我正在使用 Android M 指纹 API 来允许用户登录到应用程序。为此，我需要将用户名和密码存储在设备上。目前我有登录工作，以及指纹 API，但用户名和密码都存储为明文。我想在存储密码之前对其进行加密，并在用户使用他们的指纹进行身份验证后能够检索它。
我很难让它发挥作用。我一直在尝试从Android 安全示例中应用我所能做的，但每个示例似乎只处理加密或签名，而从不解密。
到目前为止，我必须使用非对称加密来获取AndroidKeyStore、 aKeyPairGenerator和 a的实例，Cipher以允许使用 Android KeyGenParameterSpec.Builder().setUserAuthenticationRequired(true)。非对称加密的原因是，如果用户未通过身份验证，该setUserAuthenticationRequired方法将阻止对密钥的任何使用，但是：
此授权仅适用于密钥和私钥操作。公钥操作不受限制。
这应该允许我在用户使用他们的指纹进行身份验证之前使用公钥加密密码，然后仅在用户通过身份验证后使用私钥解密。
public KeyStore getKeyStore() {
try {
return KeyStore.getInstance("AndroidKeyStore");
} catch (KeyStoreException exception) {
throw new RuntimeException("Failed to get an instance of KeyStore", exception);
}
}
public KeyPairGenerator getKeyPairGenerator() {
try {
return KeyPairGenerator.getInstance("EC", "AndroidKeyStore");
} catch(NoSuchAlgorithmException | NoSuchProviderException exception) {
throw new RuntimeException("Failed to get an instance of KeyPairGenerator", exception);
}
}
public Cipher getCipher() {
try {
return Cipher.getInstance("EC");
} catch(NoSuchAlgorithmException | NoSuchPaddingException exception) {
throw new RuntimeException("Failed to get an instance of Cipher", exception);
}
}
private void createKey() {
try {
mKeyPairGenerator.initialize(
new KeyGenParameterSpec.Builder(KEY_ALIAS,
KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT)
.setAlgorithmParameterSpec(new ECGenParameterSpec("secp256r1")
.setUserAuthenticationRequired(true)
.build());
mKeyPairGenerator.generateKeyPair();
} catch(InvalidAlgorithmParameterException exception) {
throw new RuntimeException(exception);
}
}
private boolean initCipher(int opmode) {
try {
mKeyStore.load(null);
if(opmode == Cipher.ENCRYPT_MODE) {
PublicKey key = mKeyStore.getCertificate(KEY_ALIAS).getPublicKey();
mCipher.init(opmode, key);
} else {
PrivateKey key = (PrivateKey) mKeyStore.getKey(KEY_ALIAS, null);
mCipher.init(opmode, key);
}
return true;
} catch (KeyPermanentlyInvalidatedException exception) {
return false;
} catch(KeyStoreException | CertificateException | UnrecoverableKeyException
| IOException | NoSuchAlgorithmException | InvalidKeyException
| InvalidAlgorithmParameterException exception) {
throw new RuntimeException("Failed to initialize Cipher", exception);
}
}
private void encrypt(String password) {
try {
initCipher(Cipher.ENCRYPT_MODE);
byte[] bytes = mCipher.doFinal(password.getBytes());
String encryptedPassword = Base64.encodeToString(bytes, Base64.NO_WRAP);
mPreferences.getString("password").set(encryptedPassword);
} catch(IllegalBlockSizeException | BadPaddingException exception) {
throw new RuntimeException("Failed to encrypt password", exception);
}
}
private String decryptPassword(Cipher cipher) {
try {
String encryptedPassword = mPreferences.getString("password").get();
byte[] bytes = Base64.decode(encryptedPassword, Base64.NO_WRAP);
return new String(cipher.doFinal(bytes));
} catch (IllegalBlockSizeException | BadPaddingException exception) {
throw new RuntimeException("Failed to decrypt password", exception);
}
}
老实说，我不确定这是否正确，这是我能找到的关于该主题的所有内容的零碎。我更改的所有内容都会引发不同的异常，并且此特定构建不会运行，因为我无法实例化Cipher，它会引发NoSuchAlgorithmException: No provider found for EC. 我也尝试过切换到RSA，但我遇到了类似的错误。
所以我的问题基本上是这样的；如何在 Android 上加密明文，并在用户通过指纹 API 身份验证后使其可用于解密？
我取得了一些进展，主要是由于发现了KeyGenParameterSpec文档页面上的信息。
我保留了getKeyStore, encryptePassword, decryptPassword,getKeyPairGenerator和getCipher大部分相同，但我分别将and更改为KeyPairGenerator.getInstanceand 。Cipher.getInstance"RSA""RSA/ECB/OAEPWithSHA-256AndMGF1Padding"
我还将其余代码更改为 RSA 而不是椭圆曲线，因为据我了解，Java 1.7（因此 Android）不支持使用 EC 进行加密和解密。createKeyPair我根据文档页面上的“使用 RSA OAEP 进行加密/解密的 RSA 密钥对”示例更改了我的方法：
private void createKeyPair() {
try {
mKeyPairGenerator.initialize(
