feat: add finality threshold check (#38)

Co-authored-by: Timofey Luin <[email protected]>

Author: mpetrun5

chains/evm/config/config.go

@@ -23,6 +23,7 @@ type EVMConfig struct {
 	CommitteePeriodLength uint64  `default:"256" split_words:"true"`
 	StartingPeriod        uint64  `required:"true" split_words:"true"`
 	ForcePeriod           bool    `default:"false" split_words:"true"`
+	FinalityThreshold     uint64  `default:"342" split_words:"true"`
 }
 
 // LoadEVMConfig loads EVM config from the environment and validates the fields

chains/evm/config/config_test.go

@@ -64,6 +64,7 @@ func (s *EVMConfigTestSuite) Test_LoadEVMConfig_SuccessfulLoad_DefaultValues() {
 		BeaconEndpoint:        "endpoint",
 		StartingPeriod:        500,
 		ForcePeriod:           false,
+		FinalityThreshold:     342,
 	})
 }
 
@@ -83,6 +84,7 @@ func (s *EVMConfigTestSuite) Test_LoadEVMConfig_SuccessfulLoad() {
 	os.Setenv("SPECTRE_DOMAINS_2_ROUTER", "invalid")
 	os.Setenv("SPECTRE_DOMAINS_1_STARTING_PERIOD", "500")
 	os.Setenv("SPECTRE_DOMAINS_1_FORCE_PERIOD", "true")
+	os.Setenv("SPECTRE_DOMAINS_1_FINALITY_THRESHOLD", "382")
 
 	c, err := config.LoadEVMConfig(1)
 
@@ -103,5 +105,6 @@ func (s *EVMConfigTestSuite) Test_LoadEVMConfig_SuccessfulLoad() {
 		BeaconEndpoint:        "endpoint",
 		StartingPeriod:        500,
 		ForcePeriod:           true,
+		FinalityThreshold:     382,
 	})
 }

chains/evm/prover/prover.go

@@ -58,25 +58,32 @@ type Prover struct {
 	beaconClient BeaconClient
 	proverClient ProverClient
 
-	spec Spec
+	spec              Spec
+	finalityThreshold uint64
 }
 
 func NewProver(
 	proverClient ProverClient,
 	beaconClient BeaconClient,
 	lightClient LightClient,
 	spec Spec,
+	finalityTreshold uint64,
 ) *Prover {
 	return &Prover{
-		proverClient: proverClient,
-		spec:         spec,
-		beaconClient: beaconClient,
-		lightClient:  lightClient,
+		proverClient:      proverClient,
+		spec:              spec,
+		beaconClient:      beaconClient,
+		lightClient:       lightClient,
+		finalityThreshold: finalityTreshold,
 	}
 }
 
 // StepProof generates the proof for the sync step
 func (p *Prover) StepProof(args *StepArgs) (*EvmProof[message.SyncStepInput], error) {
+	participation := uint64(CountSetBits(args.Update.SyncAggregate.SyncCommiteeBits))
+	if participation < p.finalityThreshold {
+		return nil, fmt.Errorf("participation %d lower than finality treshold %d", participation, p.finalityThreshold)
+	}
 	updateSzz, err := args.Update.MarshalSSZ()
 	if err != nil {
 		return nil, err
@@ -113,7 +120,7 @@ func (p *Prover) StepProof(args *StepArgs) (*EvmProof[message.SyncStepInput], er
 		Input: message.SyncStepInput{
 			AttestedSlot:         args.Update.AttestedHeader.Header.Slot,
 			FinalizedSlot:        args.Update.FinalizedHeader.Header.Slot,
-			Participation:        uint64(CountSetBits(args.Update.SyncAggregate.SyncCommiteeBits)),
+			Participation:        participation,
 			FinalizedHeaderRoot:  finalizedHeaderRoot,
 			ExecutionPayloadRoot: executionRoot,
 		},
@@ -154,6 +161,7 @@ func (p *Prover) StepArgs() (*StepArgs, error) {
 	if err != nil {
 		return nil, err
 	}
+
 	blockRoot, err := p.beaconClient.BeaconBlockRoot(context.Background(), &api.BeaconBlockRootOpts{
 		Block: fmt.Sprint(update.FinalizedHeader.Header.Slot),
 	})

main.go

@@ -128,7 +128,7 @@ func main() {
 				}
 
 				lightClient := lightclient.NewLightClient(config.BeaconEndpoint)
-				p := prover.NewProver(proverClient, beaconProvider, lightClient, prover.Spec(config.Spec))
+				p := prover.NewProver(proverClient, beaconProvider, lightClient, prover.Spec(config.Spec), config.FinalityThreshold)
 				routerAddress := common.HexToAddress(config.Router)
 				stepHandler := handlers.NewStepEventHandler(msgChan, client, beaconProvider, p, routerAddress, id, domains)
 				rotateHandler := handlers.NewRotateHandler(msgChan, periodStore, p, id, domains, config.CommitteePeriodLength, latestPeriod)