Delete beacon/types directory

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Isabel Schöps Thiel 2024-01-01 00:35:15 +01:00 committed by GitHub
parent d13fd1b76e
commit 3f5c83c6f6
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GPG key ID: 4AEE18F83AFDEB23
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// Copyright 2023 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package types
import (
"crypto/sha256"
"encoding/json"
"fmt"
"math/bits"
"github.com/ethereum/go-ethereum/beacon/params"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/hexutil"
bls "github.com/protolambda/bls12-381-util"
)
// SerializedSyncCommitteeSize is the size of the sync committee plus the
// aggregate public key.
const SerializedSyncCommitteeSize = (params.SyncCommitteeSize + 1) * params.BLSPubkeySize
// SerializedSyncCommittee is the serialized version of a sync committee
// plus the aggregate public key.
type SerializedSyncCommittee [SerializedSyncCommitteeSize]byte
// jsonSyncCommittee is the JSON representation of a sync committee.
//
// See data structure definition here:
// https://github.com/ethereum/consensus-specs/blob/dev/specs/altair/beacon-chain.md#syncaggregate
type jsonSyncCommittee struct {
Pubkeys []hexutil.Bytes `json:"pubkeys"`
Aggregate hexutil.Bytes `json:"aggregate_pubkey"`
}
// MarshalJSON implements json.Marshaler.
func (s *SerializedSyncCommittee) MarshalJSON() ([]byte, error) {
sc := jsonSyncCommittee{Pubkeys: make([]hexutil.Bytes, params.SyncCommitteeSize)}
for i := range sc.Pubkeys {
sc.Pubkeys[i] = make(hexutil.Bytes, params.BLSPubkeySize)
copy(sc.Pubkeys[i][:], s[i*params.BLSPubkeySize:(i+1)*params.BLSPubkeySize])
}
sc.Aggregate = make(hexutil.Bytes, params.BLSPubkeySize)
copy(sc.Aggregate[:], s[params.SyncCommitteeSize*params.BLSPubkeySize:])
return json.Marshal(&sc)
}
// UnmarshalJSON implements json.Marshaler.
func (s *SerializedSyncCommittee) UnmarshalJSON(input []byte) error {
var sc jsonSyncCommittee
if err := json.Unmarshal(input, &sc); err != nil {
return err
}
if len(sc.Pubkeys) != params.SyncCommitteeSize {
return fmt.Errorf("invalid number of pubkeys %d", len(sc.Pubkeys))
}
for i, key := range sc.Pubkeys {
if len(key) != params.BLSPubkeySize {
return fmt.Errorf("pubkey %d has invalid size %d", i, len(key))
}
copy(s[i*params.BLSPubkeySize:], key[:])
}
if len(sc.Aggregate) != params.BLSPubkeySize {
return fmt.Errorf("invalid aggregate pubkey size %d", len(sc.Aggregate))
}
copy(s[params.SyncCommitteeSize*params.BLSPubkeySize:], sc.Aggregate[:])
return nil
}
// Root calculates the root hash of the binary tree representation of a sync
// committee provided in serialized format.
//
// TODO(zsfelfoldi): Get rid of this when SSZ encoding lands.
func (s *SerializedSyncCommittee) Root() common.Hash {
var (
hasher = sha256.New()
padding [64 - params.BLSPubkeySize]byte
data [params.SyncCommitteeSize]common.Hash
l = params.SyncCommitteeSize
)
for i := range data {
hasher.Reset()
hasher.Write(s[i*params.BLSPubkeySize : (i+1)*params.BLSPubkeySize])
hasher.Write(padding[:])
hasher.Sum(data[i][:0])
}
for l > 1 {
for i := 0; i < l/2; i++ {
hasher.Reset()
hasher.Write(data[i*2][:])
hasher.Write(data[i*2+1][:])
hasher.Sum(data[i][:0])
}
l /= 2
}
hasher.Reset()
hasher.Write(s[SerializedSyncCommitteeSize-params.BLSPubkeySize : SerializedSyncCommitteeSize])
hasher.Write(padding[:])
hasher.Sum(data[1][:0])
hasher.Reset()
hasher.Write(data[0][:])
hasher.Write(data[1][:])
hasher.Sum(data[0][:0])
return data[0]
}
// Deserialize splits open the pubkeys into proper BLS key types.
