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.
Related
Identity Server 4 exposes OpenID Connect Discovery via .well-known/openid-configuration url. Now I'm not fully clear why this is here or who should have access to it. The way I understand this, all this page does is gives out information about the endpoints.
The applications that will have access to my IS4 server will have the endpoints pre-configured as they are all internal so I see no reason to have this page exposed, I see it more secure not to give out this information out.
As such, My question is should I restrict access to this page and if so how? And if not, why?
The main benefit for keeping that endpoint is automatic client configuration. From the MVC sample on the AspNet.Security.OpenIdConnect.Samples GitHub page:
// Note: setting the Authority allows the OIDC client middleware to automatically
// retrieve the identity provider's configuration and spare you from setting
// the different endpoints URIs or the token validation parameters explicitly.
Authority = "http://localhost:54540/"
The server library has the ability to change any of the endpoint paths during startup, like the endpoint for obtaining a token. By using automatic configuration, your applications can automatically pick up on that change without you needing to update all your client applications manually.
This functionality is only offered as a convenience, should you want to use it.
If this application is only exposed to your internal network (or just within your own computer or Docker network), there is absolutely no harm in leaving this be.
If this application is exposed to the public network, then you need to start asking yourself if you want an attacker to know the information that the configuration endpoint provides.
All an attacker would know is the application is an Auth server, the paths to your various endpoints, what types of OAuth2 flows you support, and maybe a few other small details. If you have publicly facing documentation, this would just be a machine-readable version of that.
Rather than focusing on preventing access to the configuration endpoint, make sure that your Auth server endpoints are authenticated. You should be checking that the Client Id and Client Secret are present and correct before giving out tokens.
From oauth.com (this is about the introspection endpoint but really the principle applies to all endpoints):
If the introspection endpoint is left open and un-throttled, it presents a means for an attacker to poll the endpoint fishing for a valid token. To prevent this, the server must either require authentication of the clients using the endpoint, or only make the endpoint available to internal servers through other means such as a firewall.
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 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".
I want to write a web service using Visual Studio. The service needs to support some type of authentication, and should be able to receive commands via simple HTTP GET requests. The input would only be a method call with some parameters, and the responses will be simple status/error codes. My instinct would be to go with an ASP.NET Web Service, but this isn't an option in C# 4.0 and it makes me wonder if I should be using something that's more up-to-date. I've looked into WCF, but it seems like this requires a running application on the client-side - is there a way to query a WCF host by just accessing a URL?
The authentication is also an important piece. Developing my own little authentication system seems like a bad idea - I've read that it's too easy to mess up. What would be the standard way of authenticating with a web service like this?
I'd love to look up all of the specifics on this and learn it myself, but I really don't even know where to begin. Some direction would be greatly appreciated!
For a simple HTTP service that takes commands via GET (you should actually consider using POST...) I would use straight ASP MVC, not a true
'web service'. WCF wants to guide you down the path of SOAP and your clients will curse you forever. RESTful WCF is also an alternative, but it still seem overkill imho.
As for authentication, you have two viable authentication schemes:
Windows Integrated security, which will work only if client is inside intranet or connected with a VPN or DirectAccess solution
HTTP Digest, which is poorly supported by the ASP authentication modes (only support authenticating against a Active Directory forest user base).
With Windows authentication you don't do anything on the server side code, simply mark the the web.config <authentication mode="Windows" />. 'Windows' authentication is understood by most user agents. Is trivial to program clients of your service to use Windows authentication too, simple set the request's Credentials to the current user DefaultCredentials.
With Digest authentication the server will challenge the user agent to authenticate, but the ASP validation unfortunately, as I said, only works for validating a trusted NT domain. The client though does not need to be in the intranet (there is no NTLM SSPI exchange between client and server). Programming a client is faily easy, in .Net simply set the requet Credentials to a properly initialized CredentialsCache:
CredentialCache myCache = new CredentialCache();
myCache.Add(new Uri("http://www.contoso.com/"),"Digest", new NetworkCredential(UserName,SecurelyStoredPassword,Domain));
...
request.PreAuthenticate = true;
request.Credentials = myCache;
It is important to reuse the cache between requests, otherwise the client will do two round-trips with each call.
In theory you can also have a third authentication path: full duplex SSL. But the 'trivial' problem of client certificate deployment makes this alternative a dead end for anybody short of a fully pre-installed enterprise PKI.
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.