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# 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
# Module: Interpret
# Author: Matt Giuca
# Date: 20/12/2007
# Runs a student script in a safe execution environment.
from common import studpath
import conf
import functools
import os
import pwd
import subprocess
def interpret_file(req, owner, filename, interpreter):
"""Serves a file by interpreting it using one of IVLE's builtin
interpreters. All interpreters are intended to run in the user's jail. The
jail location is provided as an argument to the interpreter but it is up
to the individual interpreters to create the jail.
req: An IVLE request object.
owner: Username of the user who owns the file being served.
filename: Filename in the local file system.
interpreter: A function object to call.
"""
# Make sure the file exists (otherwise some interpreters may not actually
# complain).
# Don't test for execute permission, that will only be required for
# certain interpreters.
if not os.access(filename, os.R_OK):
req.throw_error(req.HTTP_NOT_FOUND)
# Get the UID of the owner of the file
# (Note: files are executed by their owners, not the logged in user.
# This ensures users are responsible for their own programs and also
# allows them to be executed by the public).
try:
(_,_,uid,_,_,_,_) = pwd.getpwnam(owner)
except KeyError:
# The user does not exist. This should have already failed the
# previous test.
req.throw_error(req.HTTP_INTERNAL_SERVER_ERROR)
# Split up req.path again, this time with respect to the jail
(_, jail_dir, path) = studpath.url_to_jailpaths(req.path)
path = os.path.join('/', path)
(working_dir, _) = os.path.split(path)
# jail_dir is the absolute jail directory.
# path is the filename relative to the user's jail.
# working_dir is the directory containing the file relative to the user's
# jail.
# (Note that paths "relative" to the jail actually begin with a '/' as
# they are absolute in the jailspace)
return interpreter(uid, jail_dir, working_dir, path, req)
# Used to store mutable data
class Dummy:
pass
def execute_cgi(interpreter, trampoline, uid, jail_dir, working_dir,
script_path, req):
"""
trampoline: Full path on the local system to the CGI wrapper program
being executed.
uid: User ID of the owner of the file.
jail_dir: Absolute path of owner's jail directory.
working_dir: Directory containing the script file relative to owner's
jail.
script_path: CGI script relative to the owner's jail.
req: IVLE request object.
The called CGI wrapper application shall be called using popen and receive
the HTTP body on stdin. It shall receive the CGI environment variables to
its environment.
"""
# Get the student program's directory and execute it from that context.
(tramp_dir, _) = os.path.split(trampoline)
# TODO: Don't create a file if the body length is known to be 0
# Write the HTTP body to a temporary file so it can be passed as a *real*
# file to popen.
f = os.tmpfile()
body = req.read()
if body is not None:
f.write(body)
f.flush()
f.seek(0) # Rewind, for reading
# usage: tramp uid jail_dir working_dir script_path
pid = subprocess.Popen(
[trampoline, str(uid), jail_dir, working_dir, interpreter,
script_path],
stdin=f, stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
cwd=tramp_dir)
# process_cgi_line: Reads a single line of CGI output and processes it.
# Prints to req, and also does fancy HTML warnings if Content-Type
# omitted.
cgiflags = Dummy()
cgiflags.got_cgi_header = False
cgiflags.started_cgi_body = False
cgiflags.wrote_html_warning = False
def process_cgi_line(line):
# FIXME? Issue with binary files (processing per-line?)
if cgiflags.started_cgi_body:
# FIXME: HTML escape text if wrote_html_warning
req.write(line)
else:
# Read CGI headers
if line.strip() == "" and cgiflags.got_cgi_header:
cgiflags.started_cgi_body = True
elif line.startswith("Content-Type:"):
req.content_type = line[13:].strip()
cgiflags.got_cgi_header = True
elif line.startswith("Location:"):
# TODO
cgiflags.got_cgi_header = True
elif line.startswith("Status:"):
# TODO
cgiflags.got_cgi_header = True
elif cgiflags.got_cgi_header:
# Invalid header
# TODO
req.write("Invalid header")
pass
else:
# Assume the user is not printing headers and give a warning
# about that.
# User program did not print header.
# Make a fancy HTML warning for them.
req.content_type = "text/html"
req.write("""<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type"
content="text/html; charset=utf-8" />
</head>
<body style="margin: 0; padding: 0; font-family: sans;">
<div style="background-color: #faa; border-bottom: 1px solid black;
padding: 8px;">
<p><strong>Warning</strong>: You did not print a "Content-Type" header.
CGI requires you to print some content type. You may wish to try:</p>
<pre style="margin-left: 1em">Content-Type: text/html</pre>
</div>
<div style="margin: 8px;">
<pre>
""")
cgiflags.got_cgi_header = True
cgiflags.wrote_html_warning = True
cgiflags.started_cgi_body = True
req.write(line)
# Read from the process's stdout into req
for line in pid.stdout:
process_cgi_line(line)
# If we wrote an HTML warning header, write the footer
if cgiflags.wrote_html_warning:
req.write("""</pre>
</div>
</body>
</html>""")
# TODO: Replace mytest with cgi trampoline handler script
location_cgi_python = os.path.join(conf.ivle_install_dir,
"bin/trampoline")
# Mapping of interpreter names (as given in conf/app/server.py) to
# interpreter functions.
interpreter_objects = {
'cgi-python'
: functools.partial(execute_cgi, "/usr/bin/python",
location_cgi_python),
# Should also have:
# cgi-generic
# python-server-page
}
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