[5833] in Kerberos
Re: HELP: FAQ on Kerberos
daemon@ATHENA.MIT.EDU (Barry Jaspan)
Thu Sep 7 11:24:43 1995
Date: Thu, 7 Sep 1995 11:14:02 -0400
From: "Barry Jaspan" <bjaspan@cam.ov.com>
To: Richard Dammkoehler <Richard_Dammkoehler@msnotes.wustl.edu>,
cjs@psu.edu (Chris Sacksteder)
Cc: Chris Sacksteder <cjs@psu.edu>, <kerberos@MIT.EDU>
In-Reply-To: [5831]
Here is the most recent version of the FAQ.
Barry
Kerberos Users' Frequently Asked Questions
July 17, 1995
Compiled by: Barry Jaspan, <bjaspan@cam.ov.com>
OpenVision Technologies
Kerberos; also spelled Cerberus. n. The watch dog of
Hades, whose duty it was to guard the entrance--against
whom or what does not clearly appear; . . . it is known
to have had three heads. . .
-Ambrose Bierce, The Enlarged Devil's Dictionary
This document answers Frequently Asked Questions about the Kerberos
authentication system. It is freely distributable. Direct all
responses and questions to bjaspan@cam.ov.com. Most of the
information presented here has been collected from postings to the
comp.protocols.kerberos newsgroup (gatewayed to the mailing list
kerberos@mit.edu).
DISCLAIMER: OpenVision Technologies makes no representations about the
suitability of this information for any purpose. It is provided "as
is" without express or implied warranty. In particular, this document
is not intended as legal advice for exporting Kerberos, DES, or any
other encryption software.
Release Notes: Several answers have been updated to reflect the
release of MIT Kerberos V5 beta 5. The vendor list in question 2.7
has been completely redone. Information on the Kerberos mailing list
has been added to question 1.0. The DCE compatibility information in
question 1.8 has been updated.
Questions addressed in this release:
1. Kerberos and its Many Incarnations
----------------------------------------------------------------------
(1.0) Where can I get more information?
(1.1) What is Kerberos? What is it good for?
(1.2) What different versions and distributions of Kerberos exist?
(1.3) Where can I get Kerberos version 4 or 5?
(1.4) What is the current status of version 4?
(1.5) What is the current status of version 5?
(1.6) Are version 4 and version 5 compatible?
(1.7) How/why is Transarc's Kerberos different from MIT Kerberos V4?
Can they interoperate?
(1.8) How/why is OSF DCE Security different from MIT Kerberos V5?
Can they interoperate?
(1.9) How/why is DEC Ultrix Kerberos different from MIT Kerberos V4?
Can they interoperate?
(1.10) What is Bones? What is it for?
2. Building, Using, Installing, and Administering Kerberos
----------------------------------------------------------------------
(2.1) Can I use Kerberos for local password validation?
(2.2) What is the export status of Kerberos?
(2.3) How can I delete a principal from the database?
(2.4) What are the officially assigned Kerberos port numbers?
(2.5) Are there Kerberos versions of telnet and ftpd?
What other Kerberos clients exist?
(2.6) Why does rlogin print "Warning: No Kerberos tickets obtained"?
(2.7) What vendors provide commercial support for Kerberos?
(2.8) Why do I get an error message from ld when make_commands is
executed?
(2.9) What is libkrb.a, and why can't ld find it?
(2.10) How do I set up a slave server?
4. Miscellaneous
----------------------------------------------------------------------
(4.1) List references for Kerberos and network security in general.
(4.2) Where are archives of comp.protocols.kerberos (a.k.a
kerberos@mit.edu)?
======================================================================
1. Kerberos and its Many Incarnations
----------------------------------------------------------------------
(1.0) Where can I get more information?
The Kerberos mailing list is kerberos@mit.edu. There is a
bi-directional gateway between the list and the newsgroup
comp.protocols.kerberos. Send subscription requests to
kerberos-request@mit.edu.
