On Wed, 2008-04-02 at 15:56 -0400, Joshua Brindle wrote: > 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. Well, you know how I feel about encapsulation in general ;) But what I am not clear about is how we would maintain a stable ABI for libsepol if we exposed the policydb and its child data structures directly to the users. Think back to recent changes (or any of the changes) we've made to the policydb over time, such as the permissive type changes, the policy capabilities changes, the pending user transition changes, etc. How would we have done that in a way that preserved a stable libsepol ABI if the policydb had been exposed? I guess I need to go back and read Ulrich's paper again. -- Stephen Smalley National Security Agency -- This message was distributed to subscribers of the selinux mailing list. If you no longer wish to subscribe, send mail to majordomo@xxxxxxxxxxxxx with the words "unsubscribe selinux" without quotes as the message.
