linux-kernel - Re: [PATCH] kexec: Do not verify the signature without the lockdown or mandatory signature

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200526135935.ffkfulsjf7xrep63@dwarf.suse.cz>
Date:   Tue, 26 May 2020 15:59:35 +0200
From:   Jiri Bohac <jbohac@...e.cz>
To:     Lianbo Jiang <lijiang@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
        ebiederm@...ssion.com, jmorris@...ei.org, mjg59@...gle.com,
        dyoung@...hat.com, bhe@...hat.com
Subject: Re: [PATCH] kexec: Do not verify the signature without the lockdown
 or mandatory signature

On Mon, May 25, 2020 at 01:23:51PM +0800, Lianbo Jiang wrote:
> So, here, let's simplify the logic to improve code readability. If the
> KEXEC_SIG_FORCE enabled or kexec lockdown enabled, signature verification
> is mandated. Otherwise, we lift the bar for any kernel image.

I agree completely; in fact that was my intention when
introducing the code, but I got overruled about the return codes:
https://lore.kernel.org/lkml/20180119125425.l72meyyc2qtrriwe@dwarf.suse.cz/

I like this simplification very much, except this part:

> +	if (ret) {
> +		pr_debug("kernel signature verification failed (%d).\n", ret);

...

> -		pr_notice("kernel signature verification failed (%d).\n", ret);

I think the log level should stay at most PR_NOTICE when the
verification failure results in rejecting the kernel. Perhaps
even lower.

In case verification is not enforced and the failure is
ignored, KERN_DEBUG seems reasonable.

Regards,

-- 
Jiri Bohac <jbohac@...e.cz>
SUSE Labs, Prague, Czechia