Re: heimdal -> MIT kdc migration

On Sat, Aug 30, 2025 at 9:47 PM Rick Macklem <rick.macklem@gmail.com> wrote:
>
> On Sat, Aug 30, 2025 at 4:22 PM Rick Macklem <rick.macklem@gmail.com> wrote:
> >
> > On Sat, Aug 30, 2025 at 8:56 AM Rick Macklem <rick.macklem@gmail.com> wrote:
> > >
> > > On Fri, Aug 29, 2025 at 1:05 PM Rick Macklem <rick.macklem@gmail.com> wrote:
> > > >
> > > > On Fri, Aug 29, 2025 at 7:43 AM Rick Macklem <rick.macklem@gmail.com> wrote:
> > > > >
> > > > > On Wed, Aug 27, 2025 at 8:39 PM Rick Macklem <rick.macklem@gmail.com> wrote:
> > > > > >
> > > > > > On Wed, Aug 27, 2025 at 7:43 PM Rick Macklem <rick.macklem@gmail.com> wrote:
> > > > > > >
> > > > > > > On Tue, Aug 26, 2025 at 9:35 AM Gleb Smirnoff <glebius@freebsd.org> wrote:
> > > > > > > >
> > > > > > > > On Tue, Aug 26, 2025 at 08:31:13AM -0700, Gleb Smirnoff wrote:
> > > > > > > > T> On Tue, Aug 26, 2025 at 08:13:26AM -0700, Rick Macklem wrote:
> > > > > > > > T> R> Ok. If you install FreeBSD-13.5 and then "pkg install heimdal", you get a
> > > > > > > > T> R> working Heimdal-7.8 in ports.
> > > > > > > > T> R>
> > > > > > > > T> R> Now, I have another challenge. Fixing the master passwords.
> > > > > > > > T> R> I'll work on it later to-day.
> > > > > > > > T>
> > > > > > > > T> I have applied two commits from Heimdal from 2012 that add 'kadmin dump -f MIT'
> > > > > > > > T> feature to our base heimdal and polished them to compile.  So far it doesn't
> > > > > > > > T> work yet, either create an empty dump or create a core dump, instead of
> > > > > > > > T> database dump :) I'll see how difficult it is going to further resolve that to
> > > > > > > > T> a working condition. If I succeed, then having 'dump -f MIT' in base without
> > > > > > > > T> any ports would be the best solution.  Can also be merged to FreeBSD 14.4.
> > > > > > > >
> > > > > > > > Good news.  In the above paragraph I was testing my change incorrectly - threw
> > > > > > > > the new binary on a system running unpatched libraries.  When run correctly,
> > > > > > > > it successfully produced something that looks like a correct dump in MIT format.
> > > > > > > > I haven't yet tried to load it into MIT kdc yet, though.
> > Well, would you like the not so bad news or the bad news??;-)
> > Your patch works, in that it produces a dump that "kdb5_util load
> > -update" can load.
> > After loading, if the principal only has keys for the newer encryption types of
> > aes256-cts-hmac-sha1-96
> > aes128-cts-hmac-sha1-96
> > then you can look at the principal via kadmin.local, but the password must
> > be changed before it works.
> > --> This is the same behaviour as you get if you use Heimdal-7.8 to do the
> >       dump conversion.
> > So far, so good...
> >
> > Now, the not so good news. Once you update the Heimdal libraries
> > (libhdb.so and libkadm5srv.so) "kadmin -l" is broken on the system
> > running the old KDC. "kadmin -l dump" works, but something like:
> > # kadmin -l
> > kadmin> get rmacklem
> > kadmin: get rmacklem: Service key not available
> > - I have not yet looked in your patched sources to see where this
> >   failure comes from?
> >
> > Now, more not so good news...
> > My patch doesn't help.
> > It does re-encrypt the key in the master key from the MIT KDC
> > system, but that doesn't make the password work.
> > When I compared the dump generated via kadmin with both
> > your patch and mine, the key for aes256-cts-hmac-sha1-96
> > is 34bytes long.
> > After doing the change_password so that it works, a dump
> > generated by "kdb5_util dump -r13" (the same dump format)
> > has a key that is 62bytes long.
> > --> So, there is more to converting the key than just re-ecrypting
> >       it. (I'll try and find where the MIT code encrypts a key in a master
> >       key to see why it ends up at 62bytes and whether that can be done
> >       in the old code.)
> >
> > So, if we are going to continue with this...
> > - We need to figure out why your patch breaks "kadmin" for other
> >   things and fix that.
> > - I/we need to figure out how to convert the 34byte key to the MIT
> >   62byte key (and then maybe the password won't need to be changed?).
> >
> > Or do we just say "When you convert the KDC database, all the passwords
> > must be changed to get them to work?".
> All I've got sofar is this patch...
> https://people.freebsd.org/~rmacklem/print.patch
>
> It tweaks entry2mit_string_int() so that it skips over the keys for
> old encryption types and fills in a fake "modified by" entry if none
> exists.
>
> These changes at least make the MIT dump such that the records
> don't end up "incomplete or corrupted" when you try to do something
> like "get_principal <principal>" in kadmin.local.
>
> As noted, your patch makes "kadmin -l" break for most things,
> reporting "Service key not available". The failures go away if
> you revert back to the non-patched libraries.
> I have not located the problem yet.
>
> As for the passwords...no luck yet, rick
Finally..it works. (First off, apologies for all the posts, just ignore
them.;-)

