Students crack Microsoft CardSpace

May 30, 2008 – 6:04 PM

Students at the Ruhr University of Bochum, Germany, say they have found a way to steal security tokens in Microsoft’s new CardSpace authentication framework. Attackers can apparently get access to protected, encrypted user data – such as passwords, credit card numbers, and delivery addresses – when they are transmitted. CardSpace (formerly InfoCard) is the successor to Passport. In both architectures, users’ personal data are stored locally on the user’s system. Depending on the web site, users can decide which data they want to transmit. CardSpace is designed to make classic passwords a thing of the past, by replacing them with digital certificates that may be self-signed or signed by an authoritative CA such as Verisign.

According to the report, anti-DNS pinning, DNS rebinding, DNS spoofing, and drive-by pharming are apparently all successful ways to steal transmitted tokens. Attackers basically need to manipulate the user system’s name resolution so that the token for the browser-based CardSpace is sent to the attacker. To this end, attackers manipulate the DNS entries on a router, for instance by means of cross-site request forgery, and send the attacked user to a malicious name server. If the attacker manages to switch name resolution during an authentication process so that the victim lands both on a shop’s genuine CardSpace website and on a malicious forgery, the attacker then gets the token. During the token’s validity, attackers can then pretend to be the user in question when they go shopping.

The students have created a demo server that they claim demonstrates the problem. To reproduce the demonstration, you should change your own DNS settings and install an untrusted certificate. In our test at heise Security, we could not get the demonstration to run, however. Microsoft has apparently already been informed of the problem and is working on a solution. In their report, the students propose improving Same Origin Policy as a security function for browsers.

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