In this challenge, the list_files function is vulnerable to OS command injection attacks because of the usage of os.system(...). You are tasked with refactoring the code in unsafe_code.py so that:
list_files is no longer vulnerable to OS command injection attacks.list_files raises a ValueError when there is any error (including invalid syntax)list_files is changed to return a list of file names of a given directory.
You do not need to add or adjust any of the test cases in checker. You may write helper functions in unsafe_code.py,
but since you cannot adjust the test cases, do NOT adjust the original list_files function header. You must modify
unsafe_code.py in the /challenge directory, but there is a non-writable copy in /challenge/backup in case you need
to restore the original and start over.
The /challenge/some directory is there for the test cases, but you are unable to modify anything there.
All of the test cases in checker must pass for the Python executable to give you the flag. In this challenge,
you can read (but not write!) the checker script.
Make sure to run the checker script by doing the following in the /challenge directory:
$ ./checker