def _parse_kexdh_gex_request(self, m):
     minbits = m.get_int()
     preferredbits = m.get_int()
     maxbits = m.get_int()
     # smoosh the user's preferred size into our own limits
     if preferredbits > self.max_bits:
         preferredbits = self.max_bits
     if preferredbits < self.min_bits:
         preferredbits = self.min_bits
     # fix min/max if they're inconsistent.  technically, we could just pout
     # and hang up, but there's no harm in giving them the benefit of the
     # doubt and just picking a bitsize for them.
     if minbits > preferredbits:
         minbits = preferredbits
     if maxbits < preferredbits:
         maxbits = preferredbits
     # now save a copy
     self.min_bits = minbits
     self.preferred_bits = preferredbits
     self.max_bits = maxbits
     # generate prime
     pack = self.transport._get_modulus_pack()
     if pack is None:
         raise SSHException('Can\'t do server-side gex with no modulus pack')
     self.transport._log(DEBUG, 'Picking p (%d <= %d <= %d bits)' % (minbits, preferredbits, maxbits))
     self.g, self.p = pack.get_modulus(minbits, preferredbits, maxbits)
     m = Message()
     m.add_byte(chr(_MSG_KEXDH_GEX_GROUP))
     m.add_mpint(self.p)
     m.add_mpint(self.g)
     self.transport._send_message(m)
     self.transport._expect_packet(_MSG_KEXDH_GEX_INIT)

 def __init__(self, msg=None, data=None, filename=None, password=None, vals=None, file_obj=None):
     self.p = None
     self.q = None
     self.g = None
     self.y = None
     self.x = None
     if file_obj is not None:
         self._from_private_key(file_obj, password)
         return
     if filename is not None:
         self._from_private_key_file(filename, password)
         return
     if (msg is None) and (data is not None):
         msg = Message(data)
     if vals is not None:
         self.p, self.q, self.g, self.y = vals
     else:
         if msg is None:
             raise SSHException('Key object may not be empty')
         if msg.get_string() != b'ssh-dss':
             raise SSHException('Invalid key')
         self.p = msg.get_mpint()
         self.q = msg.get_mpint()
         self.g = msg.get_mpint()
         self.y = msg.get_mpint()
     self.size = util.bit_length(self.p)

 def sign_ssh_data(self, rpool, data):
     digest = SHA.new(data).digest()
     rsa = RSA.construct((int(self.n), int(self.e), int(self.d)))
     sig = util.deflate_long(rsa.sign(self._pkcs1imify(digest), '')[0], 0)
     m = Message()
     m.add_string(b'ssh-rsa')
     m.add_string(sig)
     return m

 def _send_eof(self):
     # you are holding the lock.
     if self.eof_sent:
         return None
     m = Message()
     m.add_byte(chr(MSG_CHANNEL_EOF))
     m.add_int(self.remote_chanid)
     self.eof_sent = True
     self._log(DEBUG, 'EOF sent (%s)', self._name)
     return m

 def test_4_misc(self):
     msg = Message(self.__d)
     self.assertEquals(msg.get_int(), 5)
     self.assertEquals(msg.get_mpint(), 0x1122334455L)
     self.assertEquals(msg.get_so_far(), self.__d[:13])
     self.assertEquals(msg.get_remainder(), self.__d[13:])
     msg.rewind()
     self.assertEquals(msg.get_int(), 5)
     self.assertEquals(msg.get_so_far(), self.__d[:4])
     self.assertEquals(msg.get_remainder(), self.__d[4:])

 def invoke_shell(self):
     """
     Request an interactive shell session on this channel.  If the server
     allows it, the channel will then be directly connected to the stdin,
     stdout, and stderr of the shell.
     
     Normally you would call L{get_pty} before this, in which case the
     shell will operate through the pty, and the channel will be connected
     to the stdin and stdout of the pty.
     
     When the shell exits, the channel will be closed and can't be reused.
     You must open a new channel if you wish to open another shell.
     
