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Windows Azure Pack Authentication Part 3 – Using a Third Party IdP

by Steve Syfuhs / February 07, 2014 06:22 PM

In the previous installments of this series we looked at how Windows Azure Pack authenticates users and how it’s configured out of the box for federation. This time around we’re going to look at how you can configure federation with a third party IdP.

Microsoft designed Windows Azure Pack the right way. It supports federation with industry protocols out of the box. You can’t say that for many services, and you certainly can’t say that those services support it natively for all versions – more often than not you have to pay extra for it.

Windows Azure Pack supports federation, and actually uses it to authenticate users by default. This little fact makes it easy to federate to a 3rd party IdP.

If we searched around we will find lots of resources on federating to ADFS, as that’s Microsoft’s federation product, and there are a number of good (German content) walkthroughs on how you can get it working. If you want to use ADFS go read one or all of those articles as everything we talk about today will be about using a non-Microsoft federation service.

Before we begin though I’d like to point out that Microsoft does have some resources on using 3rd party IdPs, but unfortunately the information is a bit thin in some places.

Prerequisites

Federation is a complex beast and we should be clear about what is required to get it working. In no particular order you need the following:

  • STS that supports the WS-Federation (passive) protocol
  • STS that supports WS-Federation wrapped JSON Web Tokens (JWT)
  • Optional: STS that supports WS-Trust + JWT

If you plan to use the public APIs with federated accounts then you will need a STS that supports WS-Trust + JWT.

If you don’t have a STS that can support these requirements then you should really consider taking a look at ADFS, or if you’re looking for customization, Thinktecture Identity Server. Both are top notch IdPs (edit: insert pitch about the IdP my company builds and sells as well [edit-edit: our next version natively supports JWT] Winking smile -- sorry, this concludes the not-so-regularly-scheduled product placement).

Another option is to roll your own IdP. Don’t do this. No seriously, don’t. It’s a complicated mess. You’re way better off using the Thinktecture server and extending it to fit your needs.

Supposing though that you already have an IdP and want to support JWT though, here’s how we can do it. In this context the IdP is the overarching identity providing system and the STS is simply the service issuing tokens.

Skip this next section if you just want to see how to configure Windows Azure Pack. That’s the main part that’s lacking in the MSDN documentation.

JWT via IdentityModel

First off, you need to be using .NET 4.5, and you need to be using the the 4.5 IdentityModel stack. You can’t use the original 3.5 bits.

At this point I’m going to assume you’ve got a working IdP already. There are lots of articles out there explaining how to build one. We’re just going to mod the STS.

Before making any code changes though you need to add the JWT token handler, which is easily installed via Nuget (I Red heart Nuget):

PM> Install-Package System.IdentityModel.Tokens.Jwt

This will need to be added to the project that exposes your STS configuration class.

Next, we need to inject the token handler into the STS pipeline. This can easily be done by adding an entry to the web.config system.identityModel section:

Or if you want to hardcode it you can add it to your SecurityTokenServiceConfiguration class.

There are of course other (potentially better) ways you can add it in, but this serves our purpose for the sake of a sample.

By adding the JWT token handler into the STS pipeline we can begin issuing JWTs to any relying parties that request one. This poses a problem though because passive requests don’t have a requested token type tacked on. Active (WS-Trust) requests do, but not passive. So we need to specify that a JWT should be minted instead of a SAML token. This can be done in the GetScope method of the STS class.

All we really needed to do was specify the TokenType as WIF will use that to determine which token handler should be used to mint the token. We know this is the value to use because it’s exposed by the GetTokenTypeIdentifiers() method in the JWTSecurityTokenHandler class.

Did I mention the JWT library is open source?

So now at this point if we made a request for token to the STS we could receive a WS-Federation wrapped JWT.

If the idea of using a JWT instead of a SAML token appeals to you, you can configure your app to use the JWT token handler similar to Dominick’s sample.

If you were submitting a WS-Trust RST to the STS you could use client code along the lines of:

When the GetScope method is called the request.TokenType should be set to whatever you passed in at the client. For more information on service calls you can take a look at the whitepaper Claims-Based Identity in Windows Azure Pack (docx). A future installment of this series might have more information about using services.

Lastly, we need to sign the JWT. The only caveat to using the JWT token handler is that the minimum RSA key size is 2048 bits. If you’re using a key smaller than that then please upgrade it. We’re going to overlook the fact that the MSDN article shows how to bypass minimum key sizes. Seriously. Don’t do it. I don’t want to have to explain why (putting paranoia aside for a moment, 1024 is being deprecated by Windows and related services in the near future anyway).

Issuing Tokens to Windows Azure Pack

So now we’re at a point where we can mint a JWT token. The question we need to ask now is what claims should this token contain? Looking at Part 1 we see that the Admin Portal requires UPN and Group claims. The tenant portal only requires the UPN claim.

Lucky for us the JWT token handler is smart. It knows to transform certain known XML-token-friendly-claim-types to JWT friendly claim types. In our case we can use http://schemas.xmlsoap.org/ws/2005/05/identity/claims/upn in our ClaimsIdentity to map to the UPN claim, and http://schemas.xmlsoap.org/claims/Group to map to our Group claim.

Then we need to determine where to send the token, and who to address it to. Both the tenant and admin sites have Federation Metadata documents that specify this information for us. If you’ve got an IdP that can parse the metadata then all you need to do is point it to https://yourtenantsite/FederationMetadata/2007-06/FederationMetadata.xml for the tenant configuration or https://youradminsite/FederationMetadata/2007-06/FederationMetadata.xml for the admin configuration.

