On Sun, Apr 08, 2018 at 11:00:53PM +0200, Lukas Vrabec wrote:
> Hi All,
> 
> I'm reading "SELINUX COMMON INTERMEDIATE LANGUAGE MOTIVATION AND DESIGN"
> wiki page [1] and I'm interested in CIL namespaces. I tried several
> examples related to blockinheritence and all works just great!
> 
> However, in following example I see keyword "blockinheritfilter":
> 
> (block logger
>       (blockabstract logger)
>       (type process)
>       (type log)
>       (allow process log (file (getattr append write))))
> 
> (block myapp
>       (blockinherit logger)
>       (blockinheritfilter myapp logger
>               (allow process log (file (write)))))
> 

The example above actually demonstrates that you do not need blockinheritfilter 
(and should not use it for this example), instead you can just append rules to 
blocks.

loggers should not open the log file for write and so the main template should 
not include that permission in the first place:

(block logger                                                       
       (blockabstract logger)                                        
       (type process)                                                
       (type log)                                                    
       (allow process log (file (getattr append))))

Then if you have a misbehaving logger you can just append the bad rule to that 
block:

(block badlogger
       (blockinherit logger)
       (allow process log (file (write)))))

Appending instead of filtering probably just the better approach also if you 
consider that blocks might have macros or nested blocks
You probably would not be able to filter any of those.


> 
> If I understand it correctly, it should "remove" rule:
> allow myapp.process log:file write;
> 
> So process type in myapp should have allowed:
> allow myapp.process log:file {getattr append};
> 
> And process type in logger should have allowed:
> allow logger.process log:file {getattr append write};
> 
> Which could be very cool feature, but I don't see any code in secilc
> related to "blockinheritfilter". Are there any plans to implement also
> this in CIL namespaces or is there any other way how to handle this
> (DELETE statement is also not implemented) ?
> 
> Thanks for any help.
> Lukas.
> 
> 
> [1] https://github.com/SELinuxProject/cil/wiki
> 
> -- 
> Lukas Vrabec
> Software Engineer, Security Technologies
> Red Hat, Inc.
> 




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