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Merge pull request #241 from chainbound/naman/feat/flashbot-builder
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Builder: update to new Constraints API
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Jonas Bostoen authored Oct 3, 2024
2 parents 3d62fba + 7802cd9 commit ec41a81
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Showing 14 changed files with 606 additions and 411 deletions.
118 changes: 86 additions & 32 deletions builder/builder/builder.go
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Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,8 @@ const (
)

const (
SubscribeConstraintsPath = "/relay/v1/builder/constraints"
GetConstraintsPath = "/relay/v1/builder/constraints"
SubscribeConstraintsPath = "/relay/v1/builder/constraints_stream"
)

type PubkeyHex string
Expand All @@ -66,7 +67,8 @@ type ValidatorData struct {

type IRelay interface {
SubmitBlock(msg *builderSpec.VersionedSubmitBlockRequest, vd ValidatorData) error
SubmitBlockWithProofs(msg *common.VersionedSubmitBlockRequestWithProofs, vd ValidatorData) error
SubmitBlockWithProofs(msg *types.VersionedSubmitBlockRequestWithProofs, vd ValidatorData) error
GetDelegationsForSlot(nextSlot uint64) (types.SignedDelegations, error)
GetValidatorForSlot(nextSlot uint64) (ValidatorData, error)
Config() RelayConfig
Start() error
Expand Down Expand Up @@ -100,10 +102,11 @@ type Builder struct {
limiter *rate.Limiter
submissionOffsetFromEndOfSlot time.Duration

slotMu sync.Mutex
slotAttrs types.BuilderPayloadAttributes
slotCtx context.Context
slotCtxCancel context.CancelFunc
slotMu sync.Mutex
slotConstraintsPubkeys []phase0.BLSPubKey // The pubkey of the authorized constraints signer
slotAttrs types.BuilderPayloadAttributes
slotCtx context.Context
slotCtxCancel context.CancelFunc

stop chan struct{}
}
Expand Down Expand Up @@ -347,7 +350,7 @@ func (b *Builder) subscribeToRelayForConstraints(relayBaseEndpoint string) error

// We assume the data is the JSON representation of the constraints
log.Info(fmt.Sprintf("Received new constraint: %s", data))
constraintsSigned := make(common.SignedConstraintsList, 0, 8)
constraintsSigned := make(types.SignedConstraintsList, 0, 8)
if err := json.Unmarshal([]byte(data), &constraintsSigned); err != nil {
log.Warn(fmt.Sprintf("Failed to unmarshal constraints: %v", err))
continue
Expand All @@ -359,14 +362,29 @@ func (b *Builder) subscribeToRelayForConstraints(relayBaseEndpoint string) error
}

for _, constraint := range constraintsSigned {
oneValidSignature := false
// Check if the signature is valid against any of the authorized pubkeys
for _, pubkey := range b.slotConstraintsPubkeys {
valid, err := constraint.VerifySignature(pubkey, b.GetConstraintsDomain())
if err != nil || !valid {
log.Error("Failed to verify constraint signature", "err", err)
continue
}

oneValidSignature = true
}

// If there is no valid signature, continue with the next constraint
if !oneValidSignature {
continue
}

decodedConstraints, err := DecodeConstraints(constraint)
if err != nil {
log.Error("Failed to decode constraint: ", err)
continue
}

EmitBoltDemoEvent(fmt.Sprintf("Received constraint from relay for slot %d, stored in cache (path: %s)", constraint.Message.Slot, SubscribeConstraintsPath))

// For every constraint, we need to check if it has already been seen for the associated slot
slotConstraints, _ := b.constraintsCache.Get(constraint.Message.Slot)
if len(slotConstraints) == 0 {
Expand All @@ -382,9 +400,7 @@ func (b *Builder) subscribeToRelayForConstraints(relayBaseEndpoint string) error

// Update the slot constraints in the cache
b.constraintsCache.Put(constraint.Message.Slot, slotConstraints)

}

}

return nil
Expand All @@ -395,7 +411,20 @@ func (b *Builder) Stop() error {
return nil
}

// BOLT: modify to calculate merkle inclusion proofs for preconfirmed transactions
// GetConstraintsDomain returns the constraints domain used to sign constraints-API related messages.
//
// The builder signing domain is built as follows:
// - We build a ForkData ssz container with the fork version and the genesis validators root. In the builder domain, this is an empty root.
// - We take the hash tree root of this container and replace the first 4 bytes with the builder domain mask. That gives us the signing domain.
//
// To get the constraints domain, we take the builder domain and replace the first 4 bytes with the constraints domain type.
func (b *Builder) GetConstraintsDomain() phase0.Domain {
domain := b.builderSigningDomain
copy(domain[:4], types.ConstraintsDomainType[:])
return domain
}

// BOLT: modify to calculate merkle inclusion proofs for committed transactions
func (b *Builder) onSealedBlock(opts SubmitBlockOpts) error {
executableData := engine.BlockToExecutableData(opts.Block, opts.BlockValue, opts.BlobSidecars)
var dataVersion spec.DataVersion
Expand Down Expand Up @@ -432,7 +461,7 @@ func (b *Builder) onSealedBlock(opts SubmitBlockOpts) error {
return err
}

var versionedBlockRequestWithPreconfsProofs *common.VersionedSubmitBlockRequestWithProofs
var versionedBlockRequestWithConstraintProofs *types.VersionedSubmitBlockRequestWithProofs

