We have a Silverlight app which we wrote which calls a Silverlight-enabled data service. The Silverlight app cannot require a login, as it is required to present data to the unauthenticated public.
We have some schmoe who took the time to examine our Silverlight app, one way or another figure out what service it is calling, and then wrote his own client to slurp off the data so he can post it on his site and pretend like it is his. We need to prevent this.
How can i limit my data service somehow to ONLY accept requests from my silverlight app? I tried using the allow-from domain uri setting in the clientaccesspolicy.xml file to limit access to the service only from the domain in which the silverlight app sits (say mydomain.com). This did absolutely nothing though, and the service is still serving up requests to clients from outside the domain. (I tested this by putting my SL app on a different domain under our control).
What is the proper/best/most effective way to limit the data service so only our app can use it? Thanks!!!
I'm using SL 3 and .NET 3.5.
The clientaccesspolicy.xml tells the Silverlight application which Webservice it can consume. Not preventing people accessing the Webservice.
You can try using a authentication login even though its not required. This prevents 'schmoes' accessing your webservice.
Also use Dotfuscator to prevent 'schoes' to disassemble your Silverlight application and acquire the login.
Silverlight webservice security follows the same patterns you'd use for ASP.NET security, especially services exposed to AJAX. The best way to do make use of ASP.NET's authentication.
RIA Services is an even better way to handle this. It rides on top of the ASP.NET authorization, but validates on both the client and server-side automatically to combat service spoofing. It let you take care of both client and server-side authorization by adding attributes to your methods indicating that the method requires authorized access, and by which groups or users if you need to be specific.
In addition to wire-side security and obfuscation, remember that clients can attach a debugger to Silverlight applications running in their browser. See this example from MSDN Magazine's Security IQ Test, November 2008.
Related
I have a silverlight application backed by RIA services & EntityFramework. Users log in directly in the silverlight application. We have the [RequiresAuthentication] attribute on the DomainService and have implemented custom MembershipProvider/AuthenticationBase<UserBase> for custom authentication utilizing "forms authentication". All of this is working well to authenticate users.
The problem is that users with laptops using wifi will travel through the building and hand off between wifi access points. As soon as that handoff occurs, the users session is immediately terminated - with no notice to the user. I would like some way to make the session more resilient. Asp.Net's out-of-the-box forms authentication seems to do this well - as long as you are inside the session timeout and you haven't deleted your cookies, you are good to go regardless of any temporary connectivity issues. What can I do to get my Silverlight app to be at least as resilient as a standard asp.net app?
One thing that might be the issue, is that I haven't implemented many of the functions in the MembershipProvider - really only ApplicatinName and ValidateUser(). Could that be the source of my problem?
Is it possible to access Rally's SOAP services from Silverlight? I am able to access the service from a .NET 2.0 proxy in a desktop application, but not via a WCF client proxy in Silverlight. I get the following familiar exception,
System.ServiceModel.CommunicationException:
An error occurred while
trying to make a request to URI .... This could be due to attempting
to access a service in a cross-domain way without a proper
cross-domain policy in place, or a policy that is unsuitable for SOAP
services. You may need to contact the owner of the service to publish
a cross-domain policy file and to ensure it allows SOAP-related HTTP
headers to be sent. This error may also be caused by using internal
types in the web service proxy without using the
InternalsVisibleToAttribute attribute. Please see the inner exception
for more details.
I believe the problem is caused by trying to make a cross domain request from Silverlight, which requires a cross domain policy file installed on the server. If this is the case, why does the desktop application not require such a policy?
I'm not a Silverlight expert, but this looks like a cross-domain scripting/security sandbox that Silverlight imposes to make sure that Silverlight clients don't make requests to sites other than the server/host from which they were downloaded, unless the Silverlight client is specifically granted that right by the service provider/devloper. In the error message above:
"You may need to contact the owner of the service to publish a cross-domain policy file and to ensure it allows SOAP-related HTTP headers to be sent."
I think the "owner of the service" means the owner of the Silverlight host, rather than the "external" webservice (in this case, Rally).
Desktop and/or console apps wouldn't have this same sandbox restriction. You would probably encounter the same issue trying to access another vendor's webservices via a Silverlight client.
You might find this Silverlight-specific thread:
Cross Domain Policy
Helpful for the specifics of how to setup and configure a Silverlight cross-domain policy file on your server.
Silverlight was built with security in mind. That means cross site scripting from the Silverlight application is turned off by default and must be enabled on a case by case basis. A .NET desktop application, on the other hand, generally has far greater security permissions and can call whatever web services, COM objects, and native APIs it pleases.
