fix: EOTS signing for multiple finality providers (#199)

To support EOTS signing for multiple finality providers, the signing
record should be saved with key (public key || chainID || height)

CHANGELOG.md

@@ -37,6 +37,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ## Unreleased
 
+### Bug Fixes
+
+* [#199](https://github.com/babylonlabs-io/finality-provider/pull/199) EOTS signing for multiple finality providers
+
 ## v0.13.0
 
 ### Improvements

eotsmanager/localmanager.go

@@ -4,10 +4,11 @@ import (
 	"bytes"
 	"encoding/hex"
 	"fmt"
-	"github.com/babylonlabs-io/finality-provider/metrics"
 	"strings"
 	"sync"
 
+	"github.com/babylonlabs-io/finality-provider/metrics"
+
 	"github.com/babylonlabs-io/babylon/crypto/eots"
 	bbntypes "github.com/babylonlabs-io/babylon/types"
 	"github.com/btcsuite/btcd/btcec/v2"
@@ -193,50 +194,60 @@ func (lm *LocalEOTSManager) CreateRandomnessPairList(fpPk []byte, chainID []byte
 	return prList, nil
 }
 
-func (lm *LocalEOTSManager) SignEOTS(fpPk []byte, chainID []byte, msg []byte, height uint64, passphrase string) (*btcec.ModNScalar, error) {
-	record, found, err := lm.es.GetSignRecord(height)
+func (lm *LocalEOTSManager) SignEOTS(eotsPk []byte, chainID []byte, msg []byte, height uint64, passphrase string) (*btcec.ModNScalar, error) {
+	record, found, err := lm.es.GetSignRecord(eotsPk, chainID, height)
 	if err != nil {
 		return nil, fmt.Errorf("error getting sign record: %w", err)
-	} else if found {
-		if bytes.Equal(msg, record.BlockHash) {
+	}
+
+	if found {
+		if bytes.Equal(msg, record.Msg) {
 			var s btcec.ModNScalar
 			s.SetByteSlice(record.Signature)
 
+			lm.logger.Warn(
+				"duplicate sign requested",
+				zap.String("eots_pk", hex.EncodeToString(eotsPk)),
+				zap.String("hash", hex.EncodeToString(msg)),
+				zap.Uint64("height", height),
+				zap.String("chainID", string(chainID)),
+			)
+
 			return &s, nil
 		}
 
 		lm.logger.Error(
-			"double sign error protection",
-			zap.String("fp", hex.EncodeToString(fpPk)),
-			zap.String("msg", hex.EncodeToString(msg)),
+			"double sign requested",
+			zap.String("eots_pk", hex.EncodeToString(eotsPk)),
+			zap.String("hash", hex.EncodeToString(msg)),
 			zap.Uint64("height", height),
 			zap.String("chainID", string(chainID)),
 		)
 
 		return nil, eotstypes.ErrDoubleSign
 	}
 
-	privRand, _, err := lm.getRandomnessPair(fpPk, chainID, height, passphrase)
+	privRand, _, err := lm.getRandomnessPair(eotsPk, chainID, height, passphrase)
 	if err != nil {
 		return nil, fmt.Errorf("failed to get private randomness: %w", err)
 	}
 
-	privKey, err := lm.getEOTSPrivKey(fpPk, passphrase)
+	privKey, err := lm.getEOTSPrivKey(eotsPk, passphrase)
 	if err != nil {
 		return nil, fmt.Errorf("failed to get EOTS private key: %w", err)
 	}
 
