eth, les: add sanity checks for unbounded block fields (#19573)

This PR adds some hardening in the lower levels of the protocol stack, to bail early on invalid data. Primarily, attacks that this PR protects against are on the "annoyance"-level, which would otherwise write a couple of megabytes of data into the log output, which is a bit resource intensive.

core/types/block.go

@@ -19,6 +19,7 @@ package types
 
 import (
 	"encoding/binary"
+	"fmt"
 	"io"
 	"math/big"
 	"reflect"
@@ -110,6 +111,25 @@ func (h *Header) Size() common.StorageSize {
 	return headerSize + common.StorageSize(len(h.Extra)+(h.Difficulty.BitLen()+h.Number.BitLen())/8)
 }
 
+// SanityCheck checks a few basic things -- these checks are way beyond what
+// any 'sane' production values should hold, and can mainly be used to prevent
+// that the unbounded fields are stuffed with junk data to add processing
+// overhead
+func (h *Header) SanityCheck() error {
+	if h.Number != nil && !h.Number.IsUint64() {
+		return fmt.Errorf("too large block number: bitlen %d", h.Number.BitLen())
+	}
+	if h.Difficulty != nil {
+		if diffLen := h.Difficulty.BitLen(); diffLen > 80 {
+			return fmt.Errorf("too large block difficulty: bitlen %d", diffLen)
+		}
+	}
+	if eLen := len(h.Extra); eLen > 100*1024 {
+		return fmt.Errorf("too large block extradata: size %d", eLen)
+	}
+	return nil
+}
+
 func rlpHash(x interface{}) (h common.Hash) {
 	hw := sha3.NewLegacyKeccak256()
 	rlp.Encode(hw, x)
@@ -316,6 +336,12 @@ func (b *Block) Size() common.StorageSize {
 	return common.StorageSize(c)
 }
 
+// SanityCheck can be used to prevent that unbounded fields are
+// stuffed with junk data to add processing overhead
+func (b *Block) SanityCheck() error {
+	return b.header.SanityCheck()
+}
+
 type writeCounter common.StorageSize
 
 func (c *writeCounter) Write(b []byte) (int, error) {