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Security experts are warning website operators to test whether their HTTPS traffic is vulnerable to a new crypto attack that can be used to grab sensitive information.
The so-called BREACH attack -- short for Browser Reconnaissance and Exfiltration via Adaptive Compression of Hypertext -- was detailed in a Department of Homeland Security (DHS) "BREACH vulnerability in compressed HTTPS" advisory, issued Friday, which warned that "a sophisticated attacker may be able to derive plaintext secrets from the ciphertext in an HTTPS stream." All versions of the transport layer security (TLS) and secure sockets layer (SSL) protocols are vulnerable.
Full details of the vulnerability were first unveiled Thursday at the Black Hat conference in Las Vegas by Salesforce.com lead product security engineer Angelo Prado, Square application security engineer Neal Harris, and Salesforce.com lead security engineer Yoel Gluck. Their man-in-the-middle HTTPS crypto attack involves watching "the size of the cipher text received by the browser while triggering a number of strategically crafted requests to a target site," according to exploit details provided by Prado to DHS. "To recover a particular secret in an HTTPS response body, the attacker guesses character by character, sending a pair of requests for each guess. The correct guess will result in a smaller HTTPS response," he said.
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