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Process SkinData asynchronously #6589

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Process SkinData asynchronously #6589

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e45f989
process SkinData asynchronously
Blackjack200 Dec 28, 2024
832c9cd
check whether session is online
Blackjack200 Dec 28, 2024
2e69cf2
Fix: Prevent skin overwrite when multiple skin change tasks run concu…
Blackjack200 Dec 28, 2024
844cc8e
Fix: Correct disconnect message for invalid login UUID
Blackjack200 Dec 28, 2024
a8cddf2
fix codestyle...
Blackjack200 Dec 28, 2024
30ed339
onCompletion(): replace instanceof check with @var for consistency
Blackjack200 Dec 29, 2024
438d7ce
Fix missing handling for invalid base64 data case and adjust other code
Blackjack200 Dec 29, 2024
d3b54db
...
Blackjack200 Dec 29, 2024
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70 changes: 70 additions & 0 deletions src/network/mcpe/ProcessSkinTask.php
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Original file line number Diff line number Diff line change
@@ -0,0 +1,70 @@
<?php

/*
*
* ____ _ _ __ __ _ __ __ ____
* | _ \ ___ ___| | _____| |_| \/ (_)_ __ ___ | \/ | _ \
* | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
* | __/ (_) | (__| < __/ |_| | | | | | | | __/_____| | | | __/
* |_| \___/ \___|_|\_\___|\__|_| |_|_|_| |_|\___| |_| |_|_|
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* @author PocketMine Team
* @link http://www.pocketmine.net/
*
*
*/

declare(strict_types=1);

namespace pocketmine\network\mcpe;

use pocketmine\entity\InvalidSkinException;
use pocketmine\entity\Skin;
use pocketmine\network\mcpe\convert\TypeConverter;
use pocketmine\network\mcpe\protocol\types\skin\SkinData;
use pocketmine\scheduler\AsyncTask;
use pocketmine\thread\NonThreadSafeValue;

class ProcessSkinTask extends AsyncTask{
private const KEY_ON_COMPLETION = "onCompletion";
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private ?string $error = "Unknown";
/** @var NonThreadSafeValue<SkinData> */
private NonThreadSafeValue $skinData;

/**
* @param \Closure(?Skin $skin,?string $error) : void $callback
*/
public function __construct(
SkinData $skinData,
\Closure $callback,
){
$this->skinData = new NonThreadSafeValue($skinData);
$this->storeLocal(self::KEY_ON_COMPLETION, $callback);
}

public function onRun() : void{
try{
$skin = TypeConverter::getInstance()->getSkinAdapter()->fromSkinData($this->skinData->deserialize());
$this->setResult($skin);
$this->error = null;
}catch(\InvalidArgumentException|InvalidSkinException $e){
$this->error = $e->getMessage();
}
}

public function onCompletion() : void{
$result = $this->getResult();
if(!($result instanceof Skin)){
$result = null;
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}
/** @var \Closure(?Skin $skin,?string $error) : void $callback */
$callback = $this->fetchLocal(self::KEY_ON_COMPLETION);
($callback)($result, $this->error);
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}
}
27 changes: 20 additions & 7 deletions src/network/mcpe/handler/InGamePacketHandler.php
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,7 @@
use pocketmine\block\utils\SignText;
use pocketmine\entity\animation\ConsumingItemAnimation;
use pocketmine\entity\Attribute;
use pocketmine\entity\InvalidSkinException;
use pocketmine\entity\Skin;
use pocketmine\event\player\PlayerEditBookEvent;
use pocketmine\inventory\transaction\action\DropItemAction;
use pocketmine\inventory\transaction\InventoryTransaction;
Expand All @@ -40,12 +40,14 @@
use pocketmine\item\WritableBook;
use pocketmine\item\WritableBookPage;
use pocketmine\item\WrittenBook;
use pocketmine\lang\KnownTranslationFactory;
use pocketmine\math\Facing;
use pocketmine\math\Vector3;
use pocketmine\nbt\tag\CompoundTag;
use pocketmine\nbt\tag\StringTag;
use pocketmine\network\mcpe\InventoryManager;
use pocketmine\network\mcpe\NetworkSession;
use pocketmine\network\mcpe\ProcessSkinTask;
use pocketmine\network\mcpe\protocol\ActorEventPacket;
use pocketmine\network\mcpe\protocol\ActorPickRequestPacket;
use pocketmine\network\mcpe\protocol\AnimatePacket;
Expand Down Expand Up @@ -843,12 +845,23 @@ public function handlePlayerSkin(PlayerSkinPacket $packet) : bool{
$this->lastRequestedFullSkinId = $packet->skin->getFullSkinId();