Of course, this information will also map up to the configuration elements we looked at in Part 2. That’ll tell us the Audience URI and the Reply To for both sites.

Finally we have everything we need to mint the token, address it, and send it on its way.

Configuring Windows Azure Pack to Trust your Token

The tokens been sent and once it hits either the tenant or admin site it’ll promptly be ignored and you’ll get an ugly error message saying “nope, not gonna happen, bub.”

We therefore need to configure Windows Azure Pack to trust our token. Looking at MSDN we see some somewhat useful information telling us what we need to modify, but frankly, its missing a bunch of information so we’re going to ignore it.

First things first: if your IdP publishes a Federation Metadata document then you can just configure everything via PowerShell:

You can replace the target “Admin” with “Tenant” if you want to configure the Tenant Portal. The only caveat with doing it this way is that the metadata document needs to be accessible from the server. I’ve submitted a feature request that they also support local file paths too; hopefully they listen! Since the parameter takes the full URL you can put the metadata document somewhere public if its not normally accessible. You will only need the metadata accessible while applying this configuration.

If the cmdlet completed successfully then you should be able to log in from your own IdP. That’s all there is to it for you. I would recommend seriously considering going this route instead of configuring things manually.

Otherwise, lets carry on.

Since we can’t import our federation metadata (since we probably don’t have any), we need to configure things manually. To do that we need to modify settings in the database.

Looking back to Part 2 we see all the configuration elements that enable our federated trust to the default IdPs. We’ll need to update a few settings across the Microsoft.MgmtSvc.Store and Microsoft.MgmtSvc.PortalConfigStore databases.

As per the MSDN documentation it says to modify the settings in the PortalConfigStore database. It’s wrong. It’s incomplete as that’s only part of the process.

The PortalConfigStore database contains the settings used by the Tenant and Admin Portals to validate and request tokens. We need to modify these settings to use our custom IdP. To do so locate the Authentication.IdentityProvider setting in the [Config].[Settings] table.  The namespace we need to choose is dependent on which site we want to configure. In our case we select the Admin namespace. As we saw last time it looks something like:

We need to substitute our STS information here. The Realm is whatever your STS issuer is, and the Endpoint is where ever your WS-Federation endpoint is located. The Certificate should be a base 64 encoded representation of your signing certificate (remember, just the public key).

In my experience I’ve had to do an IISRESET on the portals to get the settings refreshed. I might just be impatient though.

Once those values are replaced you can try logging in. You should be redirected to your IdP and if you issue the token properly it’ll hit the portal and you should be logged in. Unfortunately this’ll actually fail with a non-useful error message.

deadsession

Who can guess why? So far I’ve stated that the MSDN documentation is missing information. What have we missed? Hopefully if you’ve read the first two parts of this series you’re yelling at the screen telling me to get on with it already because you’ve caught on to what I’m saying.

We haven’t configured the API services to trust our STS! Oops.

With that being said, we now have proof that Windows Azure Pack flows the token to the services from the Portal and, more importantly, the services validate the token. Cool!

Anyway, now to configure the APIs. Warning: complicated.

In the Microsoft.MgmtSvc.Store database locate the Settings table and then locate the Authentication.IdentityProvider.Secondary element in the AdminAPI namespace. We need to update it with the exact same values as we put in to the configuration element in the other database.

If you’re only wanting to configure the Tenant Portal you’d want to modify the Authentication.IdentityProvider.Primary configuration element. Be careful with the Primary/Secondary elements as they can get confusing.

If you’re configuring the Admin Portal you’ll need to update the Authentication.IdentityProvider.Secondary configuration element in the TenantAPI namespace to use the configuration you specified for the Admin Portal as well. As I said previously, I think this is because the Admin Portal calls into the Tenant API. The Admin Portal will use an admin-trusted token – therefore the TenantAPI needs to trust the admin’s STS.

Now that you’ve completed configuration you can do an IISRESET and try logging in. If you configured everything properly you should now be able to log in from your own IdP.

Troubleshooting

For those rock star Ops people who understand identity this guide was likely pretty easy to follow, understand, and implement. For everyone else though, this was probably a pain in the neck. Here are some troubleshooting tips.

Review the Event Logs
It’s surprising how many people forget that a lot of applications will write errors to the Windows Event Log. Windows Azure Pack has quite a number of logs that you can review for more information. If you’re trying to track down an issue in the portals look in the MgmtSvc-*Site where * is Tenant or Admin. Errors will get logged there. If you’re stuck mucking about the APIs look in the MgmtSvc-*API where * is Tenant, Admin, or TenantPublic.

Enable Development Mode
You can enable developer mode in sites by modifying a value in the web.config. Unprotect the web.config by calling:

And then locate the appSetting named Microsoft.Azure.Portal.Configuration.PortalConfiguration.DevelopmentMode and set the value to true. Be sure to undo and re-protect the configuration when you’re done. You should then get a neat error tracing window show up in the portals, and more diagnostic information will be logged to the event logs. Probably not wise to do this in a production environment.

