soal

Fix the syntax error in the Python script to print the flag.
Download Python script

hint

• Are equality and assignment the same symbol?
• To view the file in the webshell, do: $ nano fixme2.py
• To exit nano, press Ctrl and x and follow the on-screen prompts.
• The str_xor function does not need to be reverse engineered for this challenge.

solve

wget https://artifacts.picoctf.net/c/5/fixme2.py

cat fixme2.py
###
import random

def str_xor(secret, key):
    #extend key to secret length
    new_key = key
    i = 0
    while len(new_key) < len(secret):
        new_key = new_key + key[i]
        i = (i + 1) % len(key)
    return "".join([chr(ord(secret_c) ^ ord(new_key_c)) for (secret_c,new_key_c) in zip(secret,new_key)])

flag_enc = chr(0x15) + chr(0x07) + chr(0x08) + chr(0x06) + chr(0x27) + chr(0x21) + chr(0x23) + chr(0x15) + chr(0x58) + chr(0x18) + chr(0x11) + chr(0x41) + chr(0x09) + chr(0x5f) + chr(0x1f) + chr(0x10) + chr(0x3b) + chr(0x1b) + chr(0x55) + chr(0x1a) + chr(0x34) + chr(0x5d) + chr(0x51) + chr(0x40) + chr(0x54) + chr(0x09) + chr(0x05) + chr(0x04) + chr(0x57) + chr(0x1b) + chr(0x11) + chr(0x31) + chr(0x5f) + chr(0x51) + chr(0x52) + chr(0x46) + chr(0x00) + chr(0x5f) + chr(0x5a) + chr(0x0b) + chr(0x19)

flag = str_xor(flag_enc, 'enkidu')

# Check that flag is not empty
if flag = "":
  print('String XOR encountered a problem, quitting.')
else:
  print('That is correct! Here\'s your flag: ' + flag)
'
###

python3 fixme2.py
#   File "/home/ariafatah/picoctf/s/f/fixme2.py", line 22
#     if flag = "":
#        ^^^^^^^^^
# SyntaxError: invalid syntax. Maybe you meant '==' or ':=' instead of '='?

## ubah = menjadi ==
tail fixme2.py -n 6
##
if flag == "":
  print('String XOR encountered a problem, quitting.')
else:
  print('That is correct! Here\'s your flag: ' + flag)
'
##

python3 fixme2.py
# That is correct! Here's your flag: picoCTF{3qu4l1ty_n0t_4551gnm3nt_4863e11b}

flag

picoCTF{3qu4l1ty_n0t_4551gnm3nt_4863e11b}