TryHackMe: Ninja Skills Writeup

17 Feb, 2022

ninja

Ninja Skills is a TryHackMe room for improving Linux command line skills. Note that all answers have been redacted from this writeup.

We are tasked with answering a set of questions about the following files:

8V2L
bny0
c4ZX
D8B3
FHl1
oiMO
PFbD
rmfX
SRSq
uqyw
v2Vb
X1Uy

The goal is to solve the challenges as efficiently as possible. Most of the challenges can be solved with some form of

find / -name <filename>  -exec <command> \;

To keep track of the target files, I added them to a text file:

$ cat filenames
8V2L
bny0
c4ZX
D8B3
FHl1
oiMO
PFbD
rmfX
SRSq
uqyw
v2Vb
X1Uy

Now I can use a for loop to run a command against each file! The basic syntax for this is:

for i in $(cat filenames); do find / -name "$i"  -exec <command> \; 2>/dev/null; done

Challenge Questions

Challenge 1: Which of the above files are owned by the best-group group?

Use the -group <groupname> switch to find all files owned by a specific group:

$ find / -group best-group  2>/dev/null

Challenge 2: Which of these files contain an IP address?

We can use grep to find an IP address in a file.

grep -Eo '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}'

Now, add it to the find command:

$ for i in $(cat filenames); do find / -name "$i" -exec grep -E -o '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' '{}' \; 2>/dev/null; done
1.1.1.1

Sweet, it works! To print the filename, change the -o to a -l

$ for i in $(cat filenames); do find / -name "$i" -exec grep -E -l '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' '{}' \; 2>/dev/null; done

Challenge 3: Which file has the SHA1 hash of 9d54da7584015647ba052173b84d45e8007eba94

Add -exec sha1sum '{}' \; to our find command in order to take the sha1sum of each file!

$ for i in $(cat filenames); do find / -name "$i"  -exec sha1sum '{}' \; 2>/dev/null; done | grep 9d54

Challenge 4: Which file contains 230 lines?

Add -exec wc -l '{}' \; to the find command:

$ for i in $(cat filenames); do find / -name "$i"  -exec wc -l '{}' \; 2>/dev/null; done 
209 /etc/8V2L
209 /mnt/c4ZX
209 /mnt/D8B3
209 /var/FHl1
209 /opt/oiMO
209 /opt/PFbD
209 /media/rmfX
209 /etc/ssh/SRSq
209 /var/log/uqyw
209 /home/v2Vb
209 /X1Uy

The file that is missing is the answer to the question.

Challenge 5: Which file’s owner has an ID of 502?

View file ownership by adding -exec ls -la '{}' \;.

In the below output, there is one file owner who is not our current user.

$ for i in $(cat filenames); do find / -name "$i"  -exec ls -la '{}' \; 2>/dev/null; done 
-rwxrwxr-x 1 new-user new-user 13545 Oct 23  2019 /etc/8V2L
-rw-rw-r-- 1 new-user new-user 13545 Oct 23  2019 /mnt/c4ZX
-rw-rw-r-- 1 new-user best-group 13545 Oct 23  2019 /mnt/D8B3
-rw-rw-r-- 1 new-user new-user 13545 Oct 23  2019 /var/FHl1
-rw-rw-r-- 1 new-user new-user 13545 Oct 23  2019 /opt/oiMO
-rw-rw-r-- 1 new-user new-user 13545 Oct 23  2019 /opt/PFbD
-rw-rw-r-- 1 new-user new-user 13545 Oct 23  2019 /media/rmfX
-rw-rw-r-- 1 new-user new-user 13545 Oct 23  2019 /etc/ssh/SRSq
-rw-rw-r-- 1 new-user new-user 13545 Oct 23  2019 /var/log/uqyw
-rw-rw-r-- 1 new-user best-group 13545 Oct 23  2019 /home/v2Vb
-rw-rw-r-- 1 newer-user new-user 13545 Oct 23  2019 /X1Uy

There is one unique file owner. Run id <user> to get their UID.

Challenge 6: Which file is executable by everyone?

The -executable switch displays files that are marked as executable:

$ for i in $(cat filenames); do find / -name "$i" -executable 2>/dev/null; done