func (s *SerializedSyncCommittee) Deserialize() (*SyncCommittee, error) {
sc := new(SyncCommittee)
for i := 0; i <= params.SyncCommitteeSize; i++ {
key := new(bls.Pubkey)
var bytes [params.BLSPubkeySize]byte
copy(bytes[:], s[i*params.BLSPubkeySize:(i+1)*params.BLSPubkeySize])
if err := key.Deserialize(&bytes); err != nil {
return nil, err
}
if i < params.SyncCommitteeSize {
sc.keys[i] = key
} else {
sc.aggregate = key
}
}
return sc, nil
}
// SyncCommittee is a set of sync committee signer pubkeys and the aggregate key.
//
// See data structure definition here:
// https://github.com/ethereum/consensus-specs/blob/dev/specs/altair/beacon-chain.md#syncaggregate
type SyncCommittee struct {
keys [params.SyncCommitteeSize]*bls.Pubkey
aggregate *bls.Pubkey
}
// VerifySignature returns true if the given sync aggregate is a valid signature
// or the given hash.
func (sc *SyncCommittee) VerifySignature(signingRoot common.Hash, signature *SyncAggregate) bool {
var (
sig bls.Signature
keys = make([]*bls.Pubkey, 0, params.SyncCommitteeSize)
)
if err := sig.Deserialize(&signature.Signature); err != nil {
return false
}
for i, key := range sc.keys {
if signature.Signers[i/8]&(byte(1)<<(i%8)) != 0 {
keys = append(keys, key)
}
}
return bls.FastAggregateVerify(keys, signingRoot[:], &sig)
}
//go:generate go run github.com/fjl/gencodec -type SyncAggregate -field-override syncAggregateMarshaling -out gen_syncaggregate_json.go
// SyncAggregate represents an aggregated BLS signature with Signers referring
// to a subset of the corresponding sync committee.
//
// See data structure definition here:
// https://github.com/ethereum/consensus-specs/blob/dev/specs/altair/beacon-chain.md#syncaggregate
type SyncAggregate struct {
Signers [params.SyncCommitteeBitmaskSize]byte `gencodec:"required" json:"sync_committee_bits"`
Signature [params.BLSSignatureSize]byte `gencodec:"required" json:"sync_committee_signature"`
}
type syncAggregateMarshaling struct {
Signers hexutil.Bytes
Signature hexutil.Bytes
}
// SignerCount returns the number of signers in the aggregate signature.
func (s *SyncAggregate) SignerCount() int {
var count int
for _, v := range s.Signers {
count += bits.OnesCount8(v)
}
return count
}

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// Copyright 2022 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package types
import (
"crypto/sha256"
"fmt"
"os"
"sort"
"strconv"
"strings"
"github.com/ethereum/go-ethereum/beacon/merkle"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/hexutil"
"gopkg.in/yaml.v3"
)
// syncCommitteeDomain specifies the signatures specific use to avoid clashes
// across signing different data structures.
const syncCommitteeDomain = 7
// Fork describes a single beacon chain fork and also stores the calculated
// signature domain used after this fork.
type Fork struct {
// Name of the fork in the chain config (config.yaml) file{
Name string
// Epoch when given fork version is activated
Epoch uint64
// Fork version, see https://github.com/ethereum/consensus-specs/blob/dev/specs/phase0/beacon-chain.md#custom-types
Version []byte
// calculated by computeDomain, based on fork version and genesis validators root
domain merkle.Value
}
// computeDomain returns the signature domain based on the given fork version
// and genesis validator set root.
func (f *Fork) computeDomain(genesisValidatorsRoot common.Hash) {
var (
hasher = sha256.New()
forkVersion32 merkle.Value
forkDataRoot merkle.Value
)
copy(forkVersion32[:], f.Version)
hasher.Write(forkVersion32[:])
hasher.Write(genesisValidatorsRoot[:])
hasher.Sum(forkDataRoot[:0])
f.domain[0] = syncCommitteeDomain
copy(f.domain[4:], forkDataRoot[:28])
}
// Forks is the list of all beacon chain forks in the chain configuration.