new KeyGenParameterSpec.Builder(KEY_ALIAS, KeyProperties.PURPOSE_DECRYPT)
.setDigests(KeyProperties.DIGEST_SHA256, KeyProperties.DIGEST_SHA512)
.setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_RSA_OAEP)
.setUserAuthenticationRequired(true)
.build());
mKeyPairGenerator.generateKeyPair();
} catch(InvalidAlgorithmParameterException exception) {
throw new RuntimeException(exception);
}
}
我还根据文档中的已知问题initCipher更改了我的方法：KeyGenParameterSpec
Android 6.0（API 级别 23）中的一个已知错误会导致即使对公钥也强制执行与用户身份验证相关的授权。要解决此问题，请提取公钥材料以在 Android Keystore 之外使用。
private boolean initCipher(int opmode) {
try {
mKeyStore.load(null);
if(opmode == Cipher.ENCRYPT_MODE) {
PublicKey key = mKeyStore.getCertificate(KEY_ALIAS).getPublicKey();
PublicKey unrestricted = KeyFactory.getInstance(key.getAlgorithm())
.generatePublic(new X509EncodedKeySpec(key.getEncoded()));
mCipher.init(opmode, unrestricted);
} else {
PrivateKey key = (PrivateKey) mKeyStore.getKey(KEY_ALIAS, null);
mCipher.init(opmode, key);
}
return true;
} catch (KeyPermanentlyInvalidatedException exception) {
return false;
} catch(KeyStoreException | CertificateException | UnrecoverableKeyException
| IOException | NoSuchAlgorithmException | InvalidKeyException
| InvalidAlgorithmParameterException exception) {
throw new RuntimeException("Failed to initialize Cipher", exception);
}
}
现在我可以加密密码，并保存加密的密码。但是当我获得加密密码并尝试解密时，我收到一个KeyStoreException 未知错误...
03-15 10:06:58.074 14702-14702/com.example.app E/LoginFragment: Failed to decrypt password
javax.crypto.IllegalBlockSizeException
at android.security.keystore.AndroidKeyStoreCipherSpiBase.engineDoFinal(AndroidKeyStoreCipherSpiBase.java:486)
at javax.crypto.Cipher.doFinal(Cipher.java:1502)
at com.example.app.ui.fragment.util.LoginFragment.onAuthenticationSucceeded(LoginFragment.java:251)
at com.example.app.ui.controller.FingerprintCallback.onAuthenticationSucceeded(FingerprintCallback.java:21)
at android.support.v4.hardware.fingerprint.FingerprintManagerCompat$Api23FingerprintManagerCompatImpl$1.onAuthenticationSucceeded(FingerprintManagerCompat.java:301)
at android.support.v4.hardware.fingerprint.FingerprintManagerCompatApi23$1.onAuthenticationSucceeded(FingerprintManagerCompatApi23.java:96)
at android.hardware.fingerprint.FingerprintManager$MyHandler.sendAuthenticatedSucceeded(FingerprintManager.java:805)
at android.hardware.fingerprint.FingerprintManager$MyHandler.handleMessage(FingerprintManager.java:757)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: android.security.KeyStoreException: Unknown error
at android.security.KeyStore.getKeyStoreException(KeyStore.java:632)
at android.security.keystore.KeyStoreCryptoOperationChunkedStreamer.doFinal(KeyStoreCryptoOperationChunkedStreamer.java:224)
at android.security.keystore.AndroidKeyStoreCipherSpiBase.engineDoFinal(AndroidKeyStoreCipherSpiBase.java:473)
at javax.crypto.Cipher.doFinal(Cipher.java:1502)
at com.example.app.ui.fragment.util.LoginFragment.onAuthenticationSucceeded(LoginFragment.java:251)
at com.example.app.ui.controller.FingerprintCallback.onAuthenticationSucceeded(FingerprintCallback.java:21)
at android.support.v4.hardware.fingerprint.FingerprintManagerCompat$Api23FingerprintManagerCompatImpl$1.onAuthenticationSucceeded(FingerprintManagerCompat.java:301)
at android.support.v4.hardware.fingerprint.FingerprintManagerCompatApi23$1.onAuthenticationSucceeded(FingerprintManagerCompatApi23.java:96)
at android.hardware.fingerprint.FingerprintManager$MyHandler.sendAuthenticatedSucceeded(FingerprintManager.java:805)
at android.hardware.fingerprint.FingerprintManager$MyHandler.handleMessage(FingerprintManager.java:757)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)