ENH/TMP: Preliminary support for bash scripts.

 - Changing the Question model to add a language attribute.
 - Moving python_server.py -> code_server.py.
 - Adding functionality to test for Shell scripts.  This is still
   incomplete since the shell code checker seems to have some problems.
 - Modified the xmlrpc_clients to support multiple languages and right
   now two.
 - Using setgid/setuid instead of setegid/seteuid in the code_server.py..
 - Adding a bash example to the sample_questions.py.

The shell script support doesn't quite work yet but this is really a
code_server/checking issue.

1 files changed, 179 insertions, 0 deletions

diff --git a/code_server.py b/code_server.py
new file mode 100755
index 0000000..63f3073
--- /dev/null
+++ b/code_server.py
@@ -0,0 +1,179 @@
+#!/usr/bin/env python
+"""This server runs an XMLRPC server that can be submitted code and tests
+and returns the output.  It *should* be run as root and will run as the user 
+'nobody' so as to minimize any damange by errant code.  This can be configured 
+by editing settings.py to run as many servers as desired.  One can also
+specify the ports on the command line.  Here are examples::
+
+  $ sudo ./code_server.py
+  # Runs servers based on settings.py:SERVER_PORTS one server per port given.
+  
+or::
+
+  $ sudo ./code_server.py 8001 8002 8003 8004 8005
+  # Runs 5 servers on ports specified.
+
+All these servers should be running as nobody.
+"""
+import sys
+import traceback
+from SimpleXMLRPCServer import SimpleXMLRPCServer
+import pwd
+import os
+import stat
+from os.path import isdir, dirname, abspath, join
+import signal
+from multiprocessing import Process
+import subprocess
+
+# Local imports.
+from settings import SERVER_PORTS, SERVER_TIMEOUT
+
+MY_DIR = abspath(dirname(__file__))
+
+def run_as_nobody():
+    """Runs the current process as nobody."""
+    # Set the uid and to that of nobody.
+    nobody = pwd.getpwnam('nobody')
+    os.setgid(nobody.pw_gid)
+    os.setuid(nobody.pw_uid)
+
+################################################################################
+# Python related code.
+
+# Raised when the code times-out.
+# c.f. http://pguides.net/python/timeout-a-function
+class TimeoutException(Exception):
+    pass
+    
+def timeout_handler(signum, frame):
+    """A handler for the ALARM signal."""
+    raise TimeoutException('Code took too long to run.')
+
+def run_python_code(answer, test_code, in_dir=None):
+    """Tests given Python function (`answer`) with the `test_code` supplied.  
+    If the optional `in_dir` keyword argument is supplied it changes the 
+    directory to that directory (it does not change it back to the original when
+    done).  This function also timesout when the function takes more than 
+    SERVER_TIMEOUT seconds to run to prevent runaway code.
+
+    Returns
+    -------
+    
+    A tuple: (success, error message).
+    
+    """
+    if in_dir is not None and isdir(in_dir):
+        os.chdir(in_dir)
+        
+    # Add a new signal handler for the execution of this code.
+    old_handler = signal.signal(signal.SIGALRM, timeout_handler)
+    signal.alarm(SERVER_TIMEOUT)
+     
+    success = False
+    tb = None
+    try:
+        submitted = compile(answer, '<string>', mode='exec')
+        g = {}
+        exec submitted in g
+        _tests = compile(test_code, '<string>', mode='exec')
+        exec _tests in g
+    except TimeoutException:
+        err = 'Code took more than %s seconds to run.'%SERVER_TIMEOUT
+    except AssertionError:
+        type, value, tb = sys.exc_info()
+        info = traceback.extract_tb(tb)
+        fname, lineno, func, text = info[-1]
+        text = str(test_code).splitlines()[lineno-1]
+        err = "{0} {1} in: {2}".format(type.__name__, str(value), text)
+    except:
+        type, value = sys.exc_info()[:2]
+        err = "Error: {0}".format(repr(value))
+    else:
+        success = True
+        err = 'Correct answer'
+    finally:
+        del tb
+        # Set back any original signal handler.
+        signal.signal(signal.SIGALRM, old_handler) 
+        
+    # Cancel the signal if any, see signal.alarm documentation.
+    signal.alarm(0)
+
+    return success, err
+
+################################################################################
+# Run code for Bash.
+def run_bash_code(answer, test_code, in_dir=None):
+
+    """Tests given Bash code  (`answer`) with the `test_code` supplied.  It
+    assumes that there are two parts to the test_code separated by '#++++++'.
+
+    If the optional `in_dir` keyword argument is supplied it changes the 
+    directory to that directory (it does not change it back to the original when
+    done).
+
+    Returns
+    -------
+    
+    A tuple: (success, error message).
+    
+    """
+    if in_dir is not None and isdir(in_dir):
+        os.chdir(in_dir)
+
+    def _set_exec(fname):
+        os.chmod(ref_fname,  stat.S_IRUSR|stat.S_IWUSR|stat.S_IXUSR 
+                            |stat.S_IRGRP|stat.S_IWGRP|stat.S_IXGRP
+                            |stat.S_IROTH|stat.S_IWOTH|stat.S_IXOTH)
+
+    # XXX: fix this to not hardcode it to 6 +'s!
+    reference, args = test_code.split('#++++++')
+    ref_f = open('reference.sh', 'w')
+    ref_f.write(reference); ref_f.close()
+    ref_fname = abspath(ref_f.name)
+    _set_exec(ref_fname)
+    args_f = open('reference.args', 'w')
+    args_f.write(args); args_f.close()
+    _set_exec(args_f.name)
+    submit_f = open('submit.sh', 'w')
+    submit_f.write(answer); submit_f.close()
+    submit_fname = submit_f.name
+    _set_exec(submit_fname)
+
+    tester = join(MY_DIR, 'shell_script_tester.sh')
+
+    # Run the shell code in a subprocess.
+    try:
+        output = subprocess.check_output([tester, ref_fname, submit_fname],
+                                         stderr=subprocess.STDOUT)
+    except subprocess.CalledProcessError, exc:
+        success = False
+        err = 'Error: exist status: %d, message: %s'%(exc.returncode,
+                                                     exc.output)
+    else:
+        success = True
+        err = 'Correct answer'
+
+    return success, err
+
+
+def run_server(port):
+    server = SimpleXMLRPCServer(("localhost", port))
+    server.register_function(run_python_code)
+    server.register_function(run_bash_code)
+    server.serve_forever()
+
+def main():
+    run_as_nobody()
+    if len(sys.argv) == 1:
+        ports = SERVER_PORTS
+    else:
+        ports = [int(x) for x in sys.argv[1:]]
+
+    for port in ports:
+        p = Process(target=run_server,  args=(port,))
+        p.start()
+    
+if __name__ == '__main__':
+    main()