bn# OS Demos

This repository contains a standalone container that can run the course registration example from lectures.

Nick made this pretty quickly and it's likely to have bugs. If you have problems, please feel free to post on Ed. If you have issues, please take a look at the code following the directory structure below--this may give you what you need.

Directory structure

This repository contains directories relevant to the demos:

• home: This is user Alice's home directory, which will be the starting point when running the container (and how you can run attacks).
  • When the container is running, this directory is shared with the host system--placing files here will make them appear inside the container.
• registrar: Source code used to create /home/registrar inside the container. This contains the vulnerable code we examined in lecture, particularly reg.sh.
  • NOTE: Unlike home, this directory is NOT live-updating. If you want to change any of the files here, you can either get a shell inside the container as the registrar user, or erase your container image and build the image again (instructions below)

How to use

This repository contains a Dockerfile that closely represents the one that will be deployed to students, with some changes to allow editing of the web application code. You can work with the image using the run-container script:

Initial setup: build the container image

./run-container setup

Starting the container

./run-container

This will start the container as the user "alice". You can run the binary "reg" to access the registration system as in class.

Getting a shell (as any user)

Unlike our primary development container, this one just starts the webserver directly--it doesn't give you a shell. To get one, open a new terminal and run:

./run-container shell <user>

where user is alice, registrar or root. This will start a shell inside your running container.

(Could you do this in your Handin container? Sure, but it's not going to get you any closer to finding any vulnerabilities that will count for credit.)

Working with the registration system

Here's some examples of using the registration system.

# List available courses
$ reg list

# List availability in cs1660 (with students, if admin)
$ reg list cs1660

# Add user to course
$ reg add cs1660 <file with override code>

Other container tasks

Want to play around with the container? Here are some other helpful functions.

Resetting the container

To restart the container from fresh copy of the image, run:

./run-container --clean start

This will start a new container from the original image, erasing any changes made to the container filesystem.

Note for development: this doesn't affect the webroot directory, which is shared with your local machine--any changes you make here are still saved. To revert these, revert the changes in your git repo.

Erasing the container image

If you want to free up space and delete the container image entirely, run:

./run-container clean-image

This deletes any containers and the image itself, (hopefully) removing it completely from your Docker storage.