Re: [PATCH v3 2/2] modules:capabilities: add a per-task modules autoload restriction

From: Andy Lutomirski
Date: Fri May 05 2017 - 12:19:17 EST

On Thu, May 4, 2017 at 6:07 AM, Djalal Harouni <tixxdz@xxxxxxxxx> wrote:
> On Sat, Apr 22, 2017 at 2:17 PM, Djalal Harouni <tixxdz@xxxxxxxxx> wrote:
>> On Sat, Apr 22, 2017 at 1:28 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
> [...]
>>> My point is that all of these need some way to handle configuration
>>> and inheritance, and I don't think that a bunch of per-task prctls is
>>> the right way. As just an example, saying that interactive users can
>>> autoload modules but other users can't, or that certain systemd
>>> services can, etc, might be nice. Linus already complained that he
>>> (i.e. user "torvalds" or whatever) should be able to profile the
>>> kernel but that other uids should not be able to.
>> Neat, maybe this could already be achieved with this interface and
>> systemd-logind, "ModulesAutoloadUsers=andy" in logind.conf where
>> "andy" is the only logged-in user able to trigger and autoload kernel
>> modules. However maybe we should not restrict too much other bits or
>> functionality of the other users, please let me will follow up later
>> on it.
>>> I personally like my implicit_rights idea, and it might be interesting
>>> to prototype it.
> Andy following on the idea of per user settings, I'm curious did you
> manage to make some advance on how to store the user settings ? the
> user database format is old and not extensible, there was cgmanager or
> other libcgroup but for resources, and no simple thing for such
> restrictions example: "RestrictLinuxModules=user" that will prevent
> such users from making/loading extra Linux features/modules that are
> not already available...

I figured that user code would figure it out somehow. Text config file?

There is another odd way it could be configured: just leave the inodes
around in /dev/rights with appropriate permissions. Some startup
script could re-instantiate them with the same permissions (via a
syscall that does that atomically).