les, light: remove untrusted header retrieval in ODR (#21907)

* les, light: remove untrusted header retrieval in ODR

* les: polish

* light: check the hash equality in odr

les/client_handler.go

@@ -17,6 +17,7 @@
 package les
 
 import (
+	"context"
 	"math/big"
 	"sync"
 	"sync/atomic"
@@ -200,14 +201,23 @@ func (h *clientHandler) handleMsg(p *serverPeer) error {
 		p.fcServer.ReceivedReply(resp.ReqID, resp.BV)
 		p.answeredRequest(resp.ReqID)
 
-		// Filter out any explicitly requested headers, deliver the rest to the downloader
-		filter := len(headers) == 1
-		if filter {
-			headers = h.fetcher.deliverHeaders(p, resp.ReqID, resp.Headers)
-		}
-		if len(headers) != 0 || !filter {
-			if err := h.downloader.DeliverHeaders(p.id, headers); err != nil {
-				log.Debug("Failed to deliver headers", "err", err)
+		// Filter out the explicitly requested header by the retriever
+		if h.backend.retriever.requested(resp.ReqID) {
+			deliverMsg = &Msg{
+				MsgType: MsgBlockHeaders,
+				ReqID:   resp.ReqID,
+				Obj:     resp.Headers,
+			}
+		} else {
+			// Filter out any explicitly requested headers, deliver the rest to the downloader
+			filter := len(headers) == 1
+			if filter {
+				headers = h.fetcher.deliverHeaders(p, resp.ReqID, resp.Headers)
+			}
+			if len(headers) != 0 || !filter {
+				if err := h.downloader.DeliverHeaders(p.id, headers); err != nil {
+					log.Debug("Failed to deliver headers", "err", err)
+				}
 			}
 		}
 	case BlockBodiesMsg:
@@ -394,6 +404,42 @@ func (pc *peerConnection) RequestHeadersByNumber(origin uint64, amount int, skip
 	return nil
 }
 
+// RetrieveSingleHeaderByNumber requests a single header by the specified block
+// number. This function will wait the response until it's timeout or delivered.
+func (pc *peerConnection) RetrieveSingleHeaderByNumber(context context.Context, number uint64) (*types.Header, error) {
+	reqID := genReqID()
+	rq := &distReq{
+		getCost: func(dp distPeer) uint64 {
+			peer := dp.(*serverPeer)
+			return peer.getRequestCost(GetBlockHeadersMsg, 1)
+		},
+		canSend: func(dp distPeer) bool {
+			return dp.(*serverPeer) == pc.peer
+		},
+		request: func(dp distPeer) func() {
+			peer := dp.(*serverPeer)
+			cost := peer.getRequestCost(GetBlockHeadersMsg, 1)
+			peer.fcServer.QueuedRequest(reqID, cost)
+			return func() { peer.requestHeadersByNumber(reqID, number, 1, 0, false) }
+		},
+	}
+	var header *types.Header
+	if err := pc.handler.backend.retriever.retrieve(context, reqID, rq, func(peer distPeer, msg *Msg) error {
+		if msg.MsgType != MsgBlockHeaders {
+			return errInvalidMessageType
+		}
+		headers := msg.Obj.([]*types.Header)
+		if len(headers) != 1 {
+			return errInvalidEntryCount
+		}
+		header = headers[0]
+		return nil
+	}, nil); err != nil {
+		return nil, err
+	}
+	return header, nil
+}
+
 // downloaderPeerNotify implements peerSetNotify
 type downloaderPeerNotify clientHandler