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376 lines
13 KiB
376 lines
13 KiB
"""
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Initializes a new transaction.
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"""
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import gc
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from apps.monero import misc, signing
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from apps.monero.layout import confirms
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from apps.monero.signing import RctType, RsigType
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from apps.monero.signing.state import State
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from apps.monero.xmr import crypto, monero
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if False:
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from trezor.messages.MoneroTransactionData import MoneroTransactionData
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from trezor.messages.MoneroTransactionRsigData import MoneroTransactionRsigData
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async def init_transaction(
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state: State, address_n: list, network_type: int, tsx_data: MoneroTransactionData
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):
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from apps.monero.signing import offloading_keys
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state.creds = await misc.get_creds(state.ctx, address_n, network_type)
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state.fee = state.fee if state.fee > 0 else 0
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state.tx_priv = crypto.random_scalar()
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state.tx_pub = crypto.scalarmult_base(state.tx_priv)
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state.mem_trace(1)
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# Ask for confirmation
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await confirms.require_confirm_transaction(
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state.ctx, tsx_data, state.creds.network_type
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)
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gc.collect()
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state.mem_trace(3)
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# Basic transaction parameters
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state.input_count = tsx_data.num_inputs
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state.output_count = len(tsx_data.outputs)
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state.output_change = tsx_data.change_dts
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state.mixin = tsx_data.mixin
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state.fee = tsx_data.fee
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state.account_idx = tsx_data.account
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# Ensure change is correct
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_check_change(state, tsx_data.outputs)
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# At least two outpus are required, this applies also for sweep txs
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# where one fake output is added. See _check_change for more info
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if state.output_count < 2:
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raise signing.NotEnoughOutputsError("At least two outputs are required")
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_check_rsig_data(state, tsx_data.rsig_data)
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_check_subaddresses(state, tsx_data.outputs)
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# Extra processing, payment id
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state.tx.version = 2 # current Monero transaction format (RingCT = 2)
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state.tx.unlock_time = tsx_data.unlock_time
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_process_payment_id(state, tsx_data)
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await _compute_sec_keys(state, tsx_data)
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gc.collect()
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# Iterative tx_prefix_hash hash computation
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state.tx_prefix_hasher.uvarint(state.tx.version)
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state.tx_prefix_hasher.uvarint(state.tx.unlock_time)
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state.tx_prefix_hasher.uvarint(state.input_count) # ContainerType, size
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state.mem_trace(10, True)
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# Final message hasher
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state.full_message_hasher.init(state.rct_type == RctType.Simple)
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state.full_message_hasher.set_type_fee(
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signing.get_monero_rct_type(state.rct_type, state.rsig_type), state.fee
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)
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# Sub address precomputation
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if tsx_data.account is not None and tsx_data.minor_indices:
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_precompute_subaddr(state, tsx_data.account, tsx_data.minor_indices)
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state.mem_trace(5, True)
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# HMACs all outputs to disallow tampering.
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# Each HMAC is then sent alongside the output
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# and trezor validates it.
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hmacs = []
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for idx in range(state.output_count):
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c_hmac = await offloading_keys.gen_hmac_tsxdest(
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state.key_hmac, tsx_data.outputs[idx], idx
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)
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hmacs.append(c_hmac)
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gc.collect()
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state.mem_trace(6)
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from trezor.messages.MoneroTransactionInitAck import MoneroTransactionInitAck
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from trezor.messages.MoneroTransactionRsigData import MoneroTransactionRsigData
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rsig_data = MoneroTransactionRsigData(offload_type=state.rsig_offload)
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return MoneroTransactionInitAck(hmacs=hmacs, rsig_data=rsig_data)
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def _check_subaddresses(state: State, outputs: list):
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"""
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Using subaddresses leads to a few poorly documented exceptions.
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Normally we set R=r*G (tx_pub), however for subaddresses this is equal to R=r*D
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to achieve the nice blockchain scanning property.
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Remember, that R is per-transaction and not per-input. It's all good if we have a
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single output or we have a single destination and the second output is our change.
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This is because although the R=r*D, we can still derive the change using our private view-key.
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In other words, calculate the one-time address as P = H(x*R)*G + Y (where X,Y is the change).
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However, this does not work for other outputs than change, because we do not have the
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recipient's view key, so we cannot use the same formula -- we need a new R.
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The solution is very straightforward -- we create additional `R`s and use the `extra`
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field to include them under the `ADDITIONAL_PUBKEYS` tag.
