Having spent many happy years (decades!) running various versions of DF and VDF I decided that WebApp was required for a special task. Nothing would make webapp function on my machine so I asked a colleague, Stephen Dunn to look into it. This is his report, a horror story. Sandy Young.

On a fully patched Windows 7 x64 machine VDF web applications were not working. They were generating permission errors about contacting the isapi.dll on IIS as well as various other HTTP 500 errors on the ASP. It seemed to be an issue with pass through authentication. The PT authentication worked on the top of the tree default site but no matter what permissions were set no other sites accepted PT authentication for the ASP to access the needed DLL. If it wasn’t for the fact we had a laptop here that it was working on we would have likely dismissed VDF and blamed it for the issues.

On comparing the laptop and the PC, both running Win7 x64, the difference was patching level. In particular IE9 was not on the laptop. Knowing the other issues IE9 was giving the VDF studio I focussed on this. All other steps to install the VDF studio and setup the web apps were completed in exactly the same manner. IIS was enabled as suggested. Basic WWW Service rules with the ASP box selected under Application Development Features and all of the IIS 6 compatibility features enabled under Web Management Tools. 32bit apps were then enabled on the DefaultApplicationPool. The DefaultAppPool was left to run under v2 of the .net framework.

In an attempt to diagnose exactly what the issue was I created a virtual machine running Win7 x64. The first snapshot branch of the VM, from the OOTB install, I enabled IIS and installed the VDF studio. I ensured web apps and PT authentication to sites beneath the default site in ISS were working. I stepped through all of the patching levels from the OOTB install to a fully patched system and it worked every step of the way. I installed IE9 last and everything was still working on the VM.

I therefore returned to my initial OOTB snapshot and this time I patched the machine first, right up to the level where only IE9 wasn’t installed. I then enabled IIS and installed the VDF studio. Web apps and PT authentication were still working. Lastly I installed IE9. As soon as IE9 was installed all of the authentication and permission errors appeared. Returning to the snapshot on the VM taken prior to IE9 install I reversed the previous process by installing IE9 first then the enabling IIS and installing the studio. Web apps and PT authentication didn’t work. Uninstalling IE9 DID NOT bring the system back to the pre install state on either branch and once web apps were broken that was it.

I have not tested this on an x86 Win 7 install but I would be very surprised if this was processor architecture specific. I would also be almost certain this bug will affect any Vista machines running IE9 due to them having the same kernel as Win7. However it cannot be discounted this is an IE9 and IIS 7.5 bug and the IIS 7.0, which would be on a Vista machine, may not be affected. Further testing would be required to prove / disprove this.

As you can see it is quite a nasty bug as not many people will enable IIS PRIOR to patching the machine up to date!