479 lines
16 KiB
Python
479 lines
16 KiB
Python
# Wrapper module for _ssl, providing some additional facilities
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# implemented in Python. Written by Bill Janssen.
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"""\
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This module provides some more Pythonic support for SSL.
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Object types:
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SSLSocket -- subtype of socket.socket which does SSL over the socket
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Exceptions:
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SSLError -- exception raised for I/O errors
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Functions:
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cert_time_to_seconds -- convert time string used for certificate
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notBefore and notAfter functions to integer
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seconds past the Epoch (the time values
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returned from time.time())
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fetch_server_certificate (HOST, PORT) -- fetch the certificate provided
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by the server running on HOST at port PORT. No
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validation of the certificate is performed.
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Integer constants:
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SSL_ERROR_ZERO_RETURN
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SSL_ERROR_WANT_READ
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SSL_ERROR_WANT_WRITE
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SSL_ERROR_WANT_X509_LOOKUP
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SSL_ERROR_SYSCALL
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SSL_ERROR_SSL
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SSL_ERROR_WANT_CONNECT
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SSL_ERROR_EOF
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SSL_ERROR_INVALID_ERROR_CODE
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The following group define certificate requirements that one side is
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allowing/requiring from the other side:
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CERT_NONE - no certificates from the other side are required (or will
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be looked at if provided)
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CERT_OPTIONAL - certificates are not required, but if provided will be
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validated, and if validation fails, the connection will
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also fail
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CERT_REQUIRED - certificates are required, and will be validated, and
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if validation fails, the connection will also fail
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The following constants identify various SSL protocol variants:
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PROTOCOL_SSLv2
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PROTOCOL_SSLv3
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PROTOCOL_SSLv23
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PROTOCOL_TLSv1
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"""
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import textwrap
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import _ssl # if we can't import it, let the error propagate
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from _ssl import OPENSSL_VERSION_NUMBER, OPENSSL_VERSION_INFO, OPENSSL_VERSION
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from _ssl import SSLError
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from _ssl import CERT_NONE, CERT_OPTIONAL, CERT_REQUIRED
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from _ssl import RAND_status, RAND_egd, RAND_add
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from _ssl import \
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SSL_ERROR_ZERO_RETURN, \
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SSL_ERROR_WANT_READ, \
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SSL_ERROR_WANT_WRITE, \
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SSL_ERROR_WANT_X509_LOOKUP, \
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SSL_ERROR_SYSCALL, \
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SSL_ERROR_SSL, \
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SSL_ERROR_WANT_CONNECT, \
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SSL_ERROR_EOF, \
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SSL_ERROR_INVALID_ERROR_CODE
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from _ssl import PROTOCOL_SSLv3, PROTOCOL_SSLv23, PROTOCOL_TLSv1
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_PROTOCOL_NAMES = {
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PROTOCOL_TLSv1: "TLSv1",
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PROTOCOL_SSLv23: "SSLv23",
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PROTOCOL_SSLv3: "SSLv3",
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}
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try:
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from _ssl import PROTOCOL_SSLv2
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_SSLv2_IF_EXISTS = PROTOCOL_SSLv2
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except ImportError:
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_SSLv2_IF_EXISTS = None
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else:
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_PROTOCOL_NAMES[PROTOCOL_SSLv2] = "SSLv2"
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from socket import socket, _fileobject, _delegate_methods, error as socket_error
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from socket import getnameinfo as _getnameinfo
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import base64 # for DER-to-PEM translation
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import errno
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# Disable weak or insecure ciphers by default
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# (OpenSSL's default setting is 'DEFAULT:!aNULL:!eNULL')
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_DEFAULT_CIPHERS = 'DEFAULT:!aNULL:!eNULL:!LOW:!EXPORT:!SSLv2'
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class SSLSocket(socket):
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"""This class implements a subtype of socket.socket that wraps
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the underlying OS socket in an SSL context when necessary, and
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provides read and write methods over that channel."""
