Security Doc Sought

From: xtasc@levels.unisa.edu.au
Newsgroups: comp.security.misc
Subject: [summary] Security Doc Sought Part 1/2
Message-ID: <19595.2b57e646@levels.unisa.edu.au>
Date: 16 Jan 93 10:41:10 +1030
Organization: University of South Australia
Lines: 700

Some time ago I posted a request for information about security related
documentation. Well after much gleaning of ftp sites, I've managed to
get more than enough to read for the next month or so, as well as some
very good pointers to software and a book on the subject.

My apologies if anything in this posting has already been posted, or is
widely known (I'm only new to reading the relevant groups). Similarly my
apologies if any respondee's didnt want their responses posted, but I
did say I'd summarize, and didnt see any notes to the contrary.

Its not that well formatted, but all the responses follow (minus the
people who requested this summary).

A word of warning :-) choose a time when no-one else needs your local
laserprinter .... Theres a lot there, and I managed to fray some tempers ....

Most importantly, many thanks to those who responded. I see no point in
reinventing the wheel, and now after the post I have a number of wheels
to choose from ... thanks again !

Regards .... Rob

Rob Mayfield
Senior Technical Analyst - MIS - Australian Submarine Corporation P/L.
GPO Box 2472, Adelaide S.A. 5001 Ph +61 8 348 7000 Fx +61 8 348 7001
Telex AA186451     Email mayfield@itd.adelaide.edu.au

PS: Ive posted direct followups to those who requested such, sorry if I
missed any.

/*****************/


From: IN%"breinhar@access.digex.com"  "Robert B. Reinhardt" 10-JAN-1993 12:33:51.44
Here is something that might be useful to you.

==========================cut here=============================
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 (breinhar@access.digex.com)
=======================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%srg@uunet.uu.net) - work
               (breinhar@access.digex.com) - 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 (koblas@netcom.com) or
     Michelle R. Koblas (mkoblas@nas.nasa.gov).

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 (thompsond@orvb.saic.com) and
     Kate Arndt (karndt@mitre.org).

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 Herve.Schauer@hsc-sec.fr.

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 ches@research.att.com.  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
     shabby@mentor.cs.purdue.edu.

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
     (jfh@rpp386.cactus.org).

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 (bjorn@sysadmin.com).

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 (miro@cs.cmu.edu), 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 (cert@cert.org).

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 (pem-info@tis.com).

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
     info@sware.com.  For additional information regarding AT&T USL
     SVR$.1ES, contact Tom Vaden at (908) 522-6154, or send e-mail
     to fate@usl.com.
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
cert@cert.org, 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 thompsond@orvb.saic.com
B6        Mail Gateway   NOT APPLICABLE
B7        Tty_wrapper    NOT APPLICABLE
B8        HSC-Gatekeeper e-mail to Herve.Schauer@hsc-sec.fr
B9        AT&T INET      e-mail to ches@research.att.com
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 (jfh@rpp386.cactus.org).
C5        Passwd+        dartmouth.edu:/pub/passwd+tar.Z
C6        Audit          e-mail to bjorn@sysadmin.com
C7        Miro           e-mail to miro@cs.cmu.edu
D1        Key-card       e-mail to cert@cert.org
D2        TIS/PEM        e-mail to pem-info@tis.com
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 cert@cert.org

                Additional Sources of Information

Subscribe to the following mailing lists:

cert-advisory-request@cert.org
cert-tools-request@cert.org
firewalls@greatcircle.com

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:        cert@cert.org

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.