Use the PowerShell CmdLets
There are a quite a number of PowerShell cmdlets available for you to learn about the configuration of Windows Azure Pack. If you open the Windows Azure Pack Administration PowerShell console you can see that there are two modules that get loaded that are full of cmdlets:

PS C:\Windows\system32> get-command -Module MgmtSvcConfig

CommandType     Name                                               ModuleName
-----------     ----                                               ----------
Cmdlet          Add-MgmtSvcAdminUser                               MgmtSvcConfig
Cmdlet          Add-MgmtSvcDatabaseUser                            MgmtSvcConfig
Cmdlet          Add-MgmtSvcResourceProviderConfiguration           MgmtSvcConfig
Cmdlet          Get-MgmtSvcAdminUser                               MgmtSvcConfig
Cmdlet          Get-MgmtSvcDatabaseSetting                         MgmtSvcConfig
Cmdlet          Get-MgmtSvcDefaultDatabaseName                     MgmtSvcConfig
Cmdlet          Get-MgmtSvcEndpoint                                MgmtSvcConfig
Cmdlet          Get-MgmtSvcFeature                                 MgmtSvcConfig
Cmdlet          Get-MgmtSvcFqdn                                    MgmtSvcConfig
Cmdlet          Get-MgmtSvcNamespace                               MgmtSvcConfig
Cmdlet          Get-MgmtSvcNotificationSubscriber                  MgmtSvcConfig
Cmdlet          Get-MgmtSvcResourceProviderConfiguration           MgmtSvcConfig
Cmdlet          Get-MgmtSvcSchema                                  MgmtSvcConfig
Cmdlet          Get-MgmtSvcSetting                                 MgmtSvcConfig
Cmdlet          Initialize-MgmtSvcFeature                          MgmtSvcConfig
Cmdlet          Initialize-MgmtSvcProduct                          MgmtSvcConfig
Cmdlet          Install-MgmtSvcDatabase                            MgmtSvcConfig
Cmdlet          New-MgmtSvcMachineKey                              MgmtSvcConfig
Cmdlet          New-MgmtSvcPassword                                MgmtSvcConfig
Cmdlet          New-MgmtSvcResourceProviderConfiguration           MgmtSvcConfig
Cmdlet          New-MgmtSvcSelfSignedCertificate                   MgmtSvcConfig
Cmdlet          Protect-MgmtSvcConfiguration                       MgmtSvcConfig
Cmdlet          Remove-MgmtSvcAdminUser                            MgmtSvcConfig
Cmdlet          Remove-MgmtSvcDatabaseUser                         MgmtSvcConfig
Cmdlet          Remove-MgmtSvcNotificationSubscriber               MgmtSvcConfig
Cmdlet          Remove-MgmtSvcResourceProviderConfiguration        MgmtSvcConfig
Cmdlet          Reset-MgmtSvcPassphrase                            MgmtSvcConfig
Cmdlet          Set-MgmtSvcCeip                                    MgmtSvcConfig
Cmdlet          Set-MgmtSvcDatabaseSetting                         MgmtSvcConfig
Cmdlet          Set-MgmtSvcDatabaseUser                            MgmtSvcConfig
Cmdlet          Set-MgmtSvcFqdn                                    MgmtSvcConfig
Cmdlet          Set-MgmtSvcIdentityProviderSettings                MgmtSvcConfig
Cmdlet          Set-MgmtSvcNotificationSubscriber                  MgmtSvcConfig
Cmdlet          Set-MgmtSvcPassphrase                              MgmtSvcConfig
Cmdlet          Set-MgmtSvcRelyingPartySettings                    MgmtSvcConfig
Cmdlet          Set-MgmtSvcSetting                                 MgmtSvcConfig
Cmdlet          Test-MgmtSvcDatabase                               MgmtSvcConfig
Cmdlet          Test-MgmtSvcPassphrase                             MgmtSvcConfig
Cmdlet          Test-MgmtSvcProtectedConfiguration                 MgmtSvcConfig
Cmdlet          Uninstall-MgmtSvcDatabase                          MgmtSvcConfig
Cmdlet          Unprotect-MgmtSvcConfiguration                     MgmtSvcConfig
Cmdlet          Update-MgmtSvcV1Data                               MgmtSvcConfig

As well as the MgmtSvcConfig module which is moreso for daily administration.

Read the Windows Azure Pack Claims Whitepaper
See here: Claims-Based Identity in Windows Azure Pack (docx).

Visit the Forums
When in doubt take a look at the forums and ask a question if you’re stuck.

Email Me
Lastly, you can contact me (steve@syfuhs.net) with any questions. I may not have answers but I might be able to find someone who can help.

Conclusion

In the first two parts of this series we looked at how authentication works, how it’s configured, and now in this installment we looked at how we can configure a third party IdP to log in to Windows Azure Pack. If you’re trying to configure Windows Azure Pack to use a custom IdP I imagine this part is the most complicated to figure out and hopefully it was documented well enough. I personally spent a fair amount of time fiddling with settings and most of the information I’ve gathered for this series has been the result of lots of trial and error. With any luck this series has proven useful to you and you have more luck with the configuration than I originally did.

Next time we’ll take a look at how we can consume the public APIs using a third party IdP for authentication.

In the future we might take a look at how we can authenticate requests to a service called from a Windows Azure Pack add-on, and how we can call into Windows Azure Pack APIs from an add-on.

The Importance of Elevating Privilege

by Steve Syfuhs / August 28, 2011 04:00 PM

The biggest detractor to Single Sign On is the same thing that makes it so appealing – you only need to prove your identity once. This scares the hell out of some people because if you can compromise a users session in one application it's possible to affect other applications. Congratulations: checking your Facebook profile just caused your online store to delete all it's orders. Let's break that attack down a little.

  • You just signed into Facebook and checked your [insert something to check here] from some friend. That contained a link to something malicious.
  • You click the link, and it opens a page that contains an iframe. The iframe points to a URL for your administration portal of the online store with a couple parameters in the query string telling the store to delete all the incoming orders.
  • At this point you don't have a session with the administration portal and in a pre-SSO world it would redirect you to a login page. This would stop most attacks because either a) the iframe is too small to show the page, or b) (hopefully) the user is smart enough to realize that a link from a friend on Facebook shouldn't redirect you to your online store's administration portal. In a post-SSO world, the portal would redirect you to the STS of choice and that STS already has you signed in (imagine what else could happen in this situation if you were using Facebook as your identity provider).
  • So you've signed into the STS already, and it doesn't prompt for credentials. It redirects you to the administration page you were originally redirected away from, but this time with a session. The page is pulled up, the query string parameters are parsed, and the orders are deleted.

