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: <BANLkTimELd0WhNYkaQOQuV1vnr+5jAgTZA@mail.gmail.com>
Date:	Tue, 19 Apr 2011 23:27:07 +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.

Thanks for the precious information.

I think capsh should be introduced somewhere in some manuals.

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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