wtdb/migration8: migrate channel max heights

watchtower/wtdb/migration8/codec.go

@@ -0,0 +1,234 @@
+package migration8
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/hex"
+	"fmt"
+	"io"
+
+	"github.com/btcsuite/btcd/wire"
+	"github.com/lightningnetwork/lnd/tlv"
+)
+
+// BreachHintSize is the length of the identifier used to detect remote
+// commitment broadcasts.
+const BreachHintSize = 16
+
+// BreachHint is the first 16-bytes of SHA256(txid), which is used to identify
+// the breach transaction.
+type BreachHint [BreachHintSize]byte
+
+// ChannelID is a series of 32-bytes that uniquely identifies all channels
+// within the network. The ChannelID is computed using the outpoint of the
+// funding transaction (the txid, and output index). Given a funding output the
+// ChannelID can be calculated by XOR'ing the big-endian serialization of the
+// txid and the big-endian serialization of the output index, truncated to
+// 2 bytes.
+type ChannelID [32]byte
+
+// writeBigSize will encode the given uint64 as a BigSize byte slice.
+func writeBigSize(i uint64) ([]byte, error) {
+	var b bytes.Buffer
+	err := tlv.WriteVarInt(&b, i, &[8]byte{})
+	if err != nil {
+		return nil, err
+	}
+
+	return b.Bytes(), nil
+}
+
+// readBigSize converts the given byte slice into a uint64 and assumes that the
+// bytes slice is using BigSize encoding.
+func readBigSize(b []byte) (uint64, error) {
+	r := bytes.NewReader(b)
+	i, err := tlv.ReadVarInt(r, &[8]byte{})
+	if err != nil {
+		return 0, err
+	}
+
+	return i, nil
+}
+
+// CommittedUpdate holds a state update sent by a client along with its
+// allocated sequence number and the exact remote commitment the encrypted
+// justice transaction can rectify.
+type CommittedUpdate struct {
+	// SeqNum is the unique sequence number allocated by the session to this
+	// update.
+	SeqNum uint16
+
+	CommittedUpdateBody
+}
+
+// BackupID identifies a particular revoked, remote commitment by channel id and
+// commitment height.
+type BackupID struct {
+	// ChanID is the channel id of the revoked commitment.
+	ChanID ChannelID
+
+	// CommitHeight is the commitment height of the revoked commitment.
+	CommitHeight uint64
+}
+
+// Encode writes the BackupID from the passed io.Writer.
+func (b *BackupID) Encode(w io.Writer) error {
+	return WriteElements(w,
+		b.ChanID,
+		b.CommitHeight,
+	)
+}
+
+// Decode reads a BackupID from the passed io.Reader.
+func (b *BackupID) Decode(r io.Reader) error {
+	return ReadElements(r,
+		&b.ChanID,
+		&b.CommitHeight,
+	)
+}
+
+// String returns a human-readable encoding of a BackupID.
+func (b BackupID) String() string {
+	return fmt.Sprintf("backup(%v, %d)", b.ChanID, b.CommitHeight)
+}
+
+// WriteElements serializes a variadic list of elements into the given
+// io.Writer.
+func WriteElements(w io.Writer, elements ...interface{}) error {
+	for _, element := range elements {
+		if err := WriteElement(w, element); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// ReadElements deserializes the provided io.Reader into a variadic list of
+// target elements.
+func ReadElements(r io.Reader, elements ...interface{}) error {
+	for _, element := range elements {
+		if err := ReadElement(r, element); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// WriteElement serializes a single element into the provided io.Writer.
+func WriteElement(w io.Writer, element interface{}) error {
+	switch e := element.(type) {
+	case ChannelID:
+		if _, err := w.Write(e[:]); err != nil {
+			return err
+		}
+
+	case uint64:
+		if err := binary.Write(w, byteOrder, e); err != nil {
+			return err
+		}
+
+	case BreachHint:
+		if _, err := w.Write(e[:]); err != nil {
+			return err
+		}
+
+	case []byte:
+		if err := wire.WriteVarBytes(w, 0, e); err != nil {
+			return err
+		}
+
+	default:
+		return fmt.Errorf("unexpected type")
+	}
+
+	return nil
+}
+
+// ReadElement deserializes a single element from the provided io.Reader.
+func ReadElement(r io.Reader, element interface{}) error {
+	switch e := element.(type) {
+	case *ChannelID:
+		if _, err := io.ReadFull(r, e[:]); err != nil {
+			return err
+		}
+
+	case *uint64:
+		if err := binary.Read(r, byteOrder, e); err != nil {
+			return err
+		}
+
+	case *BreachHint:
+		if _, err := io.ReadFull(r, e[:]); err != nil {
+			return err
+		}
+
+	case *[]byte:
+		bytes, err := wire.ReadVarBytes(r, 0, 66000, "[]byte")
+		if err != nil {
+			return err
+		}
+
+		*e = bytes
+
+	default:
+		return fmt.Errorf("unexpected type")
+	}
+
+	return nil
+}
+
+// CommittedUpdateBody represents the primary components of a CommittedUpdate.
+// On disk, this is stored under the sequence number, which acts as its key.
+type CommittedUpdateBody struct {
+	// BackupID identifies the breached commitment that the encrypted blob
+	// can spend from.
+	BackupID BackupID
+
+	// Hint is the 16-byte prefix of the revoked commitment transaction ID.
+	Hint BreachHint
+
+	// EncryptedBlob is a ciphertext containing the sweep information for
+	// exacting justice if the commitment transaction matching the breach
+	// hint is broadcast.
+	EncryptedBlob []byte
+}
+
+// Encode writes the CommittedUpdateBody to the passed io.Writer.
+func (u *CommittedUpdateBody) Encode(w io.Writer) error {
+	err := u.BackupID.Encode(w)
+	if err != nil {
+		return err
+	}
+
+	return WriteElements(w,
+		u.Hint,
+		u.EncryptedBlob,
+	)
+}
+
+// Decode reads a CommittedUpdateBody from the passed io.Reader.
+func (u *CommittedUpdateBody) Decode(r io.Reader) error {
+	err := u.BackupID.Decode(r)
+	if err != nil {
+		return err
+	}
+
+	return ReadElements(r,
+		&u.Hint,
+		&u.EncryptedBlob,
+	)
+}
+
+// SessionIDSize is 33-bytes; it is a serialized, compressed public key.
+const SessionIDSize = 33
+
+// SessionID is created from the remote public key of a client, and serves as a
+// unique identifier and authentication for sending state updates.
+type SessionID [SessionIDSize]byte
+
+// String returns a hex encoding of the session id.
+func (s SessionID) String() string {
+	return hex.EncodeToString(s[:])
+}