type Forks []*Fork
// domain returns the signature domain for the given epoch (assumes that domains
// have already been calculated).
func (f Forks) domain(epoch uint64) (merkle.Value, error) {
for i := len(f) - 1; i >= 0; i-- {
if epoch >= f[i].Epoch {
return f[i].domain, nil
}
}
return merkle.Value{}, fmt.Errorf("unknown fork for epoch %d", epoch)
}
// SigningRoot calculates the signing root of the given header.
func (f Forks) SigningRoot(header Header) (common.Hash, error) {
domain, err := f.domain(header.Epoch())
if err != nil {
return common.Hash{}, err
}
var (
signingRoot common.Hash
headerHash = header.Hash()
hasher = sha256.New()
)
hasher.Write(headerHash[:])
hasher.Write(domain[:])
hasher.Sum(signingRoot[:0])
return signingRoot, nil
}
func (f Forks) Len() int { return len(f) }
func (f Forks) Swap(i, j int) { f[i], f[j] = f[j], f[i] }
func (f Forks) Less(i, j int) bool { return f[i].Epoch < f[j].Epoch }
// ChainConfig contains the beacon chain configuration.
type ChainConfig struct {
GenesisTime uint64 // Unix timestamp of slot 0
GenesisValidatorsRoot common.Hash // Root hash of the genesis validator set, used for signature domain calculation
Forks Forks
}
// AddFork adds a new item to the list of forks.
func (c *ChainConfig) AddFork(name string, epoch uint64, version []byte) *ChainConfig {
fork := &Fork{
Name: name,
Epoch: epoch,
Version: version,
}
fork.computeDomain(c.GenesisValidatorsRoot)
c.Forks = append(c.Forks, fork)
sort.Sort(c.Forks)
return c
}
// LoadForks parses the beacon chain configuration file (config.yaml) and extracts
// the list of forks.
func (c *ChainConfig) LoadForks(path string) error {
file, err := os.ReadFile(path)
if err != nil {
return fmt.Errorf("failed to read beacon chain config file: %v", err)
}
config := make(map[string]string)
if err := yaml.Unmarshal(file, &config); err != nil {
return fmt.Errorf("failed to parse beacon chain config file: %v", err)
}
var (
versions = make(map[string][]byte)
epochs = make(map[string]uint64)
)
epochs["GENESIS"] = 0
for key, value := range config {
if strings.HasSuffix(key, "_FORK_VERSION") {
name := key[:len(key)-len("_FORK_VERSION")]
if v, err := hexutil.Decode(value); err == nil {
versions[name] = v
} else {
return fmt.Errorf("failed to decode hex fork id %q in beacon chain config file: %v", value, err)
}
}
if strings.HasSuffix(key, "_FORK_EPOCH") {
name := key[:len(key)-len("_FORK_EPOCH")]
if v, err := strconv.ParseUint(value, 10, 64); err == nil {
epochs[name] = v
} else {
return fmt.Errorf("failed to parse epoch number %q in beacon chain config file: %v", value, err)
}
}
}
for name, epoch := range epochs {
if version, ok := versions[name]; ok {
delete(versions, name)
c.AddFork(name, epoch, version)
} else {
return fmt.Errorf("fork id missing for %q in beacon chain config file", name)
}
}
for name := range versions {
return fmt.Errorf("epoch number missing for fork %q in beacon chain config file", name)
}
sort.Sort(c.Forks)
return nil
}

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// Code generated by github.com/fjl/gencodec. DO NOT EDIT.
package types
import (
"encoding/json"
"errors"
"github.com/ethereum/go-ethereum/common"
)
var _ = (*headerMarshaling)(nil)
// MarshalJSON marshals as JSON.
func (h Header) MarshalJSON() ([]byte, error) {
type Header struct {
Slot common.Decimal `gencodec:"required" json:"slot"`
ProposerIndex common.Decimal `gencodec:"required" json:"proposer_index"`
ParentRoot common.Hash `gencodec:"required" json:"parent_root"`
StateRoot common.Hash `gencodec:"required" json:"state_root"`
BodyRoot common.Hash `gencodec:"required" json:"body_root"`
}
var enc Header
enc.Slot = common.Decimal(h.Slot)
enc.ProposerIndex = common.Decimal(h.ProposerIndex)
enc.ParentRoot = h.ParentRoot
enc.StateRoot = h.StateRoot
enc.BodyRoot = h.BodyRoot
return json.Marshal(&enc)
}
// UnmarshalJSON unmarshals from JSON.
