Added the limit of the maximum number of hashes that can be requested…

… in a ListOffChainData call (#91)

services/datacom/datacom.go

@@ -40,9 +40,11 @@ func (d *Endpoints) SignSequence(signedSequence types.SignedSequence) (interface
 	if err != nil {
 		return "0x0", rpc.NewRPCError(rpc.DefaultErrorCode, "failed to verify sender")
 	}
+
 	if sender != d.sequencerTracker.GetAddr() {
 		return "0x0", rpc.NewRPCError(rpc.DefaultErrorCode, "unauthorized")
 	}
+
 	// Store off-chain data by hash (hash(L2Data): L2Data)
 	_, err = d.txMan.NewDbTxScope(d.db, func(ctx context.Context, dbTx db.Tx) (interface{}, rpc.Error) {
 		err := d.db.StoreOffChainData(ctx, signedSequence.Sequence.OffChainData(), dbTx)
@@ -55,11 +57,12 @@ func (d *Endpoints) SignSequence(signedSequence types.SignedSequence) (interface
 	if err != nil {
 		return "0x0", rpc.NewRPCError(rpc.DefaultErrorCode, err.Error())
 	}
+
 	// Sign
 	signedSequenceByMe, err := signedSequence.Sequence.Sign(d.privateKey)
 	if err != nil {
 		return "0x0", rpc.NewRPCError(rpc.DefaultErrorCode, fmt.Errorf("failed to sign. Error: %w", err).Error())
 	}
-	// Return signature
+
 	return signedSequenceByMe.Signature, nil
 }

services/sync/sync.go

@@ -10,8 +10,13 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 )
 
-// APISYNC  is the namespace of the sync service
-const APISYNC = "sync"
+const (
+	// APISYNC  is the namespace of the sync service
+	APISYNC = "sync"
+
+	// maxListHashes is the maximum number of hashes that can be requested in a ListOffChainData call
+	maxListHashes = 100
+)
 
 // Endpoints contains implementations for the "zkevm" RPC endpoints
 type Endpoints struct {
@@ -41,6 +46,11 @@ func (z *Endpoints) GetOffChainData(hash types.ArgHash) (interface{}, rpc.Error)
 
 // ListOffChainData returns the list of images of the given hashes
 func (z *Endpoints) ListOffChainData(hashes []types.ArgHash) (interface{}, rpc.Error) {
+	if len(hashes) > maxListHashes {
+		log.Errorf("too many hashes requested in ListOffChainData: %d", len(hashes))
+		return "0x0", rpc.NewRPCError(rpc.InvalidRequestErrorCode, "too many hashes requested")
+	}
+
 	keys := make([]common.Hash, len(hashes))
 	for i, hash := range hashes {
 		keys[i] = hash.Hash()