accounts, core, crypto, internal: use normalised V during signature handling (#3455)

To address increasing complexity in code that handles signatures, this PR
discards all notion of "different" signature types at the library level. Both
the crypto and accounts package is reduced to only be able to produce plain
canonical secp256k1 signatures. This makes the crpyto APIs much cleaner,
simpler and harder to abuse.

1 files changed, 4 insertions, 10 deletions

diff --git a/core/vm/contracts.go b/core/vm/contracts.go
index b45f14724..5cd0d0bb1 100644
--- a/core/vm/contracts.go
+++ b/core/vm/contracts.go
@@ -89,21 +89,15 @@ func ecrecoverFunc(in []byte) []byte {
 
 	r := common.BytesToBig(in[64:96])
 	s := common.BytesToBig(in[96:128])
-	// Treat V as a 256bit integer
-	vbig := common.Bytes2Big(in[32:64])
-	v := byte(vbig.Uint64())
+	v := in[63] - 27
 
 	// tighter sig s values in homestead only apply to tx sigs
-	if !crypto.ValidateSignatureValues(v, r, s, false) {
+	if common.Bytes2Big(in[32:63]).BitLen() > 0 || !crypto.ValidateSignatureValues(v, r, s, false) {
 		glog.V(logger.Detail).Infof("ECRECOVER error: v, r or s value invalid")
 		return nil
 	}
-
-	// v needs to be at the end and normalized for libsecp256k1
-	vbignormal := new(big.Int).Sub(vbig, big.NewInt(27))
-	vnormal := byte(vbignormal.Uint64())
-	rsv := append(in[64:128], vnormal)
-	pubKey, err := crypto.Ecrecover(in[:32], rsv)
+	// v needs to be at the end for libsecp256k1
+	pubKey, err := crypto.Ecrecover(in[:32], append(in[64:128], v))
 	// make sure the public key is a valid one
 	if err != nil {
 		glog.V(logger.Detail).Infoln("ECRECOVER error: ", err)