save email and password to encrypted preference

app/build.gradle

@@ -53,6 +53,7 @@ dependencies {
     implementation 'androidx.legacy:legacy-support-v4:1.0.0'
     implementation 'androidx.constraintlayout:constraintlayout:2.0.0-rc1'
     implementation 'androidx.swiperefreshlayout:swiperefreshlayout:1.1.0'
+    implementation 'androidx.security:security-crypto:1.1.0-alpha02'
     implementation 'com.google.android.material:material:1.2.0'
     implementation 'com.google.code.gson:gson:2.8.6'
     implementation 'com.afollestad:aesthetic:1.0.0-beta05'

app/src/main/java/org/mosad/seil0/projectlaogai/MainActivity.kt

@@ -48,6 +48,7 @@ import org.mosad.seil0.projectlaogai.controller.NFCMensaCard
 import org.mosad.seil0.projectlaogai.controller.PreferencesController
 import org.mosad.seil0.projectlaogai.controller.PreferencesController.Companion.cColorAccent
 import org.mosad.seil0.projectlaogai.controller.PreferencesController.Companion.cColorPrimary
+import org.mosad.seil0.projectlaogai.controller.login.LoginController
 import org.mosad.seil0.projectlaogai.fragments.*
 import kotlin.system.measureTimeMillis
 
@@ -174,6 +175,7 @@ class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelecte
         val startupTime = measureTimeMillis {
             PreferencesController.load(this) // load the settings, must be finished before doing anything else
             CacheController(this) // load the cache
+            LoginController.load(this)
         }
         Log.i(className, "startup completed in $startupTime ms")
     }

app/src/main/java/org/mosad/seil0/projectlaogai/controller/login/LoginController.kt

@@ -22,6 +22,89 @@
 
 package org.mosad.seil0.projectlaogai.controller.login
 
-class LoginController {
-    // TODO implement
+import android.content.Context
+import android.content.SharedPreferences
+import android.security.keystore.KeyGenParameterSpec
+import android.security.keystore.KeyProperties
+import android.util.Log
+import androidx.security.crypto.EncryptedSharedPreferences
+import androidx.security.crypto.MasterKey
+import org.mosad.seil0.projectlaogai.R
+
+object LoginController {
+
+    var email = ""
+        internal set
+
+    /**
+     * initially load the users email
+     */
+    fun load(context: Context) {
+        with(getEncryptedPreferences(context)) {
+            email = this?.getString(
+                context.getString(R.string.save_key_user_email),
+                context.getString(R.string.sample_user)
+            ).toString()
+        }
+    }
+
+    /**
+     * save user email and password to encrypted preference
+     */
+    fun saveCredentials(email: String, password: String, context: Context) {
+        this.email = email
+
+        with (getEncryptedPreferences(context)?.edit()) {
+            this?.putString(context.getString(R.string.save_key_user_email), email)
+            this?.putString(context.getString(R.string.save_key_user_password), password)
+            this?.apply()
+        }
+
+    }
+
+    /**
+     * read user email and password from encrypted preference
+     */
+    fun readCredentials(context: Context): Pair<String, String> {
+        return with (getEncryptedPreferences(context)) {
+            email = this?.getString(context.getString(R.string.save_key_user_email), "").toString()
+
+            Pair(
+                this?.getString(context.getString(R.string.save_key_user_email), "").toString(),
+                this?.getString(context.getString(R.string.save_key_user_password), "").toString()
+            )
+        }
+    }
+
+    /**
+     * create a encrypted shared preference
+     */
+    private fun getEncryptedPreferences(context: Context): SharedPreferences? {
+        return try {
+            val spec = KeyGenParameterSpec.Builder(MasterKey.DEFAULT_MASTER_KEY_ALIAS,
+                KeyProperties.PURPOSE_ENCRYPT or KeyProperties.PURPOSE_DECRYPT)
+                .setBlockModes(KeyProperties.BLOCK_MODE_GCM)
+                .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)
+                .setKeySize(MasterKey.DEFAULT_AES_GCM_MASTER_KEY_SIZE)
+                .build()
+
+            val masterKey = MasterKey.Builder(context)
+                .setKeyGenParameterSpec(spec)
+                .build()
+
+            EncryptedSharedPreferences.create(
+                context,
+                context.getString(R.string.encrypted_preference_file_key),
+                masterKey,
+                EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
+                EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
+            )
+        } catch (ex: Exception) {
+            Log.e(javaClass.name, "Could not create encrypted shared preference.", ex)
+            null
+        }
+    }
+
+
+
 }

