# Twisted, the Framework of Your Internet
# Copyright (C) 2001 Matthew W. Lefkowitz
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of version 2.1 of the GNU Lesser General Public
# License as published by the Free Software Foundation.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
"""TELNET implementation, with line-oriented command handling.
"""
# System Imports
import string
from cStringIO import StringIO
# Twisted Imports
from twisted import copyright
from twisted.python import log,failure
from twisted.internet import protocol
# Some utility chars.
ESC = chr(27) # ESC for doing fanciness
BOLD_MODE_ON = ESC+"[1m" # turn bold on
BOLD_MODE_OFF= ESC+"[m" # no char attributes
# Characters gleaned from the various (and conflicting) RFCs. Not all of these are correct.
NULL = chr(0) # No operation.
LF = chr(10) # Moves the printer to the
# next print line, keeping the
# same horizontal position.
CR = chr(13) # Moves the printer to the left
# margin of the current line.
BEL = chr(7) # Produces an audible or
# visible signal (which does
# NOT move the print head).
BS = chr(8) # Moves the print head one
# character position towards
# the left margin.
HT = chr(9) # Moves the printer to the
# next horizontal tab stop.
# It remains unspecified how
# either party determines or
# establishes where such tab
# stops are located.
VT = chr(11) # Moves the printer to the
# next vertical tab stop. It
# remains unspecified how
# either party determines or
# establishes where such tab
# stops are located.
FF = chr(12) # Moves the printer to the top
# of the next page, keeping
# the same horizontal position.
SE = chr(240) # End of subnegotiation parameters.
NOP= chr(241) # No operation.
DM = chr(242) # "Data Mark": The data stream portion
# of a Synch. This should always be
# accompanied by a TCP Urgent
# notification.
BRK= chr(243) # NVT character Break.
IP = chr(244) # The function Interrupt Process.
AO = chr(245) # The function Abort Output
AYT= chr(246) # The function Are You There.
EC = chr(247) # The function Erase Character.
EL = chr(248) # The function Erase Line
GA = chr(249) # The Go Ahead signal.
SB = chr(250) # Indicates that what follows is
# subnegotiation of the indicated
# option.
WILL = chr(251) # Indicates the desire to begin
# performing, or confirmation that
# you are now performing, the
# indicated option.
WONT = chr(252) # Indicates the refusal to perform,
# or continue performing, the
# indicated option.
DO = chr(253) # Indicates the request that the
# other party perform, or
# confirmation that you are expecting
# the other party to perform, the
# indicated option.
DONT = chr(254) # Indicates the demand that the
# other party stop performing,
# or confirmation that you are no
# longer expecting the other party
# to perform, the indicated option.
IAC = chr(255) # Data Byte 255.
# features
ECHO = chr(1) # User-to-Server: Asks the server to send
# Echos of the transmitted data.
# Server-to User: States that the server is
# sending echos of the transmitted data.
# Sent only as a reply to ECHO or NO ECHO.
SUPGA = chr(3) # Supress Go Ahead...? "Modern" telnet servers
# are supposed to do this.
LINEMODE = chr(34) # I don't care that Jon Postel is dead.
HIDE = chr(133) # The intention is that a server will send
# this signal to a user system which is
# echoing locally (to the user) when the user
# is about to type something secret (e.g. a
# password). In this case, the user system
# is to suppress local echoing or overprint
# the input (or something) until the server
# sends a NOECHO signal. In situations where
# the user system is not echoing locally,
# this signal must not be sent by the server.
NOECHO= chr(131) # User-to-Server: Asks the server not to
# return Echos of the transmitted data.
#
# Server-to-User: States that the server is
# not sending echos of the transmitted data.
# Sent only as a reply to ECHO or NO ECHO,
# or to end the hide your input.
iacBytes = {
DO: 'DO',
DONT: 'DONT',
WILL: 'WILL',
WONT: 'WONT',
IP: 'IP'
}
def multireplace(st, dct):
for k, v in dct.items():
st = string.replace(st, k, v)
return st
class Telnet(protocol.Protocol):
"""I am a Protocol for handling Telnet connections. I have two
sets of special methods, telnet_* and iac_*.
telnet_* methods get called on every line sent to me. The method
to call is decided by the current mode. The initial mode is 'User';
this means that telnet_User is the first telnet_* method to be called.
