Exclude specific path from WIF authorization in a ASP.NET MVC 4 project

Question

We have successfully configured windows identity foundation (WIF) in our ASP.NET 4.5 MVC 4 project with the help of the Identity and Access... extension for Visual Studio 2012. But are unable to exclude a specific path from authorization to allow anonymous access.

When we access our default route (i.e. /Home), the passive redirection will redirect us to the configured issuer Uri. This is currect. But now assume we want to exclude Path /Guest from STS Authentication so that everybody can access http://ourhost/Guest without beeing routed to the STS issuer. Only static documents are located there.

Snippets from Web.config:

<system.identityModel>
  <identityConfiguration>
    <audienceUris>
      <add value="http://ourhost/" />
    </audienceUris>
    <issuerNameRegistry type="System.IdentityModel.Tokens.ConfigurationBasedIssuerNameRegistry, System.IdentityModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
      <trustedIssuers>
        <add thumbprint="9B74****40D0" name="OurSTS" />
      </trustedIssuers>
    </issuerNameRegistry>
    <certificateValidation certificateValidationMode="None" />
  </identityConfiguration>
</system.identityModel>
<system.identityModel.services>
  <federationConfiguration>
    <cookieHandler requireSsl="false" />
    <wsFederation passiveRedirectEnabled="true" issuer="http://oursts/Issue" realm="http://ourhost/" reply="http://ourhost/" requireHttps="false" />
  </federationConfiguration>
</system.identityModel.services>

Further we have...

<system.webServer>
  <!-- ... -->
  <modules runAllManagedModulesForAllRequests="true">
    <add name="WSFederationAuthenticationModule" type="System.IdentityModel.Services.WSFederationAuthenticationModule, System.IdentityModel.Services, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" preCondition="managedHandler" />
    <add name="SessionAuthenticationModule" type="System.IdentityModel.Services.SessionAuthenticationModule, System.IdentityModel.Services, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" preCondition="managedHandler" />
    <remove name="FormsAuthentication" />
  </modules>
</system.webServer>

and finally:

<system.web>
  <!-- ... -->
  <authentication mode="None" />
</system.web>

We tried the following without success:

<location path="~/Guest"> <!-- also "/Guest" is not working -->
  <system.web>
    <authorization>
      <allow users="*" />
    </authorization>
  </system.web>
</location>

We also tried to put a small Web.config file into this folder, without success. No matter which Uri we locate to in the browser, we're always redirected.

What is the proper way to accomplish this?

EDIT

Removed the previous "accepted answered", set "accepted answer" to Eugenios answer as this is the more useful reply.

Answer 1

In an MVC app you typically define access through the [Authorize] attribute in controllers and actions.

Just remove from web.config:

<system.web>
     <authorization>
        <deny users="?" />
      </authorization>

Note: this is usually added automatically by the "Add STS Reference" wizard in VS2010

It seems that the behaviour is exactly the same on VS2012 and the new tools. I just created a brand new MVC4 app. Ran the "Identity and Access..." tool with a local config STS (left all defaults).

It did add this fragment to the web.config:

<authorization>
  <deny users="?" />
</authorization>

I removed it and added [Authorize] to the About controller action:

[Authorize]
public ActionResult About()
{
    ViewBag.Message = "Your app description page.";

    return View();
}

When I click on the "About" link, then I get redirected to the STS. Everything else works with anonymous access.

Note:

You have some control on this too in the wizard (see the "Configuration" page of the wizard).

Answer 2

I can not get [Authorize] to work - it is not doing the redirect to my STS, and I am sure it is something I am missing. I did discover how to solve for the original ask, though.

In global.asax:

    protected void Application_Start()
    {
        ... config stuff ...
        FederatedAuthentication.WSFederationAuthenticationModule.AuthorizationFailed += WSFederationAuthenticationModule_AuthorizationFailed;
    }

and then:

    void WSFederationAuthenticationModule_AuthorizationFailed(object sender, AuthorizationFailedEventArgs e)
    {
        // Do path/file detection here
        if (Request.Path.Contains("/Content/") || Request.Path.Contains("/Scripts/"))
        {
            e.RedirectToIdentityProvider = false;
        }
    }

Answer 3

I was in the same situation as Thomas. In my case, I was testing/using IISExpress locally.

Eugenio's answer almost got me working, with one added requirement. I had to set the "Anonymous Authentication" in my MVC Project Property to "Enabled."

This was either disabled by default or possibly set that way when using the VS 2012 "Identity and Access..." tooling.

So, to recap, there was no code or special attributes to write/maintain.

My csproj file contains:

<IISExpressAnonymousAuthentication>enabled</IISExpressAnonymousAuthentication>

My web.config contains:

<system.web>
    <authentication mode="None" />
</system.web>

<system.web>
    <authorization>
        <allow users="*" />
    </authorization>
</system.web>

<system.webServer>
    <modules>
        <remove name="FormsAuthentication" />
        <add name="WSFederationAuthenticationModule" type="System.IdentityModel.Services.WSFederationAuthenticationModule, System.IdentityModel.Services, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" preCondition="managedHandler" />
        <add name="SessionAuthenticationModule" type="System.IdentityModel.Services.SessionAuthenticationModule, System.IdentityModel.Services, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" preCondition="managedHandler" />
    </modules>
</system.webServer>

<system.identityModel.services>
    <federationConfiguration>
        <wsFederation passiveRedirectEnabled="true" issuer="https://REMOVED.accesscontrol.windows.net/v2/wsfederation" realm="urn:REMOVED" requireHttps="false" />
    </federationConfiguration>
</system.identityModel.services>

And, I add the standard [Authorize] attribute to controller actions that I want to be defended by WIF:

[Authorize]
public ActionResult About()
{
....
}

Answer 4

What finally pointed me into the right direction was an older blog post which explains how to protect a specific controller or area of the page. In combination with global filters I'm almost there.

It seems like the key is not to use the passiveRedirectEnabled="true" option but set it to false. Only then you have the full control over the authentication process, but would need to trigger the passive redirection yourself then, using the SignInRequestMessage class (which is not a big deal).

Better solutions with less code required are welcome.

EDIT

Removed "accepted answered" state for this, set "accepted answer" to Eugenios anwer as this is the more useful reply.