linux-kernel - Re: [RFC PATCH v19 1/5] exec: Add a new AT

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: <20240717.AGh2shahc9ee@digikod.net>
Date: Wed, 17 Jul 2024 12:00:49 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: Steve Dower <steve.dower@...hon.org>
Cc: Jeff Xu <jeffxu@...gle.com>, Al Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, Kees Cook <keescook@...omium.org>, 
	Linus Torvalds <torvalds@...ux-foundation.org>, Paul Moore <paul@...l-moore.com>, Theodore Ts'o <tytso@....edu>, 
	Alejandro Colomar <alx@...nel.org>, Aleksa Sarai <cyphar@...har.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Andy Lutomirski <luto@...nel.org>, Arnd Bergmann <arnd@...db.de>, 
	Casey Schaufler <casey@...aufler-ca.com>, Christian Heimes <christian@...hon.org>, 
	Dmitry Vyukov <dvyukov@...gle.com>, Eric Biggers <ebiggers@...nel.org>, 
	Eric Chiang <ericchiang@...gle.com>, Fan Wu <wufan@...ux.microsoft.com>, 
	Florian Weimer <fweimer@...hat.com>, Geert Uytterhoeven <geert@...ux-m68k.org>, 
	James Morris <jamorris@...ux.microsoft.com>, Jan Kara <jack@...e.cz>, Jann Horn <jannh@...gle.com>, 
	Jonathan Corbet <corbet@....net>, Jordan R Abrahams <ajordanr@...gle.com>, 
	Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>, Luca Boccassi <bluca@...ian.org>, 
	Luis Chamberlain <mcgrof@...nel.org>, "Madhavan T . Venkataraman" <madvenka@...ux.microsoft.com>, 
	Matt Bobrowski <mattbobrowski@...gle.com>, Matthew Garrett <mjg59@...f.ucam.org>, 
	Matthew Wilcox <willy@...radead.org>, Miklos Szeredi <mszeredi@...hat.com>, 
	Mimi Zohar <zohar@...ux.ibm.com>, Nicolas Bouchinet <nicolas.bouchinet@....gouv.fr>, 
	Scott Shell <scottsh@...rosoft.com>, Shuah Khan <shuah@...nel.org>, 
	Stephen Rothwell <sfr@...b.auug.org.au>, Steve Grubb <sgrubb@...hat.com>, 
	Thibaut Sautereau <thibaut.sautereau@....gouv.fr>, Vincent Strubel <vincent.strubel@....gouv.fr>, 
	Xiaoming Ni <nixiaoming@...wei.com>, Yin Fengwei <fengwei.yin@...el.com>, 
	kernel-hardening@...ts.openwall.com, linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-security-module@...r.kernel.org
Subject: Re: [RFC PATCH v19 1/5] exec: Add a new AT_CHECK flag to execveat(2)

On Wed, Jul 17, 2024 at 09:26:22AM +0100, Steve Dower wrote:
> On 17/07/2024 07:33, Jeff Xu wrote:
> > Consider those cases: I think:
> > a> relying purely on userspace for enforcement does't seem to be
> > effective,  e.g. it is trivial  to call open(), then mmap() it into
> > executable memory.
> 
> If there's a way to do this without running executable code that had to pass
> a previous execveat() check, then yeah, it's not effective (e.g. a Python
> interpreter that *doesn't* enforce execveat() is a trivial way to do it).
> 
> Once arbitrary code is running, all bets are off. So long as all arbitrary
> code is being checked itself, it's allowed to do things that would bypass
> later checks (and it's up to whoever audited it in the first place to
> prevent this by not giving it the special mark that allows it to pass the
> check).

Exactly.  As explained in the patches, one crucial prerequisite is that
the executable code is trusted, and the system must provide integrity
guarantees.  We cannot do anything without that.  This patches series is
a building block to fix a blind spot on Linux systems to be able to
fully control executability.