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def __init__(self, sock, keyfile=None, certfile=None,
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server_side=False, cert_reqs=CERT_NONE,
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ssl_version=PROTOCOL_SSLv23, ca_certs=None,
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do_handshake_on_connect=True,
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suppress_ragged_eofs=True, ciphers=None):
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socket.__init__(self, _sock=sock._sock)
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# The initializer for socket overrides the methods send(), recv(), etc.
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# in the instancce, which we don't need -- but we want to provide the
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# methods defined in SSLSocket.
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for attr in _delegate_methods:
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try:
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delattr(self, attr)
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except AttributeError:
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pass
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if ciphers is None and ssl_version != _SSLv2_IF_EXISTS:
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ciphers = _DEFAULT_CIPHERS
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if certfile and not keyfile:
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keyfile = certfile
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# see if it's connected
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try:
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socket.getpeername(self)
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except socket_error, e:
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if e.errno != errno.ENOTCONN:
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raise
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# no, no connection yet
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self._connected = False
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self._sslobj = None
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else:
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# yes, create the SSL object
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self._connected = True
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self._sslobj = _ssl.sslwrap(self._sock, server_side,
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keyfile, certfile,
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cert_reqs, ssl_version, ca_certs,
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ciphers)
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if do_handshake_on_connect:
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self.do_handshake()
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self.keyfile = keyfile
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self.certfile = certfile
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self.cert_reqs = cert_reqs
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self.ssl_version = ssl_version
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self.ca_certs = ca_certs
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self.ciphers = ciphers
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self.do_handshake_on_connect = do_handshake_on_connect
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self.suppress_ragged_eofs = suppress_ragged_eofs
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self._makefile_refs = 0
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def read(self, len=1024):
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"""Read up to LEN bytes and return them.
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Return zero-length string on EOF."""
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try:
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return self._sslobj.read(len)
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except SSLError, x:
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if x.args[0] == SSL_ERROR_EOF and self.suppress_ragged_eofs:
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return ''
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else:
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raise
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def write(self, data):
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"""Write DATA to the underlying SSL channel. Returns
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number of bytes of DATA actually transmitted."""
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return self._sslobj.write(data)
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def getpeercert(self, binary_form=False):
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"""Returns a formatted version of the data in the
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certificate provided by the other end of the SSL channel.
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Return None if no certificate was provided, {} if a
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certificate was provided, but not validated."""
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return self._sslobj.peer_certificate(binary_form)
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def cipher(self):
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if not self._sslobj:
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return None
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else:
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return self._sslobj.cipher()
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def send(self, data, flags=0):
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if self._sslobj:
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if flags != 0:
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raise ValueError(
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"non-zero flags not allowed in calls to send() on %s" %
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self.__class__)
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while True:
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try:
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v = self._sslobj.write(data)
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except SSLError, x:
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if x.args[0] == SSL_ERROR_WANT_READ:
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return 0
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elif x.args[0] == SSL_ERROR_WANT_WRITE:
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return 0
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else:
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raise
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else:
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return v
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else:
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return self._sock.send(data, flags)
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def sendto(self, data, flags_or_addr, addr=None):
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if self._sslobj:
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raise ValueError("sendto not allowed on instances of %s" %
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self.__class__)
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elif addr is None:
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return self._sock.sendto(data, flags_or_addr)
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else:
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return self._sock.sendto(data, flags_or_addr, addr)
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def sendall(self, data, flags=0):
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if self._sslobj:
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if flags != 0:
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raise ValueError(
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"non-zero flags not allowed in calls to sendall() on %s" %
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self.__class__)
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amount = len(data)
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count = 0
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while (count < amount):
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v = self.send(data[count:])
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count += v
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return amount
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else:
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return socket.sendall(self, data, flags)
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def recv(self, buflen=1024, flags=0):
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if self._sslobj:
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if flags != 0:
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raise ValueError(
