#!/usr/bin/env python3 # -*- coding: utf-8 -*- # # Copyright (C) 2013, 2014 James E. Carpenter # # This program is free software: you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation, either version 3 of the License, or # (at your option) any later version. # # This program 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 General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program. If not, see . # import socket import sys import os import select import fcntl import struct import termios import tty import time import argparse import traceback import logging log = logging.getLogger(__name__) # Escape characters ESC_CHAR = '^^' # can be overriden from command line ESC_QUIT = 'q' # IOU seems to only send *1* byte at a time. If # they ever fix that we'll be ready for it. BUFFER_SIZE = 1024 # How long to wait before retrying a connection (seconds) RETRY_DELAY = 3 # How often to test an idle connection (seconds) POLL_TIMEOUT = 3 EXIT_SUCCESS = 0 EXIT_FAILURE = 1 EXIT_ABORT = 2 # Mostly from: # https://code.google.com/p/miniboa/source/browse/trunk/miniboa/telnet.py # --[ Telnet Commands ]--------------------------------------------------------- SE = 240 # End of sub-negotiation parameters NOP = 241 # No operation DATMK = 242 # Data stream portion of a sync. BREAK = 243 # NVT Character BRK IP = 244 # Interrupt Process AO = 245 # Abort Output AYT = 246 # Are you there EC = 247 # Erase Character EL = 248 # Erase Line GA = 249 # The Go Ahead Signal SB = 250 # Sub-option to follow WILL = 251 # Will; request or confirm option begin WONT = 252 # Wont; deny option request DO = 253 # Do = Request or confirm remote option DONT = 254 # Don't = Demand or confirm option halt IAC = 255 # Interpret as Command SEND = 1 # Sub-process negotiation SEND command IS = 0 # Sub-process negotiation IS command # --[ Telnet Options ]---------------------------------------------------------- BINARY = 0 # Transmit Binary ECHO = 1 # Echo characters back to sender RECON = 2 # Reconnection SGA = 3 # Suppress Go-Ahead TMARK = 6 # Timing Mark TTYPE = 24 # Terminal Type NAWS = 31 # Negotiate About Window Size LINEMO = 34 # Line Mode class FileLock: # struct flock { /* from fcntl(2) */ # ... # short l_type; /* Type of lock: F_RDLCK, # F_WRLCK, F_UNLCK */ # short l_whence; /* How to interpret l_start: # SEEK_SET, SEEK_CUR, SEEK_END */ # off_t l_start; /* Starting offset for lock */ # off_t l_len; /* Number of bytes to lock */ # pid_t l_pid; /* PID of process blocking our lock # (F_GETLK only) */ # ... # }; _flock = struct.Struct('hhqql') def __init__(self, fname=None): self.fd = None self.fname = fname def get_lock(self): flk = self._flock.pack(fcntl.F_WRLCK, os.SEEK_SET, 0, 0, os.getpid()) flk = self._flock.unpack( fcntl.fcntl(self.fd, fcntl.F_GETLK, flk)) # If it's not locked (or is locked by us) then return None, # otherwise return the PID of the owner. if flk[0] == fcntl.F_UNLCK: return None return flk[4] def lock(self): try: self.fd = open('{}.lck'.format(self.fname), 'a') except Exception as e: raise LockError("Couldn't get lock on {}: {}" .format(self.fname, e)) flk = self._flock.pack(fcntl.F_WRLCK, os.SEEK_SET, 0, 0, 0) try: fcntl.fcntl(self.fd, fcntl.F_SETLK, flk) except BlockingIOError: raise LockError("Already connected. PID {} has lock on {}" .format(self.get_lock(), self.fname)) # If we got here then we must have the lock. Store the PID. self.fd.truncate(0) self.fd.write('{}\n'.format(os.getpid())) self.fd.flush() def unlock(self): if self.fd: # Deleting first prevents a race condition try: os.unlink(self.fd.name) except FileNotFoundError as e: log.debug("{}".format(e)) self.fd.close() def __enter__(self): self.lock() def __exit__(self, exc_type, exc_val, exc_tb): self.unlock() return False class Console: def fileno(self): raise