这是我们的场景：我们有巨大的加密文件，大小达到几个千兆字节，如果我们读取到文件结尾，我们可以正确地解密它们。但是当我们在读取文件时检测到某些标志后，我们会停止读取并调用reader.Close()函数时，会抛出一个CryptographicException异常："Padding is invalid and cannot be removed."。 我有一个小型的控制台应用程序来重现这种行为，要测试它只需运行它，它将在你的C:\驱动器上创建一个文件，并在按任意键时逐行读取，按下'q'键时停止。
using System;
using System.IO;
using System.Security.Cryptography;
namespace encryptSample
{
class Program
{
static void Main(string[] args)
{
var transform = CreateCryptoTransform(true);
// first create encrypted file
using (FileStream destination = new FileStream("c:\\test_enc.txt", FileMode.OpenOrCreate, FileAccess.Write, FileShare.ReadWrite))
{
using (CryptoStream cryptoStream = new CryptoStream(destination, transform, CryptoStreamMode.Write))
{
using (StreamWriter source = new StreamWriter(cryptoStream))
{
for (int i = 0; i < 1000; i++)
{
source.WriteLine("This is just random text to fill the file and show what happens when I stop reading in the middle - " + i);
}
// Also tried this line, but is the same with or without it
cryptoStream.FlushFinalBlock();
}
}
}
StreamReader reader;
ICryptoTransform transformDec;
CryptoStream cryptoStreamReader;
transformDec = CreateCryptoTransform(false);
FileStream fileStream = new FileStream("c:\\test_enc.txt", FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
cryptoStreamReader = new CryptoStream(fileStream, transformDec, CryptoStreamMode.Read);
reader = new StreamReader(cryptoStreamReader);
while (Console.In.ReadLine() != "q")
{
Console.WriteLine(reader.ReadLine());
}
try
{
cryptoStreamReader.Close();
reader.Close();
reader.Dispose();
}
catch (CryptographicException ex)
{
if (reader.EndOfStream)
throw;
}
}
private static ICryptoTransform CreateCryptoTransform(bool encrypt)
{
byte[] salt = new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }; // Must be at least eight bytes. MAKE THIS SALTIER!
const int iterations = 1042; // Recommendation is >= 1000.
const string password = "123456";
AesManaged aes = new AesManaged();
aes.BlockSize = aes.LegalBlockSizes[0].MaxSize;
aes.KeySize = aes.LegalKeySizes[0].MaxSize;
// NB: Rfc2898DeriveBytes initialization and subsequent calls to GetBytes must be eactly the same, including order, on both the encryption and decryption sides.
Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(password, salt, iterations);
aes.Key = key.GetBytes(aes.KeySize / 8);
aes.IV = key.GetBytes(aes.BlockSize / 8);
aes.Mode = CipherMode.CBC;
aes.Padding = PaddingMode.PKCS7;
ICryptoTransform transform = encrypt ? aes.CreateEncryptor(aes.Key, aes.IV) : aes.CreateDecryptor(aes.Key, aes.IV);
return transform;
}
}
}
在我们原始的类中，在Dispose()期间我们执行reader.Close。我的问题是，检查reader.EndOfStream是否为false然后捕获CryptographicException是否有效？或者加密/解密方法存在问题？也许我们漏掉了什么。
此致！