Merge pull request #5305 from carlaKC/sessionkey-deserialize

channeldb: read HtlcAttemptInfo session key raw bytes

Author: Roasbeef

channeldb/duplicate_payments.go

@@ -53,7 +53,7 @@ type duplicateHTLCAttemptInfo struct {
 	attemptID uint64
 
 	// sessionKey is the ephemeral key used for this attempt.
-	sessionKey *btcec.PrivateKey
+	sessionKey [btcec.PrivKeyBytesLen]byte
 
 	// route is the route attempted to send the HTLC.
 	route route.Route
@@ -181,7 +181,7 @@ func fetchDuplicatePayment(bucket kvdb.RBucket) (*MPPayment, error) {
 			HTLCAttemptInfo: HTLCAttemptInfo{
 				AttemptID:  attempt.attemptID,
 				Route:      attempt.route,
-				SessionKey: attempt.sessionKey,
+				sessionKey: attempt.sessionKey,
 			},
 		}
 

channeldb/mp_payment.go

@@ -21,8 +21,15 @@ type HTLCAttemptInfo struct {
 	// AttemptID is the unique ID used for this attempt.
 	AttemptID uint64
 
-	// SessionKey is the ephemeral key used for this attempt.
-	SessionKey *btcec.PrivateKey
+	// sessionKey is the raw bytes ephemeral key used for this attempt.
+	// These bytes are lazily read off disk to save ourselves the expensive
+	// EC operations used by btcec.PrivKeyFromBytes.
+	sessionKey [btcec.PrivKeyBytesLen]byte
+
+	// cachedSessionKey is our fully deserialized sesionKey. This value
+	// may be nil if the attempt has just been read from disk and its
+	// session key has not been used yet.
+	cachedSessionKey *btcec.PrivateKey
 
 	// Route is the route attempted to send the HTLC.
 	Route route.Route
@@ -38,6 +45,36 @@ type HTLCAttemptInfo struct {
 	Hash *lntypes.Hash
 }
 
+// NewHtlcAttemptInfo creates a htlc attempt.
+func NewHtlcAttemptInfo(attemptID uint64, sessionKey *btcec.PrivateKey,
+	route route.Route, attemptTime time.Time,
+	hash *lntypes.Hash) *HTLCAttemptInfo {
+
+	var scratch [btcec.PrivKeyBytesLen]byte
+	copy(scratch[:], sessionKey.Serialize())
+
+	return &HTLCAttemptInfo{
+		AttemptID:        attemptID,
+		sessionKey:       scratch,
+		cachedSessionKey: sessionKey,
+		Route:            route,
+		AttemptTime:      attemptTime,
+		Hash:             hash,
+	}
+}
+
+// SessionKey returns the ephemeral key used for a htlc attempt. This function
+// performs expensive ec-ops to obtain the session key if it is not cached.
+func (h *HTLCAttemptInfo) SessionKey() *btcec.PrivateKey {
+	if h.cachedSessionKey == nil {
+		h.cachedSessionKey, _ = btcec.PrivKeyFromBytes(
+			btcec.S256(), h.sessionKey[:],
+		)
+	}
+
+	return h.cachedSessionKey
+}
+
 // HTLCAttempt contains information about a specific HTLC attempt for a given
 // payment. It contains the HTLCAttemptInfo used to send the HTLC, as well
 // as a timestamp and any known outcome of the attempt.

channeldb/mp_payment_test.go

@@ -0,0 +1,27 @@
+package channeldb
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// TestLazySessionKeyDeserialize tests that we can read htlc attempt session
+// keys that were previously serialized as a private key as raw bytes.
+func TestLazySessionKeyDeserialize(t *testing.T) {
+	var b bytes.Buffer
+
+	// Serialize as a private key.
+	err := WriteElements(&b, priv)
+	require.NoError(t, err)
+
+	// Deserialize into [btcec.PrivKeyBytesLen]byte.
+	attempt := HTLCAttemptInfo{}
+	err = ReadElements(&b, &attempt.sessionKey)
+	require.NoError(t, err)
+	require.Zero(t, b.Len())
+
+	sessionKey := attempt.SessionKey()
+	require.Equal(t, priv, sessionKey)
+}

channeldb/payment_control_test.go

@@ -37,17 +37,15 @@ func genInfo() (*PaymentCreationInfo, *HTLCAttemptInfo,
 	}
 
 	rhash := sha256.Sum256(preimage[:])
+	attempt := NewHtlcAttemptInfo(
+		0, priv, *testRoute.Copy(), time.Time{}, nil,
+	)
 	return &PaymentCreationInfo{
-			PaymentIdentifier: rhash,
-			Value:             testRoute.ReceiverAmt(),
-			CreationTime:      time.Unix(time.Now().Unix(), 0),
-			PaymentRequest:    []byte("hola"),
-		},
-		&HTLCAttemptInfo{
-			AttemptID:  0,
-			SessionKey: priv,
-			Route:      *testRoute.Copy(),
-		}, preimage, nil
+		PaymentIdentifier: rhash,
+		Value:             testRoute.ReceiverAmt(),
+		CreationTime:      time.Unix(time.Now().Unix(), 0),
+		PaymentRequest:    []byte("hola"),
+	}, attempt, preimage, nil
 }
 
