I've been researching this intensely for the past few days.
We're developing an ASP.Net MVC site that needs to support 100,000+ users. We'd like to keep it fast, scalable, and simple. We have our own SQL database tables for user and user_role, etc. We are not using server controls.
Given that there are no server controls, and a custom membershipProvider would need to be created, where is there any benefit left to use ASP.Net Auth/Membership?
The other alternative would seem to be to create custom code to drop a UniqueID CustomerID in a cookie and authenticate with that. Or, if we're paranoid about sniffers, we could encrypt the cookie as well.
Is there any real benefit in this scenario (MVC and customer data is in our own tables) to using the ASP.Net auth/membership framework, or is the fully custom solution a viable route?
Update: I found one person (Matt Briggs) who seems to have come to some of the same conclusions I have: This comes from this link: http://webcache.googleusercontent.com/search?q=cache:Xm1-OrRCZXIJ:mattcode.net/posts/asp-net-membership-sucks+asp.net+membership+sucks&hl=en&gl=us&strip=1
ASP.net membership is a poorly engineered API that is insecure out of the box, is not well maintained, and gives developers a false sense of security. Authentication is a weekend project if you aren't building a framework, but still, most .net developers blindly follow the official APIs, assuming that a major corporation like MS can put out something decent.
You can customize to build your own provider. Behind the scenes the Membership provider uses the same FormsAuthentication implementation as you will write. Anyway, I have read that the main issues about the performance you will face will be related to the SQL SERVER stored procedures that retrieve the data. In one of the books about building a portal system by Omar Al Zabir he mentions some improvements to the stored procedure which can result in faster performance.
You can implement your own membership provider (as you mentioned) if you wish to have your own storage. One advantage is that you can administer memberships through IIS' .NET users configuration tool.
The biggest advantage is what the others stated already; why reinvent the wheel?
If you implement your own custom login UI using MVC you could reuse also when switching for a different membership provider.
One of the first rules of creating a secure authentication system is that you shouldn't try to build the framework yourself. There are many pitfalls that can be easily overlooked. So, I would say unless there is an overwhelming reason to do otherwise, you should use an existing framework like the MembershipProvider.
To list "the benefits" requires listing all security measures that were taken by the FormsAuthentication classes which is a long list. Off the top of my head, I can think a few:
I wrote my own after reading through all the stored procedures in the ASP.NET Membership provider. It's not hard and you have much more control at the end of the day.
If you like XML configuration, weakly-typed strings for roles, insecure by default, random web.config files littered through your directories instead of a clean marker interface on your page classes to say 'no account required', multiple database hits for a single login, user objects that aren't loaded from your current ObjectContext/DataContext and the ability to change providers on the fly (woo hoo, who uses that?!) go for the built-in one.
If not, build your own, but if you do, make sure you add salt and encrypt your passwords, and do a proper encrypted cookie please.
Just to clear up a potential misconception, using the customer ID, encrypted or not is extremely vulnerable to sniffers. What you want to do instead is create a log in ticket at the time of successful authentication and store that ID in the cookie. This won't protect sniffers from stealing sessions, but at least the session (eventually) expires whereas the customer ID does not.