569 lines
24 KiB
Python
569 lines
24 KiB
Python
"""This module implements all state handling during uploads and downloads, the
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main interface to which being the TftpState base class.
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The concept is simple. Each context object represents a single upload or
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download, and the state object in the context object represents the current
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state of that transfer. The state object has a handle() method that expects
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the next packet in the transfer, and returns a state object until the transfer
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is complete, at which point it returns None. That is, unless there is a fatal
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error, in which case a TftpException is returned instead."""
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from TftpShared import *
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from TftpPacketTypes import *
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import os
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###############################################################################
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# State classes
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###############################################################################
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class TftpState(object):
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"""The base class for the states."""
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def __init__(self, context):
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"""Constructor for setting up common instance variables. The involved
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file object is required, since in tftp there's always a file
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involved."""
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self.context = context
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def handle(self, pkt, raddress, rport):
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"""An abstract method for handling a packet. It is expected to return
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a TftpState object, either itself or a new state."""
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raise NotImplementedError, "Abstract method"
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def handleOACK(self, pkt):
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"""This method handles an OACK from the server, syncing any accepted
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options."""
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if pkt.options.keys() > 0:
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if pkt.match_options(self.context.options):
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log.info("Successful negotiation of options")
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# Set options to OACK options
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self.context.options = pkt.options
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for key in self.context.options:
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log.info(" %s = %s" % (key, self.context.options[key]))
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else:
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log.error("Failed to negotiate options")
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raise TftpException, "Failed to negotiate options"
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else:
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raise TftpException, "No options found in OACK"
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def returnSupportedOptions(self, options):
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"""This method takes a requested options list from a client, and
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returns the ones that are supported."""
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# We support the options blksize and tsize right now.
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# FIXME - put this somewhere else?
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accepted_options = {}
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for option in options:
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if option == 'blksize':
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# Make sure it's valid.
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if int(options[option]) > MAX_BLKSIZE:
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log.info("Client requested blksize greater than %d "
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"setting to maximum" % MAX_BLKSIZE)
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accepted_options[option] = MAX_BLKSIZE
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elif int(options[option]) < MIN_BLKSIZE:
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log.info("Client requested blksize less than %d "
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"setting to minimum" % MIN_BLKSIZE)
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accepted_options[option] = MIN_BLKSIZE
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else:
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accepted_options[option] = options[option]
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elif option == 'tsize':
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log.debug("tsize option is set")
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accepted_options['tsize'] = 1
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else:
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log.info("Dropping unsupported option '%s'" % option)
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log.debug("Returning these accepted options: %s" % accepted_options)
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return accepted_options
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def sendDAT(self):
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"""This method sends the next DAT packet based on the data in the
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context. It returns a boolean indicating whether the transfer is
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finished."""
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finished = False
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blocknumber = self.context.next_block
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# Test hook
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if DELAY_BLOCK and DELAY_BLOCK == blocknumber:
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import time
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log.debug("Deliberately delaying 10 seconds...")
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time.sleep(10)
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tftpassert( blocknumber > 0, "There is no block zero!" )
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dat = None
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blksize = self.context.getBlocksize()
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buffer = self.context.fileobj.read(blksize)
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log.debug("Read %d bytes into buffer" % len(buffer))
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if len(buffer) < blksize:
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log.info("Reached EOF on file %s"
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% self.context.file_to_transfer)
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finished = True
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dat = TftpPacketDAT()
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dat.data = buffer
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dat.blocknumber = blocknumber
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self.context.metrics.bytes += len(dat.data)
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log.debug("Sending DAT packet %d" % dat.blocknumber)
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self.context.sock.sendto(dat.encode().buffer,
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(self.context.host, self.context.tidport))
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if self.context.packethook:
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self.context.packethook(dat)
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self.context.last_pkt = dat
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return finished
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def sendACK(self, blocknumber=None):
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"""This method sends an ack packet to the block number specified. If
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none is specified, it defaults to the next_block property in the
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parent context."""
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log.debug("In sendACK, passed blocknumber is %s" % blocknumber)
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if blocknumber is None:
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blocknumber = self.context.next_block
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log.info("Sending ack to block %d" % blocknumber)
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ackpkt = TftpPacketACK()
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ackpkt.blocknumber = blocknumber
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self.context.sock.sendto(ackpkt.encode().buffer,
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(self.context.host,
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self.context.tidport))
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self.context.last_pkt = ackpkt
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def sendError(self, errorcode):
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"""This method uses the socket passed, and uses the errorcode to
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compose and send an error packet."""
