feat: implement PayloadProof function (#14356)

* feat: implement function `PayloadProof` to calculate proof of execution payload

* remove comments

* feat: implement function to compute field roots of

* feat: implement function to compute `BeaconBlock` field roots and add tests

* fix dependencies

* check if interface implements the assserted type

* fix: lint

* replace `ok != true` with `!ok`

* remove unused parameter from `PayloadProof`

* remove test and move `PayloadProof` to `blocks/proofs.go`

* remove `PayloadProof` from `fieldtrie`

* replace `fieldtrie.ProofFromMerkleLayers` with `trie.ProofFromMerkleLayers`

* Update container/trie/sparse_merkle.go

* update dependencies

---------

Co-authored-by: Radosław Kapka <rkapka@wp.pl>
Co-authored-by: Radosław Kapka <radoslaw.kapka@gmail.com>

consensus-types/blocks/BUILD.bazel

@@ -18,6 +18,7 @@ go_library(
     importpath = "github.com/prysmaticlabs/prysm/v5/consensus-types/blocks",
     visibility = ["//visibility:public"],
     deps = [
+        "//beacon-chain/state/stateutil:go_default_library",
         "//config/fieldparams:go_default_library",
         "//config/params:go_default_library",
         "//consensus-types:go_default_library",

consensus-types/blocks/proofs.go

@@ -3,15 +3,23 @@ package blocks
 import (
 	"context"
 	"encoding/binary"
+	"errors"
 	"fmt"
 
+	"github.com/prysmaticlabs/prysm/v5/beacon-chain/state/stateutil"
 	"github.com/prysmaticlabs/prysm/v5/config/params"
+	"github.com/prysmaticlabs/prysm/v5/container/trie"
 	"github.com/prysmaticlabs/prysm/v5/crypto/hash/htr"
 	"github.com/prysmaticlabs/prysm/v5/encoding/ssz"
 	"github.com/prysmaticlabs/prysm/v5/runtime/version"
 	"go.opencensus.io/trace"
 )
 
+const (
+	payloadFieldIndex = 9
+	bodyFieldIndex    = 4
+)
+
 func ComputeBlockBodyFieldRoots(ctx context.Context, blockBody *BeaconBlockBody) ([][]byte, error) {
 	_, span := trace.StartSpan(ctx, "blocks.ComputeBlockBodyFieldRoots")
 	defer span.End()
@@ -172,3 +180,68 @@ func ComputeBlockBodyFieldRoots(ctx context.Context, blockBody *BeaconBlockBody)
 
 	return fieldRoots, nil
 }
+
+func ComputeBlockFieldRoots(ctx context.Context, block *BeaconBlock) ([][]byte, error) {
+	_, span := trace.StartSpan(ctx, "blocks.ComputeBlockFieldRoots")
+	defer span.End()
+
+	if block == nil {
+		return nil, errNilBlock
+	}
+
+	fieldRoots := make([][]byte, 5)
+	for i := range fieldRoots {
+		fieldRoots[i] = make([]byte, 32)
+	}
+
+	// Slot
+	slotRoot := ssz.Uint64Root(uint64(block.slot))
+	copy(fieldRoots[0], slotRoot[:])
+
+	// Proposer Index
+	proposerRoot := ssz.Uint64Root(uint64(block.proposerIndex))
+	copy(fieldRoots[1], proposerRoot[:])
+
+	// Parent Root
+	copy(fieldRoots[2], block.parentRoot[:])
+
+	// State Root
+	copy(fieldRoots[3], block.stateRoot[:])
+
+	// block body Root
+	blockBodyRoot, err := block.body.HashTreeRoot()
+	if err != nil {
+		return nil, err
+	}
+	copy(fieldRoots[4], blockBodyRoot[:])
+
+	return fieldRoots, nil
+}
+
+func PayloadProof(ctx context.Context, block *BeaconBlock) ([][]byte, error) {
+	i := block.Body()
+	blockBody, ok := i.(*BeaconBlockBody)
+	if !ok {
+		return nil, errors.New("failed to cast block body")
+	}
+
+	blockBodyFieldRoots, err := ComputeBlockBodyFieldRoots(ctx, blockBody)
+	if err != nil {
+		return nil, err
+	}
+
+	blockBodyFieldRootsTrie := stateutil.Merkleize(blockBodyFieldRoots)
+	blockBodyProof := trie.ProofFromMerkleLayers(blockBodyFieldRootsTrie, payloadFieldIndex)
+
+	beaconBlockFieldRoots, err := ComputeBlockFieldRoots(ctx, block)
+	if err != nil {
+		return nil, err
+	}
+
+	beaconBlockFieldRootsTrie := stateutil.Merkleize(beaconBlockFieldRoots)
+	beaconBlockProof := trie.ProofFromMerkleLayers(beaconBlockFieldRootsTrie, bodyFieldIndex)
+
+	finalProof := append(blockBodyProof, beaconBlockProof...)
+
+	return finalProof, nil
+}