import errno import os import tempfile from django.conf import settings from django.contrib.sessions.backends.base import SessionBase, CreateError from django.core.exceptions import SuspiciousOperation, ImproperlyConfigured class SessionStore(SessionBase): """ Implements a file based session store. """ def __init__(self, session_key=None): self.storage_path = getattr(settings, "SESSION_FILE_PATH", None) if not self.storage_path: self.storage_path = tempfile.gettempdir() # Make sure the storage path is valid. if not os.path.isdir(self.storage_path): raise ImproperlyConfigured( "The session storage path %r doesn't exist. Please set your" " SESSION_FILE_PATH setting to an existing directory in which" " Django can store session data." % self.storage_path) self.file_prefix = settings.SESSION_COOKIE_NAME super(SessionStore, self).__init__(session_key) VALID_KEY_CHARS = set("abcdef0123456789") def _key_to_file(self, session_key=None): """ Get the file associated with this session key. """ if session_key is None: session_key = self._get_or_create_session_key() # Make sure we're not vulnerable to directory traversal. Session keys # should always be md5s, so they should never contain directory # components. if not set(session_key).issubset(self.VALID_KEY_CHARS): raise SuspiciousOperation( "Invalid characters in session key") return os.path.join(self.storage_path, self.file_prefix + session_key) def load(self): session_data = {} try: with open(self._key_to_file(), "rb") as session_file: file_data = session_file.read() # Don't fail if there is no data in the session file. # We may have opened the empty placeholder file. if file_data: try: session_data = self.decode(file_data) except (EOFError, SuspiciousOperation): self.create() except IOError: self.create() return session_data def create(self): while True: self._session_key = self._get_new_session_key() try: self.save(must_create=True) except CreateError: continue self.modified = True self._session_cache = {} return def save(self, must_create=False): # Get the session data now, before we start messing # with the file it is stored within. session_data = self._get_session(no_load=must_create) session_file_name = self._key_to_file() try: # Make sure the file exists. If it does not already exist, an # empty placeholder file is created. flags = os.O_WRONLY | os.O_CREAT | getattr(os, 'O_BINARY', 0) if must_create: flags |= os.O_EXCL fd = os.open(session_file_name, flags) os.close(fd) except OSError as e: if must_create and e.errno == errno.EEXIST: raise CreateError raise # Write the session file without interfering with other threads # or processes. By writing to an atomically generated temporary # file and then using the atomic os.rename() to make the complete # file visible, we avoid having to lock the session file, while # still maintaining its integrity. # # Note: Locking the session file was explored, but rejected in part # because in order to be atomic and cross-platform, it required a # long-lived lock file for each session, doubling the number of # files in the session storage directory at any given time. This # rename solution is cleaner and avoids any additional overhead # when reading the session data, which is the more common case # unless SESSION_SAVE_EVERY_REQUEST = True. # # See ticket #8616. dir, prefix = os.path.split(session_file_name) try: output_file_fd, output_file_name = tempfile.mkstemp(dir=dir, prefix=prefix + '_out_') renamed = False try: try: os.write(output_file_fd, self.encode(session_data)) finally: os.close(output_file_fd) os.rename(output_file_name, session_file_name) renamed = True finally: if not renamed: os.unlink(output_file_name) except (OSError, IOError, EOFError): pass def exists(self, session_key): return os.path.exists(self._key_to_file(session_key)) def delete(self, session_key=None): if session_key is None: if self.session_key is None: return session_key = self.session_key try: os.unlink(self._key_to_file(session_key)) except OSError: pass def clean(self): pass