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Relax requirement on mixed input types #3

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merged 1 commit into from
Jan 14, 2025
Merged

Relax requirement on mixed input types #3

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29 changes: 4 additions & 25 deletions BIP78.Sender/PayjoinClient.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,6 @@ public async Task<PSBT> RequestPayjoin(BitcoinUrlBuilder bip21, IPayjoinWallet w
if (signedPSBT.IsAllFinalized())
throw new InvalidOperationException("The original PSBT should not be finalized.");
var optionalParameters = new PayjoinClientParameters();
var inputScriptType = wallet.ScriptPubKeyType;
var paymentScriptPubKey = bip21.Address?.ScriptPubKey;
var changeOutput = signedPSBT.Outputs.CoinsFor(wallet, wallet.AccountKey, wallet.RootedKeyPath)
.Where(o => o.ScriptPubKey != paymentScriptPubKey)
Expand All @@ -56,7 +55,7 @@ public async Task<PSBT> RequestPayjoin(BitcoinUrlBuilder bip21, IPayjoinWallet w
optionalParameters.MaxAdditionalFeeContribution = MaxFeeBumpContribution is null
?
// By default, we want to keep same fee rate and a single additional input
originalFeeRate.GetFee(GetVirtualSize(inputScriptType))
originalFeeRate.GetFee(110)
: MaxFeeBumpContribution;
if (MinimumFeeRate is FeeRate v)
optionalParameters.MinFeeRate = v;
Expand Down Expand Up @@ -140,9 +139,6 @@ public async Task<PSBT> RequestPayjoin(BitcoinUrlBuilder bip21, IPayjoinWallet w
throw new PayjoinSenderException(
"The receiver did not specify non_witness_utxo or witness_utxo for one of their inputs");
sequences.Add(proposedTxIn.Sequence);
// Verify that the payjoin proposal did not introduced mixed input's type.
if (inputScriptType != proposedPSBTInput.GetInputScriptPubKeyType())
throw new PayjoinSenderException("Mixed input type detected in the proposal");
}
}

Expand Down Expand Up @@ -187,9 +183,9 @@ public async Task<PSBT> RequestPayjoin(BitcoinUrlBuilder bip21, IPayjoinWallet w
// Make sure the actual contribution is only paying fee
if (actualContribution > additionalFee)
throw new PayjoinSenderException("The actual contribution is not only paying fee");
// Make sure the actual contribution is only paying for fee incurred by additional inputs
var additionalInputsCount = proposalGlobalTx.Inputs.Count - originalGlobalTx.Inputs.Count;
if (actualContribution > originalFeeRate.GetFee(GetVirtualSize(inputScriptType)) *
// This assumes an additional input can be up to 110 bytes.
var additionalInputsCount = proposalGlobalTx.Inputs.Count - originalGlobalTx.Inputs.Count;
if (actualContribution > originalFeeRate.GetFee(110) *
additionalInputsCount)
throw new PayjoinSenderException(
"The actual contribution is not only paying for additional inputs");
Expand Down Expand Up @@ -233,23 +229,6 @@ public async Task<PSBT> RequestPayjoin(BitcoinUrlBuilder bip21, IPayjoinWallet w
return proposal;
}

private int GetVirtualSize(ScriptPubKeyType? scriptPubKeyType)
{
switch (scriptPubKeyType)
{
case ScriptPubKeyType.Legacy:
return 148;
case ScriptPubKeyType.Segwit:
return 68;
case ScriptPubKeyType.SegwitP2SH:
return 91;
case ScriptPubKeyType.TaprootBIP86:
return 58;
default:
return 110;
}
}

private static PSBT CreateOriginalPSBT(PSBT signedPSBT)
{
var original = signedPSBT.Clone();
Expand Down
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