mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-20 11:11:24 +00:00
61 lines
3.0 KiB
Diff
61 lines
3.0 KiB
Diff
READ THIS ENTIRE FILE BEFORE PROCEEDING!
|
|
|
|
This distribution contains a "diff" file suitable for using with the
|
|
"patch" program to update your Kerberos (version 4) source tree. The
|
|
gist of the patch is to replace calls to des_random_key() with calls
|
|
to des_new_random_key().
|
|
|
|
The primary difference is that des_random_key() uses a seeding
|
|
technique which is predictable and therefore
|
|
vulnerable. 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 database
|
|
master key, which is a convenient secret value.
|
|
|
|
This patch assumes that you have the new_rnd_key.c key module (which
|
|
contains the definition and code for des_new_random_key()). It has
|
|
been part of the standard Version 4 distribution since 1992 and is
|
|
used in the admin server (our primary error at MIT was not upgrading
|
|
all of Kerberos to use this newer generator. This patch finishes the
|
|
job).
|
|
|
|
In addition to the patch file for the Kerberos distribution this
|
|
distribution also contains a program for changing critical system keys
|
|
(namely the "krbtgt" and "changepw.kerberos" keys). When you
|
|
originally built your Kerberos database these keys were chosen at
|
|
random, 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
|
|
"krbtgt" ticket, they can construct tickets claiming to be any
|
|
kerberos principal. Similarly if an attacker can obtain the
|
|
"changepw.kerberos" key, they can change anyone's password.
|
|
|
|
The enclosed "fix_kdb_keys.c" (part of the patch file) program, which
|
|
you run on the KDC server, will change these critical keys to new
|
|
values using the newer random number generator. IMPORTANT: When you
|
|
run fix_kdb_keys, all outstanding ticket granting tickets will
|
|
immediately become invalid. This will be disruptive to your user
|
|
community. We recommend that you either do this 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 your users that they will have to get new tickets at that time
|
|
(using either "kinit" or simply by logging out and then in again).
|
|
|
|
NOTE: The only client program modified is "ksrvutil" which is used to
|
|
generate new server keys. All other client/server programs are
|
|
unaffected. End users do *not* need to obtain new versions of programs
|
|
that use Kerberos. This is because most random number generation in
|
|
the Kerberos system is done on the KDC system. By fixing kerberos.c
|
|
you have repaired most of the damage.
|
|
|
|
To install this patch copy patch_krb to the toplevel of your Kerberos
|
|
source tree. Then type:
|
|
|
|
patch -p0 <patch_krb
|
|
|
|
This will install changes to various kerberos modules to upgrade them
|
|
to use des_new_random_key(). It also will install a new program,
|
|
"fix_kdb_keys.c." After the patch is complete type "make world" at the
|
|
toplevel of your Kerberos source tree. This will, among other things,
|
|
build the fix_kdb_keys program.
|