Loi Tran

Over the Wire Bandit

A walkthrough and review of Over the Wire Bandit.

By completing this series of challenges we learn fundamentals of linux, bash, file system, net cat, cronjobs and more.

For each challenge we SSH into a remote server and must find a hidden PW somewhere on the file system.

Each password grants access to the next server/challenge.

0 - SSH to remote machine

How to SSH into a remote machine.

Use SSH cli command with username, host and port.

ssh bandit0@bandit.labs.overthewire.org -p 2220

bandit0

1 - How to handle dash file names

The password for the next level is stored in a file called - located in the home directory

ssh bandit1@bandit.labs.overthewire.org -p 2220

NH2SXQwcBdpmTEzi3bvBHMM9H66vVXjL

Use cat with an absolute or relative path cat /home/bandit1 and cat ./- respectively.

cat /home/bandit1
# or
cat ./-

2 - How to handle spaces in file names

The password for the next level is stored in a file called spaces in this filename located in the home directory

ssh bandit2@bandit.labs.overthewire.org -p 2220

rRGizSaX8Mk1RTb1CNQoXTcYZWU6lgzi

Use escape character \ before spaces in file names.

cat ./spaces\ in\ this\ filename

3 - How to view hidden files

The password for the next level is stored in the only human-readable file in the inhere directory. Tip: if your terminal is messed up, try the “reset” command.

ssh bandit3@bandit.labs.overthewire.org -p 2220

aBZ0W5EmUfAf7kHTQeOwd8bauFJ2lAiG

Use ls with -al flags to include hidden files in output.

ls -al

4 - How to identify human readable files

Identify ASCII text files using file command.

ssh bandit4@bandit.labs.overthewire.org -p 2220

2EW7BBsr6aMMoJ2HjW067dm8EgX26xNe

file ./-file*

Use file command to identify file types.

5 - Search for files matching criteria/flags

The password for the next level is stored in a file somewhere under the inhere directory and has all of the following properties:

ssh bandit5@bandit.labs.overthewire.org -p 2220

lrIWWI6bB37kxfiCQZqUdOIYfr6eEeqR

Search a path for file meeting parameters. After finding the file then cat it.

find ./ -type f -size 1033c ! -executable

6 - Search for files beloning to specific user and group

ssh bandit6@bandit.labs.overthewire.org -p 2220

P4L4vucdmLnm8I7Vl7jG1ApGSfjYKqJU

Search from root directory for file meeting specific parameters.

Specifically user, group, size

find / -user bandit7 -group bandit6 -size 33c

View specific file we got from the previous output

cat /var/lib/dpkg/info/bandit7.password

7 - Find specific text in a file

ssh bandit7@bandit.labs.overthewire.org -p 2220

z7WtoNQU2XfjmMtWA8u5rN4vzqu4v99S

Using grep we can find lines containing specific strings.

Include line numbers with -n.

grep -n millionth data.txt

8 - How to organize/filter lines in a long file

The password for the next level is stored in the file data.txt and is the only line of text that occurs only once

ssh bandit8@bandit.labs.overthewire.org -p 2220

TESKZC0XvTetK0S9xNwm25STk5iWrBvP

Sort the lines lexicographically and only grab unique lines.

sort data.txt | uniq -u

9 - How to parse binary data to human readable format

The password for the next level is stored in the file data.txt in one of the few human-readable strings, preceded by several ‘=’ characters.

ssh bandit9@bandit.labs.overthewire.org -p 2220

EN632PlfYiZbn3PhVK3XOGSlNInNE00t

Use strings to print the sequence of printable characters in files.

cat data.txt | strings -e s | grep ==

10 - How to decode from base64

The password for the next level is stored in the file data.txt, which contains base64 encoded data

ssh bandit10@bandit.labs.overthewire.org -p 2220

G7w8LIi6J3kTb8A7j9LgrywtEUlyyp6s

cat data.txt | base64 -d

11 - How to translate file output using TR command

The password for the next level is stored in the file data.txt, where all lowercase (a-z) and uppercase (A-Z) letters have been rotated by 13 positions

ssh bandit11@bandit.labs.overthewire.org -p 2220

6zPeziLdR2RKNdNYFNb6nVCKzphlXHBM

Rotate chars by 13 using a special command

cat data.txt | tr "A-Za-z" "N-ZA-Mn-za-m"

12 - How to investigate contents of binary files

The password for the next level is stored in the file data.txt, which is a hexdump of a file that has been repeatedly compressed. For this level it may be useful to create a directory under /tmp in which you can work using mkdir. For example: mkdir /tmp/myname123. Then copy the datafile using cp, and rename it using mv (read the manpages!)

