- Added Pocket Security Functionality (still in progress...)

app/build.gradle

@@ -1,4 +1,5 @@
 apply plugin: 'com.android.application'
+apply plugin: 'kotlin-android'
 
 android {
     compileSdkVersion 27
@@ -79,4 +80,6 @@ dependencies {
     implementation 'id.zelory:compressor:2.1.0'
     implementation 'com.vincent.filepicker:MultiTypeFilePicker:1.0.7'
     implementation 'com.andrognito.patternlockview:patternlockview:1.0.0'
+    implementation 'commons-codec:commons-codec:1.11'
+
 }

app/src/main/AndroidManifest.xml

@@ -6,6 +6,7 @@
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
     <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
+    <uses-permission android:name="android.permission.NFC" />
 
     <application
         android:name=".application.CrystalApplication"
@@ -52,6 +53,21 @@
         <activity android:name=".activities.PatternRequestActivity"
             android:noHistory="true">
         </activity>
+        <activity android:name=".activities.PocketRequestActivity"
+            android:noHistory="true">
+            <!--<meta-data
+                android:name="android.nfc.action.TECH_DISCOVERED"
+                android:resource="@xml/tech" />-->
+            <intent-filter>
+                <action android:name="android.nfc.action.NDEF_DISCOVERED"/>
+                <category android:name="android.intent.category.DEFAULT"/>
+                <data
+                    android:scheme="https"
+                    android:host="my.yubico.com"
+                    android:pathPrefix="/neo"/>
+            </intent-filter>
+
+        </activity>
         <activity android:name=".activities.CryptoNetAccountSettingsActivity"
             android:theme="@style/AppTheme.NoActionBar"
             android:windowSoftInputMode="adjustPan">
@@ -60,6 +76,14 @@
             android:name=".activities.SettingsActivity"
             android:theme="@style/AppTheme.NoActionBar"
             android:windowSoftInputMode="adjustPan">
+            <intent-filter>
+                <action android:name="android.nfc.action.NDEF_DISCOVERED"/>
+                <category android:name="android.intent.category.DEFAULT"/>
+                <data
+                    android:scheme="https"
+                    android:host="my.yubico.com"
+                    android:pathPrefix="/neo"/>
+            </intent-filter>
         </activity>
         <activity
             android:name=".activities.AccountsActivity"

app/src/main/java/cy/agorise/crystalwallet/activities/IntroActivity.java

@@ -95,6 +95,7 @@ public class IntroActivity extends AppCompatActivity {
             } else {
                 //Intent intent = new Intent(this, CreateSeedActivity.class);
                 Intent intent = new Intent(this, BoardActivity.class);
+                //Intent intent = new Intent(this, PocketRequestActivity.class);
                 startActivity(intent);
             }
 

