linux-kernel - RE: [PATCH v5 0/6] Add support for O

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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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