Try/Catch/Final 使用加密资源

Question

我的网站上有以下代码。它将 URL 查询作为名为 commandencrypted 的字符串。我有一个 try/catch/finally 块，它将加密的命令复制到内存流，然后将其解密回字符串。如果 try 块中出现任何错误，它们将在 catch 块中处理。但是，我想确保在 finally 块中关闭所有使用的资源。当提供无效的 URL 查询命令时，我在尝试关闭 csencryptedcommand CryptoStream 时收到异常。异常详情跟在代码后面。

    // Resources used for storing and decrypting the encrypted client command
    MemoryStream msencryptedcommand = null;
    RijndaelManaged rmencryptedcommand = null;
    CryptoStream csencryptedcommand = null;
    StreamReader srdecryptedcommand = null;
    MemoryStream msdecryptedcommand = null;

    try
    {
        // Copy the encrypted client command (where two characters represent a byte) to a memorystream
        msencryptedcommand = new MemoryStream();
        for (int i = 0; i < encryptedcommand.Length; )
        {
            msencryptedcommand.WriteByte(Byte.Parse(encryptedcommand.Substring(i, 2), NumberStyles.HexNumber));
            i = i + 2;
        }
        msencryptedcommand.Flush();
        msencryptedcommand.Position = 0;

        // Define parameters used for decryption
        byte[] key = new byte[] { //bytes hidden// };
        byte[] iv = new byte[] { //bytes hidden// };
        rmencryptedcommand = new RijndaelManaged();
        csencryptedcommand = new CryptoStream(msencryptedcommand, rmencryptedcommand.CreateDecryptor(key, iv), CryptoStreamMode.Read);
        msdecryptedcommand = new MemoryStream();

        // Decrypt the client command
        int decrytptedbyte;
        while ((decrytptedbyte = csencryptedcommand.ReadByte()) != -1)
        {
            msdecryptedcommand.WriteByte((byte)decrytptedbyte);
        }

        // Store the decrypted client command as a string
        srdecryptedcommand = new StreamReader(msdecryptedcommand);
        srdecryptedcommand.BaseStream.Position = 0;
        string decryptedcommand = srdecryptedcommand.ReadToEnd();
    }
    catch (Exception ex)
    {
        ErrorResponse("Invalid URL Query", context, ex.ToString());
        return;
    }
    finally
    {
        // If any resources were used, close or clear them
        if (srdecryptedcommand != null)
        {
            srdecryptedcommand.Close();
        }

        if (msdecryptedcommand != null)
        {
            msdecryptedcommand.Close();
        }

        if (csencryptedcommand != null)
        {
            csencryptedcommand.Close();
        }

        if (rmencryptedcommand != null)
        {
            rmencryptedcommand.Clear();
        }

        if (msencryptedcommand != null)
        {
            msencryptedcommand.Close();
        }
    }

发生以下未处理的异常：System.Security.Cryptography.CryptographicException：要解密的数据长度无效。在 System.Security.Cryptography.RijndaelManagedTransform.TransformFinalBlock(Byte[] inputBuffer, Int32 inputOffset, Int32 inputCount) 在 System.Security.Cryptography.CryptoStream.FlushFinalBlock() 在 System.Security.Cryptography.CryptoStream.Dispose(Boolean disposing) 在 System update.ashx 中 dongleupdate.ProcessRequest(HttpContext context) 处的 .IO.Stream.Close()：System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() 处 System.Web.HttpApplication 的第 92 行。 ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) URL Referrer: User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/30.0.1599.69 Safari/537.36 Request URL: update.ashx?aa

编辑：

我将代码更改为使用 using 语句。这也是确保关闭所有资源的有效方法吗？

    try
    {
        // Copy the encrypted client command (where two characters represent a byte) to a memorystream
        using (MemoryStream msencryptedcommand = new MemoryStream())
        {
            for (int i = 0; i < encryptedcommand.Length; )
            {
                msencryptedcommand.WriteByte(Byte.Parse(encryptedcommand.Substring(i, 2), NumberStyles.HexNumber));
                i = i + 2;
            }
            msencryptedcommand.Flush();
            msencryptedcommand.Position = 0;

            // Define parameters used for decryption
            byte[] key = new byte[] { //bytes hidden// };
            byte[] iv = new byte[] { //bytes hidden// };
            using (RijndaelManaged rmencryptedcommand = new RijndaelManaged())
            {
                using (CryptoStream csencryptedcommand = new CryptoStream(msencryptedcommand, rmencryptedcommand.CreateDecryptor(key, iv), CryptoStreamMode.Read))
                {
                    using (MemoryStream msdecryptedcommand = new MemoryStream())
                    {

                        // Decrypt the client command
                        int decrytptedbyte;
                        while ((decrytptedbyte = csencryptedcommand.ReadByte()) != -1)
                        {
                            msdecryptedcommand.WriteByte((byte)decrytptedbyte);
                        }

                        // Store the decrypted client command as a string
                        using (StreamReader srdecryptedcommand = new StreamReader(msdecryptedcommand))
                        {
                            srdecryptedcommand.BaseStream.Position = 0;
                            string decryptedcommand = srdecryptedcommand.ReadToEnd();
                        }
                    }
                }
            }
        }
    }
    catch (Exception ex)
    {
        ErrorResponse("Invalid URL Query", context, ex.ToString());
        return;
    }

Answer 1

将您的CryptoStream 包装在using 块中，然后它将自动关闭并通过Dispose Pattern 为您处理，如下所示：

using(csencryptedcommand = new CryptoStream(msencryptedcommand, 
    rmencryptedcommand.CreateDecryptor(key, iv), CryptoStreamMode.Read))
{
    // Do things with crypto stream here
}

阅读using Statement (C# Reference) 文档了解更多信息。

更新：

使用Reflector，这里是CryptoStream的Dispose方法的代码：

protected override void Dispose(bool disposing)
{
    try
    {
        if (disposing)
        {
            if (!this._finalBlockTransformed)
            {
                this.FlushFinalBlock();
            }
            this._stream.Close();
        }
    }
    finally
    {
        try
        {
            this._finalBlockTransformed = true;
            if (this._InputBuffer != null)
            {
                Array.Clear(this._InputBuffer, 0, this._InputBuffer.Length);
            }
            if (this._OutputBuffer != null)
            {
                Array.Clear(this._OutputBuffer, 0, this._OutputBuffer.Length);
            }
            this._InputBuffer = null;
            this._OutputBuffer = null;
            this._canRead = false;
            this._canWrite = false;
        }
        finally
        {
            base.Dispose(disposing);
        }
    }
}

注意：如您所见，通过此行有一个显式调用来关闭流：

this._stream.Close();

Answer 2

我认为您使用的所有对象都实现了 IDisposable，所以如果我是您，我会将它们全部包装在 using 语句中，以便它们会自动为您清理，即

using(msencryptedcommand = new MemoryStream())
{
    ....
}