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The presentation by researchers Jager and Somorovsky concerning the proof-of-concept attack for XML encryption showed it’s possible to decrypt XML-encrypted data without knowing the encryption key. Jager and Somorovsky’s research is a generalization of Padding Oracle attacks from Vaudenay in 2002. Enterprises should be relatively unconcerned about this development, but as the BEAST attacks demonstrated, theoretical or proof-of-concept exploits should be taken seriously by software vendors. As soon as fixes are released, software vendors using XML encryption should start fixing their software and in-house developers should be prepared to update their code.
Enterprises could temporarily protect XML-encrypted data by implementing rate-limiting for XML encryption connections, ensuring security tools detect the attacks, applying general access control for XML encryptions connections, and potentially instigating an XML firewall. Rate-limiting connections for XML encryption does not stop an attack, but it slows the attack because a large number of connections are required to obtain the necessary encrypted data to analyze and decrypt. By slowing the attack, an organization has a better chance of detecting an attack in progress. The organization should check if its network and host-based security tools identify the XML encryption requests to determine if the error messages generated from the attack are detected. General access control for XML connections limits the sources of an attack by restricting connections to only approved network sources. There are also XML firewalls that include some of this functionality that could be used to block an attack.
This was first published in May 2012