EIP4844: crypto stubs

beacon-chain/blockchain/process_block.go

@@ -715,3 +715,39 @@ func (s *Service) fillMissingBlockPayloadId(ctx context.Context) error {
 	})
 	return err
 }
+
+// validateBlobs validates the blobs with the kzg commitments in block.
+// Spec code:
+// def validate_blobs(expected_kzg_commitments: Sequence[KZGCommitment],
+//
+//	               blobs: Sequence[Blob],
+//	               proofs: Sequence[KZGProof]) -> None:
+//	assert len(expected_kzg_commitments) == len(blobs)
+//	assert len(blobs) == len(proofs)
+//
+//	assert verify_blob_kzg_proof_batch(blobs, expected_kzg_commitments, proofs)
+func (s *Service) validateBlobs(ctx context.Context, blk interfaces.ReadOnlyBeaconBlock) error {
+	if blk.Version() < version.Deneb {
+		return nil
+	}
+	comms, err := blk.Body().BlobKzgCommitments()
+	if err != nil {
+		return err
+	}
+	if len(comms) == 0 {
+		return nil
+	}
+	scs, err := s.cfg.BeaconDB.BlobSidecarsBySlot(ctx, blk.Slot()) // Also can use ByRoot here.
+	if err != nil {
+		return err
+	}
+	if len(scs.Sidecars) != len(comms) {
+		return fmt.Errorf("number of sidecars %d does not match number of commitments %d", len(scs.Sidecars), len(comms))
+	}
+	proofs := make([][]byte, len(comms))
+	for i, sc := range scs.Sidecars {
+		proofs[i] = sc.KzgProof
+	}
+	// TODO(Potuz):  assert verify_blob_kzg_proof_batch(blobs, expected_kzg_commitments, proofs)
+	return nil
+}

beacon-chain/rpc/prysm/v1alpha1/validator/proposer.go

@@ -154,7 +154,6 @@ func (vs *Server) GetBeaconBlock(ctx context.Context, req *ethpb.BlockRequest) (
 			return nil, status.Errorf(codes.Internal, "Could not get block root: %v", err)
 		}
 
-		// TODO: Better error handling. If something is wrong with the blob, we don't want to fail block production. Also should check if the kzg commitment matches.
 		validatorBlobs := make([]*ethpb.BlobSidecar, len(blk.Body.BlobKzgCommitments))
 		var gethBlobs types.Blobs
 		for _, b := range blobs {
@@ -162,6 +161,11 @@ func (vs *Server) GetBeaconBlock(ctx context.Context, req *ethpb.BlockRequest) (
 			copy(gethBlob[:], b.Data)
 			gethBlobs = append(gethBlobs, gethBlob)
 		}
+
+		// TODO(Potuz):
+		// - Currently using `ComputeCommitmentsAndProofs` from Geth. Is this ok?
+		// - Add a defensive check if block's kzg commitments align with blobs. If fails, we continue and skip blob.
+
 		commitments, _, proofs, err := gethBlobs.ComputeCommitmentsAndProofs()
 		if err != nil {
 			return nil, status.Errorf(codes.Internal, "Could not compute commitments and proofs: %v", err)