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Tim Sweeney has a point about Fortnite EAC support

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One of the big topics of discourse in the Linux gaming sphere recently has been Tim Sweeney's statement on porting Fortnite to the Steam Deck, where Sweeney argues that Linux would be too difficult of a target and the market not big enough to warrant the amount of resources it would take to bring all of Fortnite on the platform.

The central crux of the issue, from Sweeney's point of view, is that making Easy Anti-Cheat, with all of its capabilities, run on Steam Deck (and thus on Linux) would be extremely difficult. He argues, that for a game of Fortnite's size this would open the flood-gates to significant influx of cheaters.

There have been some responses to this from the Linux side, with some accusing Sweeney of exaggerating the difficulty of such a port or that his statements are conflicting, because he simultaneously believes the Linux market is too small to be worthwhile but also would provide a way for too many cheaters. I will address some of these aspects a bit later, but for now let's focus on the main technical blocker, which is Easy Anti-Cheat.

Easy Anti-Cheat, or EAC, is an anti-cheat solution which apparently comes in a few configurations. We know that it can be run in a configuration where it is compatible with Linux/Proton apparently with just a relatively simple toggle. However, this mode of operation is seemingly a comparatively high-trust configuration, where only part of the anti-tampering protections of EAC are active. This may prevent some cheats but fail to detect others, which can be perfectly reasonable for games, where the number of cheaters and potential cheaters are fairly low or other systems complement the anti-cheat solution. There are plenty of games, even some popular free-to-play titles, which at best have this level of anti-tamper protection and they don't seem to have a major cheating epidemic, so clearly in many cases this should be enough. We also don't know the scope of cheats that are detected by EAC in this configuration, so this system by itself may already be fairly comprehensive.

EAC also contains a kernel-level component, which on Windows is installed as a kernel driver. This allows EAC code to run at a very privileged level and inspect essentially any and all parts of the system in order to detect tampering. This provides a very broad level of monitoring, which is also harder to bypass. Based on Sweeney's comments, this is the mode of operation used by Fortnite. It is also a mode of operation that is technically incompatible with the Linux way of doing things.

In Linux, the standard way of delivering drivers is by submitting the driver into the kernel source code tree, which naturally requires that the driver be open source. Most drivers are delivered this way, where the driver gets tightly integrated into the kernel and the drivers are updated when the kernel is updated. There are of course some notable exceptions to this rule, the largest of which is the Nvidia driver. The Nvidia driver is instead loaded as a separate kernel module, which allows Nvidia to keep its source code hidden, but also allows the driver to be updated separately from the kernel. So, EAC could surely use this approach as well, right?

The separate kernel module approach comes with some gotchas. Firstly, the kernel is licensed under GPLv2 and many of the parts in the kernel require the calling code to also be GPLv2 due to the "viral" quality of GPL. This means that, legally speaking, if Epic were to turn EAC into a kernel module and started poking around the kernel APIs, they'd have to open source EAC or they'd be in a legal grey area. The first approach is obviously not possible due to their business model and the second is at least not a great look.

Another problem with separate kernel modules is that the Linux kernel only guarantees a stable user-facing interface. This means that almost anything is allowed to change inside the kernel as long as user-level programs continue functioning. This is also the reason why sometimes the Nvidia driver stops working when you upgrade from one kernel to the next without installing an up-to-date Nvidia driver as well. So, when Sweeney is complaining about the multitude of kernel configurations, he's not wrong. EAC would need to maintain a compatibility shim similar to that of the Nvidia driver, which ensures that the EAC kernel module functions with each kernel version out there. Every time the kernel updates, an EAC engineer would need to go over the changes and update the compatibility shim every time there's a breaking change while still maintaining the compatibility with older kernel versions.

Theoretically you could overcome this problem somewhat by only targeting the Steam Deck and its SteamOS. This would give you a single kernel version to target, although Epic would need to negotiate with Valve in order to ensure their driver is somehow shipped with SteamOS.

