Telnet server

1 files changed, 776 insertions, 0 deletions

diff --git a/telnetsrvlib.py b/telnetsrvlib.py
new file mode 100644
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--- /dev/null
+++ b/telnetsrvlib.py
@@ -0,0 +1,776 @@
+#!/usr/bin/python
+"""TELNET server class
+
+Based on the telnet client in telnetlib.py
+
+Presents a command line interface to the telnet client.
+Various settings can affect the operation of the server:
+
+	authCallback = Reference to authentication function. If
+                   there is none, no un/pw is requested. Should
+                   raise an exception if authentication fails
+                   Default: None
+	authNeedUser = Should a username be requested?
+                   Default: False
+	authNeedPass = Should a password be requested?
+                   Default: False
+	COMMANDS     = Dictionary of supported commands
+                   Key = command (Must be upper case)
+                   Value = List of (function, help text)
+                   Function.__doc__ should be long help
+				   Function.aliases may be a list of alternative spellings
+"""
+
+#from telnetlib import IAC, WILL, WONT, DO, DONT, ECHO, SGA, Telnet
+import threading
+import SocketServer
+import socket
+import time
+import sys
+import traceback
+import curses.ascii
+import curses.has_key
+import curses
+import logging
+import re
+if not hasattr(socket, 'SHUT_RDWR'):
+	socket.SHUT_RDWR = 2
+
+__all__ = ["TelnetHandler", "TelnetCLIHandler"]
+
+IAC  = chr(255) # "Interpret As Command"
+DONT = chr(254)
+DO   = chr(253)
+WONT = chr(252)
+WILL = chr(251)
+theNULL = chr(0)
+
+SE  = chr(240)  # Subnegotiation End
+NOP = chr(241)  # No Operation
+DM  = chr(242)  # Data Mark
+BRK = chr(243)  # Break
+IP  = chr(244)  # Interrupt process
+AO  = chr(245)  # Abort output
+AYT = chr(246)  # Are You There
+EC  = chr(247)  # Erase Character
+EL  = chr(248)  # Erase Line
+GA  = chr(249)  # Go Ahead
+SB =  chr(250)  # Subnegotiation Begin
+
+BINARY = chr(0) # 8-bit data path
+ECHO = chr(1) # echo
+RCP = chr(2) # prepare to reconnect
+SGA = chr(3) # suppress go ahead
+NAMS = chr(4) # approximate message size
+STATUS = chr(5) # give status
+TM = chr(6) # timing mark
+RCTE = chr(7) # remote controlled transmission and echo
+NAOL = chr(8) # negotiate about output line width
+NAOP = chr(9) # negotiate about output page size
+NAOCRD = chr(10) # negotiate about CR disposition
+NAOHTS = chr(11) # negotiate about horizontal tabstops
+NAOHTD = chr(12) # negotiate about horizontal tab disposition
+NAOFFD = chr(13) # negotiate about formfeed disposition
+NAOVTS = chr(14) # negotiate about vertical tab stops
+NAOVTD = chr(15) # negotiate about vertical tab disposition
+NAOLFD = chr(16) # negotiate about output LF disposition
+XASCII = chr(17) # extended ascii character set
+LOGOUT = chr(18) # force logout
+BM = chr(19) # byte macro
+DET = chr(20) # data entry terminal
+SUPDUP = chr(21) # supdup protocol
+SUPDUPOUTPUT = chr(22) # supdup output
+SNDLOC = chr(23) # send location
+TTYPE = chr(24) # terminal type
+EOR = chr(25) # end or record
+TUID = chr(26) # TACACS user identification
+OUTMRK = chr(27) # output marking
+TTYLOC = chr(28) # terminal location number
