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 - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
