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

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.
This commit is contained in:
Martin Holst Swende 2019-07-08 11:42:22 +02:00 committed by Felix Lange
parent 5bc9ccfa0a
commit cdfe9a3a2a
6 changed files with 57 additions and 5 deletions

View File

@ -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) {

View File

@ -685,7 +685,7 @@ func (f *Fetcher) 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)
}
}
@ -696,7 +696,7 @@ func (f *Fetcher) 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)
@ -705,7 +705,7 @@ func (f *Fetcher) 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)
}
}
@ -714,7 +714,7 @@ func (f *Fetcher) 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)

View File

@ -697,6 +697,9 @@ 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

View File

@ -173,6 +173,19 @@ 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

View File

@ -442,7 +442,9 @@ 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
}
update, size := req.Update.decode()
if p.rejectUpdate(size) {
return errResp(ErrRequestRejected, "")

View File

@ -149,6 +149,14 @@ 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})