Merge pull request #2116 from obscuren/homestead

core, core/vm: consensus changes necessary for the homestead release

1 files changed, 11 insertions, 2 deletions

diff --git a/crypto/crypto.go b/crypto/crypto.go
index 7d7623753..850be4da6 100644
--- a/crypto/crypto.go
+++ b/crypto/crypto.go
@@ -163,12 +163,21 @@ func GenerateKey() (*ecdsa.PrivateKey, error) {
 	return ecdsa.GenerateKey(secp256k1.S256(), rand.Reader)
 }
 
-func ValidateSignatureValues(v byte, r, s *big.Int) bool {
+func ValidateSignatureValues(v byte, r, s *big.Int, homestead bool) bool {
 	if r.Cmp(common.Big1) < 0 || s.Cmp(common.Big1) < 0 {
 		return false
 	}
 	vint := uint32(v)
-	if r.Cmp(secp256k1.N) < 0 && s.Cmp(secp256k1.N) < 0 && (vint == 27 || vint == 28) {
+	// reject upper range of s values (ECDSA malleability)
+	// see discussion in secp256k1/libsecp256k1/include/secp256k1.h
+	if homestead && s.Cmp(secp256k1.HalfN) > 0 {
+		return false
+	}
+	// Frontier: allow s to be in full N range
+	if s.Cmp(secp256k1.N) >= 0 {
+		return false
+	}
+	if r.Cmp(secp256k1.N) < 0 && (vint == 27 || vint == 28) {
 		return true
 	} else {
 		return false