From: [email protected] (Robert B. Reinhardt)
Newsgroups: comp.security.misc
Subject: (Version 3): SUMMARY PAPER: An Arch. Overview of UNIX Net. Security
Message-ID: <[email protected]>
Date: 16 Dec 1992 01:29:10 GMT
Organization: Express Access Online Communications, Greenbelt, Maryland USA
Lines: 699
This is VERSION 3 of my occassional paper on the architecture
of UNIX network security and related methods...
It is not very different from previous versions, but does
contain some additions and corrections at the request of
some of the folks who contribute these tools to the community.
I hope to complete a more complete and polished paper on this
subject in the coming months. My thanks in advance for those
who have contributed changes.
---Bob Reinhardt ([email protected])
=======================cut here================================
SUMMARY PAPER: An Architectural Overview of UNIX Network Security
(Specifically oriented toward Internet connectivity)
Version 3
By Robert B. Reinhardt, November 11, 1992
(breinhar%[email protected]) - work
([email protected]) - home
Nothing in this paper should be construed as a product
endorsement. The contents herein are the a result of light
research and some prototype implementation that I've done over the
past nine months. I don't know if this will help you or not. This
is basically just a digest of information that a lot of people
already know. This is for those of you who don't already know.
For each of the FIREWALL layers (sections) below, there is a
subsection that follows that gives a brief description of some of
the most widely used tools and techniques for implementing security
controls and their availability.
=================================================================
| | |
PUBLIC (or) NON-PRIVATE NETWORK ACCESS Y |
| O |
======================================================== U |
| | R Y
SECTION A --------------- | O
| Router | F N U
| | I E R
--------------- R T
| E W P
====================================================== W O O
| A R L
SECTION B --------------- L K I
| Dual-homed | L C
| UNIX Gateway| | A Y
--------------- | N
| | D A
======================================================== N
| E D
SECTION C --------------- Q
| Hosts on | U P
| Local Net | I E
--------------- P R
=========================================================== M S
E O
SECTION D Additional Measures to Enhance Security N N
T N
============================================================= E
L
SECTION E Functional Requirements and Security Policy |
|
================================================================= Before starting into a description of the various elements of
each of the above layers I feel I should reiterate the need for
first developing a local security policy. Each organization or
site needs to have an effective security policy. There are many
tools and techniques available to implement security controls, but
you should first conduct a thorough analysis of what your needs
are, in order to design and implement an efficient operational
environment. You need to determine what your requirements for
network services and features are, what level of security you
require, and what risks you are willing to accept. Sometimes the
benefit outweighs the risk, sometimes not. But, those decisions
differ for each organization. The "firewall" concept for creating
a security demarkation point between your local net and the
outside, as well as the various methods for enhancing security may
not be appropriate for everyone, and in some cases may not go far
enough. But I believe this a good starting point for almost anyone
with a general concern for UNIX network security.
Let me apologize right now to the authors of these tools and
designs. Since I am just giving a brief overview, I cannot do
justice to a complete description of them. To the reader let me
say that you should check the availability section and whenever
possible obtain a README or other information before making your
decisions. In many cases there is at least one paper (in most
cases probably several) that have been published that describe
these things in better detail. I'll try to list at least one
source for each.
Papers describing most if not all of these packages and
techniques can be found in the SYMPOSIUM PROCEEDINGS of the USENIX
Third UNIX Security Symposium (c) 1992 by the USENIX Association.
Some of the functionality of these tools overlap. Since you
have the source to these tools, you can modify them or customize
them to add new features.
SECTION A - Physical Access to your Network
A1. Packet filtering. Several internet protocol routers provide
the capability to filter packets. Packet filtering allows you
to program the router to make a decision whether or not
traffic can pass to or from your network based on several
criteria such as: source ip address, destination ip address,
protocol, tcp or udp port, etc.
