I recently had the privilege to get access to a machine from a colleague of mine. It was a Windows server 2003 server and I had to test some ASP.Net application for one of my pet projects. I was focusing completely on the project at hand before I was completely taken off by a surprise, although not a pleasant one.
I found that my application was throwing the following exception, in fact forget my own application even a test Asp.Net 2.0 page having just a one word was failing. Also this happened for web resources hosted directly in IIS. If you run this app from within Cassini (ASP.Net Web server) you may not see this issue at all. This happened for both Website as well as WAP based applications hosted in IIS.
Server Error in '/' Application.
Unable to load DLL 'bcrypt.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.DllNotFoundException: Unable to load DLL 'bcrypt.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
[DllNotFoundException: Unable to load DLL 'bcrypt.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)]
Microsoft.Win32.Win32Native.BCryptGetFipsAlgorithmMode(Boolean& pfEnabled) +0
System.Web.Configuration.MachineKeySection.GetEncodedData(Byte buf, Byte modifier, Int32 start, Int32& length) +37
System.Web.UI.ObjectStateFormatter.Serialize(Object stateGraph) +166
System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Serialize(Object state) +4
System.Web.UI.Util.SerializeWithAssert(IStateFormatter formatter, Object stateGraph) +37
System.Web.UI.Page.SavePageStateToPersistenceMedium(Object state) +105
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1099
Version Information: Microsoft .NET Framework Version:2.0.50727.3053; ASP.NET Version:2.0.50727.3053
This was quite perplexing as I couldn't find much information on this across the net. One incident I found talked about un-installation of MS07-040 security update. I was running on .Net framework 2.0 Sp2, Windows Server 2003 SP2. No luck with it. I had no clues about this dll which was missing as in the exception and why the heck it was looking for it in the first place.
The interesting part here was that the call stack looked like having some encryption/decryption algorithm (RijndaelManaged) being used perhaps related to viewstate. I finally had to disable the attribute EnableViewStateMac="false" for the web page to make it work, but well that may not be an option all the time for everyone.
If you face such a scenario just don't go ahead with reinstallation of .Net framework 2.0, it may not help you but only drain your precious time.
From this KB article this is what RijndaelManaged is all about.
"ASP.NET 2.0 uses the RijndaelManaged implementation of the AES algorithm when it processes view state data. The ReindaelManaged implementation has not been certified by the National Institute of Standards and Technology (NIST) as compliant with the Federal Information Processing Standard (FIPS). Therefore, the AES algorithm is not part of the Windows Platform FIPS validated cryptographic algorithms."
To work around this either set EnableViewStateMac to false or else add the following entry as mentioned in the kb under <system.web> section for the web application.
<machineKey validationKey="AutoGenerate,IsolateApps" decryptionKey="AutoGenerate,IsolateApps" validation="3DES" decryption="3DES"/>
ASP.NET use the Triple Data Encryption Standard (3DES) algorithm to process view state data instead of the AES (Rijndael) algorithm. Remember this is comparatively weaker than Rijndael based encryption and hence your application will be comparatively insecure.
*Note that the error message in the above article is not exactly the same as what I saw here for this post but the resolution remains the same :-).
Till next time..
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Sorry but I think switching from Rijndael (strong) to 3DES (weak) encryption is not my ideal resolution for this case.
I am analyzing also this problem for Windows Forms application, but not have found a solution yet and switching to a weak algorithm is not an option in my case :(