Topics CS379 in Computer Science Fall 2004 Fundamentals of Computer Security Prof. L. Felipe Perrone Homework 3 Phase 3 Posted: Wednesday, November 17, 2004 Due: Wednesday, December 1, 2004, at the beginning of class.
Important Notice 1: This assignment is to be done in teams of two. You may collaborate with other teams in this class under the following guidelines:
You are not allowed to give your code to anyone. You are not allowed to take code from anyone. If you receive help from anyone, you must acknowledge that person or team in your write up and specify the issue on which you were helped. If you take code from any source (in print or on the WWW), you must acknowledge that source and list its complete reference (bibliographic information or URL). You are allowed to collaborate with other teams as long as you dont exchange any written material, and as long as no one dictates C++ code to you. You are allowed, in fact encouraged, to share your knowledge as long as what is shared are only desing, concepts, and ideas (no specic implementation details).
Important Notice 2: The assignment must be completed in the C++ programming language and it must use the mhash library. If you use any other programming language or any method for generating message digests and message authentication codes other than those provided in mhash, you will not receive credit for this assignment. Objectives: In this homework assignment you will extend the programs you have written for Phases 1 and 2 of this project. You are allowed to reuse the previous work of either member of your team. The main goal is to nalize the construction of a system that produces cryptographic hashes for all the les encountered on the recursive traversal from a given directory.
Your executable program must be called boobytrap (because were implementing the functionality of Tripwire). It must take two command line parameters as in the example below: boobytrap MODE HMAC-TYPE PATH PASSPHRASE where HMAC-TYPE is either HMACMD5 or HMACSHA1, PATH indicates a path used as the starting point for the recursive traversal of directories, and PASSPHRASE is a string containing no blank space characters used to generate HMAC values and for something else explained below. The parameter MODE will tell your program whether it will be generating output to a le named boobytrap db or reading the le and diplaying its contents on the terminal. This parameter can assume only one of two values: -g, which implies the creation of boobytrap db or -r, which implies that boobytrap db will simply be read and displayed on the terminal.
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As its name implies, boobytrap db is a le containing a database. This database is extremely similar to the output you generated for Phase 2 of this project. Actually, calling it a database is a bit of a stretch, but its the most appropriate word we can nd. It should contain, at least, the all the elds in the example below. -rw-------rw-------rw-------rw-------rw-------rw------user user user user user user group group group group group group 980 Oct 11 16:22:32 2004 /dude/.cshrc [hash value] 60792 Oct 11 16:24:01 2004 /dude/hw/hw1.pdf [hash value] 30196 Oct 11 16:20:12 2004 /dude/hw/hw2.pdf [hash value] 4333 Oct 11 16:19:20 2004 /dude/mail/mom.txt [hash value] 1199 Oct 11 16:22:00 2004 /dude/mail/santa.txt [hash value] 20507 Oct 11 16:10:03 2004 /dude/downloads/free.tgz [hash value]
Note that dierently from Phase 2 output, rather than list simply lenames, we list the absolute path starting from the root directory for every le, together with their corresponding HMAC value generated for the given passphrase and other le attributes specied in Phase 2 of this project. You can go about the generation of le this in dierent ways and the nal choice is yours. You can make it be a textle, what would be extremely simple. Alternatively, you can use a binary le and format it so that each line in the example above corresponds to a record, which is dened as a data structured with multiple elds such as: permissions, user ownership, group ownership, size, etc. Each eld would be of a data type most appropriate to what it represents: numeric or alphanumeric. Theres an important restriction, however. The le produced must be encrypted le using the des-cbc cipher. Although, at this point, you may be scratching your head about how to accomplish this, let me tell you: its going to be nearly trivial. Youre not going to code this cipher, but instead, you will use the openssl program to do it for you. This program is installed on both our Sun Solaris and on our Intel Linux systems. Although the Solaris installation doesnt have a man-page, the Linux installation does. You can also nd information on how to use this program on the web (for instance at http://www.openssl.org/). Basically, to encrypt a le from the command you do: openssl enc -e -salt -des-cbc -in filename -out filename.enc -pass pass:PASSPHRASE Then, to decrypt it, you do: openssl enc -d -des-cbc -in filename.enc -out filename.dec -pass pass:PASSPHRASE You should try this out on your favorite text le called, say, filename, and then run the program diff to compare filename and filename.dec. They should be absolutely identical. As the examples above imply, you will be using the same PASSPHRASE for the generation of HMACs and for des-cbc encryption of the database. Although one can argue this may not the best of ideas, well just go with it for the sake of not complicating the assignment any further. Ok, so this wont be bad, but wait a second... how do you call a program from inside a C++ program? Hmm... if you dont know how to do that, you are about to teach yourself! Look at the man-page for the system command on Section 3 of the Unix manual. Important: In pursuing this goal you must continue to follow the best practices guidelines for secure programming.
Specications: See the section Objectives above; it outlines the minimal expectations that you must follow...