Re: How is policy.31 created from modules under /usr/share/selinux

[Chris PeBenito <pebenito@ieee.org>]

On 12/13/20 12:06 PM, Ashish Mishra wrote:
> Hi Chris / Richard / Steve ,
> 
> I tried the suggested approach w.r.t Monolithic & also the patch suggested .
> It seems it's creating policy.31 under DESTDIR directories .
> 
> a) Is there anything I can check specifically and share observations ?

I don't understand what you're asking.


> b) Any link where we have this thread available for future reference.
>      I wanted to know if we have any archive which can be accessed like
> other community
>      Something like https://lists.yoctoproject.org/g/poky/topics

The mail list archive is here: https://lore.kernel.org/selinux-refpolicy/


> On Thu, Dec 10, 2020 at 3:32 AM Chris PeBenito <pebenito@ieee.org> wrote:
>>
>> On 12/9/20 11:13 AM, Richard Haines wrote:
>>> On Wed, 2020-12-09 at 10:07 -0500, Steve Lawrence wrote:
>>>>
>>>> On 12/9/20 9:37 AM, Richard Haines wrote:
>>>>> On Wed, 2020-12-09 at 19:42 +0530, Ashish Mishra wrote:
>>>>>> Hi Richard ,
>>>>>>
>>>>>> Will check with the monolithic policy to check the behavior of
>>>>>> the
>>>>>> semodule as you suggested.
>>>>>>
>>>>>> Is there any similar approach / workaround for modular one?
>>>>>
>>>>> I've only had a quick look at code and I could see two ways to fix:
>>>>> 1) Modify the Rules.modular part of the make file to move or copy
>>>>> the
>>>>> policy and file contexts set of files over to $DESTDIR.
>>>>> 2) Modify semodule/semanage to handle $DESTDIR. I think this would
>>>>> be
>>>>> more difficult to fix as lots go on here.
>>>>>
>>>>
>>>> semodule does accept the -p option to change the root, so we could
>>>> feed
>>>> DESTDIR into that. For example, a minimally tested patch:
>>>>
>>>> diff --git a/Rules.modular b/Rules.modular
>>>> index d6224e95..64d953dc 100644
>>>> --- a/Rules.modular
>>>> +++ b/Rules.modular
>>>> @@ -55,8 +55,8 @@ load: $(instpkg) $(appfiles)
>>>>    # make sure two directories exist since they are not
>>>>    # created by semanage
>>>>           @echo "Loading configured modules."
>>>> -       @$(INSTALL) -d -m 0755 $(policypath) $(dir $(fcpath))
>>>> -       $(verbose) $(SEMODULE) -s $(NAME) -i $(modpkgdir)/$(notdir
>>>> $(base_pkg)) $(foreach mod,$(mod_pkgs),-i $(modpkgdir)/$(mod))
>>>> +       @$(INSTALL) -d -m 0755 $(policypath) $(dir $(fcpath))
>>>> $(DESTDIR)/var/lib/selinux
>>>> +       $(verbose) $(SEMODULE) -p $(DESTDIR)/ -s $(NAME) -i
>>>> $(modpkgdir)/$(notdir $(base_pkg)) $(foreach mod,$(mod_pkgs),-i
>>>> $(modpkgdir)/$(mod))
>>>>
>>>>    ########################################
>>>>    #
>>>>
>>>>
>>>> Note that we need to create $(DESTDIR)/var/lib/selinux since semanage
>>>> expects that to already exist.
>>>>
>>>> Though, I would suggest that maybe the "install" target should run
>>>> the
>>>> above semodule command with the --noreload option to install all
>>>> files
>>>> and build the policy binary but not actually load it into the kernel.
>>>> Then make load just becomes something like
>>>>
>>>>     semodule -p $(DESTDIR)/ --reload
>>>>
>>>> Makes a clear distinction between installing everything that's needed
>>>> vs actually loading the policy into the kernel. Happy to create a
>>>> patch
>>>> if that approach makes sense.
>>>
>>> Thanks Steve, that worked for me, however I guess Chris needs to
>>> comment as the $(DESTDIR)/var/lib/selinux needs to be generated and
>>> maybe a clarification comment in the README. Also need comment
>>> regarding the use of --reload/--noreload.
>>
>> To my knowledge, the history is that semodule was only intended to run on the
>> target system.  If you wanted to precreate a policy you could
>> semodule_link+semodule_expand like what is leveraged in the validate target.
>>
>> I'd take a patch that changes the Makefile behavior but would like some real
>> testing first.
>>
>> --
>> Chris PeBenito


-- 
Chris PeBenito