153 lines
4.7 KiB
Python
153 lines
4.7 KiB
Python
"""Data structures and utilities to make keyring access easier.
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IMPORTANT: This module has to be loaded _after_ initialisation of the logging
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module.
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"""
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import lacre.text as text
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import lacre.config as conf
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import logging
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from os import stat
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from watchdog.events import FileSystemEventHandler
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from asyncio import Semaphore, run
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import copy
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import GnuPG
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LOG = logging.getLogger(__name__)
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def _sanitize(keys):
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sanitize = text.choose_sanitizer(conf.get_item('default', 'mail_case_insensitive'))
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return {fingerprint: sanitize(keys[fingerprint]) for fingerprint in keys}
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class KeyCacheMisconfiguration(Exception):
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"""Exception used to signal that KeyCache is misconfigured."""
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class KeyCache:
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"""A store for OpenPGP keys.
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Key case is sanitised while loading from GnuPG if so
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configured. See mail_case_insensitive parameter in section
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[default].
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"""
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def __init__(self, keys: dict = None):
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"""Initialise an empty cache.
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With keyring_dir given, set location of the directory from which keys should be loaded.
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"""
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self._keys = keys
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def __getitem__(self, fingerpring):
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"""Look up email assigned to the given fingerprint."""
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return self._keys[fingerpring]
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def __setitem__(self, fingerprint, email):
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"""Assign an email to a fingerpring, overwriting it if it was already present."""
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self._keys[fingerprint] = email
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def __contains__(self, fingerprint):
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"""Check if the given fingerprint is assigned to an email."""
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# This method has to be present for KeyCache to be a dict substitute.
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# See mailgate, function _identify_gpg_recipients.
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return fingerprint in self._keys
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def has_email(self, email):
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"""Check if cache contains a key assigned to the given email."""
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return email in self._keys.values()
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def __repr__(self):
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"""Return text representation of this object."""
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details = ' '.join(self._keys.keys())
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return f'<KeyCache {details}>'
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class KeyRing:
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"""A high-level adapter for GnuPG-maintained keyring directory.
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Its role is to keep a cache of keys present in the keyring,
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reload it when necessary and produce static copies of
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fingerprint=>email maps.
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"""
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def __init__(self, path: str):
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"""Initialise the adapter."""
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self._path = path
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self._keys = self._load_and_sanitize()
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self._sema = Semaphore()
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self._last_mod = None
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def _load_and_sanitize(self):
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keys = self._load_keyring_from(self._path)
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return _sanitize(keys)
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def _load_keyring_from(self, keyring_dir):
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return GnuPG.public_keys(keyring_dir)
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async def freeze_identities(self) -> KeyCache:
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"""Return a static, async-safe copy of the identity map."""
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async with self._sema:
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keys = copy.deepcopy(self._keys)
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return KeyCache(keys)
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def load(self):
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"""Load keyring, replacing any previous contents of the cache."""
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LOG.debug('Reloading keys...')
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run(self._load())
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async def _load(self):
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last_mod = self._read_mod_time()
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if self._is_modified(last_mod):
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async with self._sema:
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self.replace_keyring(self._load_keyring_from(self._path))
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self._last_mod = self._read_mod_time()
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reload = load
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def replace_keyring(self, keys: dict):
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"""Overwrite previously stored key cache with KEYS."""
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keys = _sanitize(keys)
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LOG.info(f'Storing {len(keys)} keys')
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self._keys = keys
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def _read_mod_time(self):
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# (mode, ino, dev, nlink, uid, gid, size, atime, mtime, ctime)
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# 0 1 2 3 4 5 6 7 8 9
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MTIME = 8
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st = stat(self._path)
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return st[MTIME]
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def _is_modified(self, last_mod):
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if self._last_mod is None:
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LOG.debug('Keyring not loaded before')
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return True
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elif self._last_mod != last_mod:
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LOG.debug('Keyring directory mtime changed')
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return True
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else:
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LOG.debug('Keyring not modified ')
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return False
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class KeyringModificationListener(FileSystemEventHandler):
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"""A filesystem event listener that triggers key cache reload."""
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def __init__(self, keyring: KeyRing):
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"""Initialise a listener with a callback to be executed upon each change."""
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self._keyring = keyring
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def handle(self, event):
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"""Reload keys upon FS event."""
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LOG.debug(f'Reloading on event {event!r}')
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self._keyring.reload()
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# All methods should do the same: reload the key cache.
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# on_created = handle
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# on_deleted = handle
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on_modified = handle
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