Installing an Internet Explorer ActiveX Control

This post is different from my usual posts, mainly because I have no idea what I am talking about! Well, at least I am admitting it this time!

I am tasked with creating an installation for an intranet type application. I need to create a shortcut to a URL and install a client side ActiveX control. For the sake of argument lets make it a fairly common one, such as the Crystal ActiveX viewer control. Sounds pretty simple, eh?

Let's go over a typical usage scenario. Hopefully, when designing applications and their deployment packaging you have some made-up profiles of typical users. Lets make up a few for our purposes. "Bob the system admin," "Mary the power user," and "Joe the restricted user" should be good enough. We can be a bit more specific and cover XP SP2 users, users with severely restricted ActiveX Browser settings, and non-IE browser users as well, but lets ignore these for now.

Essentially, Joe has a problem. We can give him the URL to the web application or even create a shortcut and/or favorite for him. The problem is, the first time he tries to run a Crystal Report, he gets a security warning, and the Crystal ActiveX control does not install. Of course, it is because he has no permissions to install software, even if everything else we ignored above is in good shape. Incidentally, if we can't figure out that Joe's problem is that he is a limited user, you can try the CDLLogViewer application to find out why.

Bob and Mary never have issues with the system. In fact, if Bob and/or Mary perform the same steps as Joe everything works, and Joe logs in later on, even Joe can view and print reports. The problem is that Bob and Mary would never run reports on the system. Heck, Bob doesn't even launch the application. Bob may even deploy the install package using SMS or Group Policy.

In the corporate network world, pretty much everyone is a Joe. There are a few Privileged Mary's, and even less Bob's. To make all this work, Bob needs to install applications for the likes of Joe. This behavior is not only acceptable, but practically expected.

So how would Steve, our installation guru, make all this work? He would not only need it to work, but be practically bulletproof.

Option 1: The easiest approach. 99% of the time, this is synonymous with the wrong approach. We can extract the Crystal Reports ActiveX viewer cab file, read the .inf file to figure out what it is doing, add the files to a MSI project selecting the proper registration options, create the shortcut file, and be done with the project in under 20 minutes.

Why it doesn't work: Since Joe is not the only user of the machine (remember Mary and Bob?), any updates to the control will cause the MSI-based installation to screw up at some point. If the control is updated by Mary, and Bob uninstalls the application, the component/reference count then causes havoc with Mary by possibly removing the file on uninstall. Effectively, we have precluded the normal installation/updating/removal of the ActiveX Viewer by repackaging it in an MSI. More information on the hazards of this approach can be found on MSDN in the "Registry Details" page. Bad stuff.

Option 2: Install the shortcuts as in Option 1. Call the appropriate API's to install the CAB file from the web server. In this case, (after a bit of digging through MSDN I see this process is called "Internet Component Download" or ICD for short) we need to call CoGetClassObjectFromURL.

Why it doesn't work: Referring to the ICD link above, we assume the web server is up and running at installation time - #1 in the "Download and install process". We also assume that WinVerifyTrust returns a value that is compatible with the setting for ActiveX controls for the Zone in which the server we are pulling the cab file from resides - #2 in the "Download and install process". Last, but not least, we are assuming that good old Bob didn't muck with the CODEBASE setting of the Internet Search Path.

Option 3: Completely decimate the user's machine by querying the IE Security Settings, saving them, adding the server to a trusted zone, modifying the zone parameters to set the ActiveX settings appropriately, call CoGetClassObjectFromURL, after it succeeds, set everything back to the way it was.

This seems like a heck of a lot of work, but it appears to be the only way to bulletproof an installation of an ActiveX component. Plus, we ignored several issues. If the default browser was (or will be) Firefox or even Lynx, a shortcut to this URL will always fail to display the reports. To solve this problem, an EXE wrapper would need to be written to host the IE control to assure that IE is actually the browser engine used to access the page. Joel, the API war is far from over - it just made things more complicated!

Of course, I'll get to play around with these API's and see if installing the cab file from a file:// UNC path changes anything. I'll report back what I find. If anyone else has already "solved" this problem using an approach I haven't considered, please let me know. In all likelihood, I'll end up calling CoGetClassObjectFromURL, and if it fails, try to provide some meaningful feedback to the user as to why the installation can not succeed and let Bob worry about the corner cases. After all, he ultimately created them.

UPDATE: Please see Part II of this post!