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log.debug("In sendError, being asked to send error %d" % errorcode)
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errpkt = TftpPacketERR()
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errpkt.errorcode = errorcode
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self.context.sock.sendto(errpkt.encode().buffer,
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(self.context.host,
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self.context.tidport))
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self.context.last_pkt = errpkt
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def sendOACK(self):
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"""This method sends an OACK packet with the options from the current
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context."""
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log.debug("In sendOACK with options %s" % self.context.options)
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pkt = TftpPacketOACK()
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pkt.options = self.context.options
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self.context.sock.sendto(pkt.encode().buffer,
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(self.context.host,
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self.context.tidport))
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self.context.last_pkt = pkt
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def resendLast(self):
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"Resend the last sent packet due to a timeout."
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log.warn("Resending packet %s on sessions %s"
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% (self.context.last_pkt, self))
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self.context.metrics.resent_bytes += len(self.context.last_pkt.buffer)
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self.context.metrics.add_dup(self.context.last_pkt)
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sendto_port = self.context.tidport
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if not sendto_port:
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# If the tidport wasn't set, then the remote end hasn't even
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# started talking to us yet. That's not good. Maybe it's not
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# there.
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sendto_port = self.context.port
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self.context.sock.sendto(self.context.last_pkt.encode().buffer,
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(self.context.host, sendto_port))
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if self.context.packethook:
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self.context.packethook(self.context.last_pkt)
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def handleDat(self, pkt):
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"""This method handles a DAT packet during a client download, or a
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server upload."""
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log.info("Handling DAT packet - block %d" % pkt.blocknumber)
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log.debug("Expecting block %s" % self.context.next_block)
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if pkt.blocknumber == self.context.next_block:
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log.debug("Good, received block %d in sequence"
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% pkt.blocknumber)
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self.sendACK()
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self.context.next_block += 1
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log.debug("Writing %d bytes to output file"
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% len(pkt.data))
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self.context.fileobj.write(pkt.data)
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self.context.metrics.bytes += len(pkt.data)
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# Check for end-of-file, any less than full data packet.
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if len(pkt.data) < self.context.getBlocksize():
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log.info("End of file detected")
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return None
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elif pkt.blocknumber < self.context.next_block:
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if pkt.blocknumber == 0:
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log.warn("There is no block zero!")
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self.sendError(TftpErrors.IllegalTftpOp)
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raise TftpException, "There is no block zero!"
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log.warn("Dropping duplicate block %d" % pkt.blocknumber)
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self.context.metrics.add_dup(pkt)
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log.debug("ACKing block %d again, just in case" % pkt.blocknumber)
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self.sendACK(pkt.blocknumber)
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else:
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# FIXME: should we be more tolerant and just discard instead?
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msg = "Whoa! Received future block %d but expected %d" \
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% (pkt.blocknumber, self.context.next_block)
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log.error(msg)
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raise TftpException, msg
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# Default is to ack
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return TftpStateExpectDAT(self.context)
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class TftpServerState(TftpState):
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"""The base class for server states."""
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def __init__(self, context):
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TftpState.__init__(self, context)
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# This variable is used to store the absolute path to the file being
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# managed.
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self.full_path = None
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def serverInitial(self, pkt, raddress, rport):
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"""This method performs initial setup for a server context transfer,
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put here to refactor code out of the TftpStateServerRecvRRQ and
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TftpStateServerRecvWRQ classes, since their initial setup is
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identical. The method returns a boolean, sendoack, to indicate whether
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it is required to send an OACK to the client."""
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options = pkt.options
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sendoack = False
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if not self.context.tidport:
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self.context.tidport = rport
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log.info("Setting tidport to %s" % rport)
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log.debug("Setting default options, blksize")
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self.context.options = { 'blksize': DEF_BLKSIZE }
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if options:
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log.debug("Options requested: %s" % options)
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supported_options = self.returnSupportedOptions(options)
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self.context.options.update(supported_options)
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sendoack = True
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# FIXME - only octet mode is supported at this time.
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if pkt.mode != 'octet':
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self.sendError(TftpErrors.IllegalTftpOp)
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raise TftpException, \
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"Only octet transfers are supported at this time."
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# test host/port of client end
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if self.context.host != raddress or self.context.port != rport:
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self.sendError(TftpErrors.UnknownTID)
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log.error("Expected traffic from %s:%s but received it "
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"from %s:%s instead."