All telnet_* methods should return a string which specifies the mode
to go into next; thus dictating which telnet_* method to call next.
For example, the default telnet_User method returns 'Password' to go
into Password mode, and the default telnet_Password method returns
'Command' to go into Command mode.
The iac_* methods are less-used; they are called when an IAC telnet
byte is received. You can define iac_DO, iac_DONT, iac_WILL, iac_WONT,
and iac_IP methods to do what you want when one of these bytes is
received."""
gotIAC = 0
iacByte = None
lastLine = None
buffer = ''
echo = 0
delimiters = ['\r\n', '\r\000']
mode = "User"
def write(self, data):
"""Send the given data over my transport."""
self.transport.write(data)
def connectionMade(self):
"""I will write a welcomeMessage and loginPrompt to the client."""
self.write(self.welcomeMessage() + self.loginPrompt())
def welcomeMessage(self):
"""Override me to return a string which will be sent to the client
before login."""
x = self.factory.__class__
return ("\r\n" + x.__module__ + '.' + x.__name__ +
'\r\nTwisted %s\r\n' % copyright.version
)
def loginPrompt(self):
"""Override me to return a 'login:'-type prompt."""
return "username: "
def iacSBchunk(self, chunk):
pass
def iac_DO(self, feature):
pass
def iac_DONT(self, feature):
pass
def iac_WILL(self, feature):
pass
def iac_WONT(self, feature):
pass
def iac_IP(self, feature):
pass
def processLine(self, line):
"""I call a method that looks like 'telnet_*' where '*' is filled
in by the current mode. telnet_* methods should return a string which
will become the new mode."""
self.mode = getattr(self, "telnet_"+self.mode)(line)
def telnet_User(self, user):
"""I take a username, set it to the 'self.username' attribute,
print out a password prompt, and switch to 'Password' mode. If
you want to do something else when the username is received (ie,
create a new user if the user doesn't exist), override me."""
self.username = user
self.write(IAC+WILL+ECHO+"password: ")
return "Password"
def telnet_Password(self, paswd):
"""I accept a password as an argument, and check it with the
checkUserAndPass method. If the login is successful, I call
loggedIn()."""
self.write(IAC+WONT+ECHO+"*****\r\n")
if not self.checkUserAndPass(self.username, paswd):
return "Done"
self.loggedIn()
return "Command"
def telnet_Command(self, cmd):
"""The default 'command processing' mode. You probably want to
override me."""
return "Command"
def processChunk(self, chunk):
"""I take a chunk of data and delegate out to telnet_* methods
by way of processLine. If the current mode is 'Done', I'll close
the connection. """
self.buffer = self.buffer + chunk
#yech.
for delim in self.delimiters:
idx = string.find(self.buffer, delim)
if idx != -1:
break
while idx != -1:
buf, self.buffer = self.buffer[:idx], self.buffer[idx+2:]
self.processLine(buf)
if self.mode == 'Done':
self.transport.loseConnection()
for delim in self.delimiters:
idx = string.find(self.buffer, delim)
if idx != -1:
break
def dataReceived(self, data):
chunk = StringIO()
# silly little IAC state-machine
for char in data:
if self.gotIAC:
# working on an IAC request state
if self.iacByte:
# we're in SB mode, getting a chunk
if self.iacByte == SB:
if char == SE:
self.iacSBchunk(chunk.getvalue())
chunk = StringIO()
del self.iacByte
del self.gotIAC
else:
chunk.write(char)
else:
# got all I need to know state
try:
getattr(self, 'iac_%s' % iacBytes[self.iacByte])(char)
except KeyError:
pass
del self.iacByte
del self.gotIAC
else:
# got IAC, this is my W/W/D/D (or perhaps sb)
self.iacByte = char
elif char == IAC:
# Process what I've got so far before going into
# the IAC state; don't want to process characters
# in an inconsistent state with what they were
# received in.
c = chunk.getvalue()
if c:
why = self.processChunk(c)
if why:
return why
chunk = StringIO()
self.gotIAC = 1
else:
chunk.write(char)
# chunks are of a relatively indeterminate size.
c = chunk.getvalue()
if c:
why = self.processChunk(c)
if why:
return why
def loggedIn(self):
"""Called after the user succesfully logged in.
Override in subclasses.
"""
pass
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