Various anticheat improvements

* Calculate maximum interact distance from wielded tool
* New "interacted_while_dead" cheat_type for the Lua API
* Disallow dropping items while dead
* Move player to spawn before resurrecting them

doc/lua_api.txt

@@ -2036,9 +2036,10 @@ Call these functions only at load time!
 * `minetest.register_on_cheat(func(ObjectRef, cheat))`
     * Called when a player cheats
     * `cheat`: `{type=<cheat_type>}`, where `<cheat_type>` is one of:
-        * `"moved_too_fast"`
-        * `"interacted_too_far"`
-        * `"finished_unknown_dig"`
+        * `moved_too_fast`
+        * `interacted_too_far`
+        * `interacted_while_dead`
+        * `finished_unknown_dig`
         * `dug_unbreakable`
         * `dug_too_fast`
 * `minetest.register_on_chat_message(func(name, message))`

src/network/serverpackethandler.cpp

@@ -1021,6 +1021,15 @@ void Server::handleCommand_InventoryAction(NetworkPacket* pkt)
 			delete a;
 			return;
 		}
+
+		// Disallow dropping items if dead
+		if (playersao->isDead()) {
+			infostream << "Ignoring IDropAction from "
+					<< (da->from_inv.dump()) << ":" << da->from_list
+					<< " because player is dead." << std::endl;
+			delete a;
+			return;
+		}
 	}
 	/*
 		Handle restrictions and special cases of the craft action
@@ -1313,6 +1322,7 @@ void Server::handleCommand_Interact(NetworkPacket* pkt)
 		2: digging completed
 		3: place block or item (to abovesurface)
 		4: use item
+		5: rightclick air ("activate")
 	*/
 	u8 action;
 	u16 item_i;
@@ -1345,8 +1355,16 @@ void Server::handleCommand_Interact(NetworkPacket* pkt)
 	}
 
 	if (playersao->isDead()) {
-		verbosestream << "TOSERVER_INTERACT: " << player->getName()
-				<< " is dead. Ignoring packet";
+		actionstream << "Server: NoCheat: " << player->getName()
+				<< " tried to interact while dead; ignoring." << std::endl;
+		if (pointed.type == POINTEDTHING_NODE) {
+			// Re-send block to revert change on client-side
+			RemoteClient *client = getClient(pkt->getPeerId());
+			v3s16 blockpos = getNodeBlockPos(pointed.node_undersurface);
+			client->SetBlockNotSent(blockpos);
+		}
+		// Call callbacks
+		m_script->on_cheat(playersao, "interacted_while_dead");
 		return;
 	}
 
@@ -1384,32 +1402,6 @@ void Server::handleCommand_Interact(NetworkPacket* pkt)
 		pointed_pos_above = pointed_pos_under;
 	}
 
-	/*
-		Check that target is reasonably close
-		(only when digging or placing things)
-	*/
-	static const bool enable_anticheat = !g_settings->getBool("disable_anticheat");
-	if ((action == 0 || action == 2 || action == 3) &&
-			(enable_anticheat && !isSingleplayer())) {
-		float d = player_pos.getDistanceFrom(pointed_pos_under);
-		float max_d = BS * 14; // Just some large enough value
-		if (d > max_d) {
-			actionstream << "Player " << player->getName()
-					<< " tried to access " << pointed.dump()
-					<< " from too far: "
-					<< "d=" << d <<", max_d=" << max_d
-					<< ". ignoring." << std::endl;
-			// Re-send block to revert change on client-side
-			RemoteClient *client = getClient(pkt->getPeerId());
-			v3s16 blockpos = getNodeBlockPos(floatToInt(pointed_pos_under, BS));
-			client->SetBlockNotSent(blockpos);
-			// Call callbacks
-			m_script->on_cheat(playersao, "interacted_too_far");
-			// Do nothing else
-			return;
-		}
-	}
-
 	/*
 		Make sure the player is allowed to do it
 	*/
@@ -1432,6 +1424,39 @@ void Server::handleCommand_Interact(NetworkPacket* pkt)
 		return;
 	}
 
+	/*
+		Check that target is reasonably close
+		(only when digging or placing things)
+	*/
+	static const bool enable_anticheat = !g_settings->getBool("disable_anticheat");
+	if ((action == 0 || action == 2 || action == 3 || action == 4) &&
+			(enable_anticheat && !isSingleplayer())) {
+		float d = player_pos.getDistanceFrom(pointed_pos_under);
+		const ItemDefinition &playeritem_def =
+			playersao->getWieldedItem().getDefinition(m_itemdef);
+		float max_d = BS * playeritem_def.range;
+		float max_d_hand = BS * m_itemdef->get("").range;
+		if (max_d < 0 && max_d_hand >= 0)
+			max_d = max_d_hand;
+		else if (max_d < 0)
+			max_d = BS * 4.0;
+		if (d > max_d * 1.5) {
+			actionstream << "Player " << player->getName()
+					<< " tried to access " << pointed.dump()
+					<< " from too far: "
+					<< "d=" << d <<", max_d=" << max_d
+					<< ". ignoring." << std::endl;
+			// Re-send block to revert change on client-side
+			RemoteClient *client = getClient(pkt->getPeerId());
+			v3s16 blockpos = getNodeBlockPos(floatToInt(pointed_pos_under, BS));
+			client->SetBlockNotSent(blockpos);
+			// Call callbacks
+			m_script->on_cheat(playersao, "interacted_too_far");
+			// Do nothing else
+			return;
+		}
+	}
+
 	/*
 		If something goes wrong, this player is to blame
 	*/
@@ -1443,11 +1468,6 @@ void Server::handleCommand_Interact(NetworkPacket* pkt)
 	*/
 	if (action == 0) {
 		if (pointed.type == POINTEDTHING_NODE) {
-			/*
-				NOTE: This can be used in the future to check if
-				somebody is cheating, by checking the timing.
-			*/
-
 			MapNode n(CONTENT_IGNORE);
 			bool pos_ok;
 

src/server.cpp

@@ -2557,15 +2557,15 @@ void Server::RespawnPlayer(u16 peer_id)
 	playersao->setHP(PLAYER_MAX_HP);
 	playersao->setBreath(PLAYER_MAX_BREATH);
 
-	SendPlayerHP(peer_id);
-	SendPlayerBreath(peer_id);
-
 	bool repositioned = m_script->on_respawnplayer(playersao);
-	if(!repositioned){
+	if (!repositioned) {
 		v3f pos = findSpawnPos();
 		// setPos will send the new position to client
 		playersao->setPos(pos);
 	}
+
+	SendPlayerHP(peer_id);
+	SendPlayerBreath(peer_id);
 }