ReCurse

Description:

Found this nested zip in Morty’s PC. what is it that he is hiding?

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Stats:

150 points / 94 solvers

Solution:  

The challenge started with a .zip file which contained multiple zipped files within other zipped files as you can see in the following example:

My approach was rather brute: I unzipped one file in a folder and within the newly created folder, I repeated my actions. Here is the single bash command that I executed:

while true; do unzip $(ls \*.zip) -d $(ls \*.zip). && cd $(ls \*.zip).; done

Output:

The resulting working directory and the retrieved files:

w.zip is the last zip archive within the chain and requires a password to extract the archived text file.

From the working directory path I decided to strip all the extension names (.zip) and other unnecessary file names:

/home/nli/Desktop/otterctf/ReCurse/a.zip./H.zip./R.zip./0.zip./c.zip./H.zip./M.zip./6.zip./L.zip./y.zip./9.zip./3.zip./d.zip./3.zip./c.zip./u.zip./Z.zip./X.zip./h.zip./v.zip./d.zip./G.zip./l.zip./j.zip./Y.zip./W.zip./5.zip./p.zip./b.zip./W.zip./F.zip./s.zip./c.zip./2.zip./Z.zip./v.zip./c.zip./n.zip./N.zip./h.zip./b.zip./G.zip./U.zip./u.zip./b.zip./m.zip./V.zip./0.zip./L.zip./3.zip./N.zip./h.zip./b.zip./G.zip./U.zip./v.zip./M.zip./z.zip./k.zip./z.zip./N.zip./T.zip./M.zip./t.zip./M.zip./i.zip./1.zip./m.zip./Z.zip./W.zip./1.zip./h.zip./b.zip./G.zip./U.zip./t.zip./c.zip./2.zip./1.zip./h.zip./b.zip./G.zip./w.zip./t.zip./Y.zip./2.zip./x.zip./h.zip./d.zip./y.zip./1.zip./B.zip./c.zip./2.zip./l.zip./h.zip./b.zip./i.zip./1.zip./v.zip./d.zip./H.zip./R.zip./l.zip./c.zip./n.zip./M.zip./u.zip./Y.zip./X.zip./N.zip.

Output:

aHR0cHM6Ly93d3cuZXhvdGljYW5pbWFsc2ZvcnNhbGUubmV0L3NhbGUvMzkzNTMtMi1mZW1hbGUtc21hbGwtY2xhdy1Bc2lhbi1vdHRlcnMuYXN

After I decoded the above base64 string, I obtained the following link:

https://www.exoticanimalsforsale.net/sale/39353-2-female-small-claw-Asian-otters.as

I had to add the p letter to the end of the link in order to access the page:

https://www.exoticanimalsforsale.net/sale/39353-2-female-small-claw-Asian-otters.asp

By clicking on the User Review link, I was redirected to http://www.birple.com/users.asp?id=Brking1991@gmail.com&sid=175 website and page. At first, I thought that this was a dead end, but after multiple tries and failures I decided to use the leaked email (Brking1991@gmail.com) as the password for my last archive file:

Output:

Obtaining the flag:

flag{Recursion_1S_T3rribl3_AnD_1_H4t3_My_L1F3!!}