func (h *Header) UnmarshalJSON(input []byte) error {
type Header struct {
Slot *common.Decimal `gencodec:"required" json:"slot"`
ProposerIndex *common.Decimal `gencodec:"required" json:"proposer_index"`
ParentRoot *common.Hash `gencodec:"required" json:"parent_root"`
StateRoot *common.Hash `gencodec:"required" json:"state_root"`
BodyRoot *common.Hash `gencodec:"required" json:"body_root"`
}
var dec Header
if err := json.Unmarshal(input, &dec); err != nil {
return err
}
if dec.Slot == nil {
return errors.New("missing required field 'slot' for Header")
}
h.Slot = uint64(*dec.Slot)
if dec.ProposerIndex == nil {
return errors.New("missing required field 'proposer_index' for Header")
}
h.ProposerIndex = uint64(*dec.ProposerIndex)
if dec.ParentRoot == nil {
return errors.New("missing required field 'parent_root' for Header")
}
h.ParentRoot = *dec.ParentRoot
if dec.StateRoot == nil {
return errors.New("missing required field 'state_root' for Header")
}
h.StateRoot = *dec.StateRoot
if dec.BodyRoot == nil {
return errors.New("missing required field 'body_root' for Header")
}
h.BodyRoot = *dec.BodyRoot
return nil
}

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// Code generated by github.com/fjl/gencodec. DO NOT EDIT.
package types
import (
"encoding/json"
"errors"
"github.com/ethereum/go-ethereum/common/hexutil"
)
var _ = (*syncAggregateMarshaling)(nil)
// MarshalJSON marshals as JSON.
func (s SyncAggregate) MarshalJSON() ([]byte, error) {
type SyncAggregate struct {
Signers hexutil.Bytes `gencodec:"required" json:"sync_committee_bits"`
Signature hexutil.Bytes `gencodec:"required" json:"sync_committee_signature"`
}
var enc SyncAggregate
enc.Signers = s.Signers[:]
enc.Signature = s.Signature[:]
return json.Marshal(&enc)
}
// UnmarshalJSON unmarshals from JSON.
func (s *SyncAggregate) UnmarshalJSON(input []byte) error {
type SyncAggregate struct {
Signers *hexutil.Bytes `gencodec:"required" json:"sync_committee_bits"`
Signature *hexutil.Bytes `gencodec:"required" json:"sync_committee_signature"`
}
var dec SyncAggregate
if err := json.Unmarshal(input, &dec); err != nil {
return err
}
if dec.Signers == nil {
return errors.New("missing required field 'sync_committee_bits' for SyncAggregate")
}
if len(*dec.Signers) != len(s.Signers) {
return errors.New("field 'sync_committee_bits' has wrong length, need 64 items")
}
copy(s.Signers[:], *dec.Signers)
if dec.Signature == nil {
return errors.New("missing required field 'sync_committee_signature' for SyncAggregate")
}
if len(*dec.Signature) != len(s.Signature) {
return errors.New("field 'sync_committee_signature' has wrong length, need 96 items")
}
copy(s.Signature[:], *dec.Signature)
return nil
}

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// Copyright 2022 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
// Package types implements a few types of the beacon chain for light client usage.
package types
import (
"crypto/sha256"
"encoding/binary"
"github.com/ethereum/go-ethereum/beacon/merkle"
"github.com/ethereum/go-ethereum/beacon/params"
"github.com/ethereum/go-ethereum/common"
)
//go:generate go run github.com/fjl/gencodec -type Header -field-override headerMarshaling -out gen_header_json.go
const (
headerIndexSlot = 8
headerIndexProposerIndex = 9
headerIndexParentRoot = 10
headerIndexStateRoot = 11
headerIndexBodyRoot = 12
)
// Header defines a beacon header.