+VT3270REGIME = chr(29) # 3270 regime
+X3PAD = chr(30) # X.3 PAD
+NAWS = chr(31) # window size
+TSPEED = chr(32) # terminal speed
+LFLOW = chr(33) # remote flow control
+LINEMODE = chr(34) # Linemode option
+XDISPLOC = chr(35) # X Display Location
+OLD_ENVIRON = chr(36) # Old - Environment variables
+AUTHENTICATION = chr(37) # Authenticate
+ENCRYPT = chr(38) # Encryption option
+NEW_ENVIRON = chr(39) # New - Environment variables
+# the following ones come from
+# http://www.iana.org/assignments/telnet-options
+# Unfortunately, that document does not assign identifiers
+# to all of them, so we are making them up
+TN3270E = chr(40) # TN3270E
+XAUTH = chr(41) # XAUTH
+CHARSET = chr(42) # CHARSET
+RSP = chr(43) # Telnet Remote Serial Port
+COM_PORT_OPTION = chr(44) # Com Port Control Option
+SUPPRESS_LOCAL_ECHO = chr(45) # Telnet Suppress Local Echo
+TLS = chr(46) # Telnet Start TLS
+KERMIT = chr(47) # KERMIT
+SEND_URL = chr(48) # SEND-URL
+FORWARD_X = chr(49) # FORWARD_X
+PRAGMA_LOGON = chr(138) # TELOPT PRAGMA LOGON
+SSPI_LOGON = chr(139) # TELOPT SSPI LOGON
+PRAGMA_HEARTBEAT = chr(140) # TELOPT PRAGMA HEARTBEAT
+EXOPL = chr(255) # Extended-Options-List
+NOOPT = chr(0)
+
+#Codes used in SB SE data stream for terminal type negotiation
+IS = chr(0)
+SEND = chr(1)
+
+CMDS = {
+	WILL: 'WILL',
+	WONT: 'WONT',
+	DO: 'DO',
+	DONT: 'DONT',
+	SE: 'Subnegotiation End',
+	NOP: 'No Operation',
+	DM: 'Data Mark',
+	BRK: 'Break',
+	IP: 'Interrupt process',
+	AO: 'Abort output',
+	AYT: 'Are You There',
+	EC: 'Erase Character',
+	EL: 'Erase Line',
+	GA: 'Go Ahead',
+	SB: 'Subnegotiation Begin',
+	BINARY: 'Binary',
+	ECHO: 'Echo',
+	RCP: 'Prepare to reconnect',
+	SGA: 'Suppress Go-Ahead',
+	NAMS: 'Approximate message size',
+	STATUS: 'Give status',
+	TM: 'Timing mark',
+	RCTE: 'Remote controlled transmission and echo',
+	NAOL: 'Negotiate about output line width',
+	NAOP: 'Negotiate about output page size',
+	NAOCRD: 'Negotiate about CR disposition',
+	NAOHTS: 'Negotiate about horizontal tabstops',
+	NAOHTD: 'Negotiate about horizontal tab disposition',
+	NAOFFD: 'Negotiate about formfeed disposition',
+	NAOVTS: 'Negotiate about vertical tab stops',
+	NAOVTD: 'Negotiate about vertical tab disposition',
+	NAOLFD: 'Negotiate about output LF disposition',
+	XASCII: 'Extended ascii character set',
+	LOGOUT: 'Force logout',
+	BM: 'Byte macro',
+	DET: 'Data entry terminal',
+	SUPDUP: 'Supdup protocol',
+	SUPDUPOUTPUT: 'Supdup output',
+	SNDLOC: 'Send location',
+	TTYPE: 'Terminal type',
+	EOR: 'End or record',
+	TUID: 'TACACS user identification',
+	OUTMRK: 'Output marking',
+	TTYLOC: 'Terminal location number',
+	VT3270REGIME: '3270 regime',
+	X3PAD: 'X.3 PAD',
+	NAWS: 'Window size',
+	TSPEED: 'Terminal speed',
+	LFLOW: 'Remote flow control',
+	LINEMODE: 'Linemode option',
+	XDISPLOC: 'X Display Location',
+	OLD_ENVIRON: 'Old - Environment variables',
+	AUTHENTICATION: 'Authenticate',
+	ENCRYPT: 'Encryption option',
+	NEW_ENVIRON: 'New - Environment variables',
+}
+
+class TelnetHandler(SocketServer.BaseRequestHandler):
+	"A telnet server based on the client in telnetlib"
+
+	# What I am prepared to do?
+	DOACK = {
+		ECHO: WILL,
+		SGA: WILL,
+		NEW_ENVIRON: WONT,
+	}
+	# What do I want the client to do?
