On Fri, 02 Aug 2013 17:53:25 +0100 David Howells <[email protected]> wrote:
> Jeff Layton <[email protected]> wrote: > > > > + /* -1 indicates the current user */ > > > + if (_uid == (uid_t)-1) { > > > + uid = current_uid(); > > > > Isn't it possible to have a valid uid of (unsigned int)-1? I know that > > at least some sites use that for "nobody". Why not just require passing > > in the correct UID? > > See setresuid() and co. - there -1 is "don't change". > <facepalm> Good point. I got confused between -1 and -2. I think Solaris uses (uid_t)-2 for nobody. Using -1 in this case should be fine. > > Looks good overall, but I share Daniel's concerns about making > > krb5-specific infrastructure like this. Essentially this is just a > > persistent keyring that's associated with a kuid, right? Perhaps this > > could be done in such a way that it could be usable for other > > applications in the future? > > It's not too hard, I suppose: > > keyctl_get_persistent(uid, prefix, destring) > > eg: > > keyctl_get_persistent(-1, "_krb.", KEYCTL_SPEC_PROCESS_KEYRING) > > giving: > > struct user_namespace > \___ .krb_cache keyring > \___ _krb.0 keyring > \___ _krb.5000 keyring > \___ _krb.5001 keyring > | \___ tkt785 big_key > | \___ tkt12345 big_key > \___ _afs.5000 keyring > \___ afs.redhat.com rxrpc > > The other way to do it is create one keyring per user and let userspace create > subkeyrings under that: > > struct user_namespace > \___ .krb_cache keyring > \___ _uid_p.0 keyring > \___ _uid_p.5000 keyring > \___ _uid_p.5001 keyring > \___ krb keyring > | \___ tkt785 big_key > | \___ tkt12345 big_key > \___ afs keyring > \___ afs.redhat.com rxrpc > That's probably what I'd suggest. Allow one persistent keyring per user, and expect userland to organize things sanely under it. nit: I probably wouldn't call the top-level keyring "krb_cache" though ;) > In the above scheme, it might be worth just making these the same as the user > keyring - which means KEYCTL_SPEC_USER_KEYRING will automatically target it. > > Simo: I believe the problem you have with the user keyring is that it's not > persistent beyond the life of the processes of that UID, right? > Possibly. It really comes down to what sort of lifecycle you expect here. Some applications might be caught by surprise if the per-user keyring was already populated in certain situations. OTOH, they have the same problem if there's even one running process with that uid so maybe it's not a big deal. If you do this, it might make sense to allow the admin to tune the expiry sysctl in such a way that user keyrings go away as soon as the last reference is gone (maybe by setting it to 0?). -- Jeff Layton <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
