Validation of viewstate MAC failed and anti XSRF issue - asp.net

Question

I know this was posted here so many times and had a valuable suggestions and suggested fixes. But none of them helped.
We have an e commerce site which is online ordering system. Our web site is hosted on IIS 7.0 with .net framework 4.0.(this is the only website running on IIS ). In our testing environment everything worked fine and we deployed it.
Now we are getting MAC ERROR when user is trying to access the site or if he is in the site and browsing to other pages, user is facing this error. Here is the stack trace.
Exception: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.
Stack Trace: System.Web.HttpException
Stack Trace:
at System.Web.UI.ViewStateException.ThrowError(Exception inner, String persistedState, String errorPageMessage, Boolean macValidationError) at System.Web.UI.ViewStateException.ThrowMacValidationError(Exception inner, String persistedState) at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString, Purpose purpose) at System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter2.Deserialize(String serializedState, Purpose purpose) at System.Web.UI.Util.DeserializeWithAssert(IStateFormatter2 formatter, String serializedState, Purpose purpose) at System.Web.UI.HiddenFieldPageStatePersister.Load() at System.Web.UI.Page.LoadPageStateFromPersistenceMedium() at System.Web.UI.Page.LoadAllState() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest() at System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context) at System.Web.UI.Page.ProcessRequest(HttpContext context) at ASP.pages_usagereports_index_aspx.ProcessRequest(HttpContext context) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
We started getting this issue when we implemented a code to fix CSRF issue in the base page.
If we take out the code and tested with a user, we are not getting any error.
So far we have tried these solutions
1) Applied machine key to the website even though we are not web farm environment.
2) We don’t want to disable the enableviewstate to false or the viewstateencryption mode to never as it is preferred not to do that. We even tried this but didn’t help.
3) We tried assigning different combinations for the base.viewstateuserkey like combination of userhostaddress and user Agent but it didn't help.
4) We used Microsoft .net web protection library from this link
http://software-security.sans.org/developer-how-to/developer-guide-csrf
After this we started getting another error
Inner Exception Type: System.InvalidOperationException
Inner Exception: Validation of Anti-XSRF token failed.
Inner Stack Trace:
at System.Web.UI.Page.HandleError(Exception e) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest() at System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context) at System.Web.UI.Page.ProcessRequest(HttpContext context) at ASP.signin_aspx.ProcessRequest(HttpContext context) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
Now we are getting two errors. MAC error and Anti XSRF error.
Searched on this error and I saw number of posts but i tried them. None of them helped.
Any suggestions on this are much appreciated.
Thanks in advance

Answer 1

The MAC for the ViewState is derived using the ANtiXsrfTokenKey generated in your master page. If the token is not present when the user accesses your site (cookies disabled or the value in the cookie changed or deleted) then the page will generate a new token. What then happens, if there is a ViewState in the page being posted back, is that the MAC will be checked with the new Token and won't match the old token, that is the first error you can see.
The Xsrf check in your master page is slightly confusing but uses the Xsrf token stored in a cookie and matches it to the value stored in the page. Usually these will match but if another site attempts to make an illegal request to your site, their site won't send the Xsrf cookie and the check will fail. The reason that this is confusing is that if you have a ViewState, this will fail before the Xsrf check.
Another issue with the Xsrf check is that it uses the logged in user's name as part of the check. If a user is logged in and then the auth cookie is deleted or expires, this part of the check will fail and you will see an Xsrf failure which is misleading, the real error is that "the authentication has expired causing the Xsrf check to fail".
I have re-worked the functions in Site.Master.cs several times to make these errors more clear.
Hope that helps.