From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <4E3C0152.7000105@redhat.com>
Date: Fri, 05 Aug 2011 10:42:26 -0400
From: Daniel J Walsh <dwalsh@redhat.com>
MIME-Version: 1.0
To: Stephen Smalley <sds@tycho.nsa.gov>
CC: qingtao.cao@windriver.com, Eric Paris <eparis@redhat.com>,
        "Christopher J. PeBenito" <cpebenito@tresys.com>,
        SELinux <selinux@tycho.nsa.gov>
Subject: Re: checkpolicy is broken (which is not)
References: <4E3AEA75.3090602@redhat.com> <4E3B3D39.4020700@windriver.com>  <4E3B441A.1090900@windriver.com> <4E3B5593.7000502@redhat.com>  <4E3B6F5B.40904@windriver.com> <1312548982.19283.14.camel@moss-pluto>  <4E3BE94F.9010104@redhat.com> <1312550851.19283.35.camel@moss-pluto>
In-Reply-To: <1312550851.19283.35.camel@moss-pluto>
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On 08/05/2011 09:27 AM, Stephen Smalley wrote:
> On Fri, 2011-08-05 at 08:59 -0400, Daniel J Walsh wrote:
>> On 08/05/2011 08:56 AM, Stephen Smalley wrote:
>>> On Fri, 2011-08-05 at 12:19 +0800, Harry Ciao wrote:
>>>> Hi Eric,
>>>> 
>>>> Let me explain more about the background story.
>>>> 
>>>> The existing type rule could declare a type, and optionally 
>>>> associate it with a list of type attributes. So I invented this
>>>>  "role <regular role> attribute <a list of role attributes>"
>>>> rule in the same manner to do the similar things for roles,
>>>> since I figure this would make refpolicy rules similar and easy
>>>> to remember and use.
>>>> 
>>>> Now that the above new role-attr rule takes care of declaring 
>>>> roles, this duty has to be removed from role-type rule in order
>>>> to avoid ambiguity, and the role-type rule would be used to
>>>> only associate types with roles, which only requires TWO lines
>>>> of code as in 3cbc9727, since mostly used roles such as
>>>> system_r have been declared in kernel.te(in order to avoid some
>>>> build failure).
>>>> 
>>>> In a word, we could preserve the behavior of role-type rule,
>>>> but this would introduce discrepancy between that of role-attr
>>>> rule and type-attr rule, considering that getting used to the
>>>> new toolchain only requires an easy cherry-pick of only 2 lines
>>>> of change, would it be that desirable for us to do so?
>>> 
>>> I don't think we should introduce an incompatible policy language
>>>  change without very strong reasons.  It is fine to introduce new
>>>  constructs like your role...attribute construct, but we
>>> shouldn't change the meaning of role...type statements and
>>> thereby render invalid policies that used to be valid.
>>> 
>> 
>> Well I will say that I thought the old construct did not make
>> sense, since we have to declare most objects in the lanquage except
>> for roles.
>> 
>> This will help to find problems in the policy also like people
>> doing
>> 
>> role httpd_t types httpd_t;
>> 
>> Which I have seen in the past.
>> 
>> I just got the new toolchain to work with Fedora policy.
> 
> So are you saying that you are fine with a newer checkpolicy not 
> accepting previously valid policy modules?  Such that someone who
> wants to upgrade checkpolicy in an existing distribution release
> (e.g. RHEL6) can only do so if they also upgrade/modify their
> policy?

This is a theoretical about something we would never do.  RHEL Releases
are stable and we don't update tool chains, just bug fix.  Maybe third
parties would and then it would be up 2 them to fix their policies.

> 
> Just to be clear, the role...types statement was in fact the role 
> declaration in the original language, and you could originally only
> have one of them per role.  We later allowed multiple statements per
> role and took the union of the types to permit decomposition of the
> policy into per-domain source modules.
> 

I understand, but I think this was a mistake that allows us, the policy
writer to be sloppy.
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