Should we develop a custom membership provider in this case?

Summary

Long story short, we've been tasked with gutting the authentication and authorization parts of a fairly old and bloated asp.net application that previously h开发者_Python百科ad all of these components written from scratch. Since our application isn't a typical one, and none of us have experience in asp.net's built in membership provider stuff, we're not sure if we should roll our own authentication and authorization again or if we should try to work within the asp.net membership provider mindset and develop our own membership provider.

Our Application

We have a fairly old asp.net application that gets installed at customer locations to service clients on a LAN. Admins create users (users do not sign up) and depending on the install, we may have the software integrated with LDAP.

Currently, the LDAP integration bulk-imports the users to our database and when they login, it authenticates against LDAP so we dont have to manage their passwords. Nothing amazing there.

Admins can assign users to 1 group and they can change the authorization of that group to manage access to various parts of the software.

Groups are maintained by Admins (web based UI) and as said earlier, granted / denied permissions to certain functionality within the application.

All this was completely written from the ground up without using any of the built in .net authorization or authentication. We literally have IsLoggedIn() methods that check for login and redirect to our login page if they aren't.

Our Rewrite

We've been tasked to integrate more tightly with LDAP, they want us to tie groups in our application to groups (or whatever types of containers that LDAP uses) in LDAP so that when a customer opt's to use our LDAP integration, they dont have to manage their users in LDAP AND in our application.

The new way, they will simply create users in LDAP, add them to Groups in LDAP and our application will see that they belong to the appropriate LDAP group and authenticate and authorize them.

In addition, we've been granted the go ahead to completely rip out the User authentication and authorization code and completely re-do it.

Our Problem

The problem is that none of us have any experience with asp.net membership provider functionality. The little bit of exposure I have to it makes me worry that it was not intended to be used for an application such as ours. Though, developing our own ASP.NET Membership Provider and Role Manager sounds like it would be a great experience and most likely the appropriate thing to do.

Basically, I'm looking for advice, should we be using the ASP.NET Membership provider & Role Management API or should we continue to roll our own? I know this decision will be influenced by our requirements so I'm going over them below

Our Requirements

Just a quick n dirty list

• Maintain the ability to have a db of users and authenticate them and give admins (only, not users) the ability to CRUD users
• Allow the site to integrate with LDAP, when this is chosen, they don't want any users stored in the DB, only the relationship between Groups as they exist in our app / db and the Groups/Containers as they exist in LDAP.
• .net 3.5 is being used (mix of asp.net webforms and asp.net mvc)
• Has to work in ASP.NET and ASP.NET MVC (shouldn't be a problem I'm guessing)
• This can't be user centric, administrators need to be the only ones that CRUD (or import via ldap) users and groups
• We have to be able to Auth via LDAP when its configured to do so

I always try to monitor my questions closely so feel free to ask for more info. Also, as a general summary of what I'm looking for in an answer is just. "You should/shouldn't use xyz, here's why".

Links regarding asp.net membership provider and role management stuff are very welcome, most of the stuff I'm finding is 5+ years old.

Security in the context of your problem involves two separate operations: authentication and authorization and those are divided in .NET into MembershipProviders and RoleProviders. I would strongly recommend using both (meaning custom or built-in) to do your authentication and authorization. Doing so, provides a path to upgrade should you later find better tools to do the job and makes it easier for other developers to understand the security.

Now, for authentication, I would, as others have stated, use either the SqlMembershipProvider or the ActiveDirectoryMembershipProvider. My experience has been that in 99% of the cases the ActiveDirectoryMembershipProvider provides enough functionalty for what is need when working against a full AD store (i.e. not ADAM aka ActiveDirectory Application Mode). I have had problems with the ActiveDirectoryMembershipProvider in multi-domain situations but in general finding a way of using it rather than rolling your own is much better. Similarly, the SqlMembershipProvider for authentication, works well and scales well.

Authorization however is an entirely different kettle of fish. This is really where your pain will be felt. First, there is no "ActiveDirectoryRoleProvider". That means if you want to integrate with AD groups, you have three choices:

1. Use AzMan
2. Do it yourself via a custom RoleProvider
3. Find someone that has done it for you.
4. Use ADFS or Microsoft's new Federated Services

Choice 1: AzMan AzMan (Authorization Manager) (See also Windows Authorization Manager) is a tool Microsoft wrote to manage application authorization. AzMan has some nice features to it:

1. It can link your roles to AD groups (or Windows groups)
2. It can be stored as a file so you can keep it with the application.
3. Nicely breaks up authorization into tasks, operations and roles.
4. Comes with a separate administrative tool
5. The 2008 version will interact with SQL authentication stores.

The catch is that AzMan can be a bear to develop against and understanding the tool is not for someone that isn't experienced. I found that documentation was scant but that was a few years ago. In addition, the AuthorizationStoreRoleProvider does not support Tasks even though AzMan itself does. Tasks are the most granular things that can be done and are group into Operations which themselves can be grouped into Roles into which users or AD groups can be dropped. Documentation has gotten a little better. I do know that when I last worked with AzMan, it's lack of inherit interaction with a database authentication store made it a bit of a pain to work with.

Choice 2: Write your own RoleProvider

This can be a painful experience with LDAP. You would only need a custom RoleProvider in the case where you wanted to query against AD groups and did not want to use AzMan if you planned on using the SqlRoleProvider in non-AD environments.