//
// See data structure definition here:
// https://github.com/ethereum/consensus-specs/blob/dev/specs/phase0/beacon-chain.md#beaconblockheader
type Header struct {
// Monotonically increasing slot number for the beacon block (may be gapped)
Slot uint64 `gencodec:"required" json:"slot"`
// Index into the validator table who created the beacon block
ProposerIndex uint64 `gencodec:"required" json:"proposer_index"`
// SSZ hash of the parent beacon header
ParentRoot common.Hash `gencodec:"required" json:"parent_root"`
// SSZ hash of the beacon state (https://github.com/ethereum/consensus-specs/blob/dev/specs/bellatrix/beacon-chain.md#beacon-state)
StateRoot common.Hash `gencodec:"required" json:"state_root"`
// SSZ hash of the beacon block body (https://github.com/ethereum/consensus-specs/blob/dev/specs/bellatrix/beacon-chain.md#beaconblockbody)
BodyRoot common.Hash `gencodec:"required" json:"body_root"`
}
// headerMarshaling is a field type overrides for gencodec.
type headerMarshaling struct {
Slot common.Decimal
ProposerIndex common.Decimal
}
// Hash calculates the block root of the header.
//
// TODO(zsfelfoldi): Remove this when an SSZ encoder lands.
func (h *Header) Hash() common.Hash {
var values [16]merkle.Value // values corresponding to indices 8 to 15 of the beacon header tree
binary.LittleEndian.PutUint64(values[headerIndexSlot][:8], h.Slot)
binary.LittleEndian.PutUint64(values[headerIndexProposerIndex][:8], h.ProposerIndex)
values[headerIndexParentRoot] = merkle.Value(h.ParentRoot)
values[headerIndexStateRoot] = merkle.Value(h.StateRoot)
values[headerIndexBodyRoot] = merkle.Value(h.BodyRoot)
hasher := sha256.New()
for i := 7; i > 0; i-- {
hasher.Reset()
hasher.Write(values[i*2][:])
hasher.Write(values[i*2+1][:])
hasher.Sum(values[i][:0])
}
return common.Hash(values[1])
}
// Epoch returns the epoch the header belongs to.
func (h *Header) Epoch() uint64 {
return h.Slot / params.EpochLength
}
// SyncPeriod returns the sync period the header belongs to.
func (h *Header) SyncPeriod() uint64 {
return SyncPeriod(h.Slot)
}
// SyncPeriodStart returns the first slot of the given period.
func SyncPeriodStart(period uint64) uint64 {
return period * params.SyncPeriodLength
}
// SyncPeriod returns the sync period that the given slot belongs to.
func SyncPeriod(slot uint64) uint64 {
return slot / params.SyncPeriodLength
}
// SignedHeader represents a beacon header signed by a sync committee.
//
// This structure is created from either an optimistic update or an instant update:
// - https://github.com/ethereum/consensus-specs/blob/dev/specs/altair/light-client/sync-protocol.md#lightclientoptimisticupdate
// - https://github.com/zsfelfoldi/beacon-APIs/blob/instant_update/apis/beacon/light_client/instant_update.yaml
type SignedHeader struct {
// Beacon header being signed
Header Header
// Sync committee BLS signature aggregate
Signature SyncAggregate
// Slot in which the signature has been created (newer than Header.Slot,
// determines the signing sync committee)
SignatureSlot uint64
}

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// Copyright 2022 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package types
import (
"errors"
"fmt"
"github.com/ethereum/go-ethereum/beacon/merkle"
"github.com/ethereum/go-ethereum/beacon/params"
"github.com/ethereum/go-ethereum/common"
)
// BootstrapData contains a sync committee where light sync can be started,
// together with a proof through a beacon header and corresponding state.
// Note: BootstrapData is fetched from a server based on a known checkpoint hash.
type BootstrapData struct {
Header Header
CommitteeRoot common.Hash
Committee *SerializedSyncCommittee `rlp:"-"`
CommitteeBranch merkle.Values
}
// Validate verifies the proof included in BootstrapData.
func (c *BootstrapData) Validate() error {
if c.CommitteeRoot != c.Committee.Root() {
return errors.New("wrong committee root")
}
return merkle.VerifyProof(c.Header.StateRoot, params.StateIndexSyncCommittee, c.CommitteeBranch, merkle.Value(c.CommitteeRoot))
}
// LightClientUpdate is a proof of the next sync committee root based on a header
// signed by the sync committee of the given period. Optionally, the update can
// prove quasi-finality by the signed header referring to a previous, finalized
// header from the same period, and the finalized header referring to the next
// sync committee root.
