Encrypt current user data when storing into SharedPreferences

Refs SkygearIO/features#250.

skygear/build.gradle

@@ -42,7 +42,7 @@ android {
     useLibrary 'org.apache.http.legacy'
 
     defaultConfig {
-        minSdkVersion 16
+        minSdkVersion 18
         targetSdkVersion 26
         versionCode 1
         versionName skygearVersion

skygear/src/androidTest/java/io/skygear/skygear/SecurePersistentStoreUnitTest.java

@@ -0,0 +1,115 @@
+package io.skygear.skygear;
+
+import android.annotation.SuppressLint;
+import android.content.Context;
+import android.content.SharedPreferences;
+import android.support.test.InstrumentationRegistry;
+import android.support.test.runner.AndroidJUnit4;
+
+import org.json.JSONObject;
+import org.junit.After;
+import org.junit.AfterClass;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static junit.framework.Assert.assertEquals;
+import static junit.framework.Assert.assertNotNull;
+import static junit.framework.Assert.assertNull;
+
+@RunWith(AndroidJUnit4.class)
+@SuppressLint("CommitPrefEdits")
+public class SecurePersistentStoreUnitTest {
+    static Context instrumentationContext;
+
+    private static void clearSharedPreferences(Context context) {
+        SharedPreferences pref = context.getSharedPreferences(
+                PersistentStore.SKYGEAR_PREF_SPACE,
+                Context.MODE_PRIVATE
+        );
+        SharedPreferences.Editor edit = pref.edit();
+        edit.clear();
+        edit.commit();
+    }
+
+    @BeforeClass
+    public static void setUpClass() throws Exception {
+        instrumentationContext = InstrumentationRegistry.getContext().getApplicationContext();
+        clearSharedPreferences(instrumentationContext);
+    }
+
+    @AfterClass
+    public static void tearDownClass() throws Exception {
+        clearSharedPreferences(instrumentationContext);
+        instrumentationContext = null;
+    }
+
+    @Before
+    public void setUp() throws Exception {
+        clearSharedPreferences(instrumentationContext);
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        clearSharedPreferences(instrumentationContext);
+    }
+
+    @Test
+    public void testPersistentStoreRestoreUserFromEmptyState() throws Exception {
+        SecurePersistentStore persistentStore = new SecurePersistentStore(instrumentationContext);
+        assertNull(persistentStore.currentUser);
+    }
+
+    @Test
+    public void testPersistentStoreSaveAndRestoreUser() throws Exception {
+        SecurePersistentStore persistentStore = new SecurePersistentStore(instrumentationContext);
+
+        // Save user
+        Map profile = new HashMap<>();
+        profile.put("username", "user_12345");
+        profile.put("email", "user12345@skygear.dev");
+
+        persistentStore.currentUser = new Record("user", "12345", profile);
+        persistentStore.accessToken = "token_12345";
+        persistentStore.save();
+
+        // Restore current user
+        SecurePersistentStore newPersistentStore = new SecurePersistentStore(instrumentationContext);
+        Record currentUser = newPersistentStore.currentUser;
+
+        assertEquals("user", currentUser.type);
+        assertEquals("12345", currentUser.id);
+        assertEquals("user_12345", currentUser.get("username"));
+        assertEquals("user12345@skygear.dev", currentUser.get("email"));
+
+        assertEquals("token_12345", persistentStore.accessToken);
+
+        // Current user information should be store in encrypted fields
+        SharedPreferences pref = instrumentationContext.getSharedPreferences(
+                SecurePersistentStore.SKYGEAR_PREF_SPACE,
+                Context.MODE_PRIVATE
+        );
+
+        String currentUserString = pref.getString(PersistentStore.CURRENT_USER_KEY, null);
+        String currentUserEncryptedString = pref.getString(
+                SecurePersistentStore.CURRENT_USER_ENCRYPTED_KEY, null);
+        String currentUserEncryptedKey = pref.getString(
+                SecurePersistentStore.CURRENT_USER_ENCRYPTED_KEY_KEY, null);
+        assertNull(currentUserString);
+        assertNotNull(currentUserEncryptedString);
+        assertNotNull(currentUserEncryptedKey);
+
+        String accessToken = pref.getString(PersistentStore.ACCESS_TOKEN_KEY, null);
+        String accessTokenEncrypted = pref.getString
+                (SecurePersistentStore.ACCESS_TOKEN_ENCRYPTED_KEY, null);
+        String accessTokenEncryptedKey = pref.getString(
+                SecurePersistentStore.ACCESS_TOKEN_ENCRYPTED_KEY_KEY, null);
+        assertNull(accessToken);
+        assertNotNull(accessTokenEncrypted);
+        assertNotNull(accessTokenEncryptedKey);
+    }
+}

skygear/src/main/java/io/skygear/skygear/Configuration.java

@@ -52,18 +52,27 @@ public final class Configuration {
      */
     final boolean pubsubConnectAutomatically;
 
+
+    /**
+     * Boolean indicating whether encrypt current user data saved in SharedPreferences.
+     */
+    final boolean encryptCurrentUserData;
+
+
     private Configuration(
             String endpoint,
             String apiKey,
             String gcmSenderId,
             boolean pubsubHandlerExecutionInBackground,
-            boolean pubsubConnectAutomatically
+            boolean pubsubConnectAutomatically,
+            boolean encryptCurrentUserData
     ) {
         this.endpoint = endpoint;
         this.apiKey = apiKey;
         this.gcmSenderId = gcmSenderId;
         this.pubsubHandlerExecutionInBackground = pubsubHandlerExecutionInBackground;
         this.pubsubConnectAutomatically = pubsubConnectAutomatically;
+        this.encryptCurrentUserData = encryptCurrentUserData;
     }
 
