Add simple authentication plugin registry and extensibility API.

Signed-off-by: Bradley Grainger <[email protected]>

Author: bgrainger

src/MySqlConnector/Authentication/AuthenticationPlugins.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Collections.Generic;
+
+namespace MySqlConnector.Authentication
+{
+	/// <summary>
+	/// A registry of known authentication plugins.
+	/// </summary>
+	public static class AuthenticationPlugins
+	{
+		/// <summary>
+		/// Registers the specified authentication plugin. The name of this plugin must be unique.
+		/// </summary>
+		/// <param name="plugin">The authentication plugin.</param>
+		public static void Register(IAuthenticationPlugin plugin)
+		{
+			if (plugin is null)
+				throw new ArgumentNullException(nameof(plugin));
+			if (string.IsNullOrEmpty(plugin.Name))
+				throw new ArgumentException("Invalid plugin name.", nameof(plugin));
+
+			lock (s_lock)
+				s_plugins.Add(plugin.Name, plugin);
+		}
+
+		internal static bool TryGetPlugin(string name, out IAuthenticationPlugin plugin)
+		{
+			lock (s_lock)
+				return s_plugins.TryGetValue(name, out plugin);
+		}
+
+		static readonly object s_lock = new object();
+		static readonly Dictionary<string, IAuthenticationPlugin> s_plugins = new Dictionary<string, IAuthenticationPlugin>();
+	}
+}

src/MySqlConnector/Authentication/IAuthenticationPlugin.cs

@@ -0,0 +1,25 @@
+using System;
+
+namespace MySqlConnector.Authentication
+{
+	/// <summary>
+	/// The primary interface implemented by an authentication plugin.
+	/// </summary>
+	public interface IAuthenticationPlugin
+	{
+		/// <summary>
+		/// The authentication plugin name.
+		/// </summary>
+		string Name { get; }
+
+		/// <summary>
+		/// Creates the authentication response.
+		/// </summary>
+		/// <param name="password">The client's password.</param>
+		/// <param name="authenticationData">The authentication data supplied by the server; this is the <code>auth method data</code>
+		/// from the <a href="https://dev.mysql.com/doc/internals/en/connection-phase-packets.html#packet-Protocol::AuthSwitchRequest">Authentication
+		/// Method Switch Request Packet</a>.</param>
+		/// <returns></returns>
+		byte[] CreateResponse(string password, ReadOnlySpan<byte> authenticationData);
+	}
+}