Oh Great, WPA2 Is Broken

WPA2, the standard security for Wi-Fi networks these days, has been cracked due to a flaw in the protocol. Implications stemming from this crack range from decrypting Wi-Fi, hijacking connections, and injecting content. It’s fair to say, WPA2 is now Considered Harmful. The paper is available here (PDF).

This is a proof-of-concept exploit, and like all headline-making network security stories, it has a name. It’s called KRACK, for Key Reinstallation Attack. The key insight to this exploit is a vulnerability in the handshaking between routers and devices to establish a secure connection.

This is not the first time the researchers behind this exploit have found holes in WPA2. In a paper published by the KRACK researchers at the USENIX Symposium last August (PDF), they showed that the Random Number Generator used in 802.11 is flawed, ill-defined, and insecure. The researchers have also spoken at 33c3 on predicting WPA2 Group Keys.

The practical consequences of a poor definition and implementation of an RNG can be found in consumer hardware. The researchers found that in MediaTek-based routers, the only source of randomness is the current time. Meanwhile Broadcom-based routers do not use the RNG proposed by the 802.11 spec, but instead take the MD5 of the current time in microseconds. The researchers do not mention if the current time is a secret.

So what do we do now?

This has happened before. In 2001, WEP, the Wi-Fi security protocol many security-ignorant people are still running, was cracked in much the same was as KRACK. This quickly led to the development of Aircrack, and in 2003, the Wi-Fi Alliance rolled out WPA and WPA2. Sure, you can still select a deprecated security protocol for your router, but the problem of WEP hacking is as solved as it’s ever going to be.

The early 2000s were a different time when it came to wireless networks, though here in 2017 Wi-Fi permeates every cubic inch of our lives. Everything and everyone has Wi-Fi now. This is going to be a bit bigger than cracking WEP, but it remains possible to patch devices to ensure that this exploit is rendered useless. Install those security updates, people! Of course there will still be millions of unpatched devices in a year’s time, and for those routers, IoT baubles, and other wireless devices, turning on WPA2 will be akin to having no security at all.

That said, this isn’t a world-ending Armageddon in the way the botnet of webcams was. You will only be vulnerable if an attacker is within range of your router, and you will still be secure if you’re accessing secure websites. However, turning off Wi-Fi on your phone, relying on mobile data, not ignoring HTTPS cert warnings, and plugging into an Ethernet port might not be a bad idea.

A chink in the armor of WPA/WPA2 WiFi security

Looks like your WiFi might not be quite as secure as you thought it was. A paper recently published by [Stefan Viehböck] details a security flaw in the supposedly robust WPA/WPA2 WiFi security protocol. It’s not actually that protocol which is the culprit, but an in-built feature called Wi-Fi Protected Setup. This is an additional security protocol that allows you to easily setup network devices like printers without the need to give them the WPA passphrase. [Stephan’s] proof-of-concept allows him to get the WPS pin in 4-10 hours using brute force. Once an attacker has that pin, they can immediately get the WPA passphrase with it. This works even if the passphrase is frequently changed.

Apparently, most WiFi access points not only offer WPS, but have it enabled by default. To further muck up the situation, some hardware settings dashboards offer a disable switch that doesn’t actually do anything!

It looks like [Stephan] wasn’t the only one working on this exploit. [Craig] wrote in to let us know he’s already released software to exploit the hole.

D-Link router captcha broken


We reported last week that D-Link was adding captchas to their routers to prevent automated login by malware. Unsurprisingly, it doesn’t work all time. The team from SourceSec grabbed the new firmware and began poking at it. They found that certain pages don’t require the authentication to be passed for access. One of these is WPS activation. WPS lets you do push button WPA configuration. Once activated, any nearby client can request the WPA key using a tool like WPSpy. Only user level credentials are needed to pull this off, so changing just the admin password won’t prevent it.

[photo: schoschie]

New WPA TKIP attack


[Martin Beck] and [Erik Tews] have just released a paper covering an improved attack against WEP and a brand new attack against WPA(PDF). For the WEP half, they offer a nice overview of attacks up to this point and the optimizations they made to reduce the number of packets needed to approximately 25K. The only serious threat to WPA so far has been the coWPAtty dictionary attack. This new attack lets you decrypt the last 12 bytes of a WPA packet’s plaintext and then generate arbitrary packets to send to the client. While it doesn’t recover the WPA key, the attacker is still able to send packets directly to the machine they’re attacking and could potentially read back the response via an outbound connection to the internet.

[photo: niallkennedy]

[via SANS]