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: <20240718.yieCh6miu9en@digikod.net>
Date: Thu, 18 Jul 2024 17:35:36 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: James Bottomley <James.Bottomley@...senpartnership.com>
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 Dower <steve.dower@...hon.org>, 
	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, Elliott Hughes <enh@...gle.com>
Subject: Re: [RFC PATCH v19 1/5] exec: Add a new AT_CHECK flag to execveat(2)

On Thu, Jul 18, 2024 at 09:03:36AM -0400, James Bottomley wrote:
> On Thu, 2024-07-18 at 14:24 +0200, Mickaël Salaün wrote:
> > On Wed, Jul 17, 2024 at 07:08:17PM -0700, Jeff Xu wrote:
> > > On Wed, Jul 17, 2024 at 3:01 AM Mickaël Salaün <mic@...ikod.net>
> > > wrote:
> > > > On Tue, Jul 16, 2024 at 11:33:55PM -0700, Jeff Xu wrote:
> [...]
> > > > > I'm still thinking  execveat(AT_CHECK) vs faccessat(AT_CHECK)
> > > > > in different use cases:
> > > > > 
> > > > > execveat clearly has less code change, but that also means: we
> > > > > can't add logic specific to exec (i.e. logic that can't be
> > > > > applied to config) for this part (from do_execveat_common to
> > > > > security_bprm_creds_for_exec) in future.  This would require
> > > > > some agreement/sign-off, I'm not sure from whom.
> > > > 
> > > > I'm not sure to follow. We could still add new flags, but for now
> > > > I don't see use cases.  This patch series is not meant to handle
> > > > all possible "trust checks", only executable code, which makes
> > > > sense for the kernel.
> > > > 
> > > I guess the "configfile" discussion is where I get confused, at one
> > > point, I think this would become a generic "trust checks" api for
> > > everything related to "generating executable code", e.g.
> > > javascript, java code, and more. We will want to clearly define the
> > > scope of execveat(AT_CHECK)
> > 
> > The line between data and code is blurry.  For instance, a
> > configuration file can impact the execution flow of a program.  So,
> > where to draw the line?
> 
> Having a way to have config files part of the trusted envelope, either
> by signing or measurement would be really useful.  The current standard
> distro IMA deployment is signed executables, but not signed config
> because it's hard to construct a policy that doesn't force the signing
> of too many extraneous files (and files which might change often).
> 
> > It might makes sense to follow the kernel and interpreter semantic:
> > if a file can be executed by the kernel (e.g. ELF binary, file
> > containing a shebang, or just configured with binfmt_misc), then this
> > should be considered as executable code.  This applies to Bash,
> > Python, Javascript, NodeJS, PE, PHP...  However, we can also make a
> > picture executable with binfmt_misc.  So, again, where to draw the
> > line?
> 
> Possibly by making open for config an indication executables can give?
> I'm not advocating doing it in this patch, but if we had an open for
> config indication, the LSMs could do much finer grained policy,
> especially if they knew which executable was trying to open the config
> file.  It would allow things like an IMA policy saying if a signed
> executable is opening a config file, then that file must also be
> signed.

Checking configuration could be a next step, but not with this patch
series.  FYI, the previous version was a (too) generic syscall:
https://lore.kernel.org/all/20220104155024.48023-1-mic@digikod.net/
One of the main concern was alignment with kernel semantic.  For now,
let's focus on script execution control.

> 
> James
> 

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