[MOBL-1776] Improved security by replacing SharedPreferences with Enc…

…ryptedSharedPreferences to store UserInfo (#357)

* [MOBL-1811] Gradle = 8.6, AGP = 8.4.0, Kotlin = 1.9.23, targetSdkVersion = 34

* Reverting an unwanted version change

* first draft of encrypted shared pref implementation is ready

* Added tests for the get and save methods

* Added code for migration when needed.

* Added test cases to make sure the new preference is backward compatible

* Deprecated the clear(context) method

* Added additional test case

* Added configuration variable to opt in for encryption feature

android-sdk/build.gradle

@@ -12,7 +12,7 @@ android {
     compileSdk 34
 
     defaultConfig {
-        minSdkVersion 16
+        minSdkVersion 23
         targetSdkVersion 34
         multiDexEnabled true
 
@@ -53,6 +53,7 @@ dependencies {
     implementation 'androidx.swiperefreshlayout:swiperefreshlayout:1.2.0-alpha01'
 
     implementation 'com.google.code.gson:gson:2.8.9'
+    implementation 'androidx.security:security-crypto:1.0.0'
 
     // Firebase
     implementation 'com.google.firebase:firebase-core:17.4.4'

android-sdk/src/androidTest/java/com/blueshift/BlueshiftEncryptedPreferencesTest.kt

@@ -0,0 +1,41 @@
+package com.blueshift
+
+import androidx.test.platform.app.InstrumentationRegistry
+import org.junit.Before
+import org.junit.Test
+
+class BlueshiftEncryptedPreferencesTest {
+    @Before
+    fun setUp() {
+        val context = InstrumentationRegistry.getInstrumentation().targetContext
+        BlueshiftEncryptedPreferences.init(context)
+    }
+
+    @Test
+    fun savedValueIsReturnedWhenCorrectKeyIsProvided() {
+        BlueshiftEncryptedPreferences.putString(key = "key", value = "value")
+        val result = BlueshiftEncryptedPreferences.getString(key = "key", null)
+        assert(result == "value")
+    }
+
+    @Test
+    fun defaultValueIsReturnedWhenIncorrectKeyIsProvided() {
+        BlueshiftEncryptedPreferences.putString(key = "key", value = "value")
+        val result = BlueshiftEncryptedPreferences.getString(key = "wrong_key", "default")
+        assert(result == "default")
+    }
+
+    @Test
+    fun storedValueIsRemovedWhenCallingRemoveMethod() {
+        BlueshiftEncryptedPreferences.putString(key = "key", value = "value")
+
+        val result1 = BlueshiftEncryptedPreferences.getString(key = "key", null)
+        assert(result1 == "value")
+
+        BlueshiftEncryptedPreferences.remove(key = "key")
+
+        val result2 = BlueshiftEncryptedPreferences.getString(key = "key", null)
+        assert(result2 == null)
+    }
+
+}

