internal/ethapi: add personal_sign and fix eth_sign to hash message (#2940)

This commit includes several API changes:

- The behavior of eth_sign is changed. It now accepts an arbitrary
  message, prepends the well-known string

        \x19Ethereum Signed Message:\n<length of message>

  hashes the result using keccak256 and calculates the signature of
  the hash. This breaks backwards compatability!
  
- personal_sign(hash, address [, password]) is added. It has the same
  semantics as eth_sign but also accepts a password. The private key
  used to sign the hash is temporarily unlocked in the scope of the
  request.
  
- personal_recover(message, signature) is added and returns the
  address for the account that created a signature.

3 files changed, 6 insertions, 4 deletions

diff --git a/core/types/block_test.go b/core/types/block_test.go
index cdd8431f4..ac7f17c0d 100644
--- a/core/types/block_test.go
+++ b/core/types/block_test.go
@@ -51,7 +51,7 @@ func TestBlockEncoding(t *testing.T) {
 	check("Size", block.Size(), common.StorageSize(len(blockEnc)))
 
 	tx1 := NewTransaction(0, common.HexToAddress("095e7baea6a6c7c4c2dfeb977efac326af552d87"), big.NewInt(10), big.NewInt(50000), big.NewInt(10), nil)
-	tx1, _ = tx1.WithSignature(common.Hex2Bytes("9bea4c4daac7c7c52e093e6a4c35dbbcf8856f1af7b059ba20253e70848d094f8a8fae537ce25ed8cb5af9adac3f141af69bd515bd2ba031522df09b97dd72b100"))
+	tx1, _ = tx1.WithSignature(common.Hex2Bytes("9bea4c4daac7c7c52e093e6a4c35dbbcf8856f1af7b059ba20253e70848d094f8a8fae537ce25ed8cb5af9adac3f141af69bd515bd2ba031522df09b97dd72b11b"))
 	check("len(Transactions)", len(block.Transactions()), 1)
 	check("Transactions[0].Hash", block.Transactions()[0].Hash(), tx1.Hash())
 
diff --git a/core/types/transaction.go b/core/types/transaction.go
index f0512ae7e..ceea4f959 100644
--- a/core/types/transaction.go
+++ b/core/types/transaction.go
@@ -318,6 +318,8 @@ func (tx *Transaction) publicKey(homestead bool) ([]byte, error) {
 	return pub, nil
 }
 
+// WithSignature returns a new transaction with the given signature.
+// This signature needs to be formatted as described in the yellow paper (v+27).
 func (tx *Transaction) WithSignature(sig []byte) (*Transaction, error) {
 	if len(sig) != 65 {
 		panic(fmt.Sprintf("wrong size for signature: got %d, want 65", len(sig)))
@@ -325,13 +327,13 @@ func (tx *Transaction) WithSignature(sig []byte) (*Transaction, error) {
 	cpy := &Transaction{data: tx.data}
 	cpy.data.R = new(big.Int).SetBytes(sig[:32])
 	cpy.data.S = new(big.Int).SetBytes(sig[32:64])
-	cpy.data.V = sig[64] + 27
+	cpy.data.V = sig[64]
 	return cpy, nil
 }
 
 func (tx *Transaction) SignECDSA(prv *ecdsa.PrivateKey) (*Transaction, error) {
 	h := tx.SigHash()
-	sig, err := crypto.Sign(h[:], prv)
+	sig, err := crypto.SignEthereum(h[:], prv)
 	if err != nil {
 		return nil, err
 	}
diff --git a/core/types/transaction_test.go b/core/types/transaction_test.go
index 8b0b02c3e..98a78d221 100644
--- a/core/types/transaction_test.go
+++ b/core/types/transaction_test.go
@@ -46,7 +46,7 @@ var (
 		big.NewInt(1),
 		common.FromHex("5544"),
 	).WithSignature(
-		common.Hex2Bytes("98ff921201554726367d2be8c804a7ff89ccf285ebc57dff8ae4c44b9c19ac4a8887321be575c8095f789dd4c743dfe42c1820f9231f98a962b210e3ac2452a301"),
+		common.Hex2Bytes("98ff921201554726367d2be8c804a7ff89ccf285ebc57dff8ae4c44b9c19ac4a8887321be575c8095f789dd4c743dfe42c1820f9231f98a962b210e3ac2452a31c"),
 	)
 )