Implement ACP-118 Aggregator (#3394)

Signed-off-by: Joshua Kim <[email protected]>
Co-authored-by: Stephen Buttolph <[email protected]>
Co-authored-by: aaronbuchwald <[email protected]>

Author: 3 people

network/p2p/acp118/aggregator.go

@@ -0,0 +1,254 @@
+// Copyright (C) 2019-2024, Ava Labs, Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+package acp118
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"math/big"
+
+	"go.uber.org/zap"
+	"google.golang.org/protobuf/proto"
+
+	"github.com/ava-labs/avalanchego/ids"
+	"github.com/ava-labs/avalanchego/network/p2p"
+	"github.com/ava-labs/avalanchego/proto/pb/sdk"
+	"github.com/ava-labs/avalanchego/utils/crypto/bls"
+	"github.com/ava-labs/avalanchego/utils/logging"
+	"github.com/ava-labs/avalanchego/utils/set"
+	"github.com/ava-labs/avalanchego/vms/platformvm/warp"
+)
+
+var errFailedVerification = errors.New("failed verification")
+
+type indexedValidator struct {
+	*warp.Validator
+	Index int
+}
+
+type result struct {
+	NodeID    ids.NodeID
+	Validator indexedValidator
+	Signature *bls.Signature
+	Err       error
+}
+
+// NewSignatureAggregator returns an instance of SignatureAggregator
+func NewSignatureAggregator(log logging.Logger, client *p2p.Client) *SignatureAggregator {
+	return &SignatureAggregator{
+		log:    log,
+		client: client,
+	}
+}
+
+// SignatureAggregator aggregates validator signatures for warp messages
+type SignatureAggregator struct {
+	log    logging.Logger
+	client *p2p.Client
+}
+
+// AggregateSignatures blocks until quorumNum/quorumDen signatures from
+// validators are requested to be aggregated into a warp message or the context
+// is canceled. Returns the signed message and the amount of stake that signed
+// the message. Caller is responsible for providing a well-formed canonical
+// validator set corresponding to the signer bitset in the message.
+func (s *SignatureAggregator) AggregateSignatures(
+	ctx context.Context,
+	message *warp.Message,
+	justification []byte,
+	validators []*warp.Validator,
+	quorumNum uint64,
+	quorumDen uint64,
+) (
+	_ *warp.Message,
+	aggregatedStake *big.Int,
+	totalStake *big.Int,
+	_ error,
+) {
+	request := &sdk.SignatureRequest{
+		Message:       message.UnsignedMessage.Bytes(),
+		Justification: justification,
+	}
+
+	requestBytes, err := proto.Marshal(request)
+	if err != nil {
+		return nil, nil, nil, fmt.Errorf("failed to marshal signature request: %w", err)
+	}
+
+	nodeIDsToValidator := make(map[ids.NodeID]indexedValidator)
+	// TODO expose concrete type to avoid type casting
+	bitSetSignature, ok := message.Signature.(*warp.BitSetSignature)
+	if !ok {
+		return nil, nil, nil, errors.New("invalid warp signature type")
+	}
+
+	signerBitSet := set.BitsFromBytes(bitSetSignature.Signers)
+
+	nonSigners := make([]ids.NodeID, 0, len(validators))
+	aggregatedStakeWeight := new(big.Int)
+	totalStakeWeight := new(big.Int)
+	for i, validator := range validators {
+		totalStakeWeight.Add(totalStakeWeight, new(big.Int).SetUint64(validator.Weight))
+
+		// Only try to aggregate signatures from validators that are not already in
+		// the signer bit set
+		if signerBitSet.Contains(i) {
+			aggregatedStakeWeight.Add(aggregatedStakeWeight, new(big.Int).SetUint64(validator.Weight))
+			continue
+		}
+
+		v := indexedValidator{
+			Index:     i,
+			Validator: validator,
+		}
+
+		for _, nodeID := range v.NodeIDs {
+			nodeIDsToValidator[nodeID] = v
+		}
+
+		nonSigners = append(nonSigners, v.NodeIDs...)
+	}
+
+	// Account for requested signatures + the signature that was provided
+	signatures := make([]*bls.Signature, 0, len(nonSigners)+1)
+	if bitSetSignature.Signature != [bls.SignatureLen]byte{} {
+		blsSignature, err := bls.SignatureFromBytes(bitSetSignature.Signature[:])
+		if err != nil {
+			return nil, nil, nil, fmt.Errorf("failed to parse bls signature: %w", err)
