Adding Credential Support (RSA)

app/src/main/java/com/mylloon/mobidl/Credentials.kt

@@ -0,0 +1,59 @@
+package com.mylloon.mobidl
+
+import android.os.Build
+import android.security.keystore.KeyProperties
+import javax.crypto.Cipher
+import android.security.keystore.KeyGenParameterSpec
+import androidx.annotation.RequiresApi
+import java.security.*
+
+
+class Credentials {
+
+    private val provider = "AndroidKeyStore"
+    private val aliasKeyStore = "MobiDL"
+    private val transformation = "RSA/ECB/PKCS1Padding"
+
+    @RequiresApi(Build.VERSION_CODES.M)
+    fun generateKey() {
+        val keyPairGenerator = KeyPairGenerator.getInstance(
+            KeyProperties.KEY_ALGORITHM_RSA, provider
+        )
+        keyPairGenerator.initialize(
+            KeyGenParameterSpec.Builder(
+                aliasKeyStore,
+                KeyProperties.PURPOSE_DECRYPT
+            )
+                .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_RSA_PKCS1)
+                .build()
+        )
+        keyPairGenerator.generateKeyPair()
+    }
+
+    private fun getPublicKey(): PublicKey {
+        val keyStore: KeyStore = KeyStore.getInstance(provider)
+        keyStore.load(null)
+        return keyStore.getCertificate(aliasKeyStore).publicKey
+    }
+
+    private fun getPrivateKey(): PrivateKey {
+        val keyStore: KeyStore = KeyStore.getInstance(provider)
+        keyStore.load(null)
+        return keyStore.getKey(aliasKeyStore, null) as PrivateKey
+    }
+
+    private fun encrypt(message: String): ByteArray {
+        val cipher = Cipher.getInstance(transformation)
+        cipher.init(Cipher.ENCRYPT_MODE, getPublicKey())
+
+        return cipher.doFinal(message.toByteArray())
+    }
+
+    private fun decrypt(message: ByteArray): String {
+        val cipher = Cipher.getInstance(transformation)
+        cipher.init(Cipher.DECRYPT_MODE, getPrivateKey())
+
+        val decryptedBytes = cipher.doFinal(message)
+        return decryptedBytes.decodeToString()
+    }
+}

app/src/main/java/com/mylloon/mobidl/MainActivity.kt

@@ -3,6 +3,7 @@ package com.mylloon.mobidl
 
 import android.Manifest
 import android.content.pm.PackageManager
+import android.os.Build
 import androidx.appcompat.app.AppCompatActivity
 import android.os.Bundle
 import android.widget.Button
@@ -13,22 +14,28 @@ import android.text.TextWatcher
 import android.view.MenuItem
 import android.view.Menu
 import android.widget.Toast
+import androidx.annotation.RequiresApi
 import androidx.core.content.ContextCompat
+import android.content.SharedPreferences
 
 
 class MainActivity : AppCompatActivity() {
     private var settingsButton: Menu? = null // before starting the app there is no settings button
     private var inSettings: Boolean = false // by default your not in settings page
+    var prefs: SharedPreferences? = null // first run detection
 
     private fun toggleSettingsButtonVisibility() { // Change Settings button visibility
         val visibility: Boolean = settingsButton?.findItem(R.id.settingsButton)?.isVisible == true
         settingsButton?.findItem(R.id.settingsButton)?.isVisible = !visibility
     }
 
+    @RequiresApi(Build.VERSION_CODES.O)
     override fun onCreate(savedInstanceState: Bundle?) { // Main function
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_login) // show login page
 
+        prefs = getSharedPreferences("com.mylloon.MobiDL", MODE_PRIVATE)
+
         val userInput = findViewById<EditText>(R.id.usernameInput)
         val passwordInput = findViewById<EditText>(R.id.passwordInput)
         val buttonInput = findViewById<Button>(R.id.loginButton)
@@ -58,6 +65,17 @@ class MainActivity : AppCompatActivity() {
         }
     }
 
+    @RequiresApi(Build.VERSION_CODES.M)
+    override fun onResume() {
+        super.onResume()
+        if (prefs!!.getBoolean("firstrun", true)) {
+            println("Generate RSA keys...")
+            Credentials().generateKey()
+            println("Done!")
+            prefs!!.edit().putBoolean("firstrun", false).commit() // first run done, now the next ones won't be "first".
+        }
+    }
+
     override fun onCreateOptionsMenu(menu: Menu?): Boolean { // add settings button
         menuInflater.inflate(R.menu.menu_main, menu)
         settingsButton = menu