lnwire: limit channel update reader

Fixes a bug where channel update data is read until the end of the stream
rather than stopping after the specified length. This is problematic
when failure message tlv data is present, because this data is interpreted
as channel update tlv data.

lnwire/onion_error_test.go

@@ -1,9 +1,9 @@
 package lnwire
 
 import (
-	"bufio"
 	"bytes"
 	"encoding/binary"
+	"encoding/hex"
 	"io"
 	"reflect"
 	"testing"
@@ -82,6 +82,44 @@ func TestEncodeDecodeCode(t *testing.T) {
 	}
 }
 
+// TestEncodeDecodeTlv tests the ability of onion errors to be properly encoded
+// and decoded with tlv data present.
+func TestEncodeDecodeTlv(t *testing.T) {
+	t.Parallel()
+
+	for _, testFailure := range onionFailures {
+		testFailure := testFailure
+		code := testFailure.Code().String()
+
+		t.Run(code, func(t *testing.T) {
+			t.Parallel()
+
+			testEncodeDecodeTlv(t, testFailure)
+		})
+	}
+}
+
+var testTlv, _ = hex.DecodeString("fd023104deadbeef")
+
+func testEncodeDecodeTlv(t *testing.T, testFailure FailureMessage) { //nolint: lll,thelper
+	var failureMessageBuffer bytes.Buffer
+
+	err := EncodeFailureMessage(&failureMessageBuffer, testFailure, 0)
+	require.NoError(t, err)
+
+	failureMessageBuffer.Write(testTlv)
+
+	failure, err := DecodeFailureMessage(&failureMessageBuffer, 0)
+	require.NoError(t, err)
+
+	// FailIncorrectDetails already reads tlv data. Adapt the expected data.
+	if incorrectDetails, ok := testFailure.(*FailIncorrectDetails); ok {
+		incorrectDetails.extraOpaqueData = testTlv
+	}
+
+	require.Equal(t, testFailure, failure)
+}
+
 // TestChannelUpdateCompatabilityParsing tests that we're able to properly read
 // out channel update messages encoded in an onion error payload that was
 // written in the legacy (type prefixed) format.
@@ -100,7 +138,7 @@ func TestChannelUpdateCompatabilityParsing(t *testing.T) {
 	// encoded channel update message.
 	var newChanUpdate ChannelUpdate
 	err := parseChannelUpdateCompatabilityMode(
-		bufio.NewReader(&b), &newChanUpdate, 0,
+		&b, uint16(b.Len()), &newChanUpdate, 0,
 	)
 	require.NoError(t, err, "unable to parse channel update")
 
@@ -127,7 +165,7 @@ func TestChannelUpdateCompatabilityParsing(t *testing.T) {
 	// message even with the extra two bytes.
 	var newChanUpdate2 ChannelUpdate
 	err = parseChannelUpdateCompatabilityMode(
-		bufio.NewReader(&b), &newChanUpdate2, 0,
+		&b, uint16(b.Len()), &newChanUpdate2, 0,
 	)
 	require.NoError(t, err, "unable to parse channel update")