The way you work around this issue in Silverlight is to create a service on your server. The Silverlight client code calls your server side service which in turn calls a third party web service. The server side service can bet .NET, java, whatever. Web servers can generally call whatever they like -- problem solved.
Resolved this myself by using the extended permission features available in Silverlight 5. Since the xap is deployed on an internal internet, this solution was acceptable.
I am going to be developing an application for work, and I am trying to decide whether to use Silverlight Business App or Asp.Net Web App. My manager is concerned about the performance and download time it would take if I created the entire application as a Silverlight app, with authentication. I have been playing around with some tutorials over the last week trying to get a perspective on my situation and have come up with a design question I need to ask those that are more experienced than me.
Is it possible to use a Asp.Net application and just embed a silverlight application in one of the pages that will be used inside a folder that is configured with the roles authorization? And if so, would it be possible to get user credentials from the client silverlight app without passing them through the initParams.
I understand that I can set the authentication to "useCookies", so I was thinking I would be able to get the cookie on the client and hopefully get a property verifying if the user is authenticated.
Also, would this be a risky practice? Thanks for any advice and direction.
There are a few approaches you could take. While I know you don't want to expose the credential in init params, you could generate a "ticket" (claims-based authentication) for the credential, and include the ticket (for example, a GUID) in the init params. When the Silverlight application launches, it would consume the ticket, possibly validating it via a secured web service call, and the ticket would no longer be valid so even if someone spoofed it or viewed the source, it couldn't be used.
Quite a bit depends on your architecture. For example, if you are using the roles-based authentication, and most of the business logic and/or decision making is based on web service calls, the web services can use HttpContext.Current.Identity to validate the user. Even if someone opens the Silverlight application, any service calls would fail unless they were appropriately authenticated. Otherwise, I would either go with passing a ticket so Silverlight trustst the user is valid (you can create a service that accepts the Guid and returns the role information) or have the user log in from Silverlight (you have a service facing in front of the authentication mechanism and then return a ticket and/or role information).
It gets even more interesting if you decide to use WCF RIA, check out these examples for baked-in authentication:
http://code.msdn.microsoft.com/RiaServices/Release/ProjectReleases.aspx?ReleaseId=2661
1.) It's absolutely possible to embed a Silverlight xap on an ASP.NET page.
2.) As far as credentials, using cookies could work, or you could pass in a token over initparams and validate that token via a web service to see if the user is valid
It's always a risk passing credentials around, especially when it's running on a clients computer. That said, Silverlight buys you a lot, so don't let the challenge of authentication hold you back.
I have googled a bit for how I should handle security in a web service application when the application is basically the data repository for a Silverlight application, but have gotten inconclusive results.
The Silverlight application is not supposed to have its own user authentication, since it will be reachable only through a web application that the user have already authenticated to get into.
As such, I was thinking I could simply add a parameter to the SL application that is a cookie-type value, with a certain lifetime, linked to the user in the database. The SL application would then have to pass this value alongside other parameters to the web services. Since the web service is hopefully going to be a generic web service endpoint, few methods, adding an extra parameter at this level will not be a problem.
But, am I supposed to roll this system on my own? It sounds to me as this isn't exactly new features that nobody has considered before, so what are my options?
First of all use SSL for the service. Otherwise users will be able to capture all the parameters passed to the service. It's still possible to see it in case of https but it will be a little bit more difficult.
Also, consider using Message Inspector for adding custom headers to the messages which you will validate on the server. This way you will not need to add extra parameters.
I have a Silverlight application that needs to retrieve some data from my database. This data is sensitive. Because of this, I only want my Silverlight application to be able to access the data. How do I ensure that only my applications can access the services that expose this data? Is there a way that I can validate a client attempting to retrieve the data?
Thank you!
These might be of interest:
Using ASP.NET Secure Services and Applications Services
Build Line-Of-Business Enterprise Apps With Silverlight, Part 2
MS Whitepaper: Security Guidance for Writing and Deploying Silverlight Applications
Well, everything your SL application does could be spoofed. So direct answer is NO, you cannot ensure that only your application will access to the data.
But there are number of options. For example you can implement authorization and then authenticate your user. In this way you can ensure that only users you trust access to the data.
Another option is to make spoofing harder. For example you can include sort of "secrete" token to all your requests. So other application will need to steal this token. This harder to achieve.
I think this question is more pertaining into implementing a web service or wcf service with authentication and authorization. If your service takes care of it, then you can be ensured about your data. Your silvelight app is just calling the service.
Whoever download the xap can decompress and reverse engineer your code, so your best bet is to build a web service as others suggested. Silverlight Ria ships with a full blown authentication membership that you can leverage.