auth_krb5(8)

1AUTH_KRB5(8)              InterNetNews Documentation              AUTH_KRB5(8)
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NAME

6       auth_krb5 - nnrpd Kerberos v5 authenticator
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SYNOPSIS

9       auth_krb5 [-i instance]
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DESCRIPTION

12       This program does authentication for nnrpd against a Kerberos v5 KDC.
13       This is NOT real Kerberos authentication using service tickets;
14       instead, a username and password is used to attempt to obtain a
15       Kerberos v5 TGT to confirm that they are valid.  As such, this
16       authenticator assumes that nnrpd has been given the user's username and
17       password, and therefore is not as secure as real Kerberos
18       authentication.  It generally should only be used with NNTP over TLS to
19       protect the password from sniffing.
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21       Normally, you do not want to use this authenticator.  Instead, use
22       ckpasswd with PAM support and configure the nnrpd PAM stack to use a
23       Kerberos PAM module.  A full Kerberos PAM module is more sophisticated
24       about how it validates passwords and has a much broader array of
25       options than this authenticator.
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OPTIONS

28       -i instance
29           If this option is given, instance will be used as the instance of
30           the principal received from nnrpd and authentication will be done
31           against that principal instead of the base principal.  In other
32           words, a principal like "user", when passed to auth_krb5 invoked
33           with "-i nntp", will be transformed into "user/nntp" before
34           attempting Kerberos authentication.
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36           Since giving one's password to nnrpd is not as secure as normal
37           Kerberos authentication, this option supports a configuration where
38           all users are given a separate instance just for news
39           authentication with its own password, so their regular account
40           password isn't exposed via NNTP.
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EXAMPLE

43       The following readers.conf(5) fragment tells nnrpd to authenticate
44       users by attempting to obtain Kerberos v5 TGTs for them, appending an
45       instance of "nntp" to usernames before doing so:
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47           auth kerberos {
48               auth: "auth_krb5 -i nntp"
49           }
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51           access kerberos {
52               users: "*/nntp"
53               newsgroups: example.*
54           }
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56       Access is granted to the example.* groups for all users who
57       successfully authenticate.
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BUGS

60       Currently, any username containing realm information (containing "@")
61       is rejected.  This is to prevent someone from passing in a username
62       corresponding to a principal in another realm that they have access to
63       and gaining access to the news server via it.  However, this is also
64       something that people may wish to do under some circumstances, so there
65       should be a better way of handling it (such as, perhaps, a list of
66       acceptable realms or a -r flag specifying the realm in which to attempt
67       authentication).
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69       It's not clear the right thing to do when the username passed in
70       contains a "/" and -i was also given.  Right now, auth_krb5 will create
71       a malformed Kerberos principal with multiple instances and attempt to
72       authenticate against it, which will fail but perhaps not with the best
73       error message.
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HISTORY

76       Originally written by Christopher P. Lindsey.  This documentation was
77       written by Russ Allbery <eagle@eyrie.org> based on Christopher's
78       original README file.
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