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"non-zero flags not allowed in calls to recv() on %s" %
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self.__class__)
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return self.read(buflen)
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else:
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return self._sock.recv(buflen, flags)
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def recv_into(self, buffer, nbytes=None, flags=0):
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if buffer and (nbytes is None):
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nbytes = len(buffer)
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elif nbytes is None:
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nbytes = 1024
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if self._sslobj:
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if flags != 0:
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raise ValueError(
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"non-zero flags not allowed in calls to recv_into() on %s" %
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self.__class__)
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tmp_buffer = self.read(nbytes)
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v = len(tmp_buffer)
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buffer[:v] = tmp_buffer
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return v
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else:
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return self._sock.recv_into(buffer, nbytes, flags)
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def recvfrom(self, buflen=1024, flags=0):
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if self._sslobj:
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raise ValueError("recvfrom not allowed on instances of %s" %
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self.__class__)
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else:
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return self._sock.recvfrom(buflen, flags)
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def recvfrom_into(self, buffer, nbytes=None, flags=0):
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if self._sslobj:
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raise ValueError("recvfrom_into not allowed on instances of %s" %
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self.__class__)
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else:
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return self._sock.recvfrom_into(buffer, nbytes, flags)
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def pending(self):
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if self._sslobj:
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return self._sslobj.pending()
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else:
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return 0
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def unwrap(self):
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if self._sslobj:
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s = self._sslobj.shutdown()
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self._sslobj = None
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return s
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else:
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raise ValueError("No SSL wrapper around " + str(self))
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def shutdown(self, how):
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self._sslobj = None
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socket.shutdown(self, how)
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def close(self):
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if self._makefile_refs < 1:
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self._sslobj = None
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socket.close(self)
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else:
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self._makefile_refs -= 1
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def do_handshake(self):
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"""Perform a TLS/SSL handshake."""
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self._sslobj.do_handshake()
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def _real_connect(self, addr, return_errno):
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# Here we assume that the socket is client-side, and not
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# connected at the time of the call. We connect it, then wrap it.
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if self._connected:
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raise ValueError("attempt to connect already-connected SSLSocket!")
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self._sslobj = _ssl.sslwrap(self._sock, False, self.keyfile, self.certfile,
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self.cert_reqs, self.ssl_version,
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self.ca_certs, self.ciphers)
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try:
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if return_errno:
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rc = socket.connect_ex(self, addr)
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else:
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rc = None
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socket.connect(self, addr)
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if not rc:
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if self.do_handshake_on_connect:
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self.do_handshake()
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self._connected = True
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return rc
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except socket_error:
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self._sslobj = None
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raise
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def connect(self, addr):
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"""Connects to remote ADDR, and then wraps the connection in
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an SSL channel."""
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self._real_connect(addr, False)
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def connect_ex(self, addr):
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"""Connects to remote ADDR, and then wraps the connection in
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an SSL channel."""
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return self._real_connect(addr, True)
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def accept(self):
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"""Accepts a new connection from a remote client, and returns
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a tuple containing that new connection wrapped with a server-side
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SSL channel, and the address of the remote client."""
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newsock, addr = socket.accept(self)
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try:
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return (SSLSocket(newsock,
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keyfile=self.keyfile,
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certfile=self.certfile,
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server_side=True,
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cert_reqs=self.cert_reqs,
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ssl_version=self.ssl_version,
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ca_certs=self.ca_certs,
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ciphers=self.ciphers,
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do_handshake_on_connect=self.do_handshake_on_connect,
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suppress_ragged_eofs=self.suppress_ragged_eofs),
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addr)
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except socket_error as e:
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newsock.close()
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raise e
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def makefile(self, mode='r', bufsize=-1):
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"""Make and return a file-like object that
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works with the SSL connection. Just use the code
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from the socket module."""
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self._makefile_refs += 1
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# close=True so as to decrement the reference count when done with
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# the file-like object.