From: xtasc@levels.unisa.edu.au
Newsgroups: comp.security.misc
Subject: [summary] Security Doc Sought Part 2/2
Message-ID: <19596.2b57e72d@levels.unisa.edu.au>
Date: 16 Jan 93 10:45:01 +1030
Organization: University of South Australia
Lines: 629

Part 2 .... contd

------------------------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.
-------------------------------------------------------------------

------------------------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 breinhar@access.digex.com
-------------------------------------------------------------------

/*****************/


From: IN%"pcl@neon.athena.ox.ac.uk"  7-JAN-1993 23:05:04.74

black.ox.ac.uk:/DOCS/security/*
black.ox.ac.uk:/src/security/*

black is 129.67.1.165

Paul

/*****************/


From: IN%"Marten.Sahlen@eua.ericsson.se"  7-JAN-1993 18:42:41.95

Hi!
I know of a few places that might be of interest. The best source to start
with is probably the NIST Computer Security FTP Archive at csrc.ncsl.nist.gov.
It contains a wide variety of articles, info, software etc. in the security
field.

Another place is ariel.unm.edu in the /ethics directory, which contain a lot
of examples on how security policies can be designed.

Thirdly, for network security and particulary the Kerberos system, try
aeneas.mit.edu under pub/Kerberos/doc.

I would be very interested in a summary of all the sources you get pointers
to.

Regards...

--
>>>>-----------------Marten Sahlen  etxsahm@eua.ericsson.se-----------------<<<<
>>>-----Ellemtel Telecom Systems Lab, Box 1505, S-125 25 Alvsjo, Sweden------<<<

/*****************/


From: IN%"SPG@NEREID.SUNQUEST.COM"  7-JAN-1993 16:36:19.73

Rob,

I would really _really_ appreciate a summary/follow-up on anything that you
find.

In regards to PD VMS security stuff, you might try anonymous ftp to
spcvxa.spc.edu in the [.Madison] and [.Macro32] directories
and
ACF1.NYU.EDU in various places.

--
Steve (SPG6) spg@sunquest.com

/*****************/


From: IN%"spaf@cs.purdue.edu"  7-JAN-1993 15:42:37.46
To: IN%"xtasc@levels.unisa.edu.au"
CC:
Subj: RE: Security related Documentation sought.


I don't know if I responded to you already or not.  If I did, my
apologies.

You might try taking a look at my book (for Unix and for networks,
passwords, etc).  Canned blurb follows.

Cheers,
--spaf

"Practical Unix Security"
by Simson Garfinkel and Eugene Spafford
O'Reilly & Associates (the Nutshell Handbook people).
500 pages, 1991, $29.95.
ISBN 0-937175-72-2

Quotes from reviewers:

Cliff Stoll:
   Worried about who's in your Unix system? 
   Losing sleep because someone might be messing with your computer? 
   Having headaches from obscure computer manuals?

   Then _Practical_Unix_Security_ is for you. 

   This handy book tells you where the holes are and how to cork 'em up. 
   Moreover, you'll learn about how Unix security really works.
   Spafford and Garfinkel show you how to tighten up your Unix system
   without pain.  No secrets here -- just solid computing advice.

   Buy this book and save on aspirin.

Tom Christiansen, Convex Computer Corp:
   This book is the first I've seen that actually seemed to
   address the many security issues that I keep around on
   my own little list, and it did so well.

Paul Clark, Trusted Information Systems:
   The book could easily become a standard desktop reference for
   anyone involved in system administration. In general, its
   comprehensive treatment of Unix security issues
   will enlighten anyone with an interest in the topic.

Matt Bishop, Dartmouth
   ...I liked the book; it covers a lot of material not
   normally covered and provides practical instructions on how to do
   things.  This will be very useful for practitioners...This book is
   far superior to any other I have seen on UNIX security.

Laurie Sefton, Apple:
   Finally there is a UNIX security book that covers the BSD world as
   well as the SYS V version...The other aspect of UNIX security books
   that has been sorely lacking was the "rest of UNIX" security.  All the
   other books had a very thin overview of "down and dirty" security, as
   if they were afraid of giving out too much information...As soon as
   this is out, I'm ordering copies for all my people, and extra copies
   for the library at Apple.


