“填充无效并且不能被去除”使用AesManaged [英] "Padding is invalid and cannot be removed" using AesManaged

问题描述

我正在尝试使用AesManaged进行简单的加密/解密，但是当尝试关闭解密流时，我会继续遇到异常。这里的字符串被正确加密和解​​密，然后在Console.WriteLine打印正确的字符串后，我得到CryptographicException填充无效并且无法删除。

I'm trying to get simple encryption/decryption working with AesManaged, but I keep getting an exception when trying to close the decryption stream. The string here gets encrypted and decrypted correctly, and then I get the CryptographicException "Padding was invalid and cannot be removed" after Console.WriteLine prints the correct string.

任何想法？

MemoryStream ms = new MemoryStream();
byte[] rawPlaintext = Encoding.Unicode.GetBytes("This is annoying!");

using (Aes aes = new AesManaged())
{
  aes.Padding = PaddingMode.PKCS7;
  aes.Key = new byte[128/8];
  aes.IV = new byte[128/8];

  using (CryptoStream cs = new CryptoStream(ms, aes.CreateEncryptor(),
                                            CryptoStreamMode.Write))
  {
    cs.Write(rawPlaintext, 0, rawPlaintext.Length);
    cs.FlushFinalBlock();
  }

  ms = new MemoryStream(ms.GetBuffer());
  using (CryptoStream cs = new CryptoStream(ms, aes.CreateDecryptor(),
                                            CryptoStreamMode.Read))
  {
    byte[] rawData = new byte[rawPlaintext.Length];
    int len = cs.Read(rawData, 0, rawPlaintext.Length);
    string s = Encoding.Unicode.GetString(rawData);
    Console.WriteLine(s);
  }
}

推荐答案

窍门是使用 MemoryStream.ToArray（）。
我也改变了你的代码，以便在加密和解密时使用 CryptoStream 来编写。而且您不需要明确地调用 CryptoStream.FlushFinalBlock（），因为您使用 using（）语句，并且将在 Dispose（）发生flush。以下为我工作。

The trick is to use MemoryStream.ToArray(). I also changed your code so that it uses the CryptoStream to Write, in both encrypting and decrypting. And you don't need to call CryptoStream.FlushFinalBlock() explicitly, because you have it in a using() statement, and that flush will happen on Dispose(). The following works for me.

byte[] rawPlaintext = System.Text.Encoding.Unicode.GetBytes("This is all clear now!");

using (Aes aes = new AesManaged())
{
    aes.Padding = PaddingMode.PKCS7;
    aes.KeySize = 128;          // in bits
    aes.Key = new byte[128/8];  // 16 bytes for 128 bit encryption
    aes.IV = new byte[128/8];   // AES needs a 16-byte IV
    // Should set Key and IV here.  Good approach: derive them from 
    // a password via Cryptography.Rfc2898DeriveBytes 
    byte[] cipherText= null;
    byte[] plainText= null;

    using (MemoryStream ms = new MemoryStream())
    {
        using (CryptoStream cs = new CryptoStream(ms, aes.CreateEncryptor(), CryptoStreamMode.Write))
        {
            cs.Write(rawPlaintext, 0, rawPlaintext.Length);
        }

        cipherText= ms.ToArray();
    }


    using (MemoryStream ms = new MemoryStream())
    {
        using (CryptoStream cs = new CryptoStream(ms, aes.CreateDecryptor(), CryptoStreamMode.Write))
        {
            cs.Write(cipherText, 0, cipherText.Length);
        }

        plainText = ms.ToArray();
    }
    string s = System.Text.Encoding.Unicode.GetString(plainText);
    Console.WriteLine(s);
}

另外，我想你知道你会想明确地设置模式，并使用 System.Security.Cryptography.Rfc2898DeriveBytes 以导出密钥和/或从密码和盐。

Also, I guess you know you will want to explicitly set the Mode of the AesManaged instance, and use System.Security.Cryptography.Rfc2898DeriveBytes to derive the Key and IV from a password and salt.

另请参见：

- AesManaged

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