Add cache validity configuration parameter

Also, log basic information in KeyCache and provide load() and reload()
operations to make daemon's code cleaner.

gpg-mailgate.conf.sample

@@ -51,6 +51,14 @@ dec_regex = None
 # i.e. have mode 700.
 keyhome = /var/gpgmailgate/.gnupg
 
+# Number of minutes between key cache refreshes.
+#
+# Lacre daemon keeps a cache of known keys to reduce number of OS processes
+# needed to perform a single email.  Keyring is going to be modified during
+# daemon's lifetime, so with this simple mechanism we ensure that new keys
+# will eventually be recognised and loaded.
+cache_refresh_minutes = 5
+
 [smime]
 # the directory for the S/MIME certificate files
 cert_path = /var/gpgmailgate/smime

lacre/daemon.py

@@ -75,8 +75,8 @@ async def _sleep():
 def _main():
     _validate_config()
 
-    keys = kcache.KeyCache()
-    keys.load_keyring(conf.get_item('gpg', 'keyhome'))
+    keys = kcache.KeyCache(conf.get_item('gpg', 'keyhome'))
+    keys.load()
     controller = _init_controller(keys)
 
     LOG.info("Starting the daemon...")

lacre/keycache.py

@@ -1,9 +1,12 @@
 """A cache of OpenPGP keys known to Lacre."""
 
 import lacre.text as text
+import logging
 
 import GnuPG
 
+LOG = logging.getLogger(__name__)
+
 
 class KeyCache:
     """A store for OpenPGP keys.
@@ -13,15 +16,21 @@ class KeyCache:
     [default].
     """
 
-    def __init__(self):
-        """Initialise an empty cache."""
+    def __init__(self, keyring_dir: str = None):
+        """Initialise an empty cache.
+
+        With keyring_dir given, set location of the directory from which keys should be loaded.
+        """
         self._keys = dict()
+        self._keyring_dir = keyring_dir
 
-    def __getitem__(self, email):
-        return self._keys[email]
+    def __getitem__(self, fingerpring):
+        """Look up email assigned to the given fingerprint."""
+        return self._keys[fingerpring]
 
-    def __setitem__(self, email, fingerprint):
-        self._keys[email] = fingerprint
+    def __setitem__(self, fingerprint, email):
+        """Assign an email to a fingerpring, overwriting it if it was already present."""
+        self._keys[fingerprint] = email
 
     def __contains__(self, fingerprint):
         """Check if the given fingerprint is assigned to an email."""
@@ -30,17 +39,28 @@ class KeyCache:
         return fingerprint in self._keys
 
     def has_email(self, email):
+        """Check if cache contains a key assigned to the given email."""
         return email in self._keys.values()
 
+    def load(self):
+        """Load keyring, replacing any previous contents of the cache."""
+        self.replace_keyring(self._load_keyring_from(self._keyring_dir))
+
+    reload = load
+
     def load_keyring(self, keyhome: str):
         """Add all identities from keyring stored in KEYHOME."""
-        self.extend_keyring(GnuPG.public_keys(keyhome))
+        self.extend_keyring(self._load_keyring_from(keyhome))
+
+    def _load_keyring_from(self, keyring_dir):
+        return GnuPG.public_keys(keyring_dir)
 
     def replace_keyring(self, keys: dict):
         """Overwrite previously stored key cache with KEYS."""
         for fingerprint in keys:
             keys[fingerprint] = text.sanitize_case_sense(keys[fingerprint])
 
+        LOG.info(f'Loaded {len(keys)} keys')
         self._keys = keys
 
     def extend_keyring(self, keys: dict):
@@ -48,4 +68,5 @@ class KeyCache:
         for fingerprint in keys:
             keys[fingerprint] = text.sanitize_case_sense(keys[fingerprint])
 
+        LOG.info(f'Loaded {len(keys)} keys')
         self._keys.update(keys)

test/gpg-mailgate-daemon-test.conf

@@ -6,6 +6,7 @@ date_format = ISO
 
 [gpg]
 keyhome = test/keyhome
+cache_refresh_minutes = 1
 
 [smime]
 cert_path = test/certs