     @raise SSHException: if the request was rejected or the channel was
         closed
     """
     if self.closed or self.eof_received or self.eof_sent or not self.active:
         raise SSHException('Channel is not open')
     m = Message()
     m.add_byte(chr(MSG_CHANNEL_REQUEST))
     m.add_int(self.remote_chanid)
     m.add_string('shell')
     m.add_boolean(1)
     self._event_pending()
     self.transport._send_user_message(m)
     self._wait_for_event()

 def _parse_service_request(self, m):
     service = m.get_string()
     if self.transport.server_mode and (service == 'ssh-userauth'):
         # accepted
         m = Message()
         m.add_byte(chr(MSG_SERVICE_ACCEPT))
         m.add_string(service)
         self.transport._send_message(m)
         return
     # dunno this one
     self._disconnect_service_not_available()

 def _disconnect_no_more_auth(self):
     m = Message()
     m.add_byte(chr(MSG_DISCONNECT))
     m.add_int(DISCONNECT_NO_MORE_AUTH_METHODS_AVAILABLE)
     m.add_string('No more auth methods available')
     m.add_string('en')
     self.transport._send_message(m)
     self.transport.close()

 def _disconnect_service_not_available(self):
     m = Message()
     m.add_byte(chr(MSG_DISCONNECT))
     m.add_int(DISCONNECT_SERVICE_NOT_AVAILABLE)
     m.add_string('Service not available')
     m.add_string('en')
     self.transport._send_message(m)
     self.transport.close()

 def _close_internal(self):
     # you are holding the lock.
     if not self.active or self.closed:
         return None, None
     m1 = self._send_eof()
     m2 = Message()
     m2.add_byte(chr(MSG_CHANNEL_CLOSE))
     m2.add_int(self.remote_chanid)
     self._set_closed()
     # can't unlink from the Transport yet -- the remote side may still
     # try to send meta-data (exit-status, etc)
     return m1, m2

 def sign_ssh_data(self, rng, data):
     msg = Message()
     msg.add_byte(chr(SSH2_AGENTC_SIGN_REQUEST))
     msg.add_string(self.blob)
     msg.add_string(data)
     msg.add_int(0)
     ptype, result = self.agent._send_message(msg)
     if ptype != SSH2_AGENT_SIGN_RESPONSE:
         raise SSHException('key cannot be used for signing')
     return result.get_string()

 def start_kex(self):
     self._generate_x()
     if self.transport.server_mode:
         # compute f = g^x mod p, but don't send it yet
         self.f = pow(G, self.x, P)
         self.transport._expect_packet(_MSG_KEXDH_INIT)
         return
     # compute e = g^x mod p (where g=2), and send it
     self.e = pow(G, self.x, P)
     m = Message()
     m.add_byte(chr(_MSG_KEXDH_INIT))
     m.add_mpint(self.e)
     self.transport._send_message(m)
     self.transport._expect_packet(_MSG_KEXDH_REPLY)

 def _send_server_version(self):
     # winscp will freak out if the server sends version info before the
     # client finishes sending INIT.
     t, data = self._read_packet()
     if t != CMD_INIT:
         raise SFTPError('Incompatible sftp protocol')
     version = struct.unpack('>I', data[:4])[0]
     # advertise that we support "check-file"
     extension_pairs = [ 'check-file', 'md5,sha1' ]
     msg = Message()
     msg.add_int(_VERSION)
     msg.add(*extension_pairs)
     self._send_packet(CMD_VERSION, str(msg))
     return version

 def _parse_kexdh_gex_group(self, m):
     self.p = m.get_mpint()
     self.g = m.get_mpint()
     # reject if p's bit length < 1024 or > 8192
     bitlen = util.bit_length(self.p)
     if (bitlen < 1024) or (bitlen > 8192):
         raise SSHException('Server-generated gex p (don\'t ask) is out of range (%d bits)' % bitlen)
     self.transport._log(DEBUG, 'Got server p (%d bits)' % bitlen)
     self._generate_x()
     # now compute e = g^x mod p
     self.e = pow(self.g, self.x, self.p)
     m = Message()
     m.add_byte(chr(_MSG_KEXDH_GEX_INIT))
     m.add_mpint(self.e)
     self.transport._send_message(m)
     self.transport._expect_packet(_MSG_KEXDH_GEX_REPLY)

    def send(self, s):
        """
        Send data to the channel.  Returns the number of bytes sent, or 0 if
        the channel stream is closed.  Applications are responsible for
        checking that all data has been sent: if only some of the data was
        transmitted, the application needs to attempt delivery of the remaining
        data.

