Bypassing Steam Family Sharing Limitations

My brother bought Halo: The Master Chief Collection on Steam. He shared it with me and my sister via Steam Family Library Sharing, but it turns out that only one person can play at a time. I wanted to see if I could find a way around this restriction. Ideally, I'd like to play the game with my siblings.

Trying out the Game

The first thing to notice is that the developers likely intended for players to launch the game from Steam. Attempting to launch the binary (MCC-Win64-Shipping.exe) directly causes Steam.exe to execute and prompt the user to sign in.

If my siblings are not currently playing the game, then we will see a Play button in the Steam client.

Once the game is running, the Play button in the Steam client changes into a Stop button, which indicates that Steam knows that the game is running.

Anti-Cheat Enabled/Disabled Launch

Steam provides two launch options: regular and Anti-Cheat Disabled.

If we choose the first option, then Steam launches the game from the Easy Anti-Cheat (EAC) launcher (mcclauncher.exe). There will be an Easy Anti-Cheat logo when the game first starts.

Upon successfully launching the game, we will reach the main menu screen.

If we launch the game with Anti-Cheat disabled, then we will see this message when we click Multiplayer button in the menu.

Although the game has both a campaign and a multiplayer part, both parts require that the user be signed into Steam.

Progress

I spent a week reversing the game and learning about how the Unreal Engine uses the steamworks API. My goal here was to find a way to launch the game without Steam.

Usually, I will get a Fatal Error in the loading screen.

Or, if I successfully got through the loading screen, I would get the Purchase screen.

Solution: The 480 Trick

I ended up finding the idea for the solution in the steamworks documentation. It turns out that I do not need to find a way to launch the game without Steam in order to play the game with  my siblings. Instead, I launch the game with Steam but tell Steam that I am playing a different game.

Create this file: C:\Program Files (x86)\Steam\steamapps\common\Halo The Master Chief Collection\steam_appid.txt and write 480 in it.

To play with Anti-Cheat disable, launch the game from C:\Program Files (x86)\Steam\steamapps\common\Halo The Master Chief Collection\MCC\Binaries\Win64\MCC-Win64-Shipping.exe.

To play with Multiplayer enabled, launch the game from C:\Program Files (x86)\Steam\steamapps\common\Halo The Master Chief Collection\mcclauncher.exe

Why it Works

This works because 480 is the Steam app ID for Spacewar. Every user automatically has Spacewar. The Steamworks documentation suggest developers use 480 as a temporary app ID when working with the Steam API during the development and testing phase of creating the game.

When we launch the game with 480 as our app ID, the Steam client will report that we are playing Spacewar.

Since the lobby is provided by Steam, in order to join the same lobby, my siblings would also have to be detected as playing Spacewar. Therefore, they would also need to be using the 480 trick. Interestingly, when my brother did this trick, Steam reported that he was playing Spacewar but still reported that Halo was not currently available for family sharing. That means that while he is playing, Steam can still tell that he is using the license for Halo.

Future

Although I figured out how to bypass the Family Sharing restriction, I would still like to find a way to launch the game without Steam. I am also interested in figuring out how to launch the game with Multiplayer enabled but without having to use the Easy Anti-Cheat launcher.

The solution might seem kind of random. In a future post, I will explain the steps I took in reversing the game, which led me to realize that the solution had something to do with the steam_appid.txt.