SecurityException from using HttpWebRequest cross-domain in Silverlight 4

Question

I'm trying to write a function in my Silverlight app that requests a particular page that doesn't exist on the same domain as where my Silverlight app is hosted.

For example:

Silverlight App: http://www.mysilverlightsite.com/
Target Page: http://www.mysite.com/MyPage.aspx

However, this generates a 'SecurityException':

{System.Security.SecurityException: Security error. at System.Net.Browser.ClientHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult) at System.Net.Browser.ClientHttpWebRequest.EndGetResponse(IAsyncResult asyncResult) ...}

From what I understand, this is related to cross-domain requests being restricted, and found some posts that mentioned that this article (http://msdn.microsoft.com/en-us/library/cc197955(VS.95).aspx) might be related.

Here's my code:

public static void CheckPageContentsAsync(CheckPageContentsCallback callback, DependencyObject uiObject)
{
    bool result = false;
    try
    {
        HttpWebRequest request = WebRequest.CreateHttp("http://www.mysite.com/MyPage.aspx");
        request.BeginGetResponse((asyncHandle) =>
        {
            try
            {
                uiObject.Dispatcher.BeginInvoke(new VoidDelegate(() =>
                {

                    HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asyncHandle);
                    using (StreamReader sr = new StreamReader(response.GetResponseStream()))
                    {
                        string content = sr.ReadToEnd();
                        if (content.Contains("Value"))
                        {
                            result = true;
                        }

                        if (callback != null)
                        {
                            callback.Invoke(result);
                        }
                    }
                }), null);
            }
            catch (Exception excep)
            {
                throw new Exception("Failed to process response.", excep);
            }
        }, null);
    }
    catch(Exception excep2)
    {
        throw new Exception("Failed to generate request.", excep2);
    }
}

Haven't been able to make much sense of the applicability of the "clientaccesspolicy.xml" or "crossdomain.xml" files as a solution.

Can anyone explain clearly how I modify my app, or the web server I'm requesting from, to resolve this issue?

Adi · Accepted Answer · 2011-04-01 23:00:06Z

1

I use to copy this file in the root of my app:

<cross-domain-policy>
    <allow-access-from domain="*.*" headers="SOAPAction"/>
    <allow-http-request-headers-from domain="*.*" headers="SOAPAction"/> 
    <site-control permitted-cross-domain-policies="master-only"/>
</cross-domain-policy>

Name it crossdomain.xml.

answered Apr 1, 2011 at 23:00

Adi

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2 Comments

David Elner Over a year ago

Where is said "root of app"? Is this stored next to the XAP file? Root of the site that serves the XAP? Root of the site where I want to request from?

Adi Over a year ago

The permission must be granted by the server that needs to respond to the Silverlight's requests, so it must stay on that server, not the server that will serve the .xap file. Root means the domain's root, like: www.mydomain.com/crossdomain.xml

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