BadPaddingException：给定的最终块没有正确填充-奇怪的错误

Question

public String decrypt(String text) throws Exception {

    String key = "SiadajerSiadajer"; // 128 bit key
    // Create key and cipher
    Key aesKey = new SecretKeySpec(key.getBytes(), "AES");
    Cipher cipher = Cipher.getInstance("AES");
    // encrypt the text
    byte[]encrypted = text.getBytes();
    cipher.init(Cipher.DECRYPT_MODE, aesKey);
    String decrypted = new String(cipher.doFinal(encrypted)); //Here is the error

    return decrypted;


}

function encrypt($data, $size)
{
    $length = $size - strlen($data) % $size;
    return $data . str_repeat(chr($length), $length);
}

function decrypt($data)
{
    return substr($data, 0, -ord($data[strlen($data) - 1]));
}
$key = "SiadajerSiadajer";
$iv_size = 16; // 128 bits
$iv = openssl_random_pseudo_bytes($iv_size, $strong);
$name = openssl_encrypt(encrypt($name, 16), 'AES-256-CBC', $key, 0, $iv);

现在在php部分，我的代码是：

$key = "SiadajerSiadajer";
$iv_size = 16; // 128 bits
$iv = openssl_random_pseudo_bytes($iv_size, $strong);
$EIV = base64_encode($iv);
$name = openssl_encrypt(encrypt($name, 16), 'AES-256-CBC', $key, 0, $EIV);

它给我一个警告：警告:openssl_encrypt():IV传递的是24字节长，比所选密码预期的16字节长，在第68行的C:\xampp2\htdocs\standardfinalinserting.php中截断

在Java部分，我的解密方法与我的问题的答案完全相同，但在运行后，它给我一个错误：Java.security.invalidkeyexception：行上非法的密钥大小：

所以这就是我的整个主课。它包含您的整个Java代码示例

public class Main {

    private byte[] padKey(byte[] key) {
        byte[] paddedKey = new byte[32];
        System.arraycopy(key, 0, paddedKey, 0, key.length);
        return paddedKey;
    }

    private byte[] unpad(byte[] data) {     
        byte[] unpaddedData = new byte[data.length - data[data.length - 1]];
        System.arraycopy(data, 0, unpaddedData, 0, unpaddedData.length);
        return unpaddedData;
    }

    public String decrypt(String encodedJoinedData) throws Exception {

        // Base64-decode the joined data
        byte[] joinedData = Base64.decode(encodedJoinedData); 

        // Get IV and encrypted data
        byte[] iv = new byte[16];
        System.arraycopy(joinedData, 0, iv, 0, iv.length);
        byte[] encryptedData = new byte[joinedData.length - iv.length];
        System.arraycopy(joinedData, iv.length, encryptedData, 0, encryptedData.length);

        // Pad key
        byte[] key = padKey("SiadajerSiadajer".getBytes()); 
        Key aesKey = new SecretKeySpec(key, "AES");

        // Specify CBC-mode
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding"); 
        IvParameterSpec ivParameterSpec = new IvParameterSpec(iv); 
        cipher.init(Cipher.DECRYPT_MODE, aesKey, ivParameterSpec); //HERE IS THE ERROR

        // Decrypt data
        byte[] decryptedData = cipher.doFinal(encryptedData);

        // Remove custom padding
        byte[] unpaddedData = unpad(decryptedData);         

        return new String(unpaddedData);
    }

    public static void main(String[] args) throws Exception {
        // TODO Auto-generated method stub
         String encodedJoinedData = "RB6Au33KGOF1/z3BQKqievUmh81Y8q4uw7s4vEs9xurQmNZAKwmhRQtS9wGYKQj8cJaPpK2xaDzx3RppQ8PsM/rQ9/p0Lme+x75dozBEbmFn6Q9eCXOCiCivVsKzZ8Vz";
            String decryptedData = new Main().decrypt(encodedJoinedData);
            System.out.println(decryptedData + " - " + decryptedData.length());



