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Users are urged to continue using WPA2 pending the availability of a fix, experts have said, as a security researcher goes public with more information about a serious flaw in the security protocol.

Key Reinstallation Attacks work against all modern protected Wi-Fi networks. Depending on the network configuration, it is also possible to inject and manipulate data as well as eavesdropping on communications. The only main limitation is that an attacker needs to be within range of a victim to exploit these weaknesses.

Android, Linux, Apple, Windows, OpenBSD, MediaTek, Linksys, and others, are all affected by some variant of the attacks. Mathy Vanhoef of KU Leuven, the Belgian security researcher who discovered the flaw, warns that the security problem stems from a fundamental cryptographic weakness in the latest generation of wireless networking rather than a software security bug. Simply changing Wi-Fi network passwords is not going to help.

The weaknesses are in the Wi-Fi standard itself, and not in individual products or implementations. Therefore, any correct implementation of WPA2 is likely affected. To prevent the attack, users must update affected products as soon as security updates become available.

The key reinstallation attack (KRACK) targets the 4-way handshake of the WPA2 protocol and relies on tricking an intended mark into reinstalling an already-in-use key. This sleight of hand is achieved by manipulating and replaying cryptographic handshake messages.

“When the victim reinstalls the key, associated parameters such as the incremental transmit packet number (i.e. nonce) and receive packet number (i.e. replay counter) are reset to their initial value,” Vanhoef explains on a microsite about the attack. “Essentially, to guarantee security, a key should only be installed and used once. Unfortunately, we found this is not guaranteed by the WPA2 protocol. By manipulating cryptographic handshakes, we can abuse this weakness in practice.”

An attacker can force these nonce resets by collecting and replaying retransmissions of message three of the 4-way handshake.

A nonce is a number that is not necessarily a secret but is meant only to be used once and never repeated. A flaw in WPA2 allows a nonce to be (or forced to be) repeated, thus allowing an attacker to extract the WPA2 session key and compromise all traffic for that session.

As a proof-of-concept, Vanhoef has published a demonstration of how a key reinstallation attack might be carried out against an Android smartphone. The attack includes the but is not limited to recovering login credentials (ie, email addresses and passwords). In general, any data or information that the victim transmits can be decrypted.

Users are urged to continue using WPA2 pending the availability of a fix. VPN and other security technologies can offer protection to connections pending the availability of software update, according to preliminary analysis by one security researcher.

Arnold KL Yau told El Reg: “This sounds bad. However, a significant amount of the risk would be mitigated for services that use strong encryption at the transport or application layer (such as TLS, HTTPS, SSH, PGP) as well as applications secured by encrypted VPN protocols.

“Despite this, however, the ability to decrypt Wi-Fi traffic could still reveal unique device identifiers (MAC addresses) and massive amounts of metadata (websites visited, traffic timing, patterns, amount of data exchanged etc.) which may well violate the privacy of the users on the network and provide valuable intelligence to whoever’s sitting in the black van.”

Research behind the attack will be presented at the Computer and Communications Security (CCS) conference in November, and at the Black Hat Europe conference in December. a research paper research paper entitled Key Reinstallation Attacks: Forcing Nonce Reuse in WPA2 (pdf here). Frank Piessens of imec-DistriNet, who supervised his research, is credited as joint author of the paper.

Previous research by Vanhoef in related areas of HTTPS and Wi-Fi security can be found here and here.

Resolving the security problem is likely to involve applying security update to routers, something history shows is a problematic process.

Mark James, security specialist at ESET: “One of the biggest concerns here of course is getting routers patched – firstly getting the average user to check and apply any firmware updates and secondly, some older routers may not even have a patch available – the average household would acquire an auto-configured router, install it and forget about it, until possibly they change their internet provider. Here, they may go through the same procedure; too many people never check or implement router updates as it’s something often too complicated for the home user to be involved in.”

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Article source: http://go.theregister.com/feed/www.theregister.co.uk/2017/10/16/wpa2_krack_attack_security_wifi_wireless/