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: <BANLkTikJqgwGixtgXKOY-2e=1sAQYUtbcQ@mail.gmail.com>
Date:	Tue, 19 Apr 2011 10:14:57 +0900
From:	crocket <crockabiscuit@...il.com>
To:	"Serge E. Hallyn" <serge@...lyn.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.

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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