From f11f2d09071add4c549efb79df61a90aece24bcc Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 13 Jan 2024 14:30:05 +0200
Subject: [PATCH] Check that clients only do calls on entities they possess

---
 source/game/networking.cpp |  9 +++++++++
 source/game/networking.h   |  2 ++
 source/game/remotecall.h   |  2 +-
 source/game/replicator.cpp | 13 ++++++++++++-
 source/game/replicator.h   |  9 ++++++++-
 5 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/source/game/networking.cpp b/source/game/networking.cpp
index fb3d977..1ad4ed1 100644
--- a/source/game/networking.cpp
+++ b/source/game/networking.cpp
@@ -173,6 +173,15 @@ Networking::Player &Networking::create_player(const string &name, uint32_t id)
 	return player;
 }
 
+bool Networking::is_current_sender(uint32_t player_id) const
+{
+	auto i = lower_bound_member(players, player_id, &Player::id);
+	if(i==players.end() || i->id!=player_id)
+		return false;
+
+	return i->owner==current_sender;
+}
+
 void Networking::set_state(State s)
 {
 	if(s==state)
diff --git a/source/game/networking.h b/source/game/networking.h
index 8217bb1..eb97a26 100644
--- a/source/game/networking.h
+++ b/source/game/networking.h
@@ -172,6 +172,8 @@ public:
 	template<typename P, typename F>
 	void send(const P &, F &&);
 
+	bool is_current_sender(std::uint32_t) const;
+
 private:
 	void set_state(State);
 	void protocol_ready(const Net::Protocol &);
diff --git a/source/game/remotecall.h b/source/game/remotecall.h
index f79569c..b8e64dd 100644
--- a/source/game/remotecall.h
+++ b/source/game/remotecall.h
@@ -120,7 +120,7 @@ template<typename P, typename E>
 	requires std::is_base_of_v<Entity, E> && HasEntityIdField<P>
 void RemoteEntityCallBase<P, E>::call(const P &packet)
 {
-	Handle<Entity> entity = this->replicator->find_entity(packet.entity_id);
+	Handle<Entity> entity = this->replicator->find_entity(packet.entity_id, this->replicator->is_server());
 	if(!entity)
 		return;  // TODO report the error somehow
 
diff --git a/source/game/replicator.cpp b/source/game/replicator.cpp
index fa32249..8fefb57 100644
--- a/source/game/replicator.cpp
+++ b/source/game/replicator.cpp
@@ -9,6 +9,11 @@ using namespace std;
 
 namespace Msp::Game {
 
+entity_access_denied::entity_access_denied(uint32_t entity_id):
+	runtime_error(lexical_cast<string>(entity_id))
+{ }
+
+
 Replicator::Replicator(Stage &s, Networking &n):
 	System(s),
 	event_source(stage.get_event_bus()),
@@ -54,9 +59,15 @@ void Replicator::set_protocol(const Net::Protocol &p)
 	add_receiver<Messages::GrantPossession>(*this);
 }
 
-Handle<Entity> Replicator::find_entity(uint32_t id) const
+Handle<Entity> Replicator::find_entity(uint32_t id, bool check_access) const
 {
 	auto i = find_if(entities, [id](const ReplicatedEntity &e){ return e.zygote->get_entity_id()==id; });
+	if(check_access)
+	{
+		uint32_t possessor = (i->possessed ? i->possessed->get_player_id() : 0);
+		if(!possessor || !networking.is_current_sender(possessor))
+			throw entity_access_denied(id);
+	}
 	return (i!=entities.end() ? i->entity : nullptr);
 }
 
diff --git a/source/game/replicator.h b/source/game/replicator.h
index fdbe8f0..3385093 100644
--- a/source/game/replicator.h
+++ b/source/game/replicator.h
@@ -16,6 +16,13 @@ class Possessed;
 class Spawner;
 class Transform;
 
+class entity_access_denied: public std::runtime_error
+{
+public:
+	entity_access_denied(std::uint32_t);
+};
+
+
 class MSPGAME_API Replicator: public System, private Net::PacketReceiver<Messages::SpawnEntity>,
 	private Net::PacketReceiver<Messages::GrantPossession>
 {
@@ -70,7 +77,7 @@ public:
 	template<typename P>
 	void send(std::uint32_t, const P &);
 
-	Handle<Entity> find_entity(std::uint32_t) const;
+	Handle<Entity> find_entity(std::uint32_t, bool = false) const;
 
 	void tick(Time::TimeDelta) override;
 	void deferred_tick() override;
-- 
2.45.2