From 8a070e8f7d45eca745c29d4523cc2e05ff2f117f Mon Sep 17 00:00:00 2001
From: Martin Holst Swende <martin@swende.se>
Date: Fri, 7 May 2021 10:31:01 +0200
Subject: [PATCH] consensus/clique: add some missing checks (#22836)

---
 consensus/clique/clique.go | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/consensus/clique/clique.go b/consensus/clique/clique.go
index c62e180faa91..9954a023e574 100644
--- a/consensus/clique/clique.go
+++ b/consensus/clique/clique.go
@@ -20,6 +20,7 @@ package clique
 import (
 	"bytes"
 	"errors"
+	"fmt"
 	"io"
 	"math/big"
 	"math/rand"
@@ -293,6 +294,15 @@ func (c *Clique) verifyHeader(chain consensus.ChainHeaderReader, header *types.H
 			return errInvalidDifficulty
 		}
 	}
+	// Verify that the gas limit is <= 2^63-1
+	cap := uint64(0x7fffffffffffffff)
+	if header.GasLimit > cap {
+		return fmt.Errorf("invalid gasLimit: have %v, max %v", header.GasLimit, cap)
+	}
+	// Verify that the gasUsed is <= gasLimit
+	if header.GasUsed > header.GasLimit {
+		return fmt.Errorf("invalid gasUsed: have %d, gasLimit %d", header.GasUsed, header.GasLimit)
+	}
 	// If all checks passed, validate any special fields for hard forks
 	if err := misc.VerifyForkHashes(chain.Config(), header, false); err != nil {
 		return err
@@ -324,6 +334,15 @@ func (c *Clique) verifyCascadingFields(chain consensus.ChainHeaderReader, header
 	if parent.Time+c.config.Period > header.Time {
 		return errInvalidTimestamp
 	}
+	// Verify that the gas limit remains within allowed bounds
+	diff := int64(parent.GasLimit) - int64(header.GasLimit)
+	if diff < 0 {
+		diff *= -1
+	}
+	limit := parent.GasLimit / params.GasLimitBoundDivisor
+	if uint64(diff) >= limit || header.GasLimit < params.MinGasLimit {
+		return fmt.Errorf("invalid gas limit: have %d, want %d += %d", header.GasLimit, parent.GasLimit, limit)
+	}
 	// Retrieve the snapshot needed to verify this header and cache it
 	snap, err := c.snapshot(chain, number-1, header.ParentHash, parents)
 	if err != nil {