "

                         "SSL socket or SSL context with either "

                         "CERT_OPTIONAL or CERT_REQUIRED")

    try:

        host_ip = ipaddress.ip_address(hostname)

    except ValueError:

        # Not an IP address (common case)

        host_ip = None

    dnsnames = []

    san = cert.get('subjectAltName', ())

    for key, value in san:

        if key == 'DNS':

            if host_ip is None and _dnsname_match(value, hostname):

                return

            dnsnames.append(value)

        elif key == 'IP Address':

            if host_ip is not None and _ipaddress_match(value, host_ip):

                return

            dnsnames.append(value)

    if not dnsnames:

        # The subject is only checked when there is no dNSName entry

        # in subjectAltName

        for sub in cert.get('subject', ()):

            for key, value in sub:

                # XXX according to RFC 2818, the most specific Common Name

                # must be used.

                if key == 'commonName':

                    if _dnsname_match(value, hostname):

                        return

                    dnsnames.append(value)

    if len(dnsnames) > 1:

        raise CertificateError("hostname %r "

            "doesn't match either of %s"

            % (hostname, ', '.join(map(repr, dnsnames))))

    elif len(dnsnames) == 1:

        raise CertificateError("hostname %r "

            "doesn't match %r"

            % (hostname, dnsnames[0]))

    else:

        raise CertificateError("no appropriate commonName or "

            "subjectAltName fields were found")

DefaultVerifyPaths = namedtuple("DefaultVerifyPaths",

    "cafile capath openssl_cafile_env openssl_cafile openssl_capath_env "

    "openssl_capath")

def get_default_verify_paths():

    """Return paths to default cafile and capath.

    """

    parts = _ssl.get_default_verify_paths()

    # environment vars shadow paths

    cafile = os.environ.get(parts[0], parts[1])

    capath = os.environ.get(parts[2], parts[3])

    return DefaultVerifyPaths(cafile if os.path.isfile(cafile) else None,

                              capath if os.path.isdir(capath) else None,

                              *parts)

class _ASN1Object(namedtuple("_ASN1Object", "nid shortname longname oid")):

    """ASN.1 object identifier lookup

    """

    __slots__ = ()

    def __new__(cls, oid):

        return super().__new__(cls, *_txt2obj(oid, name=False))

    @classmethod

    def fromnid(cls, nid):

        """Create _ASN1Object from OpenSSL numeric ID

        """

        return super().__new__(cls, *_nid2obj(nid))

    @classmethod

    def fromname(cls, name):

        """Create _ASN1Object from short name, long name or OID

        """

        return super().__new__(cls, *_txt2obj(name, name=True))

class Purpose(_ASN1Object, _Enum):

    """SSLContext purpose flags with X509v3 Extended Key Usage objects

    """

    SERVER_AUTH = '1.3.6.1.5.5.7.3.1'

    CLIENT_AUTH = '1.3.6.1.5.5.7.3.2'

class SSLContext(_SSLContext):

    """An SSLContext holds various SSL-related configuration options and

    data, such as certificates and possibly a private key."""

    __slots__ = ('protocol', '__weakref__')

    _windows_cert_stores = ("CA", "ROOT")

    def __new__(cls, protocol=PROTOCOL_TLS, *args, **kwargs):

        self = _SSLContext.__new__(cls, protocol)

        if protocol != _SSLv2_IF_EXISTS:

            self.set_ciphers(_DEFAULT_CIPHERS)

        return self

    def __init__(self, protocol=PROTOCOL_TLS):

        self.protocol = protocol

    def wrap_socket(self, sock, server_side=False,

                    do_handshake_on_connect=True,

                    suppress_ragged_eofs=True,

                    server_hostname=None, session=None):

        return SSLSocket(sock=sock, server_side=server_side,

                         do_handshake_on_connect=do_handshake_on_connect,

                         suppress_ragged_eofs=suppress_ragged_eofs,

                         server_hostname=server_hostname,

                         _context=self, _session=session)

    def wrap_bio(self, incoming, outgoing, server_side=False,

                 server_hostname=None, session=None):

        sslobj = self._wrap_bio(incoming, outgoing, server_side=server_side,

                                server_hostname=server_hostname)

        return SSLObject(sslobj, session=session)

    def set_npn_protocols(self, npn_protocols):

        protos = bytearray()

        for protocol in npn_protocols:

            b = bytes(protocol, 'ascii')

            if len(b) == 0 or len(b) > 255:

                raise SSLError('NPN protocols must be 1 to 255 in length')

            protos.append(len(b))

            protos.extend(b)

        self._set_npn_protocols(protos)

    def set_alpn_protocols(self, alpn_protocols):

        protos = bytearray()

        for protocol in alpn_protocols:

            b = bytes(protocol, 'ascii')

            if len(b) == 0 or len(b) > 255:

                raise SSLError('ALPN protocols must be 1 to 255 in length')

            protos.append(len(b))

            protos.extend(b)

        self._set_alpn_protocols(protos)

    def _load_windows_store_certs(self, storename, purpose):

        certs = bytearray()

        try:

            for cert, encoding, trust in enum_certificates(storename):