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return _fileobject(self, mode, bufsize, close=True)
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def wrap_socket(sock, keyfile=None, certfile=None,
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server_side=False, cert_reqs=CERT_NONE,
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ssl_version=PROTOCOL_SSLv23, ca_certs=None,
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do_handshake_on_connect=True,
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suppress_ragged_eofs=True, ciphers=None):
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return SSLSocket(sock, keyfile=keyfile, certfile=certfile,
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server_side=server_side, cert_reqs=cert_reqs,
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ssl_version=ssl_version, ca_certs=ca_certs,
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do_handshake_on_connect=do_handshake_on_connect,
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suppress_ragged_eofs=suppress_ragged_eofs,
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ciphers=ciphers)
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# some utility functions
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def cert_time_to_seconds(cert_time):
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"""Takes a date-time string in standard ASN1_print form
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("MON DAY 24HOUR:MINUTE:SEC YEAR TIMEZONE") and return
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a Python time value in seconds past the epoch."""
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import time
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return time.mktime(time.strptime(cert_time, "%b %d %H:%M:%S %Y GMT"))
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PEM_HEADER = "-----BEGIN CERTIFICATE-----"
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PEM_FOOTER = "-----END CERTIFICATE-----"
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def DER_cert_to_PEM_cert(der_cert_bytes):
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"""Takes a certificate in binary DER format and returns the
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PEM version of it as a string."""
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if hasattr(base64, 'standard_b64encode'):
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# preferred because older API gets line-length wrong
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f = base64.standard_b64encode(der_cert_bytes)
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return (PEM_HEADER + '\n' +
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textwrap.fill(f, 64) + '\n' +
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PEM_FOOTER + '\n')
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else:
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return (PEM_HEADER + '\n' +
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base64.encodestring(der_cert_bytes) +
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PEM_FOOTER + '\n')
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def PEM_cert_to_DER_cert(pem_cert_string):
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"""Takes a certificate in ASCII PEM format and returns the
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DER-encoded version of it as a byte sequence"""
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if not pem_cert_string.startswith(PEM_HEADER):
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raise ValueError("Invalid PEM encoding; must start with %s"
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% PEM_HEADER)
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if not pem_cert_string.strip().endswith(PEM_FOOTER):
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raise ValueError("Invalid PEM encoding; must end with %s"
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% PEM_FOOTER)
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d = pem_cert_string.strip()[len(PEM_HEADER):-len(PEM_FOOTER)]
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return base64.decodestring(d)
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def get_server_certificate(addr, ssl_version=PROTOCOL_SSLv3, ca_certs=None):
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"""Retrieve the certificate from the server at the specified address,
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and return it as a PEM-encoded string.
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If 'ca_certs' is specified, validate the server cert against it.
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If 'ssl_version' is specified, use it in the connection attempt."""
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host, port = addr
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if (ca_certs is not None):
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cert_reqs = CERT_REQUIRED
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else:
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cert_reqs = CERT_NONE
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s = wrap_socket(socket(), ssl_version=ssl_version,
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cert_reqs=cert_reqs, ca_certs=ca_certs)
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s.connect(addr)
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dercert = s.getpeercert(True)
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s.close()
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return DER_cert_to_PEM_cert(dercert)
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def get_protocol_name(protocol_code):
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return _PROTOCOL_NAMES.get(protocol_code, '<unknown>')
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# a replacement for the old socket.ssl function
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def sslwrap_simple(sock, keyfile=None, certfile=None):
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"""A replacement for the old socket.ssl function. Designed
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for compability with Python 2.5 and earlier. Will disappear in
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Python 3.0."""
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if hasattr(sock, "_sock"):
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sock = sock._sock
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ssl_sock = _ssl.sslwrap(sock, 0, keyfile, certfile, CERT_NONE,
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PROTOCOL_SSLv23, None)
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try:
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sock.getpeername()
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except socket_error:
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# no, no connection yet
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pass
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else:
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# yes, do the handshake
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ssl_sock.do_handshake()
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return ssl_sock
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