TestKeyStore.java

/*
 * Copyright 2020 The Android Open Source Project
 *
 * 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.
 */

//packgage com.company.app

import android.content.Context;
import android.content.SharedPreferences;
import android.security.keystore.KeyGenParameterSpec;
import android.util.Log;

import androidx.annotation.NonNull;
import androidx.security.crypto.MasterKeys;
import androidx.security.crypto.EncryptedSharedPreferences;

import java.io.IOException;
import java.security.GeneralSecurityException;

/**
 * Convenient method to test the Android Keystore before using encryption/decryption. A small number
 * OEMs have devices with a bad keystore and KeyStore exceptions will occur.
 *
 * Requires Jetpack Security - https://developer.android.com/jetpack/androidx/releases/security
 *
 * Bugs:
 *
 * https://issuetracker.google.com/issues/147480931
 * https://issuetracker.google.com/issues/134417365
 * https://issuetracker.google.com/issues/150221071
 *
 */
public final class TestKeyStore {

     /**
     * Test the keystore, encryption and decryption on the device. This is useful to find devices
     * that have a bad keystore and encryption should not be used. It is up to the developer to
     * decide how to handle when a bad keystore is encountered. We recommend that the device be
     * trusted less by your app if possible.
     *
     * @param keyGenParameterSpec The key encryption scheme
     * @return true if the keystore can be relied on, false otherwise
     */
    public static boolean trustDeviceKeyStore(@NonNull KeyGenParameterSpec keyGenParameterSpec,
            @NonNull Context context) {
        try {
            String keyAlias = MasterKeys.getOrCreate(keyGenParameterSpec);
            SharedPreferences sharedPreferences =
                    EncryptedSharedPreferences.create("test_keystore", keyAlias,
                            context,
                            EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
                            EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM);
            SharedPreferences.Editor editor = sharedPreferences.edit();
            editor.putString("TestKeyStore", "Testing");
            editor.commit();
            String value = sharedPreferences.getString("TestKeyStore", "Failed");
            if (value.equals("Testing")) {
                return true;
            }
        } catch (GeneralSecurityException ex) {
            Log.e(TestKeyStore.class.getSimpleName(),
                    "SecurityException: Could be a keystore issue, check the error for more "
                            + "details message: " + ex.getMessage() + ".\n Stacktrace:\n"
                            + ex.getStackTrace().toString());
        } catch (IOException ex) {
            Log.e(TestKeyStore.class.getSimpleName(),
                    "IOException: Check to make sure you have enough disk space and that the "
                            + "file doesn't exist." + ex.getMessage());
        }
        return false;
    }

}