Message-ID: <54CFE3E8.2030402@schaufler-ca.com>
Date: Mon, 02 Feb 2015 12:54:00 -0800
From: Casey Schaufler <casey@schaufler-ca.com>
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To: Andy Lutomirski <luto@amacapital.net>,
        Serge Hallyn <serge.hallyn@ubuntu.com>
CC: Christoph Lameter <cl@linux.com>,
        Serge Hallyn <serge.hallyn@canonical.com>,
        Jonathan Corbet <corbet@lwn.net>, Aaron Jones <aaronmdjones@gmail.com>,
        "Ted Ts'o" <tytso@mit.edu>,
        LSM List <linux-security-module@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linuxfoundation.org>,
        Casey Schaufler <casey@schaufler-ca.com>
Subject: Re: [capabilities] Allow normal inheritance for a configurable set
 of capabilities
References: <alpine.DEB.2.11.1502021018500.5029@gentwo.org> <54CFB9B8.8020701@schaufler-ca.com> <20150202180806.GE24351@ubuntumail> <CALCETrXgodHNiEspXKbAm_xGfBtE6n4diESQzp5Rq8xyW14F2w@mail.gmail.com>
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On 2/2/2015 12:37 PM, Andy Lutomirski wrote:
> On Mon, Feb 2, 2015 at 10:08 AM, Serge Hallyn <serge.hallyn@ubuntu.com> wrote:
>> Quoting Casey Schaufler (casey@schaufler-ca.com):
>>> I'm game to participate in such an effort. The POSIX scheme
>>> is workable, but given that it's 20 years old and hasn't
>>> developed real traction it's hard to call it successful.
>> Over the years we've several times discussed possible reasons for this
>> and how to help.  I personally think it's two things:  1. lack of
>> toolchain and fs support.  The fact that we cannot to this day enable
>> ping using capabilities by default because of cpio, tar and non-xattr
>> filesystems is disheartening.  2. It's hard for users and applications
>> to know what caps they need.  yes the API is a bear to use, but we can
>> hide that behind fancier libraries.  But using capabilities requires too
>> much in-depth knowledge of precisely what caps you might need for
>> whatever operations library may now do when you asked for something.
> None of this could address the problem here, though: if I hold a
> capability and I want to pass that capability to an exec'd helper, I
> shouldn't need the fs's help to do this.

One of the holes in the 1003.1e spec is what to do with a program file
that does not have a capability set attached to it. The two options are
drop all capabilities and leave the capabilities alone. The latter gives
you what you're asking for. The former is arguably safer.


>
> --Andy
>

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