core: vm: cache GPK to prevent DoS (#335)

Cache GPK so one can not slow the chain down with the ProposeCRS method
call.

2 files changed, 34 insertions, 17 deletions

diff --git a/core/vm/oracle_contracts.go b/core/vm/oracle_contracts.go
index 10459a870..c63c750a3 100644
--- a/core/vm/oracle_contracts.go
+++ b/core/vm/oracle_contracts.go
@@ -24,6 +24,7 @@ import (
 	"math"
 	"math/big"
 	"sort"
+	"sync/atomic"
 
 	"github.com/dexon-foundation/dexon/accounts/abi"
 	"github.com/dexon-foundation/dexon/common"
@@ -1248,16 +1249,32 @@ type GovernanceContract struct {
 
 // defaultCoreDKGUtils implements coreDKGUtils.
 type defaultCoreDKGUtils struct {
+	gpk atomic.Value
 }
 
 func (c *defaultCoreDKGUtils) NewGroupPublicKey(
 	state *GovernanceState, round *big.Int, threshold int) (tsigVerifierIntf, error) {
+	var gpk *dkgTypes.GroupPublicKey
+	var err error
+
+	v := c.gpk.Load()
+	if v != nil {
+		gpk = v.(*dkgTypes.GroupPublicKey)
+		if gpk.Round == round.Uint64() {
+			return gpk, nil
+		}
+	}
 
 	// Prepare DKGMasterPublicKeys.
 	mpks := state.DKGMasterPublicKeyItems()
 	comps := state.DKGComplaintItems()
 
-	return dkgTypes.NewGroupPublicKey(round.Uint64(), mpks, comps, threshold)
+	gpk, err = dkgTypes.NewGroupPublicKey(round.Uint64(), mpks, comps, threshold)
+	if err != nil {
+		return nil, err
+	}
+	c.gpk.Store(gpk)
+	return gpk, nil
 }
 
 func (g *GovernanceContract) Address() common.Address {
diff --git a/dex/governance.go b/dex/governance.go
index 0614ae910..b8dcf1589 100644
--- a/dex/governance.go
+++ b/dex/governance.go
@@ -111,13 +111,13 @@ func (d *DexconGovernance) Round() uint64 {
 func (d *DexconGovernance) ProposeCRS(round uint64, signedCRS []byte) {
 	data, err := vm.PackProposeCRS(round, signedCRS)
 	if err != nil {
-		log.Error("failed to pack proposeCRS input", "err", err)
+		log.Error("Failed to pack proposeCRS input", "err", err)
 		return
 	}
 
 	err = d.sendGovTx(context.Background(), data)
 	if err != nil {
-		log.Error("failed to send proposeCRS tx", "err", err)
+		log.Error("Failed to send proposeCRS tx", "err", err)
 	}
 }
 
@@ -125,13 +125,13 @@ func (d *DexconGovernance) ProposeCRS(round uint64, signedCRS []byte) {
 func (d *DexconGovernance) AddDKGComplaint(complaint *dkgTypes.Complaint) {
 	data, err := vm.PackAddDKGComplaint(complaint)
 	if err != nil {
-		log.Error("failed to pack addDKGComplaint input", "err", err)
+		log.Error("Failed to pack addDKGComplaint input", "err", err)
 		return
 	}
 
 	err = d.sendGovTx(context.Background(), data)
 	if err != nil {
-		log.Error("failed to send addDKGComplaint tx", "err", err)
+		log.Error("Failed to send addDKGComplaint tx", "err", err)
 	}
 }
 
