linux-kernel - Re: [PATCH 03/27] Enforce module signatures if the kernel is locked down

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]

Date:   Thu, 02 Nov 2017 22:01:07 +0000
From:   David Howells <dhowells@...hat.com>
To:     Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:     dhowells@...hat.com, linux-security-module@...r.kernel.org,
        gnomes@...rguk.ukuu.org.uk, linux-efi@...r.kernel.org,
        matthew.garrett@...ula.com, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, jforbes@...hat.com
Subject: Re: [PATCH 03/27] Enforce module signatures if the kernel is locked down

Mimi Zohar <zohar@...ux.vnet.ibm.com> wrote:

> Right, it would never get here if the IMA signature verification
> fails.  If sig_enforce is not enabled, then it will also work.  So the
> only case is if sig_enforced is enabled and there is no key.
> 
> eg.
>          else if (can_do_ima_check && is_ima_appraise_enabled())
>                 err = 0;

I'm not sure where you want to put that, but I can't just do this:

	/* Not having a signature is only an error if we're strict. */
	if (err == -ENOKEY && !sig_enforce &&
	    (!can_do_ima_check || !is_ima_appraise_enabled()) &&
	    !kernel_is_locked_down("Loading of unsigned modules"))
		err = 0;
	else if (can_do_ima_check && is_ima_appraise_enabled())
		err = 0;

because that'll print out a message in lockdown mode saying that you're not
allowed to do that and then maybe do it anyway.

David