def _process_payment_id(state: State, tsx_data: MoneroTransactionData):
"""
Writes payment id to the `extra` field under the TX_EXTRA_NONCE = 0x02 tag.
The second tag describes if the payment id is encrypted or not.
If the payment id is 8 bytes long it implies encryption and
therefore the TX_EXTRA_NONCE_ENCRYPTED_PAYMENT_ID = 0x01 tag is used.
If it is not encrypted, we use TX_EXTRA_NONCE_PAYMENT_ID = 0x00.
Since Monero release 0.13 all 2 output payments have encrypted payment ID
to make BC more uniform.
See:
- https://github.com/monero-project/monero/blob/ff7dc087ae5f7de162131cea9dbcf8eac7c126a1/src/cryptonote_basic/tx_extra.h
"""
# encrypted payment id / dummy payment ID
view_key_pub_enc = None
if not tsx_data.payment_id or len(tsx_data.payment_id) == 8:
view_key_pub_enc = _get_key_for_payment_id_encryption(
tsx_data, state.change_address(), state.client_version > 0)
if not tsx_data.payment_id:
return
elif len(tsx_data.payment_id) == 8:
view_key_pub = crypto.decodepoint(view_key_pub_enc)
payment_id_encr = _encrypt_payment_id(tsx_data.payment_id,
view_key_pub, state.tx_priv)
extra_nonce = payment_id_encr
extra_prefix = 1 # TX_EXTRA_NONCE_ENCRYPTED_PAYMENT_ID
# plain text payment id
elif len(tsx_data.payment_id) == 32:
extra_nonce = tsx_data.payment_id
extra_prefix = 0 # TX_EXTRA_NONCE_PAYMENT_ID
else:
raise ValueError("Payment ID size invalid")
lextra = len(extra_nonce)
if lextra >= 255:
raise ValueError("Nonce could be 255 bytes max")
# write it to extra
extra_buff = bytearray(3 + lextra)
extra_buff[0] = 2 # TX_EXTRA_NONCE
extra_buff[1] = lextra + 1
extra_buff[2] = extra_prefix
extra_buff[3:] = extra_nonce
state.extra_nonce = extra_buff
def _check_change(state: State,
outputs: List[MoneroTransactionDestinationEntry]):
"""
Check if the change address in state.output_change (from `tsx_data.outputs`) is
a) among tx outputs
b) is equal to our address
The change output is in `tsx_data.change_dts`, but also has to be in `tsx_data.outputs`.
This is what Monero does in its cold wallet signing protocol.
In other words, these structures are built by Monero when generating unsigned transaction set
and we do not want to modify this logic. We just translate the unsigned tx to the protobuf message.
So, although we could probably optimize this by having the change output in `change_dts`
only, we intentionally do not do so.
"""
from apps.monero.xmr.addresses import addr_eq, get_change_addr_idx
change_index = get_change_addr_idx(outputs, state.output_change)
change_addr = state.change_address()
# if there is no change, there is nothing to check
if change_addr is None:
state.mem_trace("No change" if __debug__ else None)
return
"""
Sweep tx is just one output and no change.
To prevent recognition of such transactions another fake output is added
that spends exactly 0 coins to a random address.
See https://github.com/monero-project/monero/pull/1415
"""
if change_index is None and state.output_change.amount == 0 and len(
outputs) == 2:
state.mem_trace("Sweep tsx" if __debug__ else None)
return
found = False
for out in outputs:
if addr_eq(out.addr, change_addr):
found = True
break
if not found:
raise signing.ChangeAddressError("Change address not found in outputs")
my_addr = _get_primary_change_address(state)
if not addr_eq(my_addr, change_addr):
raise signing.ChangeAddressError("Change address differs from ours")
def _check_subaddresses(
state: State,
outputs: list[MoneroTransactionDestinationEntry]) -> None:
"""
Using subaddresses leads to a few poorly documented exceptions.
Normally we set R=r*G (tx_pub), however for subaddresses this is equal to R=r*D
to achieve the nice blockchain scanning property.
Remember, that R is per-transaction and not per-input. It's all good if we have a
single output or we have a single destination and the second output is our change.
This is because although the R=r*D, we can still derive the change using our private view-key.
In other words, calculate the one-time address as P = H(x*R)*G + Y (where X,Y is the change).
However, this does not work for other outputs than change, because we do not have the
recipient's view key, so we cannot use the same formula -- we need a new R.
The solution is very straightforward -- we create additional `R`s and use the `extra`
field to include them under the `ADDITIONAL_PUBKEYS` tag.
See:
- https://lab.getmonero.org/pubs/MRL-0006.pdf
- https://github.com/monero-project/monero/pull/2056
"""
from apps.monero.xmr.addresses import classify_subaddresses
# let's first figure out what kind of destinations we have
num_stdaddresses, num_subaddresses, single_dest_subaddress = classify_subaddresses(
outputs, state.change_address())
# if this is a single-destination transfer to a subaddress,
# we set (override) the tx pubkey to R=r*D and no additional
# tx keys are needed
if num_stdaddresses == 0 and num_subaddresses == 1:
state.tx_pub = crypto.scalarmult_into(
None,
crypto_helpers.decodepoint(
single_dest_subaddress.spend_public_key),
state.tx_priv,
)
# if a subaddress is used and either standard address is as well
# or more than one subaddress is used we need to add additional tx keys
state.need_additional_txkeys = num_subaddresses > 0 and (
num_stdaddresses > 0 or num_subaddresses > 1)
state.mem_trace(4, True)