L2: Bash Mash

L2: Bash Mash#

Objectives#

Review Bash essentials
1. Using bash on the command line
2. Creating and running bash scripts
3. Review/Learn bash shell commands / operations

Overview#

This lab walks through setting up the developer environment we will use throughout the semester, followed a short lab reviewing and developing bash skills.

Context#

In this course, we will frequently run code and commands on a raspberry pi.

An efficient way to work on a remote computer like the pis is to setup a remote bash connection using ssh.

That way, you can write code on a preferred computer, while running code and other commands directly on the raspberry pi as you work.

Using ssh effectively requires getting comfortable with the CLI shell – in this course, our shell will be bash.

Part of getting comfortable with bash is simply getting in the habit of using it for useful things.

Deliverables#

Documenting your progress: Progress on bandit-instructions.txt committed to the lab-0 branch of this repository
- A completed bandit-instructions.txt up to and including Level 7 is worth 100%.
- Some marks will be docked for missing levels/information in the .txt
- Feedback will be given directly in the lab-0 pull request.
In-class demo: Use less to preview progress documenting the bandit-instructions.txt
- The bandit-instructions.txt does not have to be complete to get full marks for the in-person demo.

Deadline#

In class demos: Friday Jan 31 (beginning of class)
bandit-instructions.txt progress committed: Friday Jan 31 (end of day)

Using bash: complete the Bandit game#

To get us warmed up with using ssh to connect to a remote computer, and using the various bash tools at our disposal, the bandit game is great practise.

For this lab, we will aim to complete up to Level 8.

Each level of the bandit game requires you use one or more bash commands to complete the level.

Getting started#

Open a terminal on your developer environment. All ssh commands for the game will be done here.
- On Windows, use your WSL container
- If working on OSX or Linux, use your default terminal
Open lab-0/bandit-instructions.txt in your editor
- You will use this file to record your progress through the lab.
- The rubric for this lab is based on completing this file.
The instructions for the lab are contained in the game itself.
- To start the lab, read the Note for beginners
- Then proceed to Level 0

[!NOTE] if you are getting “hostname not resolved” issues in WSL, follow the steps below:

sudo vim /etc/wsl.conf , add the following:

[network]

generateResolvConf = false

sudo vim /etc/resolv.conf , add the following:

nameserver 8.8.8.8

sudo chattr -f +i /etc/resolv.conf

For more detail, see https://askubuntu.com/questions/1364984/dns-not-working-on-wsl

Extra info & Hints#

Each level of the game challenges you to log in to a given user on a linux server hosted at bandit.labs.overthewire.org.
- We’ll be doing this a lot when we ssh into our raspberry pis throughout the lab.
To complete each level, you need to find the password for that user. This password is stored on a file in that user account on the server.
Each level, you are given Commands you may need to solve this level – the levels can be solved in many different ways, using one or more of those commands.
- That is: you will never need a command that is NOT listed in the Commands section. But, you do not have to use all of them; there are many ways to solve each puzzle.
- Make sure you look at the commands available to you at each step, the hints are given for good reason.
Use man to see what the suggested command can do for you. Use Ctrl + d and Ctrl + u to scroll up and down the terminal efficiently, and / to search.

Documenting your progress#

As you complete each level, write down in lab-0/bandit-instructions.txt the following:

the password needed to start the next level
the commands used to find the file
comments explaining the commands
- e.g. necessary parameters/flags

[!NOTE] In each level, the password is a long string of random characters stored in a file on the server. You will need to copy and paste the password frequently – from your bandit-instructions.txt and to your bandit game terminal.

Copy/paste is a bit different on terminals than you may be used to:

Highlight the text holding Left+click

Copy the text using Ctrl+Shift+C

Paste the text using Ctrl+Shift+V

Follow the format in the bandit-instructions.txt file. Make sure you read and follow the instructions given in the comments (marked by #).

As you complete the bandit-instructions.txt file, track your progress on the lab-0 branch using git commit. Before you finish working, make sure you git push your commits to upstream lab-0 branch of this repository.

Don’t be shy: you should be committing and pushing your progress to your branch regularly, even if it is not finished – this will let you continue where you left off easily no matter what computer you are working on.

The rubric for this lab is based on completing this file:

100%: All levels up to and including Level 7 are documented correctly
Marks off for mistakes or missing levels.

In-class demo#

[!NOTE] Wait until you have completed, documented, committed, and pushed at least 2 or 3 steps of the bandit game before beginning these instructions.

Another good use for bash and the terminal is not just commands and remote connections – it’s actually a great tool for documentation, too.

To get a sense for that, I want you to show me that you can use less to do the following:

navigate through your bandit-instructions.txt without needing my instructions
find commands/passwords for a given level by searching
copy/paste information from your file to another terminal

Remember that the man command USES less by default – so if you have been using man, you will be used to the interface. If not, practise! See TODO for more information.

You do not have to be finished the whole lab to get full marks on the demo – you just have to have done a few of the levels.

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