Orders:  800-998-9938 (US & Canada)
707-829-0515 (Europe)
nuts@ora.com (e-mail)


Table of Contents:

Preface 
    Scope of this Book
    Which UNIX System?
    Conventions Used in this Book
    Acknowledgments
    Three Final Notes

Chapter 1  Introduction 
    What's Computer Security?
    What's an Operating System?
    History of UNIX
    Security and UNIX
    Security and Networks
    Types of Security
        Risk Assessment
        Assessing Your Risk
        Reacting to an Emergency
        Other Important Steps
    The Problem with Security Through Obscurity
    The First Step

Chapter 2  Users and Passwords 
    Usernames
        The /etc/passwd File
        The /etc/passwd File and Network Databases
    Passwords
        Why Use Passwords?
        Entering Your Password
        Changing Your Password
        Checking Out Your New Password
    UNIX'S Encrypted Password System
        The crypt() Algorithm
        What is Salt?
    The Care and Feeding of Passwords
    Bad Passwords:  Open Doors
    Good Passwords:  Locked Doors
        Passwords on Multiple Machines
        Writing Down Passwords
    Administrative Techniques
        Assigning Passwords to Users
        Password Generators
        Shadow Password Files
        Password Aging and Expiration
        Algorithm Changes
        Preventing Direct Logins to Accounts
        Account Names Revisited
    Summary

Chapter 3  Users, Groups, and the Superuser 
    Users and Groups
        User Identifiers (UIDs)
        Groups and Group Identifiers (GIDs)
    Special Users
        The Superuser
        Other Special Users
        Impact of the /etc/passwd and /etc/group Files on Security
    The su(1) Command:  Changing Who You Are
        Becoming the Superuser
        Restricting su
        The Bad su Log
        Other Uses of su
        Summary

Chapter 4  The UNIX File System 
    Files
        Using the ls(1) command
        Understanding File Permissions
        File Permissions in Detail
    Using File Permissions
        chmod:  Changing a File's Permissions
        Setting a File's Permissions
        Calculating Octal File Permissions
        Using Octal File Permissions
    The umask
        The umask command
        Common umask Values
    Using Directory Permissions
    SUID
        SUID, SGID, and Sticky Bits
        Problems With SUID
        Finding All of the SUID and SGID Files
        Turning off SUID and SGID in Mounted File Systems
        SGID and Sticky Bits on Directories
(Berkeley UNIX and Sun OS Only)
        SGID Bit on Files (System V UNIX only)
    chown:  Changing a File's Owner
    chgrp:  Changing a File's Group

Chapter 5  Defending Your Accounts 
    Dangerous Accounts
        Accounts Without Passwords
        Default Accounts
        Accounts That Run a Single Command
        Open Accounts
    Group Accounts
    Dormant Accounts
        Changing an Account's Password
        Changing the Account's Login Shell
        Finding Dormant Accounts
    Protecting the Root Account Under Berkeley UNIX
        Secure Terminals
        The wheel Group

Chapter 6  Securing Your Data 
    File Backups
        Why Make Backups?
        What Should You Back up?
        Kinds of Backups
        How Long Should You Keep a Backup?
        Security for Backups
    Database Backups and Daily Checking
    Integrity Checking and Checklists
        Checklists
        File Protection Modes
        Read-Only Disks
        Comparison Copies
        Checklists
        Signatures

Chapter 7  The UNIX Log Files 
    The /usr/adm/lastlog File
    The /etc/utmp and /usr/adm/wtmp Files
        Last Program
        Pruning the wtmp File
    The /usr/adm/acct File
    The Berkeley System Log (syslog) Facility
        The syslog.conf Configuration File
        Where To Log

Chapter 8  Protecting Against Programmed Threats 
    Programmed Threats:  Definitions
        Back Doors and Trap Doors
        Logic Bombs
        Viruses
        Worms
        Trojan Horses
        Bacteria and Rabbits
    Damage
    Authors
    Entry
    Protecting Yourself
        Shell Features
        Startup File Attacks
        Abusing Automatic Mechanisms
        Unexpected Interactions
    Protecting Your System
        File Protections
        SUID and SGID Programs
        Notes on Writing a SUID Program
        SUID Shell Scripts

