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Re: [libvirt] [PATCH 2/5] util: allow using virCommandAllowCap with setuid helpers



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Il 27/03/2013 23:46, Eric Blake ha scritto:
> That seems like a kernel flaw - it makes sense that you can't
> _add_ capabilities without CAP_SETPCAP, but being unable to _drop_ 
> capabilities without first acquiring a capability seems backwards.
> I wonder if lkml would accept a patch that makes CAP_SETPCAP
> unnecessary for the restriction case, and only require it for the
> case of gaining capabilities.

The worry here is that dropping _some_ caps but not all lets you
exploit untested error paths in suid binaries.

The solution could be to install libvirtd as suid-root and drop all
capabilities except CAP_SETPCAP when running unprivileged.
Alternatively, you could use file capabilities to the same effect.

Paolo
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