Re: [KERNEL] Re: [KERNEL] Re: [KERNEL] Re: [KERNEL] Re: Kernel 4.3 breaks security in systems using capabilities

[Klaus Ethgen <Klaus+lkml@ethgen.de>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

Am Do den  5. Nov 2015 um 18:34 schrieb Serge E. Hallyn:
> > Am Do den  5. Nov 2015 um 17:15 schrieb Serge E. Hallyn:
> > > I think if you follow your idea to its logical conclusions, you end
> > > up wanting set SECURE_ALL_BITS | SECURE_ALL_LOCKS, which will include
> > > SECURE_NO_CAP_AMBIENT_RAISE, disabling ambient capabilities.
> > 
> > That I did miss out and seems to be the solution for the problem. So
> > adding cap_secure_all_bits,cap_secure_all_locks=ep to every binary that
> > gets other caps should solve it?
> 
> No that doesn't work, you have to use prctl to set those bits.  If you
> can get your system to be fully rootless, you can have init or initramfs
> do this for you.  It'll mean that root and setuid-root binaries have no
> automatic privileges beside owning host (proc/sys) files.

So this is not helping much. But for me it is at least an idea to how to
have abient capabilities _and_ full control for admin. It would be an
un-capability but at least would allow the admin to change the
behaviour.

Another one, that would be much better would be something like
cap_ambient_cap capability to explicitly allow the use of ambient
capabilities.

I have to say that I do not know much about prctl. Just reading the man
page currently. But this seems to be about the second way of taking away
rights from UID 0 instead of explicitly giving rights to selective
binaries.

Regards
   Klaus
- -- 
Klaus Ethgen                              http://www.ethgen.ch/
pub  4096R/4E20AF1C 2011-05-16   Klaus Ethgen <Klaus@Ethgen.de>
Fingerprint: 85D4 CA42 952C 949B 1753  62B3 79D0 B06F 4E20 AF1C
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
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=T9bn
-----END PGP SIGNATURE-----