Re: [RFC] Source Policy, CIL, and High Level Languages

[Daniel J Walsh <dwalsh@redhat.com>]

On 07/17/2014 04:37 PM, Stephen Smalley wrote:
> On 07/17/2014 04:04 PM, Steve Lawrence wrote:
>> On 07/17/2014 03:48 PM, Stephen Smalley wrote:
>>> On 07/17/2014 03:10 PM, Stephen Smalley wrote:
>>>> On 07/17/2014 02:58 PM, Steve Lawrence wrote:
>>>>> I think the only remaining issue is the one Dominick mentioned in his
>>>>> first email regarding file_contexts.homedirs. I don't think this is an
>>>>> actual bug, just the migration script migrating things that don't need
>>>>> to be migrated. Still investigating it. We should have an update
>>>>> sometime tomorrow.
>>>> So everything you reverted you restored in equivalent form?
>>>>
>>>>>> What new functionality is included here that was not previously
>>>>>> supported by the old policy toolchain?
>>>>> In terms a user would see, the most visible change is support for CIL
>>>>> policies and HLLs, of which there's only one right now (pp2cil). There
>>>>> are also some new semanage.conf options (target-platform, compiler-dir,
>>>>> ignore-module-cache, store-root) but I imagine the vast majority of
>>>>> people could just use the defaults. Similarly, we've added
>>>>> --ignore-module-cache and --store-root to the semodule command. We've
>>>>> also moved the store to /var/lib/selinux, but this is more behind the
>>>>> scenes and should really only affect distributions.
>>>> What about new features/options of the user-facing commands?  I know
>>>> some features were copied from earlier source/CIL releases into the main
>>>> selinux userspace (e.g. enabled/disabled modules), but aren't some
>>>> things like module priorities new?
>>>>
>>>>> Though, there are two things we just realized have a different behavior.
>>>>>
>>>>> 1) verify_modules is now performed on the CIL modules, rather than pp
>>>>> (or HLL) modules. So if someone is using verify_modules, things will
>>>>> probably break. I'm not sure if anyone uses this feature or how
>>>>> important it is that we maintain backwards compatibility.
>>>>>
>>>>> 2) verify_linked is no longer called, since there isn't any concept of a
>>>>> linked base module with CIL
>>>>>
>>>>> Aside from that, I think all functionality should remain the same.
>>>> I'm not aware of anyone using anything other than verify kernel.
>>>>
>>>>>> Any chance of getting a hll compiler for refpolicy source modules, i.e.
>>>>>> in .if/.te/.fc form?
>>>>> That's in the plan. Jim has a tool that will compile .if/.te/.fc to CIL,
>>>>> but the current HLL infrastructure may need some changes before that can
>>>>> be supported. I think the main problem is that Jim's tool needs
>>>>> knowledge of all modules to be able to convert them to CIL, but the
>>>>> current HLL infrastructure compiles each module separately. We have
>>>>> various ideas on how we can update the HLL infrastructure to support
>>>>> this, but we've primarily been focused on getting the core CIL/HLL
>>>>> functionality complete and upstreamed before focusing on the more
>>>>> complicated HLL patterns.
>>>> Ok.  Ultimately audit2allow -M i.e. sepolgen module compiler should be
>>>> re-tooled to generate source modules, and we'll essentially need a
>>>> workflow that replaces the old make -f /usr/share/selinux/devel/Makefile
>>>> mymodule.pp; semodule -i mymodule.pp.
>>> I guess one other possible concern might be storage:
>>>
>>> $ du -sh /etc/selinux/targeted/modules /var/lib/selinux/
>>> 5.4M	/etc/selinux/targeted/modules
>>> 11M	/var/lib/selinux/
>>>
>>> I'm guessing that is just the cost of storing each module in both binary
>>> and cil form?
>> Yep, we store both HLL and CIL. They are both compressed and CIL
>> compresses decently since it's just text, but it's still a lot of text.
>>
>>> Is there an option to discard the .pp files altogether and only retain
>>> the cil files?
>> Not at the moment, but it wouldn't be hard to accomplish. Just need to
>> delete all the hll files and change the contents of lang_ext to 'cil'.
>> Something we could add if storage is an issue.
> That worked, albeit I had to learn that lang_ext must not include a
> newline or libsemanage won't accept it.  Took it down to 5.8M.  I
> suspect we could also stop retaining a copy of certain generated files
> like file_contexts although that is no different than the current code.
>
> Not sure what benefit there is in retaining the pp files, since they
> carry no additional information AFAIK and they aren't human viewable or
> editable.  Is there even an option for exporting modules from the policy
> store currently that would allow extracting them except via direct file
> access to the policy store?
>
> More generally, if the user knows that the hll module is going to be
> saved elsewhere, then there is no reason to retain a copy in the policy
> store, so having the option of dropping the hll version, either for all
> modules or for specific modules, seems useful.
> _______________________________________________
> Selinux mailing list
> Selinux@tycho.nsa.gov
> To unsubscribe, send email to Selinux-leave@tycho.nsa.gov.
> To get help, send an email containing "help" to Selinux-request@tycho.nsa.gov.
>
>
BTW Moving the policy out of /etc is also great.  I would like to see
policy loaded from
/var/lib/selinux/ if it exists and then look in /usr/lib/selinux/ if it
does not.  Then distributions could
ship their own policies, and if a user wanted to get back to Factory
install he could just rm -rf /var/lib/selinux