app/src/main/java/org/mosad/seil0/projectlaogai/fragments/SettingsFragment.kt

@@ -55,6 +55,7 @@ import org.mosad.seil0.projectlaogai.controller.PreferencesController.Companion.
 import org.mosad.seil0.projectlaogai.controller.PreferencesController.Companion.cCourse
 import org.mosad.seil0.projectlaogai.controller.PreferencesController.Companion.cShowBuffet
 import org.mosad.seil0.projectlaogai.controller.cache.TimetableController
+import org.mosad.seil0.projectlaogai.controller.login.LoginController
 import org.mosad.seil0.projectlaogai.uicomponents.dialogs.LoginDialog
 import org.mosad.seil0.projectlaogai.util.DataTypes
 import java.util.*
@@ -104,6 +105,7 @@ class SettingsFragment : Fragment() {
         super.onViewCreated(view, savedInstanceState)
 
         // initialize the settings gui
+        txtView_User.text = LoginController.email
         txtView_Course.text = cCourse.courseName
         txtView_AboutDesc.text =  resources.getString(R.string.about_version, BuildConfig.VERSION_NAME, getString(R.string.build_time))
         switch_buffet.isChecked = cShowBuffet // init switch
@@ -139,10 +141,11 @@ class SettingsFragment : Fragment() {
             LoginDialog(context!!)
                 .positiveButton {
                     println("Test: $password")
+                    LoginController.saveCredentials(email, password, context)
                 }
                 .show {
-                    email = resources.getString(R.string.sample_user)
-                    password = "Test123"
+                    email = LoginController.email
+                    password = ""
                 }
         }
 

app/src/main/java/org/mosad/seil0/projectlaogai/uicomponents/dialogs/AddSubjectDialog.kt

@@ -50,8 +50,8 @@ class AddSubjectDialog(val context: Context) {
 
     private val dialog = MaterialDialog(context, BottomSheet())
 
-    private var spinnerCourses: Spinner
-    private var spinnerSubjects: Spinner
+    private val spinnerCourses: Spinner
+    private val spinnerSubjects: Spinner
 
     private val subjectsList = ArrayList<String>()
     private val courseNamesList = getCourseNames()

app/src/main/res/values/strings.xml

@@ -98,6 +98,7 @@
 
     <!-- save keys -->
     <string name="preference_file_key" translatable="false">org.mosad.seil0.projectlaogai_preferences</string>
+    <string name="encrypted_preference_file_key" translatable="false">org.mosad.seil0.projectlaogai_encrypted_preferences</string>
     <string name="save_key_course" translatable="false">org.mosad.seil0.projectlaogai.course</string>
     <string name="save_key_courseTTLink" translatable="false">org.mosad.seil0.projectlaogai.courseTTLink</string>
     <string name="save_key_colorPrimary" translatable="false">org.mosad.seil0.projectlaogai.colorPrimary</string>
@@ -106,6 +107,8 @@
     <string name="save_key_coursesCacheTime" translatable="false">org.mosad.seil0.projectlaogai.coursesCacheTime</string>
     <string name="save_key_mensaCacheTime" translatable="false">org.mosad.seil0.projectlaogai.mensaCacheTime</string>
     <string name="save_key_timetableCacheTime" translatable="false">org.mosad.seil0.projectlaogai.timetableCacheTime</string>
+    <string name="save_key_user_email" translatable="false">org.mosad.seil0.projectlaogai.user_email</string>
+    <string name="save_key_user_password" translatable="false">org.mosad.seil0.projectlaogai.user_password</string>
 
 
     <string-array name="courses">