Chapter 9  Modems 
    Theory of Operation
    Serial Interfaces
        The RS-232 Serial Protocol
        Originate and Answer
        Modems and Security
    Modems and UNIX
        Hooking Up a Modem to Your Computer
        Setting Up the UNIX Device
        Checking Your Modem
        Physical Protection
    Additional Security for Modems

Chapter 10  UUCP 
    About UUCP
        The uucp Command
        The uux Command
        The mail Command
        How The uucp Commands Work
    Versions of UUCP
    UUCP and Security
        Assigning Additional UUCP Logins
        Establishing UUCP Passwords
        Security of the L.sys and Systems Files
    Security in Version 2 UUCP
        USERFILE:  Providing Remote File Access
        A USERFILE Example
        L.cmds:  Providing Remote Command Execution
    Security in BNU UUCP
        The Permissions File
        Permissions Commands
        uucheck(1):  Checking Your Permissions File
    Additional Security Concerns
        Mail Forwarding for UUCP
        Automatic Execution of Cleanup Scripts
    Early Security Problems with UUCP
        Summary

Chapter 11  Networks and Security 
    The Internet
    Internet Addresses
        The /etc/hosts File
        Network Hostname Service
    Clients and Servers
        TCP/IP
        UDP/IP
        UNIX Network Servers
        The /etc/services File
        Starting the Servers
        The /etc/inetd Program
    Network Services
        TELNET
        rlogin and rsh
        rexec
        finger
        Electronic Mail
        FTP
        TFTP
        The X Window System
    Security Implications of Network Services
        Monitoring Your Network with netstat
        Summary

Chapter 12  Sun's NFS 
    NIS
        Netgroups
        Setting up Netgroups
    NFS
        How NFS Works
        The /etc/exports File
        The showmount Command
        Authentication and NFS
    Improving Basic NFS Security
        Limiting Exported File Systems
        Limit Exported Machines
        Use Root Ownership
        Export Read-only
        Do Not Export Server Executables
        The fsirand Program
        Summary:  Security Implications of NFS

Chapter 13  Kerberos and Secure RPC 
    The Problem
        What's Wrong with LANs?
        Minimizing the Problems
    MIT's Kerberos
        What's It Like to Use Kerberos?
        How to Install Kerberos
        What's Wrong with Kerberos?
    Sun Microsystems' Secure RPC
        How Secure RPC Works
        What's It Like to Use Secure NFS?
        How to Install Secure RPC
        What's Wrong with Secure RPC?

Chapter 14  Firewall Machines 
    What's a Firewall?
        Internal Firewalls
        External Firewalls
    Setting Up a Firewall
        The Choke
        Choosing the Choke's Protocols
    Setting up the Gate
        Name Service
        Electronic Mail
        Netnews
        FTP
        Other Services
    An Alternate Method
    Special Considerations

Chapter 15  Discovering a Break-in 
    Prelude
    Discovering an Intruder
        Catching One in the Act
        What to Do When You Catch Somebody
        Tracing a Connection
        Getting Rid of the Intruder
    The Log Files:  Discovering an Intruder's Tracks
    Cleaning Up After the Intruder
        New Accounts
    An Example
    A Last Note:  Never Trust Anything Except Hard Copy

Chapter 16  Denial of Service Attacks and Solutions 
    Destruction Attacks
    Overload Attacks
        Process Overload Attacks
        Disk Attacks
        Swap Space Attacks
        Soft Process Limits:  Preventing Accidental
Denial of Service
    Network Denial of Service Attacks
        Service Overloading
        Message Flooding
        Signal Grounding

Chapter 17  Computer Security and the U.S. Law 
    Legal Options After a Break-in
    Criminal Prosecution
        The Local Option
        Federal Jurisdiction
        Federal Computer Crime Laws
        Hazards of Criminal Prosecution
        If You or One of Your Employees is a
Target of an Investigation
        Other Tips
    Civil Actions
    Privacy and The Electronic Communications Privacy Act

Chapter 18  Encryption 
    Who Needs Encryption?
    Cryptographic Strength
    Types of Encryption Systems
    ROT13
    crypt
        Enigma
        UNIX crypt
        Ways of Improving the Security of crypt
        Example
    The Data Encryption Standard (DES)
        DES Modes
        Use and Export of DES
        DES Strength
        Sun's des command
    RSA and Public Key Cryptography
        How RSA Works
        An RSA Example
        Strength of RSA
    Proprietary Encryption Systems
    Protect Your Key!