 // TestPaymentControlSwitchFail checks that payment status returns to Failed

channeldb/payments.go

@@ -919,7 +919,7 @@ func deserializePaymentCreationInfo(r io.Reader) (*PaymentCreationInfo, error) {
 }
 
 func serializeHTLCAttemptInfo(w io.Writer, a *HTLCAttemptInfo) error {
-	if err := WriteElements(w, a.SessionKey); err != nil {
+	if err := WriteElements(w, a.sessionKey); err != nil {
 		return err
 	}
 
@@ -945,7 +945,7 @@ func serializeHTLCAttemptInfo(w io.Writer, a *HTLCAttemptInfo) error {
 
 func deserializeHTLCAttemptInfo(r io.Reader) (*HTLCAttemptInfo, error) {
 	a := &HTLCAttemptInfo{}
-	err := ReadElements(r, &a.SessionKey)
+	err := ReadElements(r, &a.sessionKey)
 	if err != nil {
 		return nil, err
 	}

channeldb/payments_test.go

@@ -68,13 +68,10 @@ func makeFakeInfo() (*PaymentCreationInfo, *HTLCAttemptInfo) {
 		PaymentRequest: []byte(""),
 	}
 
-	a := &HTLCAttemptInfo{
-		AttemptID:   44,
-		SessionKey:  priv,
-		Route:       testRoute,
-		AttemptTime: time.Unix(100, 0),
-		Hash:        &hash,
-	}
+	a := NewHtlcAttemptInfo(
+		44, priv, testRoute, time.Unix(100, 0), &hash,
+	)
+
 	return c, a
 }
 
@@ -123,9 +120,11 @@ func TestSentPaymentSerialization(t *testing.T) {
 	newWireInfo.Route = route.Route{}
 	s.Route = route.Route{}
 
+	// Call session key method to set our cached session key so we can use
+	// DeepEqual, and assert that our key equals the original key.
+	require.Equal(t, s.cachedSessionKey, newWireInfo.SessionKey())
+
 	if !reflect.DeepEqual(s, newWireInfo) {
-		s.SessionKey.Curve = nil
-		newWireInfo.SessionKey.Curve = nil
 		t.Fatalf("Payments do not match after "+
 			"serialization/deserialization %v vs %v",
 			spew.Sdump(s), spew.Sdump(newWireInfo),

routing/control_tower_test.go

@@ -331,11 +331,9 @@ func genInfo() (*channeldb.PaymentCreationInfo, *channeldb.HTLCAttemptInfo,
 			CreationTime:      time.Unix(time.Now().Unix(), 0),
 			PaymentRequest:    []byte("hola"),
 		},
-		&channeldb.HTLCAttemptInfo{
-			AttemptID:  1,
-			SessionKey: priv,
-			Route:      testRoute,
-		}, preimage, nil
+		channeldb.NewHtlcAttemptInfo(
+			1, priv, testRoute, time.Time{}, nil,
+		), preimage, nil
 }
 
 func genPreimage() ([32]byte, error) {

routing/payment_lifecycle.go

@@ -499,7 +499,7 @@ func (p *shardHandler) collectResult(attempt *channeldb.HTLCAttemptInfo) (
 
 	// Regenerate the circuit for this attempt.
 	_, circuit, err := generateSphinxPacket(
-		&attempt.Route, hash[:], attempt.SessionKey,
+		&attempt.Route, hash[:], attempt.SessionKey(),
 	)
 	if err != nil {
 		return nil, err
@@ -677,15 +677,11 @@ func (p *shardHandler) createNewPaymentAttempt(rt *route.Route, lastShard bool)
 		rt.Hops[0].ChannelID,
 	)
 
-	// We now have all the information needed to populate
-	// the current attempt information.
-	attempt := &channeldb.HTLCAttemptInfo{
-		AttemptID:   attemptID,
-		AttemptTime: p.router.cfg.Clock.Now(),
-		SessionKey:  sessionKey,
-		Route:       *rt,
-		Hash:        &hash,
-	}
+	// We now have all the information needed to populate the current
+	// attempt information.
+	attempt := channeldb.NewHtlcAttemptInfo(
+		attemptID, sessionKey, *rt, p.router.cfg.Clock.Now(), &hash,
+	)
 
 	return firstHop, htlcAdd, attempt, nil
 }