NotImplementedError("Only routers have fileno()") class Router: pass class TTY(Console): def read(self, fileno, bufsize): return self.fd.read(bufsize) def write(self, buf): return self.fd.write(buf) def register(self, epoll): self.epoll = epoll epoll.register(self.fd, select.EPOLLIN | select.EPOLLET) def __enter__(self): try: self.fd = open('/dev/tty', 'r+b', buffering=0) except OSError as e: raise TTYError("Couldn't open controlling TTY: {}".format(e)) # Save original flags self.termios = termios.tcgetattr(self.fd) self.fcntl = fcntl.fcntl(self.fd, fcntl.F_GETFL) # Update flags tty.setraw(self.fd, termios.TCSANOW) fcntl.fcntl(self.fd, fcntl.F_SETFL, self.fcntl | os.O_NONBLOCK) return self def __exit__(self, exc_type, exc_val, exc_tb): # Restore flags to original settings termios.tcsetattr(self.fd, termios.TCSANOW, self.termios) fcntl.fcntl(self.fd, fcntl.F_SETFL, self.fcntl) self.fd.close() return False class TelnetServer(Console): def __init__(self, addr, port, stop_event): self.addr = addr self.port = port self.fd_dict = {} self.stop_event = stop_event def read(self, fileno, bufsize): # Someone wants to connect? if fileno == self.sock_fd.fileno(): self._accept() return None self._cur_fileno = fileno # Read a maximum of _bufsize_ bytes without blocking. When it # would want to block it means there's no more data. An empty # buffer normally means that we've been disconnected. try: buf = self._read_cur(bufsize, socket.MSG_DONTWAIT) except BlockingIOError: return None except ConnectionResetError: buf = b'' if not buf: self._disconnect(fileno) # Process and remove any telnet commands from the buffer if IAC in buf: buf = self._IAC_parser(buf) return buf def write(self, buf): for fd in self.fd_dict.values(): fd.send(buf) def register(self, epoll): self.epoll = epoll epoll.register(self.sock_fd, select.EPOLLIN) def _read_block(self, bufsize): buf = self._read_cur(bufsize, socket.MSG_WAITALL) # If we don't get everything we were looking for then the # client probably disconnected. if len(buf) < bufsize: self._disconnect(self._cur_fileno) return buf def _read_cur(self, bufsize, flags): return self.fd_dict[self._cur_fileno].recv(bufsize, flags) def _write_cur(self, buf): return self.fd_dict[self._cur_fileno].send(buf) def _IAC_parser(self, buf): skip_to = 0 while not self.stop_event.is_set(): # Locate an IAC to process iac_loc = buf.find(IAC, skip_to) if iac_loc < 0: break # Get the TELNET command iac_cmd = bytearray([IAC]) try: iac_cmd.append(buf[iac_loc + 1]) except IndexError: buf.extend(self._read_block(1)) iac_cmd.append(buf[iac_loc + 1]) # Is this just a 2-byte TELNET command? if iac_cmd[1] not in [WILL, WONT, DO, DONT]: if iac_cmd[1] == AYT: log.debug("Telnet server received Are-You-There (AYT)") self._write_cur( b'\r\nYour Are-You-There received. I am here.\r\n' ) elif iac_cmd[1] == IAC: # It's data, not an IAC iac_cmd.pop() # This prevents the 0xff from being # interputed as yet another IAC skip_to = iac_loc + 1 log.debug("Received IAC IAC") elif iac_cmd[1] == NOP: pass else: log.debug("Unhandled telnet command: " "{0:#x} {1:#x}".format(*iac_cmd)) # This must be a 3-byte TELNET command else: try: iac_cmd.append(buf[iac_loc + 2]) except IndexError: buf.extend(self._read_block(1)) iac_cmd.append(buf[iac_loc + 2]) # We do ECHO, SGA, and BINARY. Period. if iac_cmd[1] == DO and iac_cmd[2] not in [ECHO, SGA, BINARY]: self._write_cur(bytes([IAC, WONT, iac_cmd[2]])) log.debug("Telnet WON'T {:#x}".format(iac_cmd[2])) else: log.debug("Unhandled telnet command: " "{0:#x} {1:#x} {2:#x}".format(*iac_cmd)) # Remove the entire TELNET command from the buffer buf = buf.replace(iac_cmd, b'', 1) # Return the new copy of the buffer, minus telnet commands return buf def _accept(self): fd, addr = self.sock_fd.accept() self.fd_dict[fd.fileno()] = fd