core: add message root to signed data interface (#1349)

Add explicit unsigned data message root function to signed data as a better way to ensure consistent unsigned data in parsigdb. Relying on json serialisation to check for consistent signed data is brittle.

category: refactor
ticket: #1347

core/signeddata.go

@@ -63,6 +63,10 @@ func NewPartialSignature(sig Signature, shareIdx int) ParSignedData {
 // Signature is a BLS12-381 Signature. It implements SignedData.
 type Signature []byte
 
+func (Signature) MessageRoot() ([32]byte, error) {
+	return [32]byte{}, errors.New("unsigned data root not supported by signature type")
+}
+
 func (s Signature) Clone() (SignedData, error) {
 	return s.clone(), nil
 }
@@ -153,6 +157,20 @@ type VersionedSignedBeaconBlock struct {
 	spec.VersionedSignedBeaconBlock // Could subtype instead of embed, but aligning with Attestation that cannot subtype.
 }
 
+func (b VersionedSignedBeaconBlock) MessageRoot() ([32]byte, error) {
+	switch b.Version {
+	// No block nil checks since `NewVersionedSignedBeaconBlock` assumed.
+	case spec.DataVersionPhase0:
+		return b.Phase0.Message.HashTreeRoot()
+	case spec.DataVersionAltair:
+		return b.Altair.Message.HashTreeRoot()
+	case spec.DataVersionBellatrix:
+		return b.Bellatrix.Message.HashTreeRoot()
+	default:
+		panic("unknown version") // Note this is avoided by using `NewVersionedSignedBeaconBlock`.
+	}
+}
+
 func (b VersionedSignedBeaconBlock) Clone() (SignedData, error) {
 	return b.clone()
 }
@@ -270,11 +288,6 @@ func (b *VersionedSignedBeaconBlock) UnmarshalJSON(input []byte) error {
 	return nil
 }
 
-// VersionedSignedBlindedBeaconBlock is a signed versioned blinded beacon block and implements SignedData.
-type VersionedSignedBlindedBeaconBlock struct {
-	eth2api.VersionedSignedBlindedBeaconBlock // Could subtype instead of embed, but aligning with Attestation that cannot subtype.
-}
-
 // NewVersionedSignedBlindedBeaconBlock validates and returns a new wrapped VersionedSignedBlindedBeaconBlock.
 func NewVersionedSignedBlindedBeaconBlock(block *eth2api.VersionedSignedBlindedBeaconBlock) (VersionedSignedBlindedBeaconBlock, error) {
 	switch block.Version {
@@ -302,6 +315,21 @@ func NewPartialVersionedSignedBlindedBeaconBlock(block *eth2api.VersionedSignedB
 	}, nil
 }
 
+// VersionedSignedBlindedBeaconBlock is a signed versioned blinded beacon block and implements SignedData.
+type VersionedSignedBlindedBeaconBlock struct {
+	eth2api.VersionedSignedBlindedBeaconBlock // Could subtype instead of embed, but aligning with Attestation that cannot subtype.
+}
+
+func (b VersionedSignedBlindedBeaconBlock) MessageRoot() ([32]byte, error) {
+	switch b.Version {
+	// No block nil checks since `NewVersionedSignedBlindedBeaconBlock` assumed.
+	case spec.DataVersionBellatrix:
+		return b.Bellatrix.Message.HashTreeRoot()
+	default:
+		panic("unknown version") // Note this is avoided by using `NewVersionedSignedBlindedBeaconBlock`.
+	}
+}
+
 func (b VersionedSignedBlindedBeaconBlock) Clone() (SignedData, error) {
 	return b.clone()
 }
@@ -419,6 +447,10 @@ type Attestation struct {
 	eth2p0.Attestation
 }
 
+func (a Attestation) MessageRoot() ([32]byte, error) {
+	return a.Data.HashTreeRoot()
+}
+
 func (a Attestation) Clone() (SignedData, error) {
 	return a.clone()
 }
@@ -476,6 +508,10 @@ type SignedVoluntaryExit struct {
 	eth2p0.SignedVoluntaryExit
 }
 
+func (e SignedVoluntaryExit) MessageRoot() ([32]byte, error) {
+	return e.Message.HashTreeRoot()
+}
+
 func (e SignedVoluntaryExit) Clone() (SignedData, error) {
 	return e.clone()
 }
@@ -516,11 +552,6 @@ func (e *SignedVoluntaryExit) UnmarshalJSON(b []byte) error {
 	return e.SignedVoluntaryExit.UnmarshalJSON(b)
 }
 
