Incorrect safeBlockHash in fcU with payload attributes

[michaelsproul]

🐞 Bug Report

Description

While testing Prysm with my execution multiplexer (eleel) I noticed that some of Prysm's forkchoiceUpdated messages were not matching Lighthouse.

I tracked it down to Prysm sometimes setting the safeBlockHash to the finalizedBlockHash rather than the justifiedBlockHash. I noticed that this seems to happen only for fork choice updates that include payload attributes, which at a glance makes sense given the code here:

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

Lines 139 to 143 in f5bfb8e

	f := &enginev1.ForkchoiceState{
	HeadBlockHash: parentHash,
	SafeBlockHash: finalizedBlockHash,
	FinalizedBlockHash: finalizedBlockHash,
	}

This isn't a critical bug, and I think the impact is minimal. For now I'll work around it in eleel.

Has this worked before in a previous version?

Not sure. I noticed it on v3.2.2 and upgrading to v4.0.0 didn't fix it.

🌍 Your Environment

Operating System:

  
Ubuntu 22.04 x86_64
  

What version of Prysm are you running? (Which release)

  
v4.0.0
  

[potuz]

Oh nice catch thanks for the report @michaelsproul will move to unrealized justified checkpoint all of those