Availability: I only have experience with CISCO routers,
however I've been told that Wellfleet and Proteon routers also
have this feature. There may be other vendors as well, but
they probably all implement it a little differently. Read:
Smoot Carl-Mitchell and John S. Quarterman, "Building Internet
Firewalls"; UnixWorld; February, 1992; pp 93-102.
NOTE: This layer of your security firewall also includes other
methods of access between networks such as CALL-BACK
MODEMS.
SECTION B - Logical Access to your Network
B1. TCP_WRAPPER. The "TCP_WRAPPER" tool provides monitoring and
control of network services. Essentially, what happens is
that you configure inetd on your dual-homed gateway to run the
TCP WRAPPER software whenever certain services (ports) are
connected to. Depending on how you configure TCP WRAPPER, it
will then LOG information about the connection and then
actually start the intended SERVER program that the connection
was intended for. Since you have the source to the tool, you
can modify it to do more depending on what your needs are.
For example, you may want TCP WRAPPER to connect the user to
a proxy service instead of the actual program, then have your
proxy software handle the transaction in whatever way your
security requirements demand.
Availability: This is available from several sources, but to
ensure that you get the most recent copy that CERT has
verified, you should use anonymous FTP to retrieve it from
cert.org in ~/pub/tools/tcp_wrappers/tcp_wrappers.*.
B2. SOCKS Library and sockd. The "sockd" and "SOCKS Library"
provide another way to implement a "tcp wrapper." It is not
intended to make the system it runs on secure, but rather to
centralize ("firewall") all external internet services. The
sockd process is started by inetd whenever a connection is
requested for certain services, and then only allows
connections from approved hosts (listed in a configuration
file). The sockd also will LOG information about the
connection. You can use the Socks Library to modify the
client software to directly utilize the sockd for outgoing
connections also, but this is described as very tedious and of
course requires you to have the source to those client
programs.
Availability: The socks package, which in addition to
including both the daemon and the library, has a pre-modified
FTP client and finger client; it is available via anonymous
FTP from s1.gov in ~/pub as socks.tar.Z. Contact the authors
for more information. David Koblas ([email protected]) or
Michelle R. Koblas ([email protected]).
B3. Kernel_Wrap for SunOS/RPC via Shared Libraries. Essentially
this is a wrapper for SunOS daemons that use RPC, such as
portmap, ypserv, ypbind, ypupdated, mountd, pwdauthd, etc. To
utilize this, you must have SunOS 4.1 or higher and must have
the capability to rebuild your shared libraries (but, you
don't need the source to your entire system). Essentially
what happens is that you modify the function calls that the
kernel uses to establish RPC connections, such as accept(),
recvfrom() and recvmsg(). Since these calls are maintained in
the shared libraries, you have access to modify them without
rewriting the kernel.
Availability: The secured C library package to implement this
is available via anonymous FTP from eecs.nwu.edu in
~/pub/securelib.
B4. SWATCH. Simple WATCHER is really two things, it is a program
used to parse through the myriad of LOG data generated by the
various security programs, in particular "syslog." But, it's
more than that. It is fully configurable with triggers
(actions), so that while it is continuously monitoring the LOG
in "real-time," it can take actions based upon certain high-
priority events that you tell it to watch for. To get full
use of this, you will need to modify your network service
daemons such as ftpd and telnetd so that enhanced logging is
added to syslog, to feed SWATCH.
Availability: The SWATCH source and documentation is
available via anonymous FTP from sierra.stanford.edu in
~/pub/sources.
B5. Controlled Access Point (CAP). This is more of a method or
protocol definition than a specific product. CAP provides a
network mechanism intended to reduce the risk of: password
guessing, probing for well-known accounts with default
passwords, trusted host rlogin, and password capture by
network snooping. It is really a design for a variation or
enhancement to the general firewall approach to connecting two
or more networks. In the paper describing this there is an
example of two local nets, one a secure segment with an
authentication service, and the other an unsecure segment.
Both communicate with each other via a CAP, while there is a
router for communication to public networks connected on the
unsecure side of the CAP. The CAP is essentially a router
with additional functionality to detect incoming connection
requests, intercept the user authentication process, and
invoke the authentication server.
