Android keychain

Author: colbylwilliams

NomadCode.Azure/NomadCode.Azure/AzureClient/Keychain.cs

@@ -3,8 +3,20 @@
 using System;
 
 #if __IOS__
+
 using Foundation;
 using Security;
+
+#elif __ANDROID__
+
+using System.Collections.Generic;
+
+using Java.IO;
+using Java.Security;
+using Javax.Crypto;
+
+using Android.Content;
+
 #endif
 
 namespace NomadCode.Azure
@@ -56,43 +68,159 @@ bool saveItemToKeychain (string service, string account, string privateKey)
 
 			var success = status == SecStatusCode.Success;
 
-			if (!success) Console.WriteLine ($"Error in Keychain: {status}");
+			if (!success)
+			{
+				System.Diagnostics.Debug.WriteLine ($"Error in Keychain: {status}");
+				System.Diagnostics.Debug.WriteLine ($"If you are seeing error code '-34018' got to Project Options -> iOS Bundle Signing -> make sure Entitlements.plist is populated for Custom Entitlements for iPhoneSimulator configs");
+			}
 
 			return success;
 		}
 
 
-		void removeItemFromKeychain (string service)
+		bool removeItemFromKeychain (string service)
 		{
 			var record = genericRecord (service);
 
-			SecKeyChain.Remove (record);
+			var status = SecKeyChain.Remove (record);
+
+			var success = status == SecStatusCode.Success;
+
+			if (!success)
+			{
+				System.Diagnostics.Debug.WriteLine ($"Error in Keychain: {status}");
+				System.Diagnostics.Debug.WriteLine ($"If you are seeing error code '-34018' got to Project Options -> iOS Bundle Signing -> make sure Entitlements.plist is populated for Custom Entitlements for iPhoneSimulator configs");
+			}
+
+			return success;
 		}
 
 #else
 
-		// to implement, check out the links below:
-		// https://github.com/sameerkapps/SecureStorage/blob/master/SecureStorage/Plugin.SecureStorage.Android/SecureStorageImplementation.cs
-		// https://github.com/xamarin/Xamarin.Auth/blob/portable-bait-and-switch/source/Xamarin.Auth.XamarinAndroid/PlatformSpecific/AndroidAccountStore.cs
-		// https://github.com/xamarin/Xamarin.Auth/blob/portable-bait-and-switch/source/Xamarin.Auth.XamarinAndroid/PlatformSpecific/AndroidAccountStore.Async.cs
+		static Dictionary<string, KeyStore> keyStoresCache = new Dictionary<string, KeyStore> ();
+
+
+		KeyStore getKeystore (string service)
+		{
+			var context = Android.App.Application.Context;
+
+			KeyStore keystore;
+
+			var serviceId = $"{context.PackageName}-{service}";
+
+			if (keyStoresCache.TryGetValue (serviceId, out keystore))
+			{
+				return keystore;
+			}
+
+			var password = service.ToCharArray ();
+
+			keystore = KeyStore.GetInstance (KeyStore.DefaultType);
+
+			// var protection = new KeyStore.PasswordProtection (password);
+
+			try
+			{
+				// TODO: this isn't right, fix it
+				using (var stream = context.OpenFileInput (serviceId))
+				{
+					keystore.Load (stream, password);
+				}
+			}
+			catch (FileNotFoundException)
+			{
+				keystore.Load (null, password);
+			}
+
+			keyStoresCache [serviceId] = keystore;
+
+			return keystore;
+		}
 
 
 		Tuple<string, string> getItemFromKeychain (string service)
 		{
-			throw new NotImplementedException ();
+			var context = Android.App.Application.Context;
+
+			var password = service.ToCharArray ();
+
+			var protection = new KeyStore.PasswordProtection (password);
+
+			var keystore = getKeystore (service);
+
+			var aliases = keystore.Aliases ();
+
+			while (aliases.HasMoreElements)
+			{
+				var alias = aliases.NextElement ().ToString ();
+
+				var item = keystore.GetEntry (alias, protection) as KeyStore.SecretKeyEntry;
+
+				if (item != null)
+				{
+					var bytes = item.SecretKey.GetEncoded ();
+
+					var serialized = System.Text.Encoding.UTF8.GetString (bytes);
+
+					return new Tuple<string, string> (alias, serialized);
+				}
+			}
+
+			return null;
 		}
 
 
 		bool saveItemToKeychain (string service, string account, string privateKey)
 		{
-			throw new NotImplementedException ();
+			var context = Android.App.Application.Context;
+
+			var password = service.ToCharArray ();
+
+			var serviceId = $"{context.PackageName}-{service}";
+
+			var keystore = getKeystore (service);
+
+			var item = new KeychainItem (privateKey);
+
+			var secretEntry = new KeyStore.SecretKeyEntry (item);
+
+			keystore.SetEntry (account, secretEntry, new KeyStore.PasswordProtection (password));
+
+			using (var stream = context.OpenFileOutput (serviceId, FileCreationMode.Private))
+			{
+				keystore.Store (stream, password);
+			}
+
+			return true;
 		}
 
 
-		void removeItemFromKeychain (string service)
+		bool removeItemFromKeychain (string service)
 		{
 			throw new NotImplementedException ();
 		}
+
+
+		class KeychainItem : Java.Lang.Object, ISecretKey
+		{
+			const string raw = "RAW";
+
+			byte [] bytes;
+
+			public KeychainItem (string data)
+			{
+				if (data == null) throw new ArgumentNullException ();
+
+				bytes = System.Text.Encoding.UTF8.GetBytes (data);
+			}
+
+			public byte [] GetEncoded () => bytes;
+
+			public string Algorithm => raw;
+
+			public string Format => raw;
+		}
+
 #endif
 	}
 }