The patch is at:
https://people.freebsd.org/~rmacklem/kadmin.patch

It goes on top of glebius@'s kadmin-dump-MIT branch of
https://github.com/glebius/FreeBSD.

Once built with "WITHOUT_MITKRB5="yes" in /etc/src.conf
and installed, there is a new option for "kadmin -l dump" called
"-f" and  my patch modifies "-f" so it can take a filename instead
of "MIT" or "Heimdal".

Here's how you test it (once your Heimdal KDC system has
been patched):
On the MIT KDC system:
# mkdir /var/db/krb5kdc   <-- maybe the installer should do this?
- copy kdc.conf and kadm5.acl into this directory and edit them
  for your Realm, etc.
- copy an MIT krb5.conf in /etc/krb5.conf and edit this one as well.
(I've attached the three files I use as very basic examples.)
Once you've done this:
# kdb5_util create -s
should work.

Now, copy /var/db/krb5kdc/.k5.YOUR.REALM over to the
Heimdal KDC system.
Then go to the Heimdal KDC system and...
# kadmin -l dump -f .k5.YOUR.REALM mit.dump
Now, copy mit.dump over to the MIT KDC system and
on the MIT KDC system...
# kdb5_util load -update mit.dump

And, at least if the principals on the Heimdal KDC
have keys for at least one of:
aes256-cts-hmac-sha1-96
aes128-cts-hmac-sha1-96
they should work.

For principals that do not have keys for either of
the above two etypes, you should still be able to
see the principal via "get_principal <principal>" in
kadmin.local.
If you can see it, a change_password in kadmin.local
should get it working.

Hopefully people with Heimdal KDCs can test this?