But the problems don't end there. Since Linux is a fully open platform, there is technically nothing that would prevent a determined cheater from cracking open the Linux source code and making some tactical changes to how the kernel behaves, building the kernel and then making the EAC kernel module blind. On Windows the EAC developers can assume that the black box that is the NT kernel is at least somewhat difficult to modify by users. This means that in kernel-space they can assume some level of security through obscurity. On Linux this assumption does not hold. The only way for Epic to overcome that problem would be to negotiate with Valve to lock down the Steam Deck, which Valve has already decided not to do.

So, from EAC's point of view the Linux platform can never be quite fully trusted, which is entirely fair, because from the user's point of view EAC can never be quite fully trusted.

But surely Epic could still somehow bring Fortnite to the Steam Deck, right? Surely they could ship a version of Fortnite without the kernel-level component, right?

That they could, which brings us to the points about market share and the viability of cheating. Sweeney argues that the Linux market is too small, which initially sounds a bit odd because he then goes on to worry about the large numbers of cheaters. The kicker is here that the small Linux market doesn't necessarily guarantee a low number of cheaters. If it turns out that certain cheats are possible via a Linux version of Fortnite, this will attract some cheaters to use the platform in order to bypass EAC. It won't be all of the cheaters, many casual cheaters would likely not bother to learn Linux in order to cheat in a video game, but there is no doubt a group of cheaters that would take the opportunity. So, Fortnite would see some increase in cheating, but without good data it is hard to determine how big that effect would be. However, considering the popularity and free-to-play nature of Fortnite, it could very well be that it would be an attractive enough target for cheaters to attack even if there is a slightly higher initial investment. Cheat makers on the other hand would probably eventually find ways to package their offerings in an accessible enough format, like boot-to-cheat USBs or pre-configured VM images.

Some solutions to this problem have been proposed. For example, they could silo Steam Deck/Linux users in such a way that they will never come into contact with the rest of the playerbase. This would contain cheating, but it's also a hard-handed measure that would likely be unpopular. It would also require some amount of work to accomplish and I think it's fair for Epic to discount options that would cause extra work on them.

So, what's the solution to the problem? Here's the thing: I don't think there is one. My personal opinion is that client-side anti-cheat is fundamentally limited and taking it into the kernel is a bandaid that comes with excessive cost and is simply incompatible with the Linux platform. So, as long as Epic insists on maintaining its current anti-cheat approach with Fortnite, I just don't think there's going to be Fortnite on Linux.

And that doesn't mean Tim Sweeney is wrong or lying about the difficulties of adapting that approach to Linux. It just means that a new or different approach is needed in the future.

Article taken from GamingOnLinux.com.
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I'm a Linux gamer from Finland. I like reading, long walks on the beach, dying repeatedly in roguelikes and ripping and tearing in FPS games. I also sometimes write code and sometimes that includes hobbyist game development.
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148 comments
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elmapul 13 Feb
The global cheating market is estimated to move at least100 millions per year
source:
Anti-Cheat for Multiplayer Games

https://youtu.be/hI7V60r7Jco
time: 12:40

this was before they were acquired by Epic.
14 14 Feb
Quoting: slaapliedjeThere is a solution to this Fortnite business... Valve should work on a better game! Guaranteed if something similar enough, but better comes along, Fortnite will be left in the dust, and 20 years from now when the kids that enjoy it get nostalgic, they will have recreated server side software to be able to play it themselves.
I don't feel like Valve has enough developers to create a wildly popular game. CS:GO and Dota 2 have been going strong a long time and have "production mode" dev teams. Half-Life: Alyx was a good step for the gaming industry, but a little niche and experimental as far as the market goes (VR only). So I don't think they even have a desire to compete with a game like Fortnite and PUBG. Do I think a Dota 2 world of characters in a first-person or third-person battle royale setting could be fun? Yes! Would it feel great if it was built with Source engine? No! It would feel stiff and old. Also, Valve already has a black spot on its record with the poor reception of Artifact; if their next game isn't great, their game invention and credibility will majorly tank if they have two bad eggs in a row. Come to think of it, weren't both Counter-Strike and Dota 2 rip-offs of other games (or mods) at the time? Maybe Half-Life is their only glorious original creation. Portal is amazing, although, IIRC, they hired on someone who made the concept of the game, so that was an acquired creation.

