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

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Date:   Thu, 13 Dec 2018 10:40:32 +1100 (AEDT)
From:   James Morris <jmorris@...ei.org>
To:     Florian Weimer <fweimer@...hat.com>
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

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.


-- 
James Morris
<jmorris@...ei.org>