Is it possible to decode EventValidation and ViewState in ASP.NET?

Question

How to decode the ASP.NET EventValidation and ViewState?

Answer 1

Create a simple windows app and use Convert.FromBase64(str) to decode ViewState data if it is not encrypted.

Note: GridView causes encryption.

Answer 2

I needed to decode ViewStates recently and found this tool useful: View State decoder

Answer 3

I answered a similar question recently, Getting values from viewstate using JQuery?.

Basically, by default ViewState is just Base64-encoded, so you can decode it as long as the administrator hasn't configured the site to encrypt it. Quoting from my previous answer:

If you are writing the control for your own consumption and you only need to read from ViewState, you could do so, but I wouldn't recommend it unless you find a well-debugged library to parse it for you. The format is a bit hairy (see ViewState: All You Wanted to Know for more details).

That link provides an extremely thorough and clear introduction to ViewState.

As for Event Validation, I'm unsure whether it's Base64-encoded or if it just looks like Base64 (I can't find a conclusive, authoritative reference). This Rexiology article might help though.

Answer 4

You can use this link if use python.

Best way is use this link.

A small Python 3.5+ library for decoding ASP.NET viewstate.

First install that: pip install viewstate

>>> from viewstate import ViewState
>>> base64_encoded_viewstate = '/wEPBQVhYmNkZQ9nAgE='
>>> vs = ViewState(base64_encoded_viewstate)
>>> vs.decode()
('abcde', (True, 1))

Answer 5

I'm not sure about EventValidation, but you can decode ViewState by using Fritz Onion's ViewState Decoder.