General Information

Instructor Matt Bishop, 3059 Engineering Unit II; email:
Office hours: MWF1:10-2:00PM, by appointment or chance
Teaching Assistant Eugene Fodor, 059 Engineering Unit II; email:
Office hours: to be arranged
Lectures MWF 2:10 - 3:00PM in Haring Hall, Room 1204
Discussion Section W 3:10 - 4:00PM in Olson Hall, Room 147
This is required as new material as well as review material will be presented. Material presented in this section is important and will be covered on the exams.
introduce principles, mechanisms, and implementations of computer security; learn how attacks work, how to defend against them, and how to design systems to withstand such attacks
Some goals we hope you achieve:
  1. learn about security in the UNIX system and programming environments;
  2. understand the strengths, and weaknesses of cryptography as a tool of security
  3. learn how access to systems, resources, and data can be controlled;
  4. learn the basics of writing security-related programs;
  5. learn about security in networks;
  6. learn how to analyze a system for vulnerabilities, and how to ameliorate those vulnerabilities.
Text There is no required text for this course. The recommended texts are
  • E. Amoroso, Fundamentals of Computer Security Technology, Prentice Hall, Englewood Cliffs, NJ. 1994.
  • S. Garfinkel and E. Spafford, Practical UNIX & Internet Security, Second Edition, O'Reilly and Associates, Inc., Sebastopol, CA. 1996.
Computers All registered students have been given an account on the computer science instructional machines in the basement. See the handout CSIF Accounts for more information. Change your password as soon as you can; if it is not changed within a week, your account will be disabled and you will have to see a system programmer to have it reset.
Course Handouts All course handouts, programs, and samples will be available in the directory ~cs153 on any of the CSIF DECStations, and on the WWW. The URL for the class is
Information about this class, homework assignments, and so forth, will be posted to the newsgroup ucd.class.ecs153. Read this newsgroup daily! You are responsible for everything posted to this newsgroup. Please do not post to this newsgroup; we'll use it to put out important information.
If you want to post things about the class, please use the discussion newsgroup ucd.class.ecs153.d. Discussing something in this group is perfectly fair!
Homework Homework is due at the beginning of class on the date stated on the homework. See the handout All About Homework for more information.
Extra Credit Extra credit in this course will be tallied separately from regular scores. If you end up on a borderline between two grades at the end of the course, extra credit will count in your favor. However, failure to do extra credit will never be counted against you, because grades are assigned on the basis of regular scores. You should do extra credit if you find it interesting and think that it might teach you something. However, it is not wise to skimp on the regular assignment in order to do extra credit.
Exams Midterm - Monday, February 10, 1997, in class
Final examination - Tuesday, March 18, 8:00-10:00AM

These are open book/open notes exams. No early or late exam will be given; if you miss an exam for medical reasons (you must document this; no other excuses are acceptable), you may be allowed or required to take a make-up exam, or the other parts of the course will be counted proportionally more (the choice is the instructor's). In particular, forgetting the time or place of an exam is not an excuse for missing it!

30% Homework20% Midterm exam
30% Term Project20% Final exam
Academic Integrity Please see pages 148-149 of the Winter 1997 Class Schedule and Room Directory for a general discussion of this. In particular, for this course:
  • All work submitted for credit must be your own. You may discuss your assignments with classmates, with instructors, or with teaching assistants or readers in the course to get ideas or a critique of your ideas, but the ideas and words you submit must be your own. Unless explicitly stated otherwise in the assignment, collaboration is considered cheating and will be dealt with accordingly.
  • For written homework, you must write up your own solutions and may neither read nor copy another student's solutions.
  • For programs, you must create and type in your own code and document it yourself. Note that you are free to seek help while debugging a program once it is written.

A good analogy between appropriate discussion and inappropriate collaboration is the following: you and a fellow student work for competing software companies developing different products to meet a given specification. You and your competitor might choose to discuss product specifications and general techniques employed in your products, but you certainly would not discuss or exchange proprietary information revealing details of your products. Ask the instructor or a teaching assistant for clarification beforehand if the above rules are not clear.


Here is an outline of what we will be covering.

