Warning Over Widespread Web Authentication Vulnerabilities

Warnings have been issued about serious vulnerabilities in security protocols OAuth 2.0 and OpenID, affecting a range of top web services, including Facebook, Google, LinkedIn and Microsoft.

The weaknesses could be abused to carry out what’s known as “covert redirect”, where a website does inadequate checks of partner sites when redirecting users to them.

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OAuth and OpenID are designed to allow quick access to third-party sites, using tokens from an authorisation server, such as those provided by Facebook and Google.

The standards let people use logins from Facebook, Google and other popular services to access other sites. Additionally, OAuth and OpenID mean that when users click on a link taking them from one service to another, their authentication and login are quickly checked to allow speedy access.

But problems in certain pieces of OAuth and OpenID code mean a malicious hacker could tinker with pieces of a third-party’s URL and then trick a user into clicking on it.

That could either hand over the sensitive data used in authentication, or be abused to send a victim to a malicious website

The problem stems from the fact that OAuth and OpenID fail to check the URLs properly, said Wang Jing, a PhD student at the Nanyang Technological University in Singapore, in a blog post.

“For OAuth 2.0, these attacks might jeopardise the token of the site users, which could be used to access user information. In the case of Facebook, the information could include the basic ones, such as email address, age, locale, work history,” said Wang.

“For OpenID, the attackers may get user’s information directly. Compounded by the large number of companies involved, this vulnerability could lead to huge consequences if left unresolved.”

Wang claimed to have found the vulnerabilities in February, before reporting them to affected parties. A solution would be to implement a whitelist, where third parties have to register if they want users to be able to interact with their APIs.

That’s something LinkedIn has already introduced. According to Wang, Facebook said it had protections in place, but said a full whitelist might not be feasible.

He was told by Google it was investigating the issue, whilst Microsoft said it had identified a problem in a third-party site, telling Wang to notify the owner of that website. Yahoo did not respond to Wang’s notifications, he said.

The warning comes hot on the heels of Heartbleed, a vulnerability in OpenSSL, another standard designed to guarantee security on the Internet.

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