Digitally Signed Binaries w/ Kernel support, etc.

[Roland Smith]

On Fri, Apr 04, 2008 at 10:58:40AM +0200, Ivan Voras wrote:
> >> Signing binaries could be naturally tied in with securelevel, where some
> >> securelevel (1?) would mean kernel no longer accepts new keys.
> > 
> > If you set the system immutable flag on the binaries, you cannot modify them at
> > all at securelevel >0. Signing the binaries would be pointless in that case.
> 
> I think these are separate things. Modifying binaries is separate from
> introducing new binaries. SCHG would prevent the former, but not the latter.

If you set the SCHG flag on the directories in $PATH, you can't put
anything new there as well.

> Of course, with the popularity of various scripting languages it's not
> as useful as it could be on the first thought.

If an intruder want to do real damage with a script, he pretty much has to be
root. In which case you're already fscked. Or the script must contain a
viable local root exploit, which amounts to the same thing.

As usual, there is a balance between security and usability. Where that
balance lies depends on the situation.

Roland
-- 
R.F.Smith                                   http://www.xs4all.nl/~rsmith/
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