linux-kernel - Re: Linux capabilities shouldn't be lost during setuid to non-root from root or to another non-root uid from a non-root uid.

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Message-ID: <20110419143548.GA26461@hallyn.com>
Date:	Tue, 19 Apr 2011 09:35:48 -0500
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	crocket <crockabiscuit@...il.com>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Andrew Morgan <morgan@...nel.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Linux capabilities shouldn't be lost during setuid to non-root
 from root or to another non-root uid from a non-root uid.

Quoting crocket (crockabiscuit@...il.com):
> Thanks for the precious information.
> 
> I think capsh should be introduced somewhere in some manuals.

Would mentioning capsh in capabilities(7) be a good idea?

> On Tue, Apr 19, 2011 at 10:14 AM, crocket <crockabiscuit@...il.com> wrote:
> > Is there an existing utility that sets SECBIT_NO_SETUID_FIXUP?
> > Or is there a way to set it without writing a C wrapper program?
> >
> > On Tue, Apr 19, 2011 at 7:02 AM, Serge E. Hallyn <serge@...lyn.com> wrote:
> >> Quoting crocket (crockabiscuit@...il.com):
> >>> I have several questions.
> >>>
> >>> 1) How do I set SECBIT_NO_SETUID_FIXUP?
> >>
> >> prctl(PR_SET_SECUREBITS, SECBIT_NO_SETUID_FIXUP | SECBIT_NO_SETUID_FIXUP_LOCKED)
> >>
> >> see capabilities(7) for details.
> >>
> >>> 2) Is there any reason to unset SECBIT_NO_SETUID_FIXUP by default?
> >>
> >> Yes, because it's what userspace expects.  If you prefer to run in
> >> a full POSIX capabilities environment with unprivileged root, you
> >> can have init set SECBIT_NO_SETUID_FIXUP and SECBIT_NOROOT and
> >> tune userspace to do the right thing, but it's not trivial.
> >>
> >> -serge
> >>
> >
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