app/src/main/java/cy/agorise/crystalwallet/activities/PocketRequestActivity.java

@@ -0,0 +1,130 @@
+package cy.agorise.crystalwallet.activities;
+
+import android.app.PendingIntent;
+import android.arch.lifecycle.LiveData;
+import android.arch.lifecycle.Observer;
+import android.arch.lifecycle.ViewModelProviders;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.nfc.NfcAdapter;
+import android.nfc.Tag;
+import android.nfc.tech.IsoDep;
+import android.nfc.tech.MifareClassic;
+import android.nfc.tech.NdefFormatable;
+import android.nfc.tech.NfcA;
+import android.nfc.tech.NfcF;
+import android.nfc.tech.NfcV;
+import android.os.Bundle;
+import android.support.annotation.Nullable;
+import android.support.v7.app.AppCompatActivity;
+import android.util.Log;
+import android.widget.Toast;
+
+import com.andrognito.patternlockview.PatternLockView;
+import com.andrognito.patternlockview.listener.PatternLockViewListener;
+
+import org.apache.commons.codec.binary.Base32;
+
+import java.io.IOException;
+import java.util.List;
+
+import butterknife.BindView;
+import butterknife.ButterKnife;
+import cy.agorise.crystalwallet.R;
+import cy.agorise.crystalwallet.models.GeneralSetting;
+import cy.agorise.crystalwallet.util.PasswordManager;
+import cy.agorise.crystalwallet.util.yubikey.Algorithm;
+import cy.agorise.crystalwallet.util.yubikey.OathType;
+import cy.agorise.crystalwallet.util.yubikey.YkOathApi;
+import cy.agorise.crystalwallet.viewmodels.GeneralSettingListViewModel;
+
+public class PocketRequestActivity extends AppCompatActivity {
+
+    private NfcAdapter mNfcAdapter;
+    private PendingIntent pendingIntent;
+    private IntentFilter ndef;
+    IntentFilter[] intentFiltersArray;
+    String[][] techList;
+
+    @Override
+    public void onBackPressed() {
+        //Do nothing to prevent the user to use the back button
+    }
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_pocket_request);
+        ButterKnife.bind(this);
+
+        mNfcAdapter = NfcAdapter.getDefaultAdapter(this);
+
+        this.configureForegroundDispatch();
+    }
+
+    public void configureForegroundDispatch(){
+        if (mNfcAdapter != null) {
+            pendingIntent = PendingIntent.getActivity(
+                    this, 0, new Intent(this, getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0);
+
+            ndef = new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED);
+            try {
+                ndef.addDataType("*/*");    /* Handles all MIME based dispatches.
+                                       You should specify only the ones that you need. */
+            } catch (IntentFilter.MalformedMimeTypeException e) {
+                throw new RuntimeException("fail", e);
+            }
+            intentFiltersArray = new IntentFilter[]{ndef,};
+            techList = new String[][]{ new String[] {IsoDep.class.getName(), NfcA.class.getName(), MifareClassic.class.getName(), NdefFormatable.class.getName()} };
+
+        } else {
+            Toast.makeText(this, "This device doesn't support NFC.", Toast.LENGTH_LONG).show();
+        }
+    }
+
+    public void onPause() {
+        super.onPause();
+        if (mNfcAdapter != null) {
+            mNfcAdapter.disableForegroundDispatch(this);
+        }
+    }
+
+    public void onResume() {
+        super.onResume();
+        if (mNfcAdapter != null) {
+            mNfcAdapter.enableForegroundDispatch(this, pendingIntent, intentFiltersArray, techList);
+        }
+    }
+
+    public void onNewIntent(Intent intent) {
+        Tag tagFromIntent = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
+        IsoDep tagIsoDep = IsoDep.get(tagFromIntent);
+        Log.i("Tag from nfc","New Intent");
+        try {
+
+            String encodedSecret = "hola";
+            Base32 decoder = new Base32();
+
+            if ((encodedSecret != null) && (!encodedSecret.equals("")) && decoder.isInAlphabet(encodedSecret)) {
+                byte[] secret = decoder.decode(encodedSecret);
+                YkOathApi ykOathApi = new YkOathApi();
+                tagIsoDep.connect();
+                tagIsoDep.setTimeout(15000);
+
+                //byte[] keyBytes = {0x68,0x6f,0x6c,0x61};
+                ykOathApi.putCode(tagIsoDep,"prueba",secret, OathType.TOTP, Algorithm.SHA256,(byte)6,0,false);
+                tagIsoDep.close();
+
+                Toast.makeText(this, "Credential saved!", Toast.LENGTH_LONG).show();
+            } else {
+                Toast.makeText(this, "Invalid password for credential", Toast.LENGTH_LONG).show();
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+        Toast.makeText(this, "Tag from nfc: "+tagFromIntent, Toast.LENGTH_LONG).show();
+    }
+
+}
+
+

app/src/main/java/cy/agorise/crystalwallet/activities/SettingsActivity.java

@@ -1,5 +1,6 @@
 package cy.agorise.crystalwallet.activities;
 
+import android.content.Intent;
 import android.media.MediaPlayer;
 import android.os.Bundle;
 import android.support.v4.app.Fragment;
@@ -47,6 +48,8 @@ public class SettingsActivity extends AppCompatActivity{
     @BindView(R.id.tvBuildVersion)
     public TextView tvBuildVersion;
 
