Dirt

Overview

Overall difficulty for me (From 1-10 stars): ★☆☆☆☆☆☆☆☆☆
Challenge static score: 50

Background

Find the flag

In the challenge’s description, we can download an attachment. Let’s download it:

┌[root♥siunam]-(~/ctf/KnightCTF-2023/Misc/Dirt)-[2023.01.21|13:42:50(HKT)]
└> file dirt.zip   
dirt.zip: Zip archive data, at least v1.0 to extract, compression method=store

It’s a zip archive file. We can unzip that:

┌[root♥siunam]-(~/ctf/KnightCTF-2023/Misc/Dirt)-[2023.01.21|13:42:52(HKT)]
└> unzip dirt.zip 
Archive:  dirt.zip
   creating: challenge/
   creating: challenge/}/
   creating: challenge/}/s/
   creating: challenge/}/s/r/
   creating: challenge/}/s/r/3/
   creating: challenge/}/s/r/3/d/
   creating: challenge/}/s/r/3/d/l/
   creating: challenge/}/s/r/3/d/l/0/
   creating: challenge/}/s/r/3/d/l/0/f/
   creating: challenge/}/s/r/3/d/l/0/f/_/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/n/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/n/1/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/n/1/_/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/n/1/_/s/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/n/1/_/s/r/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/n/1/_/s/r/3/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/n/1/_/s/r/3/d/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/n/1/_/s/r/3/d/l/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/n/1/_/s/r/3/d/l/0/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/n/1/_/s/r/3/d/l/0/f/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/n/1/_/s/r/3/d/l/0/f/{/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/n/1/_/s/r/3/d/l/0/f/{/F/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/n/1/_/s/r/3/d/l/0/f/{/F/T/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/n/1/_/s/r/3/d/l/0/f/{/F/T/C/
   creating: challenge/}/s/r/3/d/l/0/f/_/3/d/1/5/n/1/_/s/r/3/d/l/0/f/{/F/T/C/K/

Oh! Looks like we found the flag??

}sr3dl0f_3d15n1_sr3dl0f{FTCK

However, it looks like it’s reversed. Let’s use rev to reverse it back:

┌[root♥siunam]-(~/ctf/KnightCTF-2023)-[2023.01.21|13:44:58(HKT)]
└> echo '}sr3dl0f_3d15n1_sr3dl0f{FTCK' | rev
KCTF{f0ld3rs_1n51d3_f0ld3rs}

Nice! We found the flag!

Flag: KCTF{f0ld3rs_1n51d3_f0ld3rs}

Conclusion

What we’ve learned:

Unziping File & Reversing Strings