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% (self.context.host,
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self.context.port,
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raddress,
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rport))
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# FIXME: increment an error count?
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# Return same state, we're still waiting for valid traffic.
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return self
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log.debug("Requested filename is %s" % pkt.filename)
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# Make sure that the path to the file is contained in the server's
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# root directory.
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full_path = os.path.join(self.context.root, pkt.filename)
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self.full_path = os.path.abspath(full_path)
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log.debug("full_path is %s" % full_path)
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if self.full_path.startswith(self.context.root):
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log.info("requested file is in the server root - good")
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else:
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log.warn("requested file is not within the server root - bad")
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self.sendError(TftpErrors.IllegalTftpOp)
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raise TftpException, "bad file path"
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self.context.file_to_transfer = pkt.filename
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return sendoack
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class TftpStateServerRecvRRQ(TftpServerState):
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"""This class represents the state of the TFTP server when it has just
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received an RRQ packet."""
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def handle(self, pkt, raddress, rport):
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"Handle an initial RRQ packet as a server."
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log.debug("In TftpStateServerRecvRRQ.handle")
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sendoack = self.serverInitial(pkt, raddress, rport)
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path = self.full_path
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log.info("Opening file %s for reading" % path)
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if os.path.exists(path):
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# Note: Open in binary mode for win32 portability, since win32
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# blows.
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self.context.fileobj = open(path, "rb")
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elif self.context.dyn_file_func:
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log.debug("No such file %s but using dyn_file_func" % path)
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self.context.fileobj = \
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self.context.dyn_file_func(self.context.file_to_transfer, (raddress, rport))
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if self.context.fileobj is None:
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log.debug("dyn_file_func returned 'None', treating as "
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"FileNotFound")
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self.sendError(TftpErrors.FileNotFound)
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raise TftpException, "File not found: %s" % path
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else:
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self.sendError(TftpErrors.FileNotFound)
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raise TftpException, "File not found: %s" % path
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# Options negotiation.
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if sendoack:
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# Note, next_block is 0 here since that's the proper
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# acknowledgement to an OACK.
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# FIXME: perhaps we do need a TftpStateExpectOACK class...
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self.sendOACK()
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# Note, self.context.next_block is already 0.
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else:
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self.context.next_block = 1
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log.debug("No requested options, starting send...")
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self.context.pending_complete = self.sendDAT()
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# Note, we expect an ack regardless of whether we sent a DAT or an
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# OACK.
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return TftpStateExpectACK(self.context)
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# Note, we don't have to check any other states in this method, that's
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# up to the caller.
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class TftpStateServerRecvWRQ(TftpServerState):
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"""This class represents the state of the TFTP server when it has just
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received a WRQ packet."""
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def make_subdirs(self):
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"""The purpose of this method is to, if necessary, create all of the
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subdirectories leading up to the file to the written."""
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# Pull off everything below the root.
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subpath = self.full_path[len(self.context.root):]
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log.debug("make_subdirs: subpath is %s" % subpath)
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# Split on directory separators, but drop the last one, as it should
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# be the filename.
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dirs = subpath.split(os.sep)[:-1]
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log.debug("dirs is %s" % dirs)
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current = self.context.root
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for dir in dirs:
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if dir:
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current = os.path.join(current, dir)
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if os.path.isdir(current):
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log.debug("%s is already an existing directory" % current)
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else:
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os.mkdir(current, 0700)
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def handle(self, pkt, raddress, rport):
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"Handle an initial WRQ packet as a server."
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log.debug("In TftpStateServerRecvWRQ.handle")
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sendoack = self.serverInitial(pkt, raddress, rport)
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path = self.full_path
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log.info("Opening file %s for writing" % path)
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if os.path.exists(path):
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# FIXME: correct behavior?
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log.warn("File %s exists already, overwriting..." % self.context.file_to_transfer)
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# FIXME: I think we should upload to a temp file and not overwrite the
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# existing file until the file is successfully uploaded.
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self.make_subdirs()
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self.context.fileobj = open(path, "wb")
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# Options negotiation.
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if sendoack:
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log.debug("Sending OACK to client")
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self.sendOACK()
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else:
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log.debug("No requested options, expecting transfer to begin...")
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self.sendACK()
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# Whether we're sending an oack or not, we're expecting a DAT for
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# block 1
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self.context.next_block = 1
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# We may have sent an OACK, but we're expecting a DAT as the response
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# to either the OACK or an ACK, so lets unconditionally use the
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# TftpStateExpectDAT state.
