PM : Decrypt Message

PMDecryptMessage.py

import pgpy


mainKey = keychainVal['NoneProtection']
IVsize = 16

def decryptWithMainKey(encrypted):
    iv = encrypted[:IVsize]
    cipher = AES.new(mainKey, AES.MODE_CTR, initial_value=iv, nonce=b'')
    return cipher.decrypt(encrypted[IVsize:])

with open('group.ch.protonmail.protonmail.plist','rb') as p :
    prefplist = plistlib.load(p)


enc_val = prefplist['authKeychainStoreKeyProtectedWithMainKey']
dec_val = decryptWithMainKey(enc_val)

keychainStorePlist1 = ccl_bplist.load(BytesIO(dec_val))
keychainStorePlist = ccl_bplist.load(BytesIO(keychainStorePlist1[0]))
keychainStore = ccl_bplist.deserialise_NsKeyedArchiver(keychainStorePlist, parse_whole_structure=True)
privateKeyCoderKey = keychainStore['root']['NS.objects'][0]['privateKeyCoderKey']

key, _ = pgpy.PGPKey.from_blob(privateKeyCoderKey)
pwdKey = keychainStore['root']['NS.objects'][0]['AuthCredential.Password']

def decrypt_message(encm):
    if('-----BEGIN PGP MESSAGE-----') in encm:
        with key.unlock(pwdKey):
            assert key.is_unlocked
            message_from_blob = pgpy.PGPMessage.from_blob(encm)
            decm = key.decrypt(message_from_blob).message
            #print(decm)
            return html.unescape(decm.encode('cp1252', errors='ignore').decode('utf8', errors='ignore'))
    else:
        return encm