+	WILLACK = {
+		ECHO: DONT,
+		SGA: DO,
+		NAWS: DONT,
+		TTYPE: DO,
+		LINEMODE: DONT,
+		NEW_ENVIRON: DO,
+	}
+	# Default terminal type - used if client doesn't tell us its termtype
+	TERM = "ansi"
+	# Keycode to name mapping - used to decide which keys to query
+	KEYS = {					# Key escape sequences
+		curses.KEY_UP: 'Up',			# Cursor up
+		curses.KEY_DOWN: 'Down',		# Cursor down
+		curses.KEY_LEFT: 'Left',		# Cursor left
+		curses.KEY_RIGHT: 'Right',		# Cursor right
+		curses.KEY_DC: 'Delete',		# Delete right
+		curses.KEY_BACKSPACE: 'Backspace',	# Delete left
+	}
+	# Reverse mapping of KEYS - used for cooking key codes
+	ESCSEQ = {
+	}
+	# Terminal output escape sequences
+	CODES = {
+		'DEOL': '',	# Delete to end of line
+		'DEL': '',	# Delete and close up
+		'INS': '',	# Insert space
+		'CSRLEFT': '',	# Move cursor left 1 space
+		'CSRRIGHT': '', # Move cursor right 1 space
+	}
+	# What prompt to display
+	PROMPT = "Telnet Server> "
+	# The function to call to verify authentication data
+	authCallback = None
+	# Does authCallback want a username?
+	authNeedUser = False
+	# Does authCallback want a password?
+	authNeedPass = False
+
+# --------------------------- Environment Setup ----------------------------
+
+	def __init__(self, request, client_address, server):
+		"""Constructor.
+
+		When called without arguments, create an unconnected instance.
+		With a hostname argument, it connects the instance; a port
+		number is optional.
+		"""
+		# Am I doing the echoing?
+		self.DOECHO = True
+		# What opts have I sent DO/DONT for and what did I send?
+		self.DOOPTS = {}
+		# What opts have I sent WILL/WONT for and what did I send?
+		self.WILLOPTS = {}
+		# What commands does this CLI support
+		self.COMMANDS = {}
+		self.sock = None	# TCP socket
+		self.rawq = ''		# Raw input string
+		self.cookedq = []	# This is the cooked input stream (list of charcodes)
+		self.sbdataq = ''	# Sub-Neg string
+		self.eof = 0		# Has EOF been reached?
+		self.iacseq = ''	# Buffer for IAC sequence.
+		self.sb = 0		# Flag for SB and SE sequence.
+		self.history = []	# Command history
+		self.IQUEUELOCK = threading.Lock()
+		self.OQUEUELOCK = threading.Lock()
+		self.RUNSHELL = True
+		# A little magic - Everything called cmdXXX is a command
+		for k in dir(self):
+			if k[:3] == 'cmd':
+				name = k[3:]
+				method = getattr(self, k)
+				self.COMMANDS[name] = method
+				for alias in getattr(method, "aliases", []):
+					self.COMMANDS[alias] = self.COMMANDS[name]
+		SocketServer.BaseRequestHandler.__init__(self, request, client_address, server)
+
+	def setterm(self, term):
+		"Set the curses structures for this terminal"
+		logging.debug("Setting termtype to %s" % (term, ))
+		curses.setupterm(term) # This will raise if the termtype is not supported
+		self.TERM = term
+		self.ESCSEQ = {}
+		for k in self.KEYS.keys():
+			str = curses.tigetstr(curses.has_key._capability_names[k])
+			if str:
+				self.ESCSEQ[str] = k
+		self.CODES['DEOL'] = curses.tigetstr('el')
+		self.CODES['DEL'] = curses.tigetstr('dch1')
+		self.CODES['INS'] = curses.tigetstr('ich1')
+		self.CODES['CSRLEFT'] = curses.tigetstr('cub1')
+		self.CODES['CSRRIGHT'] = curses.tigetstr('cuf1')
+
+	def setup(self):
+		"Connect incoming connection to a telnet session"
+		self.setterm(self.TERM)
+		self.sock = self.request._sock
+		for k in self.DOACK.keys():
