Re: Bugs in sysctl.c

thospel@mail.dma.be
11 Aug 1997 16:34:24 -0000


> Securelevel is not completely implemented yet.
>
> You should write a little document with what different levels do, and
> post this to linux-kernel. You'll get some feedback, and then
> implementing it will be a matter of a few hours intense hacking.
>
>
> The document should do something like:
>
>
> 0: Default. Normal "unix-like" operation.
> 1: chattr is disallowed
> 2: ....
>
> only increasing the securelevel is allowed. Decreasing the
> securelevel requires a reboot.
>
> Things like "access to raw devices", "access to kmem", "access to /proc",
> "modifying IP parameters", etc etc should be mentioned.

Ah, so that's how securelevel will be done.

Might it not be even more interesting to make securelevel a directory with
each file corresponding to a certain ability, in each of which you could
only increase the level ? That way the several abilities would be more
orthogonal.

(of course, your script that sets up securelevels should warn if unexpectedly
files got added when booting a newer kernel. These files probably default to
very permissive, and might be enough to fight securelevel (e.g. an ability
to load modules allows you to write a module that hunts down secure level
variables in core and change them there.))
Ton
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