-

Tue, 18 Jan 2022 13:01:20 +0100

c47@hub.netzgemeinde.eu

tokudan schrieb den folgenden Beitrag Tue, 18 Jan 2022 10:42:30 +0100

#linux #cve-2021-4122
cryptsetup can be tricked to decrypt a volume. apparently published January 13th 2022, but I haven't seen that anywhere yet:
https://marc.info/?l=oss-security&m=164207624903766&w=2

show all 5 comments

Thu, 20 Jan 2022 12:04:10 +0100

Harald Eilertsen

harald@hub.volse.no

it seems an attacker needs access to an already-opened device to perform the first step

No, they just have to modify the metadata in the luks2 header part of the volume. Since that part is (was) not protected by the keys they can do that even on a cold device.

The actual decryption happens when a valid user opens the device, so that's why repeated physical access is required.

Thu, 20 Jan 2022 12:20:27 +0100

Felix Tiede

felix@pod.pc-tiede.de

Well... provided I have repeated physical access to a device, I install a key-logger. Or some other low-level spying device and not fiddle with cryptsetup itself.

However, my more serious concern is the fact that "just updating" cryptsetup is actually not enough to secure the system, because an attacker can use any version she desires. So, how do I mitigate the attack when an attacker can choose the version of cryptsetup to perform any of the necessary steps?

Thu, 20 Jan 2022 13:59:25 +0100

Harald Eilertsen

harald@hub.volse.no

@Felix Tiede Of course, there's more than one way to get in.

The attacker would have to permanently downgrade the cryptsetup tool used during bootstrapping, but that's probably doable. If you have a fully encrypted system that may be harder, depending on how the bootstrapping works.