In short

• EasyAntiCheat under Proton 8.x fails to launch games via 64-bit bootstrapper from EOS SDK v1.15.5
  • With Proton 8.x (build ID 11030361), bootstrapper start_protected_game.exe v1.5.0 (old) works, v1.6.0 (new) breaks
  • Proton 7.x launches the v1.6.0 (new) EAC bootstrapper just fine
  • Should impact all games that update to EOS SDK v1.15.5
  • Tested with Kubuntu 22.04 and Arch Linux

Details

In February 2023 with EOS SDK v1.15.5, Epic Games announced a new version of the anti-cheat bootstrapper start_protected_game.exe, converting it to 64-bit for compatibility with Chromebooks. This also resolved an Unexpected launch error for a friend's system.

• New 64-bit bootstrapper start_protected_game.exe
  • Version code: v1.6.0
  • File size: 3.7 MiB
  • SHA1 checksum 56b5da5dbe085b37b83dcf5d06dba745444b1f98
• Older 32-bit bootstrapper start_protected_game.exe
  • Version code: v1.5.0
  • File size: 3.3 MiB
  • SHA1 checksum 7d401abe97f43a1eefc9a0080583d138f32a41d7

Using Proton 8.x (build ID 11030361) or Proton Experimental, the new (v1.6.0) EAC bootstrapper fails to launch the binary wrapped by anti-cheat. Proton 7.x works just fine.

The older bootstrapper works under Proton 8.x and Proton 7.x.

Why does this matter?

EOS SDK v1.15.5 will likely be used as the basis for future games developed with anti-cheat.

On a personal note, for a friend's computer, the 64-bit anti-cheat Linux module crashes with an Unexpected launch error on the 32-bit bootstrapper v1.5.0. The modern 64-bit bootstrapper v1.6.0 resolves this issue for them, as I discovered and shared in my support thread with Epic Games.

However, 8.x-based Proton Experimental (which includes fixes for AVPro volume blasting in VRChat) cannot run this new bootstrapper, which is required to workaround the Unexpected launch error.

Testing

Steps

1. Find a game using the v1.5.0 version of the EasyAntiCheat bootstrapper
   • As of now (2023-5-1), VRChat is one such free candidate
   • Alternatively, one can follow Epic Games' documentation to build their own EAC-wrapped app - I've assembled a bare-minimum test case I can share if it's acceptable to link to binaries
2. Launch with Proton 7.x and 8.x using the stock v1.5.0 (old) start_protected_game.exe
3. Observe successful game launches
4. Download the updated Epic Games EOS SDK (C# or C++, doesn't matter)
5. Ensure it is version v1.15.5 or newer
6. Extract SDK/Tools/EOS_AntiCheatTools-win32-x64-2.0.0.zip
7. Inside EOS_AntiCheatTools-win32-x64-2.0.0.zip, extract dist\start_protected_game.exe
8. Rename to start_protected_game.exe
9. Overwrite the v1.5.0 (old) start_protected_game.exe shipped with the game in question
   • E.g. for VRChat, overwrite $HOME/.local/share/Steam/steamapps/common/VRChat/start_protected_game.exe
   • NOTE: This may cause EasyAntiCheat validation to fail after the game properly launches. If that is a concern, you can instead copy the bootstrapper as start_protected_game.new.exe and add a shortcut to a non-Steam game to launch that, forcing a compatibility tool.
10. Launch with Proton 7.x and 8.x using this updated v1.6.0 (new) start_protected_game.exe
11. Observe Proton 7.x works, 8.x fails

Expected

The updated v1.6.0 bootstrapper successfully launches the game under Proton 7.x and Proton 8.x.

Actual

The updated v1.6.0 bootstrapper successfully launches the game under Proton 7.x, but under Proton 8.x, it looks like it launches the game, only for it to silently fail after loading the anti-cheat module.

The anti-cheat launcher log does not indicate any error.

NOTE: The log file location has changed, as mentioned in the EOS SDK v1.15.5 release notes.

Deprecated: We deprecated the log file, loader.log, and introduced a new log file, anticheatlauncher.log, as the single log file for the anti-cheat bootstrapper.

Additional information

System details

NOTE: This is slightly out of date regarding software versions - the current Steam Beta fails to copy the system details.