+			self.sendcommand(self.DOACK[k], k)
+		for k in self.WILLACK.keys():
+			self.sendcommand(self.WILLACK[k], k)
+		self.thread_ic = threading.Thread(target=self.inputcooker)
+		self.thread_ic.setDaemon(True)
+		self.thread_ic.start()
+		# Sleep for 0.5 second to allow options negotiation
+		time.sleep(0.5)
+
+	def finish(self):
+		"End this session"
+		self.sock.shutdown(socket.SHUT_RDWR)
+
+# ------------------------- Telnet Options Engine --------------------------
+
+	def options_handler(self, sock, cmd, opt):
+		"Negotiate options"
+#		if CMDS.has_key(cmd):
+#			cmdtxt = CMDS[cmd]
+#		else:
+#			cmdtxt = "cmd:%d" % ord(cmd)
+#		if cmd in [WILL, WONT, DO, DONT]:
+#			if CMDS.has_key(opt):
+#				opttxt = CMDS[opt]
+#			else:
+#				opttxt = "opt:%d" % ord(opt)
+#		else:
+#			opttxt = ""
+#		logging.debug("OPTION: %s %s" % (cmdtxt, opttxt, ))
+		if cmd == NOP:
+			self.sendcommand(NOP)
+		elif cmd == WILL or cmd == WONT:
+			if self.WILLACK.has_key(opt):
+				self.sendcommand(self.WILLACK[opt], opt)
+			else:
+				self.sendcommand(DONT, opt)
+			if cmd == WILL and opt == TTYPE:
+				self.writecooked(IAC + SB + TTYPE + SEND + IAC + SE)
+		elif cmd == DO or cmd == DONT:
+			if self.DOACK.has_key(opt):
+				self.sendcommand(self.DOACK[opt], opt)
+			else:
+				self.sendcommand(WONT, opt)
+			if opt == ECHO:
+				self.DOECHO = (cmd == DO)
+		elif cmd == SE:
+			subreq = self.read_sb_data()
+			if subreq[0] == TTYPE and subreq[1] == IS:
+				try:
+					self.setterm(subreq[2:])
+				except:
+					logging.debug("Terminal type not known")
+		elif cmd == SB:
+			pass
+		else:
+			logging.debug("Unhandled option: %s %s" % (cmdtxt, opttxt, ))
+
+	def sendcommand(self, cmd, opt=None):
+		"Send a telnet command (IAC)"
+#		if CMDS.has_key(cmd):
+#			cmdtxt = CMDS[cmd]
+#		else:
+#			cmdtxt = "cmd:%d" % ord(cmd)
+#		if opt == None:
+#			opttxt = ''
+#		else:
+#			if CMDS.has_key(opt):
+#				opttxt = CMDS[opt]
+#			else:
+#				opttxt = "opt:%d" % ord(opt)
+		if cmd in [DO, DONT]:
+			if not self.DOOPTS.has_key(opt):
+				self.DOOPTS[opt] = None
+			if (((cmd == DO) and (self.DOOPTS[opt] != True))
+			or ((cmd == DONT) and (self.DOOPTS[opt] != False))):
+#				logging.debug("Sending %s %s" % (cmdtxt, opttxt, ))
+				self.DOOPTS[opt] = (cmd == DO)
+				self.writecooked(IAC + cmd + opt)
+#			else:
+#				logging.debug("Not resending %s %s" % (cmdtxt, opttxt, ))
+		elif cmd in [WILL, WONT]:
+			if not self.WILLOPTS.has_key(opt):
+				self.WILLOPTS[opt] = ''
+			if (((cmd == WILL) and (self.WILLOPTS[opt] != True))
+			or ((cmd == WONT) and (self.WILLOPTS[opt] != False))):
+#				logging.debug("Sending %s %s" % (cmdtxt, opttxt, ))
+				self.WILLOPTS[opt] = (cmd == WILL)
+				self.writecooked(IAC + cmd + opt)
+#			else:
+#				logging.debug("Not resending %s %s" % (cmdtxt, opttxt, ))
+		else:
+			self.writecooked(IAC + cmd)
+
+	def read_sb_data(self):
+		"""Return any data available in the SB ... SE queue.
+
+		Return '' if no SB ... SE available. Should only be called
+		after seeing a SB or SE command. When a new SB command is
+		found, old unread SB data will be discarded. Don't block.
+
+		"""
+		buf = self.sbdataq
+		self.sbdataq = ''
+		return buf
+
+# ---------------------------- Input Functions -----------------------------
+
+	def _readline_echo(self, char, echo):
+		"""Echo a recieved character, move cursor etc..."""