self.epoll.register(fd, select.EPOLLIN | select.EPOLLET) log.info("Telnet connection from {}:{}".format(addr[0], addr[1])) # This is a one-way negotiation. This is very basic so there # shouldn't be any problems with any decent client. fd.send(bytes([IAC, WILL, ECHO, IAC, WILL, SGA, IAC, WILL, BINARY, IAC, DO, BINARY])) if args.telnet_limit and len(self.fd_dict) > args.telnet_limit: fd.send(b'\r\nToo many connections\r\n') self._disconnect(fd.fileno()) log.warn("Client disconnected because of too many connections. " "(limit currently {})".format(args.telnet_limit)) def _disconnect(self, fileno): fd = self.fd_dict.pop(fileno) log.info("Telnet client disconnected") try: fd.shutdown(socket.SHUT_RDWR) except OSError as e: log.warn("shutdown: {}".format(e)) fd.close() def __enter__(self): # Open a socket and start listening sock_fd = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sock_fd.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) try: sock_fd.bind((self.addr, self.port)) except OSError: raise TelnetServerError("Cannot bind to {}:{}" .format(self.addr, self.port)) sock_fd.listen(socket.SOMAXCONN) self.sock_fd = sock_fd log.info("Telnet server ready for connections on {}:{}".format(self.addr, self.port)) log.info(self.stop_event.is_set()) return self def __exit__(self, exc_type, exc_val, exc_tb): for fileno in list(self.fd_dict.keys()): self._disconnect(fileno) self.sock_fd.close() return False class IOU(Router): def __init__(self, ttyC, ttyS, stop_event): self.ttyC = ttyC self.ttyS = ttyS self.stop_event = stop_event def read(self, bufsize): try: buf = self.fd.recv(bufsize) except BlockingIOError: return None return buf def write(self, buf): try: self.fd.send(buf) except BlockingIOError: return def _open(self): self.fd = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM) self.fd.setblocking(False) def _bind(self): try: os.unlink(self.ttyC) except FileNotFoundError: pass except Exception as e: raise NetioError("Couldn't unlink socket {}: {}".format(self.ttyC, e)) try: self.fd.bind(self.ttyC) except Exception as e: raise NetioError("Couldn't create socket {}: {}".format(self.ttyC, e)) def _connect(self): # Keep trying until we connect or die trying while not self.stop_event.is_set(): try: self.fd.connect(self.ttyS) except FileNotFoundError: log.debug("Waiting to connect to {}".format(self.ttyS)) time.sleep(RETRY_DELAY) except Exception as e: raise NetioError("Couldn't connect to socket {}: {}".format(self.ttyS, e)) else: break def register(self, epoll): self.epoll = epoll epoll.register(self.fd, select.EPOLLIN | select.EPOLLET) def fileno(self): return self.fd.fileno() def __enter__(self): self._open() self._bind() self._connect() return self def __exit__(self, exc_type, exc_val, exc_tb): os.unlink(self.ttyC) self.fd.close() return False class IOUConError(Exception): pass class LockError(IOUConError): pass class NetioError(IOUConError): pass class TTYError(IOUConError): pass class TelnetServerError(IOUConError): pass class ConfigError(IOUConError): pass def mkdir_netio(netio_dir): try: os.mkdir(netio_dir) except FileExistsError: pass except Exception as e: raise NetioError("Couldn't create directory {}: {}".format(netio_dir, e)) def send_recv_loop(console, router, esc_char, stop_event): epoll = select.epoll() router.register(epoll) console.register(epoll) router_fileno = router.fileno() esc_quit = bytes(ESC_QUIT.upper(), 'ascii') esc_state = False while not stop_event.is_set(): event_list = epoll.poll(timeout=POLL_TIMEOUT) # When/if the poll times out we send an empty datagram. If IOU # has gone away then this will toss a ConnectionRefusedError # exception. if not event_list: router.write(b'') continue for fileno, event in event_list: buf = bytearray() # IOU --> tty(s) if