How in a SOA environment to separate the logic from the presentation at a high level by implementing the presentation in the form of web forms in ASP.Net?

Question

Single sign-on technology

Now at an abstract level I am thinking over a solution for a corporate portal of an enterprise.
The idea is to separate the logic from the presentation at a high level by implementing the presentation as web forms in ASP.Net and the logic as loosely coupled web services (perhaps some approximation to SOA architecture).
Now I can not solve the problem of authentication. On the one hand, you need to hide from the user everything that he does not need at the portal level, on the other hand, steer the rights at the service level. That complicates administration.
The second problem is the explicit transition to role models. Very weakly imagine the option with the intersection of roles.
The third problem will come out when you need to enable the service with its own user management mechanism. Some mechanism for passing Credentials is needed (maybe a sane SSO system). We tried it on the Biztalk bus, but in some cases it is not practical to use it.
Can you recommend any sane Enterprize SSO systems.
Another important issue is service management. Now I'm spinning around UDDI, but this may not be what I want. Full control of services is required (version control, health, etc.)