refactor: Babbage block header VRF result decoding (#833)

Author: agaffney

ledger/babbage/babbage.go

@@ -140,6 +140,12 @@ func (b *BabbageBlock) Utxorpc() *utxorpc.Block {
 	return block
 }
 
+type BabbageBlockHeaderVrfResult struct {
+	cbor.StructAsArray
+	Output []byte
+	Proof  []byte
+}
+
 type BabbageBlockHeader struct {
 	cbor.StructAsArray
 	cbor.DecodeStoreCbor
@@ -151,7 +157,7 @@ type BabbageBlockHeader struct {
 		PrevHash      common.Blake2b256
 		IssuerVkey    common.IssuerVkey
 		VrfKey        []byte
-		VrfResult     interface{}
+		VrfResult     BabbageBlockHeaderVrfResult
 		BlockBodySize uint64
 		BlockBodyHash common.Blake2b256
 		OpCert        struct {

ledger/verify_block.go

@@ -75,18 +75,16 @@ func VerifyBlock(block BlockHexCbor) (error, bool, string, uint64, uint64) {
 		), false, "", 0, 0
 	}
 	vrfBytes := header.Body.VrfKey[:]
-	vrfResult := header.Body.VrfResult.([]interface{})
-	vrfProofBytes := vrfResult[1].([]byte)
-	vrfOutputBytes := vrfResult[0].([]byte)
+	vrfResult := header.Body.VrfResult
 	seed := MkInputVrf(int64(header.Body.Slot), epochNonceByte)
-	output, errVrf := VrfVerifyAndHash(vrfBytes, vrfProofBytes, seed)
+	output, errVrf := VrfVerifyAndHash(vrfBytes, vrfResult.Proof, seed)
 	if errVrf != nil {
 		return fmt.Errorf(
 			"VerifyBlock: vrf invalid, %v",
 			errVrf.Error(),
 		), false, "", 0, 0
 	}
-	isVrfValid := bytes.Equal(output, vrfOutputBytes)
+	isVrfValid := bytes.Equal(output, vrfResult.Output)
 
 	// check if block data valid
 	blockBodyHash := header.Body.BlockBodyHash