+    private SecuritySettingsFragment securitySettingsFragment;
+
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -97,7 +100,8 @@ public class SettingsActivity extends AppCompatActivity{
                 case 0:
                     return new GeneralSettingsFragment();
                 case 1:
-                    return new SecuritySettingsFragment();
+                    securitySettingsFragment = new SecuritySettingsFragment();
+                    return securitySettingsFragment;
                 case 2:
                     return new BackupsSettingsFragment();
                 //case 3:
@@ -123,4 +127,12 @@ public class SettingsActivity extends AppCompatActivity{
     public void goBack(){
         onBackPressed();
     }
+
+    @Override
+    protected void onNewIntent(Intent intent) {
+        super.onNewIntent(intent);
+        if (this.securitySettingsFragment != null){
+            this.securitySettingsFragment.onNewIntent(intent);
+        }
+    }
 }

app/src/main/java/cy/agorise/crystalwallet/application/CrystalSecurityMonitor.java

@@ -27,6 +27,7 @@ public class CrystalSecurityMonitor implements Application.ActivityLifecycleCall
     private int numStarted = 0;
     private String passwordEncrypted;
     private String patternEncrypted;
+    private String yubikeyOathTotpPasswordEncrypted;
 
     private static CrystalSecurityMonitor instance;
     private GeneralSettingListViewModel generalSettingListViewModel;
@@ -38,8 +39,10 @@ public class CrystalSecurityMonitor implements Application.ActivityLifecycleCall
 
         this.passwordEncrypted = "";
         this.patternEncrypted = "";
+        this.yubikeyOathTotpPasswordEncrypted = "";
         GeneralSetting passwordGeneralSetting = generalSettingListViewModel.getGeneralSettingByName(GeneralSetting.SETTING_PASSWORD);;
         GeneralSetting patternGeneralSetting = generalSettingListViewModel.getGeneralSettingByName(GeneralSetting.SETTING_PATTERN);;
+        GeneralSetting yubikeyOathTotpPasswordSetting = generalSettingListViewModel.getGeneralSettingByName(GeneralSetting.SETTING_YUBIKEY_OATH_TOTP_PASSWORD);;
 
         if (passwordGeneralSetting != null){
             this.passwordEncrypted = passwordGeneralSetting.getValue();
@@ -47,6 +50,9 @@ public class CrystalSecurityMonitor implements Application.ActivityLifecycleCall
         if (patternGeneralSetting != null){
             this.patternEncrypted = patternGeneralSetting.getValue();
         }
+        if (yubikeyOathTotpPasswordSetting != null){
+            this.yubikeyOathTotpPasswordEncrypted = yubikeyOathTotpPasswordSetting.getValue();
+        }
     }
 
     public static CrystalSecurityMonitor getInstance(final FragmentActivity fragmentActivity){
@@ -57,6 +63,10 @@ public class CrystalSecurityMonitor implements Application.ActivityLifecycleCall
         return instance;
     }
 
+    public static String getServiceName(){
+        return "cy.agorise.crystalwallet";
+    }
+
     public void clearSecurity(){
         this.patternEncrypted = "";
         this.passwordEncrypted = "";
@@ -65,6 +75,12 @@ public class CrystalSecurityMonitor implements Application.ActivityLifecycleCall
         generalSettingListViewModel.deleteGeneralSettingByName(GeneralSetting.SETTING_PATTERN);
     }
 
+    public void clearSecurity2ndFactor(){
+        this.yubikeyOathTotpPasswordEncrypted = "";
+
+        generalSettingListViewModel.deleteGeneralSettingByName(GeneralSetting.SETTING_YUBIKEY_OATH_TOTP_PASSWORD);
+    }
+
     public void setPasswordSecurity(String password){
         clearSecurity();
         this.passwordEncrypted = password;
@@ -95,6 +111,15 @@ public class CrystalSecurityMonitor implements Application.ActivityLifecycleCall
         return "";
     }
 