There are certainly ways to stop this as part of this is a bit trivial. For instance you could pop up an Ok/Cancel dialog asking "are you sure you want to delete these?", but for the sake of discussion lets think of this at a high level.

The biggest problem with this scenario is that deleting orders doesn't require anything more than being signed in. By default you had the highest privileges available.

This problem is similar to the problem many users of Windows XP had. They were, by default, running with administrative privileges. This lead to a bunch of problems because any application running could do whatever it pleased on the system. Malware was rampant, and worse, users were just doing all around stupid things because they didn't know what they were doing but they had the permissions necessary to do it.

The solution to that problem is to give users non-administrative privileges by default, and when something required higher privileges you have to re-authenticate and temporarily run with the higher privileges. The key here is that you are running temporarily with higher privileges. However, security lost the argument and Microsoft caved while developing Windows Vista creating User Account Control (UAC). By default a user is an administrator, but they don't have administrative privileges. Their user token is a stripped down administrator token. You only have non-administrative privileges. In order to take full advantage of the administrator token, a user has to elevate and request the full token temporarily. This is a stop-gap solution though because it's theoretically possible to circumvent UAC because the administrative token exists. It also doesn't require you to re-authenticate – you just have to approve the elevation.

As more and more things are moving to the web it's important that we don't lose control over privileges. It's still very important that you don't have administrative privileges by default because, frankly, you probably don't need them all the time.

Some web applications are requiring elevation. For instance consider online banking sites. When I sign in I have a default set of privileges. I can view my accounts and transfer money between my accounts. Anything else requires that I re-authenticate myself by entering a private pin. So for instance I cannot transfer money to an account that doesn't belong to me without proving that it really is me making the transfer.

There are a couple ways you can design a web application that requires privilege elevation. Lets take a look at how to do it with Claims Based Authentication and WIF.

First off, lets look at the protocol. Out of the box WIF supports the WS-Federation protocol. The passive version of the protocol supports a query parameter of wauth. This parameter defines how authentication should happen. The values for it are mostly specific to each STS however there are a few well-defined values that the SAML protocol specifies. These values are passed to the STS to tell it to authenticate using a particular method. Here are some most often used:

Authentication Type/Credential Wauth Value
Password urn:oasis:names:tc:SAML:1.0:am:password
Kerberos urn:ietf:rfc:1510
TLS urn:ietf:rfc:2246
PKI/X509 urn:oasis:names:tc:SAML:1.0:am:X509-PKI
Default urn:oasis:names:tc:SAML:1.0:am:unspecified

When you pass one of these values to the STS during the signin request, the STS should then request that particular type of credential. the wauth parameter supports arbitrary values so you can use whatever you like. So therefore we can create a value that tells the STS that we want to re-authenticate because of an elevation request.

All you have to do is redirect to the STS with the wauth parameter:

https://yoursts/authenticate?wa=wsignin1.0&wtrealm=uri:myrp&wauth=urn:super:secure:elevation:method

Once the user has re-authenticated you need to tell the relying party some how. This is where the Authentication Method claim comes in handy:

http://schemas.microsoft.com/ws/2008/06/identity/claims/authenticationmethod

Just add the claim to the output identity:

protected override IClaimsIdentity GetOutputClaimsIdentity(IClaimsPrincipal principal, RequestSecurityToken request, Scope scope)
{
    IClaimsIdentity ident = principal.Identity as IClaimsIdentity;
    ident.Claims.Add(new Claim(ClaimTypes.AuthenticationMethod, "urn:super:secure:elevation:method"));
    // finish filling claims...
    return ident;
}

At that point the relying party can then check to see whether the method satisfies the request. You could write an extension method like:

public static bool IsElevated(this IClaimsPrincipal principal)
{
    return principal.Identity.AuthenticationType == "urn:super:secure:elevation:method";
}

And then have a bit of code to check:

var p = Thread.CurrentPrincipal as IClaimsPrincipal;
if (p != null && p.IsElevated())
{
    DoSomethingRequiringElevation();
}

This satisfies half the requirements for elevating privilege. We need to make it so the user is only elevated for a short period of time. We can do this in an event handler after the token is received by the RP.  In Global.asax we could do something like:

void Application_Start(object sender, EventArgs e)
{
    FederatedAuthentication.SessionAuthenticationModule.SessionSecurityTokenReceived 
        += new EventHandler<SessionSecurityTokenReceivedEventArgs> (SessionAuthenticationModule_SessionSecurityTokenReceived);
}
void SessionAuthenticationModule_SessionSecurityTokenReceived(object sender, SessionSecurityTokenReceivedEventArgs e)
{
    if (e.SessionToken.ClaimsPrincipal.IsElevated())
    {
        SessionSecurityToken token = new SessionSecurityToken(e.SessionToken.ClaimsPrincipal, e.SessionToken.Context, e.SessionToken.ValidFrom, e.SessionToken.ValidFrom.AddMinutes(15));
        e.SessionToken = token;
    }
}

This will check to see if the incoming token has been elevated, and if it has, set the lifetime of the token to 15 minutes.

There are other places where this could occur like within the STS itself, however this value may need to be independent of the STS.

As I said earlier, as more and more things are moving to the web it's important that we don't lose control of privileges. By requiring certain types of authentication in our relying parties, we can easily support elevation by requiring the STS to re-authenticate.