                # CA certs are never PKCS#7 encoded

                if encoding == "x509_asn":

                    if trust is True or purpose.oid in trust:

                        certs.extend(cert)

        except PermissionError:

            warnings.warn("unable to enumerate Windows certificate store")

        if certs:

            self.load_verify_locations(cadata=certs)

        return certs

    def load_default_certs(self, purpose=Purpose.SERVER_AUTH):

        if not isinstance(purpose, _ASN1Object):

            raise TypeError(purpose)

        if sys.platform == "win32":

            for storename in self._windows_cert_stores:

                self._load_windows_store_certs(storename, purpose)

        self.set_default_verify_paths()

    @property

    def options(self):

        return Options(super().options)

    @options.setter

    def options(self, value):

        super(SSLContext, SSLContext).options.__set__(self, value)

    @property

    def verify_flags(self):

        return VerifyFlags(super().verify_flags)

    @verify_flags.setter

    def verify_flags(self, value):

        super(SSLContext, SSLContext).verify_flags.__set__(self, value)

    @property

    def verify_mode(self):

        value = super().verify_mode

        try:

            return VerifyMode(value)

        except ValueError:

            return value

    @verify_mode.setter

    def verify_mode(self, value):

        super(SSLContext, SSLContext).verify_mode.__set__(self, value)

def create_default_context(purpose=Purpose.SERVER_AUTH, *, cafile=None,

                           capath=None, cadata=None):

    """Create a SSLContext object with default settings.

    NOTE: The protocol and settings may change anytime without prior

          deprecation. The values represent a fair balance between maximum

          compatibility and security.

    """

    if not isinstance(purpose, _ASN1Object):

        raise TypeError(purpose)

    # SSLContext sets OP_NO_SSLv2, OP_NO_SSLv3, OP_NO_COMPRESSION,

    # OP_CIPHER_SERVER_PREFERENCE, OP_SINGLE_DH_USE and OP_SINGLE_ECDH_USE

    # by default.

    context = SSLContext(PROTOCOL_TLS)

    if purpose == Purpose.SERVER_AUTH:

        # verify certs and host name in client mode

        context.verify_mode = CERT_REQUIRED

        context.check_hostname = True

    elif purpose == Purpose.CLIENT_AUTH:

        context.set_ciphers(_RESTRICTED_SERVER_CIPHERS)

    if cafile or capath or cadata:

        context.load_verify_locations(cafile, capath, cadata)

    elif context.verify_mode != CERT_NONE:

        # no explicit cafile, capath or cadata but the verify mode is

        # CERT_OPTIONAL or CERT_REQUIRED. Let's try to load default system

        # root CA certificates for the given purpose. This may fail silently.

        context.load_default_certs(purpose)

    return context

def _create_unverified_context(protocol=PROTOCOL_TLS, *, cert_reqs=None,

                           check_hostname=False, purpose=Purpose.SERVER_AUTH,

                           certfile=None, keyfile=None,

                           cafile=None, capath=None, cadata=None):

    """Create a SSLContext object for Python stdlib modules

    All Python stdlib modules shall use this function to create SSLContext

    objects in order to keep common settings in one place. The configuration

    is less restrict than create_default_context()'s to increase backward

    compatibility.

    """

    if not isinstance(purpose, _ASN1Object):

        raise TypeError(purpose)

    # SSLContext sets OP_NO_SSLv2, OP_NO_SSLv3, OP_NO_COMPRESSION,

    # OP_CIPHER_SERVER_PREFERENCE, OP_SINGLE_DH_USE and OP_SINGLE_ECDH_USE

    # by default.

    context = SSLContext(protocol)

    if cert_reqs is not None:

        context.verify_mode = cert_reqs

    context.check_hostname = check_hostname

    if keyfile and not certfile:

        raise ValueError("certfile must be specified")

    if certfile or keyfile:

        context.load_cert_chain(certfile, keyfile)

    # load CA root certs

    if cafile or capath or cadata:

        context.load_verify_locations(cafile, capath, cadata)

    elif context.verify_mode != CERT_NONE:

        # no explicit cafile, capath or cadata but the verify mode is

        # CERT_OPTIONAL or CERT_REQUIRED. Let's try to load default system

        # root CA certificates for the given purpose. This may fail silently.

        context.load_default_certs(purpose)

    return context

# Used by http.client if no context is explicitly passed.

_create_default_https_context = create_default_context

# Backwards compatibility alias, even though it's not a public name.

_create_stdlib_context = _create_unverified_context

class SSLObject:

    """This class implements an interface on top of a low-level SSL object as

    implemented by OpenSSL. This object captures the state of an SSL connection

    but does not provide any network IO itself. IO needs to be performed

    through separate "BIO" objects which are OpenSSL's IO abstraction layer.

