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: <20110418220232.GA15967@hallyn.com>
Date:	Mon, 18 Apr 2011 17:02:32 -0500
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	crocket <crockabiscuit@...il.com>
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):
> 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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