*** PLEASE DO NOT SEND SUBSCRIPTION REQUESTS TO kerberos@mit.edu. ***
There are a number of Kerberos-related WWW sites. In no particular order:
o <http://www.contrib.andrew.cmu.edu/usr/db74/kerberos.html>. This
site contains links to a variety of other documents, some about
Kerberos, some related Kerberos, and some unrelated to Kerberos.
o <http://nii.isi.edu/info/kerberos>. This site
contains references to Kerberos documentation and technical papers,
available Kerberos distributions, Kerberos-related applications (only
NetCheque, currently), and Kerberos vendor information from this FAQ.
o <http://pscinfo.psc.edu/~studarus/Kerberos>. This site contains
information on setting up Kerberos V5 to use Sandia kadmin, the
r-commands, and the sample server.
o <http://ubvms.cc.buffalo.edu/~tkslen/kerberos.html>. This site
contains installation and configuration notes and help as well as
pointers to a variety of other documents.
(1.1) What is Kerberos? What is it good for?
Kerberos is a network authentication system for use on physically
insecure networks, based on the key distribution model presented by
Needham and Schroeder.[3] It allows entities communicating over
networks to prove their identity to each other while preventing
eavsdropping or replay attacks. It also provides for data stream
integrity (detection of modification) and secrecy (preventing
unauthorized reading) using cryptography systems such as DES.
Kerberos works by providing principals (users or services) with
/tickets/ that they can use to identify themselves to other principals
and secret cryptographic keys for secure communication with other
principals.[1] A ticket is a sequence of a few hundred bytes. These
ticket can then be embedded in virtually any other network protocol,
thereby allowing the processes implementing that protocol to be sure
about the identity of the principals involved.
Practically speaking, Kerberos is mostly used in application-level
protocols (ISO model level 7), such as TELNET or FTP, to provide user
to host security. It is also used, though less frequently, as the
implicit authentication system of data stream (such as SOCK_STREAM) or
RPC mechanisms (ISO model level 6). It could also be used at a lower
level for host to host security, in protocols like IP, UDP, or TCP
(ISO model levels 3 and 4), although such implementations are
currently rare, if they exist at all.
It is important to realize that Kerberos is a one-trick pony. It
provides for mutual authentication and secure communication between
principals on an open network by manufacturing secret keys for any
requestor and providing a mechanism for these secret keys to be safely
propagated through the network. Kerberos does not, per se, provide
for authorization or accounting, although applications that wish to
can use their secret keys to perform those functions securely.
Kerberos also does not provide password validation for individual
workstations unless care is taken; see question 2.1.
It is also important to understand the using Kerberos on time-sharing
machines greatly weakens its protections, since a user's tickets
are then only as secure as the 'root' account (read: not very).
Furthermore, dumb terminals and most X terminals do not understand the
Kerberos protocol and as a result their cable connections remain
insecure.
(1.2) What different versions and distributions of Kerberos exist?
There are several different versions and distributions of Kerberos.
Most of them are based on an MIT distributions in one form or another
but the lineage is not always simple. Some of the distributions are
freely available, some are stand-alone commercial products, and others
are part of a larger free or commercial systems. This list is certain
to be incomplete:
Version of Kerberos V4:
o MIT Kerberos V4. Freely available; see questions 1.4.
o Bones. Freely available; see questions 1.3 and 1.10.
o Transarc AFS. Commercial; see question 1.7.
o Digital Unix. Commercial; see question 1.9.
o Also see question 2.7.
Versions of Kerberos V5:
o MIT Kerberos V5. Freely available; see questions 1.5.
o OSF DCE Security. Commercial; see question 1.8.
o Also see question 2.7.
(1.3) Where can I get Kerberos version 4 or 5?
