Hi all,

We are working on a FreeIPA infrastructure, but we are facing an issue 
regarding GSSAPI authentication against 389ds. Our infrastructure is currently 
moving from enabled to disabled reverse DNS resolution on Kerberos clients. We 
are also using load-balanced DNS aliases and, as a consequence, nodes of 
distributed services must provide keys for both a canonical service principal 
and a localhost service principal.

This setup is similar to the one commonly used for HA proxies, which is 
described in the 389ds' documentation[1].

We configured the keytab accordingly (ipa01.example.net is the FreeIPA node and 
ldap.example.net is the load-balanced alias):

KVNO Timestamp           Principal
---- ------------------- ------------------------------------------------------
   1 06/30/2020 10:24:28 ldap/[email protected]
   1 06/30/2020 10:24:28 ldap/[email protected]
   1 06/30/2020 11:18:43 ldap/[email protected]
   1 06/30/2020 11:18:43 ldap/[email protected]

SASL/GSSAPI authentication works when connecting to ipa01.example.net, or 
ldap.example.net but only if [libdefaults].rdns=true in /etc/kbr5.conf. When 
rDNS resolution is disabled, authentication doesn't work any more:

$ ldapwhoami -QY GSSAPI -H ldaps://ldap.example.net
ldap_sasl_interactive_bind_s: Invalid credentials (49)

The ticket [email protected]>ldap/[email protected] is in the 
ccache, but 389ds rejects it even though the matching key is available in its 
keytab.

It seems 389ds is checking the incoming ticket against the "nsslapd-localhost" 
parameter, and rejects it if they are not matching:

dn: cn=config
nsslapd-localhost: ipa01.example.net

Setting "nsslapd-localhost" to "ldap.example.net" fixed this issue, but it 
causes authentication to ldap/[email protected] to stop working. 
Also it is not possible to have multiple "nsslapd-localhost" entries.

Is there a way to disable checking against "nsslapd-localhost" to allow 
authentication against any key from the configured keytab (we use 389ds version 
1.3.10.2)?

Julien Rische
CERN


[1] 
https://directory.fedoraproject.org/docs/389ds/howto/howto-loadbalance-gssapi.html
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