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

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.