Another alternative which I have used, is to manage roles in the database and allow the MembershipProvider to be whatever it wants. This still entails writing a custom provider (but a significantly simpler one) and it makes it easy to move the application into an AD environment with little mess. If you store roles in the database and if you want to allow administrators to associate multiple levels of groups to your roles, then you'll have to write that into your custom RoleProvider.

If you plan on using the SqlRoleProvider you also can run into a few issues. If you use the SqlRoleProvider with the SqlMemberProvider in a single application environment then it will work quite well and is very easy to setup. However, if you have multiple applications that you want to authenticate against a single store, then the SqlRoleProvider will not work properly in all cases out of the box without modification.

Choice 3: Find someone that has done it for you.

Specifically, I mean find someone that has developed an ActiveDirectoryRoleProvider. You can easily Google for various choices but I have not used them and would want to pour over any code that anything to do with security in my application.

Choice 4: Active Directory Federated Services

Microsoft has really been pushing this solution which does promise single sign-on if you can get it working. The catch to this solution is getting it setup especially between you and a partner.

I have been very please with the ease of the Membership Provider and Role Provider classes. They just work. The best part in my opinion, is that for my local development, I'm using a SQL Provider to logon to the local database which has the same user names as some of the people I want to test as (Admin, advanced user, basic user) with generic passwords. Then, when I publish my application, it uses the ActiveDirectory Membership Provider and integrates seamlessly. I don't have to change one piece of code for access restrictions. (Except for the differences between my web.config files)

With your situation, it does seem best to write your own custom provider, simply because you want to discover the user in your database but compare their password to LDAP. Also, these seamlessly integrate with both Webforms and MVC.

I would recommend Scott Mitchell's Multipart Series on the providers. Very extensive and thorough.

Also I would add that just because some of the articles are old, doesn't meant they don't still apply. The membership provider framework has been out for a number of years now, so it makes sense that some of the articles are gathering Ethernet dust.

I'm dealing with some of this same stuff so I'm going to start this answer with just a little bit and hopefully build onto it over time.

A quick answer is that, given your requirements, I'm going to suggest that you might want to research the TWO built-in providers that Microsoft makes available to you: SQL Server-based and Active Directory-based. Out of the box, with just the flip of some configuration in your .config file, you can flip the switch from using SQL Server to using Active Directory. Unless I'm misunderstanding your needs, it may sound like this is exactly what you need in your two scenarios. If you do it this way, 100% of your application can look and function identically, even with the same codebase. Migrating data from an existing application of one deployment to the other gets more interesting (and I have no experience with that, unfortunately), but clean deployments of one versus the other should be pretty simple.

Now obviously, if you don't like the behavior of the built-in providers, you can create your own.

Where I am at in my work is that we have been using the SQL-based provider and we need to move to Active Directory and the built-in provider may or may not be sufficient for our needs (I am still evaluating that, and very active in doing so at the moment). I have also worked with some proof-of-concept code so that, in the case that we need to, I have confidence that we can create our own provider reasonably well.

So I know that this is not exactly an answer to your question(s) but I hope that this gives you something to think about for now and helps you in some way. Like I said, I'm happy to add more to this as I grow in knowledge here myself.

FYI material

[How Do I:] Create a Custom Membership Provider? - Video Tutorial from ASP.Net official site. A very nice introduction into the topic.

Simple LDAP Membership Provider - Forum post of a very simple LDAP membership provider.

GPL .Net LDAP Membership Provider - It's GPL, so it may not work for commercial applications. Also hasn't been worked on in a while. But I guess it's still worth mentioning.

Notes

1. You may have to fight the clients temptation to use LDAP as a database. Be strong! LDAP can be use for Authentication and even Authorization. But you may eventually need to store a lot more information. The only reasonable way to do this is to map your LDAP uid to a database user table and run off that. Your membership provider can make this transparent to the rest of your project. But the client must understand that although LDAP affords them single sign-on, it's shouldn't be used as a database replacement.

2. Personally, I would stick to the Membership API but try to write a performant backend. Maybe something of a little caching and automatically maps LDAP users to the database user table on the uid as a key. The nice thing about LDAP is it has quite a bit of support in .Net. You won't have to manage sockets, etc. unless you really want to. Due to this, my LDAP/directory access code is usually under a dozen lines per method easily. And that's often good enough for production.

Just to throw another idea into the ring - have you considered Federated authentication and Claims-based authorization? It looks like it may be a good fit for your scenario. Basically this enables you to decouple the authentication from your application into a federated service provider (think OpenID) that manages authentication and issues a token to your application. There are service providers available that will integrate with LDAP, AD, and other directory standards. ADFS (Active Directory Federation Services, formerly Geneva Server) is one example that links with AD.

When configured appropriately, properties that are associated with an identity, such as group membership, can be passed to your application as a "claim" that is associated with the identity - your application can do what it likes with the claim. The point is that your application can find out which groups a user belongs to, and other properties e.g. email address, by examining the claims that are passed within the token.

The advantage of federated authentication is twofold. First, you can integrate with any directory you like, not just LDAP, as long as there is a provider (or of course you can write your own provider). Second, it keeps authentication out of your application code so you can vary the implementation in the future to support different scenarios.

Check out http://msdn.microsoft.com/en-us/magazine/ee335707.aspx for an introduction to the Windows Identity Foundation (formerly code-named 'Geneva Framework'). Or check out the team blog.