Implement noadjustfee, feebumpindex and v parameters for payjoin

BTCPayServer.Tests/PayJoinTests.cs

@@ -28,6 +28,7 @@ using NBitcoin.Altcoins;
 using NBitcoin.Payment;
 using NBitpayClient;
 using NBXplorer.Models;
+using Newtonsoft.Json.Linq;
 using OpenQA.Selenium;
 using Xunit;
 using Xunit.Abstractions;
@@ -587,6 +588,14 @@ namespace BTCPayServer.Tests
                 //Let's start the harassment
                 invoice = receiverUser.BitPay.CreateInvoice(
                     new Invoice() {Price = 0.02m, Currency = "BTC", FullNotifications = true});
+                // Bad version should throw incorrect version
+                var endpoint = TestAccount.GetPayjoinEndpoint(invoice, btcPayNetwork.NBitcoinNetwork);
+                var response = await tester.PayTester.HttpClient.PostAsync(endpoint.AbsoluteUri + "?v=2",
+                    new StringContent("", Encoding.UTF8, "text/plain"));
+                Assert.False(response.IsSuccessStatusCode);
+                var error = JObject.Parse(await response.Content.ReadAsStringAsync());
+                Assert.Equal("version-unsupported", error["errorCode"].Value<string>());
+                Assert.Equal(1, ((JArray)error["supported"]).Single().Value<int>());
 
                 var parsedBip21 = new BitcoinUrlBuilder(invoice.CryptoInfo.First().PaymentUrls.BIP21,
                     tester.ExplorerClient.Network.NBitcoinNetwork);
@@ -665,6 +674,7 @@ namespace BTCPayServer.Tests
                 //Attempt 2: Create two transactions using different inputs and send them to the same invoice. 
                 //Result: Second Tx should be rejected. 
                 var Invoice1Coin1ResponseTx = await senderUser.SubmitPayjoin(invoice, Invoice1Coin1, btcPayNetwork);
+
                 await senderUser.SubmitPayjoin(invoice, Invoice1Coin1, btcPayNetwork, "already-paid");
                 var contributedInputsInvoice1Coin1ResponseTx =
                     Invoice1Coin1ResponseTx.Inputs.Where(txin => coin.OutPoint != txin.PrevOut);

BTCPayServer.Tests/TestAccount.cs

@@ -393,7 +393,7 @@ namespace BTCPayServer.Tests
             return response;
         }
 
-        private static Uri GetPayjoinEndpoint(Invoice invoice, Network network)
+        public static Uri GetPayjoinEndpoint(Invoice invoice, Network network)
         {
             var parsedBip21 = new BitcoinUrlBuilder(
                 invoice.CryptoInfo.First(c => c.CryptoCode == network.NetworkSet.CryptoCode).PaymentUrls.BIP21,

BTCPayServer/Payments/PayJoin/PayJoinEndpointController.cs

@@ -23,6 +23,7 @@ using NBXplorer.DerivationStrategy;
 using System.Diagnostics.CodeAnalysis;
 using BTCPayServer.Data;
 using NBitcoin.DataEncoders;
+using Amazon.S3.Model;
 
 namespace BTCPayServer.Payments.PayJoin
 {
@@ -115,8 +116,20 @@ namespace BTCPayServer.Payments.PayJoin
         [EnableCors(CorsPolicies.All)]
         [MediaTypeConstraint("text/plain")]
         [RateLimitsFilter(ZoneLimits.PayJoin, Scope = RateLimitsScope.RemoteAddress)]
-        public async Task<IActionResult> Submit(string cryptoCode)
+        public async Task<IActionResult> Submit(string cryptoCode,
+            bool noadjustfee = false,
+            int feebumpindex = -1,
+            int v = 1)
         {
+            if (v != 1)
+            {
+                return BadRequest(new JObject
+                {
+                    new JProperty("errorCode", "version-unsupported"),
+                    new JProperty("supported", new JArray(1)),
+                    new JProperty("message", "This version of payjoin is not supported.")
+                });
+            }
             var network = _btcPayNetworkProvider.GetNetwork<BTCPayNetwork>(cryptoCode);
             if (network == null)
             {
@@ -146,26 +159,28 @@ namespace BTCPayServer.Payments.PayJoin
             Transaction originalTx = null;
             FeeRate originalFeeRate = null;
             bool psbtFormat = true;
-            if (!PSBT.TryParse(rawBody, network.NBitcoinNetwork, out var psbt))
+
+            if (PSBT.TryParse(rawBody, network.NBitcoinNetwork, out var psbt))
+            {
+                if (!psbt.IsAllFinalized())
+                    return BadRequest(CreatePayjoinError("psbt-not-finalized", "The PSBT should be finalized"));
+                originalTx = psbt.ExtractTransaction();
+            }
+            // BTCPay Server implementation support a transaction instead of PSBT
+            else
             {
                 psbtFormat = false;
                 if (!Transaction.TryParse(rawBody, network.NBitcoinNetwork, out var tx))
                     return BadRequest(CreatePayjoinError("invalid-format", "invalid transaction or psbt"));
                 originalTx = tx;
                 psbt = PSBT.FromTransaction(tx, network.NBitcoinNetwork);
-                psbt = (await explorer.UpdatePSBTAsync(new UpdatePSBTRequest() {PSBT = psbt})).PSBT;
+                psbt = (await explorer.UpdatePSBTAsync(new UpdatePSBTRequest() { PSBT = psbt })).PSBT;
                 for (int i = 0; i < tx.Inputs.Count; i++)
                 {
                     psbt.Inputs[i].FinalScriptSig = tx.Inputs[i].ScriptSig;
                     psbt.Inputs[i].FinalScriptWitness = tx.Inputs[i].WitScript;
                 }
             }
-            else
-            {
-                if (!psbt.IsAllFinalized())
-                    return BadRequest(CreatePayjoinError("psbt-not-finalized", "The PSBT should be finalized"));
-                originalTx = psbt.ExtractTransaction();
-            }
 
