I am trying to set up an OpenLDAP and Kerberos authentication for testing purpose. The setup contains a pair of internal ldap server and Kerberos server and the pair of external ldap server and Kerberos server.


I made the tree of the internal ldap server to be a subordinate of the external server and enabled the saslauthd for authentication on both the internal and the external ldap server to the respective Kerberos server.


I have tested that the LDAP authentication through saslauthd using Kerberos works well on both the internal ldap and Kerberos pair and the external ldap Kerberos pair.


However, when I point the client machine to the external ldap server and the add the subordinate relationship, I could not get the authentication for the uses in the internal ldap directory to work.


For example, when I used “su - peter” where peter is a user in the external ldap server and the password is {SASL}peter@EXAMPLE.COM. The authentication works. However, when I use “su – James” where james is a user defined in the internal ldap server with password {SASL}james@SUB.EXAMPLE.COM, then the authentication failed. I check the log file, the internal server did get the search request forwarded from the external ldap server and returned the correct information back. However, I did not see the saslauthd process on either the external or the internal ldap server get any inquiry for the authentication.


I tried to modify the /etc/krb5.conf and added the realms for both EXAMPLE.COM and SUB.EXAMPLE.COM. Still, the authentication does not work for users defined in the internal ldap server.


Could anyone give me some hints for this issue?