I'll stop my drabble. Anyway, I would be very surprised if Valve tried to compete with Fortnite.
Hooly 14 Feb
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Quoting: Koopacabras
Quoting: EagleDelta
Quoting: Koopacabraswhat I don't get about this whole article... is how does the heck Fortnite for Android works? and I think there's enough android "distros" out there, that have plenty of different kernels. Did google let them run a proprietary module on their kernels?
I'm sorry if my question is too stupid I simply ignore this.

They will detect if you are running with root, or running with an unlocked bootloader, or try to see if you're running a custom ROM and block those things.
that probably can be easily bypassed with MagisK. There's actually nothing preventing me from patching my own kernel and building a custom rom image, with a patched kernel to run on my android device (and running fortnite with full customized kernel). I don't see that being any different from Linux distros, It might be a little more complicated to setup and compile, than lets say installing xanmod or liquorix kernel, but it's totally doable.

Anyway... I think that clearly, they are not relying on a kernel module on android, so all this about GPL incompatibilities with EAC and the kernel is all nonsense.

Besides let's not make it about Linux only tho... I think that probably Apple wouldn't allow a kernel module for anticheat on their kernel, for the obvious security reasons.

In my opinion...this is not about Linux only, Google banned fortnite from their play store, Apple did likewise. So maybe the problem is Epic here. Maybe their app wants unlimited trust, their app needs more permissions and priviliges, than anything out there, so it's getting banned, for security reasons.
And Sweeney is so blinded with greed, that cannot see the Elephant in the room here.
Android is moving towards hardware-based attestation, which means that Magisk will come to an end eventually, regardless.

The reason why this practice of kernel-based anti-cheat is ok on desktop but not on mobile is because the OS vendors (Google and Apple, respectively) do not allow it.
The desktop security model however, is so broken that nobody even cares anymore.
Hooly 14 Feb
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Quoting: marcusThe standard way to combat this in a normal TPM / remote attestation scenario is to encrypt the communication with a key where only the TPM has the private key to decrypt it. So only the trusted non-manipulated software can read the communicated data. However, routing FPS gaming network traffic through a TPM admittedly is prohibitive ;)
Doesn't matter, the private key has to get there somehow. And how would you verify server-side that the client uses a specific individual TPM? The client could just lie to the server and then reroute the attestation request again.

Like I said, hardware-based attestation does not fix the idiotic idea of trusting the client, and neither was it intended for that to begin with.

If your security model involves placing trust onto the client in any shape or form, then it is deeply flawed, period.
Cyba.Cowboy 16 Feb
Couldn't they just implement anti-cheat software on the server instead?

Correct me if I am wrong, but I would imagine that this would be easier to maintain and it would be far more difficult for potential cheaters to bypass...
RCL 16 Feb
Quoting: Cyba.CowboyCouldn't they just implement anti-cheat software on the server instead?

Correct me if I am wrong, but I would imagine that this would be easier to maintain and it would be far more difficult for potential cheaters to bypass...

If we could, we would. There is a server side component of course, but it is more reactive than preventive. You cannot pipe everything through the server in a fast paced game, e.g. you cannot control mouselook from the server (to prevent aimhacks), or moving the mouse would feel terribly laggy. Same thing with wallhacks because at least some object culling needs to happen on the client otherwise quick strafing left-right next to a wall (or a door) would result in players popping-in late. The devil is in the details like this.
Shmerl 16 Feb
Quoting: Cyba.CowboyCouldn't they just implement anti-cheat software on the server instead?

Correct me if I am wrong, but I would imagine that this would be easier to maintain and it would be far more difficult for potential cheaters to bypass...