android-sdk/src/androidTest/java/com/blueshift/model/UserInfoTest.kt

@@ -0,0 +1,106 @@
+package com.blueshift.model
+
+import android.content.Context
+import android.content.SharedPreferences
+import androidx.test.platform.app.InstrumentationRegistry
+import com.blueshift.BlueshiftEncryptedPreferences
+import org.junit.Before
+import org.junit.Test
+
+class UserInfoTest {
+    private lateinit var context: Context
+    private lateinit var legacyPreference: SharedPreferences
+
+    private fun oldPreferenceFile(context: Context): String {
+        return context.packageName + ".user_info_file"
+    }
+
+    private fun oldPreferenceKey(context: Context): String {
+        return context.packageName + ".user_info_key"
+    }
+
+    @Before
+    fun setUp() {
+        context = InstrumentationRegistry.getInstrumentation().targetContext
+
+        // Reset old preferences
+        legacyPreference = context.getSharedPreferences(
+            oldPreferenceFile(context), Context.MODE_PRIVATE
+        )
+        legacyPreference.edit().remove(oldPreferenceKey(context)).commit()
+
+        // Reset new preferences
+        BlueshiftEncryptedPreferences.init(context)
+        BlueshiftEncryptedPreferences.remove(PREF_KEY)
+    }
+
+    @Test
+    fun load_newInstall_returnEmptyUserInfoObject() {
+        // For a fresh installation, the shared preferences will not contain any data.
+        // So, the user info class should provide an instance without any value for its members.
+        val user = UserInfo.getInstance(context)
+        assert(user.name == null)
+    }
+
+    @Test
+    fun load_updatedFromOldSDK_returnSameUserInfoObject() {
+        // Mock the presence of a user object in the old preference.
+        legacyPreference.edit().putString(oldPreferenceKey(context), USER_JSON).apply()
+
+        // When encryption is not enabled, the user info class should provide the same value
+        // for its members as we saved in the old preference.
+        val userinfo = UserInfo.load(context, false)
+        assert(userinfo.name == JOHN)
+
+        // When encryption is not enabled, the user info class should provide the same value
+        // for its members as we saved in the old preference.
+        val userinfo2 = UserInfo.load(context, true)
+        assert(userinfo2.name == JOHN)
+
+        // Kill the existing instance for the next test.
+        UserInfo.killInstance()
+    }
+
+    @Test
+    fun load_updatedFromOldSDK_copiesTheContentOfOldPrefToNewPref() {
+        // Mock the presence of a user object in the old preference.
+        legacyPreference.edit().putString(oldPreferenceKey(context), USER_JSON).apply()
+
+        // case1 : When encryption is not enabled.
+        val userInfo = UserInfo.load(context, false)
+        assert(userInfo.name == JOHN)
+
+        // case2 : When encryption is enabled.
+        UserInfo.load(context, true)
+        val json = BlueshiftEncryptedPreferences.getString(PREF_KEY, null)
+        assert(USER_JSON == json)
+
+        // Kill the existing instance for the next test.
+        UserInfo.killInstance()
+    }
+
+    @Test
+    fun load_updatedFromOldSDK_deletesTheDataInOldPreference() {
+        // Mock the presence of a user object in the old preference.
+        legacyPreference.edit().putString(oldPreferenceKey(context), USER_JSON).apply()
+
+        // case1 : When encryption is not enabled.
+        val userInfo = UserInfo.load(context, false)
+        assert(userInfo.name == JOHN)
+
+        // case2 : When encryption is enabled.
+        UserInfo.load(context, true)
+        // Make sure the value stored in the old preferences is removed after copying it to the new preferences.
+        val legacyJson = legacyPreference.getString(oldPreferenceKey(context), null)
+        assert(legacyJson == null)
+
+        // Kill the existing instance for the next test.
+        UserInfo.killInstance()
+    }
+
+    companion object {
+        const val JOHN = "John"
+        const val PREF_KEY = "user_info"
+        const val USER_JSON = "{\"joined_at\":0,\"name\":\"$JOHN\",\"unsubscribed\":false}"
+    }
+}

android-sdk/src/main/java/com/blueshift/Blueshift.java

@@ -354,6 +354,8 @@ public void getLiveContentByCustomerId(@NonNull String slot, HashMap<String, Obj
     public void initialize(@NonNull Configuration configuration) {
         mConfiguration = configuration;
 