     }



}

运行代码会导致错误：

Exception in thread "main" java.security.InvalidKeyException: Illegal key size
    at javax.crypto.Cipher.checkCryptoPerm(Cipher.java:1039)
    at javax.crypto.Cipher.implInit(Cipher.java:805)
    at javax.crypto.Cipher.chooseProvider(Cipher.java:864)
    at javax.crypto.Cipher.init(Cipher.java:1396)
    at javax.crypto.Cipher.init(Cipher.java:1327)
    at com.dd.escuel.Main.decrypt(Main.java:43)
    at com.dd.escuel.Main.main(Main.java:57)

Answer 1

Java代码存在一些问题：

>

在PHP代码中使用AES-256，因此，密钥的长度必须为32字节。较短的键自动右加零。这发生在PHP代码中，因为您的键siadajersiadajer的长度只有16字节。键填充也必须在Java代码中完成。为此，可以使用以下Java-method：

private byte[] padKey(byte[] key) {
    byte[] paddedKey = new byte[32];
    System.arraycopy(key, 0, paddedKey, 0, key.length);
    return paddedKey;
}

对于cipher.getinstance（“aes”），默认情况下选择ecb-mode和pkcs5padding。cbc-mode必须在Java-code中显式指定

Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");

byte[]encryptedData = Base64.decode(text); 

$encodedIV = base64_encode($iv);

byte[] iv = Base64.decode(ivEncoded);
IvParameterSpec ivParameterSpec = new IvParameterSpec(iv); 
...
cipher.init(Cipher.DECRYPT_MODE, aesKey, ivParameterSpec);

在PHP-methodopenSSL_encrypt中，第四个参数$options被设置为0，这意味着使用默认填充(PKCS7)。此外，在PHP-methodencrypt中实现了一种自定义填充（顺便说一句：方法的名称不合适，因为它不加密），因此它被填充了两次。因此，在解密之后，必须删除Java代码中的自定义填充（可能包含空白）：

byte[] unpaddedData = unpad(decryptedData);

与

private byte[] unpad(byte[] data) {     
    byte[] unpaddedData = new byte[data.length - data[data.length - 1]];
    System.arraycopy(data, 0, unpaddedData, 0, unpaddedData.length);
    return unpaddedData;
}

总共：

public String decrypt(String text, String ivEncoded) throws Exception {

    // Pad key
    byte[] key = padKey("SiadajerSiadajer".getBytes()); 
    Key aesKey = new SecretKeySpec(key, "AES");

    // Base64 decode data
    byte[]encryptedData = Base64.decode(text); 

    // Base64 decode iv
    byte[] iv = Base64.decode(ivEncoded);
    IvParameterSpec ivParameterSpec = new IvParameterSpec(iv); 

    // Specify CBC-mode
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding"); 
    cipher.init(Cipher.DECRYPT_MODE, aesKey, ivParameterSpec);

    // Decrypt
    byte[] decryptedData = cipher.doFinal(encryptedData);

    // Remove custom padding
    byte[] unpaddedData = unpad(decryptedData);         

    return new String(unpaddedData);
}

$data = 'This is a plain text which needs to be encrypted...';
$key = "SiadajerSiadajer";

$encodedIV = 'Dg+Zs3mqIJeDOOEPMT5F4Q==';
$name = '8dXjeQhx2WSswQOQXLcyMKNpa5s413yI2Ku8WiIB/xtA2pEjrKcl5kWtrOh9k4A12Jl0N/z6tH67Wybhp/OwTi1NtiJOZxl3w6YQufE29oU=';

如果该输出用作Java-methoddecrypt的输入，则解密数据等于纯文本。

关于PHP代码，我建议删除自定义或默认(PKCS7)填充（如果可以选择的话）。后者可以通过使用标志openSSL_zero_padding作为openSSL_encrypt方法中的第四个参数来实现（注意：该标志并不表示“pad with zero-values”，而是表示“no padding”）。如果保留自定义填充，则至少应将PHP-methodsencrypt和decrypt分别重命名为pad和unpad（或类似的内容）。

正如在注释中已经指出的，gcm-模式可能比-cbc模式更好。但是，在编码之前了解一些基本知识是很有用的，例如cbc-和GCM-模式之间的区别，这里和这里对GCM-mode的解释，以及GCM-mode带来的缺陷（GCM是安全的，但前提是您必须遵循某些指导原则，例如，对使用相同密钥加密的每个消息使用uniqe IV/nonce）。

