Old-school, export-grade crypto standard used until the 1990s can be triggered to downgrade security of client, servers, researchers find.
Turns out the old US government restriction of exporting strong encryption that led to the shipping of weaker 512-bit crypto products overseas didn't actually disappear with the outdated policy in the late 1990s. A group of researchers from Microsoft Research, INRIA and IMDEA, has found that some SSL/TLS client and server implementations--such as OpenSSL versions 1.01k and earlier and Apple Safari--can be forced to employ the weaker cipher suite.
The weaker SSL/TLS encryption key can be easily cracked, researchers say, and used to wage man-in-the-middle attacks on the secured connections in order to sniff passwords or other sensitive information.
Some one-fourth of SSL-encrypted websites are potentially vulnerable to attacks using the so-called FREAK (Factoring RSA Export Keys) vulnerability. Affected website owners in the government and private sector are currently scrambling to correct the oversight. FBI.gov and Whitehouse.gov reportedly are among the websites that have since been remedied of the problem, and Apple is in the process of coming up with a patch for its software. OpenSSL-based browsers on Android devices also are affected by the bug.
OpenSSL actually patched the issue in January, but details of the vulnerability are just now coming to light publicly.
"It's a very interesting problem that shows how we mustn't be complacent about these older technologies, even though we think they are not going to be used," says SSL expert Ivan Ristic, who is director of engineering at Qualys. "The attack seems fairly easy, conceptually."
The researchers say it would take about 7½ hours using $104 in Amazon EC2 computing power to crack the key, he notes.
But, as Ristic points out, that's just the first step to an attack: "Then they need to find a vulnerable client," he says. "In practice, I don't think this is a terribly big issue, but only because you have to have many 'ducks in a row.'"
An attack also would require exploiting a server that includes the older cipher suite option, as well as reusing a key for a long period of time, and of course, a man-in-the middle attack via a local area network or a WiFi network, he says. "It's not so easy otherwise," from afar, he says.
The FREAK problem dates back to a time when the US government had instituted a policy of only exporting weak crypto overseas to ensure the NSA could decrypt foreign communications; sale of strong encryption technology overseas was banned.
"Support for these weak algorithms has remained in many implementations such as OpenSSL, even though they are typically disabled by default; however, we discovered that several implementations incorrectly allow the message sequence of export cipher suites to be used even if a non-export ciphersuite was negotiated," the researchers wrote. "Thus, if a server is willing to negotiate an export ciphersuite, a man-in-the-middle may trick a browser (which normally doesn't allow it) to use a weak export key. By design, export RSA moduli must be less than 512 bits long; hence, they can be factored in less than 12 hours for $50 on Amazon EC2."
The researchers say NSA's site also allows the use of the older crypto, as does the OAuth SDK server used by Facebook, IBM, and Symantec.
Cryptographer Matthew Green, a research professor at Johns Hopkins University, blogged today that there's more to this finding than the potential attack. "You might think this is all a bit absurd and doesn’t affect you very much. In a strictly technical sense you’re probably right. The client bugs have will soon be patched (update your devices! unless you have Android in which case you're screwed). With good luck, servers supporting export-grade RSA cipher suites will soon be rare curiosity," Green says.
The big takeaway here, he says, is how an old policy to weaken crypto for the intel community is haunting security today.
"The export-grade RSA ciphers are the remains of a 1980s-vintage effort to weaken cryptography so that intelligence agencies would be able to monitor. This was done badly. So badly, that while the policies were ultimately scrapped, they’re still hurting us today," Green says.