Remove legacy backup code (#811)

This is a follow-up to #807.

Note that we cannot remove some legacy classes such as `EncryptedChannelData`, due to the legacy v2/v3 serialization depending on it.

Author: pm47

modules/core/src/commonMain/kotlin/fr/acinq/lightning/io/Peer.kt

@@ -23,7 +23,6 @@ import fr.acinq.lightning.payment.*
 import fr.acinq.lightning.serialization.channel.Encryption.from
 import fr.acinq.lightning.serialization.channel.Encryption.fromEncryptedPeerStorage
 import fr.acinq.lightning.serialization.channel.Serialization.PeerStorageDeserializationResult
-import fr.acinq.lightning.serialization.channel.Serialization.DeserializationResult
 import fr.acinq.lightning.transactions.Scripts
 import fr.acinq.lightning.transactions.Transactions
 import fr.acinq.lightning.utils.*
@@ -1249,40 +1248,6 @@ class Peer(
                             logger.warning { "received unwanted peer storage" }
                         }
                     }
-                    is ChannelReestablish -> {
-                        val backup: DeserializationResult? = msg.legacyChannelData.takeIf { !it.isEmpty() }?.let { channelData ->
-                            PersistedChannelState
-                                .from(nodeParams.nodePrivateKey, channelData)
-                                .onFailure { logger.warning(it) { "unreadable backup" } }
-                                .getOrNull()
-                        }
-                        val state: ChannelState? = when {
-                            backup == null -> _channels[msg.channelId]
-                            backup is DeserializationResult.UnknownVersion -> {
-                                logger.warning { "peer sent a reestablish with a backup generated by a more recent version of phoenix: version=${backup.version}." }
-                                // In this corner case, we do not want to return an error to the peer, because they will force-close and we will be unable to
-                                // do anything as we can't read the data. Best thing is to not answer, and tell the user to upgrade the app.
-                                logger.error { "need to upgrade your app!" }
-                                nodeParams._nodeEvents.emit(UpgradeRequired)
-                                null
-                            }
-                            backup is DeserializationResult.Success && backup.state.channelId == msg.channelId -> {
-                                maybeRestoreBackup(backup.state)
-                            }
-                            else -> {
-                                logger.warning { "peer sent a reestablish with a backup for a different channel" }
-                                _channels[msg.channelId]
-                            }
-                        }
-                        if (state == null) {
-                            logger.warning { "peer sent a reestablish for an unknown channel with no or undecipherable backup" }
-                            peerConnection?.send(Error(msg.channelId, "unknown channel"))
-                        } else {
-                            val (state1, actions1) = state.process(ChannelCommand.MessageReceived(msg))
-                            processActions(msg.channelId, peerConnection, actions1, state1)
-                            _channels = _channels + (msg.channelId to state1)
-                        }
-                    }
                     is HasTemporaryChannelId -> {
                         _channels[msg.temporaryChannelId]?.let { state ->
                             logger.info { "received ${msg::class.simpleName} for temporary channel ${msg.temporaryChannelId}" }

modules/core/src/commonMain/kotlin/fr/acinq/lightning/serialization/channel/Encryption.kt

@@ -10,7 +10,6 @@ import fr.acinq.lightning.logging.MDCLogger
 import fr.acinq.lightning.serialization.InputExtensions.readCollection
 import fr.acinq.lightning.serialization.InputExtensions.readDelimitedByteArray
 import fr.acinq.lightning.utils.toByteVector
-import fr.acinq.lightning.wire.EncryptedChannelData
 import fr.acinq.lightning.wire.EncryptedPeerStorage
 
 /**
@@ -34,27 +33,6 @@ object Encryption {
         return ChaCha20Poly1305.decrypt(key.toByteArray(), nonce.toByteArray(), ciphertext.toByteArray(), ByteArray(0), tag.toByteArray())
     }
 
