linux-kernel - Re: [PATCH v6 3/5] seccomp: add a way to get a listener fd from ptrace

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Date:   Wed, 17 Oct 2018 11:31:55 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Michael Tirado <mtirado418@...il.com>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Tycho Andersen <tycho@...ho.ws>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 3/5] seccomp: add a way to get a listener fd from ptrace

On Wed, Oct 17, 2018 at 12:25 AM, Michael Tirado <mtirado418@...il.com> wrote:
> On Thu, Sep 13, 2018 at 12:02 AM Andy Lutomirski <luto@...capital.net> wrote:
>>
>> Or we could have a
>> seccomp() mode that adds a filter but only kicks in after execve().
>>
>> --Andy
>
> Hey that's a pretty good idea, then we could block execve in a seccomp
> launcher without post-exec cooperation, or that patch I wrote that used
> an execve counter which probably should have been through prctl instead.

This has come up a few times before, actually. I had a working
prototype, but it needed some more shaking-out. I do like the idea of
"activate later" filters, though I'd always felt like using execve as
the boundary was a bit limiting. I wonder if we could do some kind of
external trigger (i.e. the fd passed to the caller) for when to
activate... likely the synchronization is a horror show, though, so if
execve is "good enough", I'll probably be happy with that. :)

-Kees

-- 
Kees Cook
Pixel Security