Merge pull request #9 from dapperlabs/eoa-hex-decode

EOA hex decode

dappauth.go

@@ -5,7 +5,9 @@ package dappauth
 import (
 	"bytes"
 	"context"
+	"encoding/hex"
 	"fmt"
+	"strings"
 
 	"github.com/dapperlabs/dappauth/ERCs"
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
@@ -83,9 +85,16 @@ func (a *Authenticator) IsAuthorizedSigner(challenge, signature, addrHex string)
 	return magicValue == _ERC1271MagicValue, nil
 }
 
+// See https://github.com/MetaMask/eth-sig-util/issues/60
 func personalMessageHash(message string) []byte {
-	msg := fmt.Sprintf("\x19Ethereum Signed Message:\n%d%s", len(message), message)
-	return ethCrypto.Keccak256([]byte(msg))
+	b, err := hex.DecodeString(strings.TrimPrefix(message, "0x"))
+	// if hex decode was successful, then treat is as a hex string
+	if err == nil {
+		msgToHash := fmt.Sprintf("\x19Ethereum Signed Message:\n%d", len(b))
+		return ethCrypto.Keccak256(append([]byte(msgToHash), b...))
+	}
+	msgToHash := fmt.Sprintf("\x19Ethereum Signed Message:\n%d%s", len(message), message)
+	return ethCrypto.Keccak256([]byte(msgToHash))
 }
 
 func mergeErrors(errEOA error, errCA error) error {

dappauth_test.go

@@ -3,6 +3,7 @@ package dappauth
 import (
 	"crypto/ecdsa"
 	"encoding/hex"
+	"fmt"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -172,6 +173,25 @@ func TestDappAuth(t *testing.T) {
 
 }
 
+// It should decode challenge as utf8 by default when computing EOA personal messages hash
+func TestPersonalMessageDecodeUTF8(t *testing.T) {
+	ethMsgHash := personalMessageHash("foo")
+	eoaHash := hex.EncodeToString(ethMsgHash)
+
+	expectString(fmt.Sprintf("0x%s", eoaHash), "0x76b2e96714d3b5e6eb1d1c509265430b907b44f72b2a22b06fcd4d96372b8565", t)
+}
+
+// It should decode challenge as hex if hex is detected when computing EOA personal messages hash
+// See https://github.com/MetaMask/eth-sig-util/issues/60
+func TestPersonalMessageDecodeHex(t *testing.T) {
+	ethMsgHash := personalMessageHash("0xffff")
+	eoaHash := hex.EncodeToString(ethMsgHash)
+
+	// result if 0xffff is decoded as hex:  13a6aa3102b2d639f36804a2d7c31469618fd7a7907c658a7b2aa91a06e31e47
+	// result if 0xffff is decoded as utf8: 247aefb5d2e5b17fca61f786c779f7388485460c13e51308f88b2ff84ffa6851
+	expectString(fmt.Sprintf("0x%s", eoaHash), "0x13a6aa3102b2d639f36804a2d7c31469618fd7a7907c658a7b2aa91a06e31e47", t)
+}
+
 func generateSignature(isEOA bool, msg string, key *ecdsa.PrivateKey, address common.Address, t *testing.T) string {
 	if isEOA {
 		return signEOAPersonalMessage(msg, key, t)
@@ -212,3 +232,9 @@ func expectBool(actual, expected bool, t *testing.T) {
 		t.Errorf("expected %v to be %v", actual, expected)
 	}
 }
+
+func expectString(actual, expected string, t *testing.T) {
+	if actual != expected {
+		t.Errorf("expected %s to be %s", actual, expected)
+	}
+}