They could. But it's equivalent to investing into sophisticated enough AI. They don't want to spend on it. It's cheaper to push spyware junk on the user.


Last edited by Shmerl on 16 February 2022 at 11:32 pm UTC
Shmerl 16 Feb
Quoting: RCLBut it is more reactive than preventive.

No one said you need to have a preventive anti-cheat. Or to put it differently, the elephant in the room is that you don't need it to make the game good enough. But good reactive anti-cheat is a hard and expensive problem to solve. Not impossible.


Last edited by Shmerl on 16 February 2022 at 11:34 pm UTC
Cyba.Cowboy 17 Feb
Quoting: pete910
Quoting: Samsai
Quoting: Lancabanwith everything saifd about the Linux kernel and different versions and hackabiltiy etc. yet it plays on Android, even on 3rd party Roms and Kernels just fine.

Would that not have the same exact issues and from a significantly larger player base than desktop Linux users?

Right now I can take my phone, root it, throw on a different Rom, and even use a different customized kernel, and still play Fortnite. This has been done, proven, viewed, tested, and seems to be OK.
Theoretically yes. I think the overriding issues are that Android is a market big enough to take the risk and generally speaking tech illiterate enough that the likelihood of someone installing a custom ROM to cheat in Fortnite is so unlikely, that it doesn't register as a realistic risk.

Think you've just shot your own argument in the foot there.

It's a given than 99% of cheaters have no clue on how to write a cheat let alone a kernel driver on windows, Which also would be true for Linux side or the deck.

So the entire premise fails as a result of that theory.


The simple fat is that he has no intention of allowing fortnite on the deck. Am sure if the deck had been produced by say Samsung it wouldn't have been an issue.


Quoting: F.Ultra
Quoting: EagleDelta
Quoting: Samsai
Quoting: Lancabanwith everything saifd about the Linux kernel and different versions and hackabiltiy etc. yet it plays on Android, even on 3rd party Roms and Kernels just fine.

Would that not have the same exact issues and from a significantly larger player base than desktop Linux users?

Right now I can take my phone, root it, throw on a different Rom, and even use a different customized kernel, and still play Fortnite. This has been done, proven, viewed, tested, and seems to be OK.
Theoretically yes. I think the overriding issues are that Android is a market big enough to take the risk and generally speaking tech illiterate enough that the likelihood of someone installing a custom ROM to cheat in Fortnite is so unlikely, that it doesn't register as a realistic risk.

From everything I've read, they do try to prevent custom ROMs from playing the game. Even when those Custom ROMs do get it running, they have to have root disabled, play services must be installed, and safetynet must pass its checks, among other things.

So, it still requires a fairly locked down Android OS to run the game.

So in other words, they manage to implement some safeguards even when run under the evil Linux kernel :-)

Exactly. They just don't want it (Fortnite: Battle Royale) to run on their direct competitor's platform (i.e. the Steam Deck)…


Quoting: pete910
Quoting: Samsai
Quoting: Lancabanwith everything saifd about the Linux kernel and different versions and hackabiltiy etc. yet it plays on Android, even on 3rd party Roms and Kernels just fine.

Would that not have the same exact issues and from a significantly larger player base than desktop Linux users?

Right now I can take my phone, root it, throw on a different Rom, and even use a different customized kernel, and still play Fortnite. This has been done, proven, viewed, tested, and seems to be OK.
Theoretically yes. I think the overriding issues are that Android is a market big enough to take the risk and generally speaking tech illiterate enough that the likelihood of someone installing a custom ROM to cheat in Fortnite is so unlikely, that it doesn't register as a realistic risk.

Think you've just shot your own argument in the foot there.

It's a given than 99% of cheaters have no clue on how to write a cheat let alone a kernel driver on windows, Which also would be true for Linux side or the deck.

So the entire premise fails as a result of that theory.


