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import hashlib
import os
from lockfile import LockFile
from lockfile.mkdirlockfile import MkdirLockFile
from ..cache import BaseCache
from ..controller import CacheController
def _secure_open_write(filename, fmode):
# We only want to write to this file, so open it in write only mode
flags = os.O_WRONLY
# os.O_CREAT | os.O_EXCL will fail if the file already exists, so we only
# will open *new* files.
# We specify this because we want to ensure that the mode we pass is the
# mode of the file.
flags |= os.O_CREAT | os.O_EXCL
# Do not follow symlinks to prevent someone from making a symlink that
# we follow and insecurely open a cache file.
if hasattr(os, "O_NOFOLLOW"):
flags |= os.O_NOFOLLOW
# On Windows we'll mark this file as binary
if hasattr(os, "O_BINARY"):
flags |= os.O_BINARY
# Before we open our file, we want to delete any existing file that is
# there
try:
os.remove(filename)
except (IOError, OSError):
# The file must not exist already, so we can just skip ahead to opening
pass
# Open our file, the use of os.O_CREAT | os.O_EXCL will ensure that if a
# race condition happens between the os.remove and this line, that an
# error will be raised. Because we utilize a lockfile this should only
# happen if someone is attempting to attack us.
fd = os.open(filename, flags, fmode)
try:
return os.fdopen(fd, "wb")
except:
# An error occurred wrapping our FD in a file object
os.close(fd)
raise
class FileCache(BaseCache):
def __init__(self, directory, forever=False, filemode=0o0600,
dirmode=0o0700, use_dir_lock=None, lock_class=None):
if use_dir_lock is not None and lock_class is not None:
raise ValueError("Cannot use use_dir_lock and lock_class together")
if use_dir_lock:
lock_class = MkdirLockFile
if lock_class is None:
lock_class = LockFile
self.directory = directory
self.forever = forever
self.filemode = filemode
self.dirmode = dirmode
self.lock_class = lock_class
@staticmethod
def encode(x):
return hashlib.sha224(x.encode()).hexdigest()
def _fn(self, name):
# NOTE: This method should not change as some may depend on it.
# See: https://github.com/ionrock/cachecontrol/issues/63
hashed = self.encode(name)
parts = list(hashed[:5]) + [hashed]
return os.path.join(self.directory, *parts)
def get(self, key):
name = self._fn(key)
if not os.path.exists(name):
return None
with open(name, 'rb') as fh:
return fh.read()
def set(self, key, value):
name = self._fn(key)
# Make sure the directory exists
try:
os.makedirs(os.path.dirname(name), self.dirmode)
except (IOError, OSError):
pass
with self.lock_class(name) as lock:
# Write our actual file
with _secure_open_write(lock.path, self.filemode) as fh:
fh.write(value)
def delete(self, key):
name = self._fn(key)
if not self.forever:
os.remove(name)
def url_to_file_path(url, filecache):
"""Return the file cache path based on the URL.
This does not ensure the file exists!
"""
key = CacheController.cache_url(url)
return filecache._fn(key)
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