[英]How to handle BadPaddingException During AES256 encryption in C# and decryption in Java
我不知道為什么會出現錯誤。
線程“main”中的異常javax.crypto.BadPaddingException：給定最終塊未正確填充。 如果在解密期間使用壞密鑰，則可能出現此類問題。
我知道在解密過程中使用了錯誤的密鑰時會發生此錯誤。 但是，如果查看下面的測試結果結果，可以看到C＃和Java都是相同的（Key，IV，Salt是Base64編碼的）。
它是一樣的！（Key，IV，Salt）
但是生成了當前的BadpaddingException錯誤。 可能是什么問題呢？ 我正在附加我的源文件。
class AES {
private readonly static string keyStr = "This is Key";
private readonly static string vector = "This is Vector";
public static Rfc2898DeriveBytes MakeKey(string password){
byte[] keyBytes = System.Text.Encoding.UTF8.GetBytes(password);
byte[] saltBytes = SHA512.Create().ComputeHash(keyBytes);
Rfc2898DeriveBytes result = new Rfc2898DeriveBytes(keyBytes, saltBytes, 65536);
return result;
}
public static Rfc2898DeriveBytes MakeVector(string vector){
byte[] vectorBytes = System.Text.Encoding.UTF8.GetBytes(vector);
byte[] saltBytes = SHA512.Create().ComputeHash(vectorBytes);
Rfc2898DeriveBytes result = new Rfc2898DeriveBytes(vectorBytes, saltBytes, 65536);
return result;
}
public static void Encrypt(String inputFile, String outputFile) {
using (RijndaelManaged aes = new RijndaelManaged()){
//Create Key and Vector
Rfc2898DeriveBytes key = AES.MakeKey(AES.keyStr);
Rfc2898DeriveBytes vector = AES.MakeVector(AES.vector);
//AES256
aes.BlockSize = 128;
aes.KeySize = 256;
// It is equal in java
// Cipher _Cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
aes.Mode = CipherMode.CBC;
aes.Padding = PaddingMode.PKCS7;
aes.Key = key.GetBytes(32); //256bit key
aes.IV = vector.GetBytes(16); //128bit block size
//processing Encrypt
ICryptoTransform encryptor = aes.CreateEncryptor(aes.Key, aes.IV);
byte[] encrypted;
using (MemoryStream msEncrypt = new MemoryStream()) {
using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write)) {
byte[] inputBytes = File.ReadAllBytes(inputFile);
csEncrypt.Write(inputBytes, 0, inputBytes.Length);
}
encrypted = msEncrypt.ToArray();
}
string encodedString = Convert.ToBase64String(encrypted);
File.WriteAllText(outputFile, encodedString);
}
}
}
public class AES256File {
private static final String algorithm = "AES";
private static final String blockNPadding = algorithm+"/CBC/PKCS5Padding";
private static final String password = "This is Key";
private static final String IV = "This is Vector";
private static IvParameterSpec ivSpec;
private static Key keySpec;
public static void MakeKey(String password) throws NoSuchAlgorithmException, UnsupportedEncodingException, InvalidKeySpecException{
SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
MessageDigest digest = MessageDigest.getInstance("SHA-512");
byte[] keyBytes = password.getBytes("UTF-8");
// C# : byte[] saltBytes = SHA512.Create().ComputeHash(keyBytes);
byte[] saltBytes = digest.digest(keyBytes);
//256bit
PBEKeySpec pbeKeySpec = new PBEKeySpec(password.toCharArray(), saltBytes, 65536, 256);
Key secretKey = factory.generateSecret(pbeKeySpec);
byte[] key = new byte[32];
System.arraycopy(secretKey.getEncoded(), 0, key, 0, 32);
SecretKeySpec secret = new SecretKeySpec(key, "AES");
setKeySpec(secret);
}
public static void MakeVector(String IV) throws NoSuchAlgorithmException, UnsupportedEncodingException, InvalidKeySpecException{
SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
MessageDigest digest = MessageDigest.getInstance("SHA-512");
byte[] vectorBytes = IV.getBytes("UTF-8");
byte[] saltBytes = digest.digest(vectorBytes);
// 128bit
PBEKeySpec pbeKeySpec = new PBEKeySpec(IV.toCharArray(), saltBytes, 65536, 128);
Key secretIV = factory.generateSecret(pbeKeySpec);
byte[] iv = new byte[16];
System.arraycopy(secretIV.getEncoded(), 0, iv, 0, 16);
IvParameterSpec ivSpec = new IvParameterSpec(iv);
setIvSpec(ivSpec);
}
public void decrypt(File source, File dest) throws Exception {
Cipher c = Cipher.getInstance(blockNPadding);
c.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);
fileProcessing(source, dest, c);
}
public void fileProcessing(File source, File dest, Cipher c) throws Exception{
InputStream input = null;
OutputStream output = null;
try{
input = new BufferedInputStream(new FileInputStream(source));
output = new BufferedOutputStream(new FileOutputStream(dest));
byte[] buffer = new byte[input.available()];
int read = -1;
while((read = input.read(buffer)) != -1){
output.write(c.update(buffer, 0, read));
}
byte[] deryptedBytes = c.doFinal(buffer); // -----------------------> Error!! Showing!
