OWASP 类别： MASVS-CRYPTO: 加密
概述
开发人员使用加密来保护数据的机密性和完整性，方法是使用强大的算法。但是，密钥存储往往未得到充分利用，并且通常会发现它们以字符串或字节数组的形式硬编码到应用程序代码中，或者硬编码到资产文件中，例如 strings.xml。如果密钥在应用的任何文件中公开，这将违反 Kerchoff 原则，安全模型将被视为已损坏。
影响
攻击者可以使用逆向工程工具轻松地检索硬编码的密钥。根据条件，影响可能会有所不同，但在许多情况下，会导致重大安全问题，例如访问敏感数据。
缓解措施
要缓解此问题，请考虑使用 KeyChain API（当您需要系统范围的凭据时）或 Android Keystore 提供程序（使单个应用能够存储只有该应用本身可以访问的凭据）。
以下代码片段展示了如何使用 KeyStore 存储和使用对称密钥
Kotlin
private val ANDROID_KEY_STORE_PROVIDER = "AndroidKeyStore"
private val ANDROID_KEY_STORE_ALIAS = "AES_KEY_DEMO"
@Throws(
KeyStoreException::class,
NoSuchAlgorithmException::class,
NoSuchProviderException::class,
InvalidAlgorithmParameterException::class
)
private fun createAndStoreSecretKey() {
val builder: KeyGenParameterSpec.Builder = KeyGenParameterSpec.Builder(
ANDROID_KEY_STORE_ALIAS,
KeyProperties.PURPOSE_ENCRYPT or KeyProperties.PURPOSE_DECRYPT
)
val keySpec: KeyGenParameterSpec = builder
.setKeySize(256)
.setBlockModes(KeyProperties.BLOCK_MODE_GCM)
.setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)
.setRandomizedEncryptionRequired(true)
.build()
val aesKeyGenerator: KeyGenerator =
KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES, ANDROID_KEY_STORE_PROVIDER)
aesKeyGenerator.init(keySpec)
val key: SecretKey = aesKeyGenerator.generateKey()
}
@Throws(
KeyStoreException::class,
UnrecoverableEntryException::class,
NoSuchAlgorithmException::class,
CertificateException::class,
IOException::class,
NoSuchPaddingException::class,
InvalidKeyException::class,
IllegalBlockSizeException::class,
BadPaddingException::class
)
private fun encryptWithKeyStore(plainText: String): ByteArray? {
// Initialize KeyStore
val keyStore: KeyStore = KeyStore.getInstance(ANDROID_KEY_STORE_PROVIDER)
keyStore.load(null)
// Retrieve the key with alias androidKeyStoreAlias created before
val keyEntry: KeyStore.SecretKeyEntry =
keyStore.getEntry(ANDROID_KEY_STORE_ALIAS, null) as KeyStore.SecretKeyEntry
val key: SecretKey = keyEntry.secretKey
// Use the secret key at your convenience
val cipher: Cipher = Cipher.getInstance("AES/GCM/NoPadding")
cipher.init(Cipher.ENCRYPT_MODE, key)
return cipher.doFinal(plainText.toByteArray())
}
Java
static private final String ANDROID_KEY_STORE_PROVIDER = "AndroidKeyStore";
static private final String ANDROID_KEY_STORE_ALIAS = "AES_KEY_DEMO";
private void createAndStoreSecretKey() throws KeyStoreException, NoSuchAlgorithmException, NoSuchProviderException, InvalidAlgorithmParameterException {
KeyGenParameterSpec.Builder builder = new KeyGenParameterSpec.Builder(
ANDROID_KEY_STORE_ALIAS,
KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT);
KeyGenParameterSpec keySpec = builder
.setKeySize(256)
.setBlockModes(KeyProperties.BLOCK_MODE_GCM)
.setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)
.setRandomizedEncryptionRequired(true)
.build();
KeyGenerator aesKeyGenerator = KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES, ANDROID_KEY_STORE_PROVIDER);
aesKeyGenerator.init(keySpec);
SecretKey key = aesKeyGenerator.generateKey();
}
private byte[] encryptWithKeyStore(final String plainText) throws KeyStoreException, UnrecoverableEntryException, NoSuchAlgorithmException, CertificateException, IOException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
// Initialize KeyStore
KeyStore keyStore = KeyStore.getInstance(ANDROID_KEY_STORE_PROVIDER);
keyStore.load(null);
// Retrieve the key with alias ANDROID_KEY_STORE_ALIAS created before
KeyStore.SecretKeyEntry keyEntry = (KeyStore.SecretKeyEntry) keyStore.getEntry(ANDROID_KEY_STORE_ALIAS, null);
SecretKey key = keyEntry.getSecretKey();
// Use the secret key at your convenience
final Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
cipher.init(Cipher.ENCRYPT_MODE, key);
return cipher.doFinal(plainText.getBytes());
}