05 Apr 2020 Updated: 31 Aug 2020 Categories: Computing, CTF, MBR

CTF: MBR - Interrupt Request

Album released: 20 Sep 2017

https://masterbootrecord.bandcamp.com/album/interrupt-request

Secret

087 104 101 110 032 116 104 101 032 077 111 111 110 032 119 105 108 108 032 115 104 101 100 032 110 111 032 108 105 103 104 116 013 010 087 105 116 104 032 116 104 101 032 069 113 117 105 110 111 120 032 099 108 111 115 101 032 098 121 013 010 073 110 032 116 104 101 032 100 097 114 107 032 097 032 115 112 101 108 108 119 097 114 101 032 114 105 115 101 013 010 082 105 100 105 110 103 032 111 110 032 097 032 108 105 103 104 116 110 105 110 103 032 115 116 114 105 107 101 013 010 013 010 077 097 100 101 032 111 102 032 099 105 114 099 117 105 116 032 098 111 097 114 100 115 032 097 110 100 032 098 121 116 101 115 013 010 070 111 114 103 101 100 032 116 111 032 099 114 111 115 115 032 111 117 114 032 115 112 097 099 101 032 097 110 100 032 116 105 109 101 013 010 084 104 114 117 032 116 104 101 032 115 116 111 114 109 032 109 121 032 115 111 117 108 032 119 105 108 108 032 103 117 105 100 101 013 010 084 111 032 116 104 101 032 112 097 116 104 032 102 111 114 032 103 108 111 114 121 032 097 110 100 032 109 105 103 104 116 013 010 013 010 078 111 119 032 106 117 115 116 032 116 097 107 101 032 115 111 109 101 032 111 102 032 121 111 117 114 032 116 105 109 101 013 010 087 104 105 108 101 032 119 101 032 115 104 097 114 101 032 116 104 105 115 032 114 105 116 117 097 108 032 110 105 103 104 116 013 010 084 104 101 114 101 039 115 032 097 032 115 101 099 114 101 116 032 103 105 102 116 032 116 104 097 116 032 104 105 100 101 115 013 010 066 117 116 032 119 111 110 039 116 032 099 111 109 101 032 119 105 116 104 111 117 116 032 097 032 102 105 103 104 116 013 010 013 010 070 105 114 115 116 032 121 111 117 032 110 101 101 100 032 116 111 032 103 101 116 032 116 104 101 032 114 104 121 109 101 013 010 087 104 101 110 032 104 101 114 101 032 099 111 109 101 115 032 116 104 101 032 100 097 114 107 101 115 116 032 110 105 103 104 116 013 010 084 104 101 110 032 121 111 117 032 116 097 107 101 032 116 104 101 032 102 105 114 115 116 032 056 032 098 121 116 101 115 013 010 067 111 117 110 116 032 116 104 101 032 112 105 110 115 032 097 110 100 032 110 111 114 109 097 108 105 122 101 013 010 013 010 079 110 099 101 032 121 111 117 032 103 111 116 032 116 104 101 032 110 117 109 098 101 114 115 032 114 105 103 104 116 013 010 074 117 115 116 032 098 101 119 097 114 101 032 116 104 101 032 111 100 100 115 032 097 114 101 032 108 105 101 115 013 010 076 105 110 101 032 116 104 101 109 032 105 110 032 097 032 114 111 119 032 097 110 100 032 119 114 105 116 101 013 010 084 104 097 116 032 119 105 108 108 032 112 117 116 032 116 104 101 032 099 111 100 101 032 105 110 032 115 105 103 104 116 013 010 013 010 078 111 119 032 100 111 110 039 116 032 115 116 114 101 115 115 032 097 110 100 032 116 097 107 101 032 121 111 117 114 032 116 105 109 101 013 010 083 111 109 101 116 105 109 101 115 032 119 111 114 100 115 032 099 097 110 032 116 114 105 099 107 032 121 111 117 114 032 109 105 110 100 013 010 070 111 114 032 105 110 032 065 083 067 073 073 032 099 111 100 101 032 121 111 117 039 108 108 032 102 105 110 100 013 010 084 104 101 032 115 111 108 117 116 105 111 110 032 116 111 032 116 104 101 115 101 032 114 104 121 109 101 115

6k3teSVVjbc6AxRpghGZ6Zxq2igsO6ZTaw+7tC9y7pSWObcZBydHsuuykMaOtr/xKSD8uA7lVkurGPkv7vK469AOkWkJBS2IuiMU8ploCziWvffkhyiSS2MRUEp9aRlH/9gdGuR5tAfMZEz4zHjqkt0eAfDe6y8yozwYWxIHSMzYHzFe37e5FaA/XXYXBQEz5/i9SKSNJsms002OrJCljVcHl4jCD7m1y3o7hBuaonGKpc9iY3+s3DIdqRJ8nP2Fa5cJx/IkDoiVvsyAVkq/Aue3pd6Fub4uzB5nambt0JVYAIO+GORdRwiLiuDIA4EvrKLZYv6z8CKkHdqjfC8KJmTRFwa+kwm2pLuUwaLIGSI=

Analysis

Immediately I see 032 which is a space character in ASCII. At a glance, I also don’t see any lower than 32 or higher than 127. This most likely ASCII code. Using a little Javascript to decode it:

Which results in:

When the Moon will shed no light
With the Equinox close by
In the dark a spellware rise
Riding on a lightning strike

Made of circuit boards and bytes
Forged to cross our space and time
Thru the storm my soul will guide
To the path for glory and might

Now just take some of your time
While we share this ritual night
There's a secret gift that hides
But won't come without a fight

First you need to get the rhyme
When here comes the darkest night
Then you take the first 8 bytes
Count the pins and normalize

Once you got the numbers right
Just beware the odds are lies
Line them in a row and write
That will put the code in sight

Now don't stress and take your time
Sometimes words can trick your mind
For in ASCII code you'll find
The solution to these rhymes

After some Google searching I came across some hints on reddit. I’ll save you the trouble and condense them here:

It’s 3 parts: a word (a rhyme), 8 ASCII, and a number

You need to convert them all to the same “system”, the middle part is already converted.

The number refers to “CPU pins”

The odds should be considered differently than newer challenges, per ASCII code. Eg, 058 is even despite individual digits not being all even.

The total bytes of the key is 30, so 10 3 digit ASCII numbers.

I initially had the last part incorrect, but unknowingly with correct first two parts. I got frustrated enough to write some javascript to brute force the key given all these hints. I won’t share that code, but I will let you know that it could even be solved with brute force manually if you use those hints.

Once you solve it, the plaintext contains:

Success! CONGRATULATION!

You found the treasure of MBR Island and all you got is a link ████████████████████████████████████████

Beware this is a personal gift and sharing it would mean to spoil the fun to everyone else. PLEASE, don't be a lamer & enjoy the music.