ssh bandit12@bandit.labs.overthewire.org -p 2220

JVNBBFSmZwKKOP0XbFXOoW8chDz5yVRv

mkdir -p /tmp/workhere && cp data.txt /tmp/workhere && cd /tmp/workhere

Create directory for tmp stuff, copy data.txt over, and move into that directory.

cat data.txt | xxd -r > data

Reverse hex dump

mv data data2.gz

gzip -d data2.gz

We change the suffix of data back to .gz, which means the file would be renamed to data2.gz. Then, we use gzip to decompress the file. Afterward, we use the file command to check the information of data2 again.

mv data2 data3.bz bzip2 -d data3.bz file data3

Run this loop a few times uncompressing

13 - How to use a private key to ssh into a remote machine

The password for the next level is stored in /etc/bandit_pass/bandit14 and can only be read by user bandit14. For this level, you don’t get the next password, but you get a private SSH key that can be used to log into the next level. Note: localhost is a hostname that refers to the machine you are working on

ssh bandit13@bandit.labs.overthewire.org -p 2220

wbWdlBxEir4CaE8LaPhauuOo6pwRmrDw

Use private key on bandit13 to ssh into bandit14.

ssh -i sshkey.private bandit14@bandit.labs.overthewire.org -p 2220

Check the file in this machine.

cat /etc/bandit_pass/bandit14

14 - Use NC to send messages to local http server

The password for the next level can be retrieved by submitting the password of the current level to port 30000 on localhost.

ssh bandit14@bandit.labs.overthewire.org -p 2220

fGrHPx402xGC7U7rXKDaxiWFTOiF0ENq

Echo the password to this level to port 30000 using nc

echo "fGrHPx402xGC7U7rXKDaxiWFTOiF0ENq" | nc localhost 30000

15 - Use OpenSSL to connect

The password for the next level can be retrieved by submitting the password of the current level to port 30001 on localhost using SSL encryption.

Helpful note: Getting “HEARTBEATING” and “Read R BLOCK”? Use -ign_eof and read the “CONNECTED COMMANDS” section in the manpage. Next to ‘R’ and ‘Q’, the ‘B’ command also works in this version of that command…

ssh bandit15@bandit.labs.overthewire.org -p 2220

jN2kgmIXJ6fShzhT2avhotn4Zcka6tnt

Open ssl connection

openssl s_client -connect localhost:30001

Submit password through SSL connection

jN2kgmIXJ6fShzhT2avhotn4Zcka6tnt

16 - How to check for open ports and create a ssh key

Use nmap to identify open ports and openssl to send them passwords

The credentials for the next level can be retrieved by submitting the password of the current level to a port on localhost in the range 31000 to 32000. First find out which of these ports have a server listening on them. Then find out which of those speak SSL and which don’t. There is only 1 server that will give the next credentials, the others will simply send back to you whatever you send to it.

After getting the key you should create a bandit.key on local and then chmod it. Afterwards use the key to ssh into a remote machine for 17

ssh bandit16@bandit.labs.overthewire.org -p 2220

JQttfApK4SeyHwDlI9SXGR50qclOAil1

Use nmap to identify open ports.

nmap -p 31000-32000 localhost

cat /etc/bandit_pass/bandit16 | openssl s_client -connect localhost:31046 -quiet
cat /etc/bandit_pass/bandit16 | openssl s_client -connect localhost:31518 -quiet
cat /etc/bandit_pass/bandit16 | openssl s_client -connect localhost:31691 -quiet
cat /etc/bandit_pass/bandit16 | openssl s_client -connect localhost:31790 -quiet
cat /etc/bandit_pass/bandit16 | openssl s_client -connect localhost:31960 -quiet

Save key to a local file named

bandit.key

Use chmod 400 to give user read permission and remove all other permissions to bandit.key.

chmod 400 bandit.key

Use the created key to ssh into next level .

ssh -i bandit.key bandit17@bandit.labs.overthewire.org -p 2220

17 - How to check for differences in two files

There are 2 files in the homedirectory: passwords.old and passwords.new. The password for the next level is in passwords.new and is the only line that has been changed between passwords.old and passwords.new

diff passwords.new passwords.old

18 - hga5tuuCLF6fFzUpnagiMN8ssu9LFrdg

The password for the next level is stored in a file readme in the homedirectory. Unfortunately, someone has modified .bashrc to log you out when you log in with SSH.

ssh bandit18@bandit.labs.overthewire.org -p 2220 "cat ~/readme"

hga5tuuCLF6fFzUpnagiMN8ssu9LFrdg

SSH in and invoke command immediately.

ssh bandit18@bandit.labs.overthewire.org -p 2220 "cat ~/readme"

19 - Use a binary to access a file as a different user

To gain access to the next level, you should use the setuid binary in the homedirectory. Execute it without arguments to find out how to use it. The password for this level can be found in the usual place (/etc/bandit_pass), after you have used the setuid binary.

ssh bandit19@bandit.labs.overthewire.org -p 2220

awhqfNnAbc1naukrpqDYcF95h7HoMTrC

Use another user's permissions to run an executable.