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See:
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- https://lab.getmonero.org/pubs/MRL-0006.pdf
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- https://github.com/monero-project/monero/pull/2056
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"""
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from apps.monero.xmr.addresses import classify_subaddresses
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# let's first figure out what kind of destinations we have
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num_stdaddresses, num_subaddresses, single_dest_subaddress = classify_subaddresses(
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outputs, state.change_address()
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)
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# if this is a single-destination transfer to a subaddress,
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# we set (override) the tx pubkey to R=r*D and no additional
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# tx keys are needed
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if num_stdaddresses == 0 and num_subaddresses == 1:
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state.tx_pub = crypto.scalarmult(
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crypto.decodepoint(single_dest_subaddress.spend_public_key), state.tx_priv
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)
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# if a subaddress is used and either standard address is as well
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# or more than one subaddress is used we need to add additional tx keys
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state.need_additional_txkeys = num_subaddresses > 0 and (
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num_stdaddresses > 0 or num_subaddresses > 1
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)
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state.mem_trace(4, True)
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def _get_primary_change_address(state: State):
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"""
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Computes primary change address for the current account index
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"""
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from trezor.messages.MoneroAccountPublicAddress import MoneroAccountPublicAddress
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D, C = monero.generate_sub_address_keys(
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state.creds.view_key_private, state.creds.spend_key_public, state.account_idx, 0
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)
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return MoneroAccountPublicAddress(
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view_public_key=crypto.encodepoint(C), spend_public_key=crypto.encodepoint(D)
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)
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def _check_rsig_data(state: State, rsig_data: MoneroTransactionRsigData):
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"""
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There are two types of monero ring confidential transactions:
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1. RCTTypeFull = 1 (used if num_inputs == 1)
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2. RCTTypeSimple = 2 (for num_inputs > 1)
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and four types of range proofs (set in `rsig_data.rsig_type`):
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1. RangeProofBorromean = 0
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2. RangeProofBulletproof = 1
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3. RangeProofMultiOutputBulletproof = 2
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4. RangeProofPaddedBulletproof = 3
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"""
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state.rsig_grouping = rsig_data.grouping
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if rsig_data.rsig_type == 0:
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state.rsig_type = RsigType.Borromean
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elif rsig_data.rsig_type in (1, 2, 3):
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state.rsig_type = RsigType.Bulletproof
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else:
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raise ValueError("Unknown rsig type")
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# unintuitively RctType.Simple is used for more inputs
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if state.input_count > 1 or state.rsig_type == RsigType.Bulletproof:
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state.rct_type = RctType.Simple
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else:
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state.rct_type = RctType.Full
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if state.rsig_type == RsigType.Bulletproof and state.output_count > 2:
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state.rsig_offload = True
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_check_grouping(state)
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def _check_grouping(state: State):
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acc = 0
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for x in state.rsig_grouping:
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if x is None or x <= 0:
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raise ValueError("Invalid grouping batch")
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acc += x
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if acc != state.output_count:
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raise ValueError("Invalid grouping")
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def _check_change(state: State, outputs: list):
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"""
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Check if the change address in state.output_change (from `tsx_data.outputs`) is
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a) among tx outputs
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b) is equal to our address
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The change output is in `tsx_data.change_dts`, but also has to be in `tsx_data.outputs`.
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This is what Monero does in its cold wallet signing protocol.
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In other words, these structures are built by Monero when generating unsigned transaction set
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and we do not want to modify this logic. We just translate the unsigned tx to the protobuf message.
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So, although we could probably optimize this by having the change output in `change_dts`
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only, we intentionally do not do so.
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"""
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from apps.monero.xmr.addresses import addr_eq, get_change_addr_idx
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change_index = get_change_addr_idx(outputs, state.output_change)
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change_addr = state.change_address()
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# if there is no change, there is nothing to check
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if change_addr is None:
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state.mem_trace("No change" if __debug__ else None)
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return
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"""
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Sweep tx is just one output and no change.
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To prevent recognition of such transactions another fake output is added
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that spends exactly 0 coins to a random address.
