'Secure' Wi-Fi Standard Has Serious Security Flaws

'Secure' Wi-Fi Standard Has Serious Security Flaws

Researchers from the University of Leuven in Belgium have discovered a series of serious wi-fi security flaws that essentially eliminate wi-fi privacy.

These series of wi-fi vulnerabilities collectively dubbed as “Krack”, short for key reinstallation attacks, can access data that was previously presumed to be safely encrypted. Krack attackers can steal wi-fi passwords, chat messages, emails, photos and other sensitive information. It’s also possible, depending on device use and the network configuration, for Krack attackers to inject malicious software like ransomware into websites.

The University of Leuven researchers, in their paper entitled “Key Reinstallation Attacks: Forcing Nonce Reuse in WPA2” (PDF) said that “every Wi-Fi device is vulnerable” to Krack attacks.

"The weaknesses are in the Wi-Fi standard itself, and not in individual products or implementations,” lead researcher Mathy Vanhoef said.

Wi-Fi Alliance, a non-profit organization that promotes wi-fi technology and certifies wi-fi products, said, “Recently published research identified vulnerabilities in some Wi-Fi devices where those devices reinstall network encryption keys under certain conditions, disabling replay protection and significantly reducing the security of encryption.”

 

For its part, the International Consortium for Advancement of Cybersecurity on the Internet (ICASI), in a statement said, “Depending on the specific device configuration, successful exploitation of these vulnerabilities could allow unauthenticated attackers to perform packet replay, decrypt wireless packets, and to potentially forge or inject packets into a wireless network.”

ICASI members include Amazon, Cisco Systems, IBM, Intel Corporation, Juniper Networks, Microsoft Corporation and Oracle Corporation.

How Krack Works

For Krack to work, the attacker must be within the range of a victim. As proof-of-concept, lead researcher Vanhoef executed Krack attacks against wi-fi devices. Vanhoef was able to show that Krack not just steals login credentials – including email addresses and passwords – but all data that the victim transmits or sends was decrypted.

It’s also doable for Krack attackers, depending on the network setup and the device being used, to decrypt, not just data sent over wi-fi but also data sent towards the victim, for instance, the content of a website.

“Although websites or apps may use HTTPS as an additional layer of protection, we warn that this extra protection can (still) be bypassed in a worrying number of situations,” Vanhoef said. “For example, HTTPS was previously bypassed in non-browser software, in Apple's iOS and OS X, in Android apps, in Android apps again, in banking apps, and even in VPN apps.”

Krack is able to decrypt not just data sent over wi-fi but also data sent towards the victim by exploiting the vulnerabilities in the 4-way handshake of the Wi-Fi Protected Access 2 (WPA2) protocol.

The 4-way handshake is a 14-year-old technology that supposedly ensures wi-fi privacy by installing a fresh and unique encryption key that’ll be used to encrypt all subsequent traffic every time a device joins a protected wi-fi network.

Instead of installing a fresh and unique encryption key, Krack tricks the device into reinstalling an already-in-use encryption key. This is done by manipulating and replaying handshake messages. The researchers also found that Krack similarly exploits other wi-fi handshakes, including PeerKey handshake, the group key handshake and the Fast BSS Transition (FT) handshake.

As mentioned, Krack is a series of wi-fi vulnerabilities. This means that not just one wi-fi vulnerability is exploited by Krack. The Common Vulnerabilities and Exposures (CVE) – a dictionary of common names for publicly known cyber security vulnerabilities – list the following specific vulnerabilities related to Krack:

• CVE-2017-13077: Reinstallation of the pairwise encryption key (PTK-TK) in the 4-way handshake.
• CVE-2017-13078: Reinstallation of the group key (GTK) in the 4-way handshake.
• CVE-2017-13079: Reinstallation of the integrity group key (IGTK) in the 4-way handshake.
• CVE-2017-13080: Reinstallation of the group key (GTK) in the group key handshake.
• CVE-2017-13081: Reinstallation of the integrity group key (IGTK) in the group key handshake.
• CVE-2017-13082: Accepting a retransmitted Fast BSS Transition (FT) Reassociation Request and reinstalling the pairwise encryption key (PTK-TK) while processing it.
• CVE-2017-13084: Reinstallation of the STK key in the PeerKey handshake.
• CVE-2017-13086: Reinstallation of the Tunneled Direct-Link Setup (TDLS) PeerKey (TPK) key in the TDLS handshake.
• CVE-2017-13087: Reinstallation of the group key (GTK) when processing a Wireless Network Management (WNM) Sleep Mode Response frame.
• CVE-2017-13088: Reinstallation of the integrity group key (IGTK) when processing a Wireless Network Management (WNM) Sleep Mode Response frame.

According to Wi-Fi Alliance, there’s no evidence that Krack has been exploited maliciously in the wild.

How to Prevent Krack Attacks

To prevent Krack attacks, make sure to update your wi-fi device as soon as patch or security update becomes available. A security update ensures that an encryption key is only installed once, preventing Krack attacks.

Password change of your wi-fi network won’t stop Krack attacks. The only remedy is to apply the patch or security update of your wi-fi device as soon as it becomes available. It’s also important to update your router’s firmware. While it’s important to patch or apply the latest security updates of your wi-fi and router, it also pays to change the wi-fi password as a precaution.

According to Vanhoef, they notified wi-fi manufacturers about the Krack issue on July 14, 2017. They also notified the Computer Emergency Response Team Coordination Center (CERT/CC) – the world’s first computer emergency response team for internet security incidents. CERT/CC, in turn, issued a broad notification to wi-fi manufacturers on August 28, 2017 about this issue.

“We have released a security update to address this issue,” Microsoft spokesperson told The Verge. “Customers who apply the update, or have automatic updates enabled, will be protected. We continue to encourage customers to turn on automatic updates to help ensure they are protected.”

Windows updates released last October 10, according to Microsoft, addressed this issue. The company said it “withheld disclosure until other vendors could develop and release updates”.

“Wi-Fi Alliance now requires testing for this vulnerability within our global certification lab network and has provided a vulnerability detection tool for use by any Wi-Fi Alliance member,” the alliance said. “Wi-Fi Alliance is also broadly communicating details on this vulnerability and remedies to device vendors and encouraging them to work with their solution providers to rapidly integrate any necessary patches.”