ethapi: add personal.signTransaction (#15971)

* ethapi: add personal.signTransaction

* ethapi: refactor to minimize duplicate code

* ethapi: make nonce,gas,gasPrice obligatory in signTransaction

internal/ethapi/api.go

@@ -333,28 +333,19 @@ func (s *PrivateAccountAPI) LockAccount(addr common.Address) bool {
 	return fetchKeystore(s.am).Lock(addr) == nil
 }
 
-// SendTransaction will create a transaction from the given arguments and
-// tries to sign it with the key associated with args.To. If the given passwd isn't
-// able to decrypt the key it fails.
-func (s *PrivateAccountAPI) SendTransaction(ctx context.Context, args SendTxArgs, passwd string) (common.Hash, error) {
+// signTransactions sets defaults and signs the given transation
+// NOTE: the caller needs to ensure that the nonceLock is held, if applicable,
+// and release it after the transaction has been submitted to the tx pool
+func (s *PrivateAccountAPI) signTransaction(ctx context.Context, args SendTxArgs, passwd string) (*types.Transaction, error) {
 	// Look up the wallet containing the requested signer
 	account := accounts.Account{Address: args.From}
-
 	wallet, err := s.am.Find(account)
 	if err != nil {
-		return common.Hash{}, err
-	}
-
-	if args.Nonce == nil {
-		// Hold the addresse's mutex around signing to prevent concurrent assignment of
-		// the same nonce to multiple accounts.
-		s.nonceLock.LockAddr(args.From)
-		defer s.nonceLock.UnlockAddr(args.From)
+		return nil, err
 	}
-
 	// Set some sanity defaults and terminate on failure
 	if err := args.setDefaults(ctx, s.b); err != nil {
-		return common.Hash{}, err
+		return nil, err
 	}
 	// Assemble the transaction and sign with the wallet
 	tx := args.toTransaction()
@@ -363,13 +354,53 @@ func (s *PrivateAccountAPI) SendTransaction(ctx context.Context, args SendTxArgs
 	if config := s.b.ChainConfig(); config.IsEIP155(s.b.CurrentBlock().Number()) {
 		chainID = config.ChainId
 	}
-	signed, err := wallet.SignTxWithPassphrase(account, passwd, tx, chainID)
+	return wallet.SignTxWithPassphrase(account, passwd, tx, chainID)
+}
+
+// SendTransaction will create a transaction from the given arguments and
+// tries to sign it with the key associated with args.To. If the given passwd isn't
+// able to decrypt the key it fails.
+func (s *PrivateAccountAPI) SendTransaction(ctx context.Context, args SendTxArgs, passwd string) (common.Hash, error) {
+	if args.Nonce == nil {
+		// Hold the addresse's mutex around signing to prevent concurrent assignment of
+		// the same nonce to multiple accounts.
+		s.nonceLock.LockAddr(args.From)
+		defer s.nonceLock.UnlockAddr(args.From)
+	}
+	signed, err := s.signTransaction(ctx, args, passwd)
 	if err != nil {
 		return common.Hash{}, err
 	}
 	return submitTransaction(ctx, s.b, signed)
 }
 
+// SignTransaction will create a transaction from the given arguments and
+// tries to sign it with the key associated with args.To. If the given passwd isn't
+// able to decrypt the key it fails. The transaction is returned in RLP-form, not broadcast
+// to other nodes
+func (s *PrivateAccountAPI) SignTransaction(ctx context.Context, args SendTxArgs, passwd string) (*SignTransactionResult, error) {
+	// No need to obtain the noncelock mutex, since we won't be sending this
+	// tx into the transaction pool, but right back to the user
+	if args.Gas == nil {
+		return nil, fmt.Errorf("gas not specified")
+	}
+	if args.GasPrice == nil {
+		return nil, fmt.Errorf("gasPrice not specified")
+	}
+	if args.Nonce == nil {
+		return nil, fmt.Errorf("nonce not specified")
+	}
+	signed, err := s.signTransaction(ctx, args, passwd)
+	if err != nil {
+		return nil, err
+	}
+	data, err := rlp.EncodeToBytes(signed)
+	if err != nil {
+		return nil, err
+	}
+	return &SignTransactionResult{data, signed}, nil
+}
+
 // signHash is a helper function that calculates a hash for the given message that can be
 // safely used to calculate a signature from.
 //
@@ -1221,11 +1252,14 @@ type SignTransactionResult struct {
 // The node needs to have the private key of the account corresponding with
 // the given from address and it needs to be unlocked.
 func (s *PublicTransactionPoolAPI) SignTransaction(ctx context.Context, args SendTxArgs) (*SignTransactionResult, error) {
+	if args.Gas == nil {
+		return nil, fmt.Errorf("gas not specified")
+	}
+	if args.GasPrice == nil {
+		return nil, fmt.Errorf("gasPrice not specified")
+	}
 	if args.Nonce == nil {
-		// Hold the addresse's mutex around signing to prevent concurrent assignment of
-		// the same nonce to multiple accounts.
-		s.nonceLock.LockAddr(args.From)
-		defer s.nonceLock.UnlockAddr(args.From)
+		return nil, fmt.Errorf("nonce not specified")
 	}
 	if err := args.setDefaults(ctx, s.b); err != nil {
 		return nil, err

internal/web3ext/web3ext.go

@@ -517,6 +517,12 @@ web3._extend({
 			call: 'personal_deriveAccount',
 			params: 3
 		}),
+		new web3._extend.Method({
+			name: 'signTransaction',
+			call: 'personal_signTransaction',
+			params: 2,
+			inputFormatter: [web3._extend.formatters.inputTransactionFormatter, null]
+		}),
 	],
 	properties: [
 		new web3._extend.Property({