您可以使用php方法openssl_get_cipher_methods来查找PHP中支持的允许的AES模式。这里对此有更详细的解释。对于AES-256和AES模式gcm，必须指定aes-256-gcm（用小写（！）字母）。大概，这就是为什么你会得到“未知密码算法”--错误。

编辑：

您可以使用以下PHP-code进行加密（它是问题中的PHP-code的稍微修改版本）：

<?php
function pad($data, $size) {
    $length = $size - strlen($data) % $size;
    return $data . str_repeat(chr($length), $length);
}
function unpad($data) {
    return substr($data, 0, -ord($data[strlen($data) - 1]));
}
$data = 'This is a plain text which needs to be encrypted...';
$key = "SiadajerSiadajer";
$iv_size = 16; 
$iv = openssl_random_pseudo_bytes($iv_size, $strong);
$encryptedData = openssl_encrypt(pad($data, 16), 'AES-256-CBC', $key,  0, $iv);
print base64_encode($iv)."\n".$encryptedData."\n";

<?php
function pad($data, $size) {
    $length = $size - strlen($data) % $size;
    return $data . str_repeat(chr($length), $length);
}
function unpad($data) {
    return substr($data, 0, -ord($data[strlen($data) - 1]));
}
$data = 'This is a plain text which needs to be encrypted...';
$key = "SiadajerSiadajer";
$iv_size = 16; 
$iv = openssl_random_pseudo_bytes($iv_size, $strong);
$encryptedData = openssl_encrypt(pad($data, 16), 'AES-256-CBC', $key, OPENSSL_RAW_DATA, $iv);
$joinedData = $iv.$encryptedData;
$encodedJoinedData = base64_encode($joinedData);
print $encodedJoinedData."\n";

Jave-methoddecrypt变为：

public String decrypt(String encodedJoinedData) throws Exception {

    // Base64-decode the joined data
    byte[] joinedData = Base64.decode(encodedJoinedData); 

    // Get IV and encrypted data
    byte[] iv = new byte[16];
    System.arraycopy(joinedData, 0, iv, 0, iv.length);
    byte[] encryptedData = new byte[joinedData.length - iv.length];
    System.arraycopy(joinedData, iv.length, encryptedData, 0, encryptedData.length);

    // Pad key
    byte[] key = padKey("SiadajerSiadajer".getBytes()); 
    Key aesKey = new SecretKeySpec(key, "AES");

    // Specify CBC-mode
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding"); 
    IvParameterSpec ivParameterSpec = new IvParameterSpec(iv); 
    cipher.init(Cipher.DECRYPT_MODE, aesKey, ivParameterSpec);

    // Decrypt data
    byte[] decryptedData = cipher.doFinal(encryptedData);

    // Remove custom padding
    byte[] unpaddedData = unpad(decryptedData);         

    return new String(unpaddedData);
}

Java-methodmain的示例如下：

public static void main(String[] args) throws Exception {
    String encodedJoinedData = "RB6Au33KGOF1/z3BQKqievUmh81Y8q4uw7s4vEs9xurQmNZAKwmhRQtS9wGYKQj8cJaPpK2xaDzx3RppQ8PsM/rQ9/p0Lme+x75dozBEbmFn6Q9eCXOCiCivVsKzZ8Vz";
    String decryptedData = new Main().decrypt(encodedJoinedData);
    System.out.println(decryptedData + " - " + decryptedData.length());
}

用法如下：

$data = 'This is a plain text which needs to be encrypted...';

String encodedJoinedData = "RB6Au33KGOF1/z3BQKqievUmh81Y8q4uw7s4vEs9xurQmNZAKwmhRQtS9wGYKQj8cJaPpK2xaDzx3RppQ8PsM/rQ9/p0Lme+x75dozBEbmFn6Q9eCXOCiCivVsKzZ8Vz";

$encryptedData = openssl_encrypt(pad($data, 16), 'AES-256-CBC', $key,  OPENSSL_RAW_DATA, $iv);

$encryptedData = openssl_encrypt($data, 'AES-256-CBC', $key,  OPENSSL_RAW_DATA, $iv);

并移除pad-和unpad-方法。

在Java代码中替换行

// Remove custom padding
byte[] unpaddedData = unpad(decryptedData);         

return new String(unpaddedData);

与

return new String(decryptedData);