Use the binary to run commands on other files as bandit20.

ls -al ./bandit20-do
./bandit20-do
./bandit20-do id
ls /etc/bandit_pass/bandit*
ls /etc/bandit_pass/bandit20
cat /etc/bandit_pass/bandit20
./bandit20-do cat /etc/bandit_pass/bandit20

20 - VxCazJaVykI6W36BkBU0mJTCM8rR95XT

There is a set uid binary in the home directory that does the following: it makes a connection to localhost on the port you specify as a commandline argument. It then reads a line of text from the connection and compares it to the password in the previous level (bandit20). If the password is correct, it will transmit the password for the next level (bandit21).

ssh bandit20@bandit.labs.overthewire.org -p 2220

VxCazJaVykI6W36BkBU0mJTCM8rR95XT

Two techniques, one using 2 socket connections.

Set up an nc listener on one terminal.

nc -lp 6000

Connect to listening port

./suconnect 6000

Enter password in original nc port listener and watch pw get spit out of other terminal.

VxCazJaVykI6W36BkBU0mJTCM8rR95XT

Start background process

echo -n 'VxCazJaVykI6W36BkBU0mJTCM8rR95XT' | nc -l -p 1234 &

Now try to connect to background process.

./suconnect 1234

21 - Find password inside of cron job

A program is running automatically at regular intervals from cron, the time-based job scheduler. Look in /etc/cron.d/ for the configuration and see what command is being executed.

ssh bandit21@bandit.labs.overthewire.org -p 2220

NvEJF7oVjkddltPSrdKEFOllh9V1IBcq

Checkout the directory where cron jobs are saved.

The cronjob for bandit22 runs a bash script which redirects the output to be thrown away.

cd /etc/cron.d
cat cronjob_bandit22

The bash script will create a file that can be rw by owner and r by group and others. We copy the contents of etc to that tmp file.

cat /usr/bin/cronjob_bandit22.sh
cat /tmp/t7O6lds9S0RqQh9aMcz6ShpAoZKF7fgv

22 - How to set variables in bash?

A program is running automatically at regular intervals from cron, the time-based job scheduler. Look in /etc/cron.d/ for the configuration and see what command is being executed.

NOTE: Looking at shell scripts written by other people is a very useful skill. The script for this level is intentionally made easy to read. If you are having problems understanding what it does, try executing it to see the debug information it prints.

ssh bandit22@bandit.labs.overthewire.org -p 2220

WdDozAdTM2z9DiFEQ2mGlwngMfj4EZff

cat /usr/bin/cronjob_bandit23.sh
/usr/bin/cronjob_bandit23.sh

#!/bin/bash
 
myname=$(whoami)
mytarget=$(echo I am user $myname | md5sum | cut -d ' ' -f 1)
 
echo "Copying passwordfile /etc/bandit_pass/$myname to /tmp/$mytarget"
 
cat /etc/bandit_pass/$myname > /tmp/$mytarget

From the script, we know that the password for next level stored in the file named with $mytarget which is defined above as a md5sum. And we need to set$ myname to bandit23 to fetch the correct filename.

myname=bandit23
echo I am user $myname | md5sum | cut -d ' ' -f 1
cat /tmp/8ca319486bfbbc3663ea0fbe81326349

We define a variable then use it to

23 - Create a script

A program is running automatically at regular intervals from cron, the time-based job scheduler. Look in /etc/cron.d/ for the configuration and see what command is being executed.

NOTE: This level requires you to create your own first shell-script. This is a very big step and you should be proud of yourself when you beat this level!

NOTE 2: Keep in mind that your shell script is removed once executed, so you may want to keep a copy around…

ssh bandit23@bandit.labs.overthewire.org -p 2220

QYw0Y2aiA672PsMmh9puTQuhoz8SyR2G

cat /usr/bin/cronjob_bandit24.sh

#!/bin/bash
 
myname=$(whoami)
 
cd /var/spool/$myname/foo
echo "Executing and deleting all scripts in /var/spool/$myname/foo:"
for i in * .*;
do
    if [ "$i" != "." -a "$i" != ".." ];
    then
        echo "Handling $i"
        owner="$(stat --format "%U" ./$i)"
        if [ "${owner}" = "bandit23" ]; then
            timeout -s 9 60 ./$i
        fi
        rm -f ./$i
    fi
done

mkdir /tmp/rand
cd /tmp/rand
touch script.sh

Create a script in the tmp folder which will be ran by the cron job.

#!/bin/bash
cat /etc/bandit_pass/bandit24 > /tmp/rand/password

The script reads out the password from bandit24 and then puts it inside our tmp file.

