consensus/clique: implement getSignerForBlock

consensus/clique/api.go

@@ -17,11 +17,15 @@
 package clique
 
 import (
+	"bytes"
+	"errors"
 	"fmt"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/rpc"
 )
 
@@ -175,3 +179,54 @@ func (api *API) Status() (*status, error) {
 		NumBlocks:     numBlocks,
 	}, nil
 }
+
+type SignerBlock struct {
+	*rpc.BlockNumberOrHash
+	RLP string `json:"rlp,omitempty"`
+}
+
+// GetSigner returns the signer for a specific clique block.
+// Can be called with either a blocknumber, blockhash or an rlp encoded blob.
+// The RLP encoded blob can either be a block or a header.
+func (api *API) GetSigner(rlpOrBlockNr *SignerBlock) (common.Address, error) {
+	if len(rlpOrBlockNr.RLP) == 0 {
+		blockNrOrHash := rlpOrBlockNr.BlockNumberOrHash
+		var header *types.Header
+		if blockNrOrHash == nil {
+			header = api.chain.CurrentHeader()
+		} else if hash, ok := blockNrOrHash.Hash(); ok {
+			header = api.chain.GetHeaderByHash(hash)
+		} else if number, ok := blockNrOrHash.Number(); ok {
+			header = api.chain.GetHeaderByNumber(uint64(number.Int64()))
+		}
+		return getSigner(header)
+	}
+	blob := common.Hex2Bytes(rlpOrBlockNr.RLP)
+	block := new(types.Block)
+	if err := rlp.Decode(bytes.NewReader(blob), block); err == nil {
+		return getSigner(block.Header())
+	}
+	header := new(types.Header)
+	if err := rlp.Decode(bytes.NewReader(blob), header); err == nil {
+		return getSigner(header)
+	}
+	return common.Address{}, fmt.Errorf("could not decode rlp")
+}
+
+func getSigner(header *types.Header) (common.Address, error) {
+	if header == nil {
+		return common.Address{}, errors.New("could not find header")
+	}
+	if len(header.Extra)-extraSeal < 0 {
+		return common.Address{}, errors.New("invalid extra data in header")
+	}
+	signature := header.Extra[len(header.Extra)-extraSeal:]
+	// Recover the public key and the Ethereum address
+	pubkey, err := crypto.Ecrecover(SealHash(header).Bytes(), signature)
+	if err != nil {
+		return common.Address{}, err
+	}
+	var signer common.Address
+	copy(signer[:], crypto.Keccak256(pubkey[1:])[12:])
+	return signer, nil
+}

internal/web3ext/web3ext.go

@@ -108,6 +108,12 @@ web3._extend({
 			call: 'clique_status',
 			params: 0
 		}),
+		new web3._extend.Method({
+			name: 'getSigner',
+			call: 'clique_getSigner',
+			params: 1,
+			inputFormatter: [web3._extend.formatters.inputBlockNumberFormatter]
+		}),
 	],
 	properties: [
 		new web3._extend.Property({