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telnetlib.py
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r"""TELNET client class. Based on RFC 854: TELNET Protocol Specification, by J. Postel and J. Reynolds Example: >>> from telnetlib import Telnet >>> tn = Telnet('www.python.org', 79) # connect to finger port >>> tn.write(b'guido\r\n') >>> print(tn.read_all()) Login Name TTY Idle When Where guido Guido van Rossum pts/2 <Dec 2 11:10> snag.cnri.reston.. >>> Note that read_all() won't read until eof -- it just reads some data -- but it guarantees to read at least one byte unless EOF is hit. It is possible to pass a Telnet object to a selector in order to wait until more data is available. Note that in this case, read_eager() may return b'' even if there was data on the socket, because the protocol negotiation may have eaten the data. This is why EOFError is needed in some cases to distinguish between "no data" and "connection closed" (since the socket also appears ready for reading when it is closed). To do: - option negotiation - timeout should be intrinsic to the connection object instead of an option on one of the read calls only """ # Imported modules import sys import socket import selectors from time import monotonic as _time __all__ = ["Telnet"] # Tunable parameters DEBUGLEVEL = 0 # Telnet protocol defaults TELNET_PORT = 23 # Telnet protocol characters (don't change) IAC = bytes([255]) # "Interpret As Command" DONT = bytes([254]) DO = bytes([253]) WONT = bytes([252]) WILL = bytes([251]) theNULL = bytes([0]) SE = bytes([240]) # Subnegotiation End NOP = bytes([241]) # No Operation DM = bytes([242]) # Data Mark BRK = bytes([243]) # Break IP = bytes([244]) # Interrupt process AO = bytes([245]) # Abort output AYT = bytes([246]) # Are You There EC = bytes([247]) # Erase Character EL = bytes([248]) # Erase Line GA = bytes([249]) # Go Ahead SB = bytes([250]) # Subnegotiation Begin # Telnet protocol options code (don't change) # These ones all come from arpa/telnet.h BINARY = bytes([0]) # 8-bit data path ECHO = bytes([1]) # echo RCP = bytes([2]) # prepare to reconnect SGA = bytes([3]) # suppress go ahead NAMS = bytes([4]) # approximate message size STATUS = bytes([5]) # give status TM = bytes([6]) # timing mark RCTE = bytes([7]) # remote controlled transmission and echo NAOL = bytes([8]) # negotiate about output line width NAOP = bytes([9]) # negotiate about output page size NAOCRD = bytes([10]) # negotiate about CR disposition NAOHTS = bytes([11]) # negotiate about horizontal tabstops NAOHTD = bytes([12]) # negotiate about horizontal tab disposition NAOFFD = bytes([13]) # negotiate about formfeed disposition NAOVTS = bytes([14]) # negotiate about vertical tab stops NAOVTD = bytes([15]) # negotiate about vertical tab disposition NAOLFD = bytes([16]) # negotiate about output LF disposition XASCII = bytes([17]) # extended ascii character set LOGOUT = bytes([18]) # force logout BM = bytes([19]) # byte macro DET = bytes([20]) # data entry terminal SUPDUP = bytes([21]) # supdup protocol SUPDUPOUTPUT = bytes([22]) # supdup output SNDLOC = bytes([23]) # send location TTYPE = bytes([24]) # terminal type EOR = bytes([25]) # end or record TUID = bytes([26]) # TACACS user identification OUTMRK = bytes([27]) # output marking TTYLOC = bytes([28]) # terminal location number VT3270REGIME = bytes([29]) # 3270 regime X3PAD = bytes([30]) # X.3 PAD NAWS = bytes([31]) # window size TSPEED = bytes([32]) # terminal speed LFLOW = bytes([33]) # remote flow control LINEMODE = bytes([34]) # Linemode option XDISPLOC = bytes([35]) # X Display Location OLD_ENVIRON = bytes([36]) # Old - Environment variables AUTHENTICATION = bytes([37]) # Authenticate ENCRYPT = bytes([38]) # Encryption option NEW_ENVIRON = bytes([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 = bytes([40]) # TN3270E XAUTH = bytes([41]) # XAUTH CHARSET = bytes([42]) # CHARSET RSP = bytes([43]) # Telnet Remote Serial Port COM_PORT_OPTION = bytes([44]) # Com Port Control Option SUPPRESS_LOCAL_ECHO = bytes([45]) # Telnet Suppress Local Echo TLS = bytes([46]) # Telnet Start TLS KERMIT = bytes([47]) # KERMIT SEND_URL = bytes([48]) # SEND-URL FORWARD_X = bytes([49]) # FORWARD_X PRAGMA_LOGON = bytes([138]) # TELOPT PRAGMA LOGON SSPI_LOGON = bytes([139]) # TELOPT SSPI LOGON PRAGMA_HEARTBEAT = bytes([140]) # TELOPT PRAGMA