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return TftpStateExpectDAT(self.context)
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# Note, we don't have to check any other states in this method, that's
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# up to the caller.
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class TftpStateServerStart(TftpState):
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"""The start state for the server. This is a transitory state since at
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this point we don't know if we're handling an upload or a download. We
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will commit to one of them once we interpret the initial packet."""
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def handle(self, pkt, raddress, rport):
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"""Handle a packet we just received."""
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log.debug("In TftpStateServerStart.handle")
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if isinstance(pkt, TftpPacketRRQ):
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log.debug("Handling an RRQ packet")
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return TftpStateServerRecvRRQ(self.context).handle(pkt,
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raddress,
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rport)
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elif isinstance(pkt, TftpPacketWRQ):
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log.debug("Handling a WRQ packet")
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return TftpStateServerRecvWRQ(self.context).handle(pkt,
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raddress,
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rport)
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else:
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self.sendError(TftpErrors.IllegalTftpOp)
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raise TftpException, \
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"Invalid packet to begin up/download: %s" % pkt
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class TftpStateExpectACK(TftpState):
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"""This class represents the state of the transfer when a DAT was just
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sent, and we are waiting for an ACK from the server. This class is the
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same one used by the client during the upload, and the server during the
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download."""
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def handle(self, pkt, raddress, rport):
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"Handle a packet, hopefully an ACK since we just sent a DAT."
|
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if isinstance(pkt, TftpPacketACK):
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log.info("Received ACK for packet %d" % pkt.blocknumber)
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# Is this an ack to the one we just sent?
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if self.context.next_block == pkt.blocknumber:
|
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if self.context.pending_complete:
|
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log.info("Received ACK to final DAT, we're done.")
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return None
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else:
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log.debug("Good ACK, sending next DAT")
|
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self.context.next_block += 1
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log.debug("Incremented next_block to %d"
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% (self.context.next_block))
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self.context.pending_complete = self.sendDAT()
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elif pkt.blocknumber < self.context.next_block:
|
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log.debug("Received duplicate ACK for block %d"
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% pkt.blocknumber)
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self.context.metrics.add_dup(pkt)
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else:
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log.warn("Oooh, time warp. Received ACK to packet we "
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"didn't send yet. Discarding.")
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self.context.metrics.errors += 1
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return self
|
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elif isinstance(pkt, TftpPacketERR):
|
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log.error("Received ERR packet from peer: %s" % str(pkt))
|
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raise TftpException, \
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"Received ERR packet from peer: %s" % str(pkt)
|
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else:
|
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log.warn("Discarding unsupported packet: %s" % str(pkt))
|
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return self
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|
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class TftpStateExpectDAT(TftpState):
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"""Just sent an ACK packet. Waiting for DAT."""
|
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def handle(self, pkt, raddress, rport):
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"""Handle the packet in response to an ACK, which should be a DAT."""
|
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if isinstance(pkt, TftpPacketDAT):
|
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return self.handleDat(pkt)
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|
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# Every other packet type is a problem.
|
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elif isinstance(pkt, TftpPacketACK):
|
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# Umm, we ACK, you don't.
|
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self.sendError(TftpErrors.IllegalTftpOp)
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raise TftpException, "Received ACK from peer when expecting DAT"
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|
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elif isinstance(pkt, TftpPacketWRQ):
|
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self.sendError(TftpErrors.IllegalTftpOp)
|
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raise TftpException, "Received WRQ from peer when expecting DAT"
|
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|
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elif isinstance(pkt, TftpPacketERR):
|
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self.sendError(TftpErrors.IllegalTftpOp)
|
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raise TftpException, "Received ERR from peer: " + str(pkt)
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|
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else:
|
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self.sendError(TftpErrors.IllegalTftpOp)
|
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raise TftpException, "Received unknown packet type from peer: " + str(pkt)
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|
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class TftpStateSentWRQ(TftpState):
|
|
"""Just sent an WRQ packet for an upload."""
|
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def handle(self, pkt, raddress, rport):
|
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"""Handle a packet we just received."""
