使用itemdatabound在转发器项目中解密

Question

I am displaying image using the asp repeater and i wish to encrypt it but i have no idea how to decrypt everytime the repeater fire a item

//client side <asp:Repeater ID="Repeater1" runat="server" OnItemCommand="Repeater1_ItemCommand" OnItemDataBound="Repeater1_ItemDataBound" >

`//server side
//decrypt method
private void DecryptFile(string inputFile, string outputFile)
    {

        {
            string password = @"myKey123"; // Your Key Here

            UnicodeEncoding UE = new UnicodeEncoding();
            byte[] key = UE.GetBytes(password);

            FileStream fsCrypt = new FileStream(inputFile, FileMode.Open);

            RijndaelManaged RMCrypto = new RijndaelManaged();

            CryptoStream cs = new CryptoStream(fsCrypt,
                RMCrypto.CreateDecryptor(key, key),
                CryptoStreamMode.Read);

            FileStream fsOut = new FileStream(outputFile, FileMode.Create);

            int data;
            while ((data = cs.ReadByte()) != -1)
                fsOut.WriteByte((byte)data);

            fsOut.Close();
            cs.Close();
            fsCrypt.Close();

        }
    }

`

protected void Repeater1_ItemDataBound(object source, RepeaterCommandEventArgs e)
        {
            if (e.CommandName =="openimage")
            {
                string[] commandArgs = e.CommandArgument.ToString().Split(new char[] { ',' });
                DecryptFile(commandArgs[0], commandArgs[0]);

            }
        }

when i try to run it, it gave me the error CS0123: No overload for 'Repeater1_ItemDataBound' matches delegate 'System.Web.UI.WebControls.RepeaterItemEventHandler'

Please help me as i am new to c#

Answer 1

The method signature on your event handler is incorrect. You need to change RepeaterCommandEventArgs to RepeaterItemEventArgs .

protected void Repeater1_ItemDataBound(object source, RepeaterItemEventArgs e)
{
}

That will fix your error, however with what you're trying to do I'm not sure that this would be a good way to display the decrypted image. What I recommend is creating a generic handler that will decrypt your image on the fly by passing in the id, once the id is passed you can decrypt and write out to the screen.

public class DisplayImage : IHttpHandler
{

    /// <summary>
    /// Enables processing of HTTP Web requests by a custom HttpHandler that implements the <see cref="T:System.Web.IHttpHandler" /> interface.
    /// </summary>
    /// <param name="context">An <see cref="T:System.Web.HttpContext" /> object that provides references to the intrinsic server objects (for example, Request, Response, Session, and Server) used to service HTTP requests.</param>
    public void ProcessRequest(HttpContext context)
    {
        if (!this.HasAccess())
        {
            context.Response.End();
            return;
        }

        string requestFileName = context.Request.QueryString["FileName"];

        DecryptFile(requestFileName, context);
    }

    /// <summary>
    /// Gets a value indicating whether another request can use the <see cref="T:System.Web.IHttpHandler" /> instance.
    /// </summary>
    /// <value><c>true</c> if this instance is reusable; otherwise, <c>false</c>.</value>
    /// <returns>true if the <see cref="T:System.Web.IHttpHandler" /> instance is reusable; otherwise, false.</returns>
    public bool IsReusable
    {
        get
        {
            return false;
        }
    }

    /// <summary>
    /// Determines whether the user has access to display an image.
    /// </summary>
    /// <returns><c>true</c> if this instance has access; otherwise, <c>false</c>.</returns>
    private bool HasAccess()
    {
        // Check if user is logged in and has permissions
        // to do the decryption
        // use your own logic here
        return true;
    }

    /// <summary>
    /// Decrypts the file and outputs to the response buffer
    /// </summary>
    /// <param name="inputFile">The input file.</param>
    /// <param name="context">The context.</param>
    private void DecryptFile(string inputFile, HttpContext context)
    {
        if (PathTraversalCheck(inputFile))
        {
            context.Response.End();
            return;
        }

        // get the base directory
        inputFile = Path.Combine(ConfigurationManager.AppSettings["filedirectory"], inputFile);

        if (!File.Exists())
        {
            context.Response.End();
            return;
        }

        string password = @"myKey123"; // Your Key Here

        UnicodeEncoding UE = new UnicodeEncoding();
        byte[] key = UE.GetBytes(password);

        using (FileStream encryptedFile = new FileStream(inputFile, FileMode.Open))
        {
            RijndaelManaged rijndael = new RijndaelManaged();

            using (MemoryStream output = new MemoryStream())
            {
                using (CryptoStream cryptoStream = new CryptoStream(encryptedFile, rijndael.CreateDecryptor(key, key), CryptoStreamMode.Read))
                {
                    // write to the memory stream
                    var buffer = new byte[1024];
                    var read = cryptoStream.Read(buffer, 0, buffer.Length);
                    while (read > 0)
                    {
                        output.Write(buffer, 0, read);
                        read = cryptoStream.Read(buffer, 0, buffer.Length);
                    }

                    cryptoStream.Flush();

                    // output to the response buffer
                    context.Response.ContentType = "image/jpeg";
                    context.Response.BinaryWrite(output.ToArray());
                }
            }

        }
    }

    /// <summary>
    /// Checks for a path traversal attack
    /// </summary>
    /// <param name="inputFile">The input file.</param>
    /// <returns>System.String.</returns>
    private bool PathTraversalCheck(string inputFile)
    {
        if (inputFile.Contains(".") || inputFile.Contains('\\') || inputFile.Contains('/'))
        {
            return true;
        }

        return false;
    }
}

In your repeater you simply have to put the an img tag with the src set to the handler.

<ItemTemplate>
    <img src="DisplayImage.ashx?FIleName=<%# DataBinder.Eval(Container.DataItem, "FileName" )%>" />
</ItemTemplate>

Something else I would change as well is I would not store my key in the source code, that's easily readable by decompiling the dlls. Instead you should store it in your web.config and encrypt the web.config. Check out http://msdn.microsoft.com/library/dtkwfdky.aspx for instructions.

Answer 2

You need to correct repeater events:

void Repeater1_ItemDataBound(Object Sender, RepeaterItemEventArgs e) {

}

Also, for handling event inside repeater, you should move your code to Repeater1__ItemCommand event.

void Repeater1__ItemCommand(Object Sender, RepeaterCommandEventArgs e) {       
        if (e.CommandName =="openimage")
        {
            string[] commandArgs = e.CommandArgument.ToString().Split(new char[] { ',' });
            DecryptFile(commandArgs[0], commandArgs[0]);

        }
}