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Date: Wed, 14 Feb 2024 16:43:36 +0100
From: Yves-Alexis Perez <corsac@...ian.org>
To: Mate Kukri <mate.kukri@...onical.com>
Cc: oss-security@...ts.openwall.com
Subject: Re: Secure Boot bypass in EDK2 based Virtual Machine
firmware
On Wed, Feb 14, 2024 at 02:40:43PM +0000, Mate Kukri wrote:
> Hello,
>
> We have identified a vulnerability resulting from an insecure default
> configuration of OVMF/AAVMF
> and similar firmware as used in Ubuntu's edk2 package, the firmware
> used by LXD, and potentially other similar software.
>
> Said EDK2 based firmwares implement UEFI Secure Boot functionality but
> also contain a copy of the UEFI Shell,
> this gives an OS resident attacker (without physical access or
> pseudo-physical access) the ability to execute arbitrary
> code at system level, and thus the ability bypass UEFI Secure Boot.
Hi Mate,
I'm not sure if I understand everything correctly, but if UEFI Secure
Boot is enabled, shouldn't the shell.efi binary need to be explicitely
signed in order for it to be correctly loaded? It doesnt look like a
good idea to sign shell.efi on a production platform, but for test
purposes it might be relevant.
Regards,
--
Yves-Alexis Perez
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