From 3a0d49401ff856d3ac6b44c8a07a3807231d754c Mon Sep 17 00:00:00 2001
From: Virgil <virgil@lethean.io>
Date: Sat, 4 Apr 2026 15:55:09 +0000
Subject: [PATCH] fix(consensus): reject unknown tx variants

Tighten semantic validation so unknown transaction inputs, outputs, and bare output targets are rejected explicitly instead of falling through the default case.\n\nCo-Authored-By: Charon <charon@lethean.io>
---
 consensus/tx.go      | 10 ++++++++--
 consensus/tx_test.go | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/consensus/tx.go b/consensus/tx.go
index a24bbc7..90d178d 100644
--- a/consensus/tx.go
+++ b/consensus/tx.go
@@ -119,11 +119,12 @@ func checkInputTypes(tx *types.Transaction, hf1Active, hf4Active bool) error {
 			if !hf1Active {
 				return coreerr.E("checkInputTypes", fmt.Sprintf("tag %d pre-HF1", vin.InputType()), ErrInvalidInputType)
 			}
-		default:
-			// Future types (ZC) — accept if HF4+.
+		case types.TxInputZC:
 			if !hf4Active {
 				return coreerr.E("checkInputTypes", fmt.Sprintf("tag %d pre-HF4", vin.InputType()), ErrInvalidInputType)
 			}
+		default:
+			return coreerr.E("checkInputTypes", fmt.Sprintf("unsupported input type %T", vin), ErrInvalidInputType)
 		}
 	}
 	return nil
@@ -150,13 +151,18 @@ func checkOutputs(tx *types.Transaction, hf1Active, hf4Active bool) error {
 			}
 			// HTLC and Multisig output targets require at least HF1.
 			switch o.Target.(type) {
+			case types.TxOutToKey:
 			case types.TxOutHTLC, types.TxOutMultisig:
 				if !hf1Active {
 					return coreerr.E("checkOutputs", fmt.Sprintf("output %d: HTLC/multisig target pre-HF1", i), ErrInvalidOutput)
 				}
+			default:
+				return coreerr.E("checkOutputs", fmt.Sprintf("output %d: unsupported target type %T", i, o.Target), ErrInvalidOutput)
 			}
 		case types.TxOutputZarcanum:
 			// Validated by proof verification.
+		default:
+			return coreerr.E("checkOutputs", fmt.Sprintf("unsupported output type %T", vout), ErrInvalidOutput)
 		}
 	}
 
diff --git a/consensus/tx_test.go b/consensus/tx_test.go
index 2ea2e40..96db144 100644
--- a/consensus/tx_test.go
+++ b/consensus/tx_test.go
@@ -16,6 +16,18 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+type unknownTxInput struct{}
+
+func (unknownTxInput) InputType() uint8 { return 99 }
+
+type unknownTxOutput struct{}
+
+func (unknownTxOutput) OutputType() uint8 { return 99 }
+
+type unknownTxOutputTarget struct{}
+
+func (unknownTxOutputTarget) TargetType() uint8 { return 99 }
+
 // validV1Tx returns a minimal valid v1 transaction for testing.
 func validV1Tx() *types.Transaction {
 	return &types.Transaction{
@@ -73,6 +85,14 @@ func TestValidateTransaction_InvalidInputType(t *testing.T) {
 	assert.ErrorIs(t, err, ErrInvalidInputType)
 }
 
+func TestValidateTransaction_UnknownInputType(t *testing.T) {
+	tx := validV1Tx()
+	tx.Vin = []types.TxInput{unknownTxInput{}}
+	blob := make([]byte, 100)
+	err := ValidateTransaction(tx, blob, config.MainnetForks, 5000)
+	assert.ErrorIs(t, err, ErrInvalidInputType)
+}
+
 func TestValidateTransaction_NoOutputs(t *testing.T) {
 	tx := validV1Tx()
 	tx.Vout = nil
@@ -102,6 +122,24 @@ func TestValidateTransaction_ZeroOutputAmount(t *testing.T) {
 	assert.ErrorIs(t, err, ErrInvalidOutput)
 }
 
+func TestValidateTransaction_UnsupportedOutputType(t *testing.T) {
+	tx := validV1Tx()
+	tx.Vout = []types.TxOutput{unknownTxOutput{}}
+	blob := make([]byte, 100)
+	err := ValidateTransaction(tx, blob, config.MainnetForks, 5000)
+	assert.ErrorIs(t, err, ErrInvalidOutput)
+}
+
+func TestValidateTransaction_UnsupportedBareTargetType(t *testing.T) {
+	tx := validV1Tx()
+	tx.Vout = []types.TxOutput{
+		types.TxOutputBare{Amount: 90, Target: unknownTxOutputTarget{}},
+	}
+	blob := make([]byte, 100)
+	err := ValidateTransaction(tx, blob, config.MainnetForks, 5000)
+	assert.ErrorIs(t, err, ErrInvalidOutput)
+}
+
 func TestValidateTransaction_DuplicateKeyImage(t *testing.T) {
 	ki := types.KeyImage{42}
 	tx := &types.Transaction{
@@ -238,6 +276,8 @@ func TestCheckOutputs_MultisigTargetPostHF1_Good(t *testing.T) {
 	require.NoError(t, err)
 }
 
+type unknownTxOutputTarget struct{}
+
 // --- Key image tests for HTLC (Task 8) ---
 
 func TestCheckKeyImages_HTLCDuplicate_Bad(t *testing.T) {