$this->session->getLogger()->debug("Processing skin change request");
try{
$skin = $this->session->getTypeConverter()->getSkinAdapter()->fromSkinData($packet->skin);
}catch(InvalidSkinException $e){
throw PacketHandlingException::wrap($e, "Invalid skin in PlayerSkinPacket");
}
return $this->player->changeSkin($skin, $packet->newSkinName, $packet->oldSkinName);
$this->player->getServer()->getAsyncPool()->submitTask(new ProcessSkinTask(
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This would probably make the server to freeze / crash if a malicious client floods tons of skin change requests per tick.

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Would the existing $this->gamePacketLimiter be sufficient for skin change packets, or would it be better to implement a separate rate limiter specifically for PlayerSkinPacket to prevent potential flooding?

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If a separate rate limiter is needed, how should we set the values for INCOMING_SKIN_PACKET_PER_TICK = 1 and INCOMING_SKIN_PACKET_BUFFER_TICKS = 100?
Would these settings be appropriate, or should we adjust them further?

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Would the existing $this->gamePacketLimiter be sufficient for skin change packets, or would it be better to implement a separate rate limiter specifically for PlayerSkinPacket to prevent potential flooding?

Probably not. It's supposed to limit all packets, so it has quite generous limits.

More so the issue here is memory overload if the client spams a lot of skin change packets (it could cause a large backlog in the worker pool & hog a lot of memory).

My thought was to limit the number of concurrent ProcessSkinTasks per session, but I'm not sure if this is the best way.

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@Blackjack200 Blackjack200 Dec 29, 2024 •
edited
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Limiting the rate of PlayerSkinPacket packets seems easier to implement and would have a similar effect to limiting the number of concurrent ProcessSkinTask.

In my preliminary testing, setting INCOMING_SKIN_PACKET_PER_TICK = 0.1 and INCOMING_SKIN_PACKET_BUFFER_TICKS = 20 seems promising (though it still needs sufficient testing). However, this would require changing the $averagePerTick in PacketLimiter from an int to a float or both. Would that be acceptable?

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No, I don't think so. The number of packets isn't the only factor we need to consider. We also have to be aware of how long each packet takes to process.

Under normal conditions the packets might take 10 ms each to process, but an attacker could craft packets that take 10-100x longer to process and still be subject to the same packets-per-tick limits (getting more lag per packet). That's why I said we probably need to limit the number of tasks, rather than the number of packets.

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No, I don't think so. The number of packets isn't the only factor we need to consider. We also have to be aware of how long each packet takes to process.

Under normal conditions the packets might take 10 ms each to process, but an attacker could craft packets that take 10-100x longer to process and still be subject to the same packets-per-tick limits (getting more lag per packet). That's why I said we probably need to limit the number of tasks, rather than the number of packets.

Aside from the better methods for now, we could consider handling these potential time-bomb data by spawning new processes, similar to ConsoleReaderChildProcess. This would allow the main thread to control their runtime, using OS-level process killing (with proper abstraction for generalization—I’ve already implemented this in my private project, leveraging opis/closure). However, this approach does come with challenging compatibility issues.

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That sounds overengineered to me.

