[Freeipa-devel] fixing Kerberos principal aliases handling in IPA

[Simo Sorce]

On Wed, 2015-09-02 at 14:19 +0200, Sumit Bose wrote:
> On Wed, Sep 02, 2015 at 02:10:52PM +0200, Martin Kosek wrote:
> > On 09/01/2015 04:53 PM, Simo Sorce wrote:
> > > On Tue, 2015-09-01 at 16:39 +0200, Martin Babinsky wrote:
> > >> Hi list,
> > >>
> > >> I own the following ticket https://fedorahosted.org/freeipa/ticket/3864 
> > >> and I would like to clarify what needs to be done in order to make IPA 
> > >> to fully support multiple aliases per entry.
> > >>
> > >> So far I have identified these task based on the ticket comments and 
> > >> discussion with Simo way back in the past:
> > >>
> > >> 1.) mark 'ipaKrbPrincipalAlias' attribute as deprecated so that it is 
> > >> not used in the new code.
> > >>
> > >> 2.) fix ACIs that do not permit setting multiple values of 
> > >> 'krbPrincipalName' attribute per entry (see 
> > >> https://fedorahosted.org/freeipa/ticket/3961)
> > >>
> > >> 3.) Modify KDB backend (namely 'ipadb_fetch_principal' and 
> > >> 'ipadb_find_principal' functions) to correctly perform lookup of 
> > >> krbprincipalname/krbcanonicalname, i.e. search krbprincipalname 
> > >> case-insensitively and krbcanonicalname case-sensitively, return 
> > >> krbcanonicalname when canonicalization is requested.
> > >>
> > >> 4.) Modify KDB backend and IPA framework to handle creation of both 
> > >> krbprincipalname and krbcanonicalname. I am not quite sure what cases 
> > >> should be covered here (I remember that we should create 
> > >> krbcanonicalname when we add another aliases to krbprincipalname), so it 
> > >> would be nice if you could comment on this.
> > >>
> > >> 5.) write tests which cover all this stuff so that we don't shoot 
> > >> ourselves in the foot.
> > >>
> > >> I am not very well versed in Kerberos so I might get some of this stuff 
> > >> wrong. If that's the case please point me to the right direction. Also 
> > >> please write me some additional stuff which I have fogot and needs to be 
> > >> done.
> > >>
> > > 
> > > I think the summary is correct, the only thing we need to be careful is
> > > to keep handling entries that have only a single valued krbprincipalname
> > > correctly as that will happen in upgrade paths and potentially if
> > > someone uses external tools.
> > > 
> > > The tricky part for point 3 is to implement it *without* changing the
> > > schema. KrbPrincipalName is case-sensitive, however I think we can solve
> > > the issue of "searching case-insensitively" by always lower-casing the
> > > principal name components and always upper casing the realm part on
> > > storage. If we always store a krbCanonicalName we get the "correct" case
> > > there anyway so out mucking with the krbPrincipalName case will not be a
> > > problem for any new entry.
> > > 
> > > This *may* cause issues with upgrades though, so we may need fallback
> > > code that searches with the case sent by the client if we determine the
> > > entry has no krbCanonicalName attribute (sign that it was created before
> > > we started adding krbCanonicalName and never "updated").
> > > 
> > > Note that we also need to think what will happen during and upgrade when
> > > some servers still use the current code and some servers will use the
> > > new code. So I guess it would be nice if you could write down a table
> > > with all possible forms a principal can be in on rows, and old/new
> > > server states in columns, and mark what will happen for various
> > > operations in each case.
> > > 
> > > Simo.
> > 
> > The list looks OK. Do we also plan to change the default RDN for new services
> > or other objects that use krbPrincipalName as RDN at the moment?
> > 
> > AFAIU, we are supposed to always use krbCanonicalName as the primary RDN and
> > then only allow krbPrincipalName to be added for the aliases. Of course, the
> > framework needs to still work with old services having krbPrincipalName.
> 
> no, I think we can/should keep krbPrincipalName e.g. becasue krbCanonicalName
> is only optional according to the scheme.

We might stropping using either and use CN instead for the RDN.

Simo.


-- 
Simo Sorce * Red Hat, Inc * New York