Check if message payload is signed by the message sender (#853)

* Checking if message is signed by the message sender

consensus/istanbul/core/errors.go

@@ -43,4 +43,6 @@ var (
 	errFailedDecodeCommit = errors.New("failed to decode COMMIT")
 	// errFailedDecodeMessageSet is returned when the message set is malformed.
 	errFailedDecodeMessageSet = errors.New("failed to decode message set")
+	// errInvalidSigner is returned when the message is signed by a validator different than message sender
+	errInvalidSigner = errors.New("message not signed by the sender")
 )

consensus/istanbul/core/testbackend_test.go

@@ -109,8 +109,8 @@ func (self *testSystemBackend) Verify(proposal istanbul.Proposal) (time.Duration
 }
 
 func (self *testSystemBackend) Sign(data []byte) ([]byte, error) {
-	testLogger.Warn("not sign any data")
-	return data, nil
+	testLogger.Info("returning current backend address so that CheckValidatorSignature returns the same value")
+	return self.address.Bytes(), nil
 }
 
 func (self *testSystemBackend) CheckSignature([]byte, common.Address, []byte) error {
@@ -118,7 +118,7 @@ func (self *testSystemBackend) CheckSignature([]byte, common.Address, []byte) er
 }
 
 func (self *testSystemBackend) CheckValidatorSignature(data []byte, sig []byte) (common.Address, error) {
-	return common.Address{}, nil
+	return common.BytesToAddress(sig), nil
 }
 
 func (self *testSystemBackend) Hash(b interface{}) common.Hash {

consensus/istanbul/core/types.go

@@ -17,6 +17,7 @@
 package core
 
 import (
+	"bytes"
 	"fmt"
 	"io"
 
@@ -137,10 +138,15 @@ func (m *message) FromPayload(b []byte, validateFn func([]byte, []byte) (common.
 			return err
 		}
 
-		_, err = validateFn(payload, m.Signature)
+		signerAdd, err := validateFn(payload, m.Signature)
+		if err != nil {
+			return err
+		}
+		if bytes.Compare(signerAdd.Bytes(), m.Address.Bytes()) != 0 {
+			return errInvalidSigner
+		}
 	}
-	// Still return the message even the err is not nil
-	return err
+	return nil
 }
 
 func (m *message) Payload() ([]byte, error) {

consensus/istanbul/core/types_test.go

@@ -124,10 +124,11 @@ func testSubjectWithSignature(t *testing.T) {
 
 	subjectPayload, _ := Encode(s)
 	// 1. Encode test
+	address := common.HexToAddress("0x1234567890")
 	m := &message{
 		Code:          msgPreprepare,
 		Msg:           subjectPayload,
-		Address:       common.HexToAddress("0x1234567890"),
+		Address:       address,
 		Signature:     expectedSig,
 		CommittedSeal: []byte{},
 	}
@@ -141,7 +142,7 @@ func testSubjectWithSignature(t *testing.T) {
 	// 2.1 Test normal validate func
 	decodedMsg := new(message)
 	err = decodedMsg.FromPayload(msgPayload, func(data []byte, sig []byte) (common.Address, error) {
-		return common.Address{}, nil
+		return address, nil
 	})
 	if err != nil {
 		t.Errorf("error mismatch: have %v, want nil", err)