byte[] decodedBytes = Base64.getDecoder().decode(deryptedBytes);
String decodeString = new String(decodedBytes, "UTF-8");
decodedBytes = decodeString.getBytes(StandardCharsets.UTF_8);
output.write(decodedBytes);
}finally{
if(output != null){
try{output.close();}catch(IOException e){}
}
if(input != null){
try{input.close();}catch(IOException e){}
}
}
}
我已經驗證如下。
//Key Verification
var salt = Convert.ToBase64String(saltBytes);
Console.Write("Salt Result : ");
Console.WriteLine(salt);
var result_test = Convert.ToBase64String(result.GetBytes(32));
Console.Write("Key Test Result: ");
Console.WriteLine(result_test);
//IV Verification (Salt is Using same code)
var result_test = Convert.ToBase64String(result.GetBytes(16));
Console.Write("IV Test Result: ");
Console.WriteLine(result_test);
//Key Verification
/* print Salt */
String base64 = Base64.getEncoder().encodeToString(saltBytes);
System.out.println("Salt Result : " + base64);
/* print Key */
String result_test = Base64.getEncoder().encodeToString(key);
System.out.println("Key Test Result : " + result_test);
/* print generated Key */
System.out.println("Secret Key Result : " + Base64.getEncoder().encodeToString(secret.getEncoded()));
//IV Verification (Salt is Using same code)
/* print IV */
String result_test = Base64.getEncoder().encodeToString(iv);
System.out.println("IV Test Result : " + result_test);
/* print generated IV */
System.out.println("IV Result : " + Base64.getEncoder().encodeToString(ivSpec.getIV()));
更新
c＃.netframework 4.5 / Java8修改了@Topaco所說的並確認它運行良好。
我想非常感謝@Topaco和@ Gusto2，我將對已經修改過的部分進行更改，就像@Gusto2所說的那樣！
while((read = input.read(buffer)) != -1){
output.write(c.update(buffer, 0, read));
}
byte[] deryptedBytes = c.doFinal(buffer)
您正在解密文件的輸入，然后您使用相同的密碼實例將最后讀取的塊（再次）解密為單獨的數組而不是文件
快速解決：
while((read = input.read(buffer)) != -1){
output.write(c.update(buffer, 0, read));
}
output.write(c.doFinal()); // write the padded block
如果你想創建並打印一個解密的String，你需要創建一個新的Cipher實例（或者它可能足以重新初始化實例，我不確定）假設緩沖區包含整個輸入
c.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);
// assuming the buffer contains the whole input again
byte[] deryptedBytes = c.doFinal(buffer); // decrypting the whole file again
正確的方法：
IV用於安全地重復使用相同的加密密鑰進行多次加密。 因此，如果您的密鑰不是隨機的，您應該為每個加密生成新的隨機IV（並沿着密文傳遞IV，最常見的是前置）。 否則加密在語義上不安全，您可以為兩個pad攻擊創建開放。 因此從密鑰中導出IV可能不是很安全。
我建議使用沿密文傳遞的任何MAC（認證碼）來確保完整性（例如HMAC）
你還在將所有文件輸入完全讀入內存，這對於REALLY LARGE文件無效。 您可以將緩沖區初始化為任意長度（幾MB？）並將輸入文件處理為chunked
1）在C＃ Encrypt -method中，首先加密純文本，然后加密Base64編碼。 因此，在解密過程中，數據必須首先進行Base64解碼然后解密。 目前，這是以錯誤的順序處理的，即首先解密數據然后解碼。 因此，在Java fileProcessing -method中替換
while((read = input.read(buffer)) != -1){
output.write(c.update(buffer, 0, read));
}
同
while((read = input.read(buffer)) != -1) {
byte[] bufferEncoded = buffer;
if (read != buffer.length) {
bufferEncoded = Arrays.copyOf(buffer, read);
}
byte[] bufferDecoded = Base64.getDecoder().decode(bufferEncoded);
output.write(c.update(bufferDecoded));
}
2）沒有必要將buffer （或bufferDecoded ）傳遞給doFinal -method，因為這已經在update -method中完成了。 從而，
byte[] deryptedBytes = c.doFinal(buffer);
必須更換
output.write(c.doFinal());
3）由於Base64解碼已在1）中在try -block中完成，因此必須刪除doFinal -statement之后的所有行。 總的來說，這導致了
try {
input = new BufferedInputStream(new FileInputStream(source));
output = new BufferedOutputStream(new FileOutputStream(dest));
byte[] buffer = new byte[input.available()];
int read = -1;
while((read = input.read(buffer)) != -1) {
byte[] bufferEncoded = buffer;
if (read != buffer.length) {
bufferEncoded = Arrays.copyOf(buffer, read);
}
byte[] bufferDecoded = Base64.getDecoder().decode(bufferEncoded);
output.write(c.update(bufferDecoded));
}
output.write(c.doFinal());
}
4）緩沖區的大小必須是4的倍數，以確保正確的Base64解碼。 因此，更換更可靠
byte[] buffer = new byte[input.available()];
同
byte[] buffer = new byte[4 * (input.available() / 4)];
只要在一個塊中讀取數據（無法保證，請參閱https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/io/InputStream。 html #available（） ）沒有問題。 但是，如果以幾個塊讀取數據，則讀取4個字節的倍數很重要，否則Base64解碼將失敗。 通過使用不是4的倍數的緩沖區大小可以很容易地證明這一點。如果針對較大的文件明確定義了緩沖區大小，則還必須考慮這一點。
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