  1. What is computer security: notion of an informal policy, formalization of policy, governmental vs. commercial, etc.; ethics and law
  2. Encryption: classical, public-key; implementation, problems; the UNIX file encryption mechanism and its cryptanalysis; the DES
  3. Authentication: model of authentication systems, traditional passwords, challenge/response, one-time passwords; cryptographic protocols, simple cryptosystems; the standard UNIX authentication system, its limits and alternate forms; implementations of other mechanisms
  4. Access control: controlling access to resources, access matrix model, HRU result, ACLs and capability lists; mandatory controls, ORCON controls; variants; UNIX scheme and augmentations
  5. Integrity: cryptographic checksums, malicious logic, viruses, Trojan horses; defenses, prevention; UNIX integrity checking tools and how they work; malicious logic and UNIX
  6. Security-oriented programming: design principles, focusing on common problems; gates vs. privileged servers; environment, exception handling; writing secure servers and secure setuid/setgid programs in the UNIX environment
  7. Networks and security: Internet Security Architecture, analysis of Internet protocols, design and implementation considerations; firewalls; UNIX networking and security
  8. Penetration analysis: common types of flaws, examples, flaw hypothesis methodology, analysis of programs and systems; UNIX instances of problems, flaws, and how to fix them
  9. Secure systems: types, models, design, changes to non-secure systems; comparative analysis

CSIF Accounts

The staff has created instructional accounts for all students who are registered for Computer Science courses in Winter Quarter 1997 but who did not already have an account on the Computer Science instructional machines. Find the list of new accounts downstairs. The list is alphabetized by last name. Look down the list until you find your name. In the "Account Name" column is the name of the computer account that has been assigned to you. It's also called a "login name". (It does not apply to IT [Information Technology, essentially the campus computer center] accounts, to ACS [Academic Computing Services, a unit of the College of Engineering] accounts, or to ECE [Electrical and Computer Engineering] accounts. It applies only to your Computer Science account.) The Computer Science instructional machines are in the basement of the east wing of building Engineering II.

If your name does not appear on this list, either you already have an account on the Computer Science instructional machines, or your name was not included on the class lists that we got from the registrar. The latter may occur if you have added a Computer Science class, as opposed to pre-registering for one. In this case, your account will be added the day after we receive notification from the registrar that you have added the class. Your account name and login name will then be posted as described above.

An initial password has been assigned to your account: the last 8 numeric digits of your student id number. (The student id number has 9 numeric digits in it, so omit the first one, and omit the hyphens to form your initial password.) Because your student id number is something that other people can probably find out about you, a password based on your student id number is not very secure. That is, someone other than you could login to your account, including hackers. Since you are the only one who is authorized to use your account, it is imperative that you change your password as soon as possible. Use the yppasswd(1) command when logged in to the Computer Science instructional machines to do so. If you have not changed your password by 5pm on the Monday of the second week of classes, logins on your account will be disabled. To get logins on your account re-enabled, stop by room 047, whee the student assistants are located. You will need to bring your student id card.

Disk quotas have been installed. You may store no more than 10 Mbytes of data in your home directory.

If you have any questions, send mail to "support".


All programs and commands written for homework must work on the DEC, HP, and SGI systems unless specifically stated otherwise in the assignment, since security problems often arise when porting software.

dec1, ..., dec62 Digital Equipment Corp. workstations running Ultrix
sgi1, ..., sgi23 Silicon Graphics, Inc. workstations running IRIX
hp2, ..., hp25 Hewlett-Packard workstations running HP/UX

You can log on to the instructional systems in two ways: directly into a workstation in the basement of Engineering Unit II, or through a network login program (rlogin(1) or telnet(1)) on the UC Davis network.

All About Homework

The homework will consist of both programming exercises and written questions. This handout describes some general thoughts and techniques for doing homework, as well as what is required, how to submit it, how late homeworks are handled, and other administrative matters.

Turning In Homework

All homework is due at the beginning of the class on the due date, unless noted otherwise on the assignment. (This way, you have no incentive to skip the class while finishing your homework at the last minute!) These will be graded and returned to you as quickly as possible; we'll try for two class periods, but can't guarantee it (especially since we have no grader so far ).

For written homework, please turn in either an ASCII or a PostScript version of your answers (you can use any text processor you like to generate these). If you submit PostScript, please be sure the file will print on our department printers (use ghostscript or gs to check this; if they display it properly, it should be okay). If your file is a postscript file, put the extension ".ps" on it; if it is an ASCII file, put the extension ".txt" on it. For programs, turn in the source code and any related information (such as man pages and README files).

For programs, you are free to use any programming language that is available on the CSIF and that the ECS 153 graders can get to; so C or assembly is acceptable, any of the languages in the programming languages class is acceptable (assuming compilers and interpreters are available in the CSIF), and if you can write your programs in such a way that troff(1) or latex(1) can execute them, that's fine too. (Yes, someone once wrote a BASIC interpreter as a set of troff macros. It was very slow, but it worked.) But use lots of comments!

Turn in both your written exercises and programs electronically. Suppose your program for homework 3 is in the files and prog.c Then, to turn it in, say

handin cs153r hw3 prog.c
This program will submit your files to the ECS 153 grader. (A manual page for the handin program is attached.)