Chapter 19  Physical Security 
    Protecting Computer Hardware
        The Environment
        Accidents
        Physical Access
        Vandalism
        Acts of War and Terrorism
        Theft
        Related Concerns
    Protecting Data
        Eavesdropping
        Backups
        Local Storage
        Unattended Terminals

Appendix A  UNIX Security Checklist

Appendix B  Important Files 
    System Files
    Important Files in your Home Directory
    SUID Files in Berkeley UNIX
    SGID Files in Berkeley UNIX
    SUID Files in System V R3.2 UNIX
    SGID Files in System V UNIX

Appendix C  UNIX Processes 
    Processes
        Processes and Programs
        The ps Command
        Process Properties
    Creating Processes
    Signals
    The kill Command
    Starting Up UNIX and Logging In
        Process #1: /etc/init
        Letting Users Log In
        Running the User's Shell

Appendix D  How Kerberos Works 
    Kerberos's Parts
    Using Kerberos
    Using a Service

Appendix E  Other Sources 
    References
       General Computer Security
       UNIX Security
       Computer Viruses and Programmed Threats
       Computer Crime and Law
       Understanding the Computer Security 'Culture'
       Understanding and Using Networks
       Using and Programming UNIX
       Security Products and Services Information
       Miscellaneous References
    Organizations
        Association for Computing Machinery (ACM)
        IEEE Computer Society
        ASIS
        Computer Security Institute (CSI)
        NIST
        Computer Emergency Response Team (CERT)
        DOE's Computer Incident Advisory Capability (CIAC)
    Software Resources
        Getting Kerberos
        Getting COPS


/*****************/


From: rob@panache.b17a.ingr.com (Rob Mount)

Try the book:

  Practical UNIX Security
  Simson Garfinkel and Gene Spafford
  O'Reilly & Associates, Inc. 1991

  which is available from:

  Addison-Wesley Publishers, Pty. Ltd.
  6 Byfield Street
  North Ryde, N.S.W. 2113
  Australia
  Voice: 61-2-888-2733  Fax: 61-2-888-9404

  This book contains a wealth of information and is destined to become
  your primary source for UNIX security.  Much of the information is
  general enough to be applicable elsewhere though.  Also has an excellent
  bibliography!

The book mentioned above contains references to the COPS security package
for UNIX, including information on how to get it via ftp.

Regards,

Rob Mount, Intergraph Corporation   +-----------------------------------+
Domain: rob@panache.b17a.ingr.com   | I hate quotations.  Tell me what  |
UUCP:   ...!ingr!b17a!panache!rob   | you know.  -- Ralph Waldo Emerson |
Voice:  (205) 730-1518 FAX: -7296   +-----------------------------------+

/*****************/



From: Bob Dowling <rjd4@cus.cam.ac.uk>

I keep a few useful documents that I've found searching through the net
available for anonymous FTP. Take a look in /pub/security/ on ftp.cus.cam.ac.uk
for the documents I have there.
--------
Bob Dowling:                    UNIX Support,
                                University of Cambridge Computing Service,
rjd4@cus.cam.ac.uk              New Museums Site, Pembroke Street,
+44 223 334728                  Cambridge, UK.  CB2 3QG.

/*****************/


From: XARJP@Levels.UniSA.Edu.Au

Here's some suggestions:
  look in news.answers for comp.security FAQ

  for unix - get "cops" and "crack" and shadow passwd suites from
             an archive server (archie.au will point you in the right
             direction)

  for NIST documents, use anonymous ftp to "csrc.ncsl.nist.gov" and
             gat the indices, ls-rl's etc etc

Good luck - be paranoid but happy.

Regards, Rob Potter (Secure Data Systems Pty Ltd (08) 271 6612 if you need help)



The End ....

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