-// VersionedSignedValidatorRegistration is a signed versioned validator (builder) registration and implements SignedData.
-type VersionedSignedValidatorRegistration struct {
-	eth2api.VersionedSignedValidatorRegistration
-}
-
 // versionedRawValidatorRegistrationJSON is a custom VersionedSignedValidator serialiser.
 type versionedRawValidatorRegistrationJSON struct {
 	Version      int             `json:"version"`
@@ -554,6 +585,20 @@ func NewPartialVersionedSignedValidatorRegistration(registration *eth2api.Versio
 	}, nil
 }
 
+// VersionedSignedValidatorRegistration is a signed versioned validator (builder) registration and implements SignedData.
+type VersionedSignedValidatorRegistration struct {
+	eth2api.VersionedSignedValidatorRegistration
+}
+
+func (r VersionedSignedValidatorRegistration) MessageRoot() ([32]byte, error) {
+	switch r.Version {
+	case spec.BuilderVersionV1:
+		return r.V1.Message.HashTreeRoot()
+	default:
+		panic("unknown version")
+	}
+}
+
 func (r VersionedSignedValidatorRegistration) Clone() (SignedData, error) {
 	return r.clone()
 }
@@ -660,6 +705,10 @@ type SignedRandao struct {
 	eth2util.SignedEpoch
 }
 
+func (s SignedRandao) MessageRoot() ([32]byte, error) {
+	return s.SignedEpoch.HashTreeRoot()
+}
+
 func (s SignedRandao) Signature() Signature {
 	return SigFromETH2(s.SignedEpoch.Signature)
 }
@@ -717,6 +766,10 @@ type BeaconCommitteeSelection struct {
 	eth2exp.BeaconCommitteeSelection
 }
 
+func (s BeaconCommitteeSelection) MessageRoot() ([32]byte, error) {
+	return eth2util.SlotHashRoot(s.Slot)
+}
+
 func (s BeaconCommitteeSelection) Signature() Signature {
 	return SigFromETH2(s.SelectionProof)
 }
@@ -772,6 +825,10 @@ type SignedAggregateAndProof struct {
 	eth2p0.SignedAggregateAndProof
 }
 
+func (s SignedAggregateAndProof) MessageRoot() ([32]byte, error) {
+	return s.Message.HashTreeRoot()
+}
+
 func (s SignedAggregateAndProof) Signature() Signature {
 	return SigFromETH2(s.SignedAggregateAndProof.Signature)
 }
@@ -827,6 +884,10 @@ type SignedSyncMessage struct {
 	altair.SyncCommitteeMessage
 }
 
+func (s SignedSyncMessage) MessageRoot() ([32]byte, error) {
+	return s.BeaconBlockRoot, nil
+}
+
 func (s SignedSyncMessage) Signature() Signature {
 	return SigFromETH2(s.SyncCommitteeMessage.Signature)
 }
@@ -869,6 +930,10 @@ type SignedSyncContributionAndProof struct {
 	altair.SignedContributionAndProof
 }
 
+func (s SignedSyncContributionAndProof) MessageRoot() ([32]byte, error) {
+	return s.Message.HashTreeRoot()
+}
+
 func (s SignedSyncContributionAndProof) Signature() Signature {
 	return SigFromETH2(s.SignedContributionAndProof.Signature)
 }

core/signeddata_test.go

@@ -102,6 +102,12 @@ func TestSignedDataSetSignature(t *testing.T) {
 			require.NoError(t, err)
 			require.NotEqual(t, clone.Signature(), test.data.Signature())
 			require.NotEmpty(t, clone.Signature())
+
+			msgRoot, err := test.data.MessageRoot()
+			require.NoError(t, err)
+			cloneRoot, err := test.data.MessageRoot()
+			require.NoError(t, err)
+			require.Equal(t, msgRoot, cloneRoot)
 		})
 	}
 }

core/types.go

@@ -371,6 +371,8 @@ type SignedData interface {
 	Signature() Signature
 	// SetSignature returns a copy of signed duty data with the signature replaced.
 	SetSignature(Signature) (SignedData, error)
+	// MessageRoot returns the unsigned data message root.
+	MessageRoot() ([32]byte, error)
 	// Clone returns a cloned copy of the SignedData. For an immutable core workflow architecture,
 	// remember to clone data when it leaves the current scope (sharing, storing, returning, etc).
 	Clone() (SignedData, error)