Merge pull request #75 from MarcCote/fix_buffer_overflow

Truncate very long action to avoid buffer overflow.

Author: MarcCote

jericho/jericho.py

@@ -36,6 +36,9 @@
 JERICHO_PATH = importlib.resources.files("jericho")
 FROTZ_LIB_PATH = os.path.join(JERICHO_PATH, 'libfrotz.so')
 
+# The buffer size for actions in frotz. -2 to allow for newline and null terminator.
+INPUT_BUFFER_SIZE = 200 - 2
+
 # Function to unload a shared library.
 dlclose_func = CDLL(None).dlclose  # This WON'T work on Win
 dlclose_func.argtypes = [c_void_p]
@@ -361,6 +364,10 @@ class UnsupportedGameWarning(UserWarning):
     pass
 
 
+class TruncatedInputActionWarning(UserWarning):
+    pass
+
+
 class FrotzEnv():
     """
     The Frotz Environment is a fast interface to Z-Machine games.
@@ -465,9 +472,19 @@ def step(self, action):
         the immediate reward, a boolean indicating whether the game is over,\
         and a dictionary of info.
         :rtype: string, float, boolean, dictionary
+
+        Note:
+        - The action is converted to bytes and truncated to 198 characters.
         '''
+        action_bytes = action.encode('utf-8')
+        if len(action_bytes) > INPUT_BUFFER_SIZE:
+            action_bytes = action_bytes[:INPUT_BUFFER_SIZE]
+            msg = ("Once converted to bytes, actions should have less than 198 characters."
+                   " Action '{}' was truncated to '{}'.".format(action, action_bytes.decode()))
+            warnings.warn(msg, TruncatedInputActionWarning)
+
         old_score = self.frotz_lib.get_score()
-        next_state = self.frotz_lib.step((action+'\n').encode('utf-8')).decode('cp1252')
+        next_state = self.frotz_lib.step(action_bytes + b'\n').decode('cp1252')
         score = self.frotz_lib.get_score()
         reward = score - old_score
         return next_state, reward, (self.game_over() or self.victory()),\

jericho/version.py

@@ -1 +1 @@
-__version__ = '3.2.0'
+__version__ = '3.3.0'

tests/test_jericho.py

@@ -127,3 +127,19 @@ def test_saving_opcode_in_state():
         else:
             obs, rew, done, info = env.step(cmd)
             assert not env._emulator_halted()
+
+
+def test_very_long_action():
+    rom = pjoin(DATA_PATH, "905.z5")
+    env = jericho.FrotzEnv(rom)
+    env.reset()
+
+    long_command = "It's a " + "very " * 36 + "long action!"
+    assert len(long_command) == 199
+    env.step(long_command)
+    env.step(long_command * 2)
+
+    long_command = "It's a " + "très " * 36 + "long action!"
+    assert len(long_command) == 199
+    env.step(long_command)
+    env.step(long_command * 2)