// BOLT: fetch constraints from the cache, which is automatically updated by the SSE subscription
constraints, _ := b.constraintsCache.Get(opts.PayloadAttributes.Slot)
Expand All @@ -441,23 +470,17 @@ func (b *Builder) onSealedBlock(opts SubmitBlockOpts) error {
if len(constraints) > 0 {
message := fmt.Sprintf("sealing block %d with %d constraints", opts.Block.Number(), len(constraints))
log.Info(message)
EmitBoltDemoEvent(message)

timeStart := time.Now()
inclusionProof, _, err := CalculateMerkleMultiProofs(opts.Block.Transactions(), constraints)
timeForProofs := time.Since(timeStart)

if err != nil {
log.Error("[BOLT]: could not calculate merkle multiproofs", "err", err)
return err
}

// BOLT: send event to web demo
EmitBoltDemoEvent(fmt.Sprintf("created merkle multiproof of %d constraint(s) for block %d in %v", len(constraints), opts.Block.Number(), timeForProofs))

versionedBlockRequestWithPreconfsProofs = &common.VersionedSubmitBlockRequestWithProofs{
Inner: versionedBlockRequest,
Proofs: inclusionProof,
versionedBlockRequestWithConstraintProofs = &types.VersionedSubmitBlockRequestWithProofs{
VersionedSubmitBlockRequest: versionedBlockRequest,
Proofs: inclusionProof,
}
}

Expand All @@ -474,13 +497,13 @@ func (b *Builder) onSealedBlock(opts SubmitBlockOpts) error {
log.Error("could not validate block", "version", dataVersion.String(), "err", err)
}
} else {
// NOTE: we can ignore preconfs for `processBuiltBlock`
// NOTE: we can ignore constraints for `processBuiltBlock`
go b.processBuiltBlock(opts.Block, opts.BlockValue, opts.OrdersClosedAt, opts.SealedAt, opts.CommitedBundles, opts.AllBundles, opts.UsedSbundles, &blockBidMsg)
if versionedBlockRequestWithPreconfsProofs != nil {
log.Info(fmt.Sprintf("[BOLT]: Sending sealed block to relay %s", versionedBlockRequestWithPreconfsProofs))
err = b.relay.SubmitBlockWithProofs(versionedBlockRequestWithPreconfsProofs, opts.ValidatorData)
if versionedBlockRequestWithConstraintProofs != nil {
log.Info(fmt.Sprintf("[BOLT]: Sending sealed block to relay %s", versionedBlockRequestWithConstraintProofs))
err = b.relay.SubmitBlockWithProofs(versionedBlockRequestWithConstraintProofs, opts.ValidatorData)
} else if len(constraints) == 0 {
// If versionedBlockRequestWithPreconfsProofs is nil and no constraints, then we don't have proofs to send
// If versionedBlockRequestWithConstraintsProofs is nil and no constraints, then we don't have proofs to send
err = b.relay.SubmitBlock(versionedBlockRequest, opts.ValidatorData)
} else {
log.Warn(fmt.Sprintf("[BOLT]: Could not send sealed block this time because we have %d constraints but no proofs", len(constraints)))
Expand Down Expand Up @@ -570,6 +593,40 @@ func (b *Builder) OnPayloadAttribute(attrs *types.BuilderPayloadAttributes) erro
return fmt.Errorf("could not get validator while submitting block for slot %d - %w", attrs.Slot, err)
}

proposerPubkey, err := utils.HexToPubkey(string(vd.Pubkey))
if err != nil {
return fmt.Errorf("could not parse pubkey (%s) - %w", vd.Pubkey, err)
}

// BOLT: by default, the proposer key is the constraint signer key
pubkey, err := utils.HexToPubkey(string(vd.Pubkey))
if err != nil {
log.Error("could not parse pubkey", "pubkey", vd.Pubkey, "err", err)
}
constraintsPubkeys := []phase0.BLSPubKey{pubkey}

// BOLT: get delegations for the slot
delegations, err := b.relay.GetDelegationsForSlot(attrs.Slot)
if err != nil {
log.Error("could not get delegations for slot, using default validator key", "slot", attrs.Slot, "err", err)
}

if len(delegations) > 0 {
// If there are delegations, reset the constraintsPubkeys (i.e. remove the validator key as authorized)
constraintsPubkeys = make([]phase0.BLSPubKey, 0, len(delegations))
for _, delegation := range delegations {
// Verify signature against the public key
valid, err := delegation.VerifySignature(pubkey, b.GetConstraintsDomain())
if err != nil || !valid {
log.Error("could not verify signature", "err", err)
continue
}

// If signature is valid, add the pubkey to the list of authorized constraint pubkeys
constraintsPubkeys = append(constraintsPubkeys, delegation.Message.DelegateePubkey)
}
}

parentBlock := b.eth.GetBlockByHash(attrs.HeadHash)
if parentBlock == nil {
return fmt.Errorf("parent block hash not found in block tree given head block hash %s", attrs.HeadHash)
Expand All @@ -578,11 +635,6 @@ func (b *Builder) OnPayloadAttribute(attrs *types.BuilderPayloadAttributes) erro
attrs.SuggestedFeeRecipient = [20]byte(vd.FeeRecipient)
attrs.GasLimit = core.CalcGasLimit(parentBlock.GasLimit(), vd.GasLimit)

proposerPubkey, err := utils.HexToPubkey(string(vd.Pubkey))
if err != nil {
return fmt.Errorf("could not parse pubkey (%s) - %w", vd.Pubkey, err)
}

if !b.eth.Synced() {
return errors.New("backend not Synced")
}
Expand All @@ -601,6 +653,8 @@ func (b *Builder) OnPayloadAttribute(attrs *types.BuilderPayloadAttributes) erro

slotCtx, slotCtxCancel := context.WithTimeout(context.Background(), 12*time.Second)
b.slotAttrs = *attrs
// BOLT: save the authorized pubkeys for the upcoming slot
b.slotConstraintsPubkeys = constraintsPubkeys
b.slotCtx = slotCtx
b.slotCtxCancel = slotCtxCancel

Expand Down
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