-    /**
-     * Convenience method that builds an [EncryptedChannelData] from a [PersistedChannelState]
-     */
-    fun EncryptedChannelData.Companion.from(key: PrivateKey, state: PersistedChannelState): EncryptedChannelData {
-        val bin = Serialization.serialize(state)
-        val encrypted = encrypt(key.value, bin)
-        // we copy the first 2 bytes as meta-info on the serialization version
-        val data = bin.copyOfRange(0, 2) + encrypted
-        return EncryptedChannelData(data.toByteVector())
-    }
-
-    /**
-     * Convenience method that decrypts and deserializes a [PersistedChannelState] from an [EncryptedChannelData]
-     */
-    fun PersistedChannelState.Companion.from(key: PrivateKey, encryptedChannelData: EncryptedChannelData): Result<Serialization.DeserializationResult> {
-        // we first assume that channel data is prefixed by 2 bytes of serialization meta-info
-        return runCatching { decrypt(key.value, encryptedChannelData.data.drop(2).toByteArray()) }
-            .recoverCatching { decrypt(key.value, encryptedChannelData.data.toByteArray()) }
-            .map { Serialization.deserialize(it) }
-    }
-
     /**
      * Convenience method that builds an [EncryptedPeerStorage] from a list of [PersistedChannelState]
      */

modules/core/src/commonMain/kotlin/fr/acinq/lightning/wire/ChannelTlv.kt

@@ -170,7 +170,7 @@ sealed class ChannelReestablishTlv : Tlv {
         }
     }
 
-    // Legacy TLV needed to deserialize old backups
+    /** Legacy TLV needed to deserialize old backups */
     data class ChannelData(val ecb: EncryptedChannelData) : ChannelReestablishTlv() {
         override val tag: Long get() = ChannelData.tag
         override fun write(out: Output) = LightningCodecs.writeBytes(ecb.data, out)
@@ -183,7 +183,7 @@ sealed class ChannelReestablishTlv : Tlv {
 }
 
 sealed class ShutdownTlv : Tlv {
-    // Legacy TLV needed to deserialize old backups
+    /** Legacy TLV needed to deserialize old backups */
     data class ChannelData(val ecb: EncryptedChannelData) : ShutdownTlv() {
         override val tag: Long get() = ChannelData.tag
         override fun write(out: Output) = LightningCodecs.writeBytes(ecb.data, out)

modules/core/src/commonMain/kotlin/fr/acinq/lightning/wire/LightningMessages.kt

@@ -156,18 +156,8 @@ interface HasChainHash : LightningMessage {
 
 interface ForbiddenMessageDuringSplice : LightningMessage
 
-/**
- * Legacy format to backup channel state.
- * It is only kept to restore old channels. New backups now use EncryptedPeerStorage.
- */
+/** Legacy format for channel backup, needed to deserialize old backups */
 data class EncryptedChannelData(val data: ByteVector) {
-    /** We don't want to log the encrypted channel backups, they take a lot of space. We only keep the first bytes to help correlate mobile/server backups. */
-    override fun toString(): String {
-        val bytes = data.take(min(data.size(), 10))
-        return if (bytes.isEmpty()) "" else "$bytes (truncated)"
-    }
-
-    fun isEmpty(): Boolean = data.isEmpty()
 
     companion object {
         val empty: EncryptedChannelData = EncryptedChannelData(ByteVector.empty)
@@ -1329,8 +1319,6 @@ data class ChannelReestablish(
     override val type: Long get() = ChannelReestablish.type
 
     val nextFundingTxId: TxId? = tlvStream.get<ChannelReestablishTlv.NextFunding>()?.txId
-    // Legacy channel backup present only on old inactive channels, will be replaced by peer storage next time this channel data is updated.
-    val legacyChannelData: EncryptedChannelData get() = tlvStream.get<ChannelReestablishTlv.ChannelData>()?.ecb ?: EncryptedChannelData.empty
 
     override fun write(out: Output) {
         LightningCodecs.writeBytes(channelId, out)