Availability: Unknown. Contact the authors for more
information. J. David Thompson ([email protected]) and
Kate Arndt ([email protected]).
B6. Mail Gateway. This is more of a procedure than a software
package (although there are packages designed just to do
this). I included this to maintain continuity with what I'm
trying to illustrate in this paper. This really should be
applied to all network services that require external
connectivity (meaning any communication over non-private or
non-secure channels). In the simplest implementation of this,
you configure your router to filter packets so that all mail
traffic (SMTP protocol for example) is only allowed to and
from one host, the "Mail Gateway." Likewise, your DNS and MTA
software will need to be configured for this as well.
B7. TTY_WRAPPER. This is one of my pet ideas. I have not seen
something like this around, and I'll probably never have time
to develop it. But, essentially this would be like "TCP
WRAPPER," only it is designed specifically for serial
communications. After that, we will need a "PSEUDO-TTY
WRAPPER," but that's for another day.
B8. HSC-Gatekeeper. The HSC-Gatekeeper from Herve' Schauer
Consultants, is a complete solution to both layers A and B of
this firewall model. It consists of a thorough firewall
methodology and authentication server, providing pass-thru FTP
and TELNET services. The author (Herve Schauer) noted that
HSC-Gatekeeper was alone to be able to offer fully transparent
authentication for these services. I have not had personal
experience with HSC's products, so I cannot make a conclusive
statement about it other than to comment that the description
of it in HSC's paper "An Internet Gatekeeper" (available in
the USENIX Proceedings) depicts it (IMHO) as a very
comprehensive solution.
Availability: For more information, contact Herve Schauer via
e-mail at [email protected].
B9. AT&T INET. Since I discussed HSC's firewall solution, I
thought it only fair to mention AT&T's INET Gateway. For a
complete description of AT&T's internal solution, you should
read Bill Cheswick's paper "The Design of a Secure Internet
Gateway." For additional information, contact the author via
e-mail at [email protected]. I do not believe that AT&T
is in the business of selling this solution to anyone, but the
paper describes in good detail how it was done. It should
provide the puritan firewaller additional depth to the
problems and possible solutions to an Internet firewall
approach.
SECTION C - Physical and Logical Access to Hosts on your Network
C1. Computer Oracle and Password System (COPS). COPS is a UNIX
security status checker. Essentially what it does is check
various files and software configurations to see if they have
been compromised (edited to plant a trojan horse or back
door), and checks to see that files have the appropriate modes
and permissions set to maintain the integrity of your security
level (make sure that your file permissions don't leave
themselves wide open to attack/access).
NOTE: Many vendors of UNIX are now bundling a security
status checker with the OS, usually under the
nomenclature of a "C2" or "trusted system." You
may still find that this package has more features
than your canned package. Compare them.
Additional Comments: The current version of COPS (1.04) makes
a limited attempt to detect bugs that are posted in CERT
advisories. Also, it has an option to generate a limited
script that can correct various security problems that are
discovered. Dan also offers a quick hint that should easily
get you started using COPS. After you have unarchived the
COPS package, perform the following steps: './reconfig',
'make', and './cops -v -s . -b bit_bucket'. -- There is a lot
of README documentation included if you need more help.
Availability: COPS can be retrieved via anonymous FTP from
cert.org in ~/pub/tools/cops.
C2. Chkacct. Chkacct is a COPS for the ordinary user. This tool
is made available to the users to run, or it is run for them
once per day. It will do an integrity check on the status of
files in their own account and then mail them the results
(such as "Dear user: Your .rhosts file is unsafe"). This
package can help make your users more aware of security
controls and raise their level of participation in the
program.
Availability: Chkacct is distributed with the COPS package
(>= COPS 1.04), for additional information contact
[email protected].
C3. CRACK. Crack helps the security administrator identify weak
passwords by checking for various weaknesses and attempting to
decrypt them. If Crack can figure out your password, then you
must choose a better password. It is very likely that a
determined intruder will be able to get the password too
(using similar techniques, or the Crack program itself, since
it is publicly available).
