Create skeleton of the Lacre daemon

Also:
- Expose a function to read mail relay configuration.
- Replace tabs with 4 spaces in lacre.config.

lacre/config.py

@@ -16,72 +16,86 @@ CONFIG_PATH_ENV = "GPG_MAILGATE_CONFIG"
 # List of mandatory configuration parameters.  Each item on this list should be
 # a pair: a section name and a parameter name.
 MANDATORY_CONFIG_ITEMS = [("relay", "host"),
-						  ("relay", "port")]
+                          ("relay", "port")]
 
 # Global dict to keep configuration parameters.  It's hidden behind several
 # utility functions to make it easy to replace it with ConfigParser object in
 # the future.
 cfg = dict()
 
+
 def load_config() -> dict:
-	"""Parses configuration file.
+    """Parse configuration file.
 
-	If environment variable identified by CONFIG_PATH_ENV
-	variable is set, its value is taken as a configuration file
-	path.  Otherwise, the default is taken
-	('/etc/gpg-mailgate.conf').
-	"""
-	configFile = os.getenv(CONFIG_PATH_ENV, '/etc/gpg-mailgate.conf')
+    If environment variable identified by CONFIG_PATH_ENV
+    variable is set, its value is taken as a configuration file
+    path.  Otherwise, the default is taken
+    ('/etc/gpg-mailgate.conf').
+    """
+    configFile = os.getenv(CONFIG_PATH_ENV, '/etc/gpg-mailgate.conf')
 
-	parser = read_config(configFile)
+    parser = _read_config(configFile)
 
-	global cfg
-	cfg = copy_to_dict(parser)
-	return cfg
+    global cfg
+    cfg = _copy_to_dict(parser)
+    return cfg
 
-def read_config(fileName) -> RawConfigParser:
-	cp = RawConfigParser()
-	cp.read(fileName)
 
-	return cp
+def _read_config(fileName) -> RawConfigParser:
+    cp = RawConfigParser()
+    cp.read(fileName)
 
-def copy_to_dict(confParser) -> dict:
-	config = dict()
+    return cp
 
-	for sect in confParser.sections():
-		config[sect] = dict()
-		for (name, value) in confParser.items(sect):
-			config[sect][name] = value
 
-	return config
+def _copy_to_dict(confParser) -> dict:
+    config = dict()
+
+    for sect in confParser.sections():
+        config[sect] = dict()
+        for (name, value) in confParser.items(sect):
+            config[sect][name] = value
+
+    return config
+
+
+def get_item(section, key, empty_value=None):
+    global cfg
+    if config_item_set(section, key):
+        return cfg[section][key]
+    else:
+        return empty_value
 
-def get_item(section, key, empty_value = None):
-	global cfg
-	if config_item_set(section, key):
-		return cfg[section][key]
-	else:
-		return empty_value
 
 def has_section(section) -> bool:
-	global cfg
-	return section in cfg
+    return section in cfg
+
 
 def config_item_set(section, key) -> bool:
-	global cfg
-	return section in cfg and (key in cfg[section]) and not (cfg[section][key] is None)
+    return section in cfg and (key in cfg[section]) and not (cfg[section][key] is None)
+
 
 def config_item_equals(section, key, value) -> bool:
-	global cfg
-	return section in cfg and key in cfg[section] and cfg[section][key] == value
+    return section in cfg and key in cfg[section] and cfg[section][key] == value
+
 
 def validate_config():
-	"""Checks whether the configuration is complete.
+    """Check if configuration is complete.
 
-	Returns a list of missing parameters, so an empty list means
-	configuration is complete.
-	"""
-	missing = []
-	for (section, param) in MANDATORY_CONFIG_ITEMS:
-		if not config_item_set(section, param):
-			missing.append((section, param))
-	return missing
+    Returns a list of missing parameters, so an empty list means
+    configuration is complete.
+    """
+    missing = []
+    for (section, param) in MANDATORY_CONFIG_ITEMS:
+        if not config_item_set(section, param):
+            missing.append((section, param))
+    return missing
+
+
+#
+# High level access to configuration.
+#
+
+def relay_params():
+    """Return a (HOST, PORT) tuple identifying the mail relay."""
+    return (cfg["relay"]["host"], int(cfg["relay"]["port"]))

lacre/daemon.py

@@ -0,0 +1,34 @@
+"""Lacre Daemon, the Advanced Mail Filter message dispatcher."""
+
+from aiosmtpd.controller import Controller
+
+import lacre.config as conf
+# import lacre.mailgate as gate
+
+
+RESULT_OK = '250 OK'
+RESULT_ERROR = '500 Could not process your message'
+RESULT_NOT_IMPLEMENTED = '500 Not implemented yet'
+
+
+class MailEncryptionProxy:
+    """A mail handler dispatching to appropriate mail operation."""
+
+    async def handle_DATA(self, server, session, envelope):
+        """Accept a message and either encrypt it or forward as-is."""
+        # for now, just return an error because we're not ready to handle mail
+        return RESULT_NOT_IMPLEMENTED
+
+
+if __name__ == '__main__':
+    proxy = MailEncryptionProxy()
+    host, port = conf.relay_params()
+    controller = Controller(proxy, hostname=host, port=port)
+
+    # starts the controller in a new thread
+    controller.start()
+
+    # _this_ thread now continues operation, so it may be used to control key
+    # and certificate cache
+
+    controller.stop()

lacre/mailgate.py

@@ -378,7 +378,7 @@ def send_msg( message, recipients ):
 	recipients = [_f for _f in recipients if _f]
 	if recipients:
 		LOG.info(f"Sending email to: {recipients!r}")
-		relay = (conf.get_item('relay', 'host'), int(conf.get_item('relay', 'port')))
+		relay = conf.relay_params()
 		smtp = smtplib.SMTP(relay[0], relay[1])
 		if conf.config_item_equals('relay', 'starttls', 'yes'):
 			smtp.starttls()