+		}
+		signatures = append(signatures, blsSignature)
+	}
+
+	results := make(chan result)
+	handler := responseHandler{
+		message:             message,
+		nodeIDsToValidators: nodeIDsToValidator,
+		results:             results,
+	}
+
+	if err := s.client.AppRequest(ctx, set.Of(nonSigners...), requestBytes, handler.HandleResponse); err != nil {
+		return nil, nil, nil, fmt.Errorf("failed to send aggregation request: %w", err)
+	}
+
+	minThreshold := new(big.Int).Mul(totalStakeWeight, new(big.Int).SetUint64(quorumNum))
+	minThreshold.Div(minThreshold, new(big.Int).SetUint64(quorumDen))
+
+	// Block until:
+	// 1. The context is cancelled
+	// 2. We get responses from all validators
+	// 3. The specified security threshold is reached
+	for i := 0; i < len(nonSigners); i++ {
+		select {
+		case <-ctx.Done():
+			// Try to return whatever progress we have if the context is cancelled
+			msg, err := newWarpMessage(message, signerBitSet, signatures)
+			if err != nil {
+				return nil, nil, nil, err
+			}
+
+			return msg, aggregatedStakeWeight, totalStakeWeight, nil
+		case result := <-results:
+			if result.Err != nil {
+				s.log.Debug(
+					"dropping response",
+					zap.Stringer("nodeID", result.NodeID),
+					zap.Error(err),
+				)
+				continue
+			}
+
+			// Validators may share public keys so drop any duplicate signatures
+			if signerBitSet.Contains(result.Validator.Index) {
+				s.log.Debug(
+					"dropping duplicate signature",
+					zap.Stringer("nodeID", result.NodeID),
+					zap.Error(err),
+				)
+				continue
+			}
+
+			signatures = append(signatures, result.Signature)
+			signerBitSet.Add(result.Validator.Index)
+			aggregatedStakeWeight.Add(aggregatedStakeWeight, new(big.Int).SetUint64(result.Validator.Weight))
+
+			if aggregatedStakeWeight.Cmp(minThreshold) != -1 {
+				msg, err := newWarpMessage(message, signerBitSet, signatures)
+				if err != nil {
+					return nil, nil, nil, err
+				}
+
+				return msg, aggregatedStakeWeight, totalStakeWeight, nil
+			}
+		}
+	}
+
+	msg, err := newWarpMessage(message, signerBitSet, signatures)
+	if err != nil {
+		return nil, nil, nil, err
+	}
+
+	return msg, aggregatedStakeWeight, totalStakeWeight, nil
+}
+
+func newWarpMessage(
+	message *warp.Message,
+	signerBitSet set.Bits,
+	signatures []*bls.Signature,
+) (*warp.Message, error) {
+	if len(signatures) == 0 {
+		return message, nil
+	}
+
+	aggregateSignature, err := bls.AggregateSignatures(signatures)
+	if err != nil {
+		return nil, err
+	}
+
+	bitSetSignature := &warp.BitSetSignature{
+		Signers:   signerBitSet.Bytes(),
+		Signature: [bls.SignatureLen]byte{},
+	}
+	copy(bitSetSignature.Signature[:], bls.SignatureToBytes(aggregateSignature))
+
+	return warp.NewMessage(&message.UnsignedMessage, bitSetSignature)
+}
+
+type responseHandler struct {
+	message             *warp.Message
+	nodeIDsToValidators map[ids.NodeID]indexedValidator
+	results             chan result
+}
+
+func (r *responseHandler) HandleResponse(
+	_ context.Context,
+	nodeID ids.NodeID,
+	responseBytes []byte,
+	err error,
+) {
+	validator := r.nodeIDsToValidators[nodeID]
+	if err != nil {
+		r.results <- result{NodeID: nodeID, Validator: validator, Err: err}
+		return
+	}
+
+	response := &sdk.SignatureResponse{}
+	if err := proto.Unmarshal(responseBytes, response); err != nil {
+		r.results <- result{NodeID: nodeID, Validator: validator, Err: err}
+		return
+	}
+
+	signature, err := bls.SignatureFromBytes(response.Signature)
+	if err != nil {
+		r.results <- result{NodeID: nodeID, Validator: validator, Err: err}
+		return
+	}
+
+	if !bls.Verify(validator.PublicKey, signature, r.message.UnsignedMessage.Bytes()) {
+		r.results <- result{NodeID: nodeID, Validator: validator, Err: errFailedVerification}
+		return
+	}
+
+	r.results <- result{NodeID: nodeID, Validator: validator, Signature: signature}
+}