In the United States and Canada (*), Kerberos is available via
anonymous FTP from athena-dist.mit.edu (18.71.0.38). For specific
instructions, cd to pub/kerberos and get the file README.KRB4 (for
version 4) or README.KRB5_BETA5 (for version 5). Note that *YOU WILL
NOT BE ABLE TO RETRIEVE KERBEROS WITHOUT READING THIS FILE*.
Outside the United States, you can get Bones via anonymous ftp from
ftp.funet.fi (128.214.6.100) in pub/unix/security/kerberos. A DES
library is available from the same place. See question 1.10 for
information on Bones.
(*) Kerberos and DES can be exported to Canada. See question 2.2.
(1.4) What is the current status of version 4?
With the release of patch level 10 on December 10, 1992, MIT Kerberos
4 is now in its final form. MIT does not anticipate ever making a new
Kerberos 4 release.
Several vendors provide their own versions of Kerberos which may
contain improvements or extensions; see question 2.7.
(1.5) What is the current status of version 5?
The newest version of MIT Kerberos V5 is beta 5, released 5 May 1995.
It contains substantial (and backwards-incompatible) changes to the
krb5 API, a new admin server, improved portability, and numerous bug
fixes and improvements.
See question 1.3 for instructions on acquiring it.
(1.6) Are version 4 and version 5 compatible?
No. Versions 4 and 5 are based on completely different protocols.
The MIT Kerberos V5 distribution contains some compatibility code,
however: (a) the Kerberos server can optionally service V4 requests;
(b) there is a program to convert a V4 format Kerberos database to a
V5 format database; (c) an administration server that accepts V4
requests and operates on a V5 database is provided.
(1.7) How/why is Transarc's Kerberos different from MIT Kerberos V4?
Can they interoperate?
This is a fairly complex question, and this answer is known to be
incomplete. The issue is regularly discussed on the
info-afs-kerberos@transarc.com mailing list; send mail to the -request
list for subscriptions.
Years ago, the designers of AFS decided to implement their own
security system based on the Kerberos specification instead of using
the (then, not yet publicly available) MIT Kerberos V4. As a result,
Transarc's AFS Kerberos speaks a different protocol but also
understands the MIT Kerberos V4 protocol. They can, in principal,
talk to each other; however, there are a sufficient number of annoying
details and an insufficient number of advantages such that it may not
be practical.
The two versions use a different string-to-key function (the algorithm
that turns a password into a DES key); the AFS version uses the realm
name as part of the computation while the MIT version does not. A
program that uses a password to acquire a ticket (e.g. kinit or
login) will only work with one version, unless it is hacked up to try
both string-to-key algorithms.
The two versions also use a different method of finding Kerberos
servers. MIT Kerberos uses krb.conf and krb.realms to map hostnames
to realms and realms to Kerberos servers. AFS kaservers for a realm,
by definition, are located on the AFS database servers and can
therefore be located using /usr/vice/etc/CellServDB. This means that
a program built using the MIT Kerberos libraries will look in one
place for the information while a program built using the AFS Kerberos
libraries will look in another. You can certainly set up all three
files and use both libraries, but be sure that everything is
consistent.
The two versions have a different password changing protocol, so you
must use the correct 'kpasswd' program for the server you are talking
to. In general, AFS clients that talk directly to the kaserver use an
Rx-based protocol, instead of UDP as with MIT Kerberos, so those AFS
clients cannot talk to an MIT server.
In summary, AFS Kerberos and MIT Kerberos can interoperate once you've
acquired a ticket granting ticket, which you can do with kinit (MIT)
or klog (AFS). With a tgt, Kerberos applications such as rlogin can
talk to an MIT or AFS Kerberos server and achieve correct results.
However, it is probably best to pick one implementation and use it
exclusively
(1.8) How/why is OSF DCE Security different from MIT Kerberos V5?
Can they interoperate?