 	// Update metrics
-	lm.metrics.IncrementEotsFpTotalEotsSignCounter(hex.EncodeToString(fpPk))
-	lm.metrics.SetEotsFpLastEotsSignHeight(hex.EncodeToString(fpPk), float64(height))
+	lm.metrics.IncrementEotsFpTotalEotsSignCounter(hex.EncodeToString(eotsPk))
+	lm.metrics.SetEotsFpLastEotsSignHeight(hex.EncodeToString(eotsPk), float64(height))
 
 	signedBytes, err := eots.Sign(privKey, privRand, msg)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to sign eots")
 	}
 
 	b := signedBytes.Bytes()
-	if err := lm.es.SaveSignRecord(height, msg, fpPk, b[:]); err != nil {
+	if err := lm.es.SaveSignRecord(height, chainID, msg, eotsPk, b[:]); err != nil {
 		return nil, fmt.Errorf("failed to save signing record: %w", err)
 	}
 

eotsmanager/localmanager_test.go

@@ -6,7 +6,9 @@ import (
 	"path/filepath"
 	"testing"
 
+	"github.com/babylonlabs-io/babylon/crypto/eots"
 	"github.com/babylonlabs-io/babylon/testutil/datagen"
+	bbntypes "github.com/babylonlabs-io/babylon/types"
 	"github.com/stretchr/testify/require"
 	"go.uber.org/zap"
 
@@ -98,7 +100,6 @@ func FuzzSignRecord(f *testing.F) {
 	f.Fuzz(func(t *testing.T, seed int64) {
 		r := rand.New(rand.NewSource(seed))
 
-		fpName := testutil.GenRandomHexStr(r, 4)
 		homeDir := filepath.Join(t.TempDir(), "eots-home")
 		eotsCfg := eotscfg.DefaultConfigWithHomePath(homeDir)
 		dbBackend, err := eotsCfg.DatabaseConfig.GetDBBackend()
@@ -111,29 +112,41 @@ func FuzzSignRecord(f *testing.F) {
 		lm, err := eotsmanager.NewLocalEOTSManager(homeDir, eotsCfg.KeyringBackend, dbBackend, zap.NewNop())
 		require.NoError(t, err)
 
-		fpPk, err := lm.CreateKey(fpName, passphrase, hdPath)
-		require.NoError(t, err)
-
-		chainID := datagen.GenRandomByteArray(r, 10)
 		startHeight := datagen.RandomInt(r, 100)
-		num := r.Intn(10) + 1
-		pubRandList, err := lm.CreateRandomnessPairList(fpPk, chainID, startHeight, uint32(num), passphrase)
-		require.NoError(t, err)
-		require.Len(t, pubRandList, num)
+		numRand := r.Intn(10) + 1
 
 		msg := datagen.GenRandomByteArray(r, 32)
+		numFps := 3
+		for i := 0; i < numFps; i++ {
+			chainID := datagen.GenRandomByteArray(r, 10)
+			fpName := testutil.GenRandomHexStr(r, 4)
+			fpPk, err := lm.CreateKey(fpName, passphrase, hdPath)
+			require.NoError(t, err)
+			pubRandList, err := lm.CreateRandomnessPairList(fpPk, chainID, startHeight, uint32(numRand), passphrase)
+			require.NoError(t, err)
+			require.Len(t, pubRandList, numRand)
 
-		sig, err := lm.SignEOTS(fpPk, chainID, msg, startHeight, passphrase)
-		require.NoError(t, err)
-		require.NotNil(t, sig)
+			sig, err := lm.SignEOTS(fpPk, chainID, msg, startHeight, passphrase)
+			require.NoError(t, err)
+			require.NotNil(t, sig)
 
-		// we expect return from db
-		sig2, err := lm.SignEOTS(fpPk, chainID, msg, startHeight, passphrase)
-		require.NoError(t, err)
-		require.Equal(t, sig, sig2)
+			eotsPk, err := bbntypes.NewBIP340PubKey(fpPk)
+			require.NoError(t, err)
+
+			err = eots.Verify(eotsPk.MustToBTCPK(), pubRandList[0], msg, sig)
+			require.NoError(t, err)
+
+			// we expect return from db
+			sig2, err := lm.SignEOTS(fpPk, chainID, msg, startHeight, passphrase)
+			require.NoError(t, err)
+			require.Equal(t, sig, sig2)
 