Availability: Crack is available via anonymous FTP from
cert.org in ~/pub/tools/crack/crack_4.1-tar.Z.
C4. SHADOW. The shadow password suite of programs replaces the
normal password control mechanisms on your system to remove
the encrypted password from the publicly readable file
/etc/passwd and hides them in a place that only this program
has permission to read. It consists of optional, configurable
components, provides password aging to force users to change
their passwords once in awhile, adds enhanced syslog logging,
and can allow users to set passwords up to a length of sixteen
characters.
NOTE: Many vendors of UNIX are now bundling a shadow
password suite with the OS, usually under the
nomenclature of a "C2" or "trusted system." You
may still find that this package has more features
than your canned package. Compare them.
Availability: Shadow is available from USENET archives which
store the comp.sources.misc newsgroup. Distribution is
permitted for all non-commercial purposes. For more
information contact the author, John F. Haugh III
([email protected]).
C5. PASSWD+. Passwd+ is a proactive password checker that
replaces /bin/passwd on your system. It is rule-based and
easily configurable. It prevents users from selecting a weak
password so that programs like "CRACK" can't guess it, and it
provides enhanced syslog logging.
NOTE: Many vendors of UNIX are now bundling a proactive
password checker with the OS, usually under the
nomenclature of a "C2" or "trusted system." You
may still find that this package has more features
than your canned package. Compare them.
Availability: Passwd+ is available via anonymous FTP from
dartmouth.edu in ~/pub/passwd+tar.Z.
C6. AUDIT. Audit is a policy-driven security checker for a
heterogeneous environment. It is fully configurable so that
you can set up Audit to exactly match your site's security
policy. This program functionally does what COPS is intended
to do, but does not hard-code your policy decisions for you
the way that COPS does.
NOTE: Many vendors of UNIX are now bundling an auditing
subsystem with the OS, usually under the
nomenclature of a "C2" or "trusted system." You
may still find that this package has more features
than your canned package. Compare them. One
particular subject to note is that most (IMHO)
vendors auditing subsystems only collect and
regurgitate tons of raw data, with no guidance and
assistance for using that information. They leave
that up to you. The Audit and/or Swatch tools are
probably better.
Availability: The final version of Audit will eventually be
posted to USENET. However, the beta release will only be made
available on a limited basis, to larger, heterogeneous sites.
If your interested in participating in the beta test, send e-
mail to the auther, Bjorn Satdeva ([email protected]).
C7. MIRO. Miro is a suite of tools for specifying and checking
security contraints (like COPS and Audit), including a couple
programming languages. It is general because it is not tied
to any particular OS, and it is flexible because security
administrators express site policies via a formal
specification language. It is easy to extend or modify a
policy by simply augmenting or changing the specification of
the current policy.
Availability: Miro is the product of a large research
project, and to understand it you need more than the paragraph
I've written above. For more information about the Miro
project send e-mail to ([email protected]), there is even a
video available. The authors Ph.D thesis, as well as the
sources for the Miro tools, are available via anonymous FTP
from ftp.cs.cmu.edu. When you connect there, type "cd
/afs/cs/project/miro/ftp" and "get ftp-instructions"; this
will explain how to get the thesis and/or software.
SECTION D - Additional Security Enhancements
The tools described in sections {A...C} above, are what I
consider part of a "base" set of tools and functional requirements
for general security administration. The tools and methods
described in this section are additional measures that can be
combined with or added to your overall security program at any of
the other levels {A...C}.
D1. One-time Password ("Key Card"). Since reusable passwords can
be captured and used/reused by intruders, consider a "one-time
password" scheme. One-time passwords can be implemented using
software-only solutions or software/hardware solutions, and
there are several commercial products available. The
following is an example of what CERT uses. Each user is
assigned a "Digital Pathways" key-card (approximately $60 per
user). When you enter your PIN code, it supplies a password
that is good only one time. The only other piece to this, is
software that replace the login shell on your "firewall"
server.
