DEFCON 2020 Quals Fungez(z)

Fungez

Race FUNGEZ_IOCTL_START to bypass befunge_check

Fungezz

OOO{trappedinvYP1ctlxrhdrnfctxhrldrlfhdxtxdtnfcftcdlnhdxnlhrcxcflxtr}

You should not follow the path of trappedinhell.

Find the branch to trigger the backdoor (a 'p' command) to modify the map at runtime. Change the direction '<' to 'v' then you will reach the second stage of the game, which is a sudoku challenge.

The second stage was accidently exposed to the trappedinhell path due to an implementation bug (see comments in gen.py). It made the challenge broing, so we disabled the shortcut in the old map and released a new one.

There are 3 teams solved the real one during the ctf. Many other teams stopped at the trivial one and started complaining.

Most people only accept easy challenges that are within their capability :)

References

1. gen.py design and errors

2. solve.py quick solution

3. deopt.py script to help you reverse and analyze

4. map* maps in different optimization levels