+    public void setYubikeyOathTotpSecurity(String name, String password){
+        this.yubikeyOathTotpPasswordEncrypted = password;
+        GeneralSetting yubikeyOathTotpSetting = new GeneralSetting();
+        yubikeyOathTotpSetting.setName(GeneralSetting.SETTING_YUBIKEY_OATH_TOTP_PASSWORD);
+        yubikeyOathTotpSetting.setValue(password);
+
+        generalSettingListViewModel.saveGeneralSetting(yubikeyOathTotpSetting);
+    }
+
     @Override
     public void onActivityStarted(Activity activity) {
         if (numStarted == 0) {

app/src/main/java/cy/agorise/crystalwallet/fragments/SecuritySettingsFragment.java

@@ -1,20 +1,42 @@
 package cy.agorise.crystalwallet.fragments;
 
+import android.app.PendingIntent;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.nfc.NfcAdapter;
+import android.nfc.Tag;
+import android.nfc.tech.IsoDep;
+import android.nfc.tech.MifareClassic;
+import android.nfc.tech.NdefFormatable;
+import android.nfc.tech.NfcA;
 import android.os.Bundle;
 import android.support.design.widget.TabLayout;
 import android.support.v4.app.Fragment;
 import android.support.v4.app.FragmentManager;
 import android.support.v4.app.FragmentPagerAdapter;
+import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
+import android.widget.CompoundButton;
+import android.widget.EditText;
+import android.widget.Switch;
+import android.widget.Toast;
+
+import org.apache.commons.codec.binary.Base32;
+
+import java.io.IOException;
 
 import butterknife.BindView;
 import butterknife.ButterKnife;
+import butterknife.OnCheckedChanged;
 import cy.agorise.crystalwallet.R;
 import cy.agorise.crystalwallet.application.CrystalSecurityMonitor;
 import cy.agorise.crystalwallet.models.GeneralSetting;
 import cy.agorise.crystalwallet.util.ChildViewPager;
+import cy.agorise.crystalwallet.util.yubikey.Algorithm;
+import cy.agorise.crystalwallet.util.yubikey.OathType;
+import cy.agorise.crystalwallet.util.yubikey.YkOathApi;
 
 /**
  * Created by xd on 1/17/18.
@@ -34,11 +56,23 @@ public class SecuritySettingsFragment extends Fragment {
         return fragment;
     }
 
+    private NfcAdapter mNfcAdapter;
+    private PendingIntent pendingIntent;
+    private IntentFilter ndef;
+    IntentFilter[] intentFiltersArray;
+    String[][] techList;
+
+
     @BindView(R.id.pager)
     public ChildViewPager mPager;
 
     public SecurityPagerAdapter securityPagerAdapter;
 
+    @BindView(R.id.sPocketSecurity)
+    Switch sPocketSecurity;
+    @BindView(R.id.etPocketPassword)
+    EditText etPocketPassword;
+
     @Override
     public View onCreateView(LayoutInflater inflater, ViewGroup container,
                              Bundle savedInstanceState) {
@@ -66,6 +100,9 @@ public class SecuritySettingsFragment extends Fragment {
         mPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
         tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(mPager));
 
+        mNfcAdapter = NfcAdapter.getDefaultAdapter(this.getActivity());
+        this.configureForegroundDispatch();
+
         return v;
     }
 
