Update zero hash to sha256().digest() (#2932)

* update zero hash

* change zero hash to conform with spec

* goimports

* add test for zero hash

beacon-chain/core/blocks/BUILD.bazel

@@ -56,5 +56,6 @@ go_test(
         "@com_github_prysmaticlabs_go_bitfield//:go_default_library",
         "@com_github_prysmaticlabs_go_ssz//:go_default_library",
         "@com_github_sirupsen_logrus//:go_default_library",
+        "@in_gopkg_d4l3k_messagediff_v1//:go_default_library",
     ],
 )

beacon-chain/core/blocks/block_operations_test.go

@@ -25,6 +25,7 @@ import (
 	"github.com/prysmaticlabs/prysm/shared/testutil"
 	"github.com/prysmaticlabs/prysm/shared/trieutil"
 	"github.com/sirupsen/logrus"
+	"gopkg.in/d4l3k/messagediff.v1"
 )
 
 func init() {
@@ -308,18 +309,19 @@ func TestProcessBlockHeader_OK(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Failed to process block header got: %v", err)
 	}
-	var zeroHash [32]byte
 	var zeroSig [96]byte
 	nsh := newState.LatestBlockHeader
 	expected := &pb.BeaconBlockHeader{
 		Slot:       block.Slot,
 		ParentRoot: latestBlockSignedRoot[:],
 		BodyRoot:   bodyRoot[:],
-		StateRoot:  zeroHash[:],
+		StateRoot:  params.BeaconConfig().ZeroHash[:],
 		Signature:  zeroSig[:],
 	}
 	if !proto.Equal(nsh, expected) {
-		t.Errorf("Expected %v, received %vk9k", expected, nsh)
+		diff, _ := messagediff.PrettyDiff(nsh, expected)
+		t.Log(diff)
+		t.Error("Mismatched state")
 	}
 }
 
@@ -342,7 +344,7 @@ func TestProcessRandao_IncorrectProposerFailsVerification(t *testing.T) {
 	domain := helpers.Domain(beaconState, epoch, params.BeaconConfig().DomainRandao)
 
 	// We make the previous validator's index sign the message instead of the proposer.
-	epochSignature := privKeys[proposerIdx-1].Sign(buf, domain)
+	epochSignature := privKeys[proposerIdx+1].Sign(buf, domain)
 	block := &pb.BeaconBlock{
 		Body: &pb.BeaconBlockBody{
 			RandaoReveal: epochSignature.Marshal(),

beacon-chain/core/state/state_test.go

@@ -34,10 +34,6 @@ func TestGenesisBeaconState_OK(t *testing.T) {
 	}
 	genesisForkVersion := params.BeaconConfig().GenesisForkVersion
 
-	if params.BeaconConfig().ZeroHash != [32]byte{} {
-		t.Error("ZeroHash should be all 0s for these tests to pass")
-	}
-
 	if params.BeaconConfig().EpochsPerHistoricalVector != 65536 {
 		t.Error("EpochsPerHistoricalVector should be 8192 for these tests to pass")
 	}

shared/params/config.go

@@ -35,7 +35,7 @@ type BeaconChainConfig struct {
 
 	// Initial value constants.
 	BLSWithdrawalPrefixByte byte     `yaml:"BLS_WITHDRAWAL_PREFIX_BYTE"` // BLSWithdrawalPrefixByte is used for BLS withdrawal and it's the first byte.
-	ZeroHash                [32]byte // ZeroHash is used to represent a zeroed out 32 byte array.
+	ZeroHash                [32]byte // ZeroHash is an alias for sha256().digest().
 
 	// Time parameters constants.
 	MinAttestationInclusionDelay     uint64 `yaml:"MIN_ATTESTATION_INCLUSION_DELAY"`     // MinAttestationInclusionDelay defines how long validator has to wait to include attestation for beacon block.
@@ -134,7 +134,7 @@ var defaultBeaconConfig = &BeaconChainConfig{
 
 	// Initial value constants.
 	BLSWithdrawalPrefixByte: byte(0),
-	ZeroHash:                [32]byte{},
+	ZeroHash:                [32]byte{0xe3, 0xb0, 0xc4, 0x42, 0x98, 0xfc, 0x1c, 0x14, 0x9a, 0xfb, 0xf4, 0xc8, 0x99, 0x6f, 0xb9, 0x24, 0x27, 0xae, 0x41, 0xe4, 0x64, 0x9b, 0x93, 0x4c, 0xa4, 0x95, 0x99, 0x1b, 0x78, 0x52, 0xb8, 0x55},
 
 	// Time parameter constants.
 	MinAttestationInclusionDelay:     1,

shared/params/config_test.go

@@ -1,6 +1,8 @@
 package params
 
 import (
+	"bytes"
+	"crypto/sha256"
 	"testing"
 )
 
@@ -12,3 +14,10 @@ func TestOverrideBeaconConfig(t *testing.T) {
 		t.Errorf("Shardcount in BeaconConfig incorrect. Wanted %d, got %d", 5, c.ShardCount)
 	}
 }
+
+func TestMainnetConfig_ZeroHashIsAliasOfSha256(t *testing.T) {
+	h := sha256.New()
+	if !bytes.Equal(BeaconConfig().ZeroHash[:], h.Sum(nil)) {
+		t.Error("Zero hash is not sha256.New().Sum()")
+	}
+}