auth: Disable auth caching for passwd-file

Its caching is usually unnecessary, because the passwd-files are efficiently
in memory already. It's also problematic, because extra_fields can contain
%variables, which can be lookup-dependent. So for example if %{lport} is used
in extra_fields, it would need to be included in the cache key. But because
different variables can be used by different users' extra_fields, there's
really no good way to include all of it in the cache key.

src/auth/passdb-passwd-file.c

@@ -150,14 +150,6 @@ passwd_file_preinit(pool_t pool, const char *args)
 	module->pwf = db_passwd_file_init(args, FALSE,
 					  global_auth_settings->debug);
 	module->username_format = format;
-
-	if (!module->pwf->vars)
-		module->module.default_cache_key = format;
-	else {
-		module->module.default_cache_key = auth_cache_parse_key(pool,
-			t_strconcat(format, module->pwf->path, NULL));
-	}
-
 	module->module.default_pass_scheme = scheme;
 	return &module->module;
 }

src/auth/userdb-passwd-file.c

@@ -13,8 +13,6 @@
 #include <unistd.h>
 #include <fcntl.h>
 
-#define PASSWD_FILE_CACHE_KEY "%u"
-
 struct passwd_file_userdb_iterate_context {
 	struct userdb_iterate_context ctx;
 	struct istream *input;
@@ -191,16 +189,6 @@ passwd_file_preinit(pool_t pool, const char *args)
 	module->pwf = db_passwd_file_init(args, TRUE,
 					  global_auth_settings->debug);
 	module->username_format = format;
-
-	if (!module->pwf->vars)
-		module->module.default_cache_key = PASSWD_FILE_CACHE_KEY;
-	else {
-		module->module.default_cache_key =
-			auth_cache_parse_key(pool,
-					     t_strconcat(PASSWD_FILE_CACHE_KEY,
-						         module->pwf->path,
-							 NULL));
-	}
 	return &module->module;
 }