HTTPS Vulnerable To Crypto Attack

The secure sockets layer (SSL) and transport layer security (TLS) encryption protocol, used by millions of websites to secure Web communications via HTTPS, is vulnerable to being decrypted by attackers.

In particular, security researchers Juliano Rizzo and Thai Duong have built a tool that's capable of decrypting and obtaining the authentication tokens and cookies used in many websites' HTTPS requests. "Our exploit abuses a vulnerability present in the SSL/TLS implementation of major Web browsers at the time of writing," they said.

The duo plan to detail their findings, which they characterize as a "fast block-wise chosen-plaintext attack against SSL/TLS," on Friday at the Ekoparty Security Conference in Argentina. They said websites using SSL version 3 and TLS version 1.0 and earlier are vulnerable. Although newer versions of TLS are available--and apparently not vulnerable to this attack--most sites still use TLS 1.0.

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To illustrate the vulnerability they've discovered and automatically harvest authentication tokens and cookies, the researchers said they've also built a JavaScript-based tool dubbed BEAST, for Browser Exploit Against SSL/TLS. "It is worth noting that the vulnerability that BEAST exploits has been [present] since the very first version of SSL. Most people in the crypto and security community have concluded that it is non-exploitable, that's why it has been largely ignored for many years," Duong told Threatpost.

The researchers plan use BEAST during their Ekoparty presentation to decrypt PayPal authentication cookies and access a PayPal account, according to the Register.

While full details of the vulnerability haven't been publicly disclosed, browser developers don't appear to be running scared. "The researchers disclosed BEAST to browsers so I'm not going to comment in detail until public," said Google Chrome engineer Adam Langley in a Twitter post. "It's neat, but not something to worry about." Opera, however, has already released a related patch, and the researchers said they expect other browser makers to follow suit.

The HTTPS vulnerability is likely to accelerate calls for an overhaul of today's fragile SSL ecosystem. Such calls have intensified after the July 2011 exploit--not revealed publicly until last month--of Dutch certificate authority DigiNotar. As a result of that exploit, attackers were able to issue false credentials for hundreds of legitimate websites, including Gmail and Windows Update.

Interestingly, Rizzo and Duong are no strangers to vulnerability research. Rizzo is one of the founders and designers behind open source network security tool platform Netifera, while Duong is chief security officer for a large Vietnamese bank, and has led Black Hat workshops detailing practical attacks against cryptography.

Last year, notably, the pair detailed a previously unknown "padding oracle attack" (referring not to Oracle, but rather a cryptographic concept) against ASP.NET Web applications that could be used to "decrypt cookies, view states, form authentication tickets, membership password, user data, and anything else encrypted using the framework's API," they said. Exploiting the vulnerability, present in 25% of ASP Web applications, could allow attackers to access information or even compromise systems.

The vulnerability stemmed from how Microsoft implemented AES in ASP.NET. Notably, if an attacker altered the encrypted data contained in a cookie, ASP.NET returned semi-detailed error messages. After amassing enough of these, an attacker could make an educated guess about the encryption key being used.

That vulnerability disclosure led Microsoft to issue an emergency patch.

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