Fixes payment ID problem

payment_id_fix.py

# pip install monero_agent>=1.7.6

import binascii
import json
import requests

from monero_glue.xmr import crypto
from monero_serialize.xmrserialize import load_uvarint_b, uvarint_size

# Set your values here:
daemon_addr = 'opennode.xmr-tw.org:18089'
txid = '2331873ba8d7d2b935e2d89b36ebe2c031a2f785fc799a4fb4641385c098c66d'
viewkey = 'f27ab2ae6c9849601b15d55da305f02b6a4e373432f280a78263eb137ca36603'  # viewkey command in monero-wallet-cli, the private (secret) part


def parse_payment_id(extra):
    offset = 0
    extra = bytearray(extra)
    pub_key = None
    payment_id = None
    nonce = None

    while offset < len(extra):
        tag = extra[offset]
        offset += 1

        if tag == 0x1:  # pubkey
            pub_key = extra[offset : offset + 32]
            offset += 32

        elif tag == 0x2:  # nonce
            ln = load_uvarint_b(extra[offset:])
            offset += uvarint_size(ln)
            nonce = extra[offset : offset + ln]
            offset += ln

        elif tag == 0x4:  # additionals
            ln = load_uvarint_b(extra[offset:])
            offset += uvarint_size(ln) + 32 * ln

        else:
            raise ValueError('Not Trezor transaction')

    if nonce and len(nonce) == 9 and nonce[0] == 1:
        payment_id = nonce[1:]

    if not payment_id or not pub_key:
        raise ValueError('Payment ID or pubkey not found in TX')

    return pub_key, payment_id


def encrypt_payment_id(payment_id, public_key, secret_key, tag):
    derivation_p = crypto.generate_key_derivation(public_key, secret_key)
    derivation = bytearray(33)
    derivation = crypto.encodepoint_into(derivation, derivation_p)
    derivation[32] = tag  # ENCRYPTED_PAYMENT_ID_TAIL
    hash = crypto.cn_fast_hash(derivation)
    pm_copy = bytearray(payment_id)
    for i in range(8):
        pm_copy[i] ^= hash[i]
    return pm_copy


def fix_payment_id(daemon_addr, txid, viewkey):
    res = requests.post('http://%s/gettransactions' % daemon_addr, json={"txs_hashes":[txid], "decode_as_json": True})
    txjs = json.loads([x['as_json'] for x in res.json()['txs'] if x['tx_hash'] == txid][0])

    extra = bytearray(txjs['extra'])
    pub_bin, payment_id = parse_payment_id(extra)
    pub = crypto.decodepoint(pub_bin)
    viewkey_bin = binascii.unhexlify(viewkey)
    viewkey_sec = crypto.decodeint(viewkey_bin)

    return encrypt_payment_id(payment_id, pub, viewkey_sec, 0x8b)


if __name__ == '__main__':
    fixed = fix_payment_id(daemon_addr, txid, viewkey)
    print('Fixed: %s for txid %s' % (binascii.hexlify(fixed), txid))