PicoCTF Writeup – mus1c
# Information:
CTF Name: PicoCTF
CTF Challenge: mus1c
Challenge Category: General Skills/Misc
Challenge Points: 300
picoCTF 2019
# Used Tools:
# Challenge Description:
I wrote you a song. Put it in the picoCTF{} flag format.
Hints: Do you think you can master rockstar?
# Writeup
In this challenge, we are provided with a text file with song lyrics. A weird thing if you ask me. Considering the hint “can you master rockstar?” I went online and wrote rockstar programming, and this link came up.
It seems that there is indeed a programming language called rockstar!! After reading a little about it, I decided to give it a go.
Step 1
I went to https://codewithrockstar.com/online I pasted the lyrics provided in the challenge and the output was the following:
114
114
114
111
99
107
110
114
110
48
49
49
51
114
We are presented with a sequence of numbers. After some thought I tested the theory that these numbers pointed to letters in ASCII.
Step 2
In this step I tried the theorythat these numbers pointed to letters in ASCII.
114 -> r
114 -> r
114 -> r
111 -> o
99 -> c
107 -> k
110 -> n
114 -> r
110 -> n
48 -> 0
49 -> 1
49 -> 1
51 -> 3
114 -> r
Which becomes: rrrocknrn0113r.
Extra step – manual interpretation of the code.
If you want to interpret the code manual we can do that.
Note: To learn rockstar I saw this video starting at this time and also this site.
Pico's a CTFFFFFFF -> Pico = 19
my mind is waitin -> my mind = 6
It's waitin -> It = 6
Put my mind of Pico into This -> This = Pico * my mind = 114
my flag is not found -> Initializes my flag
put This into my flag -> my flag = This = 114
put my flag into Pico -> Pico = my flag = 114
shout Pico -> prints Pico = 114
shout Pico -> prints Pico = 114
shout Pico -> prints Pico = 114
My song's something -> My song = 9
put Pico into This -> This = Pico = 114
Knock This down, down, down -> This - 3 = 111
put This into CTF -> CTF = This
shout CTF -> prints CTF = 111
my lyric is nothing -> my lyric = null
Put This without my song into my lyric -> my lyrics = This - my song = 102
Knock my lyric down, down, down -> my lyric - 3 = 99
shout my lyric -> print my lyric = 99
Put my lyric into This -> This = my lyric
Put my song with This into my lyric -> my lyric = my song + This = 108
Knock my lyric down -> my lyric = 107
shout my lyric -> prints my lyric = 107
Build my lyric up, up ,up -> my lyric + 3 = 110
shout my lyric -> prints my lyric = 110
shout Pico -> prints Pico = 114
shout It -> prints = It = my lyric = 110
Pico CTF is fun -> Pico CTF = 3
security is important -> security = 9
Fun is fun -> Fun = 3
Put security with fun into Pico CTF -> Pico CTF = 3 + 9 = 12
Build Fun up -> Fun + 1 = 4
shout fun times Pico CTF -> prints 4 * Pico CTF = 48
put fun times Pico CTF into my song -> my song = 48
build it up -> my song + 1 = 49
shout it -> prints my song = 49
shout it -> prints my song = 49
build it up, up -> my song = 51
shout it -> prints my song = 51
shout Pico -> prints Pico = 114
The flag is:
Thank you very much for reading!
Cheers,
MRegra
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Hello. Interesting post, keep up the good work.