[ This answer is based on information provided by Joe Pato
(pato@apollo.hp.com). ]
DCE Security is based on Kerberos V5, and uses the same wire protocol
for AS and TGS requests; that means that standard Kerberos
applications like kinit and telnet should work using a DCE Security
Server. The implementation for the DCE Security Server, secd, was
based on an early MIT releases and has evolved independently of the
MIT code base and as a result some minor incompatibilities exist. DCE
1.2 slated for release in 1996 is planned to be fully conformant with
IETF RFC 1510 at which time any remaining protocol nits will be
resolved (interoperability problems with "vanilla" Kerberos clients
will be treated as bugs in DCE).
An MIT Kerberos V5 server cannot replace the DCE Security Server,
however. First, DCE applications communicate with secd via the DCE
RPC. Second, the DCE security model includes a Privilege Server (PS)
that fills in the authorization field of a principal's ticket with
DCE-specific data, and the DCE Security Server has a PS built in. In
order for the MIT Kerberos V5 server to support DCE clients it would
need to talk to a stand-alone PS and, although the necessary
information is available, no such PS presently exists.
The DCE does not support the Kerberos V5 API. It does, however,
provide the GSS-API with Kerberos V5 mechanism (in addition to a DCE
mechanism). Since a Kerberos V5 GSS-API mechanism is also provided in
the current MIT Kerberos V5 distribution, applications developed
against the GSS-API with this mechanism should operate with either an
MIT Kerberos server or a DCE secd. For this reason, the GSS-API
should now be considered the API of choice for Kerberos application
development.
(1.9) How/why is DEC Ultrix Kerberos different from MIT Kerberos V4?
Can they interoperate?
DEC ULTRIX contains Kerberos for a single reason, namely, to provide
authenticated name service for the ULTRIX enhanced security option.
It does not support user-level authentication in the normal manner.
DEC's version is essentially the same as (and derived from) MIT
Kerberos V4 with a few changes. The most significant change is that
the ability to perform any kind of end-to-end user data encryption has
been eliminated in order to comply with export restrictions. Minor
changes include the placement of ticket files (/var/dss/kerberos/tkt
vs. /tmp) and the principal names used by some standard Kerberos
services (e.g.: kprop vs. rcmd); there are probably other minor
changes as well.
These changes make it annoying but not impossible to use DEC ULTRIX
Kerberos in the normal way. However, there is no reason at all to do
so, because the MIT distribution supports ULTRIX directly. [This may
not be completely true. I imagine that using ULTRIX Kerberos for
enhanced security and MIT's Kerberos at the same time would cause
problems. Has anyone tried this?]
(1.10) What is Bones? What is it for?
Bones is a system that provides the Kerberos API without using
encryption and without providing any form of security whatsoever. It
is a fake that allows the use of software that expects Kerberos to be
present when it cannot be.
Why does it exist? Kerberos is a network security system which relies
on cryptographic methods for its security. Since Kerberos' encryption
system, DES, is not exportable, Kerberos itself cannot be exported or
used outside of the United States in its original form. (See question
2.2 for more information.)
As a partial solution to this problem, the Kerberos source code was
modified by the addition of #ifdef NOENCRYPTION around all calls to
DES functions. Compiling this version with the symbol NOENCRYPTION
defined results in a system that looks like Kerberos from an
application's point of view but that does not require DES libraries
(and, as a result, does not speak the real Kerberos protocol and does
not provide any security).
The final piece in this puzzle is a program called "piranha" which
takes the Kerberos sources and removes all of the calls to the
encryption routines, replacing it with the code which was under #ifdef
NOENCRYPTION, producing the system known as Bones. Bones has the
property that there is absolutely no question about whether or not it
is legal to transport its sources across national boundaries, since it
neither has any encryption routines nor any calls to encryption
routines.
#ifdef NOENCRYPTION was not documented, and it was only intended to be
used in the above manner. Someone who tries compiling Kerberos with
that #define has in some sense "voided the warranty", and will get
something which is both (a) not secure and (b) not Kerberos.
Copies of the Kerberos Bones with DES routines and calls added back in
by foreign programmers are called `eBones', and are available by
anonymous FTP from machines in Sweden, Germany, Israel, Finland,
Australia, and France (so far); check with "archie".