+		if echo == True or (echo == None and self.DOECHO == True):
+			self.write(char)
+
+	def readline(self, echo=None):
+		"""Return a line of text, including the terminating LF
+		   If echo is true always echo, if echo is false never echo
+		   If echo is None follow the negotiated setting.
+		"""
+		line = []
+		insptr = 0
+		histptr = len(self.history)
+		while True:
+			c = self.getc(block=True)
+			if c == theNULL:
+				continue
+			elif c == curses.KEY_LEFT:
+				if insptr > 0:
+					insptr = insptr - 1
+					self._readline_echo(self.CODES['CSRLEFT'], echo)
+				else:
+					self._readline_echo(chr(7), echo)
+				continue
+			elif c == curses.KEY_RIGHT:
+				if insptr < len(line):
+					insptr = insptr + 1
+					self._readline_echo(self.CODES['CSRRIGHT'], echo)
+				else:
+					self._readline_echo(chr(7), echo)
+				continue
+			elif c == curses.KEY_UP or c == curses.KEY_DOWN:
+				if c == curses.KEY_UP:
+					if histptr > 0:
+						histptr = histptr - 1
+					else:
+						self._readline_echo(chr(7), echo)
+						continue
+				elif c == curses.KEY_DOWN:
+					if histptr < len(self.history):
+						histptr = histptr + 1
+					else:
+						self._readline_echo(chr(7), echo)
+						continue
+				line = []
+				if histptr < len(self.history):
+					line.extend(self.history[histptr])
+				for char in range(insptr):
+					self._readline_echo(self.CODES['CSRLEFT'], echo)
+				self._readline_echo(self.CODES['DEOL'], echo)
+				self._readline_echo(''.join(line), echo)
+				insptr = len(line)
+				continue
+			elif c == chr(3):
+				self._readline_echo('\n' + curses.ascii.unctrl(c) + ' ABORT\n', echo)
+				return ''
+			elif c == chr(4):
+				if len(line) > 0:
+					self._readline_echo('\n' + curses.ascii.unctrl(c) + ' ABORT (QUIT)\n', echo)
+					return ''
+				self._readline_echo('\n' + curses.ascii.unctrl(c) + ' QUIT\n', echo)
+				return 'QUIT'
+			elif c == chr(10):
+				self._readline_echo(c, echo)
+				if echo == True or (echo == None and self.DOECHO == True):
+					self.history.append(line)
+				return ''.join(line)
+			elif c == curses.KEY_BACKSPACE or c == chr(127) or c == chr(8):
+				if insptr > 0:
+					self._readline_echo(self.CODES['CSRLEFT'] + self.CODES['DEL'], echo)
+					insptr = insptr - 1
+					del line[insptr]
+				else:
+					self._readline_echo(chr(7), echo)
+				continue
+			elif c == curses.KEY_DC:
+				if insptr < len(line):
+					self._readline_echo(self.CODES['DEL'], echo)
+					del line[insptr]
+				else:
+					self._readline_echo(chr(7), echo)
+				continue
+			else:
+				if ord(c) < 32:
+					c = curses.ascii.unctrl(c)
+				self._readline_echo(c, echo)
+			line[insptr:insptr] = c
+			insptr = insptr + len(c)
+
+	def getc(self, block=True):
+		"""Return one character from the input queue"""
+		if not block:
+			if not len(self.cookedq):
+				return ''
+		while not len(self.cookedq):
+			time.sleep(0.05)
+		self.IQUEUELOCK.acquire()
+		ret = self.cookedq[0]
+		self.cookedq = self.cookedq[1:]
+		self.IQUEUELOCK.release()
+		return ret
+
+# --------------------------- Output Functions -----------------------------
+
+	def writeline(self, text):
+		"""Send a packet with line ending."""
+		self.write(text+chr(10))
+
+	def write(self, text):
+		"""Send a packet to the socket. This function cooks output."""
+		text = text.replace(IAC, IAC+IAC)
+		text = text.replace(chr(10), chr(13)+chr(10))
+		self.writecooked(text)
+
+	def writecooked(self, text):
+		"""Put data directly into the output queue (bypass output cooker)"""
+		self.OQUEUELOCK.acquire()
+		self.sock.sendall(text)
+		self.OQUEUELOCK.release()
+
+# ------------------------------- Input Cooker -----------------------------
+
+	def _inputcooker_getc(self, block=True):
+		"""Get one character from the raw queue. Optionally blocking.
