Re: Need to break or reduce the dependency on a static libsepol

[Joshua Brindle <jbrindle@tresys.com>]

Joshua Brindle wrote:
> Stephen Smalley wrote:
>> This is likely my fault, but we're encountering increasing
>> problems from growth in the set of things that depend on the
>> static libsepol whenever we make a change to libsepol,
>> particularly a policy version change.  We now have (at least)
>> the following dependencies on it:
>> checkpolicy (always true, not likely to go away) libselinux
>> (for the audit2why python binding module, which used to be
>> its own utility in policycoreutils) setools
>>
>> Does slide also have this dependency or is it clean? Anything else to
>> worry about? 
>>
>> The result is that when a newer libsepol gets incorporated
>> and libselinux or setools does not, we encounter breakage
>> (unable to find a policy file they can read or unable to read
>> the policy file at which they are pointed) or confusion
>> (reading an older policy file left around from before the
>> libsepol update) upon trying to use audit2why or setools.
>>
>> We ran into this problem twice in rawhide / F9, once upon the
>> policy capability support (policy.22) and now for permissive types
>> (policy.23). 
>>
>> Only real way forward that I can see it to actually
>> encapsulate the interfaces required by audit2why and setools
>> so that they can use the shared libsepol.
> 
> One thing that we are doing for policyrep is encapsulating all the "add
> this kind of thing to a policydb" functionality because we didn't want
> policyrep users to be static libsepol users. 
> 
> This has multiple disadvantages including its huge, it is slow (7 hash
> lookups to add an av rule currently, since its string based) and doesn't
> include the other functionality like the security server, query
> functions that would be required for audit2why and setools.
> 
> After going through that effort and seeing the pain first hand I
> honestly think it is a better alternative to forgo encapsulation and
> just make the policydb public. Not yet though, since we ripped out all
> the module stuff in it for policyrep. Since it is returning to a more
> pristine state that can't realistically change much in the future maybe
> it would be better for everyone to rip out the encapsulation as well.
> 

What are your thoughts on this Steve? Karl agrees with me, the 
encapsulation we have is pretty fake in some places (eg., the interface 
between libsemanage and libsepol) and doesn't help in most others. The 
shared interfaces for everything in libsepol will be _huge_, the ones we 
wrote for policyrep were huge by themselves.

I think libsepol should be the library that knows how to read and write 
a policydb, maybe has a security server implementation but otherwise 
lets people manipulate the policydb however they wish. It would make the 
library much smaller, get rid of the need to statically build and be 
much less work in the long run.

I still think we need to wait until the wide sweeping policyrep changes 
since they remove all the module junk from policydb but after that (or 
perhaps at the same time?) we should just make policydb public and 
slowly remove the unneeded encapsulation.


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