@@ -101,4 +138,87 @@ public class SecuritySettingsFragment extends Fragment {
             return 3;
         }
     }
+
+    @OnCheckedChanged(R.id.sPocketSecurity)
+    public void onPocketSecurityActivated(CompoundButton button, boolean checked){
+        if (checked) {
+            enableNfc();
+        } else {
+            disableNfc();
+        }
+    }
+
+    public void configureForegroundDispatch(){
+        if (mNfcAdapter != null) {
+            pendingIntent = PendingIntent.getActivity(
+                    this.getActivity(), 0, new Intent(this.getActivity(), getActivity().getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0);
+
+            ndef = new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED);
+            try {
+                ndef.addDataType("*/*");    /* Handles all MIME based dispatches.
+                                       You should specify only the ones that you need. */
+            } catch (IntentFilter.MalformedMimeTypeException e) {
+                throw new RuntimeException("fail", e);
+            }
+            intentFiltersArray = new IntentFilter[]{ndef,};
+            techList = new String[][]{ new String[] {IsoDep.class.getName(), NfcA.class.getName(), MifareClassic.class.getName(), NdefFormatable.class.getName()} };
+
+        } else {
+            Toast.makeText(this.getContext(), "This device doesn't support NFC.", Toast.LENGTH_LONG).show();
+        }
+    }
+
+    public void enableNfc(){
+        mNfcAdapter.enableForegroundDispatch(this.getActivity(), pendingIntent, intentFiltersArray, techList);
+        Toast.makeText(this.getContext(), "Tap with your yubikey", Toast.LENGTH_LONG).show();
+    }
+
+    public void disableNfc(){
+        mNfcAdapter.disableForegroundDispatch(this.getActivity());
+    }
+
+    public void onPause() {
+        super.onPause();
+        disableNfc();
+    }
+
+    public void onResume() {
+        super.onResume();
+        if (mNfcAdapter != null) {
+            enableNfc();
+        }
+    }
+
+    public void onNewIntent(Intent intent) {
+        Tag tagFromIntent = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
+        IsoDep tagIsoDep = IsoDep.get(tagFromIntent);
+        Log.i("Tag from nfc","New Intent");
+        try {
+
+            String serviceName = "cy.agorise.crystalwallet";
+            String encodedSecret = etPocketPassword.getText().toString();
+            Base32 decoder = new Base32();
+
+            if ((encodedSecret != null) && (!encodedSecret.equals("")) && decoder.isInAlphabet(encodedSecret)) {
+                byte[] secret = decoder.decode(encodedSecret);
+                YkOathApi ykOathApi = new YkOathApi();
+                tagIsoDep.connect();
+                tagIsoDep.setTimeout(15000);
+
+                try {
+                    ykOathApi.putCode(tagIsoDep, serviceName, secret, OathType.TOTP, Algorithm.SHA256, (byte) 6, 0, false);
+                    CrystalSecurityMonitor.getInstance(null).setYubikeyOathTotpSecurity(CrystalSecurityMonitor.getServiceName(),encodedSecret);
+                } catch(IOException e) {
+                    Toast.makeText(this.getContext(), "There's no space for new credentials!", Toast.LENGTH_LONG).show();
+                }
+
+                tagIsoDep.close();
+                Toast.makeText(this.getContext(), "Credential saved!", Toast.LENGTH_LONG).show();
+            } else {
+                Toast.makeText(this.getContext(), "Invalid password for credential", Toast.LENGTH_LONG).show();
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
 }

app/src/main/java/cy/agorise/crystalwallet/models/GeneralSetting.java

@@ -23,6 +23,8 @@ public class GeneralSetting {
     public final static String SETTING_PATTERN = "PATTERN";
     public final static String SETTING_NAME_RECEIVED_FUNDS_SOUND_PATH = "RECEIVED_FUNDS_SOUND_PATH";
     public final static String SETTING_LAST_LICENSE_READ = "LAST_LICENSE_READ";
+    public final static String SETTING_YUBIKEY_OATH_TOTP_NAME = "YUBIKEY_OATH_TOTP_NAME";
+    public final static String SETTING_YUBIKEY_OATH_TOTP_PASSWORD = "YUBIKEY_OATH_TOTP_PASSWORD";
 