2. Using and Administering Kerberos
----------------------------------------------------------------------
(2.1) Can I use Kerberos for local password validation?
Yes, but only under certain circumstances and only if you are
careful.
Requests for Kerberos ticket granting tickets (tgts) (e.g. from kinit
or login) are sent in plaintext to the Kerberos server, which then
responds with credentials encrypted in the requesting principal's
secret key. The program then attempts to decrypt the data with the
supplied password and considers the authentication "successful" if the
decryption appears to yield meaningful results (such as the correct
principal name).
The problem here is that the requesting program cannot know for sure
whether the decryption succeeded or, more importantly, whether the
response actually came from the Kerberos server. An attacker could,
for example, walk up to an unattended machine and "log in" as a
non-existent user. Kerberos will eventually respond with an
appropriate error, but the attacker can arrange for another program to
deliver a fake response to login first; he then types the correct
password (which he knows because he created the fake response in the
first place) and succeeds in spoofing login.
The solution to this problem is for login to verify the tgt by using
it to acquire a service ticket with a known key and comparing the
results. Typically, this means requesting an rcmd.<hostname> ticket,
where <hostname> is the local hostname, and checking the response
against the key stored in the machine's /etc/srvtab file. If the keys
match then the original tgt must have come from Kerberos (since the
key only exists in the srvtab and the Kerberos database), and login
can allow the user to log in.
The solution works only so long as the host has a srvtab containing an
rcmd.<hostname> (or any other standard principal) entry. This is fine
for physically secure or single-user workstations, but does not work
on public workstations in which anyone could access the srvtab file.
(2.2) What is the export status of Kerberos?
[ There is a great deal of activity relating to this question and the
answer below is somewhat out of date. ]
The export status of Kerberos is constantly changing, largely because
the export regulations are unclear in general. There's an overview of
cryptography export cases in http://www.cygnus.com/~gnu/export.html .
Several companies, including OpenVision and DEC, have received export
licenses for commercial products that contain Kerberos binaries and/or
programming libraries. Contact the Kerberos vendors listed in
question 2.7 for more information.
Export of technology is controlled by both the State Department and by
the Commerce Department. The two agencies' jurisdictions don't
actually legally overlap, but nobody really knows which agency has
jurisdiction over which products. So there is a process by which you,
as a potential exporter, can ask the State Department which agency
controls your particular export. It's called a Commodity Jurisdiction
Request or CJR. There is a "CJR Kit" for helping you to file CJR's
available at ftp://ftp.cygnus.com/pub/export/cjr.kit .
The State Department has the power to regulate exports of even
publicly available (published) materials, in apparent contradiction to
the First Amendment. The Commerce Department regulations (Commerce
Control List) specifically exempts publicly available materials from
export controls (section 779.3), allowing their export under `General
License' GTDA, which requires no paperwork and is usable by everyone
except a few hundred people or companies who have abused export
controls in the past. The State Department regulation (International
Traffic in Arms Regulations, or ITAR) exempts `public domain
information' (22 CFR 120.11) but fails to define `information'. The
State Department takes the position that software is not
`information'.
Kerberos is an authentication system, and export of authentication
software and hardware is controlled by the Commerce Department.
However, the State Department has never formally said where the line
between authentication and encryption is, so they are also apparently
interested in Kerberos.
Cygnus Support filed a CJR for the Kerberos Bones software, and got
back a formal notification that it was controlled by the Commerce
Dept. We then filed a CCATS request with the Commerce Department, and
eventually found out that it is exportable to all destinations without
paperwork under the GTDA license (because it is `publicly available'
without charge on the Internet). The formal documents are in
ftp://ftp.cygnus.com/pub/export . This just confirms what we all
suspected anyway -- if you take the crypto out of Kerberos (which is
how the Bones were generated), it's exportable. The Bones are
available at ftp://athena-dist.mit.edu/pub/kerberos; look at
README.ftp for instructions.
