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.\" $FreeBSD$
.\" Copyright 1989 by the Massachusetts Institute of Technology.
.\"
.\" For copying and distribution information,
.\" please see the file <Copyright.MIT>.
.\"
.TH FIX_KDB_KEYS 8 "Kerberos Version 4.0" "MIT Project Athena"
.SH NAME
fix_kdb_keys \- Secure Kerberos database by properly randomising keys
.SH SYNOPSIS
fix_kdb_keys
.SH DESCRIPTION
If you built your Kerberos database before receiving this distribution,
the keys were randomly generated using the vulnerable version of
the Kerberos random number generator. Therefore it is possible for
an attacker to mount an attack to guess these values. If an attacker
can determine the key for the
.I krbtgt
ticket, they can construct tickets claiming to be any Kerberos
principal. Similarly if an attacker can obtain the
.I changepw.kerberos
key, they can change anyone's password.
.PP
This distribution has been patched to use the improved
.IR des_new_random_key()
routines instead of the old and cryptographically suspect
.IR des_random_key().
.PP
The primary difference is that
.IR des_random_key()
uses a seeding
technique which is predictable and therefore vulnerable. While
.IR des_new_random_key()
uses a feedback mechanism based on the Data Encryption Standard
(DES) and is seeded with a secret (and therefore unknown to an
attacker) value. This value is the secret database master key.
.PP
Running
.I fix_kdb_keys
on the KDC server will change these critical keys to new
values using the newer random number generator. IMPORTANT: When this
is done, all outstanding ticket granting tickets will
immediately become invalid. This will be disruptive to your user
community. It is recommended that this is done late at night or early
in the morning before most users have logged in. Alternatively
pre-announce a definitive time when you will run the program and
inform the users that they will have to get new tickets at that time
(using either
.I kinit
or simply by logging out and then in again).
.SH DIAGNOSTICS
Many, and descriptive.
.SH FILES
.TP 20n
/etc/kerberosIV/principal.db
DBM file containing database
.TP
/etc/kerberosIV/master_key
Master key cache file.
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