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See https://github.com/monero-project/monero/pull/1415
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"""
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if change_index is None and state.output_change.amount == 0 and len(outputs) == 2:
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state.mem_trace("Sweep tsx" if __debug__ else None)
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return
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found = False
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for out in outputs:
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if addr_eq(out.addr, change_addr):
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found = True
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break
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if not found:
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raise signing.ChangeAddressError("Change address not found in outputs")
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my_addr = _get_primary_change_address(state)
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if not addr_eq(my_addr, change_addr):
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raise signing.ChangeAddressError("Change address differs from ours")
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async def _compute_sec_keys(state: State, tsx_data: MoneroTransactionData):
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"""
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Generate master key H( H(TsxData || tx_priv) || rand )
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"""
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import protobuf
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from apps.monero.xmr.keccak_hasher import get_keccak_writer
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writer = get_keccak_writer()
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await protobuf.dump_message(writer, tsx_data)
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writer.write(crypto.encodeint(state.tx_priv))
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master_key = crypto.keccak_2hash(
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writer.get_digest() + crypto.encodeint(crypto.random_scalar())
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)
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state.key_hmac = crypto.keccak_2hash(b"hmac" + master_key)
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state.key_enc = crypto.keccak_2hash(b"enc" + master_key)
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def _precompute_subaddr(state: State, account: int, indices):
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"""
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Precomputes subaddresses for account (major) and list of indices (minors)
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Subaddresses have to be stored in encoded form - unique representation.
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Single point can have multiple extended coordinates representation - would not match during subaddress search.
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"""
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monero.compute_subaddresses(state.creds, account, indices, state.subaddresses)
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def _process_payment_id(state: State, tsx_data: MoneroTransactionData):
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"""
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Writes payment id to the `extra` field under the TX_EXTRA_NONCE = 0x02 tag.
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The second tag describes if the payment id is encrypted or not.
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If the payment id is 8 bytes long it implies encryption and
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therefore the TX_EXTRA_NONCE_ENCRYPTED_PAYMENT_ID = 0x01 tag is used.
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If it is not encrypted, we use TX_EXTRA_NONCE_PAYMENT_ID = 0x00.
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See:
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- https://github.com/monero-project/monero/blob/ff7dc087ae5f7de162131cea9dbcf8eac7c126a1/src/cryptonote_basic/tx_extra.h
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"""
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if not tsx_data.payment_id:
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return
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# encrypted payment id
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if len(tsx_data.payment_id) == 8:
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view_key_pub_enc = _get_key_for_payment_id_encryption(
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tsx_data.outputs, state.change_address()
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)
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view_key_pub = crypto.decodepoint(view_key_pub_enc)
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payment_id_encr = _encrypt_payment_id(
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tsx_data.payment_id, view_key_pub, state.tx_priv
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)
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extra_nonce = payment_id_encr
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extra_prefix = 1 # TX_EXTRA_NONCE_ENCRYPTED_PAYMENT_ID
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# plain text payment id
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elif len(tsx_data.payment_id) == 32:
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extra_nonce = tsx_data.payment_id
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extra_prefix = 0 # TX_EXTRA_NONCE_PAYMENT_ID
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else:
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raise ValueError("Payment ID size invalid")
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lextra = len(extra_nonce)
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if lextra >= 255:
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raise ValueError("Nonce could be 255 bytes max")
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# write it to extra
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extra_buff = bytearray(3 + lextra)
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extra_buff[0] = 2 # TX_EXTRA_NONCE
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extra_buff[1] = lextra + 1
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extra_buff[2] = extra_prefix
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extra_buff[3:] = extra_nonce
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state.tx.extra = extra_buff
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def _get_key_for_payment_id_encryption(destinations: list, change_addr=None):
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"""
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Returns destination address public view key to be used for
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payment id encryption.
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"""
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from apps.monero.xmr.addresses import addr_eq
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from trezor.messages.MoneroAccountPublicAddress import MoneroAccountPublicAddress
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addr = MoneroAccountPublicAddress(
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spend_public_key=crypto.NULL_KEY_ENC, view_public_key=crypto.NULL_KEY_ENC
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)
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count = 0
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for dest in destinations:
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if dest.amount == 0:
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continue
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if change_addr and addr_eq(dest.addr, change_addr):
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continue
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if addr_eq(dest.addr, addr):
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continue
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if count > 0:
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raise ValueError(
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"Destinations have to have exactly one output to support encrypted payment ids"
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)
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addr = dest.addr
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count += 1
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if addr.view_public_key == crypto.NULL_KEY_ENC:
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raise ValueError("Invalid key")
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return addr.view_public_key
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def _encrypt_payment_id(payment_id, public_key, secret_key):
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"""
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Encrypts payment_id hex.
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Used in the transaction extra. Only recipient is able to decrypt.
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"""
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derivation_p = crypto.generate_key_derivation(public_key, secret_key)
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derivation = bytearray(33)
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derivation = crypto.encodepoint_into(derivation, derivation_p)
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derivation[32] = 0x8B
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hash = crypto.cn_fast_hash(derivation)
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pm_copy = bytearray(payment_id)
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for i in range(8):
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pm_copy[i] ^= hash[i]
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return pm_copy
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