             async Task BroadcastNow()
             {
@@ -173,8 +188,6 @@ namespace BTCPayServer.Payments.PayJoin
             }
 
             var sendersInputType = psbt.GetInputsScriptPubKeyType();
-            if (sendersInputType is null)
-                return BadRequest(CreatePayjoinError("unsupported-inputs", "Payjoin only support segwit inputs (of the same type)"));
             if (psbt.CheckSanity() is var errors && errors.Count != 0)
             {
                 return BadRequest(CreatePayjoinError("insane-psbt", $"This PSBT is insane ({errors[0]})"));
@@ -242,7 +255,7 @@ namespace BTCPayServer.Payments.PayJoin
                     //this should never happen, unless the store owner changed the wallet mid way through an invoice
                     return StatusCode(500, CreatePayjoinError("unavailable", $"This service is unavailable for now"));
                 }
-                if (sendersInputType != receiverInputsType)
+                if (sendersInputType is ScriptPubKeyType t && t != receiverInputsType)
                 {
                     return StatusCode(503,
                         CreatePayjoinError("out-of-utxos",
@@ -331,6 +344,10 @@ namespace BTCPayServer.Payments.PayJoin
             var ourNewOutput = newTx.Outputs[originalPaymentOutput.Index];
             HashSet<TxOut> isOurOutput = new HashSet<TxOut>();
             isOurOutput.Add(ourNewOutput);
+            TxOut preferredFeeBumpOutput = feebumpindex >= 0
+                                            && feebumpindex < newTx.Outputs.Count
+                                            && !isOurOutput.Contains(newTx.Outputs[feebumpindex])
+                                            ? newTx.Outputs[feebumpindex] : null;
             var rand = new Random();
             int senderInputCount = newTx.Inputs.Count;
             foreach (var selectedUTXO in selectedUTXOs.Select(o => o.Value))
@@ -398,7 +415,7 @@ namespace BTCPayServer.Payments.PayJoin
             Money expectedFee = txBuilder.EstimateFees(newTx, originalFeeRate);
             Money actualFee = newTx.GetFee(txBuilder.FindSpentCoins(newTx));
             Money additionalFee = expectedFee - actualFee;
-            if (additionalFee > Money.Zero)
+            if (additionalFee > Money.Zero && !noadjustfee)
             {
                 // If the user overpaid, taking fee on our output (useful if sender dump a full UTXO for privacy)
                 for (int i = 0; i < newTx.Outputs.Count && additionalFee > Money.Zero && due < Money.Zero; i++)
@@ -418,6 +435,9 @@ namespace BTCPayServer.Payments.PayJoin
                 // The rest, we take from user's change
                 for (int i = 0; i < newTx.Outputs.Count && additionalFee > Money.Zero; i++)
                 {
+                    if (preferredFeeBumpOutput is TxOut &&
+                        preferredFeeBumpOutput != newTx.Outputs[i])
+                        continue;
                     if (!isOurOutput.Contains(newTx.Outputs[i]))
                     {
                         var outputContribution = Money.Min(additionalFee, newTx.Outputs[i].Value);
@@ -493,6 +513,7 @@ namespace BTCPayServer.Payments.PayJoin
                     .ToDictionary(pair => pair.Key, pair => pair.Value)
             });
 
+            // BTCPay Server support PSBT set as hex
             if (psbtFormat && HexEncoder.IsWellFormed(rawBody))
             {
                 return Ok(newPsbt.ToHex());
@@ -501,6 +522,7 @@ namespace BTCPayServer.Payments.PayJoin
             {
                 return Ok(newPsbt.ToBase64());
             }
+            // BTCPay Server should returns transaction if received transaction
             else
                 return Ok(newTx.ToHex());
         }

BTCPayServer/Services/PayjoinClient.cs

@@ -6,9 +6,7 @@ using System.Net.Http;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
-using BTCPayServer.Payments.Changelly.Models;
 using Google.Apis.Http;
-using Microsoft.WindowsAzure.Storage.Queue.Protocol;
 using NBitcoin;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
@@ -265,7 +263,8 @@ namespace BTCPayServer.Services
         OutOfUTXOS,
         NotEnoughMoney,
         InsanePSBT,
-        VersionUnsupported
+        VersionUnsupported,
+        NeedUTXOInformation
     }
     public class PayjoinReceiverException : PayjoinException
     {
@@ -282,6 +281,7 @@ namespace BTCPayServer.Services
                 "not-enough-money" => PayjoinReceiverWellknownErrors.NotEnoughMoney,
                 "insane-psbt" => PayjoinReceiverWellknownErrors.InsanePSBT,
                 "version-unsupported" => PayjoinReceiverWellknownErrors.VersionUnsupported,
+                "need-utxo-information" => PayjoinReceiverWellknownErrors.NeedUTXOInformation,
                 _ => null
             };
         }
@@ -310,6 +310,7 @@ namespace BTCPayServer.Services
                 "not-enough-money" => "The receiver added some inputs but could not bump the fee of the payjoin proposal.",
                 "insane-psbt" => "Some consistency check on the PSBT failed.",
                 "version-unsupported" => "This version of payjoin is not supported.",
+                "need-utxo-information" => "The witness UTXO or non witness UTXO is missing",
                 _ => "Unknown error"
             };
         }