+        BlueshiftEncryptedPreferences.INSTANCE.init(mContext);
+
         BlueshiftAttributesApp.getInstance().init(mContext);
         doAppVersionChecks(mContext);
 

android-sdk/src/main/java/com/blueshift/BlueshiftEncryptedPreferences.kt

@@ -0,0 +1,44 @@
+package com.blueshift
+
+import android.content.Context
+import android.content.SharedPreferences
+import androidx.security.crypto.EncryptedSharedPreferences
+import androidx.security.crypto.MasterKeys
+
+object BlueshiftEncryptedPreferences {
+    private val PREF_NAME = "blueshift_sdk_preferences"
+
+    private lateinit var sharedPreferences: SharedPreferences
+
+    fun init(context: Context) {
+        val masterKey = MasterKeys.getOrCreate(MasterKeys.AES256_GCM_SPEC)
+
+        sharedPreferences = EncryptedSharedPreferences.create(
+            PREF_NAME,
+            masterKey,
+            context,
+            EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
+            EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
+        )
+    }
+
+    fun remove(key: String) {
+        if (::sharedPreferences.isInitialized) {
+            sharedPreferences.edit().remove(key).apply()
+        }
+    }
+
+    fun putString(key: String, value: String?) {
+        if (::sharedPreferences.isInitialized) {
+            sharedPreferences.edit().putString(key, value).apply()
+        }
+    }
+
+    fun getString(key: String, defaultValue: String?): String? {
+        return if (::sharedPreferences.isInitialized) {
+            sharedPreferences.getString(key, defaultValue)
+        } else {
+            defaultValue
+        }
+    }
+}

android-sdk/src/main/java/com/blueshift/model/Configuration.java

@@ -58,6 +58,10 @@ public class Configuration {
     private Blueshift.DeviceIdSource deviceIdSource;
     private String customDeviceId;
 
+    // Defines is we should store user info in plain text or in encrypted form.
+    // Default value is false to make it backward compatible.
+    private  boolean shouldEncryptUserInfo = false;
+
     public Configuration() {
         // Setting default region to the US.
         region = BlueshiftRegion.US;
@@ -94,6 +98,14 @@ public Configuration() {
         autoAppOpenInterval = 86400;
     }
 
+    public boolean shouldEncryptUserInfo() {
+        return shouldEncryptUserInfo;
+    }
+
+    public void setShouldEncryptUserInfo(boolean shouldEncryptUserInfo) {
+        this.shouldEncryptUserInfo = shouldEncryptUserInfo;
+    }
+
     public boolean isPushAppLinksEnabled() {
         return pushAppLinksEnabled;
     }

android-sdk/src/main/java/com/blueshift/model/UserInfo.java

@@ -1,9 +1,14 @@
 package com.blueshift.model;
 
 import android.content.Context;
+import android.content.SharedPreferences;
+
+import androidx.annotation.NonNull;
 
 import com.blueshift.BlueshiftConstants;
+import com.blueshift.BlueshiftEncryptedPreferences;
 import com.blueshift.BlueshiftLogger;
+import com.blueshift.util.BlueshiftUtils;
 import com.google.gson.Gson;
 import com.google.gson.JsonSyntaxException;
 
@@ -23,6 +28,7 @@ public class UserInfo {
     private static final String TAG = "UserInfo";
     private static final String PREF_FILE = "user_info_file";
     private static final String PREF_KEY = "user_info_key";
+    private static final String PREF_KEY_ENCRYPTED = "user_info";
     private static final Boolean lock = false;
 
     private String email;
@@ -49,6 +55,10 @@ private UserInfo() {
         unsubscribed = false;
     }
 
+    static void killInstance() {
+        instance = null;
+    }
+
     public static UserInfo getInstance(Context context) {
         synchronized (lock) {
             if (instance == null) {
@@ -60,18 +70,29 @@ public static UserInfo getInstance(Context context) {
         }
     }
 
-    private static String getPrefFile(Context context) {
+    private static String getLegacyPreferenceFile(@NonNull Context context) {
         return context.getPackageName() + "." + PREF_FILE;
     }
 
-    private static String getPrefKey(Context context) {
+    private static String getLegacyPreferenceKey(@NonNull Context context) {
         return context.getPackageName() + "." + PREF_KEY;
     }
 
