A new security research outfit called ReVuln has presented its letter of introduction to the world in the form of a paper that analyses how the Steam protocol can expose gamers to attacks.
In this document (PDF), the company analyses what happens when a URL using the protocol
steam:// is redirected. Of the major browsers, Internet Explorer and Chrome present warnings (Chrome being the most detailed, describing the program the redirect is trying to call); Opera presents a warning but only shows the first 40 characters of the URL being called; Firefox requests a confirmation but doesn't show the URL; and Safari will directly execute the program without warnings.
RealPlayer is also vulnerable to external calls using crafted URLs, write the company's Luigi Auriemma and Donato Ferrante.
Steam's custom browser executes software to an external URL call without warnings. However, they note, it's limited to Valve-owned domains (like steampowered.com).
One proof-of-concept demonstrated in the paper is the use of the Steam reinstall feature, an undocumented feature for installing backups from a local directory. This has a splash image processor which, the paper says, has an integer overflow vulnerability that "may allow executing malicious code on the Steam process."
Other undocumented features in Steam include command-line parameters in the Source engine (used by games such as Half-Life and CounterStrike), callable from a URL and also vulnerable; and integer overflow vulnerabilities in the Unreal engine.
These and other vulnerabilities are detailed in the video below:
Users can disable the
steam:// protocol in their browser, but a complete fix will depend on Valve, the researchers state. ®