Recovering FIBS passwords from Javafibs Preferences

[inim]

From time to time there is a request to recover a forgotten FIBS password from a JavaFIBS 2001 preferences file. Due to some obfuscation (not really encryption) you can not easily recover it. So I decided to document the algorithm in the form of a small Python code snippet. In the hope that this is useful - no warranty, no copyright. Written 2017 by Ingo Macherius and hereby released to the public domain. You find the preferences file needed in the JavaFibs2001 installation directory subfolder "user/yourfibsnick/preferences".

#!/usr/bin/env python

from sys import argv
import struct

if len(argv) != 2:
    print("Usage: " + argv[0] + " file")
    print("'file' is the name of a JavaFibs 2001 preferences file.")
    print("The decrypted password from the file is printed to stdout.")
    exit

filename = argv[1];
print ("Attempting to open Javafibs 2001 preferences file " + filename + " as binary file.")
prefs = open(filename, "rb");

# read in magic file marker (ignored, must be 1.011) and length of password
magic, passwordlength = struct.unpack('>fi', prefs.read(2*4))
print ("File open succeeded.")

# read and decrypt password char by char and build string
password = ""
for i in range (0, passwordlength):
    encrypted = prefs.read(4);
    decrypted = chr(int(struct.unpack('>f', encrypted)[0]))
    password += decrypted

print ("Your FIBS password recovered from it is: '" + password + "'")