#!/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. This will also start a server pool that defaults to port 50000 and is configurable in settings.py:SERVER_POOL_PORT. This port exposes a `get_server_port` function that returns an available server. """ import sys import traceback from SimpleXMLRPCServer import SimpleXMLRPCServer import pwd import os import stat from os.path import isdir, dirname, abspath, join, isfile import signal from multiprocessing import Process, Queue import subprocess import re import json # Local imports. from settings import SERVER_PORTS, SERVER_TIMEOUT, SERVER_POOL_PORT MY_DIR = abspath(dirname(__file__)) def run_as_nobody(): """Runs the current process as nobody.""" # Set the effective uid and to that of nobody. nobody = pwd.getpwnam('nobody') os.setegid(nobody.pw_gid) os.seteuid(nobody.pw_uid) # 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 create_signal_handler(): """Add a new signal handler for the execution of this code.""" prev_handler = signal.signal(signal.SIGALRM, timeout_handler) signal.alarm(SERVER_TIMEOUT) return prev_handler def set_original_signal_handler(old_handler=None): """Set back any original signal handler.""" if old_handler is not None: signal.signal(signal.SIGALRM, old_handler) return else: raise Exception("Signal Handler: object cannot be NoneType") def delete_signal_handler(): signal.alarm(0) return ############################################################################### # `TestCode` class. ############################################################################### class TestCode(object): """Evaluates and tests the code obtained from Code Server""" def __init__(self, test_parameter, language, user_answer, ref_code_path=None, in_dir=None): msg = 'Code took more than %s seconds to run. You probably '\ 'have an infinite loop in your code.' % SERVER_TIMEOUT self.timeout_msg = msg self.test_parameter = test_parameter self.language = language self.user_answer = user_answer self.ref_code_path = ref_code_path self.in_dir = in_dir def run_code(self): """Tests given code (`answer`) with the test cases based on given arguments. The ref_code_path is a path to the reference code. The reference code will call the function submitted by the student. The reference code will check for the expected output. If the path's start with a "/" then we assume they are absolute paths. If not, we assume they are relative paths w.r.t. the location of this code_server script. 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). """ success = False prev_handler = None methods = {"python": 'evaluate_python_code', "bash": 'evaluate_bash_code', "C": "evaluate_c_cpp_java_code", "C++": "evaluate_c_cpp_java_code", "java": "evaluate_c_cpp_java_code", "scilab": "evaluate_scilab_code", } get_method_based_on_lang = methods[self.language] self._change_dir(self.in_dir) # Add a new signal handler for the execution of this code. prev_handler = create_signal_handler() success = False # Do whatever testing needed. try: evaluate_code = getattr(self, get_method_based_on_lang) success, err = evaluate_code() except TimeoutException: err = self.timeout_msg except: type, value = sys.exc_info()[:2] err = "Error: {0}".format(repr(value)) finally: # Set back any original signal handler. set_original_signal_handler(prev_handler) # Cancel the signal delete_signal_handler() result = {'success': success, 'error': err} return result def evaluate_python_code(self): success = False try: tb = None test_code = self._create_test_case() submitted = compile(self.user_answer, '', mode='exec') g = {} exec submitted in g _tests = compile(test_code, '', mode='exec') exec _tests in g 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) else: success = True err = 'Correct answer' del tb return success, err def evaluate_c_cpp_java_code(self): submit_path = self._create_submit_code_file() ref_path, test_case_path = self._set_test_code_file_path() success = False success, err = self._check_code(ref_path, submit_path) # Delete the created file. os.remove(submit_path) return success, err def evaluate_scilab_code(self): submit_path = self._create_submit_code_file() ref_path, test_case_path = self._set_test_code_file_path() success = False cmd = 'printf "lines(0)\nexec(\'{0}\',2);\nquit();"'.format(ref_path) cmd += ' | timeout 8 scilab-cli -nb' ret = self._run_command(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE) proc, stdout, stderr = ret # Get only the error. stderr = self._get_error(stdout) if stderr is None: # Clean output stdout = self._strip_output(stdout) if proc.returncode == 5: success, err = True, "Correct answer" else: err = add_err + stdout else: err = add_err + stderr # Delete the created file. os.remove(submit_path) return success, err def evaluate_bash_code(self): submit_path = self._create_submit_code_file() ref_path, test_case_path = self._set_test_code_file_path() success = False success, err = self.check_bash_script(ref_path, submit_path, test_case_path) # Delete the created file. os.remove(submit_path) return success, err def _create_submit_code_file(self): """ Write the code (`answer`) to a file and set the file path""" user_answer_file = {'C': 'submit.c', 'java': 'Test.java', 'scilab': 'function.sci', 'C++': 'submitstd.cpp', 'bash': 'submit.sh'} # File extension depending on the question language submit_f = open(user_answer_file.get(self.language), 'w') submit_f.write(self.user_answer.lstrip()) submit_f.close() submit_path = abspath(submit_f.name) if self.language == "bash": self._set_exec(submit_path) return submit_path def _set_test_code_file_path(self): ref_path, test_case_path = self.ref_code_path.split(',') if ref_path and not ref_path.startswith('/'): ref_path = join(MY_DIR, ref_path) if test_case_path and not test_case_path.startswith('/'): test_case_path = join(MY_DIR, test_case_path) return ref_path, test_case_path def _check_code(self, ref_code_path, submit_code_path): """ Function validates student code using instructor code as reference.The first argument ref_code_path, is the path to instructor code, it is assumed to have executable permission. The second argument submit_code_path, is the path to the student code, it is assumed to have executable permission. Returns -------- returns (True, "Correct answer") : If the student function returns expected output when called by reference code. returns (False, error_msg): If the student function fails to return expected output when called by reference code. Returns (False, error_msg): If mandatory arguments are not files or if the required permissions are not given to the file(s). """ language_dependent_path = { 'c_user_output_path': os.getcwd() + '/output', 'c_ref_output_path': os.getcwd() + '/executable', 'java_student_directory': os.getcwd() + '/', # 'java_student_file_name': 'Test', 'java_ref_file_name': (ref_code_path.split('/')[-1]).split('.')[0], } language_dependent_var = { 'C': {'compile_command': 'g++ {0} -c -o {1}'.format(submit_code_path, language_dependent_path.get('c_user_output_path')), 'compile_main': 'g++ {0} {1} -o {2}'.format(ref_code_path, language_dependent_path.get('c_user_output_path'), language_dependent_path.get('c_ref_output_path')), 'run_command_args': [language_dependent_path.get('c_ref_output_path')], 'remove_user_output': language_dependent_path.get('c_user_output_path'), 'remove_ref_output': language_dependent_path.get('c_ref_output_path') }, 'java':{'compile_command': 'javac {0}'.format(submit_code_path), 'compile_main': 'javac {0} -classpath {1} -d {2}'.format(ref_code_path, language_dependent_path.get('java_student_directory'), language_dependent_path.get('java_student_directory')), 'run_command_args': "java -cp {0} {1}".format( language_dependent_path.get('java_student_directory'), language_dependent_path.get('java_ref_file_name')), 'remove_user_output': "%s%s.class".format( language_dependent_path.get('java_student_directory'), 'Test'), 'remove_ref_output': "%s%s.class".format( language_dependent_path.get('java_student_directory'), language_dependent_path.get('java_ref_file_name')), } } if not isfile(ref_code_path): return False, "No file at %s or Incorrect path" % ref_code_path if not isfile(submit_code_path): return False, 'No file at %s or Incorrect path' % submit_code_path success = False # output_path = os.getcwd() + '/output' compile_command = language_dependent_var.get(self.language).get('compile_command') ret = self._compile_command(compile_command) proc, stdnt_stderr = ret if self.language == "java": stdnt_stderr = self._remove_null_substitute_char(stdnt_stderr) # Only if compilation is successful, the program is executed # And tested with testcases if stdnt_stderr == '': compile_main = language_dependent_var.get(self.language).get('compile_main') ret = self._compile_command(compile_main) proc, main_err = ret if self.language == "java": main_err = self._remove_null_substitute_char(main_err) if main_err == '': run_command_args = language_dependent_var.get(self.language).get('run_command_args') ret = self._run_command(run_command_args, stdin=None, stdout=subprocess.PIPE, stderr=subprocess.PIPE) proc, stdout, stderr = ret if proc.returncode == 0: success, err = True, "Correct answer" else: err = stdout + "\n" + stderr os.remove(language_dependent_var.get(self.language).get('remove_ref_output')) else: err = "Error:" try: error_lines = main_err.splitlines() for e in error_lines: if ':' in e: err = err + "\n" + e.split(":", 1)[1] else: err = err + "\n" + e except: err = err + "\n" + main_err os.remove(language_dependent_var.get(self.language).get('remove_user_output')) else: err = "Compilation Error:" try: error_lines = stdnt_stderr.splitlines() for e in error_lines: if ':' in e: err = err + "\n" + e.split(":", 1)[1] else: err = err + "\n" + e except: err = err + "\n" + stdnt_stderr return success, err def check_bash_script(self, ref_path, submit_path, test_case_path=None): """ Function validates student script using instructor script as reference. Test cases can optionally be provided. The first argument ref_path, is the path to instructor script, it is assumed to have executable permission. The second argument submit_path, is the path to the student script, it is assumed to have executable permission. The Third optional argument is the path to test the scripts. Each line in this file is a test case and each test case is passed to the script as standard arguments. Returns -------- returns (True, "Correct answer") : If the student script passes all test cases/have same output, when compared to the instructor script returns (False, error_msg): If the student script fails a single test/have dissimilar output, when compared to the instructor script. Returns (False, error_msg): If mandatory arguments are not files or if the required permissions are not given to the file(s). """ if not isfile(ref_path): return False, "No file at %s or Incorrect path" % ref_path if not isfile(submit_path): return False, "No file at %s or Incorrect path" % submit_path if not os.access(ref_path, os.X_OK): return False, "Script %s is not executable" % ref_path if not os.access(submit_path, os.X_OK): return False, "Script %s is not executable" % submit_path if test_case_path is None or "": ret = self._run_command(ref_path, stdin=None, stdout=subprocess.PIPE, stderr=subprocess.PIPE) proc, inst_stdout, inst_stderr = ret ret = self._run_command(submit_path, stdin=None, stdout=subprocess.PIPE, stderr=subprocess.PIPE) proc, stdnt_stdout, stdnt_stderr = ret if inst_stdout == stdnt_stdout: return True, "Correct answer" else: err = "Error: expected %s, got %s" % (inst_stderr, stdnt_stderr) return False, err else: if not isfile(test_case_path): return False, "No test case at %s" % test_case_path if not os.access(ref_path, os.R_OK): return False, "Test script %s, not readable" % test_case_path valid_answer = True # We initially make it one, so that we can # stop once a test case fails loop_count = 0 # Loop count has to be greater than or # equal to one. # Useful for caching things like empty # test files,etc. test_cases = open(test_case_path).readlines() num_lines = len(test_cases) for test_case in test_cases: loop_count += 1 if valid_answer: args = [ref_path] + [x for x in test_case.split()] ret = self._run_command(args, stdin=None, stdout=subprocess.PIPE, stderr=subprocess.PIPE) proc, inst_stdout, inst_stderr = ret args = [submit_path]+[x for x in test_case.split()] ret = self._run_command(args, stdin=None, stdout=subprocess.PIPE, stderr=subprocess.PIPE) proc, stdnt_stdout, stdnt_stderr = ret valid_answer = inst_stdout == stdnt_stdout if valid_answer and (num_lines == loop_count): return True, "Correct answer" else: err = "Error:expected %s, got %s" % (inst_stdout+inst_stderr, stdnt_stdout+stdnt_stderr) return False, err def _run_command(self, cmd_args, *args, **kw): """Run a command in a subprocess while blocking, the process is killed if it takes more than 2 seconds to run. Return the Popen object, the stdout and stderr. """ try: proc = subprocess.Popen(cmd_args, *args, **kw) stdout, stderr = proc.communicate() except TimeoutException: # Runaway code, so kill it. proc.kill() # Re-raise exception. raise return proc, stdout, stderr def _compile_command(self, cmd, *args, **kw): """Compiles C/C++/java code and returns errors if any. Run a command in a subprocess while blocking, the process is killed if it takes more than 2 seconds to run. Return the Popen object, the stderr. """ try: proc_compile = subprocess.Popen(cmd, shell=True, stdin=None, stdout=subprocess.PIPE, stderr=subprocess.PIPE) out, err = proc_compile.communicate() except TimeoutException: # Runaway code, so kill it. proc_compile.kill() # Re-raise exception. raise return proc_compile, err def _remove_null_substitute_char(self, string): """Returns a string without any null and substitute characters""" stripped = "" for c in string: if ord(c) is not 26 and ord(c) is not 0: stripped = stripped + c return ''.join(stripped) def _remove_scilab_exit(self, string): """ Removes exit, quit and abort from the scilab code """ new_string = "" i=0 for line in string.splitlines(): new_line = re.sub(r"exit.