Writing a custom NTLM challenge/response in ASP.Ne

Question

I know that you can enable NTLM authentication in an ASP.Net app using:

<authentication mode="Windows" />

However - I need to handle Forms, HTTP and other custom authentications in the same app, so ASP.Net's limited built-in support is no use.

The NTLM handshake should be fairly simple:

Request  - [unauthenticated - no user info passed]

Response - 401 Unauthorized
           WWW-Authenticate: NTLM


Request  - Authorization: NTLM <base64-encoded type-1-message>

Response - 401 Unauthorized
           WWW-Authenticate: NTLM <base64-encoded type-2-message>


Request  - Authorization: NTLM <base64-encoded type-3-message>

           Server can now check username/password against LDAP from type-3 message
Response - 200 Ok [now authenticated & authorised]

So to roll my own I need to parse type-1 and type-3 messages and generate a type-2 message.

The structure for those messages is well documented but fairly complex - it seems very messy to write my own message generators and parsers. I think the methods to read and write these messages should already be in .Net, but I haven't been able to find them.

How can I build and parse these NTLM messages using .Net?

Answer 1

Cassini supports NTLM authentication, so you could use the source to more easily create a class which parses the NTLM authorization messages.

http://cassinidev.codeplex.com/