Problems with kprop and incremental propagation - works but bugs found

[Jeremy Hunt]

Hi Greg,

I don't know that your conclusions are necessarily true. I would say the only bug is that the location of the principal database (and therefore the location of kdc.conf) is not settable in krb5.conf. My point is that if you can override the kdc location in krb5.conf then you can put the correct subsection in the realms section of the kdc.conf and everything will work. Of course, if Matej had been able to set the location of his principal database in the krb5.conf file, then everything would work as he defined it from that file without reference to a kdc.conf file.

  I administer a more static domain than Matej, but I suspect that is irrelevant. I built my version of kerberos to use /krb5 as the containing directory for everything and configured incremental propagation entirely in kdc.conf. I needed none of the workarounds Matej did, my incremental propagation works seamlessly.

To put this in perspective my realm is used correctly and so is Matej's now he has correctly defined his domain in the domain_realm section of krb5.conf.  The location of my principal database is /krb5/var/krb5kdc, this is not a typical location.

I put the directives as defined in the documentation in the subsection for my domain in the realms section of the kdc.conf file, and put the kdc.conf file in the same directory as the principal database. I built my kerberos by configuring with " --prefix=/krb5 --exec-prefix=/krb5" which set @LOCALSTATEDIR+/krb5/var in the Makefile, this defines the location of my principal database as /krb5/var/krb5kdc.

For what it is worth here is a sanitised version of my configuration, which works as advertised with no principal pathnames defined:

/krb5/etc/krb5.conf
--------------------------
[libdefaults]
#     irrelevant, except possibly this
         default_realm = MYREALM.COM

[appdefaults]
#     irrelevant

[realms]
#      only relevant in it defines where propagation is from and to
         MYREALM.COM = {
                 kdc = kdc1
                 kdc = kdc2
                 admin_server = kdc1
#              I am not advertising my password port here
                 kpasswd_server = kdc1:myPasswdPort
         }

[domain_realm]
#    The lines for my kdc systems probably set the realm correctly. this is satisfactory if you can do it this way.
#    Matej's setting is more general, more elegant and entirely satisfactory,
#    remember his settings were initially wrong and this was one of the causes of his problems
        kdc1 = MYREALM.COM
        kdc2 = MYREALM.COM
        sys1 = MYREALM.COM
        sys2 = MYREALM.COM
        sys3 = MYREALM.COM
#     etcetera

[logging]
#     irrelevant

/krb5/var/krb5kdc/kdc.conf
-------------------------------------
[kdcdefaults]
#     irrelevant

[realms]
         MYREALM.COM= {
#              Left out irrelevant stuff in this email like principal flags and enctypes, ports, files used, etcetera
#              From my build, the location of  kdc.conf is known
#              The realm is referred to in this subsection.
#              Incremental propagation is defined in the simplest way
#              the principal database is found and the correct realm is used
                 iprop_enable = true
                 iprop_port = 2107
         }

[logging]
#     irrelevant

On 16/11/2010 11:14 AM, Greg Hudson wrote:
> [safeTgram (safetgram-in) receive status: NOT encrypted, NOT signed.]
>
>
> I can confirm two bugs that you have encountered and worked around:
>
> 1. kprop uses krb5_sname_to_principal() to determine its client
> principal, and does not understand the referral realm.  So it does not
> work without a -r parameter unless the profile's domain_realm section
> can map the local hostname.  You worked around this by correcting your
> existing domain_realm section in your profile.
> A reasonable, if not perfect, fix here is to do what kpropd does in a
> similiar piece of code: substitute the default realm for the referral
> realm when using the result of krb5_sname_to_principal() as a client
> principal.
>
> 2. kpropd, when processing incremental updates, modifies the KDB using
> ulog_replay(), but does not initialize its context to use the KDC
> profile, so it uses only settings from krb5.conf to find the KDB.  You
> worked around this with symlinks.  An alternative workaround would be to
> put the KDB configuration into krb5.conf instead of kdc.conf.  (In the
> past, it used to be required to put KDB configuration into krb5.conf.
> That odd requirement was relaxed somewhere around krb5 1.5 for most
> programs which run on the KDC, but a few have escaped the net, including
> kpropd.)
>
> I will open issues for both bugs and try to get them fixed for 1.9.
> Thanks for your investigative work.
>
>
> ________________________________________________
> Kerberos mailing list           Kerberos at mit.edu
> https://mailman.mit.edu/mailman/listinfo/kerberos
>


-- 

"The whole modern world has divided itself into Conservatives and Progressives. The business of Progressives is to go on making mistakes. The business of the Conservatives is to prevent the mistakes from being corrected." -- G. K. Chesterton