IllegalBlockSizeException "null" Android 上的 RSA 解密

Question

我目前正在使用我的加密软件的 Android 客户端，但我一直收到 IllegalBlockSizeException，并且 e.getMessage() 总是 returns null

这是我用来查找问题的代码

try {
    KeyPairGenerator generator = KeyPairGenerator.getInstance(KeyProperties.KEY_ALGORITHM_RSA,"AndroidKeyStore");
    generator.initialize(new KeyGenParameterSpec.Builder(
            "1",
            KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT)
            .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_RSA_OAEP)
            .setDigests(KeyProperties.DIGEST_SHA256)
            .setKeySize(2048)
            .build());
    KeyPair kp = generator.generateKeyPair();

    KeyStore store = KeyStore.getInstance("AndroidKeyStore");
    store.load(null);
    PublicKey pubKey = store.getCertificate("1").getPublicKey();
    PrivateKey privkey = ((KeyStore.PrivateKeyEntry) store.getEntry("1",null)).getPrivateKey();

    byte[] content = "123456789".getBytes();
    Cipher encrypt = Cipher.getInstance("RSA/ECB/OAEPWithSHA-256AndMGF1Padding");
    encrypt.init(Cipher.ENCRYPT_MODE,pubKey);
    Cipher decrypt = Cipher.getInstance("RSA/ECB/OAEPWithSHA-256AndMGF1Padding");
    decrypt.init(Cipher.DECRYPT_MODE,privkey);

    byte[] A = encrypt.doFinal(content);
    byte[] B = decrypt.doFinal(A);

    String resultA = new String(A);
    String resultB = new String(B);
    Toast.makeText(getApplicationContext(), resultA + "\n" + resultB, Toast.LENGTH_LONG).show();
} catch (Exception e) {
    e.printStackTrace();
    Toast.makeText(getApplicationContext(), e.toString()+"\n"+e.getMessage(), Toast.LENGTH_LONG).show();
}

正如我所说，有一个 IllegalBlockSizeException，我发现它是由 decrypt.doFinal() 和 e.getMessage() returns null

抛出的

这是我从调试控制台得到的结果

W/System.err: javax.crypto.IllegalBlockSizeException
    at android.security.keystore.AndroidKeyStoreCipherSpiBase.engineDoFinal(AndroidKeyStoreCipherSpiBase.java:519)
    at javax.crypto.Cipher.doFinal(Cipher.java:1741)
W/System.err:     at storm.cyanine.decryptor.MainActivity$override.onJob(MainActivity.java:187)
    at storm.cyanine.decryptor.MainActivity$override.onOpen(MainActivity.java:115)
    at storm.cyanine.decryptor.MainActivity$override.access$dispatch(Unknown Source:50)
    at storm.cyanine.decryptor.MainActivity.onOpen(Unknown Source:15)
    at java.lang.reflect.Method.invoke(Native Method)
    at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385)
W/System.err:     at android.view.View.performClick(View.java:6329)
    at android.view.View$PerformClick.run(View.java:24996)
    at android.os.Handler.handleCallback(Handler.java:809)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:166)
    at android.app.ActivityThread.main(ActivityThread.java:7377)
W/System.err:     at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:469)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:963)
W/System.err: Caused by: android.security.KeyStoreException: Unknown error
    at android.security.KeyStore.getKeyStoreException(KeyStore.java:709)
    at android.security.keystore.KeyStoreCryptoOperationChunkedStreamer.doFinal(KeyStoreCryptoOperationChunkedStreamer.java:224)
    at android.security.keystore.AndroidKeyStoreCipherSpiBase.engineDoFinal(AndroidKeyStoreCipherSpiBase.java:506)
    ... 16 more

起初，我以为是AndroidKeyStore的一些限制阻止我使用私钥，所以我尝试直接使用KeyPairGenerator生成的私钥，但没有任何改变

什么可能导致此问题？

我在网上搜索了好几天，没有发现上面的代码有什么问题（除了不是最终产品）

我的设备是 Android 8.1.0

Edit: Thanks Steve Miskovetz a lot for the solution, and I just found the Android official guide for this topic: Cryptography

(don't know why I wasn't able to find this earlier)

Answer 1

您的问题似乎是由 Android Oreo 引入的，但有解决方法。

这个 Whosebug post 对此进行了讨论：
Android 8.0: IllegalBlocksizeException when using RSA/ECB/OAEPWithSHA-512AndMGF1Padding

这个 Google 问题跟踪器对此有很好的讨论：
https://issuetracker.google.com/issues/36708951

您需要添加这一行：

OAEPParameterSpec sp = new OAEPParameterSpec("SHA-256", "MGF1", new MGF1ParameterSpec("SHA-1"), PSource.PSpecified.DEFAULT);

并修改这些行，添加 sp 参数：

encrypt.init(Cipher.ENCRYPT_MODE,pubKey,sp);
decrypt.init(Cipher.DECRYPT_MODE,privkey,sp);

您在此处进行修改后的完整代码：

try {
    KeyPairGenerator generator = KeyPairGenerator.getInstance(KeyProperties.KEY_ALGORITHM_RSA,"AndroidKeyStore");
    generator.initialize(new KeyGenParameterSpec.Builder(
            "1",
            KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT)
            .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_RSA_OAEP)
            .setDigests(KeyProperties.DIGEST_SHA256)
            .setKeySize(2048)
            .build());
    KeyPair kp = generator.generateKeyPair();

    KeyStore store = KeyStore.getInstance("AndroidKeyStore");
    store.load(null);
    PublicKey pubKey = store.getCertificate("1").getPublicKey();
    PrivateKey privkey = ((KeyStore.PrivateKeyEntry) store.getEntry("1",null)).getPrivateKey();

    byte[] content = "123456789".getBytes();
    OAEPParameterSpec sp = new OAEPParameterSpec("SHA-256", "MGF1", new MGF1ParameterSpec("SHA-1"), PSource.PSpecified.DEFAULT);
    Cipher encrypt = Cipher.getInstance("RSA/ECB/OAEPWithSHA-256AndMGF1Padding");
    encrypt.init(Cipher.ENCRYPT_MODE,pubKey,sp);
    Cipher decrypt = Cipher.getInstance("RSA/ECB/OAEPWithSHA-256AndMGF1Padding");
    decrypt.init(Cipher.DECRYPT_MODE,privkey,sp);

    byte[] A = encrypt.doFinal(content);
    byte[] B = decrypt.doFinal(A);

    String resultA = new String(A);
    String resultB = new String(B);
    Toast.makeText(getApplicationContext(), resultA + "\n" + resultB, Toast.LENGTH_LONG).show();
} catch (Exception e) {
    e.printStackTrace();
    Toast.makeText(getApplicationContext(), e.toString()+"\n"+e.getMessage(), Toast.LENGTH_LONG).show();
}

Answer 2

非对称密钥加密可从 android 6+（api 23+）获得。这是 android 加密的一个很好的指南。在调用 getBytes 之后，您还需要使用 Base64 对字节进行编码。

IllegalBlockSizeException "null" Android 上的 RSA 解密

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