*$","",line) new_line = re.sub(r"quit.*$","",new_line) new_line = re.sub(r"abort.*$","",new_line) if line != new_line: i=i+1 new_string = new_string +'\n'+ new_line return new_string, i def _get_error(self, string): """ Fetches only the error from the string. Returns None if no error. """ obj = re.search("!.+\n.+",string); if obj: return obj.group() return None def _strip_output(self, out): """ Cleans whitespace from the output """ strip_out = "Message" for l in out.split('\n'): if l.strip(): strip_out = strip_out+"\n"+l.strip() return strip_out def _set_exec(self, fname): os.chmod(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) def _create_test_case(self): """ Create assert based test cases in python """ test_code = "" for test_case in self.test_parameter: pos_args = ", ".join(str(i) for i in test_case.get('pos_args')) if test_case.get('pos_args') \ else "" kw_args = ", ".join(str(k+"="+a) for k, a in test_case.get('kw_args').iteritems()) \ if test_case.get('kw_args') else "" args = pos_args + ", " + kw_args if pos_args and kw_args else pos_args or kw_args tcode = "assert {0}({1}) == {2}" \ .format(test_case.get('func_name'), args, test_case.get('expected_answer')) test_code += tcode + "\n" return test_code def _change_dir(self, in_dir): if in_dir is not None and isdir(in_dir): os.chdir(in_dir) ############################################################################### # `CodeServer` class. ############################################################################### class CodeServer(object): """A code server that executes user submitted test code, tests it and reports if the code was correct or not. """ def __init__(self, port, queue): self.port = port self.queue = queue def checker(self, info_parameter, in_dir=None): """Calls the TestCode Class to test the current code""" info_parameter = json.loads(info_parameter) test_parameter = info_parameter.get("test_parameter") language = info_parameter.get("language") user_answer = info_parameter.get("user_answer") ref_code_path = info_parameter.get("ref_code_path") tc = TestCode(test_parameter, language, user_answer, ref_code_path, in_dir) result = tc.run_code() # Put us back into the server pool queue since we are free now. self.queue.put(self.port) return json.dumps(result) def run(self): """Run XMLRPC server, serving our methods.""" server = SimpleXMLRPCServer(("localhost", self.port)) self.server = server server.register_instance(self) self.queue.put(self.port) server.serve_forever() ############################################################################### # `ServerPool` class. ############################################################################### class ServerPool(object): """Manages a pool of CodeServer objects.""" def __init__(self, ports, pool_port=50000): """Create a pool of servers. Uses a shared Queue to get available servers. Parameters ---------- ports : list(int) List of ports at which the CodeServer's should run. pool_port : int Port at which the server pool should serve. """ self.my_port = pool_port self.ports = ports queue = Queue(maxsize=len(ports)) self.queue = queue servers = [] for port in ports: server = CodeServer(port, queue) servers.append(server) p = Process(target=server.run) p.start() self.servers = servers def get_server_port(self): """Get available server port from ones in the pool. This will block till it gets an available server. """ q = self.queue was_waiting = True if q.empty() else False port = q.get() if was_waiting: print '*'*80 print "No available servers, was waiting but got server \ later at %d." % port print '*'*80 sys.stdout.flush() return port def run(self): """Run server which returns an available server port where code can be executed. """ server = SimpleXMLRPCServer(("localhost", self.my_port)) self.server = server server.register_instance(self) 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:]] server_pool = ServerPool(ports=ports, pool_port=SERVER_POOL_PORT) server_pool.run() if __name__ == '__main__': main()