Steam GetAuthTicketForWebApi in Unreal Engine

When working with Steam in Unreal Engine you may want to authenticate a player to a backend server. The Steamworks documentation on authentication recommends using the Web API for this purpose, where a client generates an auth ticket (ISteamUser::GetAuthTicketForWebApi) which is then sent to the backend server for validation (ISteamUserAuth/AuthenticateUserTicket).

We want to call GetAuthTicketForWebApi from Unreal Engine and expose it to Blueprints. To do this we need to call GetLinkedAccountAuthToken from the Steam subsystem identity interface. I implement this in my game’s custom Game Instance class. Below is an example of how to do this.

To generate a Web API Auth Ticket in Unreal Engine the following should be done:

1. Update your project’s Build.cs file to include the Steamworks, OnlineSubsystem, and OnlineSubsystemSteam modules.

PublicDependencyModuleNames.AddRange(new string[] { ..., "Steamworks", "OnlineSubsystem", "OnlineSubsystemSteam" });

1. Call GetLinkedAccountAuthToken from the Steam subsystem identity interface (here I have implemented this in my custom Game Instance class with method/delegate that’s accessible from Blueprints):

DECLARE_DYNAMIC_DELEGATE_TwoParams(FGetSteamAuthTicketForWebApiResponse, bool, bWasSuccessful, const FString&, AuthToken);

UCLASS()
class MY_GAME_API UMyGameInstance : public UGameInstance
{
  UFUNCTION(BlueprintCallable)
  static void GetSteamAuthTicketForWebApi(const FGetSteamAuthTicketForWebApiResponse& Delegate);
};

#include "OnlineSubsystemNames.h"
#include "OnlineSubsystemSteam.h"
#include "Interfaces/OnlineIdentityInterface.h"

void UMyGameInstance::GetSteamAuthTicketForWebApi(const FGetSteamAuthTicketForWebApiResponse& Delegate)
{
  FOnlineSubsystemSteam* SteamSubsystem = static_cast<FOnlineSubsystemSteam*>(IOnlineSubsystem::Get(STEAM_SUBSYSTEM));
  if (SteamSubsystem != nullptr)
  {
    SteamSubsystem->GetIdentityInterface()->GetLinkedAccountAuthToken(0, TEXT("WebAPI:MyGame"), IOnlineIdentity::FOnGetLinkedAccountAuthTokenCompleteDelegate::CreateLambda([Delegate](int32 LocalUserNum, bool bWasSuccessful, const FExternalAuthToken& AuthToken)
    {
      Delegate.ExecuteIfBound(bWasSuccessful, AuthToken.TokenString);
    }));
  }
}

Note: in the above snippet there is a hardcoded text value “WebAPI:MyGame”, which is composed of two parts separated by a colon.

The first part of this string must be WebAPI to indicate to GetLinkedAccountAuthToken that we want a Web API token from Steam.

The second part is an identity string, this can be whatever you want but the same string must be used when calling AuthenticateUserTicket on your backend server.

The resulting token can then be sent to your backend server for validation. The backend server should call AuthenticateUserTicket to validate the token and ensure the player is who they say they are. Successful validation will return the player’s Steam ID.