Android AES 解密和来自 iOS :javax. crypto.BadPaddingException 的数据:填充 block 已损坏

Question

我试图在 Android 上解密从 iOS 发送的备份，异常 javax.crypto.BadPaddingException: pad block corrupted 显示在方法 doFinal 中。

public  String decrypt(byte[] cipherText, SecretKey key, byte [] initialVector) throws Exception {
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
    IvParameterSpec ivParameterSpec = new IvParameterSpec(initialVector);
    cipher.init(Cipher.DECRYPT_MODE, key, ivParameterSpec);
    cipherText = cipher.doFinal(cipherText);

    return new String(cipherText, "UTF-8");
}

key 和 initialVector 以 base64 字符串形式从 iOS 发送。相关代码:

public static byte[] decodeWebSafe(String s) throws Base64DecoderException {
    byte[] bytes = s.getBytes();
    return decodeWebSafe(bytes, 0, bytes.length);
}

byte[] iv = Base64.decodeWebSafe(enciv);
byte[] salt = Base64.decodeWebSafe(encsalt);
byte[] data = Base64.decodeWebSafe(encdata);
SecretKey key = Security.getExistingKey(password, salt);
String original = aes.decrypt(data, key, iv);

关于 Security.getExistingKey:

public static SecretKey getExistingKey(String password, byte[] salt) throws Exception{
    SecretKey key= null;
    KeySpec keySpec = new PBEKeySpec(password.toCharArray(), salt, 10000, 256);
    SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");

    byte[] keyBytes=new byte[32]; 
    keyBytes = keyFactory.generateSecret(keySpec).getEncoded();
    key= new SecretKeySpec(keyBytes, "AES");

    return key;
}

感谢任何解决方案。

P.S.这是我们在 iOS 中设置加密的方式:

CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128,
kCCOptionPKCS7Padding,
self.encryptionKey.bytes, kCCKeySizeAES128,
self.encryptionIV.bytes, [rawData bytes], dataLength, 
/* input */buffer, bufferSize, /* output */&numBytesEncrypted);

key 和IV推导方法:

(NSData *)keyForPassword:(NSString *)password salt:(NSData *)salt {
NSMutableData *
derivedKey = [NSMutableData dataWithLength:kCCKeySizeAES128];

int result = CCKeyDerivationPBKDF(kCCPBKDF2,            // algorithm
                              password.UTF8String, 
                              password.length,  
                              salt.bytes,           // salt
                              salt.length,          // saltLen
                              kCCPRFHmacAlgSHA1,    // PRF
                              kPBKDFRounds,         // rounds
                              derivedKey.mutableBytes, // derivedKey
                              derivedKey.length); // derivedKeyLen
}

Answer 1

这是为解密/加密消息生成字符串的 Android 版本，它使用 Cipher 并生成正确的向量以产生与 iOS 相同的结果。对应本帖@亚历山大的iOS版本。

public class MyCrypter {

private static String TAG = "MyCrypter";

public MyCrypter() {

}

/**
 * Encodes a String in AES-128 with a given key
 * 
 * @param context
 * @param password
 * @param text
 * @return String Base64 and AES encoded String
 * @throws NoPassGivenException
 * @throws NoTextGivenException
 */
public String encode(Context context, String password, String text)
        throws NoPassGivenException, NoTextGivenException {
    if (password.length() == 0 || password == null) {
        throw new NoPassGivenException("Please give Password");
    }

    if (text.length() == 0 || text == null) {
        throw new NoTextGivenException("Please give text");
    }

    try {
        SecretKeySpec skeySpec = getKey(password);
        byte[] clearText = text.getBytes("UTF8");

        //IMPORTANT TO GET SAME RESULTS ON iOS and ANDROID
        final byte[] iv = new byte[16];
        Arrays.fill(iv, (byte) 0x00);
        IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);

        // Cipher is not thread safe
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec, ivParameterSpec);

        String encrypedValue = Base64.encodeToString(
                cipher.doFinal(clearText), Base64.DEFAULT);
        Log.d(TAG, "Encrypted: " + text + " -> " + encrypedValue);
        return encrypedValue;

    } catch (InvalidKeyException e) {
        e.printStackTrace();
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    } catch (BadPaddingException e) {
        e.printStackTrace();
    } catch (NoSuchPaddingException e) {
        e.printStackTrace();
    } catch (IllegalBlockSizeException e) {
        e.printStackTrace();
    } catch (InvalidAlgorithmParameterException e) {
        e.printStackTrace();
    }
    return "";
}

/**
 * Decodes a String using AES-128 and Base64
 * 
 * @param context
 * @param password
 * @param text
 * @return desoded String
 * @throws NoPassGivenException
 * @throws NoTextGivenException
 */
public String decode(Context context, String password, String text)
        throws NoPassGivenException, NoTextGivenException {

    if (password.length() == 0 || password == null) {
        throw new NoPassGivenException("Please give Password");
    }

    if (text.length() == 0 || text == null) {
        throw new NoTextGivenException("Please give text");
    }

    try {
        SecretKey key = getKey(password);

        //IMPORTANT TO GET SAME RESULTS ON iOS and ANDROID
        final byte[] iv = new byte[16];
        Arrays.fill(iv, (byte) 0x00);
        IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);

        byte[] encrypedPwdBytes = Base64.decode(text, Base64.DEFAULT);
        // cipher is not thread safe
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
        cipher.init(Cipher.DECRYPT_MODE, key, ivParameterSpec);
        byte[] decrypedValueBytes = (cipher.doFinal(encrypedPwdBytes));

        String decrypedValue = new String(decrypedValueBytes);
        Log.d(TAG, "Decrypted: " + text + " -> " + decrypedValue);
        return decrypedValue;

    } catch (InvalidKeyException e) {
        e.printStackTrace();
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    } catch (BadPaddingException e) {
        e.printStackTrace();
    } catch (NoSuchPaddingException e) {
        e.printStackTrace();
    } catch (IllegalBlockSizeException e) {
        e.printStackTrace();
    } catch (InvalidAlgorithmParameterException e) {
        e.printStackTrace();
    }
    return "";
}

/**
 * Generates a SecretKeySpec for given password
 * @param password
 * @return SecretKeySpec
 * @throws UnsupportedEncodingException
 */
public SecretKeySpec getKey(String password)
        throws UnsupportedEncodingException {


    int keyLength = 128;
    byte[] keyBytes = new byte[keyLength / 8];
    // explicitly fill with zeros
    Arrays.fill(keyBytes, (byte) 0x0);

    // if password is shorter then key length, it will be zero-padded
    // to key length
    byte[] passwordBytes = password.getBytes("UTF-8");
    int length = passwordBytes.length < keyBytes.length ? passwordBytes.length
            : keyBytes.length;
    System.arraycopy(passwordBytes, 0, keyBytes, 0, length);
    SecretKeySpec key = new SecretKeySpec(keyBytes, "AES");
    return key;
}

public class NoTextGivenException extends Exception {
    public NoTextGivenException(String message) {
        super(message);
    }

}

public class NoPassGivenException extends Exception {
    public NoPassGivenException(String message) {
        super(message);
    }

}

}