Re: [PATCH] capabilities: Ambient capability set V1

[Serge E. Hallyn]

On Mon, Feb 23, 2015 at 10:44:32AM -0600, Christoph Lameter wrote:
> On Mon, 23 Feb 2015, Serge Hallyn wrote:
> 
> > The core concern for amorgan is that an unprivileged user not be
> > able to cause a privileged program to run in a way that it fails to
> > drop privilege before running unprivileged-user-provided code.
> 
> I do not see a problem with dropping privilege since the ambient set
> is supposed to be preserved across a drop of priviledge.

Because you're tricking the program into thinking it has dropped
the privilege, when in fact it has not.

> > Since your desire is precisely for a mode where dropping privilege
> > works as usual, but exec then re-gains some or all of that privilege,
> 
> I would say that the ambient set stays active even if the setuid binary
> drops to regular perms.
> 
> > we need to either agree on a way to enter that mode that ordinary
> > use caes can't be tricked into using, or find a way for legacy
> > users to be tpiped off as to what's going on (without having to be
> > re-written)
> 
> Well if the ambient set is completely separate then the existing
> semantics are preserved while the ambient set stays active as intended.
> 
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