//
// See data structure definition here:
// https://github.com/ethereum/consensus-specs/blob/dev/specs/altair/light-client/sync-protocol.md#lightclientupdate
type LightClientUpdate struct {
AttestedHeader SignedHeader // Arbitrary header out of the period signed by the sync committee
NextSyncCommitteeRoot common.Hash // Sync committee of the next period advertised in the current one
NextSyncCommitteeBranch merkle.Values // Proof for the next period's sync committee
FinalizedHeader *Header `rlp:"nil"` // Optional header to announce a point of finality
FinalityBranch merkle.Values // Proof for the announced finality
score *UpdateScore // Weight of the update to compare between competing ones
}
// Validate verifies the validity of the update.
func (update *LightClientUpdate) Validate() error {
period := update.AttestedHeader.Header.SyncPeriod()
if SyncPeriod(update.AttestedHeader.SignatureSlot) != period {
return errors.New("signature slot and signed header are from different periods")
}
if update.FinalizedHeader != nil {
if update.FinalizedHeader.SyncPeriod() != period {
return errors.New("finalized header is from different period")
}
if err := merkle.VerifyProof(update.AttestedHeader.Header.StateRoot, params.StateIndexFinalBlock, update.FinalityBranch, merkle.Value(update.FinalizedHeader.Hash())); err != nil {
return fmt.Errorf("invalid finalized header proof: %w", err)
}
}
if err := merkle.VerifyProof(update.AttestedHeader.Header.StateRoot, params.StateIndexNextSyncCommittee, update.NextSyncCommitteeBranch, merkle.Value(update.NextSyncCommitteeRoot)); err != nil {
return fmt.Errorf("invalid next sync committee proof: %w", err)
}
return nil
}
// Score returns the UpdateScore describing the proof strength of the update
// Note: thread safety can be ensured by always calling Score on a newly received
// or decoded update before making it potentially available for other threads
func (update *LightClientUpdate) Score() UpdateScore {
if update.score == nil {
update.score = &UpdateScore{
SignerCount: uint32(update.AttestedHeader.Signature.SignerCount()),
SubPeriodIndex: uint32(update.AttestedHeader.Header.Slot & 0x1fff),
FinalizedHeader: update.FinalizedHeader != nil,
}
}
return *update.score
}
// UpdateScore allows the comparison between updates at the same period in order
// to find the best update chain that provides the strongest proof of being canonical.
//
// UpdateScores have a tightly packed binary encoding format for efficient p2p
// protocol transmission. Each UpdateScore is encoded in 3 bytes.
// When interpreted as a 24 bit little indian unsigned integer:
// - the lowest 10 bits contain the number of signers in the header signature aggregate
// - the next 13 bits contain the "sub-period index" which is he signed header's
// slot modulo params.SyncPeriodLength (which is correlated with the risk of the chain being
// re-orged before the previous period boundary in case of non-finalized updates)
// - the highest bit is set when the update is finalized (meaning that the finality
// header referenced by the signed header is in the same period as the signed
// header, making reorgs before the period boundary impossible
type UpdateScore struct {
SignerCount uint32 // number of signers in the header signature aggregate
SubPeriodIndex uint32 // signed header's slot modulo params.SyncPeriodLength
FinalizedHeader bool // update is considered finalized if has finalized header from the same period and 2/3 signatures
}
// finalized returns true if the update has a header signed by at least 2/3 of
// the committee, referring to a finalized header that refers to the next sync
// committee. This condition is a close approximation of the actual finality
// condition that can only be verified by full beacon nodes.
func (u *UpdateScore) finalized() bool {
return u.FinalizedHeader && u.SignerCount >= params.SyncCommitteeSupermajority
}
// BetterThan returns true if update u is considered better than w.
func (u UpdateScore) BetterThan(w UpdateScore) bool {
var (
uFinalized = u.finalized()
wFinalized = w.finalized()
)
if uFinalized != wFinalized {
return uFinalized
}
return u.SignerCount > w.SignerCount
}