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

[Simo Sorce]

On Wed, 2015-09-02 at 14:36 +0200, Martin Kosek wrote:
> On 09/02/2015 02:32 PM, Simo Sorce wrote:
> > 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.
> 
> This would make changing krbPrincipalName that happens to be RDN much easier.
> Wouldn't this break software that depends on this RDN already?
> 
> Like "ldapsearch -b "<principal>,cn=services,cn=accounts,SUFFIX"?

It would,. but so would a change to krbCanonicalName. If you need to
change something we might as well go CN. Otherwise keep it as is, but I
guess your worry is that the RDN becomes multivalued which is really a
pain.

Simo.

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