|
|
if not self.context.tidport:
|
|
self.context.tidport = rport
|
|
log.debug("Set remote port for session to %s" % rport)
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|
|
# If we're going to successfully transfer the file, then we should see
|
|
# either an OACK for accepted options, or an ACK to ignore options.
|
|
if isinstance(pkt, TftpPacketOACK):
|
|
log.info("Received OACK from server")
|
|
try:
|
|
self.handleOACK(pkt)
|
|
except TftpException:
|
|
log.error("Failed to negotiate options")
|
|
self.sendError(TftpErrors.FailedNegotiation)
|
|
raise
|
|
else:
|
|
log.debug("Sending first DAT packet")
|
|
self.context.pending_complete = self.sendDAT()
|
|
log.debug("Changing state to TftpStateExpectACK")
|
|
return TftpStateExpectACK(self.context)
|
|
|
|
elif isinstance(pkt, TftpPacketACK):
|
|
log.info("Received ACK from server")
|
|
log.debug("Apparently the server ignored our options")
|
|
# The block number should be zero.
|
|
if pkt.blocknumber == 0:
|
|
log.debug("Ack blocknumber is zero as expected")
|
|
log.debug("Sending first DAT packet")
|
|
self.context.pending_complete = self.sendDAT()
|
|
log.debug("Changing state to TftpStateExpectACK")
|
|
return TftpStateExpectACK(self.context)
|
|
else:
|
|
log.warn("Discarding ACK to block %s" % pkt.blocknumber)
|
|
log.debug("Still waiting for valid response from server")
|
|
return self
|
|
|
|
elif isinstance(pkt, TftpPacketERR):
|
|
self.sendError(TftpErrors.IllegalTftpOp)
|
|
raise TftpException, "Received ERR from server: " + str(pkt)
|
|
|
|
elif isinstance(pkt, TftpPacketRRQ):
|
|
self.sendError(TftpErrors.IllegalTftpOp)
|
|
raise TftpException, "Received RRQ from server while in upload"
|
|
|
|
elif isinstance(pkt, TftpPacketDAT):
|
|
self.sendError(TftpErrors.IllegalTftpOp)
|
|
raise TftpException, "Received DAT from server while in upload"
|
|
|
|
else:
|
|
self.sendError(TftpErrors.IllegalTftpOp)
|
|
raise TftpException, "Received unknown packet type from server: " + str(pkt)
|
|
|
|
# By default, no state change.
|
|
return self
|
|
|
|
class TftpStateSentRRQ(TftpState):
|
|
"""Just sent an RRQ packet."""
|
|
def handle(self, pkt, raddress, rport):
|
|
"""Handle the packet in response to an RRQ to the server."""
|
|
if not self.context.tidport:
|
|
self.context.tidport = rport
|
|
log.info("Set remote port for session to %s" % rport)
|
|
|
|
# Now check the packet type and dispatch it properly.
|
|
if isinstance(pkt, TftpPacketOACK):
|
|
log.info("Received OACK from server")
|
|
try:
|
|
self.handleOACK(pkt)
|
|
except TftpException, err:
|
|
log.error("Failed to negotiate options: %s" % str(err))
|
|
self.sendError(TftpErrors.FailedNegotiation)
|
|
raise
|
|
else:
|
|
log.debug("Sending ACK to OACK")
|
|
|
|
self.sendACK(blocknumber=0)
|
|
|
|
log.debug("Changing state to TftpStateExpectDAT")
|
|
return TftpStateExpectDAT(self.context)
|
|
|
|
elif isinstance(pkt, TftpPacketDAT):
|
|
# If there are any options set, then the server didn't honour any
|
|
# of them.
|
|
log.info("Received DAT from server")
|
|
if self.context.options:
|
|
log.info("Server ignored options, falling back to defaults")
|
|
self.context.options = { 'blksize': DEF_BLKSIZE }
|
|
return self.handleDat(pkt)
|
|
|
|
# Every other packet type is a problem.
|
|
elif isinstance(pkt, TftpPacketACK):
|
|
# Umm, we ACK, the server doesn't.
|
|
self.sendError(TftpErrors.IllegalTftpOp)
|
|
raise TftpException, "Received ACK from server while in download"
|
|
|
|
elif isinstance(pkt, TftpPacketWRQ):
|
|
self.sendError(TftpErrors.IllegalTftpOp)
|
|
raise TftpException, "Received WRQ from server while in download"
|
|
|
|
elif isinstance(pkt, TftpPacketERR):
|
|
self.sendError(TftpErrors.IllegalTftpOp)
|
|
raise TftpException, "Received ERR from server: " + str(pkt)
|
|
|
|
else:
|
|
self.sendError(TftpErrors.IllegalTftpOp)
|
|
raise TftpException, "Received unknown packet type from server: " + str(pkt)
|
|
|
|
# By default, no state change.
|
|
return self
|