使用加密资源尝试/捕获/最后

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,将加密的命令复制到一个MemoryStream,然后解密回一个字符串.如果发生在try块中的任何错误,他们在catch块处理.不过,我要确保所使用的任何资源finally块中被关闭.当提供无效的URL查询命令,我收到一个异常,而试图关闭csencryptedcommand CryptoStream的.例外细节遵循代码.

    // 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();
        }
    }

以下未处理的异常:System.Security.Cryptography.CryptographicException:数据的长度来解密是无效的.在System.Security.Cryptography.RijndaelManagedTransform.TransformFinalBlock(字节[] INPUTBUFFER,的Int32 inputOffset,的Int32 inputCount)在System.Security.Cryptography.CryptoStream.FlushFinalBlock()在System.Security.Cryptography.CryptoStream.Dispose(布尔处置)在系统update.ashx中的dongleupdate.ProcessRequest(HttpContext context)中的.IO.Stream.Close():位于System.Web.HttpApplication的System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()的第92行. ExecuteStep(IExecutionStep step,Boolean&completedSynchronously)URL Referrer:用户代理:Mozilla/5.0(Windows NT 6.1; WOW64)AppleWebKit/537.36(KHTML,如Gecko)Chrome/30.0.1599.69 Safari/537.

编辑:

我将代码更改为使用语句.这也是确保所有资源都关闭的有效方法吗？

    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

包装你CryptoStream的using块,然后它会通过自动关闭和处置你Dispose Pattern,就像这样:

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

有关更多信息,请阅读Statement(C#参考)文档.

更新:

使用反射器,这里是代码CryptoStream的Dispose方法:

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,有一条显式调用通过此行关闭流:

this._stream.Close();