From 42a26000eacd23ca325623c6460a70f5c8d4a50f Mon Sep 17 00:00:00 2001
From: Bas van Kervel <bas@ethdev.com>
Date: Thu, 25 Aug 2016 13:50:47 +0200
Subject: [PATCH] add personal_recover

---
 internal/ethapi/api.go      | 29 +++++++++++++++++++++++++++++
 internal/web3ext/web3ext.go |  5 +++++
 2 files changed, 34 insertions(+)

diff --git a/internal/ethapi/api.go b/internal/ethapi/api.go
index ac78cd1362..c51558e4c6 100644
--- a/internal/ethapi/api.go
+++ b/internal/ethapi/api.go
@@ -312,6 +312,35 @@ func (s *PrivateAccountAPI) Sign(ctx context.Context, message string, addr commo
 	return common.ToHex(signature), nil
 }
 
+// recover returns the address for the account that was used to create the signature.
+//
+// https://github.com/ethereum/go-ethereum/wiki/Management-APIs#personal_recover
+func (s *PrivateAccountAPI) Recover(ctx context.Context, message string, signature string) (common.Address, error) {
+	var (
+		sig  = common.FromHex(signature)
+		hash = crypto.Keccak256(common.FromHex(message))
+	)
+
+	if len(sig) != 65 {
+		return common.Address{}, fmt.Errorf("signature must be 65 bytes long")
+	}
+
+	// see crypto.Ecrecover description
+	if sig[64] == 27 || sig[64] == 28 {
+		sig[64] -= 27
+	}
+
+	rpk, err := crypto.Ecrecover(hash, sig)
+	if err != nil {
+		return common.Address{}, err
+	}
+
+	pubKey := crypto.ToECDSAPub(rpk)
+	recoveredAddr := crypto.PubkeyToAddress(*pubKey)
+
+	return recoveredAddr, nil
+}
+
 // SignAndSendTransaction was renamed to SendTransaction. This method is deprecated
 // and will be removed in the future. It primary goal is to give clients time to update.
 func (s *PrivateAccountAPI) SignAndSendTransaction(ctx context.Context, args SendTxArgs, passwd string) (common.Hash, error) {
diff --git a/internal/web3ext/web3ext.go b/internal/web3ext/web3ext.go
index f7d5e67c66..e201d7c4ae 100644
--- a/internal/web3ext/web3ext.go
+++ b/internal/web3ext/web3ext.go
@@ -434,6 +434,11 @@ web3._extend({
 			call: 'personal_sign',
 			params: 3,
 			inputFormatter: [null, web3._extend.formatters.inputAddressFormatter, null]
+		}),
+		new web3._extend.Method({
+			name: 'recover',
+			call: 'personal_recover',
+			params: 2
 		})
 	]
 })