@@ -139,13 +139,13 @@ func (d *DexconGovernance) AddDKGComplaint(complaint *dkgTypes.Complaint) {
 func (d *DexconGovernance) AddDKGMasterPublicKey(masterPublicKey *dkgTypes.MasterPublicKey) {
 	data, err := vm.PackAddDKGMasterPublicKey(masterPublicKey)
 	if err != nil {
-		log.Error("failed to pack addDKGMasterPublicKey input", "err", err)
+		log.Error("Failed to pack addDKGMasterPublicKey input", "err", err)
 		return
 	}
 
 	err = d.sendGovTx(context.Background(), data)
 	if err != nil {
-		log.Error("failed to send addDKGMasterPublicKey tx", "err", err)
+		log.Error("Failed to send addDKGMasterPublicKey tx", "err", err)
 	}
 }
 
@@ -153,13 +153,13 @@ func (d *DexconGovernance) AddDKGMasterPublicKey(masterPublicKey *dkgTypes.Maste
 func (d *DexconGovernance) AddDKGMPKReady(ready *dkgTypes.MPKReady) {
 	data, err := vm.PackAddDKGMPKReady(ready)
 	if err != nil {
-		log.Error("failed to pack addDKGMPKReady input", "err", err)
+		log.Error("Failed to pack addDKGMPKReady input", "err", err)
 		return
 	}
 
 	err = d.sendGovTx(context.Background(), data)
 	if err != nil {
-		log.Error("failed to send addDKGMPKReady tx", "err", err)
+		log.Error("Failed to send addDKGMPKReady tx", "err", err)
 	}
 }
 
@@ -167,13 +167,13 @@ func (d *DexconGovernance) AddDKGMPKReady(ready *dkgTypes.MPKReady) {
 func (d *DexconGovernance) AddDKGFinalize(final *dkgTypes.Finalize) {
 	data, err := vm.PackAddDKGFinalize(final)
 	if err != nil {
-		log.Error("failed to pack addDKGFinalize input", "err", err)
+		log.Error("Failed to pack addDKGFinalize input", "err", err)
 		return
 	}
 
 	err = d.sendGovTx(context.Background(), data)
 	if err != nil {
-		log.Error("failed to send addDKGFinalize tx", "err", err)
+		log.Error("Failed to send addDKGFinalize tx", "err", err)
 	}
 }
 
@@ -181,13 +181,13 @@ func (d *DexconGovernance) AddDKGFinalize(final *dkgTypes.Finalize) {
 func (d *DexconGovernance) ReportForkVote(vote1, vote2 *coreTypes.Vote) {
 	data, err := vm.PackReportForkVote(vote1, vote2)
 	if err != nil {
-		log.Error("failed to pack report fork vote input", "err", err)
+		log.Error("Failed to pack report fork vote input", "err", err)
 		return
 	}
 
 	err = d.sendGovTx(context.Background(), data)
 	if err != nil {
-		log.Error("failed to send report fork vote tx", "err", err)
+		log.Error("Failed to send report fork vote tx", "err", err)
 	}
 }
 
@@ -195,25 +195,25 @@ func (d *DexconGovernance) ReportForkVote(vote1, vote2 *coreTypes.Vote) {
 func (d *DexconGovernance) ReportForkBlock(block1, block2 *coreTypes.Block) {
 	data, err := vm.PackReportForkBlock(block1, block2)
 	if err != nil {
-		log.Error("failed to pack report fork block input", "err", err)
+		log.Error("Failed to pack report fork block input", "err", err)
 		return
 	}
 
 	err = d.sendGovTx(context.Background(), data)
 	if err != nil {
-		log.Error("failed to send report fork block tx", "err", err)
+		log.Error("Failed to send report fork block tx", "err", err)
 	}
 }
 
 func (d *DexconGovernance) ResetDKG(newSignedCRS []byte) {
 	data, err := vm.PackResetDKG(newSignedCRS)
 	if err != nil {
-		log.Error("failed to pack resetDKG input", "err", err)
+		log.Error("Failed to pack resetDKG input", "err", err)
 		return
 	}
 
 	err = d.sendGovTx(context.Background(), data)
 	if err != nil {
-		log.Error("failed to send resetDKG tx", "err", err)
+		log.Error("Failed to send resetDKG tx", "err", err)
 	}
 }