Is it possible to use Brokered Kerberos Authentication for web services over the Internet? I'm looking at web services security for an environment which already has Active Directory. Due to the existing architecture the web services will be quite chatty and I have no control over this architecture. It may take up to 6 web service calls to perform one business process .
There is concern over authenticating multiple times and the overhead this will incur. From my initial reading of brokered kerberos authentication, once the user credentials are provided then a Kerberos security token will be returned and authentication is not required for each web service call.
I'm envisaging a system where the user credentials are passed to Active Directory via a web service call and the Kerberos token is returned. This token is then used for all subsequent web service calls.
Is this possible or am I heading off on a tangent? If I am heading off on a tangent is there a preferred approach for this? I've finished reading the Microsoft Web Service Security: Scenarios, Patterns and Implementation Guidance for WSE 3.0 and still a little unclear.
Consider leveraging the SAML protocol as a way to exchange assertions via WS-Security.
Related
My scenario is that I have to expose some API over WCF to third party clients. I wanna use the most secure option. Ideal solution would be making a windows account for each client in my server active directory and letting them access the service with Transport & Message security and Client credentials username. So I could ask the client to provide username and password and use windows group policy to role base authorization.
Since this is an internet facing WCF service, I'm not sure I could use windows accounts??? Should I be using database solution to manage usernames, pwd and roles?
Should be able to consume from .NET clients as well as Java clients. Third party clients could be anything that can consume soap.
What's the best security option to this scenario? VPN is not an option as this totally should go over internet. Your help is very much appreciated.
It sounds like what you need is some kind of a token based authentication setup. Microsoft seems to publish the best material in the game for this kind of thing. You can find their articles here and pick the scenario of security that most closely matches your needs:
Microsoft WCF Security
you can use ASP.net membership with form authentication for your service.
using windows authentication for internet facing service is not a good idea.
for more information:
How to: Enable the WCF Authentication Service
Windows Communication Foundation Authentication Service Overview
Securing WCF with Forms Authentication
I've got two MVC sites that use the same STS for authentication. I need to create a WCF service as part of one of the sites that allows the other site to retrieve data.
These sites could be on different machines accessible over the internet (although currently they're on the same machine) and the WCF service should only be able to be accessed from the client site. The authentication token used to log into the client site should be passed through to the WCF service.
I've been looking at the different WS-Security options available (Transport, Message etc) and it's not quite sinking in 100%, and I feel like I'd end up implementing something that seemed secure but wasn't actually secure due to a lack of understanding. Any help much appreciated.
Edit:
My first attempt was with transport layer security and setting the WCF service virtual directory with require SSL in IIS. However that left me with an error of:
"The remote certificate is invalid according to the validation procedure."
And I had no way of ensuring that a specific client was connecting to the service, only that a client had a certificate from a trusted CA. At least as far as I know. I'm probably missing something vital here.
The authentication token used to log into the client site should be
passed through to the WCF service.
In this case you should be requesting an "ActAs" token from the STS:
The WCF service should be configured as a Relying Party of the STS.
The MVC site should call back to the STS and request an ActAs token specific to the WCF service.
The MVC site uses the ActAs token to call the service.
The motivation for the complexity: Delegation, or traversing multilayer architectures
Since you mentioned WS standards:
Requesting Delegation (ActAs) Tokens using WSTrustChannel (as opposed to Configuration Madness)
Not knowing your STS its hard to say more, but Googling "ActAs token" will probably give you what you need.
I need to find a way to authenticate/authorize users in a WCF-service. I'm using an external authentication service which stores the credentials of the users.
Eg. "Bob uses our loginmethod, we send the credentials to the authentication service, the service lets us know if these credentials are correct."
If Bob sends another request, we need to know if Bob is already authenticated.
Now a session is being created on the client, but it needs to move to the server-side. We can not rely on clients for security.
Can this be solved by using security cookies or do any of you have a better suggestion?
EDIT! I can only use the authentication server and do not have access to it
The problem you are describing is a well-known one that had (at least) two standardized solutions.
Federation using WS-Trust
The first option is a SOAP based one that uses active federation based on WS-Trust. In this solution:
Your client provides credentials to the authentication service
If the credentials are valid, the authentication service returns a signed (and encrypted) token to the client. It is encrypted so that any information contained in the token remains confidential - even the client cannot read it. It is encrypted with a public key belonging to the your WCF service. It is signed with a private key belonging to the authentication service.
The client submits the signed/encrypted token to your WCF service. The service can decrypt it because it holds the private key for decryption. It can trust it because it is signed by the authentication service.
Based on the content of the decrypted token, the service can establish the client identity and make an authorization decision.
In this model, the usual terminology is:
Your authentication service the Security Token Service
Your WCF service is the Relying Party
your client is the Client
This sounds complex, but it is very well supported in .Net and WCF using Windows Identity Foundation. There are many samples available much of it (maybe all) can be done via WCF configuration rather than code.
This is well suited to scenarios where the clients are crypto-capable (like your .Net clients) and where good frameworks exist (like WIF). It is not so good for low spec clients such as browsers and some phones, or where you are not in control of the clients.
It is commonly used in enterprise scenarios, including enterprise-to-enterprise federation. It is used less often in internet scenarios.
the strengths of it are
It is standardised and therefore generally well supported by frameworks
It means that your WCF service never has to handle the client credentials (= more secure)
It makes it pretty easy to switch to different authentication services (because it is standardised). For example, on-premise AD and Windows Azure AD both support this, as do other independent identity services
An overview can be found here:
http://msdn.microsoft.com/en-us/magazine/ee335707.aspx
And Google will show you lots more walkthroughs and examples.
