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security: check if shared memory belongs to current user and is only … #43

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security: check if shared memory belongs to current user and is only … #43

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20 changes: 20 additions & 0 deletions shared_memory_dict/dict.py
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
import logging
import os
import sys
import warnings
from contextlib import contextmanager
Expand Down Expand Up @@ -157,13 +158,32 @@ def _get_or_create_memory_block(
self, name: str, size: int
) -> SharedMemory:
try:
self.check_security(name)
return SharedMemory(name=name)
except FileNotFoundError:
shm = SharedMemory(name=name, create=True, size=size)
data = self._serializer.dumps({})
shm.buf[: len(data)] = data
return shm

def check_security(self, name: str) -> None:
"""Check if shared memory belongs to and is only read+writeable
for the current user"""
if os.name == 'nt':
return

if '/' in name:
raise TypeError('Name must not contain "/".')

shm_file = os.path.join('/dev/shm', name)
stat = os.stat(shm_file)
if (
stat.st_uid != os.getuid()
or stat.st_gid != os.getgid()
or stat.st_mode != 0o100600
):
os.unlink(shm_file)

def _save_memory(self, db: Dict[str, Any]) -> None:
data = self._serializer.dumps(db)
try:
Expand Down