~azzar1/unity/add-show-desktop-key : revision 89

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# IVLE

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#

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# This program is free software; you can redistribute it and/or modify

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# it under the terms of the GNU General Public License as published by

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# the Free Software Foundation; either version 2 of the License, or

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# (at your option) any later version.

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#

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# This program is distributed in the hope that it will be useful,

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# but WITHOUT ANY WARRANTY; without even the implied warranty of

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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

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# GNU General Public License for more details.

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#

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# You should have received a copy of the GNU General Public License

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# along with this program; if not, write to the Free Software

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

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# Module: Interpret

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# Author: Matt Giuca

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# Date: 20/12/2007

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# Runs a student script in a safe execution environment.

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from common import studpath

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import conf

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import functools

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import os

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import pwd

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import subprocess

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def interpret_file(req, owner, filename, interpreter):

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"""Serves a file by interpreting it using one of IVLE's builtin

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interpreters. All interpreters are intended to run in the user's jail. The

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jail location is provided as an argument to the interpreter but it is up

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to the individual interpreters to create the jail.

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req: An IVLE request object.

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owner: Username of the user who owns the file being served.

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filename: Filename in the local file system.

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interpreter: A function object to call.

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"""

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# Make sure the file exists (otherwise some interpreters may not actually

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# complain).

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# Don't test for execute permission, that will only be required for

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# certain interpreters.

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if not os.access(filename, os.R_OK):

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req.throw_error(req.HTTP_NOT_FOUND)

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# Get the UID of the owner of the file

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# (Note: files are executed by their owners, not the logged in user.

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# This ensures users are responsible for their own programs and also

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# allows them to be executed by the public).

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try:

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(_,_,uid,_,_,_,_) = pwd.getpwnam(owner)

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except KeyError:

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

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# previous test.

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req.throw_error(req.HTTP_INTERNAL_SERVER_ERROR)

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# Split up req.path again, this time with respect to the jail

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(_, jail_dir, path) = studpath.url_to_jailpaths(req.path)

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path = os.path.join('/', path)

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(working_dir, _) = os.path.split(path)

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# Now jail_dir is the jail directory relative to the jails root.

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# Note that the trampoline has jails root hard-coded for security.

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# path is the filename relative to the user's jail.

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# working_dir is the directory containing the file relative to the user's

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# jail.

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# (Note that paths "relative" to the jail actually begin with a '/' as

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# they are absolute in the jailspace)

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return interpreter(uid, jail_dir, working_dir, path, req)

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# Used to store mutable data

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class Dummy:

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pass

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def execute_cgi(trampoline, uid, jail_dir, working_dir, script_path, req):

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"""

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trampoline: Full path on the local system to the CGI wrapper program

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being executed.

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uid: User ID of the owner of the file.

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jail_dir: Owner's jail directory relative to the jails root.

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working_dir: Directory containing the script file relative to owner's

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jail.

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script_path: CGI script relative to the owner's jail.

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req: IVLE request object.

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The called CGI wrapper application shall be called using popen and receive

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the HTTP body on stdin. It shall receive the CGI environment variables to

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its environment.

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"""

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# Get the student program's directory and execute it from that context.

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(tramp_dir, _) = os.path.split(trampoline)

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# TODO: Don't create a file if the body length is known to be 0

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# Write the HTTP body to a temporary file so it can be passed as a *real*

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# file to popen.

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f = os.tmpfile()

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body = req.read()

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if body is not None:

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f.write(body)

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f.flush()

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f.seek(0) # Rewind, for reading

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# usage: tramp uid jail_dir working_dir script_path

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pid = subprocess.Popen(

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[trampoline, str(uid), jail_dir, working_dir, script_path],

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stdin=f, stdout=subprocess.PIPE, cwd=tramp_dir)

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# process_cgi_line: Reads a single line of CGI output and processes it.

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# Prints to req, and also does fancy HTML warnings if Content-Type

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# omitted.

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cgiflags = Dummy()

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cgiflags.got_cgi_header = False

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cgiflags.started_cgi_body = False

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cgiflags.wrote_html_warning = False

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def process_cgi_line(line):

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# FIXME? Issue with binary files (processing per-line?)

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if cgiflags.started_cgi_body:

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# FIXME: HTML escape text if wrote_html_warning

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req.write(line)

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else:

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# Read CGI headers

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if line.strip() == "" and cgiflags.got_cgi_header:

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cgiflags.started_cgi_body = True

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elif line.startswith("Content-Type:"):

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req.content_type = line[13:].strip()

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cgiflags.got_cgi_header = True

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elif line.startswith("Location:"):

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# TODO

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cgiflags.got_cgi_header = True

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elif line.startswith("Status:"):

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# TODO

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cgiflags.got_cgi_header = True

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elif cgiflags.got_cgi_header:

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# Invalid header

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# TODO

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req.write("Invalid header")

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pass

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else:

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# Assume the user is not printing headers and give a warning

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# about that.

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# User program did not print header.

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# Make a fancy HTML warning for them.

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req.content_type = "text/html"

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req.write("""<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"

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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

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<head>

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content="text/html; charset=utf-8" />

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</head>

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<div style="background-color: #faa; border-bottom: 1px solid black;

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padding: 8px;">

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<p><strong>Warning</strong>: You did not print a "Content-Type" header.

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CGI requires you to print some content type. You may wish to try:</p>

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<pre style="margin-left: 1em">Content-Type: text/html</pre>

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</div>

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<pre>

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""")

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cgiflags.got_cgi_header = True

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cgiflags.wrote_html_warning = True

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cgiflags.started_cgi_body = True

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req.write(line)

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# Read from the process's stdout into req

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for line in pid.stdout:

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process_cgi_line(line)

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# If we wrote an HTML warning header, write the footer

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if cgiflags.wrote_html_warning:

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req.write("""</pre>

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</div>

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</body>

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</html>""")

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# TODO: Replace mytest with cgi trampoline handler script

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location_cgi_python = os.path.join(conf.ivlepath, "bin/trampoline-python")

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# Mapping of interpreter names (as given in conf/app/server.py) to

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# interpreter functions.

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interpreter_objects = {

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'cgi-python'

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: functools.partial(execute_cgi, location_cgi_python),

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# Should also have:

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# cgi-generic

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# python-server-page

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}

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