Generating Federation Metadata Dynamically

by Steve Syfuhs / November 03, 2010 04:00 PM

In a previous post we looked at what it takes to actually write a Security Token Service.  If we knew what the STS offered and required already, we could set up a relying party relatively easily with that setup.  However, we don’t always know what is going on.  That’s the purpose of federation metadata.  It gives us a basic breakdown of the STS so we can interact with it.

Now, if we are building a custom STS we don’t have anything that is creating this metadata.  We could do it manually by hardcoding stuff in an xml file and then signing it, but that gets ridiculously tedious after you have to make changes for the third or fourth time – which will happen.  A lot.  The better approach is to generate the metadata automatically.  So in this post we will do just that.

The first thing you need to do is create a endpoint.  There is a well known path of /FederationMetadata/2007-06/FederationMetadata.xml that is generally used, so let’s use that.  There are a lot of options to generate dynamic content and in Programming Windows Identity Foundation, Vitorrio uses a WCF Service:

[ServiceContract]
public interface IFederationMetadata
{    
    [ServiceBehavior]    
    [webGet(UriTemplate = "2007-06/FederationMetadata.xml")]    
    XElement FederationMetadata();
}

It’s a great approach, but for some reason I prefer the way that Dominick Baier creates the endpoint in StarterSTS.  He uses an IHttpHandler and a web.config entry to create a handler:

<location path="FederationMetadata/2007-06">    
    <system.webServer>
        <handlers>
            <add name="MetadataGenerator"
                path="FederationMetadata.xml"
                verb="GET"
                type="Syfuhs.TokenService.WSTrust.FederationMetadataHandler" 
                />        
            </handlers>    
    </system.webServer>    
    <system.web>        
        <authorization>
            <allow users="*" />
        </authorization>
    </system.web>
</location>

As such, I’m going to go that route.  Let’s take a look at the implementation for the handler:

using System.Web;

namespace Syfuhs.TokenService.WSTrust
{
    public class FederationMetadataHandler : IHttpHandler
    {
        public void ProcessRequest(HttpContext context)
        {
            context.Response.ClearHeaders();
            context.Response.Clear();
            context.Response.ContentType = "text/xml";
            MyAwesomeTokenServiceConfiguration.Current.SerializeMetadata(context.Response.OutputStream);

        }

        public bool IsReusable { get { return false; } }
    }
}

All the handler is doing is writing metadata out to a stream, which in this case is the response stream.  You can see that it is doing this through the MyAwesomeTokenServiceConfiguration class which we created in the previous article.  The SeriaizeMetadata method creates an instance of a MetadataSerializer and writes an entity to the stream:

public void SerializeMetadata(Stream stream)
{ 
    MetadataSerializer serializer = new MetadataSerializer(); 
    serializer.WriteMetadata(stream, GenerateEntities()); 
}

The entities are generated through a collection of tasks:

private EntityDescriptor GenerateEntities()
{
    if (entity != null)
        return entity;
            
    SecurityTokenServiceDescriptor sts = new SecurityTokenServiceDescriptor();
    FillOfferedClaimTypes(sts.ClaimTypesOffered);
    FillEndpoints(sts);
    FillSupportedProtocols(sts);
    FillSigningKey(sts);

    entity = new EntityDescriptor(new EntityId(string.Format("https://{0}", host))) 
    { 
        SigningCredentials = this.SigningCredentials 
    };

    entity.RoleDescriptors.Add(sts);
    return entity;
}

The entity is generated, and an object is created to describe the STS called a SecurityTokenServiceDescriptor.  At this point it’s just a matter of sticking in the data and defining the credentials used to sign the metadata:

private void FillSigningKey(SecurityTokenServiceDescriptor sts)
{
    KeyDescriptor signingKey = new KeyDescriptor(this.SigningCredentials.SigningKeyIdentifier)
    {
        Use = KeyType.Signing
    };

    sts.Keys.Add(signingKey);
}

private void FillSupportedProtocols(SecurityTokenServiceDescriptor sts)
{
    sts.ProtocolsSupported.Add(new System.Uri(WSFederationConstants.Namespace));
}

private void FillEndpoints(SecurityTokenServiceDescriptor sts)
{
    EndpointAddress activeEndpoint = new EndpointAddress(string.Format("https://{0}/STS/activeSTS.svc", host));

    sts.SecurityTokenServiceEndpoints.Add(activeEndpoint);
    sts.TargetScopes.Add(activeEndpoint);
}

private void FillOfferedClaimTypes(ICollection<DisplayClaim> claimTypes)
{
    claimTypes.Add(new DisplayClaim(ClaimTypes.Name, "Name", ""));
    claimTypes.Add(new DisplayClaim(ClaimTypes.Email, "Email", ""));
    claimTypes.Add(new DisplayClaim(ClaimTypes.Role, "Role", ""));
}

That in a nutshell is how to create a basic metadata document as well as sign it.  There is a lot more information you can put into this, and you can find more things to work with in the Microsoft.IdentityModel.Protocols.WSFederation.Metadata namespace.

The Basics of Building a Security Token Service

by Steve Syfuhs / October 29, 2010 04:00 PM

Last week at TechDays in Toronto I ran into a fellow I worked with while I was at Woodbine.  He works with a consulting firm Woodbine uses, and he caught my session on Windows Identity Foundation.  His thoughts were (essentially—paraphrased) that the principle of Claims Authentication was sound and a good idea, however implementing it requires a major investment.  Yes.  Absolutely.  You will essentially be adding a new tier to the application.  Hmm.  I’m not sure if I can get away with that analogy.  It will certainly feel like you are adding a new tier anyway.