Availability: The source-code for this shell is based on code
from the key card vendor and is currently not available to the
public domain via anonymous FTP. For additional information
about this, send e-mail to ([email protected]).
D2. Privacy Enhanced Mail (PEM). PEM is a RSA-based encryption
scheme that encrypts sensitive information, but more than that
it checks for message integrity and non-repudiation of origin,
so that the originator cannot deny having sent the message.
PEM is actually a protocol that is designed to allow use of
symmetric (private-key) and asymmetric (public-key)
cryptography methods. In this example, Trusted Information
Systems, Inc. (TIS) has implemented a PEM package using the
public-key technique together with the Rand MH Message
Handling System (version 6.7.2). TIS/PEM libraries can be
adapted for implementation of non-mail applications as well.
Availability: TIS/PEM is a commercially available product,
for additional information send e-mail to ([email protected]).
D3. Kerberos. Kerberos is a DES-based encryption scheme that
encrypts sensitive information, such as passwords, sent via
the network from client software to the server daemon process.
The network services will automatically make requests to the
Kerberos server for permission "tickets." You will need to
have the source to your client/server programs so that you can
use the Kerberos libraries to build new applications. Since
Kerberos tickets are cached locally in /tmp, if there is more
than one user on a given workstation, then a possibility for
a collision exists. Kerberos also relies upon the system time
to operate, therefore it should be enhanced in the future to
include a secure time server (timed is not appropriate).
There are two versions of Kerberos, one for OSF ported by HP,
and one BSD-based developed by the author.
Availability: Kerberos is distributed via anonymous FTP from
athena-dist.mit.edu in ~/pub/kerberos or ~/pub/kerberos5.
D4. Private-Key Certificates. This is not really a product, but
rather a design proposal that is an alternative method to PEM
for adding network security to applications such as mail.
Simply put, it uses the public-key style of implementation
with private-key cryptography. It can be adapted to different
types of applications and it is boilerplate so that you can
essentially plug-in any encryption algorithm. This is
designed so that public-key protocols no longer have to rely
on public-key encryption.
Availability: Unknown. For more information, contact Don
Davis, at Geer Zolot Assoc., Boston, MA (formerly of Project
Athena at MIT). His paper "Network Security via Private-Key
Certificates" better describes this techique.
D5. Multi-Level Security (MLS). After you've done everything else
(above) to make your network secure, then MLS will probably be
one of your next logical steps. That doesn't mean you have to
wait until you've done everything else before implementing
MLS, it's just (IMHO) that you would be wasting your time to
go to the Nth degree before covering the fundamentals. The
other alternative if you are just now deciding to buy your
UNIX operating system is to buy an MLS variant now, and after
you configure it to manage your security policy, go back
through layers {A...C} to see what you might add to make it
more secure in a networked environment. Many UNIX vendors are
now shipping or preparing to ship a MLS version. A couple
examples that immediately come to mind is SecureWare CMW+
(based on A/UX or SCO ODT 1.1) and AT&T USL System V-Release
4-Version 1-Enhanced Security (SVR4.1ES).
For additional information regarding MLS implementations
within the Department of Defense (DoD), contact Charles West
at (703) 696-1891, Multilevel Security Technology Insertion
Program (MLS TIP), Defense Information Systems Agency (DISA).
For additional information regarding SecureWare CMW+, contact
David Luterancik at (404) 315-6296, or send e-mail to
[email protected]. For additional information regarding AT&T USL
SVR$.1ES, contact Tom Vaden at (908) 522-6154, or send e-mail
to [email protected].
D6. File Encryption. Users should get into the habit of
encrypting sensitive files whenever they are stored in a
public place or transmitted via public communication circuits.
File encryption isn't bulletproof, but it is better than clear
text for sensitive information. The UNIX crypt utility is the
least secure of these tools, since it can be broken using
well-known decryption techniques. The UNIX des utility
(available in US only) is more secure. It has not been known
to be broken, however DoD does not sanction its use for
transmitting classified material. A new UNIX tool PGP 2.0 is
available (uses RSA encryption), however there may be
licensing issues to be concerned with.
