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- // Copyright 2019 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 checkpointoracle is a wrapper of checkpoint oracle contract with
- // additional rules defined. This package can be used both in LES client or
- // server side for offering oracle related APIs.
- package checkpointoracle
- import (
- "encoding/binary"
- "sync"
- "sync/atomic"
- "time"
- "github.com/ethereum/go-ethereum/accounts/abi/bind"
- "github.com/ethereum/go-ethereum/common"
- "github.com/ethereum/go-ethereum/contracts/checkpointoracle"
- "github.com/ethereum/go-ethereum/crypto"
- "github.com/ethereum/go-ethereum/log"
- "github.com/ethereum/go-ethereum/params"
- )
- // CheckpointOracle is responsible for offering the latest stable checkpoint
- // generated and announced by the contract admins on-chain. The checkpoint can
- // be verified by clients locally during the checkpoint syncing.
- type CheckpointOracle struct {
- config *params.CheckpointOracleConfig
- contract *checkpointoracle.CheckpointOracle
- running int32 // Flag whether the contract backend is set or not
- getLocal func(uint64) params.TrustedCheckpoint // Function used to retrieve local checkpoint
- checkMu sync.Mutex // Mutex to sync access to the fields below
- lastCheckTime time.Time // Time we last checked the checkpoint
- lastCheckPoint *params.TrustedCheckpoint // The last stable checkpoint
- lastCheckPointHeight uint64 // The height of last stable checkpoint
- }
- // New creates a checkpoint oracle handler with given configs and callback.
- func New(config *params.CheckpointOracleConfig, getLocal func(uint64) params.TrustedCheckpoint) *CheckpointOracle {
- return &CheckpointOracle{
- config: config,
- getLocal: getLocal,
- }
- }
- // Start binds the contract backend, initializes the oracle instance
- // and marks the status as available.
- func (oracle *CheckpointOracle) Start(backend bind.ContractBackend) {
- contract, err := checkpointoracle.NewCheckpointOracle(oracle.config.Address, backend)
- if err != nil {
- log.Error("Oracle contract binding failed", "err", err)
- return
- }
- if !atomic.CompareAndSwapInt32(&oracle.running, 0, 1) {
- log.Error("Already bound and listening to registrar")
- return
- }
- oracle.contract = contract
- }
- // IsRunning returns an indicator whether the oracle is running.
- func (oracle *CheckpointOracle) IsRunning() bool {
- return atomic.LoadInt32(&oracle.running) == 1
- }
- // Contract returns the underlying raw checkpoint oracle contract.
- func (oracle *CheckpointOracle) Contract() *checkpointoracle.CheckpointOracle {
- return oracle.contract
- }
- // StableCheckpoint returns the stable checkpoint which was generated by local
- // indexers and announced by trusted signers.
- func (oracle *CheckpointOracle) StableCheckpoint() (*params.TrustedCheckpoint, uint64) {
- oracle.checkMu.Lock()
- defer oracle.checkMu.Unlock()
- if time.Since(oracle.lastCheckTime) < 1*time.Minute {
- return oracle.lastCheckPoint, oracle.lastCheckPointHeight
- }
- // Look it up properly
- // Retrieve the latest checkpoint from the contract, abort if empty
- latest, hash, height, err := oracle.contract.Contract().GetLatestCheckpoint(nil)
- oracle.lastCheckTime = time.Now()
- if err != nil || (latest == 0 && hash == [32]byte{}) {
- oracle.lastCheckPointHeight = 0
- oracle.lastCheckPoint = nil
- return oracle.lastCheckPoint, oracle.lastCheckPointHeight
- }
- local := oracle.getLocal(latest)
- // The following scenarios may occur:
- //
- // * local node is out of sync so that it doesn't have the
- // checkpoint which registered in the contract.
- // * local checkpoint doesn't match with the registered one.
- //
- // In both cases, no stable checkpoint will be returned.
- if local.HashEqual(hash) {
- oracle.lastCheckPointHeight = height.Uint64()
- oracle.lastCheckPoint = &local
- return oracle.lastCheckPoint, oracle.lastCheckPointHeight
- }
- return nil, 0
- }
- // VerifySigners recovers the signer addresses according to the signature and
- // checks whether there are enough approvals to finalize the checkpoint.
- func (oracle *CheckpointOracle) VerifySigners(index uint64, hash [32]byte, signatures [][]byte) (bool, []common.Address) {
- // Short circuit if the given signatures doesn't reach the threshold.
- if len(signatures) < int(oracle.config.Threshold) {
- return false, nil
- }
- var (
- signers []common.Address
- checked = make(map[common.Address]struct{})
- )
- for i := 0; i < len(signatures); i++ {
- if len(signatures[i]) != 65 {
- continue
- }
- // EIP 191 style signatures
- //
- // Arguments when calculating hash to validate
- // 1: byte(0x19) - the initial 0x19 byte
- // 2: byte(0) - the version byte (data with intended validator)
- // 3: this - the validator address
- // -- Application specific data
- // 4 : checkpoint section_index (uint64)
- // 5 : checkpoint hash (bytes32)
- // hash = keccak256(checkpoint_index, section_head, cht_root, bloom_root)
- buf := make([]byte, 8)
- binary.BigEndian.PutUint64(buf, index)
- data := append([]byte{0x19, 0x00}, append(oracle.config.Address.Bytes(), append(buf, hash[:]...)...)...)
- signatures[i][64] -= 27 // Transform V from 27/28 to 0/1 according to the yellow paper for verification.
- pubkey, err := crypto.Ecrecover(crypto.Keccak256(data), signatures[i])
- if err != nil {
- return false, nil
- }
- var signer common.Address
- copy(signer[:], crypto.Keccak256(pubkey[1:])[12:])
- if _, exist := checked[signer]; exist {
- continue
- }
- for _, s := range oracle.config.Signers {
- if s == signer {
- signers = append(signers, signer)
- checked[signer] = struct{}{}
- }
- }
- }
- threshold := oracle.config.Threshold
- if uint64(len(signers)) < threshold {
- log.Warn("Not enough signers to approve checkpoint", "signers", len(signers), "threshold", threshold)
- return false, nil
- }
- return true, signers
- }
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