    This class does not have a public constructor. Instances are returned by

    ``SSLContext.wrap_bio``. This class is typically used by framework authors

    that want to implement asynchronous IO for SSL through memory buffers.

    When compared to ``SSLSocket``, this object lacks the following features:

     * Any form of network IO incluging methods such as ``recv`` and ``send``.

     * The ``do_handshake_on_connect`` and ``suppress_ragged_eofs`` machinery.

    """

    def __init__(self, sslobj, owner=None, session=None):

        self._sslobj = sslobj

        # Note: _sslobj takes a weak reference to owner

        self._sslobj.owner = owner or self

        if session is not None:

            self._sslobj.session = session

    @property

    def context(self):

        """The SSLContext that is currently in use."""

        return self._sslobj.context

    @context.setter

    def context(self, ctx):

        self._sslobj.context = ctx

    @property

    def session(self):

        """The SSLSession for client socket."""

        return self._sslobj.session

    @session.setter

    def session(self, session):

        self._sslobj.session = session

    @property

    def session_reused(self):

        """Was the client session reused during handshake"""

        return self._sslobj.session_reused

    @property

    def server_side(self):

        """Whether this is a server-side socket."""

        return self._sslobj.server_side

    @property

    def server_hostname(self):

        """The currently set server hostname (for SNI), or ``None`` if no

        server hostame is set."""

        return self._sslobj.server_hostname

    def read(self, len=1024, buffer=None):

        """Read up to 'len' bytes from the SSL object and return them.

        If 'buffer' is provided, read into this buffer and return the number of

        bytes read.

        """

        if buffer is not None:

            v = self._sslobj.read(len, buffer)

        else:

            v = self._sslobj.read(len)

        return v

    def write(self, data):

        """Write 'data' to the SSL object and return the number of bytes

        written.

        The 'data' argument must support the buffer interface.

        """

        return self._sslobj.write(data)

    def getpeercert(self, binary_form=False):

        """Returns a formatted version of the data in the certificate provided

        by the other end of the SSL channel.

        Return None if no certificate was provided, {} if a certificate was

        provided, but not validated.

        """

        return self._sslobj.peer_certificate(binary_form)

    def selected_npn_protocol(self):

        """Return the currently selected NPN protocol as a string, or ``None``

        if a next protocol was not negotiated or if NPN is not supported by one

        of the peers."""

        if _ssl.HAS_NPN:

            return self._sslobj.selected_npn_protocol()

    def selected_alpn_protocol(self):

        """Return the currently selected ALPN protocol as a string, or ``None``

        if a next protocol was not negotiated or if ALPN is not supported by one

        of the peers."""

        if _ssl.HAS_ALPN:

            return self._sslobj.selected_alpn_protocol()

    def cipher(self):

        """Return the currently selected cipher as a 3-tuple ``(name,

        ssl_version, secret_bits)``."""

        return self._sslobj.cipher()

    def shared_ciphers(self):

        """Return a list of ciphers shared by the client during the handshake or

        None if this is not a valid server connection.

        """

        return self._sslobj.shared_ciphers()

    def compression(self):

        """Return the current compression algorithm in use, or ``None`` if

        compression was not negotiated or not supported by one of the peers."""

        return self._sslobj.compression()

    def pending(self):

        """Return the number of bytes that can be read immediately."""

        return self._sslobj.pending()

    def do_handshake(self):

        """Start the SSL/TLS handshake."""

        self._sslobj.do_handshake()

        if self.context.check_hostname:

            if not self.server_hostname:

                raise ValueError("check_hostname needs server_hostname "

                                 "argument")

            match_hostname(self.getpeercert(), self.server_hostname)

    def unwrap(self):

        """Start the SSL shutdown handshake."""

        return self._sslobj.shutdown()

    def get_channel_binding(self, cb_type="tls-unique"):

        """Get channel binding data for current connection.  Raise ValueError

        if the requested `cb_type` is not supported.  Return bytes of the data

        or None if the data is not available (e.g. before the handshake)."""

        if cb_type not in CHANNEL_BINDING_TYPES:

            raise ValueError("Unsupported channel binding type")

        if cb_type != "tls-unique":

            raise NotImplementedError(

                            "{0} channel binding type not implemented"

                            .format(cb_type))

        return self._sslobj.tls_unique_cb()

    def version(self):

        """Return a string identifying the protocol version used by the

        current SSL channel. """

        return self._sslobj.version()

class SSLSocket(socket):

    """This class implements a subtype of socket.socket that wraps

    the underlying OS socket in an SSL context when necessary, and

    provides read and write methods over that channel."""

