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Add a TX size check to Monero

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This isn't perfect yet should ensure the eventual TX is less than 100k bytes.
This commit is contained in:
Luke Parker 2023-03-12 03:54:30 -04:00
parent 36034c2f72
commit 41a285ddfa
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2 changed files with 20 additions and 3 deletions
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1
coins/monero/src/ringct/bulletproofs/mod.rs
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@ -37,6 +37,7 @@ impl Bulletproofs {
pub(crate) fn fee_weight(plus: bool, outputs: usize) -> usize {
let fields = if plus { 6 } else { 9 };
// TODO: Shouldn't this use u32/u64?
#[allow(non_snake_case)]
let mut LR_len = usize::try_from(usize::BITS - (outputs - 1).leading_zeros()).unwrap();
let padded_outputs = 1 << LR_len;

22
coins/monero/src/wallet/send/mod.rs
View file

@ -124,6 +124,8 @@ pub enum TransactionError {
TooManyOutputs,
#[error("too much data")]
TooMuchData,
#[error("too many inputs/too much arbitrary data")]
TooLargeTransaction,
#[error("not enough funds (in {0}, out {1})")]
NotEnoughFunds(u64, u64),
#[error("wrong spend private key")]
@ -303,8 +305,6 @@ impl SignableTransaction {
}
}
// TODO TX MAX SIZE
// If we don't have two outputs, as required by Monero, error
if (payments.len() == 1) && change_address.is_none() {
Err(TransactionError::NoChange)?;
@ -316,8 +316,24 @@ impl SignableTransaction {
// Calculate the extra length
let extra = Extra::fee_weight(outputs, has_payment_id, data.as_ref());
// This is a extremely heavy fee weight estimation which can only be trusted for two things
// 1) Ensuring we have enough for whatever fee we end up using
// 2) Ensuring we aren't over the max size
let estimated_tx_size = Transaction::fee_weight(protocol, inputs.len(), outputs, extra);
// The actual limit is half the block size, and for the minimum block size of 300k, that'd be
// 150k
// wallet2 will only create transactions up to 100k bytes however
const MAX_TX_SIZE: usize = 100_000;
// This uses the weight (estimated_tx_size) despite the BP clawback
// The clawback *increases* the weight, so this will over-estimate, yet it's still safe
if estimated_tx_size >= MAX_TX_SIZE {
Err(TransactionError::TooLargeTransaction)?;
}
// Calculate the fee.
let fee = fee_rate.calculate(Transaction::fee_weight(protocol, inputs.len(), outputs, extra));
let fee = fee_rate.calculate(estimated_tx_size);
// Make sure we have enough funds
let in_amount = inputs.iter().map(|input| input.commitment().amount).sum::<u64>();