+		Raise EOFError on end of stream. SHOULD ONLY BE CALLED FROM THE
+		INPUT COOKER."""
+		if self.rawq:
+			ret = self.rawq[0]
+			self.rawq = self.rawq[1:]
+			return ret
+		if not block:
+			if select.select([self.sock.fileno()], [], [], 0) == ([], [], []):
+				return ''
+		ret = self.sock.recv(20)
+		self.eof = not(ret)
+		self.rawq = self.rawq + ret
+		if self.eof:
+			raise EOFError
+		return self._inputcooker_getc(block)
+
+	def _inputcooker_ungetc(self, char):
+		"""Put characters back onto the head of the rawq. SHOULD ONLY
+		BE CALLED FROM THE INPUT COOKER."""
+		self.rawq = char + self.rawq
+
+	def _inputcooker_store(self, char):
+		"""Put the cooked data in the correct queue (with locking)"""
+		if self.sb:
+			self.sbdataq = self.sbdataq + char
+		else:
+			self.IQUEUELOCK.acquire()
+			if type(char) in [type(()), type([]), type("")]:
+				for v in char:
+					self.cookedq.append(v)
+			else:
+				self.cookedq.append(char)
+			self.IQUEUELOCK.release()
+
+	def inputcooker(self):
+		"""Input Cooker - Transfer from raw queue to cooked queue.
+
+		Set self.eof when connection is closed.  Don't block unless in
+		the midst of an IAC sequence.
+		"""
+		try:
+			while True:
+				c = self._inputcooker_getc()
+				if not self.iacseq:
+					if c == IAC:
+						self.iacseq += c
+						continue
+					elif c == chr(13) and not(self.sb):
+						c2 = self._inputcooker_getc(block=False)
+						if c2 == theNULL or c2 == '':
+							c = chr(10)
+						elif c2 == chr(10):
+							c = c2
+						else:
+							self._inputcooker_ungetc(c2)
+							c = chr(10)
+					elif c in [x[0] for x in self.ESCSEQ.keys()]:
+						'Looks like the begining of a key sequence'
+						codes = c
+						for keyseq in self.ESCSEQ.keys():
+							if len(keyseq) == 0:
+								continue
+							while codes == keyseq[:len(codes)] and len(codes) <= keyseq:
+								if codes == keyseq:
+									c = self.ESCSEQ[keyseq]
+									break
+								codes = codes + self._inputcooker_getc()
+							if codes == keyseq:
+								break
+							self._inputcooker_ungetc(codes[1:])
+							codes = codes[0]
+					self._inputcooker_store(c)
+				elif len(self.iacseq) == 1:
+					'IAC: IAC CMD [OPTION only for WILL/WONT/DO/DONT]'
+					if c in (DO, DONT, WILL, WONT):
+						self.iacseq += c
+						continue
+					self.iacseq = ''
+					if c == IAC:
+						self._inputcooker_store(c)
+					else:
+						if c == SB: # SB ... SE start.
+							self.sb = 1
+							self.sbdataq = ''
+	#							continue
+						elif c == SE: # SB ... SE end.
+							self.sb = 0
+						# Callback is supposed to look into
+						# the sbdataq
+						self.options_handler(self.sock, c, NOOPT)
+				elif len(self.iacseq) == 2:
+					cmd = self.iacseq[1]
+					self.iacseq = ''
+					if cmd in (DO, DONT, WILL, WONT):
+						self.options_handler(self.sock, cmd, c)
+		except EOFError:
+			pass
+
+# ------------------------------- Basic Commands ---------------------------
+
+# Format of docstrings for command methods:
+# Line 0:  Command paramater(s) if any. (Can be blank line)
+# Line 1:  Short descriptive text. (Mandatory)
+# Line 2+: Long descriptive text. (Can be blank line)
+
+	def cmdHELP(self, params):
+		"""[<command>]
+		Display help
+		Display either brief help on all commands, or detailed
+		help on a single command passed as a parameter.
