82 lines
2.4 KiB
Python
82 lines
2.4 KiB
Python
import hashlib
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import os
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from lockfile import FileLock
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def _secure_open_write(filename, fmode):
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# We only want to write to this file, so open it in write only mode
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flags = os.O_WRONLY
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# os.O_CREAT | os.O_EXCL will fail if the file already exists, so we only
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# will open *new* files.
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# We specify this because we want to ensure that the mode we pass is the
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# mode of the file.
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flags |= os.O_CREAT | os.O_EXCL
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# Do not follow symlinks to prevent someone from making a symlink that
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# we follow and insecurely open a cache file.
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if hasattr(os, "O_NOFOLLOW"):
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flags |= os.O_NOFOLLOW
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# On Windows we'll mark this file as binary
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if hasattr(os, "O_BINARY"):
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flags |= os.O_BINARY
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# Before we open our file, we want to delete any existing file that is
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# there
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try:
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os.remove(filename)
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except (IOError, OSError):
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# The file must not exist already, so we can just skip ahead to opening
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pass
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# Open our file, the use of os.O_CREAT | os.O_EXCL will ensure that if a
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# race condition happens between the os.remove and this line, that an
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# error will be raised. Because we utilize a lockfile this should only
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# happen if someone is attempting to attack us.
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fd = os.open(filename, flags, fmode)
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try:
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return os.fdopen(fd, "wb")
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except:
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# An error occurred wrapping our FD in a file object
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os.close(fd)
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raise
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class FileCache(object):
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def __init__(self, directory, forever=False, filemode=0o0600,
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dirmode=0o0700):
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self.directory = directory
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self.forever = forever
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self.filemode = filemode
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if not os.path.isdir(self.directory):
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os.makedirs(self.directory, dirmode)
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@staticmethod
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def encode(x):
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return hashlib.sha224(x.encode()).hexdigest()
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def _fn(self, name):
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return os.path.join(self.directory, self.encode(name))
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def get(self, key):
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name = self._fn(key)
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if not os.path.exists(name):
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return None
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with open(name, 'rb') as fh:
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return fh.read()
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def set(self, key, value):
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name = self._fn(key)
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with FileLock(name) as lock:
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with _secure_open_write(lock.path, self.filemode) as fh:
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fh.write(value)
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def delete(self, key):
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name = self._fn(key)
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if not self.forever:
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os.remove(name)
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