As for the exportability of full strength Kerberos in source code,
nobody has apparently applied for this and it is a good bet that the
State Department would not grant a license for it in the current
political climate.
I believe that the best bet for threading the export maze is to define
and defend Kerberos as an authentication product, to get it past the
State Department, and then to show that it is publicly available, to
get it past the Commerce Department. To do this, you actually have to
be trying to export a publicly available version of Kerberos, though.
Canada is considered a part of the United States for export control
purposes so Kerberos can be exported to Canada without problems.
(2.3) How can I delete a principal from the database?
MIT Kerberos V4 does not include a single command to delete a Kerberos
principal. This was an intentional omission based on the assumption
that by making deletion difficult, accidents were less likely to
happen. If you want to delete a principal, do "kdb_util dump", edit
the ASCII dump with an editor, and do a "kdb_util load". Obviously,
you can write a shell script to make this more convenient.
The admin tools for AFS Kerberos, MIT Kerberos V5, and the DCE
Kerberos have a delete command.
(2.4) What are the officially assigned Kerberos port numbers?
The file src/prototypes/services.append in the MIT Kerberos
distribution contains the commonly used port assignments. This file
is not the whole story, however.
"kerberos" has officially been moved to port 88, although people will
have to listen on port 750 for some time to come, and assume
that many servers won't be converted to listen to port 88 for some
time.
"kerberos_master" and "krb_prop" have not been reserved, but they are
only used for intra-site transactions so having them reserved probably
isn't necessary. Furthermore, both of their port numbers have already
been assigned to other services, so requesting an official assignment
will force them to change.
"eklogin", "kpop", and "erlogin" have not been officially reserved,
but probably should be. Their ports are not currently assigned to
other services, so hopefully they will not have to change if an
official assignment is requested.
(2.5) Are there Kerberos versions of telnet and ftpd?
(a) TELNET. An experimental Telnet Authentication Option has been
defined, and is described in RFC1416. A separate document, RFC1411,
describes how that option is to be used with Kerberos V4, but no RFC
exists for its use with Kerberos V5. These RFC's only define how
/authentication/ is to be performed; the standard for full encryption
is still under development.
An implementation of Kerberos V4 telnet is available via anonymous ftp
from ftp.uu.net, in /networking/telnet.91.03.25.tar.Z, but it predates
both of the above-mentioned RFCs and is therefore almost certainly not
compliant with them. A Kerberos V5 telnet implementation is contained
in MIT Kerberos 5 beta 4 and subsequent releases.
(b) FTP. The IETF Common Authentication Technology (CAT) Working
Group has published the Internet Draft "FTP Security Extensions"
<draft-ietf-cat-ftpsec-NN.txt> which defines Kerberos V4 and GSS-API
authentication systems. Please note that the extensions are still in
the Draft stage and may change at any time, in incompatible ways.
A freely available version of FTP using Kerberos V4 used to exist on
thumper.bellcore.com but is no longer there [Anyone know where it
went?]. Commercial versions of secure FTP are available; see question
2.7.
(2.6) Why does rlogin print "Warning: No Kerberos tickets obtained"?
Kerberos rlogin uses a standard Kerberos exchange to prove the
identity of the user to the remote host, after which it uses the
/etc/passwd and a .klogin file to determine whether the user is
authorized to log in.
Since the user never types a password, klogind on the remote host
cannot obtain a new ticket granting ticket. The user's existing tgt
cannot be used on the remote host, because MIT Kerberos V4 tickets are
host-specific. Therefore, even though the user has logged in to the
remote host, there is no ticket granting ticket for the user available
on the remote host. The warning message is merely a reminder of this
fact.
The most recent release of MIT Kerberos V4 (patchlevel 10) contains a
system called "rkinit" that allows a user to obtain a ticket granting
ticket on a remote machine. Using this system, it is possible first
to obtain a tgt on a machine and then log into it with Kerberos
rlogin, thereby achieving a secure remote login with tickets.
