Message-ID: <54CFC942.9010502@schaufler-ca.com>
Date: Mon, 02 Feb 2015 11:00:18 -0800
From: Casey Schaufler <casey@schaufler-ca.com>
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To: Serge Hallyn <serge.hallyn@ubuntu.com>
CC: Christoph Lameter <cl@linux.com>,
        Serge Hallyn <serge.hallyn@canonical.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Jonathan Corbet <corbet@lwn.net>, Aaron Jones <aaronmdjones@gmail.com>,
        "Ted Ts'o" <tytso@mit.edu>, linux-security-module@vger.kernel.org,
        linux-kernel@vger.kernel.org, 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>
In-Reply-To: <20150202180806.GE24351@ubuntumail>
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On 2/2/2015 10:08 AM, Serge Hallyn 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.

The fix for that is to a change to the audit system. If the audit system
reported the capabilities relevant to the decision you'd have what you
need. If you failed because you didn't have CAP_CHMOD or you succeeded
because you had CAP_SYS_ADMIN it should show up in the audit record.
Other systems have used this approach.

You could, of course, create a separate capability result log, and I
believe that Nokia had done something along those lines. I think that
adding it to the audit trail is a more rational approach.

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