+		"""
+		if params:
+			cmd = params[0].upper()
+			if self.COMMANDS.has_key(cmd):
+				method = self.COMMANDS[cmd]
+				doc = method.__doc__.split("\n")
+				docp = doc[0].strip()
+				docl = '\n'.join(doc[2:]).replace("\n\t\t", " ").replace("\t", "").strip()
+				if len(docl) < 4:
+					docl = doc[1].strip()
+				self.writeline(
+					"%s %s\n\n%s" % (
+						cmd,
+						docp,
+						docl,
+					)
+				)
+				return
+			else:
+				self.writeline("Command '%s' not known" % cmd)
+		else:
+			self.writeline("Help on built in commands\n")
+		keys = self.COMMANDS.keys()
+		keys.sort()
+		for cmd in keys:
+			method = self.COMMANDS[cmd]
+			doc = method.__doc__.split("\n")
+			docp = doc[0].strip()
+			docs = doc[1].strip()
+			if len(docp) > 0:
+				docps = "%s - %s" % (docp, docs, )
+			else:
+				docps = "- %s" % (docs, )
+			self.writeline(
+				"%s %s" % (
+					cmd,
+					docps,
+				)
+			)
+	cmdHELP.aliases = ['?']
+
+	def cmdEXIT(self, params):
+		"""
+		Exit the command shell
+		"""
+		self.RUNSHELL = False
+		self.writeline("Goodbye")
+	cmdEXIT.aliases = ['QUIT', 'BYE', 'LOGOUT']
+
+	def cmdDEBUG(self, params):
+		"""
+		Display some debugging data
+		"""
+		for (v,k) in self.ESCSEQ.items():
+			line = '%-10s : ' % (self.KEYS[k], )
+			for c in v:
+				if ord(c)<32 or ord(c)>126:
+					line = line + curses.ascii.unctrl(c)
+				else:
+					line = line + c
+			self.writeline(line)
+
+	def cmdHISTORY(self, params):
+		"""
+		Display the command history
+		"""
+		cnt = 0
+		self.writeline('Command history\n')
+		for line in self.history:
+			cnt = cnt + 1
+			self.writeline("%-5d : %s" % (cnt, ''.join(line)))
+
+# ----------------------- Command Line Processor Engine --------------------
+
+	def handleException(self, exc_type, exc_param, exc_tb):
+		"Exception handler (False to abort)"
+		self.writeline(traceback.format_exception_only(exc_type, exc_param)[-1])
+		return True
+
+	def handle(self):
+		"The actual service to which the user has connected."
+		username = None
+		password = None
+		if self.authCallback:
+			if self.authNeedUser:
+				if self.DOECHO:
+					self.write("Username: ")
+				username = self.readline()
+			if self.authNeedPass:
+				if self.DOECHO:
+					self.write("Password: ")
+				password = self.readline(echo=False)
+				if self.DOECHO:
+					self.write("\n")
+			try:
+				self.authCallback(username, password)
+			except:
+				return
+		while self.RUNSHELL:
+			if self.DOECHO:
+				self.write(self.PROMPT)
+			cmdlist = [item.strip() for item in self.readline().split()]
+			idx = 0
+			while idx < (len(cmdlist) - 1):
+				if cmdlist[idx][0] in ["'", '"']:
+					cmdlist[idx] = cmdlist[idx] + " " + cmdlist.pop(idx+1)
+					if cmdlist[idx][0] != cmdlist[idx][-1]:
+						continue
+					cmdlist[idx] = cmdlist[idx][1:-1]
+				idx = idx + 1
+			if cmdlist:
+				cmd = cmdlist[0].upper()
+				params = cmdlist[1:]
+				if self.COMMANDS.has_key(cmd):
+					try:
+						self.COMMANDS[cmd](params)
+					except:
+						(t, p, tb) = sys.exc_info()
+						if self.handleException(t, p, tb):
+							break
+				else:
+					self.write("Unknown command '%s'\n" % cmd)
+		logging.debug("Exiting handler")
+
+if __name__ == '__main__':
+	"Testing - Accept a single connection"
+	class TNS(SocketServer.TCPServer):
+		allow_reuse_address = True
+
+	class TNH(TelnetHandler):
+		def cmdECHO(self, params):
+			""" [<arg> ...]
+			Echo parameters
+			Echo command line parameters back to user, one per line.
+			"""
+			self.writeline("Parameters:")
+			for item in params:
+				self.writeline("\t%s" % item)
+
+	logging.getLogger('').setLevel(logging.DEBUG)
+
+	tns = TNS(("0.0.0.0", 23), TNH)
+	tns.serve_forever()
+
+# vim: set syntax=python ai showmatch:
+