ASP.Net MVC – Viewstate validation failed on page with no viewstate (or server side controls)

asp.netasp.net-mvcviewstate

An interesting take on an error that's really fustrating. I have a MVC page with no runat=server controls, a single form, and yet I have still recieved a "Validation of viewstate MAC failed" exception on the page, when reading through my error logs.

Here is the exception thrown:

System.Web.HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. ---> System.Web.UI.ViewStateException: Invalid viewstate.
Client IP: 10.XXX.XXX.XXX Port: 33791 
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5 (.NET CLR 3.5.30729) 
ViewState: /wEPDwUKMTc2MzIxNTAwOWRkLTq4ngVrnkwCLjQCKKiLdjGVFbs=

Here is the complete stack:

System.Web.HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. ---> System.Web.UI.ViewStateException: Invalid viewstate. 
    Client IP: 10.XXX.XXX.XXX
    Port: 33791
    User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5 (.NET CLR 3.5.30729)
    ViewState: /wEPDwUKMTc2MzIxNTAwOWRkLTq4ngVrnkwCLjQCKKiLdjGVFbs=
    Referer: http://www.shelfari.com/search/combine?Keywords=turn%20of%20the%20screw
    Path: /search/Combine ---> System.Web.HttpException: Unable to validate data.
   at System.Web.Configuration.MachineKeySection.GetDecodedData(Byte[] buf, Byte[] modifier, Int32 start, Int32 length, Int32& dataLength)
   at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString)
   --- End of inner exception stack trace ---
   --- End of inner exception stack trace ---
   at System.Web.UI.ViewStateException.ThrowError(Exception inner, String persistedState, String errorPageMessage, Boolean macValidationError)
   at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString)
   at System.Web.UI.Util.DeserializeWithAssert(IStateFormatter formatter, String serializedState)
   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()
   at System.Web.UI.Page.ProcessRequest(HttpContext context)
   at ASP.views_search_bookcombined_aspx.ProcessRequest(HttpContext context)
   at System.Web.Mvc.ViewPage.RenderView(ViewContext viewContext)
   at System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context)
   at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClass11.<InvokeActionResultWithFilters>b__e()
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult)
   at System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName)
   at System.Web.Mvc.Controller.ExecuteCore()
   at System.Web.Mvc.MvcHandler.ProcessRequest(HttpContextBase httpContext)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

It's not clear why there would be viewstate on the page at all – I've never been able to reproduce the error, but it occurs occasionally in logs. The users who get the error tend to be individuals trusted & unlikely to be manipulating the viewstate manually.

The production environment is a webfarm, with machineKey configuration specified, using the validationKey and validation algorithm across all machines.

Any thoughts?

Best Answer

I've seen this too. I believe the cause is search engine accesses -- something must be missing in the way that the search engine accesses the page. At least the issue went away when I added a robots.txt file and told the search engines not to spider my login page (with the form and antiforgery token).

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