List strings which may appear when a target string is doubly base 64-encoded

double_reverse_base64.py

#!/usr/bin/python
import base64
import sys
input = sys.argv[1]

def get_combinations(s):
 return [base64.urlsafe_b64encode('a'*i + s)[2*i:-4] for i in range(3)]

for x in [get_combinations(intermediate) for intermediate in get_combinations(sys.argv[1])]:
 for y in x:
  print(y)

Sample usage:

grep -rf <(./double_reverse_base64.py search_string) my_directory

Nice!