[Samba] question about ldap passwd sync

[FM]

Hello
for unix sync password we can add a custom script ot sync password :
passwd program =

Which ldap tool samba is using to sync password ? Is is possible to use 
a home made script ?

My unix password are hardcoded ({SASL}user at REALM) because of kerberos 5 
auth so I use a perl script to update the krb5 database

thanks !