rick


>
>
> >
> > rick
> >
> > > > > > Oh, and one more thing...
> > > > > > - If there are keys for old encryption types like des.. or arcfour..
> > > > > > in the MIT dump,
> > > > > >   those will screw up the load. (You can check and delete them in the
> > > > > > Heimdal-1.5.2
> > > > > >   kdc system via..
> > > > > >   # kadmin -l
> > > > > >   get <principal>
> > > > > >   - if old keys are listed in Keytypes:
> > > > > >   del_enctype <principal> <enctypes>
> > > > > >  exit
> > > > > >
> > > > > >  Ideally the conversion code would skip over these and not put them in the dump.
> > > > > >
> > > > > > rick
> > > > > > ps: If you don't do this, when you "get_principal" in kadmin.local on
> > > > > > the MIT KDC
> > > > > >       system, it will give you a "Database record is incomplete or corrupted..".
> > > > > >
> > > > > > > >
> > > > > > > > I will finalize the branch promptly and share it.  The above experience also
> > > > > > > > indicated that I need to do a library version bump.
> > > > > > > I don't know if you are enthusiastic about pursuing this, but hopefully this
> > > > > > > works and gets the principals in (although I doubt the passwords will
> > > > > > > work without changing them).
> > > > > > >
> > > > > > > To get the passwords to work, I think the following *might* do it:
> > > > > > > - If you look in the Heimdal sources, when "--decrypt" is specified,
> > > > > > >   I think it finds its way down into a function called hdb_unseal_key_mkey()
> > > > > > >   which decrypts the key using the master key by calling _hdb_mkey_decrypt().
> > > > > > >   To get the passwords to work, I think the call to _hdb_mkey_decrypt() would
> > > > > > >   need to be followed by a call to _hdb_mkey_encrypt() with the "key"
> > > > > > >   argument being the master key for the MIT database. (It it a keytab
> > > > > > >   entry called /var/db/krb5kdc/.k5.YOUR.REALM created when you do a
> > > > > > >   "kdb5_util create -s" on the system that will be the MIT KDC.)
> > > > > > >   - Just to make it even more fun, there is a flag called HDB_KU_MKEY
> > > > > > >     which is set to the Heimdal way and not for the MIT way (whatever
> > > > > > >     that really means?).
> > > > > > >   - There is also some stuff about padding in hdb_unseal_key_mkey(),
> > > > > > >     but hopefully that won't be a problem?
> > > > > > >
> > > > > > > I think hdb_read_master_key() can be used to read in the MIT master
> > > > > > > key from the file you provide as an argument to it.
> > > > > > >
> > > > > > > This all is just a hunch, based on what I've seen so far.
> > > > > > >
> > > > > > > I'll admit since the hardware I have takes forever to "make buildworld"
> > > > > > > and I don't know a quick way to build/test these changes, I'm not
> > > > > > > inspired to try it.
> > > > > Although not inspired, I have taken a stab at it.
> > > > > I am still trying to figure out how to build/test it, but I have forked
> > > > > glebius@'s github and added some code to...
> > > > > - Not dump the weak encryption keys (they just cause MIT's kadmin.local
> > > > >   to complain that the principal's database entry is corrupted.
> > > > > - If the argument to "kadmin -l dump" is "-f <mit-master-key-file>" instead
> > > > >   of "-f MIT" it re-encrypts the keys in MIT's master key. (I hope that will
> > > > >   make the passwords work.
> > > > >   (Basically, someone will "kdb5_util create -s" on the MIT KDC system
> > > > >    and then copy the /var/db/krbkdc/.k5.YOUR.REALM file over to the
> > > > >    Heimdal KDC system and do "kadmin -l dump -f <.k5-filename> mit.dump"
> > > > >    then copy "mit.dump" over to the MIT KDC system and
> > > > >    "kdb5_util load -update mit.dump". Then, hopefully, the principals will
> > > > >    work??)
> > > > >
> > > > > Anyhow, it is currently sitting here:
> > > > > github.com/rmacklem/FreeBSD in the kadmin-dump-MIT branch.
> > > > > (I'm as unconversant with git and github as anyone, so if you have
> > > > > trouble finding it, just let me know.)
> > > > Actually, it hasn't made it there yet. For some reason (I think it is
> > > > glebius@s large # of branches) it takes a very long time to "git push"
> > > > a patch involving 4 files. It failed after over an hour with an unexpected
> > > > TCP disconnect. I am running it again.
> > > >
> > > > I will stick the patch here, in case the push fails again.
> > > > (It needs to be applied on top of glebius@'s kadmin-dump-MIT branch.
> > > The patch is here. (For some reason, I couldn't push so I deleted the
> > > github fork.)
> > > https://people.freebsd.org/~rmacklem/kadmin.patch
> > >
> > > I haven't yet been able to test it, but will be able to do so later to-day, rick
> > >
> > > >
> > > > Meanwhile I've given up trying to build it on a universe system and
> > > > an now trying the "make buildworld" locally. This will take days,
> > > > so I guess I'll go do something else.;-)
> > > >
> > > > rick
> > > >
> > > > >
> > > > > I'll keep updating this github fork as I get to test it, but if others
> > > > > know how to build it, feel free to test, rick
> > > > >
> > > > > > >
> > > > > > > rick
> > > > > > >
> > > > > > > >
> > > > > > > > --
> > > > > > > > Gleb Smirnoff