fix about signature recovery identifier range

m0t0k1ch1 · Apr 27, 2018 · f2527fb · f2527fb
1 parent dc93cf3
commit f2527fb
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Showing 3 changed files with 11 additions and 8 deletions.
diff --git a/domain/const.go b/domain/const.go
@@ -1,7 +1,8 @@
 package domain
 
 const (
-	SignatureLength = 65 // bytes
+	SignatureLength                      = 65 // bytes
+	SignatureRecoveryIdentifierRangeBase = 27
 
 	UserNameLengthMin = 1
 	UserNameLengthMax = 16

diff --git a/domain/signature.go b/domain/signature.go
@@ -11,6 +11,12 @@ func (sig Signature) Bytes() []byte {
 	return sig[:]
 }
 
+func (sig *Signature) LowerRecoveryIdentifierRange() {
+	if sig[SignatureLength-1] >= SignatureRecoveryIdentifierRangeBase {
+		sig[SignatureLength-1] -= SignatureRecoveryIdentifierRangeBase
+	}
+}
+
 func NewSignatureFromBytes(sigBytes []byte) Signature {
 	sig := Signature{}
 	copy(sig[:], sigBytes[:])

diff --git a/infrastructure/auth/metamask/service.go b/infrastructure/auth/metamask/service.go
@@ -31,16 +31,12 @@ func (s *service) SetUpChallenge(u *domain.User) error {
 }
 
 func (s *service) VerifyResponse(u *domain.User, responseBytes []byte) error {
-	switch responseBytes[domain.SignatureLength-1] {
-	case 27:
-		responseBytes[domain.SignatureLength-1] = 0
-	case 28:
-		responseBytes[domain.SignatureLength-1] = 1
-	}
+	sig := domain.NewSignatureFromBytes(responseBytes)
+	sig.LowerRecoveryIdentifierRange()
 
 	pubkey, err := crypto.SigToPub(
 		challenge(u.Challenge).signatureHashBytes(),
-		responseBytes,
+		sig.Bytes(),
 	)
 	if err != nil {
 		return err