auth_krb58

Usage

Overview

This program does authentication for nnrpd against a Kerberos v5 KDC. This is NOT real Kerberos authentication using service tickets; instead, a username and password is used to attempt to obtain a Kerberos v5 TGT to confirm that they are valid. As such, this authenticator assumes that nnrpd has been given the user's username and password, and therefore is not as secure as real Kerberos authentication. It generally should only be used with NNTP over TLS to protect the password from sniffing.

Normally, you do not want to use this authenticator. Instead, use ckpasswd with PAM support and configure the nnrpd PAM stack to use a Kerberos PAM module. A full Kerberos PAM module is more sophisticated about how it validates passwords and has a much broader array of options than this authenticator.

Options

-i instance

If this option is given, instance will be used as the instance of the principal received from nnrpd and authentication will be done against that principal instead of the base principal. In other words, a principal like "user", when passed to auth_krb5 invoked with "-i nntp", will be transformed into "user/nntp" before attempting Kerberos authentication.

Since giving one's password to nnrpd is not as secure as normal Kerberos authentication, this option supports a configuration where all users are given a separate instance just for news authentication with its own password, so their regular account password isn't exposed via NNTP.

Examples

The following readers.conf(5) fragment tells nnrpd to authenticate users by attempting to obtain Kerberos v5 TGTs for them, appending an instance of "nntp" to usernames before doing so:

    auth kerberos {
        auth: "auth_krb5 -i nntp"
    }
    access kerberos {
        users: "*/nntp"
        newsgroups: example.*
    }

Access is granted to the example.* groups for all users who successfully authenticate.