ctf1
=== Originality === Not sure if the program is what it was intended ...
=== Difficulty === Very easy: just provide 0 as the first argument, and function f1 will be called, granting us a shell.
Similar, we can link /bin/bash1 to /bin/bash, and call similarly with the first argument 1.
If fns[] would also have f3, we could also gain shell using using a carefully constructed string, with / in positions 1,5,10,11, something similar to //bin/././//bash
=== Relevance === Code review