Mirror/docs/Concepts/Authentication.md

# Authentication

When you have a multiplayer game,  often you need to store information about your player for later games, keep game stats or communicate with your friends. For all these use cases,  you often need a way to uniquely identify a user. Being able to tell users appart is called authentication.  There are several methods available,  some examples include:

* Ask the user for username and password
* Use a third party oath or openid identity provider, such as facebook, twitter, google
* Use a third party service such as playfab, gamelift or steam
* Use the device id,  very popular method in mobile
* Use Google Play in android
* Use Game Center in ios
* Use a web service in your website

Trying to write a comprehensive authentication framework that cover all these is very complex.  There is no one size fit all, and we would quickly end up with bloated code. 

Instead, **Mirror does not perform authentication**,  but we provide hooks you can use to implement any of these. 

Here is an example of how to implement simple username/password authentication:

1) Select your NetworkManager gameobject in the unity editor.
2) In the inspector, under `Spawn Info`, disable `Auto Create Player`
3) Call `AddPlayer` in your client to pass the credentials. 
4) Override the `OnServerAddPlayer` method and validate the user's credential.


For example this would be part of your NetworkManager class:

```cs
class MyGameNetworkManager : NetworkManager {

    class CredentialsMessage : MessageBase
    {
        // use whatever credentials make sense for your game
        // for example,  you might want to pass the accessToken if using oauth
        public string username;
        public string password;
    }

    // this gets called in your client after 
    // it has connected to the server,  
    public override void OnClientConnect(NetworkConnection conn)
    {
        base.OnClientConnect(conn);

        var msg = new CredentialsMessage()
        {
            // perhaps get the username and password
            // from textboxes instead
            username = "Joe",
            password = "Gaba Gaba"
        };

        ClientScene.AddPlayer(connection,   MessagePacker.Pack(msg));
    }

    // this gets called in your server when the 
    // client requests to add a player.
    public override void OnServerAddPlayer(NetworkConnection conn, AddPlayerMessage extraMessage)
    {
        var msg = MessagePacker.Unpack<CredentialsMessage>(extraMessage.value);

        // check the credentials by calling your web server, database table, playfab api, or any method appropriate.
        if (msg.username == "Joe" && msg.password == "Gaba Gaba")
        {
            // proceed to regular add player
            base.OnServerAddPlayer(conn, extraMessage);
        }
        else
        {
            conn.Disconnect();
        }
    }
}

```