AUTH_KRB5(8) InterNetNews Documentation AUTH_KRB5(8)
NAME
auth_krb5 - nnrpd Kerberos v5 authenticator
SYNOPSIS
auth_krb5 [-i instance]
DESCRIPTION
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.
EXAMPLE
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.
BUGS
Currently, any username containing realm information (containing "@") is rejected. This is to prevent someone from passing in a username
corresponding to a principal in another realm that they have access to and gaining access to the news server via it. However, this is also
something that people may wish to do under some circumstances, so there should be a better way of handling it (such as, perhaps, a list of
acceptable realms or a -r flag specifying the realm in which to attempt authentication).
It's not clear the right thing to do when the username passed in contains a "/" and -i was also given. Right now, auth_krb5 will create a
malformed Kerberos principal with multiple instances and attempt to authenticate against it, which will fail but perhaps not with the best
error message.
HISTORY
Originally written by Christopher P. Lindsey. This documentation was written by Russ Allbery <rra@stanford.edu> based on Christopher's
original README file.
$Id: auth_krb5.pod 8595 2009-08-21 08:29:26Z iulius $
SEE ALSO
ckpasswd(8), nnrpd(8), readers.conf(5).
The latest version of Christopher's original nnrpkrb5auth may be found on his web site at <http://www.mallorn.com/tools/>.
INN 2.5.3 2009-09-11 AUTH_KRB5(8)