    def __init__(self, sock=None, keyfile=None, certfile=None,

                 server_side=False, cert_reqs=CERT_NONE,

                 ssl_version=PROTOCOL_TLS, ca_certs=None,

                 do_handshake_on_connect=True,

                 family=AF_INET, type=SOCK_STREAM, proto=0, fileno=None,

                 suppress_ragged_eofs=True, npn_protocols=None, ciphers=None,

                 server_hostname=None,

                 _context=None, _session=None):

        if _context:

            self._context = _context

        else:

            if server_side and not certfile:

                raise ValueError("certfile must be specified for server-side "

                                 "operations")

            if keyfile and not certfile:

                raise ValueError("certfile must be specified")

            if certfile and not keyfile:

                keyfile = certfile

            self._context = SSLContext(ssl_version)

            self._context.verify_mode = cert_reqs

            if ca_certs:

                self._context.load_verify_locations(ca_certs)

            if certfile:

                self._context.load_cert_chain(certfile, keyfile)

            if npn_protocols:

                self._context.set_npn_protocols(npn_protocols)

            if ciphers:

                self._context.set_ciphers(ciphers)

            self.keyfile = keyfile

            self.certfile = certfile

            self.cert_reqs = cert_reqs

            self.ssl_version = ssl_version

            self.ca_certs = ca_certs

            self.ciphers = ciphers

        # Can't use sock.type as other flags (such as SOCK_NONBLOCK) get

        # mixed in.

        if sock.getsockopt(SOL_SOCKET, SO_TYPE) != SOCK_STREAM:

            raise NotImplementedError("only stream sockets are supported")

        if server_side:

            if server_hostname:

                raise ValueError("server_hostname can only be specified "

                                 "in client mode")

            if _session is not None:

                raise ValueError("session can only be specified in "

                                 "client mode")

        if self._context.check_hostname and not server_hostname:

            raise ValueError("check_hostname requires server_hostname")

        self._session = _session

        self.server_side = server_side

        self.server_hostname = server_hostname

        self.do_handshake_on_connect = do_handshake_on_connect

        self.suppress_ragged_eofs = suppress_ragged_eofs

        if sock is not None:

            socket.__init__(self,

                            family=sock.family,

                            type=sock.type,

                            proto=sock.proto,

                            fileno=sock.fileno())

            self.settimeout(sock.gettimeout())

            sock.detach()

        elif fileno is not None:

            socket.__init__(self, fileno=fileno)

        else:

            socket.__init__(self, family=family, type=type, proto=proto)

        # See if we are connected

        try:

            self.getpeername()

        except OSError as e:

            if e.errno != errno.ENOTCONN:

                raise

            connected = False

        else:

            connected = True

        self._closed = False

        self._sslobj = None

        self._connected = connected

        if connected:

            # create the SSL object

            try:

                sslobj = self._context._wrap_socket(self, server_side,

                                                    server_hostname)

                self._sslobj = SSLObject(sslobj, owner=self,

                                         session=self._session)

                if do_handshake_on_connect:

                    timeout = self.gettimeout()

                    if timeout == 0.0:

                        # non-blocking

                        raise ValueError("do_handshake_on_connect should not be specified for non-blocking sockets")

                    self.do_handshake()

            except (OSError, ValueError):

                self.close()

                raise

    @property

    def context(self):

        return self._context

    @context.setter

    def context(self, ctx):

        self._context = ctx

        self._sslobj.context = ctx

    @property

    def session(self):

        """The SSLSession for client socket."""

        if self._sslobj is not None:

            return self._sslobj.session

    @session.setter

    def session(self, session):

        self._session = session

        if self._sslobj is not None:

            self._sslobj.session = session

    @property

    def session_reused(self):

        """Was the client session reused during handshake"""

        if self._sslobj is not None:

            return self._sslobj.session_reused

    def dup(self):

        raise NotImplemented("Can't dup() %s instances" %

                             self.__class__.__name__)

    def _checkClosed(self, msg=None):

        # raise an exception here if you wish to check for spurious closes

        pass

    def _check_connected(self):

        if not self._connected:

            # getpeername() will raise ENOTCONN if the socket is really

            # not connected; note that we can be connected even without

            # _connected being set, e.g. if connect() first returned

            # EAGAIN.

            self.getpeername()

    def read(self, len=1024, buffer=None):

        """Read up to LEN bytes and return them.

        Return zero-length string on EOF."""

        self._checkClosed()

        if not self._sslobj:

            raise ValueError("Read on closed or unwrapped SSL socket.")

        try:

            return self._sslobj.read(len, buffer)

        except SSLError as x:

            if x.args[0] == SSL_ERROR_EOF and self.suppress_ragged_eofs:

                if buffer is not None:

                    return 0

                else:

                    return b''

            else:

                raise