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Message-ID: <20b24b9ca0a64afb9389722845738ec8@AcuMS.aculab.com>
Date: Thu, 7 May 2020 08:05:04 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Mickaël Salaün' <mic@...ikod.net>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: Aleksa Sarai <cyphar@...har.com>, Alexei Starovoitov <ast@...nel.org>, "Al
Viro" <viro@...iv.linux.org.uk>, Andy Lutomirski <luto@...nel.org>,
"Christian Heimes" <christian@...hon.org>, Daniel Borkmann
<daniel@...earbox.net>, "Deven Bowers" <deven.desai@...ux.microsoft.com>,
Eric Chiang <ericchiang@...gle.com>, Florian Weimer <fweimer@...hat.com>,
James Morris <jmorris@...ei.org>, Jan Kara <jack@...e.cz>, Jann Horn
<jannh@...gle.com>, Jonathan Corbet <corbet@....net>, Kees Cook
<keescook@...omium.org>, "Lakshmi Ramasubramanian"
<nramas@...ux.microsoft.com>, Matthew Garrett <mjg59@...gle.com>, Matthew
Wilcox <willy@...radead.org>, Michael Kerrisk <mtk.manpages@...il.com>,
Mickaël Salaün <mickael.salaun@....gouv.fr>, Mimi Zohar
<zohar@...ux.ibm.com>, Philippe Trébuchet
<philippe.trebuchet@....gouv.fr>, Scott Shell <scottsh@...rosoft.com>, Sean
Christopherson <sean.j.christopherson@...el.com>, Shuah Khan
<shuah@...nel.org>, Steve Dower <steve.dower@...hon.org>, Steve Grubb
<sgrubb@...hat.com>, Thibaut Sautereau <thibaut.sautereau@....gouv.fr>,
Vincent Strubel <vincent.strubel@....gouv.fr>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
"linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
"linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
"linux-security-module@...r.kernel.org"
<linux-security-module@...r.kernel.org>, "linux-fsdevel@...r.kernel.org"
<linux-fsdevel@...r.kernel.org>
Subject: RE: [PATCH v5 0/6] Add support for O_MAYEXEC
From: Mickaël Salaün
> Sent: 05 May 2020 16:32
>
> This fifth patch series add new kernel configurations (OMAYEXEC_STATIC,
> OMAYEXEC_ENFORCE_MOUNT, and OMAYEXEC_ENFORCE_FILE) to enable to
> configure the security policy at kernel build time. As requested by
> Mimi Zohar, I completed the series with one of her patches for IMA.
>
> The goal of this patch series is to enable to control script execution
> with interpreters help. A new O_MAYEXEC flag, usable through
> openat2(2), is added to enable userspace script interpreter to delegate
> to the kernel (and thus the system security policy) the permission to
> interpret/execute scripts or other files containing what can be seen as
> commands.
>
> A simple system-wide security policy can be enforced by the system
> administrator through a sysctl configuration consistent with the mount
> points or the file access rights. The documentation patch explains the
> prerequisites.
>
> Furthermore, the security policy can also be delegated to an LSM, either
> a MAC system or an integrity system. For instance, the new kernel
> MAY_OPENEXEC flag closes a major IMA measurement/appraisal interpreter
> integrity gap by bringing the ability to check the use of scripts [1].
> Other uses are expected, such as for openat2(2) [2], SGX integration
> [3], bpffs [4] or IPE [5].
>
> Userspace needs to adapt to take advantage of this new feature. For
> example, the PEP 578 [6] (Runtime Audit Hooks) enables Python 3.8 to be
> extended with policy enforcement points related to code interpretation,
> which can be used to align with the PowerShell audit features.
> Additional Python security improvements (e.g. a limited interpreter
> withou -c, stdin piping of code) are on their way.
>
> The initial idea come from CLIP OS 4 and the original implementation has
> been used for more than 12 years:
> https://github.com/clipos-archive/clipos4_doc
>
> An introduction to O_MAYEXEC was given at the Linux Security Summit
> Europe 2018 - Linux Kernel Security Contributions by ANSSI:
> https://www.youtube.com/watch?v=chNjCRtPKQY&t=17m15s
> The "write xor execute" principle was explained at Kernel Recipes 2018 -
> CLIP OS: a defense-in-depth OS:
> https://www.youtube.com/watch?v=PjRE0uBtkHU&t=11m14s
>
> This patch series can be applied on top of v5.7-rc4. This can be tested
> with CONFIG_SYSCTL. I would really appreciate constructive comments on
> this patch series.
None of that description actually says what the patch actually does.
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
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