From db66fef6cc0ea4efccc46544004557fb2d17400e Mon Sep 17 00:00:00 2001
From: "Johan T. Halseth" <johanth@gmail.com>
Date: Fri, 19 Feb 2021 12:03:01 +0100
Subject: [PATCH] channeldb+htlcswitch: write wire messages using length prefix

In this commit, we modify the way we write wire messages across the
entire database. We'll now ensure that we always write wire messages
with a length prefix. We update the `codec.go` file to always write a 2
byte length prefix, this affects the way we write the `CommitDiff` and
`LogUpdates` struct to disk, and the network results bucket in the
switch as it includes a wire message.
---
 channeldb/channel.go         | 14 ++++++++++----
 channeldb/codec.go           | 21 +++++++++++++++++++--
 htlcswitch/payment_result.go | 17 ++---------------
 3 files changed, 31 insertions(+), 21 deletions(-)

diff --git a/channeldb/channel.go b/channeldb/channel.go
index 3bd014aeb..d36ded213 100644
--- a/channeldb/channel.go
+++ b/channeldb/channel.go
@@ -1965,12 +1965,12 @@ func deserializeLogUpdates(r io.Reader) ([]LogUpdate, error) {
 	return logUpdates, nil
 }
 
-func serializeCommitDiff(w io.Writer, diff *CommitDiff) error {
+func serializeCommitDiff(w io.Writer, diff *CommitDiff) error { // nolint: dupl
 	if err := serializeChanCommit(w, &diff.Commitment); err != nil {
 		return err
 	}
 
-	if err := diff.CommitSig.Encode(w, 0); err != nil {
+	if err := WriteElements(w, diff.CommitSig); err != nil {
 		return err
 	}
 
@@ -2016,10 +2016,16 @@ func deserializeCommitDiff(r io.Reader) (*CommitDiff, error) {
 		return nil, err
 	}
 
-	d.CommitSig = &lnwire.CommitSig{}
-	if err := d.CommitSig.Decode(r, 0); err != nil {
+	var msg lnwire.Message
+	if err := ReadElements(r, &msg); err != nil {
 		return nil, err
 	}
+	commitSig, ok := msg.(*lnwire.CommitSig)
+	if !ok {
+		return nil, fmt.Errorf("expected lnwire.CommitSig, instead "+
+			"read: %T", msg)
+	}
+	d.CommitSig = commitSig
 
 	d.LogUpdates, err = deserializeLogUpdates(r)
 	if err != nil {
diff --git a/channeldb/codec.go b/channeldb/codec.go
index f6903175f..424f7c6e8 100644
--- a/channeldb/codec.go
+++ b/channeldb/codec.go
@@ -1,6 +1,7 @@
 package channeldb
 
 import (
+	"bytes"
 	"encoding/binary"
 	"fmt"
 	"io"
@@ -178,7 +179,17 @@ func WriteElement(w io.Writer, element interface{}) error {
 		}
 
 	case lnwire.Message:
-		if _, err := lnwire.WriteMessage(w, e, 0); err != nil {
+		var msgBuf bytes.Buffer
+		if _, err := lnwire.WriteMessage(&msgBuf, e, 0); err != nil {
+			return err
+		}
+
+		msgLen := uint16(len(msgBuf.Bytes()))
+		if err := WriteElements(w, msgLen); err != nil {
+			return err
+		}
+
+		if _, err := w.Write(msgBuf.Bytes()); err != nil {
 			return err
 		}
 
@@ -394,7 +405,13 @@ func ReadElement(r io.Reader, element interface{}) error {
 		*e = bytes
 
 	case *lnwire.Message:
-		msg, err := lnwire.ReadMessage(r, 0)
+		var msgLen uint16
+		if err := ReadElement(r, &msgLen); err != nil {
+			return err
+		}
+
+		msgReader := io.LimitReader(r, int64(msgLen))
+		msg, err := lnwire.ReadMessage(msgReader, 0)
 		if err != nil {
 			return err
 		}
diff --git a/htlcswitch/payment_result.go b/htlcswitch/payment_result.go
index cd5fe0a56..06345affb 100644
--- a/htlcswitch/payment_result.go
+++ b/htlcswitch/payment_result.go
@@ -61,28 +61,15 @@ type networkResult struct {
 
 // serializeNetworkResult serializes the networkResult.
 func serializeNetworkResult(w io.Writer, n *networkResult) error {
-	if _, err := lnwire.WriteMessage(w, n.msg, 0); err != nil {
-		return err
-	}
-
-	return channeldb.WriteElements(w, n.unencrypted, n.isResolution)
+	return channeldb.WriteElements(w, n.msg, n.unencrypted, n.isResolution)
 }
 
 // deserializeNetworkResult deserializes the networkResult.
 func deserializeNetworkResult(r io.Reader) (*networkResult, error) {
-	var (
-		err error
-	)
-
 	n := &networkResult{}
 
-	n.msg, err = lnwire.ReadMessage(r, 0)
-	if err != nil {
-		return nil, err
-	}
-
 	if err := channeldb.ReadElements(r,
-		&n.unencrypted, &n.isResolution,
+		&n.msg, &n.unencrypted, &n.isResolution,
 	); err != nil {
 		return nil, err
 	}