Federation using OAUth 2
In this solution:
The client displays some UI provided by the authentication service (generally a web page)
The user enters their credentials in that UI and the authentication service authenticates and eventually returns a token to the client. The nature of the token is not standardised, nor is whether it is encrypted. Generally it will be at least signed.
The client submits the token with each request to the WCF service
The WCF service authenticates the token as in the previous solution
In the OAuth terminology:
Your authentication service is the Authorization Server
Your WCF service is the Resource Owner
Your client is the Client
Again, this sounds complex, but it is reasonably well supported in .Net. Probably not as well as the WS-Trust approach though at the moment. It is supported by Windows Azure AD and on the client side, using the Windows Azure Authentication Library. May other services use this approach - e.g. Facebook.
This works well where
Your client is low spec or not crypto-capable (e.g. a browser or some phones)
You do not control the client (e.g. a third party application is accessing your service)
It is very commonly used in internet application where you as an owner of the WCF service don't necessarily know the users or the clients. It is a less complete standard in some ways (e.g. it does not define exactly how the authentication happens) and as a result, it is less easy to switch to alternative authorisation servers.
The strengths of it are:
It is simpler and therefore has wider platform support
It is growing in popularity and therefore the library support is getting better all the time
The user never enters their credentials into your UI, only into the auth server, so it is more likely to be trusted (in internet scenarios)
It has a built in way of controlling the scope of the permissions granted to the client, and revoking those permissions, so again it is more trusted in an internet scenario
The official .Net support for this is in the Windows Azure AD Authentication library
http://msdn.microsoft.com/en-us/library/windowsazure/jj573266.aspx
There are other, open source components too, such as DotNetOpenAuth
http://dotnetopenauth.net/
Which solution would be best for you depends mainly on the nature of your authentication service I would say. And on whether you are in an enterprise or internet scenario. If the auth. service could be easily adapted to be a WS-Trust Secure Token Service (STS), then that would be a good route. If adding some web UI to the auth. service is feasible, the OAuth might be better.
Or, if neither option is feasible, you could just borrow the patterns form one approach and use that without going for the full standard.
Good luck!
I have a Web API application and I've understood OAuth would be the standard security model for APIs where an Authentication Server would become responsible to generate Authorization Tokens so that the user can send to our server and consume the services.
I'm very new to this but I understand the roles involved:
Resource Owner
Client
Resource Server
Authorization Server
But what is OAuth exactly in practice, not in theory? Is it a .NET library? Is it a service provided by a separate Company? Is it something I can configure on my local development machine and see how it works?
How to get started with OAuth to secure a Web API application?
OAuth is a protocol; the current version is OAuth 2.0. More to your question, that link lists several implementations of the protocol in various technologies. For use with the .NET Web API you're probably interested in DotNetOpenAuth which provides implementations of both OAuth 1 and OAuth 2.
I'm using DotNetOpenAuth in an app I'm working on now to secure a .NET Web API. I've got an OAuth2Handler which extends DelegatingHandler which is inserted into the Web API pipeline before incoming requests reach any controllers. OAuth2Handler does the following:
Instantiates a DotNetOpenAuth ResourceServer
Calls ResourceServer.GetPrincipal() which reads and decrypts an access
token (issued elsewhere by the AuthorizationServer and returns an
OAuthPrincipal (In my case I'm reading additional data that the DotNetOpenAuth implementation allows you to pass and creating a ClaimsPrincipal.)
Assigning the IPrincipal containing the user information read from the access token to the User property of the thread and current HTTP context so it is available from the ApiController.User property in the service controllers: httpContext.User = Thread.CurrentPrincipal = principal;
Honestly, getting this all working (e.g. setting up the authorization server, resource server, certificates, etc.) isn't trivial. Unfortunately there didn't seem to be a good guide on the DotNetOpenAuth site. Here's a few other tasks you'll have ahead of you if you go this route:
Implement IAuthorizationServer - This is the interface provided by
DotNetOpenAuth that allows you to plug in to the library and use
their implementation to issue OAuth2 access tokens. You'll also need to implement INonceStore and ICryptoKeyStore which I did using an EntityFramework context for storage.
Configure Certificates - The AuthorizationServer and ResourceServer each use certificates to encrypt/decrypt the access token ensuring they are only accessible to each other. I built some custom configuration so I could manage this configuration in the web.config files of my authorization server app and my Web API services (resource server).
Manage Refresh Token - When first requesting an access token from the authorization server you'll get back (depending on your configuration) both an OAuth2 refresh token and an access token. The services use the access token which should be short-lived. The refresh token is used to get more access tokens. The refresh token should be kept secret (whatever that means in your scenario). For me it means the refresh token is never exposed to client-side javascript in my web app.
I hope that helps give you a high level idea of how to get started with OAuth and .NET Web API. Here's a blog post demonstrating some of these steps. This SO answer gives a few more high level details of the client side of the picture.
(The DotNetOpenAuth online docs appear to be down right now... sorry for no links to them; Apparently it has happened before).
I have Active Directory Federation Services 2.0 all setup and ready to work, but I have a scenario that falls outside pretty much everything I've read on enabling a relying party application. The 2 scenarios that are well documented involve A) Passive authentication for a web site or B) Using a thick client that's authenticated for calling web services.
My scenario is as follows: I have a web application that calls WCF services via Net.TCP for data access. I need to use ADFS 2.0 to secure each WCF call with a secure token.
I also can't use use the passive method of authenticating with ADFS from the web site (security restrictions outside my control).
So my question is, is it possible to manually request a secure token from ADFS via a web site, then use that same token to call my WFC service methods?
Have a look at http://travisspencer.com/blog/2009/03/caching-tokens-to-avoid-calls.html.
In this blog post it is described how to cache security tokens for wcf service calls.
I think it should also be possible to "inject" an already fetched token in the described "CacheSecurityTokenProvider".