eth,les: add hash-lookup that is easier on memory

core/blockchain.go

@@ -1523,6 +1523,12 @@ func (bc *BlockChain) GetBlockHashesFromHash(hash common.Hash, max uint64) []com
 	return bc.hc.GetBlockHashesFromHash(hash, max)
 }
 
+// GetAncestorBlockHashFromHash retrieves the block hash for the ancestor of a given
+// hash, fetching towards the genesis block.
+func (bc *BlockChain) GetAncestorBlockHashFromHash(hash common.Hash, max uint64) common.Hash {
+	return bc.hc.GetAncestorBlockHashFromHash(hash, max)
+}
+
 // GetHeaderByNumber retrieves a block header from the database by number,
 // caching it (associated with its hash) if found.
 func (bc *BlockChain) GetHeaderByNumber(number uint64) *types.Header {

core/headerchain.go

@@ -307,6 +307,27 @@ func (hc *HeaderChain) GetBlockHashesFromHash(hash common.Hash, max uint64) []co
 	return chain
 }
 
+// GetAncestorBlockHashFromHash retrieves the block hash for the ancestor of a given
+// hash, fetching towards the genesis block.
+func (hc *HeaderChain) GetAncestorBlockHashFromHash(hash common.Hash, max uint64) common.Hash {
+	// Get the origin header from which to fetch
+	header := hc.GetHeaderByHash(hash)
+	if header == nil {
+		return common.Hash{}
+	}
+	// Iterate the headers until enough is collected or the genesis reached
+	next := common.Hash{}
+	for i := uint64(0); i < max; i++ {
+		next = header.ParentHash
+		if header = hc.GetHeader(next, header.Number.Uint64()-1); header == nil {
+			return common.Hash{}
+		}
+		if header.Number.Sign() == 0 {
+			return common.Hash{}
+		}
+	}
+	return next
+}
 // GetTd retrieves a block's total difficulty in the canonical chain from the
 // database by hash and number, caching it if found.
 func (hc *HeaderChain) GetTd(hash common.Hash, number uint64) *big.Int {

eth/handler.go

@@ -387,7 +387,7 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 					unknown = true
 				} else {
 					if header := pm.blockchain.GetHeaderByNumber(next); header != nil {
-						if pm.blockchain.GetBlockHashesFromHash(header.Hash(), query.Skip+1)[query.Skip] == query.Origin.Hash {
+						if pm.blockchain.GetAncestorBlockHashFromHash(header.Hash(), query.Skip+1) == query.Origin.Hash {
 							query.Origin.Hash = header.Hash()
 						} else {
 							unknown = true

les/handler.go

@@ -84,6 +84,7 @@ type BlockChain interface {
 	Rollback(chain []common.Hash)
 	GetHeaderByNumber(number uint64) *types.Header
 	GetBlockHashesFromHash(hash common.Hash, max uint64) []common.Hash
+	GetAncestorBlockHashFromHash(hash common.Hash, max uint64) common.Hash
 	Genesis() *types.Block
 	SubscribeChainHeadEvent(ch chan<- core.ChainHeadEvent) event.Subscription
 }
@@ -465,7 +466,7 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 					unknown = true
 				} else {
 					if header := pm.blockchain.GetHeaderByNumber(next); header != nil {
-						if pm.blockchain.GetBlockHashesFromHash(header.Hash(), query.Skip+1)[query.Skip] == query.Origin.Hash {
+						if pm.blockchain.GetAncestorBlockHashFromHash(header.Hash(), query.Skip+1) == query.Origin.Hash {
 							query.Origin.Hash = header.Hash()
 						} else {
 							unknown = true

les/handler_test.go

@@ -75,6 +75,11 @@ func testGetBlockHeaders(t *testing.T, protocol int) {
 			&getBlockHeadersData{Origin: hashOrNumber{Number: limit / 2}, Amount: 1},
 			[]common.Hash{bc.GetBlockByNumber(limit / 2).Hash()},
 		},
+		// Overflow attack
+		{
+			&getBlockHeadersData{Origin: hashOrNumber{Hash:bc.GetBlockByNumber(1).Hash()}, Amount: 1,Skip:0xFFFFFFFFFFFFFFFF},
+				[]common.Hash{},
+		},
 		// Multiple headers should be retrievable in both directions
 		{
 			&getBlockHeadersData{Origin: hashOrNumber{Number: limit / 2}, Amount: 3},

light/lightchain.go

@@ -433,6 +433,12 @@ func (self *LightChain) GetBlockHashesFromHash(hash common.Hash, max uint64) []c
 	return self.hc.GetBlockHashesFromHash(hash, max)
 }
 
+// GetAncestorBlockHashFromHash retrieves the block hash for the ancestor of a given
+// hash, fetching towards the genesis block.
+func (self *LightChain) GetAncestorBlockHashFromHash(hash common.Hash, max uint64) common.Hash{
+	return self.hc.GetAncestorBlockHashFromHash(hash, max)
+}
+
 // GetHeaderByNumber retrieves a block header from the database by number,
 // caching it (associated with its hash) if found.
 func (self *LightChain) GetHeaderByNumber(number uint64) *types.Header {