256 位 AES/CBC/PKCS5 填充，带充气城堡

java aes cryptography bouncycastle

2022-09-04 00:59:53

我在将以下JDK JCE加密代码映射到Bouncy Castles轻量级API时遇到问题：

public String dec(String password, String salt, String encString) throws Throwable {
    // AES algorithm with CBC cipher and PKCS5 padding
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding", "BC");

    // Construct AES key from salt and 50 iterations 
    PBEKeySpec pbeEKeySpec = new PBEKeySpec(password.toCharArray(), toByte(salt), 50, 256);
    SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithSHA256And256BitAES-CBC-BC");
    SecretKeySpec secretKey = new SecretKeySpec(keyFactory.generateSecret(pbeEKeySpec).getEncoded(), "AES");

    // IV seed for first block taken from first 32 bytes
    byte[] ivData = toByte(encString.substring(0, 32));
    // AES encrypted data
    byte[] encData = toByte(encString.substring(32));

    cipher.init( Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec( ivData ) );

    return new String( cipher.doFinal( encData ) );
}

上述方法效果很好，但由于Oracle对加密强度的限制，因此移植性不是很强。我已经多次尝试移植到Bouncy Castles轻量级API，但没有成功。

public String decrypt1(String password, String salt, String encString) throws Exception {

    byte[] ivData = toByte(encString.substring(0, 32));
    byte[] encData = toByte(encString.substring(32));

    PKCS12ParametersGenerator gen = new PKCS12ParametersGenerator(new SHA256Digest());
    gen.init(password.getBytes(), toByte(salt), 50);
    CBCBlockCipher cbcBlockcipher = new CBCBlockCipher(new RijndaelEngine(256));
    CipherParameters params = gen.generateDerivedParameters(256, 256);

    cbcBlockcipher.init(false, params);

    PaddedBufferedBlockCipher aesCipher = new PaddedBufferedBlockCipher(cbcBlockcipher, new PKCS7Padding());
    byte[] plainTemp = new byte[aesCipher.getOutputSize(encData.length)];
    int offset = aesCipher.processBytes(encData, 0, encData.length, plainTemp, 0);
    int last = aesCipher.doFinal(plainTemp, offset);
    byte[] plain = new byte[offset + last];
    System.arraycopy(plainTemp, 0, plain, 0, plain.length);
    return new String(plain);
}

上述尝试导致 org.bouncycastle.crypto.DataLengthException：解密中的最后一个块不完整。

我已经在网上搜索了示例，但是使用PKCS5 / PKCS7作为填充为CBC为256位AES提供自己的IV数据的示例并不多。

注意：toByte 函数使用 base64 或类似函数将 String 转换为字节数组。

答案 1

这应该适用于您：

public String dec(String password, String salt, String encString)
        throws Exception {

    byte[] ivData = toByte(encString.substring(0, 32));
    byte[] encData = toByte(encString.substring(32));

    // get raw key from password and salt
    PBEKeySpec pbeKeySpec = new PBEKeySpec(password.toCharArray(),
            toByte(salt), 50, 256);
    SecretKeyFactory keyFactory = SecretKeyFactory
            .getInstance("PBEWithSHA256And256BitAES-CBC-BC");
    SecretKeySpec secretKey = new SecretKeySpec(keyFactory.generateSecret(
            pbeKeySpec).getEncoded(), "AES");
    byte[] key = secretKey.getEncoded();

    // setup cipher parameters with key and IV
    KeyParameter keyParam = new KeyParameter(key);
    CipherParameters params = new ParametersWithIV(keyParam, ivData);

    // setup AES cipher in CBC mode with PKCS7 padding
    BlockCipherPadding padding = new PKCS7Padding();
    BufferedBlockCipher cipher = new PaddedBufferedBlockCipher(
            new CBCBlockCipher(new AESEngine()), padding);
    cipher.reset();
    cipher.init(false, params);

    // create a temporary buffer to decode into (it'll include padding)
    byte[] buf = new byte[cipher.getOutputSize(encData.length)];
    int len = cipher.processBytes(encData, 0, encData.length, buf, 0);
    len += cipher.doFinal(buf, len);

    // remove padding
    byte[] out = new byte[len];
    System.arraycopy(buf, 0, out, 0, len);

    // return string representation of decoded bytes
    return new String(out, "UTF-8");
}

我假设您实际上正在执行十六进制编码，因为您的代码对 IV 使用 32 个字符（提供必要的 16 个字节）。虽然我没有您用于加密的代码，但我确实验证了此代码将提供与您的代码相同的解密输出。toByte()

答案 2