What strikes me as the main investment is the Security Token Service.  When you break it down, there are a lot of moving parts in an STS.  In a previous post I asked what it would take to create something similar to ADFS 2.  I said it would be fairly straightforward, and broke down the parts as well as what would be required of them.  I listed:

  • Token Services
  • A Windows Authentication end-point
  • An Attribute store-property-to-claim mapper (maps any LDAP properties to any claim types)
  • An application management tool (MMC snap-in and PowerShell cmdlets)
  • Proxy Services (Allows requests to pass NAT’ed zones)

These aren’t all that hard to develop.  With the exception of the proxy services and token service itself, there’s a good chance we have created something similar to each one if user authentication is part of an application.  We have the authentication endpoint: a login form to do SQL Authentication, or the Windows Authentication Provider for ASP.NET.  We have the attribute store and something like a claims mapper: Active Directory, SQL databases, etc.  We even have an application management tool: anything you used to manage users in the first place.  This certainly doesn’t get us all the way there, but they are good starting points.

Going back to my first point, the STS is probably the biggest investment.  However, it’s kind of trivial to create an STS using WIF.  I say that with a big warning though: an STS is a security system.  Securing such a system is NOT trivial.  Writing your own STS probably isn’t the best way to approach this.  You would probably be better off to use an STS like ADFS.  With that being said it’s good to know what goes into building an STS, and if you really do have the proper resources to develop one, as well as do proper security testing (you probably wouldn’t be reading this article on how to do it in that case…), go for it.

For the sake of simplicity I’ll be going through the Fabrikam Shipping demo code since they did a great job of creating a simple STS.  The fun bits are in the Fabrikam.IPSts project under the Identity folder.  The files we want to look at are CustomSecurityTokenService.cs, CustomSecurityTokenServiceConfiguration.cs, and the default.aspx code file.  I’m not sure I like the term “configuration”, as the way this is built strikes me as factory-ish.

image

The process is pretty simple.  A request is made to default.aspx which passes the request to FederatedPassiveSecurityTokenServiceOperations.ProcessRequest() as well as a newly instantiated CustomSecurityTokenService object by calling CustomSecurityTokenServiceConfiguration.Current.CreateSecurityTokenService().

The configuration class contains configuration data for the STS (hence the name) like the signing certificate, but it also instantiates an instance of the STS using the configuration.  The code for is simple:

namespace Microsoft.Samples.DPE.Fabrikam.IPSts
{
    using Microsoft.IdentityModel.Configuration;
    using Microsoft.IdentityModel.SecurityTokenService;

    internal class CustomSecurityTokenServiceConfiguration
: SecurityTokenServiceConfiguration
    {
        private static CustomSecurityTokenServiceConfiguration current;

        private CustomSecurityTokenServiceConfiguration()
        {
            this.SecurityTokenService = typeof(CustomSecurityTokenService);
            this.SigningCredentials =
new X509SigningCredentials(this.ServiceCertificate);
            this.TokenIssuerName = "https://ipsts.fabrikam.com/";
        }

        public static CustomSecurityTokenServiceConfiguration Current
        {
            get
            {
                if (current == null)
                {
                    current = new CustomSecurityTokenServiceConfiguration();
                }

                return current;
            }
        }
    }
}

It has a base type of SecurityTokenServiceConfiguration and all it does is set the custom type for the new STS, the certificate used for signing, and the issuer name.  It then lets the base class handle the rest.  Then there is the STS itself.  It’s dead simple.  The custom class has a base type of SecurityTokenService and overrides a couple methods.  The important method it overrides is GetOutputClaimsIdentity():

protected override IClaimsIdentity GetOutputClaimsIdentity(
IClaimsPrincipal principal, RequestSecurityToken request, Scope scope)
{
    var inputIdentity = (IClaimsIdentity)principal.Identity;

    Claim name = inputIdentity.Claims.Single(claim =>
claim.ClaimType == ClaimTypes.Name);
    Claim email = new Claim(ClaimTypes.Email,
Membership.Provider.GetUser(name.Value, false).Email);
    string[] roles = Roles.Provider.GetRolesForUser(name.Value);

    var issuedIdentity = new ClaimsIdentity();
    issuedIdentity.Claims.Add(name);
    issuedIdentity.Claims.Add(email);

    foreach (var role in roles)
    {
        var roleClaim = new Claim(ClaimTypes.Role, role);
        issuedIdentity.Claims.Add(roleClaim);
    }

    return issuedIdentity;
}

It gets the authenticated user, grabs all the roles from the RolesProvider, and generates a bunch of claims then returns the identity.  Pretty simple.

At this point you’ve just moved the authentication and Roles stuff away from the application.  Nothing has really changed data-wise.  If you only cared about roles, name, and email you are done.  If you needed something more you could easily add in the logic to grab the values you needed. 

By no means is this production ready, but it is a good basis for how the STS creates claims.

Claims Transformation and Custom Attribute Stores in Active Directory Federation Services 2

by Steve Syfuhs / September 14, 2010 04:00 PM

Active Directory Federation Services 2 has an amazing amount of power when it comes to claims transformation.  To understand how it works lets take a look at a set of claims rules and the flow of data from ADFS to the Relying Party:

image

We can have multiple rules to transform claims, and each one takes precedence via an Order:

image

In the case above, Transform Rule 2 transformed the claims that Rule 1 requested from the attribute store, which in this case was Active Directory.  This becomes extremely useful because there are times when some of the data you need to pull out of Active Directory isn’t in a useable format.  There are a couple options to fix this:

  • Make the receiving application deal with it
  • Modify it before sending it off
  • Ignore it

Lets take a look at the second option (imagine an entire blog post on just ignoring it…).  ADFS allows us to transform claims before they are sent off in the token by way of the Claims Rule Language.  It follows the pattern: "If a set of conditions is true, issue one or more claims."  As such, it’s a big Boolean system.  Syntactically, it’s pretty straightforward.