fileno == router_fileno: while not stop_event.is_set(): data = router.read(BUFFER_SIZE) if not data: break buf.extend(data) console.write(buf) # tty --> IOU else: while not stop_event.is_set(): data = console.read(fileno, BUFFER_SIZE) if not data: break buf.extend(data) # If we just received the escape character then # enter the escape state. # # If we are in the escape state then check for a # quit command. Or if it's the escape character then # send the escape character. Else, send the escape # character we ate earlier and whatever character we # just got. Exit escape state. # # If we're not in the escape state and this isn't an # escape character then just send it to IOU. if esc_state: if buf.upper() == esc_quit: sys.exit(EXIT_SUCCESS) elif buf == esc_char: router.write(esc_char) else: router.write(esc_char) router.write(buf) esc_state = False elif buf == esc_char: esc_state = True else: router.write(buf) def get_args(): parser = argparse.ArgumentParser( description='Connect to an IOU console port.') parser.add_argument('-d', '--debug', action='store_true', help='display some debugging information') parser.add_argument('-e', '--escape', help='set escape character (default: %(default)s)', default=ESC_CHAR, metavar='CHAR') parser.add_argument('-t', '--telnet-server', help='start telnet server listening on ADDR:PORT', metavar='ADDR:PORT', default=False) parser.add_argument('-l', '--telnet-limit', help='maximum number of simultaneous ' 'telnet connections (default: %(default)s)', metavar='LIMIT', type=int, default=1) parser.add_argument('appl_id', help='IOU instance identifier') return parser.parse_args() def get_escape_character(escape): # Figure out the escape character to use. # Can be any ASCII character or a spelled out control # character, like "^e". The string "none" disables it. if escape.lower() == 'none': esc_char = b'' elif len(escape) == 2 and escape[0] == '^': c = ord(escape[1].upper()) - 0x40 if not 0 <= c <= 0x1f: # control code range raise ConfigError("Invalid control code") esc_char = bytes([c]) elif len(escape) == 1: try: esc_char = bytes(escape, 'ascii') except ValueError as e: raise ConfigError("Invalid escape character") from e else: raise ConfigError("Invalid length for escape character") return esc_char def start_ioucon(cmdline_args, stop_event): global args args = cmdline_args if args.debug: logging.basicConfig(level=logging.DEBUG) else: # default logging level logging.basicConfig(level=logging.INFO) # Create paths for the Unix domain sockets netio = '/tmp/netio{}'.format(os.getuid()) ttyC = '{}/ttyC{}'.format(netio, args.appl_id) ttyS = '{}/ttyS{}'.format(netio, args.appl_id) try: mkdir_netio(netio) with FileLock(ttyC): esc_char = get_escape_character(args.escape) if args.telnet_server: addr, _, port = args.telnet_server.partition(':') nport = 0 try: nport = int(port) except ValueError: pass if addr == '' or nport == 0: raise ConfigError('format for --telnet-server must be ' 'ADDR:PORT (like 127.0.0.1:20000)') while not stop_event.is_set(): try: if args.telnet_server: with TelnetServer(addr, nport, stop_event) as console: with IOU(ttyC, ttyS, stop_event) as router: send_recv_loop(console, router, b'', stop_event) else: with IOU(ttyC, ttyS, stop_event) as router, TTY() as console: send_recv_loop(console, router, esc_char, stop_event) except ConnectionRefusedError: pass except KeyboardInterrupt: sys.exit(EXIT_ABORT) finally: # Put us at the beginning of a line if not args.telnet_server: print() except IOUConError as e: if args.debug: traceback.print_exc(file=sys.stderr) else: log.error("ioucon: {}".format(e)) sys.exit(EXIT_FAILURE) log.info("exiting...") def main(): import threading stop_event = threading.Event() args = get_args() start_ioucon(args, stop_event) if __name__ == '__main__': main()