#37646 [BC-Insight] No implementation of BLOB_SIDECAR_SUBNET_COUNT with no issue and no PR in the GitHub

Submitted on Dec 11th 2024 at 14:10:06 UTC by @Pig46940 for Attackathon | Ethereum Protocol

Report ID: #37646
Report Type: Blockchain/DLT
Report severity: Insight
Target: https://github.com/chainsafe/lodestar
Impacts:
- (Specifications) A bug in specifications with no direct impact on client implementations

Description

Brief/Intro

In the consensus specifications, BLOB_SIDECAR_SUBNET_COUNT should be implemented; however, it is not implemented in the Lodestar codebase.

https://github.com/ethereum/consensus-specs/blob/d8276acf06a05cf396951687119de55b725ca120/specs/deneb/p2p-interface.md_\\[New in Deneb:EIP4844]_

Name	Value	Description
`BLOB_SIDECAR_SUBNET_COUNT`	`6`	The number of blob sidecar subnets used in the gossipsub protocol.

Vulnerability Details

The coment left in the test code // TODO DENEB: Configure the blob subnets in a followup PR. BUT, I could not find the implementation in entire repository.

The BLOB_SIDECAR_SUBNET_COUNT defines the blob sidecar subnet count in the Gossipsub protocol. However, no implementation is found in the entire codebase.

I carefully checked the following code, which should contain the relevant logic, but found no implementation:
https://github.com/ChainSafe/lodestar/blob/dad9037e7739d5bcbccfe627e715ef40e9ba935b/packages/beacon-node/src/network/gossip/gossipsub.ts

The value is only defined in interopConfigs.ts with no implementation:
https://github.com/ChainSafe/lodestar/blob/dad9037e7739d5bcbccfe627e715ef40e9ba935b/packages/validator/test/unit/utils/interopConfigs.ts#L54

I could not understand why your project does not implement this specification logic though the GitHub:
https://github.com/search?q=repo%3AChainSafe%2Flodestar%20BLOB\\_SIDECAR\\_SUBNET\\_COUNT\\&type=code

Additionally, the following comment is left in the test code:
// TODO DENEB: Configure the blob subnets in a followup PR
However, I could not find the implementation in the entire repository.

Other clients

Other consensus clients have implemented this logic.

Prysm

https://github.com/prysmaticlabs/prysm/blob/008f157e17e625e44ec076c79aae3a91c0a3f977/beacon-chain/sync/subscriber.go#L146

Lighthouse

https://github.com/sigp/lighthouse/blob/c042dc14d74352512b7632e0ee6ec07f1aa26b3a/beacon\\_node/lighthouse\\_network/src/types/topics.rs#L56

Impact Details

It is difficult to clearly understand the full impact; however, the blob sidecar network will increase certain limits when interacting with other clients. This may lead to an increase in P2P network traffic to some extent, potentially exposing a vulnerability that attackers could exploit.

References

https://github.com/ethereum/consensus-specs/blob/d8276acf06a05cf396951687119de55b725ca120/specs/deneb/p2p-interface.md#configuration

Proof of Concept

Should be in like following code

https://github.com/ChainSafe/lodestar/blob/dad9037e7739d5bcbccfe627e715ef40e9ba935b/packages/beacon-node/src/network/gossip/gossipsub.ts#L6

     for (const [fork, peersByBeaconBlobSidecarSubnet] of peersByBeaconBlobSidecarSubnetByFork.map) {
        for (let subnet = 0; subnet < BLOB_SIDECAR_SUBNET_COUNT; subnet++) {
          metricsGossip.peersByBeaconBlobSidecarSubnet.set(
            {fork, subnet: attSubnetLabel(subnet)},
            peersByBeaconBlobSidecarSubnet[subnet] ?? 0
          );
        }
      }