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

@@ -154,6 +154,25 @@ func (h *Header) Size() common.StorageSize {
 	return common.StorageSize(unsafe.Sizeof(*h)) + common.StorageSize(len(h.Extra)+(h.Difficulty.BitLen()+h.Number.BitLen()+h.Time.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
+}
+
 // Body is a simple (mutable, non-safe) data container for storing and moving
 // a block's data contents (transactions and uncles) together.
 type Body struct {
@@ -369,6 +388,12 @@ 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) {

eth/fetcher/block_fetcher.go

@@ -804,7 +804,7 @@ func (f *BlockFetcher) forgetHash(hash common.Hash) {
 	// Remove all pending announces and decrement DOS counters
 	for _, announce := range f.announced[hash] {
 		f.announces[announce.origin]--
-		if f.announces[announce.origin] == 0 {
+		if f.announces[announce.origin] <= 0 {
 			delete(f.announces, announce.origin)
 		}
 	}
@@ -815,7 +815,7 @@ func (f *BlockFetcher) forgetHash(hash common.Hash) {
 	// Remove any pending fetches and decrement the DOS counters
 	if announce := f.fetching[hash]; announce != nil {
 		f.announces[announce.origin]--
-		if f.announces[announce.origin] == 0 {
+		if f.announces[announce.origin] <= 0 {
 			delete(f.announces, announce.origin)
 		}
 		delete(f.fetching, hash)
@@ -824,7 +824,7 @@ func (f *BlockFetcher) forgetHash(hash common.Hash) {
 	// Remove any pending completion requests and decrement the DOS counters
 	for _, announce := range f.fetched[hash] {
 		f.announces[announce.origin]--
-		if f.announces[announce.origin] == 0 {
+		if f.announces[announce.origin] <= 0 {
 			delete(f.announces, announce.origin)
 		}
 	}
@@ -833,7 +833,7 @@ func (f *BlockFetcher) forgetHash(hash common.Hash) {
 	// Remove any pending completions and decrement the DOS counters
 	if announce := f.completing[hash]; announce != nil {
 		f.announces[announce.origin]--
-		if f.announces[announce.origin] == 0 {
+		if f.announces[announce.origin] <= 0 {
 			delete(f.announces, announce.origin)
 		}
 		delete(f.completing, hash)

eth/handler.go

@@ -810,6 +810,9 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 		if err := msg.Decode(&request); err != nil {
 			return errResp(ErrDecode, "%v: %v", msg, err)
 		}
+		if err := request.sanityCheck(); err != nil {
+			return err
+		}
 		request.Block.ReceivedAt = msg.ReceivedAt
 		request.Block.ReceivedFrom = p
 

eth/protocol.go

@@ -233,6 +233,19 @@ type newBlockData struct {
 	TD    *big.Int
 }
 
+// sanityCheck verifies that the values are reasonable, as a DoS protection
+func (request *newBlockData) sanityCheck() error {
+	if err := request.Block.SanityCheck(); err != nil {
+		return err
+	}
+	//TD at mainnet block #7753254 is 76 bits. If it becomes 100 million times
+	// larger, it will still fit within 100 bits
+	if tdlen := request.TD.BitLen(); tdlen > 100 {
+		return fmt.Errorf("too large block TD: bitlen %d", tdlen)
+	}
+	return nil
+}
+
 // blockBody represents the data content of a single block.
 type blockBody struct {
 	Transactions []*types.Transaction // Transactions contained within a block

les/handler.go

@@ -385,7 +385,9 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 		if err := msg.Decode(&req); err != nil {
 			return errResp(ErrDecode, "%v: %v", msg, err)
 		}
-
+		if err := req.sanityCheck(); err != nil {
+			return err
+		}
 		if p.requestAnnounceType == announceTypeSigned {
 			if err := req.checkSignature(p.ID()); err != nil {
 				p.Log().Trace("Invalid announcement signature", "err", err)

les/protocol.go

@@ -137,6 +137,14 @@ type announceData struct {
 	Update     keyValueList
 }
 
+// sanityCheck verifies that the values are reasonable, as a DoS protection
+func (a *announceData) sanityCheck() error {
+	if tdlen := a.Td.BitLen(); tdlen > 100 {
+		return fmt.Errorf("too large block TD: bitlen %d", tdlen)
+	}
+	return nil
+}
+
 // sign adds a signature to the block announcement by the given privKey
 func (a *announceData) sign(privKey *ecdsa.PrivateKey) {
 	rlp, _ := rlp.EncodeToBytes(announceBlock{a.Hash, a.Number, a.Td})