chore(blobs): Validate Index field in BlobSidecar during processing

da/blob/types.go

@@ -49,6 +49,7 @@ type ConsensusSidecars interface {
 }
 
 type Sidecar interface {
+	GetIndex() uint64
 	GetBlob() eip4844.Blob
 	GetKzgProof() eip4844.KZGProof
 	GetKzgCommitment() eip4844.KZGCommitment

da/blob/verifier.go

@@ -78,6 +78,11 @@ func (bv *verifier) verifySidecars(
 	// Verifying that sidecars block headers match with header of the
 	// corresponding block concurrently.
 	for i, s := range sidecars.GetSidecars() {
+		// This check happens outside the goroutines so that we do not
+		// process the inclusion proofs before validating the index.
+		if s.GetIndex() >= bv.chainSpec.MaxBlobsPerBlock() {
+			return fmt.Errorf("invalid sidecar Index: %d", i)
+		}
 		g.Go(func() error {
 			var sigHeader = s.GetSignedBeaconBlockHeader()
 

da/types/sidecar.go

@@ -84,6 +84,10 @@ func (b *BlobSidecar) HasValidInclusionProof(
 	)
 }
 
+func (b *BlobSidecar) GetIndex() uint64 {
+	return b.Index
+}
+
 func (b *BlobSidecar) GetBlob() eip4844.Blob {
 	return b.Blob
 }