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202 changes: 202 additions & 0 deletions LICENSE.txt
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57 changes: 57 additions & 0 deletions README.md
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For securing your `SharedPreferences` information.

## Why Secure `SharedPreferences`?
`SharedPreferences` are accessible to anybody if your device is compromised. It is recommended to obscure the information saved in `SharedPreferences` before you store them (See [`ObscuredSharedPreferences`] (library/src/main/java/in/co/ophio/secure/core/ObscuredSharedPreferences.java)). Still the `key` that is used to obscure the information can be recovered by a simple decompilation procedure if it is hard-coded in the app.

## Solution
In addition to obscuring the information stored in `SharedPreferences,` store your key in the [`Android Keystore System`] (https://developer.android.com/training/articles/keystore.html#UsingAndroidKeyStore) by using our [`KeyGenerator`](library/src/main/java/in/co/ophio/secure/core/KeyStoreKeyGenerator.java)

## Android Keystore System
The Android Keystore system lets you store private keys in a container to make it more difficult to extract from the device. Once keys are in the keystore, they can be used for cryptographic operations with the private key material remaining non-exportable.

The Keystore system is used by the [`KeyChain`](https://developer.android.com/reference/android/security/KeyChain.html) API as well as the Android Keystore provider feature that was introduced in Android 4.3 (API level 18).

#Usage

* Generate a key using [`KeyGenerator`](library/src/main/java/in/co/ophio/secure/core/KeyStoreKeyGenerator.java):

```
String key = KeyGenerator.get(KeystoreApplication.getAppContext(),
KeystoreApplication.getAppContext().getPackageName())
.loadOrGenerateKeys();
```

* Obtain an instance of [`ObscuredSharedPreferences`] (library/src/main/java/in/co/ophio/secure/core/ObscuredSharedPreferences.java) using [`ObscuredPreferencesBuilder`](library/src/main/java/in/co/ophio/secure/core/ObscuredPreferencesBuilder.java) as follows:

```
SharedPreferences sharedPreferences = new ObscuredPreferencesBuilder()
.setApplication(KeystoreApplication.getAppContext())
.obfuscateValue(true)
.obfuscateKey(true)
.setSharePrefFileName(PREFS_NAME)
.setSecret(key) //secret key we generated in step 1.
.createSharedPrefs();
```

* For more information on usage see the sample application [implementation](app/src/main/java/in/co/ophio/keystore_preferences/util/KeystoreAccountUtils.java):
* For more information on library see the [library page](library/).



# License

```
Copyright 2015 Ophio.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
```
15 changes: 15 additions & 0 deletions app/src/main/java/in/co/ophio/keystore_preferences/view/MainFragment.java
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import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import org.w3c.dom.Text;

import javax.inject.Inject;

import butterknife.InjectView;
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import butterknife.ButterKnife;
import in.co.ophio.keystore_preferences.entity.UserCredential;
import in.co.ophio.keystore_preferences.util.AccountUtils;
import in.co.ophio.secure.core.KeyGenerator;

/**
* @author ragdroid (garima.my.way@gmail.com)
*/
public class MainFragment extends Fragment {

@Inject AccountUtils accountUtils;
@Inject KeyGenerator keyGenerator;
@InjectView(R.id.user_name) EditText userName;
@InjectView(R.id.password) EditText password;
@InjectView(R.id.hardware_backed) TextView hardwareBack;
private MainFragmentListener fragmentListener;

public static MainFragment getInstance() {
Expand Down Expand Up @@ -59,9 +65,18 @@ public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle sa
View view = inflater.inflate(R.layout.fragment_main, container, false);
ButterKnife.inject(this, view);
KeystoreApplication.getAppContext().getAppComponent().inject(this);
setUpView();
return view;
}

private void setUpView() {
if (keyGenerator.isHardwareBacked()) {
hardwareBack.setText("Keystore is hardware-backed.");
} else {
hardwareBack.setText("This device has software keystore which is more vulnerable to offline attacks if the device is compromised.");
}
}

@OnClick(R.id.login_button)
public void onLoginButtonClicked() {
if (isEntryValid()) {
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8 changes: 7 additions & 1 deletion app/src/main/res/layout/fragment_main.xml
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android:orientation="vertical"
android:paddingLeft="@dimen/keyline_1"
android:paddingRight="@dimen/keyline_1">

<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
Expand All @@ -23,6 +22,13 @@
android:textStyle="bold"
android:text="@string/login"
/>
<TextView
android:id="@+id/hardware_backed"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:padding="@dimen/space"
/>

<EditText
android:id="@+id/user_name"
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2 changes: 1 addition & 1 deletion app/src/main/res/values/dimens.xml
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<dimen name="space_medium">16dp</dimen>
<dimen name="space_large">24dp</dimen>
<dimen name="space_xlarge">40dp</dimen>
<dimen name="login_heading_text_size">16sp</dimen>
<dimen name="login_heading_text_size">18sp</dimen>

</resources>
40 changes: 40 additions & 0 deletions library/README.md
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This library contains the following:

* [`ObscuredSharedPreferences`] (src/main/java/in/co/ophio/secure/core/ObscuredSharedPreferences.java): An implementation of `SharedPreferences` that can store keys and values in obscured manner.
* [`ObscuredPreferencesBuilder`] (src/main/java/in/co/ophio/secure/core/ObscuredPreferencesBuilder.java): Can be used to obtain an instance of `ObscuredSharedPreferences`.
* [`KeyStoreKeyGenerator`] (src/main/java/in/co/ophio/secure/core/KeyStoreKeyGenerator.java): used to generate keys using `Android Keystore System`


## [`ObscuredSharedPreferences`] (src/main/java/in/co/ophio/secure/core/ObscuredSharedPreferences.java)

* Main idea by Mike Burton in an answer posted [here](http://stackoverflow.com/questions/785973/what-is-the-most-appropriate-way-to-store-user-settings-in-android-application).
* It is mandatory to set key using `setSecret()` method otherwise `IllegalAccessException` will be thrown.
* Uses `PBEWithMD5AndDES` to encode the keys and/or values.
* Overrides methods like `putBoolean(), putFloat(), getBoolean(), getFloat(), contains(),` ` getAll(),` ... to provide an obscured implementation.

## [`ObscuredPreferencesBuilder`] (library/src/main/java/in/co/ophio/secure/core/ObscuredPreferencesBuilder.java)

* Will return an instance of `ObscuredPreferencesBuilder` if atleast one of the `obfuscateKey()` OR `obfuscateValue()` is set.
* If none of the above methods are set it will return simple `SharedPreferences` implementation.
* Example:

```
SharedPreferences sharedPreferences = new ObscuredPreferencesBuilder()
.setApplication(KeystoreApplication.getAppContext())
.obfuscateValue(true)
.obfuscateKey(true)
.setSharePrefFileName(PREFS_NAME)
.setSecret("some key")
.createSharedPrefs();
```

## [`KeyStoreKeyGenerator`] (src/main/java/in/co/ophio/secure/core/KeyStoreKeyGenerator.java)
* method `loadOrGenerateKeys()`: Subsequent calls of same method in an application returns the same key. Uses `Android Keystore System` to generate and return key. It throws `IllegalStateException` if some error occurred while trying to generate keys.
* method `isHardwareBacked()`: Flag indicating that the `SecretKeyWrapper` public/private key is hardware-backed. A software keystore is more vulnerable to offline attacks if the device is compromised.
* Example:

```
String key = KeyGenerator.get(KeystoreApplication.getAppContext(),
KeystoreApplication.getAppContext().getPackageName())
.loadOrGenerateKeys();
```

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