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: <BANLkTimMGm=Qd-exvKmwJdh4pGRscRTHVw@mail.gmail.com>
Date:	Thu, 21 Apr 2011 08:51:40 +0900
From:	crocket <crockabiscuit@...il.com>
To:	unlisted-recipients:; (no To-header on input)
Cc:	Michael Kerrisk <mtk.manpages@...il.com>,
	Andrew Morgan <morgan@...nel.org>, 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.

On Tue, Apr 19, 2011 at 11:35 PM, Serge E. Hallyn <serge@...lyn.com> wrote:
> Quoting crocket (crockabiscuit@...il.com):
>> Thanks for the precious information.
>>
>> I think capsh should be introduced somewhere in some manuals.


     Yes I think mentioning capsh in capabilities(7) would be a good idea.


>
> 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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