From 144d42c773ad072e6d2311e76ad86c0fa98d7d85 Mon Sep 17 00:00:00 2001
From: Arceliar <Arceliar@users.noreply.github.com>
Date: Sun, 8 Nov 2020 06:09:55 -0600
Subject: [PATCH] send dht responses via reverse path (fixes some possible DDoS
 issues with the old coord approach)

---
 src/yggdrasil/dht.go    | 10 ++++++----
 src/yggdrasil/router.go |  6 +++---
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/src/yggdrasil/dht.go b/src/yggdrasil/dht.go
index bbc31546..a68ba2bd 100644
--- a/src/yggdrasil/dht.go
+++ b/src/yggdrasil/dht.go
@@ -185,7 +185,7 @@ func dht_ordered(first, second, third *crypto.NodeID) bool {
 
 // Reads a request, performs a lookup, and responds.
 // Update info about the node that sent the request.
-func (t *dht) handleReq(req *dhtReq) {
+func (t *dht) handleReq(req *dhtReq, rpath []byte) {
 	// Send them what they asked for
 	res := dhtRes{
 		Key:    t.router.core.boxPub,
@@ -193,7 +193,7 @@ func (t *dht) handleReq(req *dhtReq) {
 		Dest:   req.Dest,
 		Infos:  t.lookup(&req.Dest, false),
 	}
-	t.sendRes(&res, req)
+	t.sendRes(&res, req, rpath)
 	// Also add them to our DHT
 	info := dhtInfo{
 		key:    req.Key,
@@ -213,13 +213,15 @@ func (t *dht) handleReq(req *dhtReq) {
 }
 
 // Sends a lookup response to the specified node.
-func (t *dht) sendRes(res *dhtRes, req *dhtReq) {
+func (t *dht) sendRes(res *dhtRes, req *dhtReq, rpath []byte) {
 	// Send a reply for a dhtReq
 	bs := res.encode()
 	shared := t.router.sessions.getSharedKey(&t.router.core.boxPriv, &req.Key)
 	payload, nonce := crypto.BoxSeal(shared, bs, nil)
+	path := append([]byte{0}, switch_reverseCoordBytes(rpath)...)
 	p := wire_protoTrafficPacket{
-		Coords:  req.Coords,
+		Offset:  1,
+		Coords:  path,
 		ToKey:   req.Key,
 		FromKey: t.router.core.boxPub,
 		Nonce:   *nonce,
diff --git a/src/yggdrasil/router.go b/src/yggdrasil/router.go
index f89b26f9..089c49e7 100644
--- a/src/yggdrasil/router.go
+++ b/src/yggdrasil/router.go
@@ -204,7 +204,7 @@ func (r *router) _handleProto(packet []byte) {
 	case wire_NodeInfoResponse:
 		r._handleNodeInfo(bs, &p.FromKey)
 	case wire_DHTLookupRequest:
-		r._handleDHTReq(bs, &p.FromKey)
+		r._handleDHTReq(bs, &p.FromKey, p.RPath)
 	case wire_DHTLookupResponse:
 		r._handleDHTRes(bs, &p.FromKey)
 	default:
@@ -227,13 +227,13 @@ func (r *router) _handlePong(bs []byte, fromKey *crypto.BoxPubKey, rpath []byte)
 }
 
 // Decodes dht requests and passes them to dht.handleReq to trigger a lookup/response.
-func (r *router) _handleDHTReq(bs []byte, fromKey *crypto.BoxPubKey) {
+func (r *router) _handleDHTReq(bs []byte, fromKey *crypto.BoxPubKey, rpath []byte) {
 	req := dhtReq{}
 	if !req.decode(bs) {
 		return
 	}
 	req.Key = *fromKey
-	r.dht.handleReq(&req)
+	r.dht.handleReq(&req, rpath)
 }
 
 // Decodes dht responses and passes them to dht.handleRes to update the DHT table and further pass them to the search code (if applicable).