Alternatively, you use Kerberos V5 which has forwardable tickets.
However, forwardable tickets do not seem to work in the current
release of MIT Kerberos V5.
(2.7) What vendors provide commercial support for Kerberos?
This answer contains contact information for Kerberos vendors. Any
vendor can submit an entry.
NOTE: The current maintainer of this list works for OpenVision
Technologies, Inc.
----------------------------------------
Vendor: CyberSAFE Corporation
formerly Open Computing Security Group (OCSG)
Product: Challenger
Contact: Sales Department
(206) 883-8721
sales@ocsg.com
Base version: MIT Kerberos 5
Last update: 4/6/95
----------------------------------------
Vendor: Cygnus Support
Product: Cygnus Network Security (CNS)
Contact: Dwayne Shirakura or Kathy Powers
+1 415 903 1400 voice
+1 415 903 0122 fax
network-security@cygnus.com
Base version: MIT Kerberos 4
Last update: 4/20/95
References:
o Product information: <http://www.cygnus.com/data/cns.html>
----------------------------------------
Vendor: Digital Equipment Corporation
Product: DECathena
Contact: Steve Omand
(508) 952-4350
omand@athena.tay.dec.com
Base version: MIT Kerberos 4
Last update: 4/11/95
References:
ftp://ftp.digital.com/pub/Digital/info/whitepaper/decathena-solution.*
ftp://ftp.digital.com/pub/Digital/info/whitepaper/secure-distributed-computing.*
http://www.digital.com/info/whitepaper/decathena-solution.abs.html
http://www.digital.com/info/whitepaper/secure-distributed-computing.abs.html
----------------------------------------
Vendor: Emulex Network Systems
Product: a line of communications servers
Contact: (714) 662-5600 ext 8065
sales@emulex.com
Base version: MIT Kerberos 4
Last update: 11/23/94
----------------------------------------
Vendor: OpenVision Technologies, Inc.
Product: OpenV*Secure
Contact: Brian Breton
(617) 374-3700 (voice)
(617) 374-3715 (fax)
brian.breton@ov.com
Base version: MIT Kerberos 5
Last update: 7/18/95
References:
o Product information: <http://www.ov.com/product/>
o Technical paper: _GSS-API Security for ONC RPC_
<ftp://ftp.cam.ov.com/pub/users/bjaspan/rpc_paper.ps>
----------------------------------------
Vendor: TGV, Inc.
101 Cooper Street
Santa Cruz, CA 95060
Product: MultiNet for OpenVMS V3.3 Rev D
Contact: (408) 457-5200
sales@tgv.com, info@tgv.com
Base version: MIT Kerberos 4
Last update: 1/20/95
----------------------------------------
Vendor: Xyplex, Inc.
295 Foster St.
Littleton, MA 01460
Product: terminal servers
Contact: (508) 952-4700
(508) 952-4702 (fax)
mkt@xyplex.com
Base version: MIT Kerberos 4 and 5
Last update: 4/17/95
(2.8) Why do I get an error message from ld when make_commands is
executed?
The make_commands program (from the file util/ss/make_commands.c,
around line 101) spawns ld as part of its normal operation. The
arguments to ld are hard-coded into the exec() call and are not
correct for all systems. To fix the problem, examine the call and
determine the correct arguments for your environment; once you know
the correct arguments, the change to the source code will be obvious.
(2.9) What is libkrb.a, and why can't ld find it?
The MIT Kerberos V5 server (krb5kdc) can operate in a V4 compatibility
mode in which it accepts and responds to standard V4 requests (see
question 1.5). In order to do so, it needs the V4 Kerberos library,
libkrb.a. That library is not part of the MIT Kerberos V5 beta 4 and
earlier distributions. It is assumed that if you want V4
compatibility you already have V4 built and installed; see question
1.3 for information on obtaining V4. To get krb5kdc to link properly,
run configure with the argument "--with-krb4=<path>" where <path> is a
directory that contains directories called "include" and "lib" that
contain the V4 include files and libraries.
