From da049ebcf7831c23145ce277ad988e08857e5315 Mon Sep 17 00:00:00 2001
From: Conner Fromknecht <conner@lightning.engineering>
Date: Wed, 3 Mar 2021 09:56:28 -0800
Subject: [PATCH] channeldb: ensure invoices can't be added with HTLCs

---
 channeldb/invoice_test.go | 18 ++++++++++++++++++
 channeldb/invoices.go     |  9 +++++++++
 2 files changed, 27 insertions(+)

diff --git a/channeldb/invoice_test.go b/channeldb/invoice_test.go
index 4e01f52e..a66d9f25 100644
--- a/channeldb/invoice_test.go
+++ b/channeldb/invoice_test.go
@@ -1304,6 +1304,24 @@ func TestHTLCSet(t *testing.T) {
 	}
 }
 
+// TestAddInvoiceWithHTLCs asserts that you can't insert an invoice that already
+// has HTLCs.
+func TestAddInvoiceWithHTLCs(t *testing.T) {
+	db, cleanUp, err := MakeTestDB()
+	defer cleanUp()
+	require.Nil(t, err)
+
+	testInvoice, err := randInvoice(1000)
+	require.Nil(t, err)
+
+	key := CircuitKey{HtlcID: 1}
+	testInvoice.Htlcs[key] = &InvoiceHTLC{}
+
+	payHash := testInvoice.Terms.PaymentPreimage.Hash()
+	_, err = db.AddInvoice(testInvoice, payHash)
+	require.Equal(t, ErrInvoiceHasHtlcs, err)
+}
+
 // TestDeleteInvoices tests that deleting a list of invoices will succeed
 // if all delete references are valid, or will fail otherwise.
 func TestDeleteInvoices(t *testing.T) {
diff --git a/channeldb/invoices.go b/channeldb/invoices.go
index bcff0629..9f867ea8 100644
--- a/channeldb/invoices.go
+++ b/channeldb/invoices.go
@@ -106,6 +106,10 @@ var (
 	// ErrInvoicePreimageMismatch is returned when the preimage doesn't
 	// match the invoice hash.
 	ErrInvoicePreimageMismatch = errors.New("preimage does not match")
+
+	// ErrInvoiceHasHtlcs is returned when attempting to insert an invoice
+	// that already has HTLCs.
+	ErrInvoiceHasHtlcs = errors.New("cannot add invoice with htlcs")
 )
 
 const (
@@ -588,6 +592,11 @@ func validateInvoice(i *Invoice, paymentHash lntypes.Hash) error {
 	if i.Terms.PaymentPreimage == nil && !i.HodlInvoice {
 		return errors.New("non-hodl invoices must have a preimage")
 	}
+
+	if len(i.Htlcs) > 0 {
+		return ErrInvoiceHasHtlcs
+	}
+
 	return nil
 }