To issue a claim by implicitly passing true:

=> issue(Type = "http://MyAwesomeUri/claims/AwesomeRole", Value = "Awesome Employee");

What that did was ignored the fact that there weren’t any conditions and will always pass a value.

To check a condition:

c:[Type == "http://schemas.microsoft.com/ws/2008/06/identity/claims/role", Value == "SomeRole"]
    => issue(Type = "http://MyAwesomeUri/claims/AwesomeRole", Value = "AwesomeRole");

Breaking down the query, we are checking that a claim created in a previous step has a specific type; in this case role and the claim’s value is SomeRole.  Based on that we are going to append a new claim to the outgoing list with a new type and a new value.

That’s pretty useful in it’s own right, but ADFS can actually go even further by allowing you to pull data out of custom data stores by way of Custom Attribute Stores.  There are four options to choose from when getting data:

  1. Active Directory (default)
  2. LDAP (Any directory that you can query via LDAP)
  3. SQL Server (awesome)
  4. Custom built store via custom .NET assembly

Let’s get some data from a SQL database.  First we need to create the attribute store.  Go to Trust Relationships/Attribute Stores in the ADFS MMC Console (or you could also use PowerShell):

image

Then add an attribute store:

image

All you need is a connection string to the database in question:

image

The next step is to create the query to pull data from the database.  It’s surprisingly straightforward.  This is a bit of a contrived example, but lets grab the certificate name and the certificate hash from a database table where the certificate name is equal to the value of the http://MyCertUri/UserCertName claim type:

c:[type == http://MyCertUri/UserCertName]
   => issue(store = "MyAttributeStore",
         types = ("http://test/CertName", "http://test/CertHash"),
         query = "SELECT CertificateName, CertificateHash FROM UserCertificates WHERE CertificateName='{0}'", param = c.value);

For each column you request in the SQL query, you need a claim type as well.  Also, unlike most SQL queries, to use parameters we need to use a format similar to String.Format instead of using @MyVariable syntaxes.

In a nutshell this is how you deal with claims transformation.  For a more in depth article on how to do this check out TechNet: http://technet.microsoft.com/en-us/library/dd807118(WS.10).aspx.

Converting Bootstrap Tokens to SAML Tokens

by Steve Syfuhs / September 09, 2010 04:00 PM

there comes a point where using an eavesdropping application to catch packets as they fly between Secure Token Services and Relying Parties becomes tiresome.  For me it came when I decided to give up on creating a man-in-the-middle between SSL sessions between ADFS and applications.  Mainly because ADFS doesn’t like that.  At all.

Needless to say I wanted to see the tokens.  Luckily, Windows Identity Foundation has the solution by way of the Bootstrap token.  To understand what it is, consider how this whole process works.  Once you’ve authenticated, the STS will POST a chunk of XML (the SAML Token) back to the RP.  WIF will interpret it as necessary and do it’s magic generating a new principal with the payload.  However, in some instances you need to keep this token intact.  This would be the case if you were creating a web service and needed to forward the token.  What WIF does is generate a bootstrap token from the SAML token, in the event you needed to forward it off to somewhere.

Before taking a look at it, let's add in some useful using statements:

using System;
using System.IdentityModel.Tokens;
using System.Text;
using System.Threading;
using System.Xml;
using Microsoft.IdentityModel.Claims;
using Microsoft.IdentityModel.Tokens;
using Microsoft.IdentityModel.Tokens.Saml11;

The bootstrap token is attached to IClaimsPrincipal identity:

SecurityToken bootstrapToken = ((IClaimsPrincipal)Thread.CurrentPrincipal).Identities[0].BootstrapToken;

However if you do this out of the box, BootstrapToken will be null.  By default, WIF will not save the token.  We need to explicitly enable this in the web.config file.  Add this line under <microsoft.IdentityModel><service><securityTokenHandlers>:

<securityTokenHandlerConfiguration saveBootstrapTokens="true" />

Once you’ve done that, WIF will load the token.

The properties are fairly straightforward, but you can’t just get a blob from it:

image

Luckily we have some code to convert from the bootstrap token to a chunk of XML:

SecurityToken bootstrapToken = ((IClaimsPrincipal)Thread.CurrentPrincipal).Identities[0].BootstrapToken;

StringBuilder sb = new StringBuilder();

using (var writer = XmlWriter.Create(sb))
{
     new Saml11SecurityTokenHandler(new SamlSecurityTokenRequirement()).WriteToken(writer, bootstrapToken);
}

string theXml = sb.ToString();

We get a proper XML document:

image

That’s all there is to it.

Installing ADFS 2 and Federating an Application

by Steve Syfuhs / August 13, 2010 04:00 PM

From Microsoft Marketing, ADFS 2.0 is:

Active Directory Federation Services 2.0 helps IT enable users to collaborate across organizational boundaries and easily access applications on-premises and in the cloud, while maintaining application security. Through a claims-based infrastructure, IT can enable a single sign-on experience for end-users to applications without requiring a separate account or password, whether applications are located in partner organizations or hosted in the cloud.

So, it’s a Token Service plus some.  In a previous post I had said:

In other words it is a method for centralizing user Identity information, very much like how the Windows Live and OpenID systems work.  The system is reasonably simple.  I have a Membership data store that contains user information.  I want (n) number of websites to use that membership store, EXCEPT I don’t want each application to have direct access to membership data such as passwords.  The way around it is through claims.

