linux-kernel - Re: [RFC PATCH v1 0/5] Add support for O

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Date:   Thu, 13 Dec 2018 06:13:39 +0100
From:   Florian Weimer <fweimer@...hat.com>
To:     James Morris <jmorris@...ei.org>
Cc:     Mickaël Salaün <mic@...ikod.net>,
        linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Matthew Garrett <mjg59@...gle.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Mickaël Salaün <mickael.salaun@....gouv.fr>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Philippe Trébuchet 
        <philippe.trebuchet@....gouv.fr>, Shuah Khan <shuah@...nel.org>,
        Thibaut Sautereau <thibaut.sautereau@....gouv.fr>,
        Vincent Strubel <vincent.strubel@....gouv.fr>,
        Yves-Alexis Perez <yves-alexis.perez@....gouv.fr>,
        kernel-hardening@...ts.openwall.com, linux-api@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [RFC PATCH v1 0/5] Add support for O_MAYEXEC

* James Morris:

> On Wed, 12 Dec 2018, Florian Weimer wrote:
>
>> * James Morris:
>> 
>> > If you're depending on the script interpreter to flag that the user may 
>> > execute code, this seems to be equivalent in security terms to depending 
>> > on the user.  e.g. what if the user uses ptrace and clears O_MAYEXEC?
>> 
>> The argument I've heard is this: Using ptrace (and adding the +x
>> attribute) are auditable events.
>
> I guess you could also preload a modified libc which strips the flag.

My understanding is that this new libc would have to come somewhere, and
making it executable would be an auditable even as well.

Thanks,
Florian