Whitelisted courses now run Python code outside the sandbox.

common/lib/capa/capa/capa_problem.py

@@ -470,6 +470,7 @@ class LoncapaProblem(object):
                     python_path=python_path,
                     cache=self.system.cache,
                     slug=self.problem_id,
+                    unsafely=self.system.can_execute_unsafe_code(),
                 )
             except Exception as err:
                 log.exception("Error while execing script code: " + all_code)

common/lib/capa/capa/responsetypes.py

@@ -294,6 +294,7 @@ class LoncapaResponse(object):
                     python_path=self.context['python_path'],
                     slug=self.id,
                     random_seed=self.context['seed'],
+                    unsafely=self.system.can_execute_unsafe_code(),
                 )
             except Exception as err:
                 msg = 'Error %s in evaluating hint function %s' % (err, hintfn)
@@ -985,6 +986,7 @@ class CustomResponse(LoncapaResponse):
                             python_path=self.context['python_path'],
                             slug=self.id,
                             random_seed=self.context['seed'],
+                            unsafely=self.system.can_execute_unsafe_code(),
                         )
                         return globals_dict['cfn_return']
                     return check_function
@@ -1108,6 +1110,7 @@ class CustomResponse(LoncapaResponse):
                     cache=self.system.cache,
                     slug=self.id,
                     random_seed=self.context['seed'],
+                    unsafely=self.system.can_execute_unsafe_code(),
                 )
             except Exception as err:
                 self._handle_exec_exception(err)
@@ -1838,6 +1841,7 @@ class SchematicResponse(LoncapaResponse):
                 cache=self.system.cache,
                 slug=self.id,
                 random_seed=self.context['seed'],
+                unsafely=self.system.can_execute_unsafe_code(),
             )
         except Exception as err:
             msg = 'Error %s in evaluating SchematicResponse' % err

common/lib/capa/capa/safe_exec/safe_exec.py

@@ -1,6 +1,7 @@
 """Capa's specialized use of codejail.safe_exec."""
 
 from codejail.safe_exec import safe_exec as codejail_safe_exec
+from codejail.safe_exec import not_safe_exec as codejail_not_safe_exec
 from codejail.safe_exec import json_safe, SafeExecException
 from . import lazymod
 from statsd import statsd
@@ -71,7 +72,7 @@ def update_hash(hasher, obj):
 
 
 @statsd.timed('capa.safe_exec.time')
-def safe_exec(code, globals_dict, random_seed=None, python_path=None, cache=None, slug=None):
+def safe_exec(code, globals_dict, random_seed=None, python_path=None, cache=None, slug=None, unsafely=False):
     """
     Execute python code safely.
 
@@ -90,6 +91,8 @@ def safe_exec(code, globals_dict, random_seed=None, python_path=None, cache=None
     `slug` is an arbitrary string, a description that's meaningful to the
     caller, that will be used in log messages.
 
+    If `unsafely` is true, then the code will actually be executed without sandboxing.
+
     """
     # Check the cache for a previous result.
     if cache:
@@ -111,9 +114,15 @@ def safe_exec(code, globals_dict, random_seed=None, python_path=None, cache=None
     # Create the complete code we'll run.
     code_prolog = CODE_PROLOG % random_seed
 
+    # Decide which code executor to use.
+    if unsafely:
+        exec_fn = codejail_not_safe_exec
+    else:
+        exec_fn = codejail_safe_exec
+
     # Run the code!  Results are side effects in globals_dict.
     try:
-        codejail_safe_exec(
+        exec_fn(
             code_prolog + LAZY_IMPORTS + code, globals_dict,
             python_path=python_path, slug=slug,
         )

common/lib/capa/capa/safe_exec/tests/test_safe_exec.py

@@ -1,13 +1,17 @@
 """Test safe_exec.py"""
 
 import hashlib
+import os
 import os.path
 import random
 import textwrap
 import unittest
 
+from nose.plugins.skip import SkipTest
+
 from capa.safe_exec import safe_exec, update_hash
 from codejail.safe_exec import SafeExecException
+from codejail.jail_code import is_configured
 
 
 class TestSafeExec(unittest.TestCase):
@@ -68,6 +72,24 @@ class TestSafeExec(unittest.TestCase):
         self.assertIn("ZeroDivisionError", cm.exception.message)
 
 
+class TestSafeOrNot(unittest.TestCase):
+    def test_cant_do_something_forbidden(self):
+        # Can't test for forbiddenness if CodeJail isn't configured for python.
+        if not is_configured("python"):
+            raise SkipTest
+
+        g = {}
+        with self.assertRaises(SafeExecException) as cm:
+            safe_exec("import os; files = os.listdir('/')", g)
+        self.assertIn("OSError", cm.exception.message)
+        self.assertIn("Permission denied", cm.exception.message)
+
+    def test_can_do_something_forbidden_if_run_unsafely(self):
+        g = {}
+        safe_exec("import os; files = os.listdir('/')", g, unsafely=True)
+        self.assertEqual(g['files'], os.listdir('/'))
+
+
 class DictCache(object):
     """A cache implementation over a simple dict, for testing."""
 

requirements/edx/github.txt

@@ -9,5 +9,5 @@
 
 # Our libraries:
 -e git+https://github.com/edx/XBlock.git@2144a25d#egg=XBlock
--e git+https://github.com/edx/codejail.git@5fb5fa0#egg=codejail
+-e git+https://github.com/edx/codejail.git@0a1b468#egg=codejail
 -e git+https://github.com/edx/diff-cover.git@v0.1.0#egg=diff_cover