GMS-2020-602: Link injection in SimpleSAMLphp

Background

Several scripts part of SimpleSAMLphp display a web page with links obtained from the request parameters. This allows us to enhance usability, as the users are presented with links they can follow after completing a certain action, like logging out.

Description

The following scripts were not checking the URLs obtained via the HTTP request before displaying them as the target of links that the user may click on:

• www/logout.php
• modules/core/www/no_cookie.php

The issue allowed attackers to display links targeting a malicious website inside a trusted site running SimpleSAMLphp, due to the lack of security checks involving the link_href and retryURL HTTP parameters, respectively. The issue was resolved by including a verification of the URLs received in the request against a white list of websites specified in the trusted.url.domains configuration option.

Affected versions

All SimpleSAMLphp versions prior to 1.14.4.

Impact

A remote attacker could craft a link pointing to a trusted website running SimpleSAMLphp, including a parameter pointing to a malicious website, and try to fool the victim into visiting that website by clicking on a link in the page presented by SimpleSAMLphp.

Resolution

Upgrade to the latest version.

Credit

This security issue was discovered and reported by John Page (hyp3rlinx).