mailcow/data/web/inc/sessions.inc.php

<?php
// Start session
ini_set("session.cookie_httponly", 1);
if (isset($_SERVER['HTTP_X_FORWARDED_PROTO']) && 
  strtolower($_SERVER['HTTP_X_FORWARDED_PROTO']) == "https") {
  ini_set("session.cookie_secure", 1);
  $IS_HTTPS = true;
}
elseif (isset($_SERVER['HTTPS'])) {
  ini_set("session.cookie_secure", 1);
  $IS_HTTPS = true;
}
else {
  $IS_HTTPS = false;
}
session_set_cookie_params($GLOBALS['SESSION_LIFETIME'], '/', $_SERVER['SERVER_NAME'], $IS_HTTPS, true);
session_start();

// Handle logouts
if (isset($_POST["logout"])) {
  if (isset($_SESSION["dual-login"])) {
    $_SESSION["mailcow_cc_username"] = $_SESSION["dual-login"]["username"];
    $_SESSION["mailcow_cc_role"] = $_SESSION["dual-login"]["role"];
    unset($_SESSION["dual-login"]);
  }
  else {
    session_regenerate_id(true);
    session_unset();
    session_destroy();
    session_write_close();
    header("Location: /");
  }
}

// Set session IP and UA
if (!isset($_SESSION['SESS_REMOTE_IP'])) {
  $_SESSION['SESS_REMOTE_IP'] = $_SERVER['REMOTE_ADDR'];
}
if (!isset($_SESSION['SESS_REMOTE_UA'])) {
  $_SESSION['SESS_REMOTE_UA'] = $_SERVER['HTTP_USER_AGENT'];
}

// Check session
function session_check() {
  if (!isset($_SESSION['SESS_REMOTE_IP']) || !isset($_SESSION['SESS_REMOTE_UA'])) {
    return false;
  }
  if ($_SESSION['SESS_REMOTE_IP'] != $_SERVER['REMOTE_ADDR']) {
    return false;
  }
  if ($_SESSION['SESS_REMOTE_UA'] != $_SERVER['HTTP_USER_AGENT']) {
    return false;
  }
  return true;
}
if (isset($_SESSION['mailcow_cc_role']) && session_check() === false) {
  session_regenerate_id(true);
  session_unset();
  session_destroy();
  session_write_close();
  header("Location: /");
}