From 9177358a3ce8298c0eab567669ac44c7c184738e Mon Sep 17 00:00:00 2001
From: Conner Fromknecht <conner@lightning.engineering>
Date: Fri, 15 Mar 2019 02:30:22 -0700
Subject: [PATCH] watchtower/wtdb/client_session: add ClientSession

---
 watchtower/wtdb/client_session.go | 110 ++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 watchtower/wtdb/client_session.go

diff --git a/watchtower/wtdb/client_session.go b/watchtower/wtdb/client_session.go
new file mode 100644
index 00000000..f7b531fe
--- /dev/null
+++ b/watchtower/wtdb/client_session.go
@@ -0,0 +1,110 @@
+package wtdb
+
+import (
+	"errors"
+
+	"github.com/btcsuite/btcd/btcec"
+	"github.com/lightningnetwork/lnd/keychain"
+	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/lightningnetwork/lnd/watchtower/wtpolicy"
+)
+
+var (
+	// ErrClientSessionNotFound signals that the requested client session
+	// was not found in the database.
+	ErrClientSessionNotFound = errors.New("client session not found")
+
+	// ErrUpdateAlreadyCommitted signals that the chosen sequence number has
+	// already been committed to an update with a different breach hint.
+	ErrUpdateAlreadyCommitted = errors.New("update already committed")
+
+	// ErrCommitUnorderedUpdate signals the client tried to commit a
+	// sequence number other than the next unallocated sequence number.
+	ErrCommitUnorderedUpdate = errors.New("update seqnum not monotonic")
+
+	// ErrCommittedUpdateNotFound signals that the tower tried to ACK a
+	// sequence number that has not yet been allocated by the client.
+	ErrCommittedUpdateNotFound = errors.New("committed update not found")
+
+	// ErrUnallocatedLastApplied signals that the tower tried to provide a
+	// LastApplied value greater than any allocated sequence number.
+	ErrUnallocatedLastApplied = errors.New("tower echoed last appiled " +
+		"greater than allocated seqnum")
+)
+
+// ClientSession encapsulates a SessionInfo returned from a successful
+// session negotiation, and also records the tower and ephemeral secret used for
+// communicating with the tower.
+type ClientSession struct {
+	// ID is the client's public key used when authenticating with the
+	// tower.
+	ID SessionID
+
+	// SeqNum is the next unallocated sequence number that can be sent to
+	// the tower.
+	SeqNum uint16
+
+	// TowerLastApplied the last last-applied the tower has echoed back.
+	TowerLastApplied uint16
+
+	// TowerID is the unique, db-assigned identifier that references the
+	// Tower with which the session is negotiated.
+	TowerID uint64
+
+	// Tower holds the pubkey and address of the watchtower.
+	//
+	// NOTE: This value is not serialized. It is recovered by looking up the
+	// tower with TowerID.
+	Tower *Tower
+
+	// SessionKeyDesc is the key descriptor used to derive the client's
+	// session key so that it can authenticate with the tower to update its
+	// session.
+	SessionKeyDesc keychain.KeyLocator
+
+	// SessionPrivKey is the ephemeral secret key used to connect to the
+	// watchtower.
+	// TODO(conner): remove after HD keys
+	SessionPrivKey *btcec.PrivateKey
+
+	// Policy holds the negotiated session parameters.
+	Policy wtpolicy.Policy
+
+	// RewardPkScript is the pkscript that the tower's reward will be
+	// deposited to if a sweep transaction confirms and the sessions
+	// specifies a reward output.
+	RewardPkScript []byte
+
+	// CommittedUpdates is a map from allocated sequence numbers to unacked
+	// updates. These updates can be resent after a restart if the update
+	// failed to send or receive an acknowledgment.
+	CommittedUpdates map[uint16]*CommittedUpdate
+
+	// AckedUpdates is a map from sequence number to backup id to record
+	// which revoked states were uploaded via this session.
+	AckedUpdates map[uint16]BackupID
+}
+
+// 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 lnwire.ChannelID
+
+	// CommitHeight is the commitment height of the revoked commitment.
+	CommitHeight uint64
+}
+
+// CommittedUpdate holds a state update sent by a client along with its
+// SessionID.
+type CommittedUpdate struct {
+	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 braodcast.
+	EncryptedBlob []byte
+}