D7. Secure Programming Methods. Programmers can assist in the
effort of security by reducing the chance that a potential
intruder can exploit a hole or bug that is coded into locally
developed software. There is probably a lot that can be said
about this, and their are probably many books on the subject
somewhere. But, here are some common recommendations. (A)
Never create a SETUID shell script. There are well-known
techniques used by intruders to gain access to a shell program
that is running as root. (B) List the complete file name,
including the full path in any system() or popen() call. (C)
Since there is no reason for users to have read access to a
SETUID file (or any exectuble for that matter), set
permissions to 4711 (SETUID) or 711 (Non-SETUID).
D8. Counterintelligence. To extend your security program to seek
out, identify, and locate intruders; you may want to modify
some of the security tools (especially those proxy service
daemons and event-driven auditors) to trace intruders back to
their source, and otherwise maintain logs of data on intrusion
attempts. This information can prove vital in taking an
offensive stance against security break-in's and can help
prosecute offenders.
D9. Other Possibilities. Depending on your requirements you might
look into specialized solutions such as Compartmented Mode
Workstations (CMW), end-to-end Data Link Encryption, and
TEMPEST. The NCSC (Rainbow Series) and ITSEC specifications
can help you define what level of need you have for security
and help lead you to additional types of solutions.
SECTION E - Security Policy
Everything discussed in sections {A...D} involve specific
things you can do, tools and techniques to implement, to address a
particular area or "hole" in security. Your SECURITY POLICY is
what ties all of that together into a cohesive and effective
SECURITY PROGRAM. There are many diverse issues to consider when
formulating your policy, which alone is one of the biggest reasons
why you must have one:
-- What are the functional requirements of your network?
-- How secure do you need to be? What needs to be protected?
-- How will you handle incident reporting and prosecution?
-- What does the law require you to do? What about privacy? Since
break-ins often occur via multiple hops on computers throughout the
US and the rest of the world, you will need to consider a variation
of federal, state, local, as well as foreign laws.
-- Make security a dedicated and deliberate effort.
-- User training and security awareness.
-- What is considered acceptable use for users? Do the users
understand what it is they are permitted to do and what it is they
are not permitted to do?
-- What is considered acceptable use for system administration
staff? Is using Crack to test passwords okay? Is giving friends
outside the organization accounts okay?
-- Maintain a working relationship with the Computer Emergency
Response Team (CERT) at Carnegie Mellon University (CMU) and your
Forum of Incident Response and Security Teams (FIRST) regional
representative "CERT" team.
-- PLUS a myriad of different issues too numerous to go into in a
summary paper.
By answering these questions you determine what packages and
methods in sections {A...D} that you want to implement, and in what
ways you want to modify or configure them. "A security policy is
a formal specification of the rules by which people are given
access to a computer and its resources." (and to extend that to
say...a network and its resources). Whatever tools you install to
help you maintain the security of your network and monitor it, they
must be configured to implement YOUR POLICY, or else they are not
doing the whole job that needs to be done. Therefore, you must
first have a POLICY.
For additional help in the area of policy development, contact
[email protected], and they can probably lead you to useful
documentation on the subject and guide you to your FIRST regional
CERT team representative. A good starting point is Request For
Comments (RFC) 1244 "Site Security Handbook" (96 pages), which is
available via anonymous FTP from numerous RFC archive sites (for
example: nic.ddn.mil). SUMMARY OF AVAILABILITY
Section Name Availability
A1 Router Cisco, Wellfleet, Proteon
B1 Tcp_wrapper cert.org:/pub/tools/tcp_wrappers
B2 Socks s1.gov:/pub/socks.tar.Z
B3 Kernel_wrap eecs.nwu.edu:/pub/securelib
B4 Swatch sierra.stanford.edu:/pub/sources
B5 CAP e-mail to [email protected]
B6 Mail Gateway NOT APPLICABLE
B7 Tty_wrapper NOT APPLICABLE
B8 HSC-Gatekeeper e-mail to [email protected]
B9 AT&T INET e-mail to [email protected]
C1 COPS cert.org:/pub/tools/cops
C2 Chkacct cc.perdue.edu:/pub/chkacctv1.1.tar.Z
C3 Crack cert.org:/pub/tools/crack/crack_4.1-tar.Z
C4 Shadow comp.sources.misc ([email protected]).
