From 35fcf9c52b806d2a7eba0da4f65c97975200a2b2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Felf=C3=B6ldi=20Zsolt?= <zsfelfoldi@gmail.com>
Date: Thu, 4 Apr 2024 16:30:27 +0200
Subject: [PATCH] beacon/types: enforce fork order based on known forks list
 (#29380)

Co-authored-by: Felix Lange <fjl@twurst.com>
---
 beacon/types/config.go | 36 +++++++++++++++++++++++++++---------
 1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/beacon/types/config.go b/beacon/types/config.go
index a52da5212e..7706e85f6c 100644
--- a/beacon/types/config.go
+++ b/beacon/types/config.go
@@ -19,7 +19,9 @@ package types
 import (
 	"crypto/sha256"
 	"fmt"
+	"math"
 	"os"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -27,6 +29,7 @@ import (
 	"github.com/ethereum/go-ethereum/beacon/merkle"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/log"
 	"gopkg.in/yaml.v3"
 )
 
@@ -34,6 +37,8 @@ import (
 // across signing different data structures.
 const syncCommitteeDomain = 7
 
+var knownForks = []string{"GENESIS", "ALTAIR", "BELLATRIX", "CAPELLA", "DENEB"}
+
 // Fork describes a single beacon chain fork and also stores the calculated
 // signature domain used after this fork.
 type Fork struct {
@@ -46,6 +51,9 @@ type Fork struct {
 	// Fork version, see https://github.com/ethereum/consensus-specs/blob/dev/specs/phase0/beacon-chain.md#custom-types
 	Version []byte
 
+	// index in list of known forks or MaxInt if unknown
+	knownIndex int
+
 	// calculated by computeDomain, based on fork version and genesis validators root
 	domain merkle.Value
 }
@@ -99,9 +107,14 @@ func (f Forks) SigningRoot(header Header) (common.Hash, error) {
 	return signingRoot, nil
 }
 
-func (f Forks) Len() int           { return len(f) }
-func (f Forks) Swap(i, j int)      { f[i], f[j] = f[j], f[i] }
-func (f Forks) Less(i, j int) bool { return f[i].Epoch < f[j].Epoch }
+func (f Forks) Len() int      { return len(f) }
+func (f Forks) Swap(i, j int) { f[i], f[j] = f[j], f[i] }
+func (f Forks) Less(i, j int) bool {
+	if f[i].Epoch != f[j].Epoch {
+		return f[i].Epoch < f[j].Epoch
+	}
+	return f[i].knownIndex < f[j].knownIndex
+}
 
 // ChainConfig contains the beacon chain configuration.
 type ChainConfig struct {
@@ -122,16 +135,22 @@ func (c *ChainConfig) ForkAtEpoch(epoch uint64) Fork {
 
 // AddFork adds a new item to the list of forks.
 func (c *ChainConfig) AddFork(name string, epoch uint64, version []byte) *ChainConfig {
+	knownIndex := slices.Index(knownForks, name)
+	if knownIndex == -1 {
+		knownIndex = math.MaxInt // assume that the unknown fork happens after the known ones
+		if epoch != math.MaxUint64 {
+			log.Warn("Unknown fork in config.yaml", "fork name", name, "known forks", knownForks)
+		}
+	}
 	fork := &Fork{
-		Name:    name,
-		Epoch:   epoch,
-		Version: version,
+		Name:       name,
+		Epoch:      epoch,
+		Version:    version,
+		knownIndex: knownIndex,
 	}
 	fork.computeDomain(c.GenesisValidatorsRoot)
-
 	c.Forks = append(c.Forks, fork)
 	sort.Sort(c.Forks)
-
 	return c
 }
 
@@ -181,6 +200,5 @@ func (c *ChainConfig) LoadForks(path string) error {
 	for name := range versions {
 		return fmt.Errorf("epoch number missing for fork %q in beacon chain config file", name)
 	}
-	sort.Sort(c.Forks)
 	return nil
 }