Doing Written Exercises

When you are asked to analyze something, or explain something, please be complete, and show your work (including any commands you give, and their output, to show how you did the problem); otherwise, even if you get the right answer, you will get ZERO points. Think your answer through and do a rough draft before you begin to write or type. Write clearly and cogently. If the question asks for an opinion, state your opinion clearly, justify it, and do not ramble. Answers which start, "My opinion is yes" and conclude with "so on the other hand I guess it could be no equally well" will not get much credit.

Doing Programming Exercises

We cannot overemphasize the importance of taking time to design your program, or outline and draft your answer, thoroughly. More programming problems arise from improper design than anything else, and the few hours you spend on design will be amply repaid by shorter coding and debugging phases. So do think the design and interfaces through, and, as always,, try to find the simplest way to do the assignment (within the limits given in the assignment, of course)!

Do not leave assignments for the last minute. The assignments are non-trivial and will require significant design time before you start programming and debugging. When we decide on the due dates, we assume you will spend significant amounts of time on design as well as coding and debugging. If you choose not to do this, you will have difficulty finishing the assignments on time.

We do not mind being asked for help; indeed, we welcome it because it helps us know what the students are finding difficult or confusing, and sometimes a few words about the problem in class will clarify the assignment immensely. We do mind being asked for help before you have tried to think the problem through; the classic objectionable question (this really happened) occurred on a homework assignment in which the class was given a buggy program. The assignment said the program did not work, and the homework was to debug it and make it work. Within 10 minutes of the end of the class during which the assignment was given out, the instructor got this request for help: "The program does not run. What do I do now?"

So, before asking for help, please be sure that you have:

When you come to us, or send us a note, asking for help, please bring whatever you have done to solve the problem, because the first question we will ask you is "What have you tried to solve the problem?" This is not because we think you are wasting our time; it is because understanding how you have tried to solve the problem will help us figure out exactly what the problem is and what we can do to help you solve it. Remember, we will do everything we can to avoid solving the problem for you; when we give you help, our goal is to help you solve the problem yourself.

What We Look For In Programming Exercises

When we grade your homework, we look for simplicity, clarity, elegance, and documentation. Here is a rough weighting of the various factors that go into the grade of each program:
Commenting, ease of reading20%
Clean, readable output10%
Documentation (README, man page, etc.)10%
If a program does not compile (or assemble), the maximum you can get is 40% of the value of the program. So check your programs before you submit them!

Late Homework

In general, late homework will not be accepted. Requests for exceptions will be handled on a case-by-case basis.

Grade Appeals

If you feel that there is an error in grading, please come see me or the TA and we will look over it (and possibly talk with you about it). However, do not dally; any such request must be made within one week of when the grades were made available. After that, we will not change your grade.
handin - file submission program

/usr/pkg/bin/handin touser [ subdirectory [ files ... ] ]

Handin provides a secure means of submitting files to another user, recounting what has already been submitted, and listing what subdirectories exist for containing submissions.


Submitting files
With touser, subdirectory and files all specified, each file is copied to ~touser/handin/subdirectory/fromuser, named with the original file's basename(1), and made owned by touser. The directory fromuser is made if it doesn't already exist and is named after the invoking user. Each file specified should have a basename(1) unique among any files already submitted by that user to subdirectory, unless overwriting is desired.

Recounting submissions
Without files specified, information on previous submissions by the user to the specified subdirectory is shown.

Listing existing subdirectories
Run with only touser specified, handin just lists the existing subdirectories (regardless of accessability).

The following examples illustrate the use as a homework submission facility to the pseudo-user "cs101" created for this purpose:

example1% handin cs101
Existing subdirectories (comments in parentheses):
Asn1    (Due Mar 18)
Asn2    (Due Mar 25)
example2% handin cs101 Asn1 part1 part2
Submitting part1... ok
Submitting part2... ok
example3% handin cs101 Asn1
The following input files have been received:
Thu Mar 17 14:50:49 1994        1599 bytes      part1
Thu Mar 17 14:50:49 1994        3412 bytes      part2


handin itself provides only a little of the diagnostic information that's given and returns the number of errors encountered as its exit status. Any other information comes from rcvhandin(8).

Skipping file: file non-existant or irregular
The named file didn't exist or was probably a directory. The user should check to make sure that the file they specified was indeed the file they intended to submit.

Skipping file: file not readable
The named file was not readable by the user.

Submitting file... failed [: reason ]
The named file was not successfully submitted. If at all possible a reason is provided by rcvhandin(8).

Submitting file... ok
The named file was successfully submitted.

Handin is really just a front-end to the rcvhandin(8) program. The primary function of handin is to open the named files with the effective user ID of the invoking user and pass on their contents to the rcvhandin(8) program having the effective user ID of touser. This design provides a simple and portable means for implementing a file submission facility in even a non-homogeneous, network-file-system environment.

Lou Langholtz, Department of Computer Science, University of Utah, 1994

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Department of Computer Science
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Page last modified on 1/20/97