We do this because we cannot directly access /etc/bandit_pass/bandit24

cp script.sh /var/spool/bandit24/foo
chmod 777 /tmp/rand

Move our script to the dir where the original script will run and change permissions on the current dir.

24 - Loop with bash

A daemon is listening on port 30002 and will give you the password for bandit25 if given the password for bandit24 and a secret numeric 4-digit pincode. There is no way to retrieve the pincode except by going through all of the 10000 combinations, called brute-forcing. You do not need to create new connections each time

ssh bandit24@bandit.labs.overthewire.org -p 2220

VAfGXJ1PBSsPSnvsjI8p759leLZ9GGar

nc localhost 30002

mktemp -d
cd /tmp/tmp.3YQNHtW1Uu
nano brute_force_pin.sh
chmod +x brute_force_pin.sh

#!/bin/bash
 
for i in {0000..9999}
do
        echo VAfGXJ1PBSsPSnvsjI8p759leLZ9GGar $i >> possibilities.txt
done
 
cat possibilities.txt | nc localhost 30002 > result.txt

Our script will brute force all possible solutions.

25 - Change editor modes in order to enter a shell

Logging in to bandit26 from bandit25 should be fairly easy… The shell for user bandit26 is not /bin/bash, but something else. Find out what it is, how it works and how to break out of it.

ssh bandit25@bandit.labs.overthewire.org -p 2220

p7TaowMYrmu23Ol8hiZh9UvD0O9hpx8d

ssh -i bandit26.sshkey bandit26@localhost -p 2220

SSH into bandit25 using the key provided. It will use another shell by default. We can use the more shell with vim mode to read out of it with command.

:e /etc/bandit_pass/bandit26

26 - Use more to get a shell and run a script

Good job getting a shell! Now hurry and grab the password for bandit27!

ssh bandit26@bandit.labs.overthewire.org -p 2220

c7GvcKlw9mC7aUQaPx7nwFstuAIBw1o1

:set shell=/bin/bash

:shell

./bandit27-do cat /etc/bandit_pass/bandit27

27 - Clone repo using ssh connection

There is a git repository at ssh://bandit27-git@localhost/home/bandit27-git/repo. The password for the user bandit27-git is the same as for the user bandit27.

Clone the repository and find the password for the next level.

ssh bandit27@bandit.labs.overthewire.org -p 2220

YnQpBuifNMas1hcUFk70ZmqkhUU2EuaS

Clone repo and read password for the next level. Make sure you add a port.

git clone ssh://bandit27-git@localhost:2220/home/bandit27-git/repo

28 - Find password in previous commit

There is a git repository at ssh://bandit28-git@localhost/home/bandit28-git/repo. The password for the user bandit28-git is the same as for the user bandit28.

Clone the repository and find the password for the next level.

ssh bandit28@bandit.labs.overthewire.org -p 2220

AVanL161y9rsbcJIsFHuw35rjaOM19nR

git clone ssh://bandit28-git@localhost:2220/home/bandit28-git/repo

git checkout COMMIT

29 - Get pw on different branches

There is a git repository at ssh://bandit29-git@localhost/home/bandit29-git/repo. The password for the user bandit29-git is the same as for the user bandit29.

Clone the repository and find the password for the next level.

ssh bandit29@bandit.labs.overthewire.org -p 2220

tQKvmcwNYcFS6vmPHIUSI3ShmsrQZK8S

git clone ssh://bandit29-git@localhost:2220/home/bandit29-git/repo

30 - Get pw from tags on git

There is a git repository at ssh://bandit30-git@localhost/home/bandit30-git/repo. The password for the user bandit30-git is the same as for the user bandit30.

Clone the repository and find the password for the next level.

ssh bandit30@bandit.labs.overthewire.org -p 2220

xbhV3HpNGlTIdnjUrdAlPzc2L6y9EOnS

git clone ssh://bandit30-git@localhost:2220/home/bandit30-git/repo

31 - Get pw by committing file and pushing to remote.

There is a git repository at ssh://bandit31-git@localhost/home/bandit31-git/repo. The password for the user bandit31-git is the same as for the user bandit31.

Clone the repository and find the password for the next level.

ssh bandit31@bandit.labs.overthewire.org -p 2220

OoffzGDlzhAlerFJ2cAiz1D41JW1Mhmt

git clone ssh://bandit31-git@localhost:2220/home/bandit31-git/repo

32 - Use $0 to reference current shell

After all this git stuff its time for another escape. Good luck!

ssh bandit32@bandit.labs.overthewire.org -p 2220

rmCBvG56y58BXzv98yZGdO7ATVL5dW8y

33 - Final level

After all this git stuff its time for another escape. Good luck!

ssh bandit33@bandit.labs.overthewire.org -p 2220

odHo63fHiFqcWWJG9rLiLDtPm45KzUKy