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eth/downloader: circumvent a fake blockchain attack

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This commit is contained in:
Péter Szilágyi
2015-05-15 14:48:57 +03:00
parent b517967f86
commit 5c1a7b965c
2 changed files with 58 additions and 27 deletions
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21
eth/downloader/downloader.go
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@ -90,7 +90,6 @@ func New(mux *event.TypeMux, hasBlock hashCheckFn, getBlock getBlockFn) *Downloa
mux: mux,
queue: newQueue(),
peers: newPeerSet(),
checks: make(map[common.Hash]time.Time),
hasBlock: hasBlock,
getBlock: getBlock,
newPeerCh: make(chan *peer, 1),
@ -160,6 +159,7 @@ func (d *Downloader) Synchronise(id string, hash common.Hash) error {
// Reset the queue and peer set to clean any internal leftover state
d.queue.Reset()
d.peers.Reset()
d.checks = make(map[common.Hash]time.Time)
// Retrieve the origin peer and initiate the downloading process
p := d.peers.Peer(id)
@ -184,7 +184,7 @@ func (d *Downloader) syncWithPeer(p *peer, hash common.Hash) (err error) {
defer func() {
// reset on error
if err != nil {
d.queue.Reset()
d.Cancel()
d.mux.Post(FailedEvent{err})
} else {
d.mux.Post(DoneEvent{})
@ -259,8 +259,6 @@ func (d *Downloader) fetchHashes(p *peer, h common.Hash) error {
// Make sure the peer actually gave something valid
if len(hashPack.hashes) == 0 {
glog.V(logger.Debug).Infof("Peer (%s) responded with empty hash set\n", active.id)
d.queue.Reset()
return errEmptyHashSet
}
// Determine if we're done fetching hashes (queue up all pending), and continue if not done
@ -277,8 +275,6 @@ func (d *Downloader) fetchHashes(p *peer, h common.Hash) error {
inserts := d.queue.Insert(hashPack.hashes)
if len(inserts) == 0 && !done {
glog.V(logger.Debug).Infof("Peer (%s) responded with stale hashes\n", active.id)
d.queue.Reset()
return ErrBadPeer
}
if !done {
@ -306,8 +302,13 @@ func (d *Downloader) fetchHashes(p *peer, h common.Hash) error {
if blockPack.peerId != active.id || len(blockPack.blocks) != 1 {
continue
}
hash := blockPack.blocks[0].Hash()
delete(d.checks, hash)
block := blockPack.blocks[0]
if _, ok := d.checks[block.Hash()]; ok {
if !d.queue.Has(block.ParentHash()) {
return ErrCrossCheckFailed
}
delete(d.checks, block.Hash())
}
case <-crossTicker.C:
// Iterate over all the cross checks and fail the hash chain if they're not verified
@ -334,7 +335,6 @@ func (d *Downloader) fetchHashes(p *peer, h common.Hash) error {
// if all peers have been tried, abort the process entirely or if the hash is
// the zero hash.
if p == nil || (head == common.Hash{}) {
d.queue.Reset()
return ErrTimeout
}
// set p to the active peer. this will invalidate any hashes that may be returned
@ -380,7 +380,6 @@ out:
if err := d.queue.Deliver(blockPack.peerId, blockPack.blocks); err != nil {
if err == ErrInvalidChain {
// The hash chain is invalid (blocks are not ordered properly), abort
d.queue.Reset()
return err
}
// Peer did deliver, but some blocks were off, penalize
@ -414,7 +413,6 @@ out:
}
// After removing bad peers make sure we actually have sufficient peer left to keep downloading
if d.peers.Len() == 0 {
d.queue.Reset()
return errNoPeers
}
// If there are unrequested hashes left start fetching
@ -448,7 +446,6 @@ out:
// Make sure that we have peers available for fetching. If all peers have been tried
// and all failed throw an error
if d.queue.InFlight() == 0 {
d.queue.Reset()
return errPeersUnavailable
}