HEARTBEAT EXOPL = bytes([255]) # Extended-Options-List NOOPT = bytes([0]) # poll/select have the advantage of not requiring any extra file descriptor, # contrarily to epoll/kqueue (also, they require a single syscall). if hasattr(selectors, 'PollSelector'): _TelnetSelector = selectors.PollSelector else: _TelnetSelector = selectors.SelectSelector class Telnet: """Telnet interface class. An instance of this class represents a connection to a telnet server. The instance is initially not connected; the open() method must be used to establish a connection. Alternatively, the host name and optional port number can be passed to the constructor, too. Don't try to reopen an already connected instance. This class has many read_*() methods. Note that some of them raise EOFError when the end of the connection is read, because they can return an empty string for other reasons. See the individual doc strings. read_until(expected, [timeout]) Read until the expected string has been seen, or a timeout is hit (default is no timeout); may block. read_all() Read all data until EOF; may block. read_some() Read at least one byte or EOF; may block. read_very_eager() Read all data available already queued or on the socket, without blocking. read_eager() Read either data already queued or some data available on the socket, without blocking. read_lazy() Read all data in the raw queue (processing it first), without doing any socket I/O. read_very_lazy() Reads all data in the cooked queue, without doing any socket I/O. read_sb_data() Reads available data between SB ... SE sequence. Don't block. set_option_negotiation_callback(callback) Each time a telnet option is read on the input flow, this callback (if set) is called with the following parameters : callback(telnet socket, command, option) option will be chr(0) when there is no option. No other action is done afterwards by telnetlib. """ def __init__(self, host=None, port=0, timeout=socket._GLOBAL_DEFAULT_TIMEOUT): """Constructor. When called without arguments, create an unconnected instance. With a hostname argument, it connects the instance; port number and timeout are optional. """ self.debuglevel = DEBUGLEVEL self.host = host self.port = port self.timeout = timeout self.sock = None self.rawq = b'' self.irawq = 0 self.cookedq = b'' self.eof = 0 self.iacseq = b'' # Buffer for IAC sequence. self.sb = 0 # flag for SB and SE sequence. self.sbdataq = b'' self.option_callback = None if host is not None: self.open(host, port, timeout) def open(self, host, port=0, timeout=socket._GLOBAL_DEFAULT_TIMEOUT): """Connect to a host. The optional second argument is the port number, which defaults to the standard telnet port (23). Don't try to reopen an already connected instance. """ self.eof = 0 if not port: port = TELNET_PORT self.host = host self.port = port self.timeout = timeout self.sock = socket.create_connection((host, port), timeout) def __del__(self): """Destructor -- close the connection.""" self.close() def msg(self, msg, *args): """Print a debug message, when the debug level is > 0. If extra arguments are present, they are substituted in the message using the standard string formatting operator. """ if self.debuglevel > 0: print('Telnet(%s,%s):' % (self.host, self.port), end=' ') if args: print(msg % args) else: print(msg) def set_debuglevel(self, debuglevel): """Set the debug level. The higher it is, the more debug output you get (on sys.stdout). """ self.debuglevel = debuglevel def close(self): """Close the connection.""" sock = self.sock self.sock = None self.eof = True self.iacseq = b'' self.sb = 0 if sock: sock.close() def get_socket(self): """Return the socket object used internally.""" return self.sock def fileno(self): """Return the fileno() of the socket object used internally.""" return self.sock.fileno() def write(self, buffer): """Write a string to the socket, doubling any IAC characters. Can block if the connection is blocked. May raise OSError if the connection is closed. """ if IAC in buffer: buffer = buffer.replace(IAC, IAC+IAC) self.msg("send %r", buffer) self.sock.sendall(buffer) def read_until(self, match, timeout=None): """Read until a given string is encountered or until timeout. When no match is found, return whatever is available instead, possibly the empty string. Raise EOFError if the connection is closed and no cooked