The simple fat is that he has no intention of allowing fortnite on the deck. Am sure if the deck had been produced by say Samsung it wouldn't have been an issue.
Quoting: areamanplaysgame
Quoting: fearnflavioThere is one solution: ship a cloud version of fortnite. Not the best solution but depending on how it is implemented could work.
Several games on the Nintendo switch are cloud based like Control and Kingdom Hearts. There are companies that port your game to the cloud.
Not the best solution, still a solution.

Cloud gaming requires a pretty robust internet connection, though (significantly more internets than you need to simply connect a locally installed game to a server). But given that Fortnite already is (was?) available on mobile platforms, I guess Epic is not particularly worried about delivering a suboptimal experience for their very popular digital clothing store for ten year olds.

Quoting: eridanired123
Quoting: RCLTo all people saying that not trusting the client or moving the game to the cloud is the solution - you seem to ignore the existence of network latency.

False.

Gforcenow latency is pretty fine on LOL, GW2 and BDO which are the competitive games I've played. I can assume other gaming clouds to have similar results. And I'm not a resident of a first world country by any means.

Those calling for Fortnite: Battle Royale to run "out of the cloud" have obviously never been to Australia... Australia's "high-quality" broadband struggles with Fortnite; Battle Royale in its current form; I'd hate to see how bad the experience would be if the entire game was run "out of the cloud". 🙄


Quoting: EagleDelta
Quoting: Koopacabraswhat I don't get about this whole article... is how does the heck Fortnite for Android works? and I think there's enough android "distros" out there, that have plenty of different kernels. Did google let them run a proprietary module on their kernels?
I'm sorry if my question is too stupid I simply ignore this.

They will detect if you are running with root, or running with an unlocked bootloader, or try to see if you're running a custom ROM and block those things.
Quoting: slaapliedje
Quoting: Koopacabras
Quoting: emphyFor someone who pretends to be doing stuff "for the good of the industry", Sweeney is displaying a remarkably short-sighted stance.
Sweeney couldn't care less about the industry, he sued Apple because they are a bunch of whiners. Apple ofc did the right thing, any app that wants to take control of your wallet looks SUS to me. He is just a Tencent puppet and he'll do the Tencent "dance" or anything they'll ask. At this point if you consider Sweeney as someone "neutral" and with "fair" opinions, I'm sorry to tell you, but, unfortunately you are being played. He is just a snake oil salesman and a puppet, the opposite of being independent (like ie an indie dev).
The whole thing was about Epic wanting to be able to have their own store within the game that didn't use Apple's payment methods (thereby skipping giving Apple a cut).
I am on the fence about this, as for one it is about two greedy bullies trying to figure out who should get all of the kids lunch money they are picking on. Think of Apple as the mob racket, and Epic wanting to move into their territory without paying their cut on the new 'service' they provide.

There is a solution to this Fortnite business... Valve should work on a better game! Guaranteed if something similar enough, but better comes along, Fortnite will be left in the dust, and 20 years from now when the kids that enjoy it get nostalgic, they will have recreated server side software to be able to play it themselves.

This is what I would like to see...

Believe it or not, I only started playing Fortnite: Battle Royale late last year ('The Last of Us: Factions MP' is usually my go-to multiplayer game) and it is primarily these three things which appeal to me in the game:
* The "battle royale" concept (start with "x" players and no weapons, scavenge for weapons and fight your way down the the last player), which I've never seen in a game before;
* The expansive maps, which change every couple of months to offer new challenges / content / quests;
* The difficulty of the game, which seems to be "just right" (not too easy, not too difficult), so that one can play and not always win or lose (in comparison, I find that most other multiplayer games are usually either too easy or too difficult).

These are things that could easily be implemented in another game, so an alternative to Fortnite: Battle Royale is not entirely out of the question... Who is up to the challenge, and wants to get a head-start on the Steam Deck?


Quoting: Shmerl
Quoting: Cyba.CowboyCouldn't they just implement anti-cheat software on the server instead?

Correct me if I am wrong, but I would imagine that this would be easier to maintain and it would be far more difficult for potential cheaters to bypass...

