From 76cbfe9d620ca66a374b828c011c937918f80c2c Mon Sep 17 00:00:00 2001 From: Timotej Lazar Date: Wed, 7 Oct 2015 17:25:35 +0200 Subject: Add a sandbox for Python interpreter Switch to user "nobody" and set additional limits. --- server/python_session.py | 28 ++++++++++++++++++++-------- 1 file changed, 20 insertions(+), 8 deletions(-) (limited to 'server') diff --git a/server/python_session.py b/server/python_session.py index 24d33b0..f4c482c 100644 --- a/server/python_session.py +++ b/server/python_session.py @@ -116,15 +116,27 @@ class PythonSession(server.LanguageSession): self._sent_hints.extend(hints) def _interpreter(control, callback): - directory = os.path.dirname(os.path.realpath(__file__)) - # TODO drop privileges using a wrapper - script = os.path.join(directory, '..', 'python', 'interpreter.py') + basedir = os.path.split(os.path.dirname(os.path.realpath(__file__)))[0] + script = os.path.join(basedir, 'python', 'runner', 'interpreter.py') + + # If the sandbox wrapper exists, use it to switch to user "nobody" and + # enforce additional limits. Unless the daemon is running as root we are + # not able to signal nobody's PIDs, so switch user again for the killing. + sandbox = os.path.join(basedir, 'python', 'runner', 'sandbox') + terminator = os.path.join(basedir, 'python', 'runner', 'terminator') + if os.path.exists(sandbox) and os.path.exists(terminator): + newuser = 'nobody' # TODO make this configurable + args = [sandbox, newuser, script] + kill = lambda proc, sig: subprocess.call([terminator, newuser, str(proc.pid), str(sig)]) + else: + args = [script] + kill = lambda proc, sig: proc.send_signal(sig) proc = None while True: # Ensure the interpreter process is running. if proc is None: - proc = subprocess.Popen([script], + proc = subprocess.Popen(args, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.STDOUT) @@ -143,7 +155,7 @@ def _interpreter(control, callback): proc.stdin.write(data.encode('utf-8')) proc.stdin.flush() elif cmd == 'stop': - proc.send_signal(signal.SIGINT) + kill(proc, signal.SIGINT) elif cmd == 'done': break except: @@ -155,7 +167,7 @@ def _interpreter(control, callback): data = proc.stdout.read() if data: if len(data) > 20000: - proc.kill() + kill(proc, signal.SIGKILL) proc = None callback('Child killed for talking too much.\n') else: @@ -169,7 +181,7 @@ def _interpreter(control, callback): elif retcode == -31: # killed by seccomp callback('Child killed due to sandbox misbehavior.\n') else: - callback('Child exited with status "{}".\n'.format(retcode)) + callback('Child exited with status {}.\n'.format(retcode)) proc = None # TODO we should select() on control and proc.stdout instead of polling @@ -177,7 +189,7 @@ def _interpreter(control, callback): # We are done, kill the child. if proc is not None: - proc.kill() + kill(proc, signal.SIGKILL) # Execute [code] and evaluate [expr]. Input is given by the string [stdin]. # Return result of evaluation, the contents of stdout and stderr, and the -- cgit v1.2.1