Do basic "protection" against RA api tokens in the config

src/BizHawk.Client.EmuHawk/RetroAchievements/RCheevos.Login.cs

@@ -1,3 +1,5 @@
+using BizHawk.Common;
+
 namespace BizHawk.Client.EmuHawk
 {
 	public partial class RCheevos
@@ -57,7 +59,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			var config = _getConfig();
 			Username = config.RAUsername;
-			ApiToken = config.RAToken;
+			ApiToken = SensitiveStrings.DecryptString(config.RAToken);
 
 			if (LoggedIn)
 			{
@@ -65,7 +67,7 @@ namespace BizHawk.Client.EmuHawk
 				if (DoLogin(Username, apiToken: ApiToken))
 				{
 					config.RAUsername = Username;
-					config.RAToken = ApiToken;
+					config.RAToken = SensitiveStrings.EncryptString(ApiToken);
 					PlaySound(_loginSound);
 					return;
 				}
@@ -75,7 +77,7 @@ namespace BizHawk.Client.EmuHawk
 			loginForm.ShowDialog();
 
 			config.RAUsername = Username;
-			config.RAToken = ApiToken;
+			config.RAToken = SensitiveStrings.EncryptString(ApiToken);
 
 			if (LoggedIn)
 			{

src/BizHawk.Common/SensitiveStrings.cs

@@ -0,0 +1,68 @@
+using System.IO;
+using System.Security.Cryptography;
+using System.Text;
+
+namespace BizHawk.Common
+{
+	/// <summary>
+	/// Goals
+	/// 1. Allows for encrypting/decrypting strings, suitable for any sensitive info (e.g. api tokens) to be placed in a config file
+	/// 2. Encryption is unique to a particular machine, so another person with the string can't decrypt it
+	/// 3. ASSUMES ANY ATTACK HAS NO KNOWLEDGE OF THE MACHINE NAME
+	/// 4. As such, DOES NOT protect against attacks which have access to said machine or within the same LAN
+	/// (This is mainly to mitigate sensitive info leaks in the case the user posted the config publicly, unredacted)
+	/// (For anyone who's generally security minded, don't trust this to keep your tokens safe)
+	/// </summary>
+	public static class SensitiveStrings
+	{
+		private static readonly Aes _aes;
+
+		static SensitiveStrings()
+		{
+			_aes = Aes.Create();
+			// lame, but this seems to be the best method to do this...
+			_aes.Key = SHA256Checksum.Compute(Encoding.UTF8.GetBytes(Environment.MachineName));
+			_aes.IV = new byte[_aes.BlockSize / 8];
+			_aes.Mode = CipherMode.CBC;
+			_aes.Padding = PaddingMode.PKCS7;
+		}
+
+		public static string EncryptString(string sensitiveString)
+		{
+			var bytes = Encoding.UTF8.GetBytes(sensitiveString);
+			using var ms = new MemoryStream();
+			using var encryptor = _aes.CreateEncryptor();
+			using (var cryptoStream = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
+			{
+				cryptoStream.Write(bytes, 0, bytes.Length);
+			}
+
+			return Convert.ToBase64String(ms.ToArray());
+		}
+
+		public static string DecryptString(string encryptedString)
+		{
+			try
+			{
+				if (string.IsNullOrEmpty(encryptedString))
+				{
+					return string.Empty;
+				}
+
+				var bytes = Convert.FromBase64String(encryptedString);
+				using var ms = new MemoryStream();
+				using var decryptor = _aes.CreateDecryptor();
+				using (var cryptoStream = new CryptoStream(ms, decryptor, CryptoStreamMode.Write))
+				{
+					cryptoStream.Write(bytes, 0, bytes.Length);
+				}
+
+				return Encoding.UTF8.GetString(ms.ToArray());
+			}
+			catch
+			{
+				return string.Empty;
+			}
+		}
+	}
+}