From a2892b1ed560dde4c733a25f6d0cad4f45259160 Mon Sep 17 00:00:00 2001
From: Nishant Das <nishdas93@gmail.com>
Date: Wed, 24 Jan 2024 13:48:15 +0800
Subject: [PATCH] clean up validate beacon block (#13517)

---
 beacon-chain/sync/validate_beacon_blocks.go | 63 ++++++++++++---------
 1 file changed, 37 insertions(+), 26 deletions(-)

diff --git a/beacon-chain/sync/validate_beacon_blocks.go b/beacon-chain/sync/validate_beacon_blocks.go
index 107cb9dc2..a82b787fc 100644
--- a/beacon-chain/sync/validate_beacon_blocks.go
+++ b/beacon-chain/sync/validate_beacon_blocks.go
@@ -241,36 +241,11 @@ func (s *Service) validateBeaconBlock(ctx context.Context, blk interfaces.ReadOn
 		return err
 	}
 
-	if !s.cfg.chain.InForkchoice(blk.Block().ParentRoot()) {
-		s.setBadBlock(ctx, blockRoot)
-		return blockchain.ErrNotDescendantOfFinalized
-	}
-
-	parentState, err := s.cfg.stateGen.StateByRoot(ctx, blk.Block().ParentRoot())
+	parentState, err := s.validatePhase0Block(ctx, blk, blockRoot)
 	if err != nil {
 		return err
 	}
 
-	if err := blocks.VerifyBlockSignatureUsingCurrentFork(parentState, blk); err != nil {
-		s.setBadBlock(ctx, blockRoot)
-		return err
-	}
-	// In the event the block is more than an epoch ahead from its
-	// parent state, we have to advance the state forward.
-	parentRoot := blk.Block().ParentRoot()
-	parentState, err = transition.ProcessSlotsUsingNextSlotCache(ctx, parentState, parentRoot[:], blk.Block().Slot())
-	if err != nil {
-		return err
-	}
-	idx, err := helpers.BeaconProposerIndex(ctx, parentState)
-	if err != nil {
-		return err
-	}
-	if blk.Block().ProposerIndex() != idx {
-		s.setBadBlock(ctx, blockRoot)
-		return errors.New("incorrect proposer index")
-	}
-
 	if err = s.validateBellatrixBeaconBlock(ctx, parentState, blk.Block()); err != nil {
 		if errors.Is(err, ErrOptimisticParent) {
 			return err
@@ -282,6 +257,42 @@ func (s *Service) validateBeaconBlock(ctx context.Context, blk interfaces.ReadOn
 	return nil
 }
 
+// Validates beacon block according to phase 0 validity conditions.
+// - Checks that the parent is in our forkchoice tree.
+// - Validates that the proposer signature is valid.
+// - Validates that the proposer index is valid.
+func (s *Service) validatePhase0Block(ctx context.Context, blk interfaces.ReadOnlySignedBeaconBlock, blockRoot [32]byte) (state.BeaconState, error) {
+	if !s.cfg.chain.InForkchoice(blk.Block().ParentRoot()) {
+		s.setBadBlock(ctx, blockRoot)
+		return nil, blockchain.ErrNotDescendantOfFinalized
+	}
+
+	parentState, err := s.cfg.stateGen.StateByRoot(ctx, blk.Block().ParentRoot())
+	if err != nil {
+		return nil, err
+	}
+
+	if err := blocks.VerifyBlockSignatureUsingCurrentFork(parentState, blk); err != nil {
+		return nil, err
+	}
+	// In the event the block is more than an epoch ahead from its
+	// parent state, we have to advance the state forward.
+	parentRoot := blk.Block().ParentRoot()
+	parentState, err = transition.ProcessSlotsUsingNextSlotCache(ctx, parentState, parentRoot[:], blk.Block().Slot())
+	if err != nil {
+		return nil, err
+	}
+	idx, err := helpers.BeaconProposerIndex(ctx, parentState)
+	if err != nil {
+		return nil, err
+	}
+	if blk.Block().ProposerIndex() != idx {
+		s.setBadBlock(ctx, blockRoot)
+		return nil, errors.New("incorrect proposer index")
+	}
+	return parentState, nil
+}
+
 func validateDenebBeaconBlock(blk interfaces.ReadOnlyBeaconBlock) error {
 	if blk.Version() < version.Deneb {
 		return nil