feat: move attestation committee at the end of attestation (#6883)

packages/beacon-node/src/chain/validation/attestation.ts

@@ -456,7 +456,7 @@ async function validateGossipAttestationNoSignatureCheck(
   let attDataRootHex: RootHex;
   const signature = attestationOrCache.attestation
     ? attestationOrCache.attestation.signature
-    : getSignatureFromAttestationSerialized(fork, attestationOrCache.serializedData);
+    : getSignatureFromAttestationSerialized(attestationOrCache.serializedData);
   if (signature === null) {
     throw new AttestationError(GossipAction.REJECT, {
       code: AttestationErrorCode.INVALID_SERIALIZED_BYTES,

packages/beacon-node/src/util/sszBytes.ts

@@ -26,8 +26,8 @@ export type AttDataCommitteeBitsBase64 = string;
 // class Attestation(Container):
 //   aggregation_bits: BitList[MAX_VALIDATORS_PER_COMMITTEE * MAX_COMMITTEES_PER_SLOT] - offset 4
 //   data: AttestationData - target data - 128
-//   committee_bits: BitVector[MAX_COMMITTEES_PER_SLOT]
 //   signature: BLSSignature - 96
+//   committee_bits: BitVector[MAX_COMMITTEES_PER_SLOT]
 //
 // for all forks
 // class AttestationData(Container): 128 bytes fixed size
@@ -82,14 +82,19 @@ export function getSeenAttDataKey(forkSeq: ForkSeq, data: Uint8Array): SeenAttDa
  * Return null if data is not long enough to extract attestation data.
  */
 export function getSeenAttDataKeyElectra(electraAttestationBytes: Uint8Array): AttDataCommitteeBitsBase64 | null {
-  const startIndex = VARIABLE_FIELD_OFFSET;
-  const seenKeyLength = ATTESTATION_DATA_SIZE + COMMITTEE_BITS_SIZE;
+  const attestationData = getSeenAttDataKeyPhase0(electraAttestationBytes);
 
-  if (electraAttestationBytes.length < startIndex + seenKeyLength) {
+  if (attestationData === null) {
     return null;
   }
 
-  return toBase64(electraAttestationBytes.subarray(startIndex, startIndex + seenKeyLength));
+  const committeeBits = getCommitteeBitsFromAttestationSerialized(electraAttestationBytes);
+
+  if (committeeBits === null) {
+    return null;
+  }
+
+  return attestationData + toBase64(committeeBits.uint8Array);
 }
 
 /**
@@ -112,7 +117,7 @@ export function getSeenAttDataKeyPhase0(data: Uint8Array): AttDataBase64 | null
 export function getAggregationBitsFromAttestationSerialized(fork: ForkName, data: Uint8Array): BitArray | null {
   const aggregationBitsStartIndex =
     ForkSeq[fork] >= ForkSeq.electra
-      ? VARIABLE_FIELD_OFFSET + ATTESTATION_DATA_SIZE + COMMITTEE_BITS_SIZE + SIGNATURE_SIZE
+      ? VARIABLE_FIELD_OFFSET + ATTESTATION_DATA_SIZE + SIGNATURE_SIZE + COMMITTEE_BITS_SIZE
       : VARIABLE_FIELD_OFFSET + ATTESTATION_DATA_SIZE + SIGNATURE_SIZE;
 
   if (data.length < aggregationBitsStartIndex) {
@@ -127,11 +132,8 @@ export function getAggregationBitsFromAttestationSerialized(fork: ForkName, data
  * Extract signature from attestation serialized bytes.
  * Return null if data is not long enough to extract signature.
  */
-export function getSignatureFromAttestationSerialized(fork: ForkName, data: Uint8Array): BLSSignature | null {
-  const signatureStartIndex =
-    ForkSeq[fork] >= ForkSeq.electra
-      ? VARIABLE_FIELD_OFFSET + ATTESTATION_DATA_SIZE + COMMITTEE_BITS_SIZE
-      : VARIABLE_FIELD_OFFSET + ATTESTATION_DATA_SIZE;
+export function getSignatureFromAttestationSerialized(data: Uint8Array): BLSSignature | null {
+  const signatureStartIndex = VARIABLE_FIELD_OFFSET + ATTESTATION_DATA_SIZE;
 
   if (data.length < signatureStartIndex + SIGNATURE_SIZE) {
     return null;
@@ -145,7 +147,7 @@ export function getSignatureFromAttestationSerialized(fork: ForkName, data: Uint
  * Return null if data is not long enough to extract committee bits.
  */
 export function getCommitteeBitsFromAttestationSerialized(data: Uint8Array): BitArray | null {
-  const committeeBitsStartIndex = VARIABLE_FIELD_OFFSET + ATTESTATION_DATA_SIZE;
+  const committeeBitsStartIndex = VARIABLE_FIELD_OFFSET + ATTESTATION_DATA_SIZE + SIGNATURE_SIZE;
 
   if (data.length < committeeBitsStartIndex + COMMITTEE_BITS_SIZE) {
     return null;

packages/beacon-node/test/unit/util/sszBytes.test.ts

@@ -54,12 +54,12 @@ describe("attestation SSZ serialized picking", () => {
           attestation.aggregationBits.toBoolArray()
         );
         expect(getCommitteeBitsFromAttestationSerialized(bytes)).toEqual(attestation.committeeBits);
-        expect(getSignatureFromAttestationSerialized(ForkName.electra, bytes)).toEqual(attestation.signature);
+        expect(getSignatureFromAttestationSerialized(bytes)).toEqual(attestation.signature);
       } else {
         expect(getAggregationBitsFromAttestationSerialized(ForkName.phase0, bytes)?.toBoolArray()).toEqual(
           attestation.aggregationBits.toBoolArray()
         );
-        expect(getSignatureFromAttestationSerialized(ForkName.phase0, bytes)).toEqual(attestation.signature);
+        expect(getSignatureFromAttestationSerialized(bytes)).toEqual(attestation.signature);
       }
 
       const attDataBase64 = ssz.phase0.AttestationData.serialize(attestation.data);
@@ -99,8 +99,8 @@ describe("attestation SSZ serialized picking", () => {
   it("getSignatureFromAttestationSerialized - invalid data", () => {
     const invalidSignatureDataSizes = [0, 4, 100, 128, 227];
     for (const size of invalidSignatureDataSizes) {
-      expect(getSignatureFromAttestationSerialized(ForkName.phase0, Buffer.alloc(size))).toBeNull();
-      expect(getSignatureFromAttestationSerialized(ForkName.electra, Buffer.alloc(size))).toBeNull();
+      expect(getSignatureFromAttestationSerialized(Buffer.alloc(size))).toBeNull();
+      expect(getSignatureFromAttestationSerialized(Buffer.alloc(size))).toBeNull();
     }
   });
 });

packages/types/src/electra/sszTypes.ts

@@ -62,8 +62,8 @@ export const Attestation = new ContainerType(
   {
     aggregationBits: AggregationBits, // Modified in ELECTRA
     data: phase0Ssz.AttestationData,
-    committeeBits: CommitteeBits, // New in ELECTRA
     signature: BLSSignature,
+    committeeBits: CommitteeBits, // New in ELECTRA
   },
   {typeName: "Attestation", jsonCase: "eth2"}
 );