Use the passwd(1) to change a password. In order to change the password, the userPassword attribute must be writeable by the user. Remember that the serviceAuthenticationMethod for passwd-cmd will override the authenticationMethod for this operation. Depending on the authentication used, the current password might be un-encrypted on the wire.
In the case of pam_unix the new userPassword attribute is encrypted using UNIX crypt and tagged before being written to LDAP. Therefore, the new password is encrypted on the wire, regardless of the authentication method used to bind to the server.
For pam_ldap, when a password is changed, the new password is un-encrypted. Therefore, to insure privacy, you need to use TLS. If TLS is not used, the new userPassword will be subject to snooping.
When setting the password with pam_ldap with the iPlanet Directory Server 5.1, the password is encrypted using the serverStrorageScheme (as it is untagged). See “User Account Management” in the iPlanet Directory Server 5.1 Administrator's Guide for additional information about the passwordStorageScheme attribute.
You need to consider the following when setting the passwordStorageScheme attribute. If a NIS, NIS+, or another client using pam_unix is using LDAP as a repository, then passwordStorageScheme needs to be crypt. Also, if using pam_ldap with sasl/digest-MD5 with the iPlanet Directory Server 5.1, passwrodStorageScheme must be set to clear.