linux-kernel - Re: [PATCH V31 07/25] kexec_file: Restrict at runtime 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]

Message-Id: <1561411657.4340.70.camel@linux.ibm.com>
Date:   Mon, 24 Jun 2019 17:27:37 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Matthew Garrett <mjg59@...gle.com>, Dave Young <dyoung@...hat.com>
Cc:     James Morris <jmorris@...ei.org>, Jiri Bohac <jbohac@...e.cz>,
        Linux API <linux-api@...r.kernel.org>,
        kexec@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Howells <dhowells@...hat.com>,
        LSM List <linux-security-module@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH V31 07/25] kexec_file: Restrict at runtime if the kernel
 is locked down

Hi Matthew,

On Mon, 2019-06-24 at 14:06 -0700, Matthew Garrett wrote:
> On Sun, Jun 23, 2019 at 6:52 PM Dave Young <dyoung@...hat.com> wrote:
> >
> > On 06/21/19 at 01:18pm, Matthew Garrett wrote:
> > > I don't think so - we want it to be possible to load images if they
> > > have a valid signature.
> >
> > I know it works like this way because of the previous patch.  But from
> > the patch log "When KEXEC_SIG is not enabled, kernel should not load
> > images", it is simple to check it early for !IS_ENABLED(CONFIG_KEXEC_SIG) &&
> > kernel_is_locked_down(reason, LOCKDOWN_INTEGRITY)  instead of depending
> > on the late code to verify signature.  In that way, easier to
> > understand the logic, no?
> 
> But that combination doesn't enforce signature validation? We can't
> depend on !IS_ENABLED(CONFIG_KEXEC_SIG_FORCE) because then it'll
> enforce signature validation even if lockdown is disabled.

I agree with Dave.  There should be a stub lockdown function to
prevent enforcing lockdown when it isn't enabled.

Mimi