University of Minnesota
Development of Secure Software Systems

CSci 4271 Lab 7

This week we'll continue with the theme of attacking vulnerabilities in web software, but consider a different class of problems: SQL injection. Since desktop machines are less likely to have a SQL server available compared to a web browser, you'll be using some externally-created vulnerable code named WebGoat which contains an internal SQL server. It's more explicitly tutorial-style than many of our other labs; if you like the style you might also look at the modules it provides on other web vulnerabilities.

As usual in the online lab we'll randomly split you into breakout groups of 2-3 students: please work together, discuss, and learn from the other student(s) in you group. Use the "Ask for Help" button to ask questions or show off what you've done.

Because WebGoat packages a web site that intentionally contains lots of vulnerabilities, you might wonder whether there's a risk from leaving it running. WebGoat itself has a some scary-sounding disclaimers on the login page and recommends that you run it on a computer disconnected from the Internet, but of course that's not a very practical suggestion if you need to be running Zoom on your computer at the same time. Our recommendation is that running it on an Internet-connected computer is sufficiently safe, though we would still recommend killing it when you're not using it. If your personal computer (e.g., laptop) has Java 11 and a browser, you can run it there. It's also set up to be easily run in a Docker container if you happen to have that set up. Directions for using these configurations can be found on the WebGoat site here. The rest of the instructions will describe running it on CSE Labs machines; this is a less ideal situation because the machines are all multi-user, but the risk is still limited because the ultimate effect of WebGoat's vulnerabilities is intentionally circumscribed. (The SQL injection vulnerabilities themselves only expose fake databases.)

WebGoat is packaged as a large .jar file, so it's better not to copy it to your home directory; instead we've downloaded a single copy that everyone can use. Choose a random port number between 8000 and 9000 for the server (the examples use 8234) and another random port number between 9000 and 10000 for the database server (the examples use 9234). The WebGoat program will produce lots of (unimportant) messages on the terminal, so we recommend running it in its own terminal window, and because it only allows connections from the same machine, you should run it on a machine where you can also run a web browser (e.g., Vole). The command to start it looks like:

env WEBGOAT_HSQLPORT=9234 java -jar /web/classes/Spring-2021/csci4271/labs/07/webgoat-server-8.1.0.jar --server.port=8234

It should take a few seconds to start up and then print a message that looks like Started StartWebGoat in 8.645 seconds. When you want to stop the server, you can kill it by typing Control-C in the window where it is running. The program will also store some persistent data in your home directory in a directory named .webgoat-8.1.0; you can remove this if you're done with it.

Once the WebGoat web server is running you can connect to it from your favorite web browser (on the same machine) at a URL like:


Where of course you replace 8234 with the port number you chose in the previous step. You'll have to create an account when you log in for the first time.

The main set of exercises we'd like you to work on in lab are the introduction to SQL and SQL injection that are found in the menu on the left side of the page under (A1) Injection > SQL Injection (intro). It starts with some basic questions that review different aspects of SQL syntax, but the questions are straightforward enough that you should be able to see what's going on from the provided examples, error messages, and a basic knowledge of SQL syntax, for instance as summarized in this site's table.

One thing to note is that the SQL queries you'll be messing with all use single quotes around strings, which is the standard SQL syntax for strings. The double quotes you see next to them in examples are the Java string syntax because the sample code for the program constructing the queries is Java code, using double quotes for strings and + for string concatenation. (Because the SQL standard assigns double quotes to an arguably less important purpose and database vendors have historically not followed the standard in all aspects, several "SQL" servers non-standardly interpret double quotes as an alternative string syntax, but not the one used by WebGoat.)

If you finish with the intro-level SQL injection module, you can go on to the advanced module, which discusses blind SQL injection and has a more difficult example. It's not important that you take the multiple-choice quiz that's the last page of the advanced section; confusingly it's actually mostly about mitigations. The module labeled mitigation mostly covers material that is beyond our scope, though you might still find parts of it interesting.