VPN Shared Secret decoder for networkConnect files

vpn_shared_secret_decoder.py

#!/usr/bin/python

# Decoder for the ExportedSharedSecret values stored in .networkConnect files
# Tested with .networkConnect files created in Mac OS X 10.10
#
# Author: Martin Rakhmanov, http://jimmers.info
#
# Example invocation and output:
#
# python vpn_shared_secret_decoder.py TLthF+e88vwmAYhK
# Shared Secret: 12345

import sys
import base64

if len(sys.argv) != 2:
    print("Provide ExportedSharedSecret value from .networkConnect file")
    sys.exit(1)

cryptotext = base64.b64decode(sys.argv[1])

decryption_key = [0x7d, 0x89, 0x52, 0x23, 0xd2, 0xbc, 0xdd, 0xea, 0xa3, 0xb9, 0x1f]

i = 0
cleartext = ""

for ch in cryptotext:
    b = ord(ch) ^ decryption_key[i]
    if b == 0x00:
        break
    cleartext += chr(b)
    i += 1
    i = i % len(decryption_key)

print("Shared Secret: %s" %(cleartext))

What is the algorithm to generate the cryptotext from the clear text?

Inspired by your code, and given the fact that if A ^ B = C, then C ^ B = A, or C ^ A = B. I wrote the following code attempting to generate the crypto text. However, I only get similar crypto code. It seems Apple put some rand data at the tail of the crypto text. So do you have idea how to generate exactly the same crypto code? Thanks.

#!/usr/bin/python

import sys
import base64

cleartext = sys.argv[1]

decryption_key = [0x7d, 0x89, 0x52, 0x23, 0xd2, 0xbc, 0xdd, 0xea, 0xa3, 0xb9, 0x1f]

i = 0
cryptotext = ""

for ch in cleartext:
    b = ord(ch) ^ decryption_key[i]
    cryptotext += chr(b)
    i += 1
    i = i % len(decryption_key)

result = base64.b64encode(cryptotext)


print("Shared Secret: %s" %(result))

It seems the clear text string's length needs to be a multiple of 12. Filling the remaining characters with null bytes worked for me.

#!/usr/bin/python

import sys
import base64

cleartext = sys.argv[1]

while len(cleartext) % 12 != 0:
    cleartext += chr(0x00)

decryption_key = [0x7d, 0x89, 0x52, 0x23, 0xd2, 0xbc, 0xdd, 0xea, 0xa3, 0xb9, 0x1f]

i = 0
cryptotext = ""

for ch in cleartext:
    b = ord(ch) ^ decryption_key[i]
    cryptotext += chr(b)
    i += 1
    i = i % len(decryption_key)

result = base64.b64encode(cryptotext)


print("Shared Secret: %s" %(result))