The membership store in this case being Active Directory.

I thought it would be a good idea to run through how to install ADFS and set up an application to use it.  Since we already discussed how to federate an application using FedUtil.exe, I will let you go through the steps in the previous post.  I will provide information on where to find the Metadata later on in this post.

But First: The Prerequisites

  1. Join the Server to the Domain. (I’ve started the installation of ADFS three times on non-domain joined systems.  Doh!)
  2. Install the latest .NET Framework.  I’m kinda partial to using SmallestDotNet.com created by Scott Hanselman.  It’s easy.
  3. Install IIS.  If you are running Server 2008 R2 you can follow these steps in another post, or just go through the wizards.  FYI: The post installs EVERY feature.  Just remember that when you move to production.  Surface Area and what not…
  4. Install PowerShell.
  5. Install the Windows Identity Foundation: http://www.microsoft.com/downloads/details.aspx?FamilyID=eb9c345f-e830-40b8-a5fe-ae7a864c4d76&displaylang=en
  6. Install SQL Server.  This is NOT required.  You only need to install it if you want to use a SQL Database to get custom Claims data.  You could also use a SQL Server on another server…
  7. Download ADFS 2.0 RTW: http://www.microsoft.com/downloads/details.aspx?familyid=118c3588-9070-426a-b655-6cec0a92c10b&displaylang=en

The Installation

image

Read the terms and accept them.  If you notice, you only have to read half of what you see because the rest is in French.  Maybe the lawyers are listening…these things are getting more readable.

image

Select Federation Server.  A Server Proxy allows you to use ADFS on a web server not joined to the domain.

image

We already installed all of these things.  When you click next it will check for latest hotfixes and ask if you want to open the configuration MMC snap-in.  Start it.

image

We want to start the configuration Wizard and then create a new Federation Service:

image

Next we want to create a Stand-alone federation server:

image

We need to select a certificate for ADFS to use.  By default it uses the SSL certificate of the default site in IIS.  So lets add one.  In the IIS Manager select the server and then select Server Certificates:

image

We have a couple options when it comes to adding a certificate.  For the sake of this post I’ll just create a self-signed certificate, but if you have a domain Certificate Authority you could go that route, or if this is a public facing service create a request and get a certificate from a 3rd party CA.

image

Once we’ve created the certificate we assign it to the web site.  Go to the website and select Bindings…

image

Add a site binding for https:

image

Now that we’ve done that we can go back to the Configuration Wizard:

image

Click next and it will install the service.  It will stop IIS so be aware of that.

image

You may receive this error if you are installing on Server 2008:

image

The fix for this is here: http://www.syfuhs.net/post/2010/07/22/ADFS-20-Windows-Service-Not-Starting-on-Server-2008.aspx

You will need to re-run the configuration wizard if you do this.  It may complain about the virtual applications already existing.  You two options:

  1. Delete the applications in IIS as well as the folder C:\inetpub\adfs;
  2. Ignore the warning.

Back to the installation, it will create two new Virtual Applications in IIS:

image

Once the wizard finishes you can go back to the MMC snap-in and fiddle around.  The first thing we need to do is create an entry for a Relying Party.  This will allow us to create a web application to work with it.

image

When creating an RP we have a couple options to provide configuration data.

image

Since we are going to create a web application from scratch we will enter in manual data.  If you already have the application built and have Federation Metadata available for it, by all means just use that.

We need a name:

image

Very original, eh?

Next we need to decide on what profile we will be using.  Since we are building an application from scratch we can take advantage of the 2.0 profile, but if we needed backwards compatibility for a legacy application we should select the 1.0/1.1 profile.

image

Next we specify the certificate to encrypt our claims sent to the application.  We only need the public key of the certificate.  When we run FedUtil.exe we can specify which certificate we want to use to decrypt the incoming tokens.  This will be the private key of the same certificate.  For the sake of this, we’ll skip it.

image

The next step gets a little confusing.  It asks which protocols we want to use if we are federating with a separate STS.  In this case since we aren’t doing anything that crazy we can ignore them and continue:

image

We next need to specify the RP’s identifying URI.

image

Allow anyone and everyone, or deny everyone and add specific users later?  Allow everyone…

image

When we finish we want to edit the claim rules:

image

This dialog will allow us to add mappings between claims and the data within Active Directory:

image

So lets add a rule.  We want to Send LDAP Attributes as Claims

image

First we specify what data in Active Directory we want to provide:

image

Then we specify which claim type to use:

image

And ADFS is configured!  Lets create our Relying Party.  You can follow these steps: Making an ASP.NET Website Claims Aware with the Windows Identity Foundation.  To get the Federation Metadata for ADFS navigate to the URL that the default website is mapped to + /FederationMetadata/2007-06/FederationMetadata.xml.  In my case it’s https://web1.nexus.internal.test/FederationMetadata/2007-06/FederationMetadata.xml.

Once you finish the utility it’s important that we tell ADFS that our new RP has Metadata available.  Double click on the RP to get to the properties.  Select Monitoring:

image

Add the URL for the Metadata and select Monitor relying party.  This will periodically call up the URL and download the metadata in the event that it changes.

At this point we can test.  Hit F5 and we will redirect to the ADFS page.  It will ask for domain credentials and redirect back to our page.  Since I tested it with a domain admin account I got this back:

image

It works!

For more information on ADFS 2.0 check out http://www.microsoft.com/windowsserver2008/en/us/ad-fs-2-overview.aspx or the WIF Blog at http://blogs.msdn.com/b/card/

Happy coding!

// About

Steve is a renaissance kid when it comes to technology. He spends his time in the security stack.