From 032eacb796ae2cebe8d6a38733049f2a46e2e72e Mon Sep 17 00:00:00 2001
From: Olaoluwa Osuntokun <laolu32@gmail.com>
Date: Fri, 8 Mar 2019 16:04:31 -0800
Subject: [PATCH] channeldb: prevent mutating on-disk commitment state if
 channel is borked

---
 channeldb/channel.go | 48 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/channeldb/channel.go b/channeldb/channel.go
index 42a53a7c..aba7fe25 100644
--- a/channeldb/channel.go
+++ b/channeldb/channel.go
@@ -107,6 +107,10 @@ var (
 	// mutate a channel that's been recovered.
 	ErrNoRestoredChannelMutation = fmt.Errorf("cannot mutate restored " +
 		"channel state")
+
+	// ErrChanBorked is returned when a caller attempts to mutate a borked
+	// channel.
+	ErrChanBorked = fmt.Errorf("channel mutate borked channel")
 )
 
 // ChannelType is an enum-like type that describes one of several possible
@@ -807,6 +811,20 @@ func (c *OpenChannel) MarkBorked() error {
 	return c.putChanStatus(ChanStatusBorked)
 }
 
+// isBorked returns true if the channel has been marked as borked in the
+// database. This requires an existing database transaction to already be
+// active.
+//
+// NOTE: The primary mutex should already be held before this method is called.
+func (c *OpenChannel) isBorked(chanBucket *bbolt.Bucket) (bool, error) {
+	channel, err := fetchOpenChannel(chanBucket, &c.FundingOutpoint)
+	if err != nil {
+		return false, err
+	}
+
+	return channel.chanStatus != ChanStatusDefault, nil
+}
+
 // MarkCommitmentBroadcasted marks the channel as a commitment transaction has
 // been broadcast, either our own or the remote, and we should watch the chain
 // for it to confirm before taking any further action.
@@ -978,6 +996,16 @@ func (c *OpenChannel) UpdateCommitment(newCommitment *ChannelCommitment) error {
 			return err
 		}
 
+		// If the channel is marked as borked, then for safety reasons,
+		// we shouldn't attempt any further updates.
+		isBorked, err := c.isBorked(chanBucket)
+		if err != nil {
+			return err
+		}
+		if isBorked {
+			return ErrChanBorked
+		}
+
 		if err = putChanInfo(chanBucket, c); err != nil {
 			return fmt.Errorf("unable to store chan info: %v", err)
 		}
@@ -1408,6 +1436,16 @@ func (c *OpenChannel) AppendRemoteCommitChain(diff *CommitDiff) error {
 			return err
 		}
 
+		// If the channel is marked as borked, then for safety reasons,
+		// we shouldn't attempt any further updates.
+		isBorked, err := c.isBorked(chanBucket)
+		if err != nil {
+			return err
+		}
+		if isBorked {
+			return ErrChanBorked
+		}
+
 		// Any outgoing settles and fails necessarily have a
 		// corresponding adds in this channel's forwarding packages.
 		// Mark all of these as being fully processed in our forwarding
@@ -1539,6 +1577,16 @@ func (c *OpenChannel) AdvanceCommitChainTail(fwdPkg *FwdPkg) error {
 			return err
 		}
 
+		// If the channel is marked as borked, then for safety reasons,
+		// we shouldn't attempt any further updates.
+		isBorked, err := c.isBorked(chanBucket)
+		if err != nil {
+			return err
+		}
+		if isBorked {
+			return ErrChanBorked
+		}
+
 		// Persist the latest preimage state to disk as the remote peer
 		// has just added to our local preimage store, and given us a
 		// new pending revocation key.