They could. But it's equivalent to investing into sophisticated enough AI. They don't want to spend on it. It's cheaper to push spyware junk on the user.

Ah, so the real reason Fortnite: Battle Royale won’t come to the Steam Deck anytime soon is because Epic Games is to cheap and lazy to implement server-based anti-cheat stuff?

Got it.


Quoting: Shmerl
Quoting: RCLBut it is more reactive than preventive.

No one said you need to have a preventive anti-cheat. Or to put it differently, the elephant in the room is that you don't need it to make the game good enough. But good reactive anti-cheat is a hard and expensive problem to solve. Not impossible.

Well a Steam Deck would be tied to a particular ‘Steam’ account and presumably there’s some sort of hardware identifier (a serial number or something) that’s sent to Valve Software’s servers or is readable by software running on the Steam Deck… So just ban those ‘Steam’ accounts and / or identifiers that are known to be cheating.

Even if server-based anti-cheat software was reactive rather than preventive, this’d be a possible solution.

What I don’t understand, is how there are so many online games throughout the world – including for many, many Linux-based operating systems – that operate their own, respective solutions to prevent cheating… Yet Epic Games is adamant that there is absolute no possible way they could do the same?

As has been pointed out by loads of people, this says an awful lot about their anti-cheat solution and I think the real question is (albeit off-topic), is why would a developer even want to consider their anti-cheat solution now that we know how inadequate it is?
RCL 17 Feb
Quoting: ShmerlNo one said you need to have a preventive anti-cheat.

This is a rather bold statement to make, without having the data or likely even an idea about the health of the game. I don't know what grounds you have to state this, but I trust people in the trenches whose full time job is fighting cheaters, and they say otherwise. If you have relevant experience in the area, you're welcome to apply and join the anti-cheat team...

Quoting: ShmerlOr to put it differently, the elephant in the room is that you don't need it to make the game good enough. But good reactive anti-cheat is a hard and expensive problem to solve. Not impossible.

As I said before, there is a server-side anti-cheat and it works in conjunction with the client-side one. Contrary to what is assumed here in the thread, the client isn't absolutely trusted. However, limiting the attack surface is essential to keep the scale of issues small.

Quoting: Cyba.CowboyWhat I don’t understand, is how there are so many online games throughout the world – including for many, many Linux-based operating systems – that operate their own, respective solutions to prevent cheating… Yet Epic Games is adamant that there is absolute no possible way they could do the same?

There are multiple possible explanations for this. First, the games vary wildly in their player base. Cheaters tend to attack popular games where they can make money selling the hacks, if the market for the hacks is small they won't care about the game. Game distribution model matters a lot, too, if the game is behind a paywall, it makes cheating naturally more expensive than when it's free to play. Last but not least, Fortnite security is one of the best in class, as exemplified by statements like these:
https://www.reddit.com/r/FortNiteBR/comments/ftqic7/muselk_speaking_facts/
https://www.reddit.com/r/pcgaming/comments/b1giwg/why_didnt_fortnite_have_a_major_hacker_problem/
https://www.essentiallysports.com/fortnite-keeps-cheaters-at-bay-unlike-valorant-and-call-of-duty-epic-games-esports-news/

All in all, I understand the emotions in this thread, but it doesn't help anyone when people go for the simplest explanation possible - "oh, it's because they are stupid | evil | cheap". Cheating in online games is a serious problem even on consoles, where it is mostly contained (I again encourage watching this video to see how this was achieved: https://www.youtube.com/watch?v=U7VwtOrwceo), much worse on Windows, which is still a relatively open platform (although it moves to become more sealed, which isn't something I personally like), whereas Linux is not even designed to limit their users' freedom, which poses a fundamental and philosophical issue - how to prevent bad behavior on a platform that trusts their users completely? People who are smarter than me are working on this and don't have a good (or economical at least) solution so far.


Last edited by RCL on 17 February 2022 at 2:32 am UTC
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