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New WiFi Setup Flaw Allows Easy Router PIN Guessing

Posted by Soulskill on from the orders-of-magnitude dept.

Trailrunner7 writes "There is a newly discovered vulnerability in the WiFi Protected Setup standard that reduces the number of attempts it would take an attacker to brute-force the PIN for a wireless router's setup process. The flaw results in too much information about the PIN being returned to an attacker and makes the PIN quite weak, affecting the security of millions of WiFi routers and access points. Security researcher Stefan Viehbock discovered the vulnerability (PDF) and reported it to US-CERT. The problem affects a number of vendors' products, including D-Link, Netgear, Linksys and Buffalo. 'I noticed a few really bad design decisions which enable an efficient brute force attack, thus effectively breaking the security of pretty much all WPS-enabled Wi-Fi routers. As all of the of the more recent router models come with WPS enabled by default, this affects millions of devices worldwide,' Viehbock said."

5 of 86 comments (clear)

  1. Re:WPS by Anonymous Coward · · Score: 2, Informative

    There's push button mode, and there's a shared PIN mode.

  2. Nothing new by ewanm89 · · Score: 3, Informative

    Same old thing, default configuration is bad.

    1. Re:Nothing new by swillden · · Score: 3, Informative

      Same old thing, default configuration is bad.

      Not really. That would imply that changing the default configuration to something else would fix the problem, but it doesn't. The only thing that fixes it is disabling WPS. Well, I suppose setting a really long PIN -- but the default is 8 digits which most people would expect is reasonable anyway. If the protocol didn't leak information about the PIN, or the device didn't allow brute force searches, this wouldn't be a problem.

      This isn't a default configuration problem, this is a security protocol defect coupled with an implementation error.

      --
      Note to ACs: I usually delete AC replies without reading them. If you want to talk to me, log in.
  3. Re:ok... by stevel · · Score: 5, Informative

    No. If your router supports the "external" authentication mode using only a PIN, it is vulnerable no matter which encryption type you use or how good your password is. I did not realize that there was such a mode - I too thought it required the pushbutton.

    The easiest mitigation is to disable the WPS PIN on your router, re-enabling it when you want to add a device. Some routers may not have such an option, but at least mine does.

    Scary.

  4. Simple mistake, simple correction by romiz · · Score: 3, Informative

    From the PDF, the implementation mistake is to give the attacker feedback on whether the tried key is correct after the first half of authentication (phase M4), and then after the complete authentication (phase M6). Since the PIN is only 8 digits, and the last one is a checksum, the problem is reduced to guessing 1 number in 10000, and then 1 in 1000.

    The document states that there are few possible mitigations for the problem. However, it skips the obvious one: do not notify authentication success/failure until the response to the M6 message. This would restore the 1 in 10,000,000 guessing complexity of the PIN code, without changing the protocol. It should even be a new issue tested by the compliance suite the vendors need to pass to get the WPS certification.