consensus/sign.go

package consensus

import (
	"errors"

	"github.com/PlatONnetwork/PlatON-Go/common"
	"github.com/PlatONnetwork/PlatON-Go/core/types"
	"github.com/PlatONnetwork/PlatON-Go/crypto"
	"github.com/PlatONnetwork/PlatON-Go/crypto/sha3"
	"github.com/PlatONnetwork/PlatON-Go/rlp"
	lru "github.com/hashicorp/golang-lru"
)

var (
	// ExtraSeal fixed number of extra-data suffix bytes reserved for signer seal
	ExtraSeal = 65
	// ErrMissingSignature is returned if a block's extra-data section doesn't seem
	// to contain a 65 byte secp256k1 signature.
	ErrMissingSignature = errors.New("extra-data 65 byte signature suffix missing")
)

// SigHash returns the hash which is used as input for the proof-of-authority
// signing. It is the hash of the entire header apart from the 65 byte signature
// contained at the end of the extra data.
//
// Note, the method requires the extra data to be at least 65 bytes, otherwise it
// panics. This is done to avoid accidentally using both forms (signature present
// or not), which could be abused to produce different hashes for the same header.
func SigHash(header *types.Header) (hash common.Hash) {
	hasher := sha3.NewKeccak256()

	rlp.Encode(hasher, []interface{}{
		header.ParentHash,
		header.Coinbase,
		header.Root,
		header.TxHash,
		header.ReceiptHash,
		header.Bloom,
		header.Number,
		header.GasLimit,
		header.GasUsed,
		header.Time,
		header.Extra[:len(header.Extra)-65], // Yes, this will panic if extra is too short
		header.Nonce,
	})
	hasher.Sum(hash[:0])
	return hash
}

// Ecrecover extracts the Ethereum account address from a signed header.
func Ecrecover(header *types.Header, sigcache *lru.ARCCache) (common.Address, error) {
	// If the signature's already cached, return that
	hash := header.Hash()
	if address, known := sigcache.Get(hash); known {
		return address.(common.Address), nil
	}
	// Retrieve the signature from the header extra-data
	if len(header.Extra) < ExtraSeal {
		return common.Address{}, ErrMissingSignature
	}
	signature := header.Extra[len(header.Extra)-ExtraSeal:]

	// Recover the public key and the Ethereum address
	pubkey, err := crypto.Ecrecover(SigHash(header).Bytes(), signature)
	if err != nil {
		return common.Address{}, err
	}
	var signer common.Address
	copy(signer[:], crypto.Keccak256(pubkey[1:])[12:])

	sigcache.Add(hash, signer)
	return signer, nil
}