On 07/05/2020 10:05, David Laight wrote: > 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. "Add support for O_MAYEXEC" "to enable to control script execution". What is not clear here? This seems well understood by other commenters. The documentation patch and the talks can also help.
