Android指纹API加密解密

Question

我正在使用 Android M Fingerprint API 允许用户登录应用程序。为此，我需要在设备上存储用户名和密码。目前我有登录工作，以及指纹API，但用户名和密码都以明文形式存储。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。

我很难让它工作。我一直在尝试应用我能从 Android Security samples 中获得的东西，但每个示例似乎只处理加密或签名，而从不处理解密。

到目前为止，我必须获得 AndroidKeyStore、一个 KeyPairGenerator 和一个 Cipher 的实例，使用非对称加密来允许使用 Android KeyGenParameterSpec.Builder().setUserAuthenticationRequired(true)。非对称加密的原因是因为如果用户未通过身份验证，setUserAuthenticationRequired 方法将阻止任何使用密钥，但是：

This authorization applies only to secret key and private key operations. Public key operations are not restricted.

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 public 密钥加密密码，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内容。我更改的所有内容都会引发不同的异常，而这个特定的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。我也试过切换到 RSA，但我得到了类似的错误。

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 验证后使其可用于解密？

我取得了一些进步，主要是由于在 KeyGenParameterSpec 文档页面上发现了信息。

我保持 getKeyStore、encryptePassword、decryptPassword、getKeyPairGenerator 和 getCipher 基本相同，但我更改了 KeyPairGenerator.getInstance和 Cipher.getInstance 分别变为 "RSA" 和 "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。我根据文档页面上的 "RSA key pair for encryption/decryption using RSA OAEP" 示例更改了 createKeyPair 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 KeyGenParameterSpec 文档中的 已知问题 更改了我的 initCipher 方法：

A known bug in Android 6.0 (API Level 23) causes user authentication-related authorizations to be enforced even for public keys. To work around this issue extract the public key material to use outside of Android Keystore.

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，并保存加密后的密码。但是当我获得加密密码并尝试解密时，我得到一个 KeyStoreException Unknown error...

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$Api23FingerprintManagerCompatImpl.onAuthenticationSucceeded(FingerprintManagerCompat.java:301)
            at android.support.v4.hardware.fingerprint.FingerprintManagerCompatApi23.onAuthenticationSucceeded(FingerprintManagerCompatApi23.java:96)
            at android.hardware.fingerprint.FingerprintManager$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$Api23FingerprintManagerCompatImpl.onAuthenticationSucceeded(FingerprintManagerCompat.java:301) 
            at android.support.v4.hardware.fingerprint.FingerprintManagerCompatApi23.onAuthenticationSucceeded(FingerprintManagerCompatApi23.java:96) 
            at android.hardware.fingerprint.FingerprintManager$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)

Answer 1

我在 Android Issue Tracker 上找到了最后一块拼图，另一个已知错误会导致在使用 OAEP 时不受限制的 PublicKey 与 Cipher 不兼容。解决方法是在初始化时向 Cipher 添加一个新的 OAEPParameterSpec：

OAEPParameterSpec spec = new OAEPParameterSpec(
        "SHA-256", "MGF1", MGF1ParameterSpec.SHA1, PSource.PSpecified.DEFAULT);

mCipher.init(opmode, unrestricted, spec);

下面是最终代码：

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("RSA", "AndroidKeyStore");
    } catch(NoSuchAlgorithmException | NoSuchProviderException exception) {
        throw new RuntimeException("Failed to get an instance of KeyPairGenerator", exception);
    }
}

public Cipher getCipher() {
    try {
        return Cipher.getInstance("RSA/ECB/OAEPWithSHA-256AndMGF1Padding");
    } catch(NoSuchAlgorithmException | NoSuchPaddingException exception) {
        throw new RuntimeException("Failed to get an instance of Cipher", exception);
    }
}

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("Failed to generate key pair", exception);
    }
}

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()));

            OAEPParameterSpec spec = new OAEPParameterSpec(
                    "SHA-256", "MGF1", MGF1ParameterSpec.SHA1, PSource.PSpecified.DEFAULT);

            mCipher.init(opmode, unrestricted, spec);
        } 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 encrypted = Base64.encodeToString(bytes, Base64.NO_WRAP);
        mPreferences.getString("password").set(encrypted);
    } catch(IllegalBlockSizeException | BadPaddingException exception) {
        throw new RuntimeException("Failed to encrypt password", exception);
    }
}

private String decrypt(Cipher cipher) {
    try {
        String encoded = mPreferences.getString("password").get();
        byte[] bytes = Base64.decode(encoded, Base64.NO_WRAP);
        return new String(cipher.doFinal(bytes));
    } catch (IllegalBlockSizeException | BadPaddingException exception) {
        throw new RuntimeException("Failed to decrypt password", exception);
    }
}

Android指纹API加密解密

Android Fingerprint API Encryption and Decryption

android

encryption

android-keystore

android-fingerprint-api