feat: Device Authenticator (#3003)

* feat: Device Authenticator
Uses `SystemInfo.deviceUniqueIdentifier` for authentication.

Assets/Mirror/Authenticators/DeviceAuthenticator.cs

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+using System;
+using UnityEngine;
+
+namespace Mirror.Authenticators
+{
+    /// <summary>
+    /// An authenicator that identifies the user by their device.
+    /// <para>A GUID is used as a fallback when the platform doesn't support SystemInfo.deviceUniqueIdentifier.</para>
+    /// <para>Note: deviceUniqueIdentifier can be spoofed, so security is not guaranteed.</para>
+    /// <para>See https://docs.unity3d.com/ScriptReference/SystemInfo-deviceUniqueIdentifier.html for details.</para>
+    /// </summary>
+    [AddComponentMenu("Network/Authenticators/DeviceAuthenticator")]
+    [HelpURL("https://mirror-networking.gitbook.io/docs/components/network-authenticators/device-authenticator")]
+    public class DeviceAuthenticator : NetworkAuthenticator
+    {
+        #region Messages
+
+        public struct AuthRequestMessage : NetworkMessage
+        {
+            public string clientDeviceID;
+        }
+
+        public struct AuthResponseMessage : NetworkMessage { }
+
+        #endregion
+
+        #region Server
+
+        /// <summary>
+        /// Called on server from StartServer to initialize the Authenticator
+        /// <para>Server message handlers should be registered in this method.</para>
+        /// </summary>
+        public override void OnStartServer()
+        {
+            // register a handler for the authentication request we expect from client
+            NetworkServer.RegisterHandler<AuthRequestMessage>(OnAuthRequestMessage, false);
+        }
+
+        /// <summary>
+        /// Called on server from StopServer to reset the Authenticator
+        /// <para>Server message handlers should be registered in this method.</para>
+        /// </summary>
+        public override void OnStopServer()
+        {
+            // unregister the handler for the authentication request
+            NetworkServer.UnregisterHandler<AuthRequestMessage>();
+        }
+
+        /// <summary>
+        /// Called on server from OnServerAuthenticateInternal when a client needs to authenticate
+        /// </summary>
+        /// <param name="conn">Connection to client.</param>
+        public override void OnServerAuthenticate(NetworkConnection conn)
+        {
+            // do nothing, wait for client to send his id
+        }
+
+        void OnAuthRequestMessage(NetworkConnection conn, AuthRequestMessage msg)
+        {
+            Debug.Log($"connection {conn.connectionId} authenticated with id {msg.clientDeviceID}");
+
+            // Store the device id for later reference, e.g. when spawning the player
+            conn.authenticationData = msg.clientDeviceID;
+
+            // Send a response to client telling it to proceed as authenticated
+            conn.Send(new AuthResponseMessage());
+
+            // Accept the successful authentication
+            ServerAccept(conn);
+        }
+
+        #endregion
+
+        #region Client
+
+        /// <summary>
+        /// Called on client from StartClient to initialize the Authenticator
+        /// <para>Client message handlers should be registered in this method.</para>
+        /// </summary>
+        public override void OnStartClient()
+        {
+            // register a handler for the authentication response we expect from server
+            NetworkClient.RegisterHandler<AuthResponseMessage>((Action<AuthResponseMessage>)OnAuthResponseMessage, false);
+        }
+
+        /// <summary>
+        /// Called on client from StopClient to reset the Authenticator
+        /// <para>Client message handlers should be unregistered in this method.</para>
+        /// </summary>
+        public override void OnStopClient()
+        {
+            // unregister the handler for the authentication response
+            NetworkClient.UnregisterHandler<AuthResponseMessage>();
+        }
+
+        /// <summary>
+        /// Called on client from OnClientAuthenticateInternal when a client needs to authenticate
+        /// </summary>
+        public override void OnClientAuthenticate()
+        {
+            string deviceUniqueIdentifier = SystemInfo.deviceUniqueIdentifier;
+
+            // Not all platforms support this, so we use a GUID instead
+            if (deviceUniqueIdentifier == SystemInfo.unsupportedIdentifier)
+            {
+                // Get the value from PlayerPrefs if it exists, new GUID if it doesn't
+                deviceUniqueIdentifier = PlayerPrefs.GetString("deviceUniqueIdentifier", Guid.NewGuid().ToString());
+
+                // Store the deviceUniqueIdentifier to PlayerPrefs (in case we just made a new GUID)
+                PlayerPrefs.SetString("deviceUniqueIdentifier", deviceUniqueIdentifier);
+            }
+
+            // send the deviceUniqueIdentifier to the server
+            NetworkClient.connection.Send(new AuthRequestMessage { clientDeviceID = deviceUniqueIdentifier } );
+        }
+
+        /// <summary>
+        /// Called on client when the server's AuthResponseMessage arrives
+        /// </summary>
+        /// <param name="msg">The message payload</param>
+        public void OnAuthResponseMessage(AuthResponseMessage msg)
+        {
+            Debug.Log("Authentication Success");
+            ClientAccept();
+        }
+
+        #endregion
+    }
+}

Assets/Mirror/Authenticators/DeviceAuthenticator.cs.meta

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