$packet->skin,
function(?Skin $skin, ?string $error) use ($packet) : void{
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if($error !== null){
$this->session->disconnectWithError(
reason: "Invalid skin: " . $error,
disconnectScreenMessage: KnownTranslationFactory::disconnectionScreen_invalidSkin()
);
return;
}
if($skin !== null){
$this->player->changeSkin($skin, $packet->newSkinName, $packet->oldSkinName);
$this->session->getLogger()->debug("Skin change request processed");
}
}
));
return true;
}

public function handleSubClientLogin(SubClientLoginPacket $packet) : bool{
Expand Down
41 changes: 28 additions & 13 deletions src/network/mcpe/handler/LoginPacketHandler.php
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Original file line number Diff line number Diff line change
Expand Up @@ -23,14 +23,15 @@

namespace pocketmine\network\mcpe\handler;

use pocketmine\entity\InvalidSkinException;
use pocketmine\entity\Skin;
use pocketmine\event\player\PlayerPreLoginEvent;
use pocketmine\lang\KnownTranslationFactory;
use pocketmine\lang\Translatable;
use pocketmine\network\mcpe\auth\ProcessLoginTask;
use pocketmine\network\mcpe\JwtException;
use pocketmine\network\mcpe\JwtUtils;
use pocketmine\network\mcpe\NetworkSession;
use pocketmine\network\mcpe\ProcessSkinTask;
use pocketmine\network\mcpe\protocol\LoginPacket;
use pocketmine\network\mcpe\protocol\types\login\AuthenticationData;
use pocketmine\network\mcpe\protocol\types\login\ClientData;
Expand All @@ -41,6 +42,7 @@
use pocketmine\player\PlayerInfo;
use pocketmine\player\XboxLivePlayerInfo;
use pocketmine\Server;
use pocketmine\utils\AssumptionFailedError;
use Ramsey\Uuid\Uuid;
use function is_array;

Expand Down Expand Up @@ -70,19 +72,33 @@ public function handleLogin(LoginPacket $packet) : bool{

$clientData = $this->parseClientData($packet->clientDataJwt);

try{
$skin = $this->session->getTypeConverter()->getSkinAdapter()->fromSkinData(ClientDataToSkinDataHelper::fromClientData($clientData));
}catch(\InvalidArgumentException | InvalidSkinException $e){
$this->session->disconnectWithError(
reason: "Invalid skin: " . $e->getMessage(),
disconnectScreenMessage: KnownTranslationFactory::disconnectionScreen_invalidSkin()
);
$this->server->getAsyncPool()->submitTask(new ProcessSkinTask(
ClientDataToSkinDataHelper::fromClientData($clientData),
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function(?Skin $skin, ?string $error) use ($packet, $clientData, $extraData){
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if($error !== null){
$this->session->disconnectWithError(
reason: "Invalid skin: " . $error,
disconnectScreenMessage: KnownTranslationFactory::disconnectionScreen_invalidSkin()
);
return;
}
if($skin === null){
throw new AssumptionFailedError("This should never happen...");
}
$this->onSkinParsed($extraData, $clientData, $skin, $packet);
},
));

return true;
}
return true;
}

private function onSkinParsed(AuthenticationData $extraData, ClientData $clientData, Skin $skin, LoginPacket $packet) : void{
if(!Uuid::isValid($extraData->identity)){
throw new PacketHandlingException("Invalid login UUID");
$this->session->disconnectWithError(
reason: "Invalid login uuid",
disconnectScreenMessage: KnownTranslationFactory::disconnectionScreen_notAuthenticated()
);
return;
}
$uuid = Uuid::fromString($extraData->identity);
$arrClientData = (array) $clientData;
Expand Down Expand Up @@ -136,12 +152,11 @@ public function handleLogin(LoginPacket $packet) : bool{
$ev->call();
if(!$ev->isAllowed()){
$this->session->disconnect($ev->getFinalDisconnectReason(), $ev->getFinalDisconnectScreenMessage());
return true;
return;
}

$this->processLogin($packet, $ev->isAuthRequired());

return true;
}

/**
Expand Down
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