data is available. """ n = len(match) self.process_rawq() i = self.cookedq.find(match) if i >= 0: i = i+n buf = self.cookedq[:i] self.cookedq = self.cookedq[i:] return buf if timeout is not None: deadline = _time() + timeout with _TelnetSelector() as selector: selector.register(self, selectors.EVENT_READ) while not self.eof: if selector.select(timeout): i = max(0, len(self.cookedq)-n) self.fill_rawq() self.process_rawq() i = self.cookedq.find(match, i) if i >= 0: i = i+n buf = self.cookedq[:i] self.cookedq = self.cookedq[i:] return buf if timeout is not None: timeout = deadline - _time() if timeout < 0: break return self.read_very_lazy() def read_all(self): """Read all data until EOF; block until connection closed.""" self.process_rawq() while not self.eof: self.fill_rawq() self.process_rawq() buf = self.cookedq self.cookedq = b'' return buf def read_some(self): """Read at least one byte of cooked data unless EOF is hit. Return b'' if EOF is hit. Block if no data is immediately available. """ self.process_rawq() while not self.cookedq and not self.eof: self.fill_rawq() self.process_rawq() buf = self.cookedq self.cookedq = b'' return buf def read_very_eager(self): """Read everything that's possible without blocking in I/O (eager). Raise EOFError if connection closed and no cooked data available. Return b'' if no cooked data available otherwise. Don't block unless in the midst of an IAC sequence. """ self.process_rawq() while not self.eof and self.sock_avail(): self.fill_rawq() self.process_rawq() return self.read_very_lazy() def read_eager(self): """Read readily available data. Raise EOFError if connection closed and no cooked data available. Return b'' if no cooked data available otherwise. Don't block unless in the midst of an IAC sequence. """ self.process_rawq() while not self.cookedq and not self.eof and self.sock_avail(): self.fill_rawq() self.process_rawq() return self.read_very_lazy() def read_lazy(self): """Process and return data that's already in the queues (lazy). Raise EOFError if connection closed and no data available. Return b'' if no cooked data available otherwise. Don't block unless in the midst of an IAC sequence. """ self.process_rawq() return self.read_very_lazy() def read_very_lazy(self): """Return any data available in the cooked queue (very lazy). Raise EOFError if connection closed and no data available. Return b'' if no cooked data available otherwise. Don't block. """ buf = self.cookedq self.cookedq = b'' if not buf and self.eof and not self.rawq: raise EOFError('telnet connection closed') return buf def read_sb_data(self): """Return any data available in the SB ... SE queue. Return b'' 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 = b'' return buf def set_option_negotiation_callback(self, callback): """Provide a callback function called after each receipt of a telnet option.""" self.option_callback = callback def process_rawq(self): """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. """ buf = [b'', b''] try: while self.rawq: c = self.rawq_getchar() if not self.iacseq: if c == theNULL: continue if c == b"\021": continue if c != IAC: buf[self.sb] = buf[self.sb] + c continue else: self.iacseq += 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 = b'' if c == IAC: buf[self.sb] = buf[self.sb] + c else: if c == SB: # SB ... SE start. self.sb = 1 self.sbdataq = b'' elif c == SE: self.sb = 0 self.sbdataq = self.sbdataq + buf[1] buf[1] = b'' if self.option_callback: # Callback is supposed to look into # the sbdataq self.option_callback(self.sock, c, NOOPT) else: # We can't offer automatic processing of # suboptions. Alas, we should not get any # unless we did a WILL/DO before. self.msg('IAC %d not recognized' % ord(c)) elif len(self.iacseq) == 2: cmd = self.iacseq[1:2] self.iacseq = b'' opt = c if cmd in (DO, DONT): self.msg('IAC %s %d', cmd == DO and 'DO' or 'DONT', ord(opt)) if self.option_callback: self.option_callback(self.sock, cmd, opt) else: self.sock.sendall(IAC + WONT + opt) elif cmd in (WILL, WONT): self.msg('IAC %s %d', cmd == WILL and 'WILL' or 'WONT', ord(opt)) if self.option_callback: self.option_callback(self.sock, cmd, opt) else: self.sock.sendall(IAC + DONT + opt) except EOFError: # raised by self.rawq_getchar() self.iacseq = b'' # Reset on EOF self.sb = 0 pass self.cookedq = self.cookedq + buf[0] self.sbdataq = self.sbdataq + buf[1] def rawq_getchar(self): """Get next char from raw queue. Block if no data is immediately available. Raise EOFError when connection is closed. """ if not self.rawq: self.fill_rawq() if self.eof: raise EOFError c = self.rawq[self.irawq:self.irawq+1] self.irawq = self.irawq + 1 if self.irawq >= len(self.rawq): self.rawq = b'' self.irawq = 0 return c def fill_rawq(self): """Fill raw queue from exactly one recv() system call. Block if no data is immediately available. Set self.eof when connection is closed. """ if self.irawq >= len(self.rawq): self.rawq = b'' self.irawq = 0 # The buffer size should be fairly small so as to avoid quadratic # behavior in process_rawq() above buf = self.sock.recv(50) self.msg("recv %r", buf) self.eof = (not buf) self.rawq = self.rawq + buf def sock_avail(self): """Test whether data is available on the socket.""" with _TelnetSelector() as selector: selector.register(self, selectors.EVENT_READ) return bool(selector.select(0)) def interact(self): """Interaction function, emulates a very dumb telnet client.""" if sys.platform == "win32": self.mt_interact() return with _TelnetSelector() as selector: selector.register(self, selectors.EVENT_READ) selector.register(sys.stdin, selectors.EVENT_READ) while True: for key, events in selector.select(): if key.fileobj is self: try: text = self.read_eager() except EOFError: print('*** Connection closed by remote host ***') return if text: sys.stdout.write(text.decode('ascii')) sys.stdout.flush() elif key.fileobj is sys.stdin: line = sys.stdin.readline().encode('ascii') if not line: return self.write(line) def mt_interact(self): """Multithreaded version of interact().""" import _thread _thread.start_new_thread(self.listener, ()) while 1: line = sys.stdin.readline() if not line: break self.write(line.encode('ascii')) def listener(self): """Helper for mt_interact() -- this executes in the other thread.""" while 1: try: data = self.read_eager() except EOFError: print('*** Connection closed by remote host ***') return if data: sys.stdout.write(data.decode('ascii')) else: sys.stdout.flush() def expect(self, list, timeout=None): """Read until one from a list of a regular expressions matches. The first argument is a list of regular expressions, either compiled (re.RegexObject instances) or uncompiled (strings). The optional second argument is a timeout, in seconds; default is no timeout. Return a tuple of three items: the index in the list of the first regular expression that matches; the match object returned; and the text read up till and including the match. If EOF is read and no text was read, raise EOFError. Otherwise, when nothing matches, return (-1, None, text) where text is the text received so far (may be the empty string if a timeout happened). If a regular expression ends with a greedy match (e.g. '.*') or if more than one expression can match the same input, the results are undeterministic, and may depend on the I/O timing. """ re = None list = list[:] indices = range(len(list)) for i in indices: if not hasattr(list[i], "search"): if not re: import re list[i] = re.compile(list[i]) if timeout is not None: deadline = _time() + timeout with _TelnetSelector() as selector: selector.register(self, selectors.EVENT_READ) while not self.eof: self.process_rawq() for i in indices: m = list[i].search(self.cookedq) if m: e = m.end() text = self.cookedq[:e] self.cookedq = self.cookedq[e:] return (i, m, text) if timeout is not None: ready = selector.select(timeout) timeout = deadline - _time() if not ready: if timeout < 0: break else: continue self.fill_rawq() text = self.read_very_lazy() if not text and self.eof: raise EOFError return (-1, None, text) def __enter__(self): return self def __exit__(self, type, value, traceback): self.close() def test(): """Test program for telnetlib. Usage: python telnetlib.py [-d] ... [host [port]] Default host is localhost; default port is 23. """ debuglevel = 0 while sys.argv[1:] and sys.argv[1] == '-d': debuglevel = debuglevel+1 del sys.argv[1] host = 'localhost' if sys.argv[1:]: host = sys.argv[1] port = 0 if sys.argv[2:]: portstr = sys.argv[2] try: port = int(portstr) except ValueError: port = socket.getservbyname(portstr, 'tcp') with Telnet() as tn: tn.set_debuglevel(debuglevel) tn.open(host, port, timeout=0.5) tn.interact() if __name__ == '__main__': test()