Le 12/12/2018 à 17:29, Jordan Glover a écrit :

On Wednesday, December 12, 2018 9:17 AM, Mickaël Salaün [off-list ref] wrote:

quoted

Hi,

The goal of this patch series is to control script interpretation. A
new O_MAYEXEC flag used by sys_open() is added to enable userland script
interpreter to delegate to the kernel (and thus the system security
policy) the permission to interpret scripts or other files containing
what can be seen as commands.

The security policy is the responsibility of an LSM. A basic
system-wide policy is implemented with Yama and configurable through a
sysctl.

The initial idea come from CLIP OS and the original implementation has
been used for more than 10 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 v4.20-rc6. This can be
tested with CONFIG_SECURITY_YAMA. I would really appreciate
constructive comments on this RFC.

Regards,

Are various interpreters upstreams interested in adding support
for O_MAYEXEC if it land in kernel? Did you contacted them about this?

I think the first step is to be OK on the kernel side. We will then be
able to help upstream interpreters implement this feature. It should be
OK because the behavior doesn't change by default, i.e. if the sysadmin
doesn't configure (and test) the whole system. Some examples of modified
interpreters can be found at
https://github.com/clipos-archive/clipos4_portage-overlay/search?q=O_MAYEXEC
.

 Mickaël