From eb166a7f9b0a0020695a78162111e4654eea0002 Mon Sep 17 00:00:00 2001
From: Jamie Holdstock <jholdstock@decred.org>
Date: Fri, 22 Dec 2023 11:24:27 +0000
Subject: [PATCH] pool: Handle (nil,nil) response from dcrd.GetTxOut

---
 pool/hub.go             |  6 ++++--
 pool/paymentmgr.go      | 10 ++++++++--
 pool/paymentmgr_test.go | 15 +++++++++++++++
 3 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/pool/hub.go b/pool/hub.go
index b7df9107..88468cd8 100644
--- a/pool/hub.go
+++ b/pool/hub.go
@@ -108,9 +108,11 @@ type WalletConnection interface {
 	Rescan(ctx context.Context, in *walletrpc.RescanRequest, opts ...grpc.CallOption) (walletrpc.WalletService_RescanClient, error)
 }
 
-// NodeConnection defines the functionality needed by a mining node
-// connection for the pool.
+// NodeConnection defines the functionality needed by a mining node connection
+// for the pool. Typically a dcrd client but can be stubbed for testing.
 type NodeConnection interface {
+	// GetTxOut fetches the output referenced by the provided txHash and index.
+	// WARNING: dcrd can return (nil, nil).
 	GetTxOut(context.Context, *chainhash.Hash, uint32, int8, bool) (*chainjson.GetTxOutResult, error)
 	CreateRawTransaction(context.Context, []chainjson.TransactionInput, map[stdaddr.Address]dcrutil.Amount, *int64, *int64) (*wire.MsgTx, error)
 	GetWorkSubmit(context.Context, string) (bool, error)
diff --git a/pool/paymentmgr.go b/pool/paymentmgr.go
index f95c4e95..47c67b3b 100644
--- a/pool/paymentmgr.go
+++ b/pool/paymentmgr.go
@@ -55,6 +55,7 @@ const (
 // pool. Typically a dcrd client but can be stubbed for testing.
 type txCreator interface {
 	// GetTxOut fetches the output referenced by the provided txHash and index.
+	// WARNING: dcrd can return (nil, nil).
 	GetTxOut(context.Context, *chainhash.Hash, uint32, int8, bool) (*chainjson.GetTxOutResult, error)
 	// CreateRawTransaction generates a transaction from the provided
 	// inputs and payouts.
@@ -641,8 +642,13 @@ func (pm *PaymentMgr) generatePayoutTxDetails(ctx context.Context, txC txCreator
 		// the current height.
 		txOutResult, err := txC.GetTxOut(ctx, txHash, coinbaseIndex, wire.TxTreeRegular, false)
 		if err != nil {
-			desc := fmt.Sprintf("%s: unable to find tx output: %v",
-				funcName, err)
+			desc := fmt.Sprintf("%s: unable to find tx output %s:%d: %v",
+				funcName, txHash, coinbaseIndex, err)
+			return nil, nil, nil, 0, errs.PoolError(errs.TxOut, desc)
+		}
+		if txOutResult == nil {
+			desc := fmt.Sprintf("%s: unable to find tx output %s:%d",
+				funcName, txHash, coinbaseIndex)
 			return nil, nil, nil, 0, errs.PoolError(errs.TxOut, desc)
 		}
 		if txOutResult.Confirmations < int64(pm.cfg.ActiveNet.CoinbaseMaturity+1) {
diff --git a/pool/paymentmgr_test.go b/pool/paymentmgr_test.go
index 1250105e..7155094b 100644
--- a/pool/paymentmgr_test.go
+++ b/pool/paymentmgr_test.go
@@ -840,6 +840,21 @@ func testPaymentMgrPayment(t *testing.T) {
 		t.Fatalf("expected a fetch txOut error, got %v", err)
 	}
 
+	// Ensure a (nil, nil) response from dcrd is handled gracefully.
+	// generatePayoutTxDetails should return a TxOut error rather than
+	// generating a panic.
+	txC = &txCreatorImpl{
+		getTxOut: func(ctx context.Context, txHash *chainhash.Hash, index uint32, tree int8, mempool bool) (*chainjson.GetTxOutResult, error) {
+			return nil, nil
+		},
+	}
+	_, _, _, _, err = mgr.generatePayoutTxDetails(ctx, txC, poolFeeAddrs,
+		mPmts, coinbaseIndex)
+	if !errors.Is(err, errs.TxOut) {
+		cancel()
+		t.Fatalf("expected a fetch txOut error, got %v", err)
+	}
+
 	// Ensure generating payout tx details returns an error if the returned
 	// output is not spendable.
 	txC = &txCreatorImpl{