~azzar1/unity/add-show-desktop-key

# IVLE

# Copyright (C) 2007-2008 The University of Melbourne

#

# 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 2 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, write to the Free Software

# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

# App: consoleservice

# Author: Matt Giuca, Tom Conway

# Date: 14/1/2008

import cStringIO

import httplib

import md5

import os

import pwd

import random

import socket

import sys

import urllib

import uuid

import cjson

from common import (util, studpath)

import conf

trampoline_path = os.path.join(conf.ivle_install_dir, "bin/trampoline")

python_path = "/usr/bin/python"                     # Within jail

console_dir = "/opt/ivle/scripts"                   # Within jail

console_path = "/opt/ivle/scripts/python-console"   # Within jail

def handle(req):

    """Handler for the Console Service AJAX backend application."""

    if len(req.path) > 0 and req.path[-1] == os.sep:

        path = req.path[:-1]

    else:

        path = req.path

    # The path determines which "command" we are receiving

    if req.path == "start":

        handle_start(req)

    elif req.path == "chat":

        handle_chat(req)

    elif req.path == "block":

        handle_chat(req, kind="block")

    else:

        req.throw_error(req.HTTP_BAD_REQUEST)

def handle_start(req):

    jail_path = os.path.join(conf.jail_base, req.username)

    working_dir = os.path.join("/home", req.username)   # Within jail

    # Get the UID of the logged-in user

    try:

        (_,_,uid,_,_,_,_) = pwd.getpwnam(req.username)

    except KeyError:

        # The user does not exist. This should have already failed the

        # previous test.

        req.throw_error(req.HTTP_INTERNAL_SERVER_ERROR)

    # Set request attributes

    req.content_type = "text/plain"

    req.write_html_head_foot = False

    # TODO: Figure out the host name the console server is running on.

    host = socket.gethostname()

    # Create magic

    # TODO

    magic = md5.new(uuid.uuid4().bytes).digest().encode('hex')

    # Try to find a free port on the server.

    # Just try some random ports in the range [3000,8000)

    # until we either succeed, or give up. If you think this

    # sounds risky, it isn't:

    # For N ports (e.g. 5000) with k (e.g. 100) in use, the

    # probability of failing to find a free port in t (e.g. 5) tries

    # is (k / N) ** t (e.g. 3.2*10e-9).

    tries = 0

    while tries < 5:

        port = int(random.uniform(3000, 8000))

        # Start the console server (port, magic)

        # trampoline usage: tramp uid jail_dir working_dir script_path args

        # console usage:    python-console port magic

        # TODO: Pass working_dir as argument, let console cd to it

        cmd = ' '.join([trampoline_path, str(uid), jail_path,

                            console_dir, python_path, console_path,

                            str(port), str(magic)])

        print >> sys.stderr, cmd

        res = os.system(cmd)

        print >> sys.stderr, res

        if res == 0:

            # success

            break;

        tries += 1

    if tries == 5:

        raise Exception, "unable to find a free port!"

    # Return port, magic

    req.write(cjson.encode({"host": host, "port": port, "magic": magic}))

def handle_chat(req, kind = "chat"):

    # The request *should* have the following four fields:

    # host, port: Host and port where the console server apparently lives

    # digest, text: Fields to pass along to the console server

    # It simply acts as a proxy to the console server

    if req.method != "POST":

        req.throw_error(req.HTTP_BAD_REQUEST)

    fields = req.get_fieldstorage()

    try:

        host = fields.getfirst("host").value

        port = int(fields.getfirst("port").value)

        digest = fields.getfirst("digest").value

    except AttributeError:

        # Any of the getfirsts returned None

        req.throw_error(req.HTTP_BAD_REQUEST)

    # If text is None, it was probably just an empty line

    try:

        text = fields.getfirst("text").value

    except AttributeError:

        text = ""

    msg = {'cmd':kind, 'text':text, 'digest':digest}

    sok = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    sok.connect((host, port))

    sok.send(cjson.encode(msg))

    buf = cStringIO.StringIO()

    blk = sok.recv(1024)

    while blk:

        buf.write(blk)

        try:

            blk = conn.recv(1024, socket.MSG_DONTWAIT)

        except:

            # Exception thrown if it WOULD block (but we

            # told it not to wait) - ie. we are done

            blk = None

    inp = buf.getvalue()

    sok.close()

    req.content_type = "text/plain"

    req.write(inp)