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ASP.NET Support Voice Column
SSL Termination and ASP.NETTo customize this column to your needs, we want to invite you to submit your ideas about topics that interest you and issues that you want to see addressed in future Knowledge Base articles and Support Voice columns. You can submit your ideas and feedback using the Ask For It
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Welcome to the ASP.NET Support Voice column! My name is Jerry Orman. I have been with Microsoft for over five years, and have spent most of my time focused on Web-related technologies such as Microsoft FrontPage and Microsoft SharePoint Products and Technologies. I've spent the last year working with Microsoft ASP.NET as a support engineer. This month, I'm going to talk about SSL Termination and ASP.NET. In particular, I want to focus on issues that result from a configuration of the server. We're going to take a look at SSL Termination and some side effects of this configuration on your application.
SSL Termination is a configuration in which the Web server running your code sends and receives traffic over HTTP, and there is a device between your Web server and your clients that encrypts and decrypts the data. In this configuration, the clients are sending and receiving HTTPS traffic. The SSL Termination configuration is similar to the following:
Client <— HTTPS —>SSL device <— HTTP —> Web serverNow let's go over two issues that come up in Microsoft ASP.NET 2.0 with this configuration, and some ways to work around the behavior.
Issue 1When you hover over a menu item in the ASP.NET 2.0 Menu control, you get the following error message:
The application is supposed to be secure, you're using the SSL protocol, and you have not added any controls that are rendering an absolute path back to an HTTP address. What's up with this message?
This page contains both secure and nonsecure items. Do you want to display the nonsecure items?
(http://support.microsoft.com/kb/837850/ )You receive a "This page contains both secure and nonsecure items" message when you click Explorer View in a document library in Windows SharePoint Services or in SharePoint Team Services from Microsoft
Ideally, you would have the menu in a MasterPage class or a UserControl class, and could add this code just one time.
Issue 2You may find that, when you have the requireSSL attribute of the <forms> element set to true, the server responds with repeated redirects to the FormsAuthentication login page. This is caused by a change in the way the FormsAuthenticationModule method handles the requireSSL attribute. If you set the requireSSL attribute to true, the FormsAuthenticationModule method creates a cookie that has the secure attribute set. (This behavior is the same as in the .NET Framework 1.1.) When you use the secure attribute, the client will only pass the cookie to the server if the client is using SSL. This part is great, because the client is indeed using SSL. Let's assume you have a SecurePage.aspx page that anonymous users can't access. With the SSL protocol and the requireSSL attribute, you end up with the following traffic on an initial request to SecurePage.aspx:
—>Client makes a GET request for SecurePage.aspx .
<—Server responds with an HTTP 302 (Redirect) to the login page.
—>Client makes a GET request for Login.aspx.
<—Server responds with a 200 OK. The login page is rendered to client.
—>Client makes a POST request to Login.aspx.
<—Server responds with a 302 (Redirect) to SecurePage.aspx. Set Cookie header is sent with the secure attribute to the client.
—>Client makes a GET request to SecurePage.aspx. Cookie is passed because the client is using SSL.
<—Server responds with a 302 (Redirect) back to the login page.
You get the redirect in the last request because of a change in the FormsAuthenticationModule class. An additional check was added in ASP.NET 2.0 to determine whether the user is passing a secure cookie over a non-SSL request. ASP.NET 2.0 returns the FormsAuthenticationTicket class if the FormsAuthentication.RequireSSL property is set to false or if the Request.IsSecure attribute is set to true.
The request that the user is making is anonymous at this point because the server has not yet validated the user's credentials. As the request passes through the ASP.NET pipeline, the UrlAuthorizationModule class checks whether the user has access to the page. Since an anonymous user does not have access to a SecurePage.aspx page, the UrlAuthorizationModule class returns a 401 error message ("Access Denied"), which results in a redirect to the login page.
In order to avoid this behavior, you first have to remove the requireSSL attribute from the <forms> tag in the configuration file. Then you have to programmatically set the secure attribute on the FormsAuthentication cookie. The following code does this for you, for both the FormsAuthentication cookie and the Session cookie.
For more information about the Menu control, visit the following Microsoft Developer Network (MSDN) Web site:
http://msdn2.microsoft.com/en-us/library/2xt3t8a7(vs.80).aspxFor more information about the requireSSL attribute of the FormsAuthentication.RequireSSL property, visit the following MSDN Web site:
http://msdn2.microsoft.com/en-us/library/system.web.security.formsauthentication.requiressl.aspxFor more information about the IsSecure attribute of the HttpRequest.IsSecureConnection property, visit the following MSDN Web site:
http://msdn2.microsoft.com/en-us/library/system.web.httprequest.issecureconnection(vs.71).aspxFor more information about the FormsAuthenticationModule class, visit the following MSDN Web site:
http://msdn2.microsoft.com/en-us/library/system.web.security.formsauthenticationmodule.aspxFor more information about the UrlAuthorizationModule class, visit the following MSDN Web site:
I hope you find this information helpful when you're using SSL Termination and Microsoft ASP.NET. Remember, the Support Voice columns are for you! As always, feel free to submit ideas on topics that you want addressed in future columns or in the Knowledge Base using the Ask For It
Article ID: 910444 - Last Review: November 22, 2007 - Revision: 1.3
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