        @param s: data to send
        @type s: str
        @return: number of bytes actually sent
        @rtype: int

        @raise socket.timeout: if no data could be sent before the timeout set
            by L{settimeout}.
        """
        size = len(s)
        self.lock.acquire()
        try:
            size = self._wait_for_send_window(size)
            if size == 0:
                # eof or similar
                return 0
            m = Message()
            m.add_byte(chr(MSG_CHANNEL_DATA))
            m.add_int(self.remote_chanid)
            m.add_string(s[:size])
        finally:
            self.lock.release()
        # Note: We release self.lock before calling _send_user_message.
        # Otherwise, we can deadlock during re-keying.
        self.transport._send_user_message(m)
        return size

    def recv_stderr(self, nbytes):
        """
        Receive data from the channel's stderr stream.  Only channels using
        L{exec_command} or L{invoke_shell} without a pty will ever have data
        on the stderr stream.  The return value is a string representing the
        data received.  The maximum amount of data to be received at once is
        specified by C{nbytes}.  If a string of length zero is returned, the
        channel stream has closed.

        @param nbytes: maximum number of bytes to read.
        @type nbytes: int
        @return: data.
        @rtype: str
        
        @raise socket.timeout: if no data is ready before the timeout set by
            L{settimeout}.
        
        @since: 1.1
        """
        try:
            out = self.in_stderr_buffer.read(nbytes, self.timeout)
        except PipeTimeout as e:
            raise socket.timeout()
            
        ack = self._check_add_window(len(out))
        # no need to hold the channel lock when sending this
        if ack > 0:
            m = Message()
            m.add_byte(chr(MSG_CHANNEL_WINDOW_ADJUST))
            m.add_int(self.remote_chanid)
            m.add_int(ack)
            self.transport._send_user_message(m)

        return out

 def __bytes__(self):
     m = Message()
     m.add_string(b'ssh-dss')
     m.add_mpint(self.p)
     m.add_mpint(self.q)
     m.add_mpint(self.g)
     m.add_mpint(self.y)
     return bytes(m)

 def __str__(self):
     m = Message()
     m.add_string('ssh-dss')
     m.add_mpint(self.p)
     m.add_mpint(self.q)
     m.add_mpint(self.g)
     m.add_mpint(self.y)
     return str(m)

 def _negotiate_keys_wrapper(self, m):
     if self.local_kex_init is None: # Remote side sent KEXINIT
         # Simulate in-transit MSG_CHANNEL_WINDOW_ADJUST by sending it
         # before responding to the incoming MSG_KEXINIT.
         m2 = Message()
         m2.add_byte(chr(MSG_CHANNEL_WINDOW_ADJUST))
         m2.add_int(chan.remote_chanid)
         m2.add_int(1)    # bytes to add
         self._send_message(m2)
     return _negotiate_keys(self, m)

 def _parse_kexdh_gex_request_old(self, m):
     # same as above, but without min_bits or max_bits (used by older clients like putty)
     self.preferred_bits = m.get_int()
     # smoosh the user's preferred size into our own limits
     if self.preferred_bits > self.max_bits:
         self.preferred_bits = self.max_bits
     if self.preferred_bits < self.min_bits:
         self.preferred_bits = self.min_bits
     # generate prime
     pack = self.transport._get_modulus_pack()
     if pack is None:
         raise SSHException('Can\'t do server-side gex with no modulus pack')
     self.transport._log(DEBUG, 'Picking p (~ %d bits)' % (self.preferred_bits,))
     self.g, self.p = pack.get_modulus(self.min_bits, self.preferred_bits, self.max_bits)
     m = Message()
     m.add_byte(chr(_MSG_KEXDH_GEX_GROUP))
     m.add_mpint(self.p)
     m.add_mpint(self.g)
     self.transport._send_message(m)
     self.transport._expect_packet(_MSG_KEXDH_GEX_INIT)
     self.old_style = True