Add plugin to debug login cookie issues

login-debug.php

+<?php
+/*
+* Plugin Name: A/I - Debug login issues
+* Plugin URI:
+* Description: Debug login issues
+* Version: 0.0.1
+* Author: Autistici/Inventati
+* Author URI: https://autistici.org
+**/
+
+function debug_login_auth_cookie_malformed($cookie, $scheme) {
+    error_log("LOGIN: auth_cookie_malformed: scheme={$scheme} cookie={$cookie}");
+}
+add_action('auth_cookie_malformed', 'debug_login_auth_cookie_malformed', 10, 2);
+
+function debug_login_auth_cookie_expired($cookie_elements) {
+    $username = $cookie_elements['username'];
+    error_log("LOGIN: auth_cookie_expired: username={$username}");
+}
+add_action('auth_cookie_expired', 'debug_login_auth_cookie_expired');
+
+function debug_login_auth_cookie_bad_username($cookie_elements) {
+    $username = $cookie_elements['username'];
+    error_log("LOGIN: auth_cookie_bad_username: username={$username}");
+}
+add_action('auth_cookie_bad_username', 'debug_login_auth_cookie_bad_username');
+
+function debug_login_auth_cookie_bad_hash($cookie_elements) {
+    $username = $cookie_elements['username'];
+    $token = $cookie_elements['token'];
+    error_log("LOGIN: auth_cookie_bad_hash: username={$username} token={$token}");
+}
+add_action('auth_cookie_bad_hash', 'debug_login_auth_cookie_bad_hash');
+
+function debug_login_auth_cookie_bad_session_token($cookie_elements) {
+    $username = $cookie_elements['username'];
+    $token = $cookie_elements['token'];
+    error_log("LOGIN: auth_cookie_bad_session_token: username={$username} token={$token}");
+}
+add_action('auth_cookie_bad_session_token', 'debug_login_auth_cookie_bad_session_token');