What are the implementation details and rationale of ASP.NET MVC3's AntiForgeryToken?

Question

The AntiForgeryToken is used to prevent CSRF attacks, however the links on MSDN don't give me much insight to what exactly the AntiForgeryToken does, or how it works, or why things are done the way they are.

From what I gather, it creates a hash inside a web page and a cookie. One or both of them use the hashed IPrincipal.Name, and use symmetric encryption.

Can anyone shed light as to:

How the AntiForgeryToken works internally
What should it be used to protect
What should it NOT be used to protect
What is the reasoning behind the implementation choices for #1 above?

Link to S.O. http://stackoverflow.com/questions/4915430/what-are-the-implementation-details-and-rationale-of-asp-net-mvc3s-antiforgeryto — makerofthings7, Feb 06 '11 at 19:07

score 1 · Answer 1 · answered Mar 29 '11 at 16:19

1

All CSRF is prevented by the use of cryptographic nonce which cannot be obtained by the attacker due to Same-Origin Policy. This is not a problem that Symmetric Cryptography can solve.

Check out the CSRF Prevention Cheat Sheet.

answered Mar 29 '11 at 16:19

rook

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What are the implementation details and rationale of ASP.NET MVC3's AntiForgeryToken?

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