-    private static UserInfo load(Context context) {
+    private static UserInfo load(@NonNull Context context) {
+        Configuration configuration = BlueshiftUtils.getConfiguration(context);
+        boolean isEncryptionEnabled = configuration != null && configuration.shouldEncryptUserInfo();
+        return load(context, isEncryptionEnabled);
+    }
+
+    static UserInfo load(Context context, boolean encryptionEnabled) {
+        return encryptionEnabled ? loadEncrypted(context) : loadLegacy(context);
+    }
+
+    private static UserInfo loadLegacy(@NonNull Context context) {
         UserInfo userInfo = null;
-        String json = context.getSharedPreferences(getPrefFile(context), Context.MODE_PRIVATE)
-                .getString(getPrefKey(context), null);
+
+        SharedPreferences preferences = context.getSharedPreferences(getLegacyPreferenceFile(context), Context.MODE_PRIVATE);
+        String json = preferences.getString(getLegacyPreferenceKey(context), null);
         if (json != null) {
             try {
                 userInfo = new Gson().fromJson(json, UserInfo.class);
@@ -83,6 +104,38 @@ private static UserInfo load(Context context) {
         return userInfo;
     }
 
+    private static UserInfo loadEncrypted(@NonNull Context context) {
+        UserInfo userInfo = null;
+
+        String json = BlueshiftEncryptedPreferences.INSTANCE.getString(PREF_KEY_ENCRYPTED, null);
+        if (json == null) {
+            // The new secure store doesn't have the user info. Let's check in the old preference
+            // file and copy over the data if present.
+            SharedPreferences pref = context.getSharedPreferences(getLegacyPreferenceFile(context), Context.MODE_PRIVATE);
+            String legacyJson = pref.getString(getLegacyPreferenceKey(context), null);
+            if (legacyJson != null) {
+                try {
+                    userInfo = new Gson().fromJson(legacyJson, UserInfo.class);
+                    // Save it to secure store for loading next time.
+                    userInfo.saveEncrypted();
+                    // Clear the old preference for privacy reasons.
+                    pref.edit().clear().apply();
+                } catch (Exception e) {
+                    BlueshiftLogger.e(TAG, e);
+                }
+            }
+        } else {
+            // The new secure store has the user info. Let's load it.
+            try {
+                userInfo = new Gson().fromJson(json, UserInfo.class);
+            } catch (Exception e) {
+                BlueshiftLogger.e(TAG, e);
+            }
+        }
+
+        return userInfo;
+    }
+
     public HashMap<String, Object> toHashMap() {
         HashMap<String, Object> map = new HashMap<>();
         map.put(BlueshiftConstants.KEY_CUSTOMER_ID, getRetailerCustomerId());
@@ -116,11 +169,29 @@ public HashMap<String, Object> toHashMap() {
         return map;
     }
 
-    public void save(Context context) {
-        context.getSharedPreferences(getPrefFile(context), Context.MODE_PRIVATE)
-                .edit()
-                .putString(getPrefKey(context), new Gson().toJson(this))
-                .apply();
+    public void save(@NonNull Context context) {
+        Configuration configuration = BlueshiftUtils.getConfiguration(context);
+        boolean isEncryptionEnabled = configuration != null && configuration.shouldEncryptUserInfo();
+        save(context, isEncryptionEnabled);
+    }
+
+    void save(Context context, boolean encryptionEnabled) {
+        if (encryptionEnabled) {
+            saveEncrypted();
+        } else {
+            saveLegacy(context);
+        }
+    }
+
+    private void saveLegacy(Context context) {
+        String json = new Gson().toJson(this);
+        context.getSharedPreferences(getLegacyPreferenceFile(context), Context.MODE_PRIVATE)
+                .edit().putString(getLegacyPreferenceKey(context), json).apply();
+    }
+
+    private void saveEncrypted() {
+        String json = new Gson().toJson(this);
+        BlueshiftEncryptedPreferences.INSTANCE.putString(PREF_KEY_ENCRYPTED, json);
     }
 
     public String getEmail() {