Map logins to internal users in Auth module

This makes it possible to implement #349 as a Auth module. Another use case would be to encode usernames that contain characters unsupported by the file system.

radicale/__init__.py

@@ -167,7 +167,7 @@ class Application:
         super().__init__()
         self.configuration = configuration
         self.logger = logger
-        self.is_authenticated = auth.load(configuration, logger)
+        self.Auth = auth.load(configuration, logger)
         self.Collection = storage.load(configuration, logger)
         self.authorized = rights.load(configuration, logger)
         self.encoding = configuration.get("encoding", "request")
@@ -288,10 +288,11 @@ class Application:
         authorization = environ.get("HTTP_AUTHORIZATION", None)
         if authorization and authorization.startswith("Basic"):
             authorization = authorization[len("Basic"):].strip()
-            user, password = self.decode(base64.b64decode(
+            login, password = self.decode(base64.b64decode(
                 authorization.encode("ascii")), environ).split(":", 1)
+            user = self.Auth.map_login_to_user(login)
         else:
-            user = environ.get("REMOTE_USER")
+            user = self.Auth.map_login_to_user(environ.get("REMOTE_USER", ""))
             password = None
 
         # If "/.well-known" is not available, clients query "/"
@@ -303,7 +304,7 @@ class Application:
             self.logger.info("Refused unsafe username: %s", user)
             is_authenticated = False
         else:
-            is_authenticated = self.is_authenticated(user, password)
+            is_authenticated = self.Auth.is_authenticated(user, password)
         is_valid_user = is_authenticated or not user
 
         # Create principal collection

radicale/auth.py

@@ -65,12 +65,12 @@ def load(configuration, logger):
     auth_type = configuration.get("auth", "type")
     logger.debug("Authentication type is %s", auth_type)
     if auth_type == "None":
-        return lambda user, password: True
+        class_ = NoneAuth
     elif auth_type == "htpasswd":
-        return Auth(configuration, logger).is_authenticated
+        class_ = Auth
     else:
-        module = import_module(auth_type)
-        return module.Auth(configuration, logger).is_authenticated
+        class_ = import_module(auth_type).Auth
+    return class_(configuration, logger)
 
 
 class BaseAuth:
@@ -88,6 +88,15 @@ class BaseAuth:
         """
         raise NotImplementedError
 
+    def map_login_to_user(self, login):
+        """Map login to internal username."""
+        return login
+
+
+class NoneAuth(BaseAuth):
+    def is_authenticated(self, user, password):
+        return True
+
 
 class Auth(BaseAuth):
     def __init__(self, configuration, logger):