Paper/patches/server/0349-Validate-PickItem-Packet-and-kick-for-invalid.patch
Bjarne Koll c5a10665b8
Remove wall-time / unused skip tick protection (#11412)
Spigot still maintains some partial implementation of "tick skipping", a
practice in which the MinecraftServer.currentTick field is updated not
by an increment of one per actual tick, but instead set to
System.currentTimeMillis() / 50. This behaviour means that the tracked
tick may "skip" a tick value in case a previous tick took more than the
expected 50ms.

To compensate for this in important paths, spigot/craftbukkit
implements "wall-time". Instead of incrementing/decrementing ticks on
block entities/entities by one for each call to their tick() method,
they instead increment/decrement important values, like
an ItemEntity's age or pickupDelay, by the difference of
`currentTick - lastTick`, where `lastTick` is the value of
`currentTick` during the last tick() call.

These "fixes" however do not play nicely with minecraft's simulation
distance as entities/block entities implementing the above behaviour
would "catch up" their values when moving from a non-ticking chunk to a
ticking one as their `lastTick` value remains stuck on the last tick in
a ticking chunk and hence lead to a large "catch up" once ticked again.

Paper completely removes the "tick skipping" behaviour (See patch
"Further-improve-server-tick-loop"), making the above precautions
completely unnecessary, which also rids paper of the previous described
incompatibility with non-ticking chunks.
2024-09-19 16:36:07 +02:00

27 lines
1.9 KiB
Diff

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sat, 2 May 2020 03:09:46 -0400
Subject: [PATCH] Validate PickItem Packet and kick for invalid
diff --git a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
index 0ed2d0f5ec9d107e8049aa9e803479ffd341639f..119b9b2c45e3321b4197f3e6a34037e3fa99622d 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -895,7 +895,14 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
@Override
public void handlePickItem(ServerboundPickItemPacket packet) {
PacketUtils.ensureRunningOnSameThread(packet, this, this.player.serverLevel());
- this.player.getInventory().pickSlot(packet.getSlot());
+ // Paper start - validate pick item position
+ if (!(packet.getSlot() >= 0 && packet.getSlot() < this.player.getInventory().items.size())) {
+ ServerGamePacketListenerImpl.LOGGER.warn("{} tried to set an invalid carried item", this.player.getName().getString());
+ this.disconnect(Component.literal("Invalid hotbar selection (Hacking?)"));
+ return;
+ }
+ this.player.getInventory().pickSlot(packet.getSlot()); // Paper - Diff above if changed
+ // Paper end - validate pick item position
this.player.connection.send(new ClientboundContainerSetSlotPacket(-2, 0, this.player.getInventory().selected, this.player.getInventory().getItem(this.player.getInventory().selected)));
this.player.connection.send(new ClientboundContainerSetSlotPacket(-2, 0, packet.getSlot(), this.player.getInventory().getItem(packet.getSlot())));
this.player.connection.send(new ClientboundSetCarriedItemPacket(this.player.getInventory().selected));