     /**
@@ -111,6 +120,15 @@ public boolean isPubsubConnectAutomatically() {
         return pubsubConnectAutomatically;
     }
 
+    /**
+     * Encrypt current user data boolean.
+     *
+     * @return the boolean
+     */
+    public boolean encryptCurrentUserData() {
+        return encryptCurrentUserData;
+    }
+
     /**
      * Creates an instance of default configuration.
      *
@@ -148,6 +166,7 @@ public static final class Builder {
         private String gcmSenderId;
         private boolean pubsubHandlerExecutionInBackground;
         private boolean pubsubConnectAutomatically;
+        private boolean encryptCurrentUserData;
 
         /**
          * Creates an instance of Builder.
@@ -212,6 +231,18 @@ public Builder pubsubConnectAutomatically(boolean automatic) {
             return this;
         }
 
+        /**
+         * Sets whether encrypt current user data saved in SharedPreferences.
+         *
+         * @param enabled the boolean indicating whether encryption Enabled
+         * automatically.
+         * @return the builder
+         */
+        public Builder encryptCurrentUserData(boolean enabled) {
+            this.encryptCurrentUserData = enabled;
+            return this;
+        }
+
         /**
          * Build a configuration.
          *
@@ -231,7 +262,8 @@ public Configuration build() {
                     this.apiKey,
                     this.gcmSenderId,
                     this.pubsubHandlerExecutionInBackground,
-                    this.pubsubConnectAutomatically
+                    this.pubsubConnectAutomatically,
+                    this.encryptCurrentUserData
             );
         }
     }

skygear/src/main/java/io/skygear/skygear/Container.java

@@ -31,7 +31,7 @@ public final class Container {
     private static final String TAG = "Skygear SDK";
     private static Container sharedInstance;
 
-    final PersistentStore persistentStore;
+    PersistentStore persistentStore;
     final Context context;
     final RequestManager requestManager;
     Configuration config;
@@ -61,18 +61,13 @@ public Container(Context context, Configuration config) {
         this.context = context.getApplicationContext();
         this.config = config;
         this.requestManager = new RequestManager(this.context, this.config);
-        this.persistentStore = new PersistentStore(this.context);
 
         this.auth = new AuthContainer(this);
         this.pubsub = new PubsubContainer(this);
         this.push = new PushContainer(this);
         this.publicDatabase = Database.Factory.publicDatabase(this);
         this.privateDatabase = Database.Factory.privateDatabase(this);
-        this.requestManager.accessToken = this.persistentStore.accessToken;
-
-        if (this.persistentStore.defaultAccessControl != null) {
-            AccessControl.defaultAccessControl = this.persistentStore.defaultAccessControl;
-        }
+        this.configPersistentStore(config);
     }
 
     /**
@@ -151,6 +146,7 @@ public void configure(Configuration config) {
         }
 
         this.config = config;
+        this.configPersistentStore(config);
         this.requestManager.configure(config);
         this.pubsub.configure(config);
     }
@@ -263,4 +259,16 @@ public final void onFailure(Error error) {
             }
         });
     }
+
+    private void configPersistentStore(Configuration config) {
+        if (config != null && config.encryptCurrentUserData) {
+            this.persistentStore = new SecurePersistentStore(this.context);
+        } else {
+            this.persistentStore = new PersistentStore(this.context);
+        }
+        this.requestManager.accessToken = this.persistentStore.accessToken;
+        if (this.persistentStore.defaultAccessControl != null) {
+            AccessControl.defaultAccessControl = this.persistentStore.defaultAccessControl;
+        }
+    }
 }

skygear/src/main/java/io/skygear/skygear/PersistentStore.java

@@ -42,7 +42,7 @@ class PersistentStore {
     static final String DEVICE_ID_KEY = "device_id";
     static final String DEVICE_TOKEN_KEY = "device_token";
 
-    private final Context context;
+    final Context context;
     /**
      * The Current user.
      */
@@ -109,7 +109,7 @@ void save() {
         prefEditor.apply();
     }
 
-    private void restoreAuthUser(SharedPreferences pref) {
+    void restoreAuthUser(SharedPreferences pref) {
         String currentUserString = pref.getString(CURRENT_USER_KEY, null);
 
         if (currentUserString == null) {
@@ -126,7 +126,7 @@ private void restoreAuthUser(SharedPreferences pref) {
         }
     }
 
-    private void saveAuthUser(SharedPreferences.Editor prefEditor) {
+    void saveAuthUser(SharedPreferences.Editor prefEditor) {
         if (this.currentUser != null) {
             prefEditor.putString(CURRENT_USER_KEY,
                     RecordSerializer.serialize(this.currentUser).toString()
@@ -136,11 +136,11 @@ private void saveAuthUser(SharedPreferences.Editor prefEditor) {
         }
     }
 
-    private void restoreAccessToken(SharedPreferences pref) {
+    void restoreAccessToken(SharedPreferences pref) {
         this.accessToken = pref.getString(ACCESS_TOKEN_KEY, null);
     }
 
-    private void saveAccessToken(SharedPreferences.Editor prefEditor) {
+    void saveAccessToken(SharedPreferences.Editor prefEditor) {
         if (this.accessToken != null) {
             prefEditor.putString(ACCESS_TOKEN_KEY, this.accessToken);
         } else {