-		// same height diff msg
-		_, err = lm.SignEOTS(fpPk, chainID, datagen.GenRandomByteArray(r, 32), startHeight, passphrase)
-		require.ErrorIs(t, err, types.ErrDoubleSign)
+			err = eots.Verify(eotsPk.MustToBTCPK(), pubRandList[0], msg, sig2)
+			require.NoError(t, err)
+
+			// same height diff msg
+			_, err = lm.SignEOTS(fpPk, chainID, datagen.GenRandomByteArray(r, 32), startHeight, passphrase)
+			require.ErrorIs(t, err, types.ErrDoubleSign)
+		}
 	})
 }

eotsmanager/proto/signstore.proto

@@ -5,9 +5,12 @@ package proto;
 option go_package = "github.com/babylonlabs-io/finality-provider/eotsmanager/proto";
 
 // SigningRecord represents a record of a signing operation.
+// it is keyed by (chain_id || public_key || height)
 message SigningRecord {
-  bytes block_hash = 1;     // The hash of the block.
-  bytes public_key = 2;     // The public key used for signing.
-  bytes signature = 3;      // The signature of the block.
-  int64 timestamp = 4;      // The timestamp of the signing operation, in Unix seconds.
-}
+  // msg is the message that the signature is signed over
+  bytes msg = 1;
+  // eots_sig is the eots signature
+  bytes eots_sig = 2;
+  // timestamp is the timestamp of the signing operation, in Unix seconds.
+  int64 timestamp = 3;
+}

eotsmanager/store/eotsstore.go

@@ -1,13 +1,14 @@
 package store
 
 import (
-	"encoding/binary"
 	"errors"
 	"fmt"
-	"github.com/babylonlabs-io/finality-provider/eotsmanager/proto"
-	pm "google.golang.org/protobuf/proto"
 	"time"
 
+	pm "google.golang.org/protobuf/proto"
+
+	"github.com/babylonlabs-io/finality-provider/eotsmanager/proto"
+
 	"github.com/btcsuite/btcd/btcec/v2"
 	"github.com/btcsuite/btcd/btcec/v2/schnorr"
 	"github.com/btcsuite/btcwallet/walletdb"
@@ -107,11 +108,12 @@ func (s *EOTSStore) GetEOTSKeyName(pk []byte) (string, error) {
 
 func (s *EOTSStore) SaveSignRecord(
 	height uint64,
-	blockHash []byte,
+	chainID []byte,
+	msg []byte,
 	publicKey []byte,
 	signature []byte,
 ) error {
-	key := uint64ToBytes(height)
+	key := getSignRecordKey(chainID, publicKey, height)
 
 	return kvdb.Batch(s.db, func(tx kvdb.RwTx) error {
 		bucket := tx.ReadWriteBucket(signRecordBucketName)
@@ -124,9 +126,8 @@ func (s *EOTSStore) SaveSignRecord(
 		}
 
 		signRecord := &proto.SigningRecord{
-			BlockHash: blockHash,
-			PublicKey: publicKey,
-			Signature: signature,
+			Msg:       msg,
+			EotsSig:   signature,
 			Timestamp: time.Now().UnixMilli(),
 		}
 
@@ -139,8 +140,8 @@ func (s *EOTSStore) SaveSignRecord(
 	})
 }
 
-func (s *EOTSStore) GetSignRecord(height uint64) (*SigningRecord, bool, error) {
-	key := uint64ToBytes(height)
+func (s *EOTSStore) GetSignRecord(eotsPk, chainID []byte, height uint64) (*SigningRecord, bool, error) {
+	key := getSignRecordKey(chainID, eotsPk, height)
 	protoRes := &proto.SigningRecord{}
 
 	err := s.db.View(func(tx kvdb.RTx) error {
@@ -169,10 +170,3 @@ func (s *EOTSStore) GetSignRecord(height uint64) (*SigningRecord, bool, error) {
 
 	return res, true, nil
 }
-
-// Converts an uint64 value to a byte slice.
-func uint64ToBytes(v uint64) []byte {
-	var buf [8]byte
-	binary.BigEndian.PutUint64(buf[:], v)
-	return buf[:]
-}