     /**
      * The id on the database

app/src/main/java/cy/agorise/crystalwallet/util/yubikey/Algorithm.java

@@ -0,0 +1,58 @@
+package cy.agorise.crystalwallet.util.yubikey;
+
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.Arrays;
+
+import kotlin.jvm.internal.Intrinsics;
+
+public enum Algorithm {
+    SHA1((byte)1, "SHA1", 64),
+    SHA256((byte)2, "SHA256", 64),
+    SHA512((byte)3, "SHA512", 128);
+
+    protected Byte byteVal;
+    protected String name;
+    protected int blockSize;
+    protected MessageDigest messageDigest;
+
+    Algorithm(Byte byteVal, String name, int blockSize){
+        this.byteVal = byteVal;
+        this.name = name;
+        this.blockSize = blockSize;
+
+        try {
+            this.messageDigest = MessageDigest.getInstance(name);
+        } catch (NoSuchAlgorithmException e){
+            this.messageDigest = null;
+        }
+    }
+
+    public Byte getByteVal(){
+        return this.byteVal;
+    }
+
+    public String getName(){
+        return this.name;
+    }
+
+    public int getBlockSize() {
+        return this.blockSize;
+    }
+
+    public byte[] prepareKey(byte[] key){
+        int keyLength = key.length;
+        byte[] keyPrepared;
+        if ((0 <= keyLength) && (keyLength <= 13)) {
+            keyPrepared = Arrays.copyOf(key, 14);
+            return keyPrepared;
+        }
+        if ((14 <= keyLength) && (keyLength <= this.blockSize)){
+            keyPrepared = key;
+            return keyPrepared;
+        }
+
+        keyPrepared = this.messageDigest.digest(key);
+        return keyPrepared;
+    }
+}

app/src/main/java/cy/agorise/crystalwallet/util/yubikey/OathType.java

@@ -0,0 +1,16 @@
+package cy.agorise.crystalwallet.util.yubikey;
+
+public enum OathType {
+    HOTP((byte)0x10),
+    TOTP((byte)0x20);
+
+    protected Byte byteVal;
+
+    OathType(Byte byteVal){
+        this.byteVal = byteVal;
+    }
+
+    public Byte getByteVal(){
+        return this.byteVal;
+    }
+}

app/src/main/res/layout/activity_pocket_request.xml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical">
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_weight="1"
+        android:gravity="center"
+        android:padding="5dp"
+        android:background="@color/colorPrimary">
+        <TextView
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="Please tap pocket!"/>
+    </LinearLayout>
+</LinearLayout>

app/src/main/res/layout/fragment_security_settings.xml

@@ -68,7 +68,7 @@
         android:layout_width="match_parent"
         android:layout_height="140dp"
         android:background="@color/lightGray"
-        android:visibility="gone"
+        android:visibility="visible"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent" />
@@ -102,15 +102,14 @@
         android:text="@string/user_name_password_placeholder"
         app:layout_constraintTop_toBottomOf="@id/tvPocketSecurity"
         app:layout_constraintStart_toStartOf="@id/tvPocketSecurity"/>
-    
+
     <EditText
         android:id="@+id/etPocketPassword"
         android:layout_width="0dp"
         android:layout_height="wrap_content"
-        android:inputType="numberPassword"
-        app:layout_constraintTop_toBottomOf="@id/tvPocketSecurityUser"
-        app:layout_constraintStart_toStartOf="@id/tvPocketSecurity"
         app:layout_constraintEnd_toEndOf="@id/sPocketSecurity"
+        app:layout_constraintStart_toStartOf="@id/tvPocketSecurity"
+        app:layout_constraintTop_toBottomOf="@id/tvPocketSecurityUser"
         tools:ignore="LabelFor" />
 
 </android.support.constraint.ConstraintLayout>

app/src/main/res/xml/tech.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources xmlns:xliff="urn:oasis:names:tc:xliff:document:1.2">
+    <tech-list>
+        <tech>android.nfc.tech.MifareUltralight</tech>
+        <tech>android.nfc.tech.Ndef</tech>
+        <tech>android.nfc.tech.NfcA</tech>
+    </tech-list>
+    <tech-list>
+        <tech>android.nfc.tech.MifareClassic</tech>
+        <tech>android.nfc.tech.Ndef</tech>
+        <tech>android.nfc.tech.NfcA</tech>
+    </tech-list>
+</resources>

build.gradle

@@ -5,9 +5,11 @@ buildscript {
         jcenter()
         google()
     }
+    ext.kotlin_version = '1.2.51'
     dependencies {
         classpath 'com.android.tools.build:gradle:3.1.3'
         classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8'
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files
     }