Starting with the beta 5 release, the MIT Kerberos V5 distribution
contains the V4 code so it is no longer necessary to obtain and build
it separately.
(2.10) How do I set up a slave server?
This answer is written for Kerberos V5, but the same setup works for
V4 with different program names.
A slave database propagation consists of four steps:
1. Dumping the database to a transportable form. Use the command as
"kdb5_edit -R 'dump_db /krb5/slave_datatrans'".
2. Transmitting the file from the master server with kprop. Use the
command "kprop <slave>" for each slave server you want to propagate
to. This requires that the master's host principal appear in the
master's keytab (e.g.: /etc/v5srvtab).
3. Receiving the file on each slave server with kpropd. kpropd is
intended to be run out of inetd with a line such as
krb5_prop stream tcp nowait root /var/sbin/kpropd kpropd -p /var/sbin/kdb5_edit
kpropd requires that the slave server's host principal exist in its
keytab.
4. Loading the transported database with kdb5_edit load. If
everything goes well up to this point, kpropd will automatically
invoke kdb5_edit (via the path you specified in /etc/inetd.conf) and
load the database so that the slave KDC can use it.
Given this system, all you have to do is make sure that a krb5kdc gets
started on all of your slave servers and that the propagation takes
place at whatever schedule you desire. A common solution is to write
a script to perform steps 1 and 2 above that is run from cron(1).
4. Miscellaneous
----------------------------------------------------------------------
(4.1) List references for Kerberos and network security in general.
See the bibliography at the end of this document.
(4.2) Where are archives of comp.protocols.kerberos (a.k.a
kerberos@mit.edu)?
Archives are available via anonymous FTP from athena-dist.mit.edu in
the directory pub/kerberos/krb-mail. The kerberos@mit.edu
archives prensently extend up to the end of 1992. Some archives of
the kerberos protocol mailing list are also available.
----------------------------------------------------------------------
BIBLIOGRAPHY
The FTP site for a reference, when known, is listed in square brackets
following the entry. Yes, I know that these are not in Officially
Blessed Bibliography Format. Sue me.
[1] Jennifer G. Steiner, Clifford Neuman, Jeffrey I. Schiller.
"Kerberos: An Authentication Service for Open Network Systems", USENIX
Mar 1988. [athena-dist.mit.edu:pub/kerberos/doc/usenix.PS]
[2] S. P. Miller, B. C. Neuman, J. I. Schiller, and J. H. Saltzer,
"Kerberos Authentication and Authorization System", 12/21/87.
[3] R. M. Needham and M. D. Schroeder, "Using Encryption for
Authentication in Large Networks of Computers," Communications of the
ACM, Vol. 21(12), pp. 993-999 (December, 1978).
[4] V. L. Voydock and S. T. Kent, "Security Mechanisms in High-Level
Network Protocols," Computing Surveys, Vol. 15(2), ACM (June 1983).
[5] Li Gong, "A Security Risk of Depending on Synchronized Clocks",
Operating Systems Review, Vol 26, #1, pp 49--53.
[6] S.M. Bellovin and M. Merritt, "Limitations of the Kerberos
Authentication System," USENIX Jan 1991.
[research.att.com:dist/internet_security/kerblimit.usenix.ps]
[7] Refik Molva, Gene Tsudik, Els Van Herreweghen, and Stefano Zatti,
"KryptoKnight Authentication and Key Distribution System."
[jerico.usc.edu:pub/gene/kryptoknight.ps.Z]
[8] C. Neuman and J. Kohl, "The Kerberos Network Authentication
Service (V5)," RFC 1510, September 1993.
[9] B. Clifford Neuman and Theodore Ts'o, "Kerberos: An Authentication
Service for Computer Networks," IEEE Communications, 32(9), September
1994.