Computer Information:
    Manufacturer:  Gigabyte Technology Co., Ltd.
    Model:  X570 AORUS MASTER
    Form Factor: Desktop
    No Touch Input Detected

Processor Information:
    CPU Vendor:  AuthenticAMD
    CPU Brand:  AMD Ryzen 5 5600X 6-Core Processor             
    CPU Family:  0x19
    CPU Model:  0x21
    CPU Stepping:  0x2
    CPU Type:  0x0
    Speed:  4651 Mhz
    12 logical processors
    6 physical processors
    HyperThreading:  Supported
    FCMOV:  Supported
    SSE2:  Supported
    SSE3:  Supported
    SSSE3:  Supported
    SSE4a:  Supported
    SSE41:  Supported
    SSE42:  Supported
    AES:  Supported
    AVX:  Supported
    AVX2:  Supported
    AVX512F:  Unsupported
    AVX512PF:  Unsupported
    AVX512ER:  Unsupported
    AVX512CD:  Unsupported
    AVX512VNNI:  Unsupported
    SHA:  Supported
    CMPXCHG16B:  Supported
    LAHF/SAHF:  Supported
    PrefetchW:  Unsupported

Operating System Version:
    Ubuntu 22.04.2 LTS (64 bit)
    Kernel Name:  Linux
    Kernel Version:  5.19.0-38-generic
    X Server Vendor:  The X.Org Foundation
    X Server Release:  12101004
    X Window Manager:  KWin
    Steam Runtime Version:  steam-runtime_0.20230118.0

Video Card:
    Driver:  AMD AMD Radeon RX 5600 XT (navi10, LLVM 15.0.6, DRM 3.47, 5.19.0-38-generic)
    Driver Version:  4.6 (Compatibility Profile) Mesa 22.2.5
    OpenGL Version: 4.6
    Desktop Color Depth: 24 bits per pixel
    Monitor Refresh Rate: 60 Hz
    VendorID:  0x1002
    DeviceID:  0x731f
    Revision Not Detected
    Number of Monitors:  1
    Number of Logical Video Cards:  1
    Primary Display Resolution:  1920 x 1080
    Desktop Resolution: 1920 x 1080
    Primary Display Size: 20.04" x 11.26" (22.95" diag)
                                            50.9cm x 28.6cm (58.3cm diag)
    Primary VRAM: 6144 MB

Sound card:
    Audio device: ATI R6xx HDMI

Memory:
    RAM:  32022 MB

VR Hardware:
    Headset: HTC Vive. MV (lighthouse)
    Base station or sensor: HTC HTC V2-XD/XE (lighthouse)
    Base station or sensor: HTC HTC V2-XD/XE (lighthouse)
    Controller: HTC Vive. Controller MV (lighthouse)
    Controller: HTC Vive Controller MV (lighthouse)

Miscellaneous:
    UI Language:  English
    LANG:  en_US.UTF-8
    Total Hard Disk Space Available:  1804284 MB
    Largest Free Hard Disk Block:  1110708 MB

Storage:
    Number of SSDs: 2
    SSD sizes: 2000G,1000G
    Number of HDDs: 0

Proton 7.x with v1.6.0 bootstrapper

Full Proton 7.x PROTON_LOG=1 result available in this zip file.

Example anticheatlauncher.log:

[…trimmed identical lines…]
[04:42:27:922] [Windows] [EAC Launcher] [Info] Current progress: 100 (1/1).
[04:42:27:936] [Windows] [EAC Launcher] [Info] Starting Wine module mapping, Wine version: 7.0.
[04:42:28:835] [Windows] [EAC Launcher] [Info] Launcher finished with: 301, 'Easy Anti-Cheat successfully loaded in-game'.
[04:42:28:835] [Windows] [EAC Launcher] [Info] Successfully initialized the Easy Anti-Cheat service, waiting for game window to become visible.
[04:42:28:836] [Windows] [EAC Launcher] [Info] Unlocking the launch lock, allowing next game to launch to take place.
[04:42:28:869] [Windows] [EAC Launcher] [Info] Downloaded 7788376 bytes in 1546 ms (4919.69 KB/s)

Proton 8.x (build ID 11030361) with v1.6.0 bootstrapper

Full Proton 8.x PROTON_LOG=1 result available in this zip file.

Example anticheatlauncher.log:

[…trimmed identical lines…]
[04:40:40:410] [Windows] [EAC Launcher] [Info] Current progress: 100 (1/1).
[04:40:40:433] [Windows] [EAC Launcher] [Info] Starting Wine module mapping, Wine version: 8.0.
[04:40:42:752] [Windows] [EAC Launcher] [Info] Launcher finished with: 301, 'Easy Anti-Cheat successfully loaded in-game'.
[04:40:42:752] [Windows] [EAC Launcher] [Info] Successfully initialized the Easy Anti-Cheat service, waiting for game window to become visible.
[04:40:42:752] [Windows] [EAC Launcher] [Info] Unlocking the launch lock, allowing next game to launch to take place.
[04:40:42:785] [Windows] [EAC Launcher] [Info] Downloaded 7788376 bytes in 894 ms (8507.65 KB/s)

Let me know if you'd like any additional information! I can reliably reproduce this issue on my system, but I might be overlooking important details.