ATTACK VECTORS: EXPLOITING THE VULNERABILITY
Since Kr00k (encryption with an all-zero TK) manifests itself following a disassociation, an adversary can exploit this by manually triggering disassociations – as opposed to the disassociations that occur naturally.
This is possible, because a disassociation can be triggered by a management data frame that’s unauthenticated and unencrypted. There are possibly even other methods or events that can cause a disassociation (e.g. transmitting malcrafted packets, EAPOLs, etc.) – and/or to trigger Kr00k.
Unauthorized reading - decryption of data
As explained in the previous section, after a disassociation occurs, data from the chip’s Tx buffer will be transmitted encrypted with the all-zero TK. These data frames can be captured by an adversary and subsequently decrypted. This data can contain several kilobytes of potentially sensitive information.
My understanding is that even if the data is captured, it still needs to be decrypted. Correct?
AFFECTED DEVICES (client)
The vulnerability primarily affects FullMAC WLAN chips manufactured by
Broadcom and Cypress. These chip manufacturers have a high market share – it is safe to say that Broadcom chips are used by the majority of today’s Wi-Fi capable devices. Cypress chips are widely used in IoT devices.
The client devices that we positively tested in our lab to be vulnerable to Kr00k include:
• Amazon Echo 2nd gen
• Amazon Kindle 8th gen
• Apple iPad mini 2
• Apple iPhone 6, 6S, 8, XR
• Apple MacBook Air Retina 13-inch 2018
• Google Nexus 5
• Google Nexus 6
• Google Nexus 6S
• Raspberry Pi 3
• Samsung Galaxy S4 GT-I9505
• Samsung Galaxy S8
• Xiaomi Redmi 3S
We estimate that the number of affected devices, prior to patching, was well over a billion as the billion mark is passed by counting only the number of affected iPhone generations we tested.
We have also tested some devices with Wi-Fi chips from other manufacturers, including Qualcomm, Realtek, Ralink, Mediatek and did not see the vulnerability manifest itself. Obviously, we have not tested every possible Wi-Fi chip by every manufacturer, so while we are currently not aware of other affected chips, we also cannot rule this out.
Vulnerable access points
Of great concern is that not only client devices but also Wi-Fi access points and routers are affected by Kr00k.
This results in scenarios where client devices that are unaffected (either patched or using different Wi-Fi chips not vulnerable to Kr00k) can be connected to an access point (often times beyond an individual’s control) that is vulnerable. The attack surface is greatly increased, since an adversary can decrypt data that was transmitted by a vulnerable access point to a specific client (which may or may not be vulnerable itself).
In our lab, we were able to confirm that some wireless routers by ASUS and Huawei were vulnerable in this way.
Specifically, we positively tested:
• Asus RT-N12
• Huawei B612S-25d
• Huawei EchoLife HG8245H
• Huawei E5577Cs-321
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Seems more related to client devices?