C5 Passwd+ dartmouth.edu:/pub/passwd+tar.Z
C6 Audit e-mail to [email protected]
C7 Miro e-mail to [email protected]
D1 Key-card e-mail to [email protected]
D2 TIS/PEM e-mail to [email protected]
D3 Kerberos athena-dist.mit.edu:/pub/kerberos5
D4 Private-key contact Don Davis, at Geer Zolot Assoc.
D5 MLS contact your UNIX vendor
D6 File encrypt contact your UNIX vendor
D7 Programming NOT APPLICABLE
D8 Counter-Intel NOT APPLICABLE
D9 Other Poss. research and contact various vendors
E* Policy RFC 1244 and [email protected]
Additional Sources of Information
Subscribe to the following mailing lists:
[email protected]
[email protected]
[email protected]
Read the following USENET newsgroups:
comp.security.announce (echos the CERT advisory mailing list)
comp.security.misc
alt.security (frequently dissolves into "flame wars")
comp.risks
comp.virus (almost exclusively for discussing PC and MAC viruses)
Copy files from the CERT Usenet Clipping Archive via anonymous FTP
from cert.org
CERT Contact Information:
Emergencies: +1 412 268-7090
FAX: +1 412 268-6989
E-mail: [email protected]
U.S. Mail: CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
4500 Fifth Avenue
Pittsburgh, PA 15213-3890, USA
USENIX Papers are available directly from USENIX:
The USENIX Association
2560 Ninth Street, Suite 215
Berkeley, CA 94710, USA
READ: The SYMPOSIUM PROCEEDINGS of the USENIX Third UNIX Security
Symposium (September 14-16, 1992). It is 330+ pages, containing
papers describing in better detail a lot of the packages and
security techniques I briefly described in this paper.
------------------------SUMMARY OF CHANGES-------------------------
Version 1 was distributed on September 19, 1992
Version 2 was distributed on October 8, 1992
Version 3 was distributed on November 11, 1992
(V3) Paragraph B2 (Socks) - Changes to e-mail address submitted by
Ed DeHart of CERT. Changes to availability submitted by the
authors, David and Michelle Koblas, the package is available from
s1.gov. (V3) Paragraph B8 (HSC-Gatekeeper) - Added this at the
suggestion of the author, Herve Schauer. (V3) Paragraph B9 (AT&T
INET) - Added this to show a contrast to new paragraph B8. (V2)
Paragraph C1 (COPS) - Additional Comments and Hints submitted by
Dan Farmer, the author of COPS. (V2) Paragraph C2 (Chkacct) -
Correction to availability, the package is distributed with COPS
(versions >= 1.04). (V2) Paragraph D1 (KeyCard) - Correction to
availability, source code is not in public domain, submitted by Jim
Ellis at CERT. (V3) Paragraph D5 (MLS) - Changed to take a more
progressive stance toward MLS in current operating environments.
(V3) Additional information - Added address for the new Firewalls
mailing list.
------------------------NOTICE---DISCLAIMER------------------------
The contents of this paper do not necessarily reflect the opinions
of my employer or anyone else that I know. Nothing in this paper
should be construed as a product endorsement. No warranty is
expressed or implied. Any comments? Please send me e-mail.
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------------------------NOTICE---COPYRIGHT-------------------------
(c) Copyright 1992, Robert B. Reinhardt. This paper is freely
distributable as long as the paper is not modified in any way,
includes this notice, and is provided without guarantee or warranty
expressed or implied. E-mail comments to [email protected]
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