stratum: show reason of auth failure

util.cpp

@@ -1354,7 +1354,11 @@ bool stratum_authorize(struct stratum_ctx *sctx, const char *user, const char *p
 
 	if (!res_val || json_is_false(res_val) ||
 	    (err_val && !json_is_null(err_val)))  {
-		applog(LOG_ERR, "Stratum authentication failed");
+		if (err_val && json_is_array(err_val)) {
+			const char* reason = json_string_value(json_array_get(err_val, 1));
+			applog(LOG_ERR, "Stratum authentication failed (%s)", reason);
+		}
+		else applog(LOG_ERR, "Stratum authentication failed");
 		goto out;
 	}