Add signature aggregation helpers

params/protocol_params.go

@@ -169,3 +169,7 @@ var (
 	MinimumDifficulty      = big.NewInt(131072) // The minimum that the difficulty may ever be.
 	DurationLimit          = big.NewInt(13)     // The decision boundary on the blocktime duration used to determine whether difficulty should go up or not.
 )
+
+const (
+	WarpQuorumDenominator uint64 = 100
+)

plugin/evm/vm.go

@@ -37,6 +37,8 @@ import (
 	"github.com/ava-labs/subnet-evm/sync/client/stats"
 	"github.com/ava-labs/subnet-evm/trie"
 	"github.com/ava-labs/subnet-evm/warp"
+	"github.com/ava-labs/subnet-evm/warp/aggregator"
+	warpValidators "github.com/ava-labs/subnet-evm/warp/validators"
 
 	// Force-load tracer engine to trigger registration
 	//
@@ -822,7 +824,8 @@ func (vm *VM) CreateHandlers(context.Context) (map[string]*commonEng.HTTPHandler
 	}
 
 	if vm.config.WarpAPIEnabled {
-		if err := handler.RegisterName("warp", &warp.WarpAPI{Backend: vm.warpBackend}); err != nil {
+		warpAggregator := aggregator.NewAggregator(vm.ctx.SubnetID, warpValidators.NewState(vm.ctx), &aggregator.NetworkSigner{Client: vm.client})
+		if err := handler.RegisterName("warp", warp.NewWarpAPI(vm.warpBackend, warpAggregator)); err != nil {
 			return nil, err
 		}
 		enabledAPIs = append(enabledAPIs, "warp")

warp/aggregator/aggregation_job.go

@@ -0,0 +1,135 @@
+// (c) 2023, Ava Labs, Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+package aggregator
+
+import (
+	"context"
+	"fmt"
+	"sync"
+
+	"github.com/ava-labs/avalanchego/ids"
+	"github.com/ava-labs/avalanchego/snow/validators"
+	"github.com/ava-labs/avalanchego/utils/crypto/bls"
+	"github.com/ava-labs/avalanchego/utils/set"
+	avalancheWarp "github.com/ava-labs/avalanchego/vms/platformvm/warp"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/log"
+)
+
+type signatureAggregationJob struct {
+	// SignatureBackend is assumed to be thread-safe and may be used by multiple signature aggregation jobs concurrently
+	client   SignatureBackend
+	height   uint64
+	subnetID ids.ID
+
+	quorumNum       uint64 // Minimum threshold at which to bother returning the resulting signature
+	cancelQuorumNum uint64 // Threshold at which to cancel further signature fetching
+	quorumDen       uint64 // Denominator to use when checking if we've reached the threshold
+	state           validators.State
+	msg             *avalancheWarp.UnsignedMessage
+}
+
+type AggregateSignatureResult struct {
+	SignatureWeight uint64
+	TotalWeight     uint64
+	Message         *avalancheWarp.Message
+}
+
+func NewSignatureAggregationJob(
+	client SignatureBackend,
+	height uint64,
+	subnetID ids.ID,
+	quorumNum uint64,
+	cancelQuorumNum uint64,
+	quorumDen uint64,
+	state validators.State,
+	msg *avalancheWarp.UnsignedMessage,
+) *signatureAggregationJob {
+	return &signatureAggregationJob{
+		client:          client,
+		height:          height,
+		subnetID:        subnetID,
+		quorumNum:       quorumNum,
+		cancelQuorumNum: cancelQuorumNum,
+		quorumDen:       quorumDen,
+		state:           state,
+		msg:             msg,
+	}
+}
+
+// Execute aggregates signatures for the requested message
+func (a *signatureAggregationJob) Execute(ctx context.Context) (*AggregateSignatureResult, error) {
+	validators, totalWeight, err := avalancheWarp.GetCanonicalValidatorSet(ctx, a.state, a.height, a.subnetID)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get validator set: %w", err)
+	}
+	signatureJobs := make([]*signatureJob, 0, len(validators))
+	for _, validator := range validators {
+		signatureJobs = append(signatureJobs, newSignatureJob(a.client, validator, a.msg))
+	}
+
+	// signatureLock is used to access any of the signature attributes in the goroutines created below
+	signatureLock := sync.Mutex{}
+	blsSignatures := make([]*bls.Signature, 0, len(signatureJobs))
+	bitSet := set.NewBits()
+	signatureWeight := uint64(0)
+
+	// Create a child context to cancel signature fetching if we reach [cancelQuorumNum] threshold
+	signatureFetchCtx, signatureFetchCancel := context.WithCancel(ctx)
+	defer signatureFetchCancel()
+
+	wg := sync.WaitGroup{}
+	for i, signatureJob := range signatureJobs {
+		i := i
+		signatureJob := signatureJob
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			log.Info("Fetching warp signature", "nodeID", signatureJob.nodeID, "index", i)
+			blsSignature, err := signatureJob.Execute(signatureFetchCtx)
+			if err != nil {
+				log.Info("Failed to fetch signature at index %d: %s", i, signatureJob)
+				return
+			}
+			log.Info("Retrieved warp signature", "nodeID", signatureJob.nodeID, "index", i, "signature", hexutil.Bytes(bls.SignatureToBytes(blsSignature)))
+			// Add the signature and check if we've reached the requested threshold
+			signatureLock.Lock()
+			defer signatureLock.Unlock()
+
+			blsSignatures = append(blsSignatures, blsSignature)
+			bitSet.Add(i)
+			log.Info("Updated weight", "totalWeight", signatureWeight+signatureJob.weight, "addedWeight", signatureJob.weight)
+			signatureWeight += signatureJob.weight
+			// If the signature weight meets the requested threshold, cancel signature fetching
+			if err := avalancheWarp.VerifyWeight(signatureWeight, totalWeight, a.cancelQuorumNum, a.quorumDen); err == nil {
+				log.Info("Verify weight passed, exiting aggregation early", "cancelQuorumNum", a.cancelQuorumNum, "totalWeight", totalWeight, "signatureWeight", signatureWeight)
+				signatureFetchCancel()
+			}
+		}()
+	}
+	wg.Wait()
+
+	// If I failed to fetch sufficient signature stake, return an error
+	if err := avalancheWarp.VerifyWeight(signatureWeight, totalWeight, a.quorumNum, a.quorumDen); err != nil {
+		return nil, fmt.Errorf("failed to aggregate signature: %w", err)
+	}
+	// Otherwise, return the aggregate signature
+	aggregateSignature, err := bls.AggregateSignatures(blsSignatures)
+	if err != nil {
+		return nil, fmt.Errorf("failed to aggregate BLS signatures: %w", err)
+	}
+	warpSignature := &avalancheWarp.BitSetSignature{
+		Signers: bitSet.Bytes(),
+	}
+	copy(warpSignature.Signature[:], bls.SignatureToBytes(aggregateSignature))
+	msg, err := avalancheWarp.NewMessage(a.msg, warpSignature)
+	if err != nil {
+		return nil, fmt.Errorf("failed to construct warp message: %w", err)
+	}
+	return &AggregateSignatureResult{
+		Message:         msg,
+		SignatureWeight: signatureWeight,
+		TotalWeight:     totalWeight,
+	}, nil
+}