installation - Per Machine App Registration

Question

I'm building an installer with WiX to install a program, per machine (not per user), and it gives them the option to register the program. Registration involves entering user name and organization (or accepting some defaults from Windows settings), and entering a valid registration key. When the registration key is validated, I write registry settings in the HKEY_LOCAL_MACHINE area with this information. Under Windows, when one runs the MSI, it prompts automatically for an admin password to be able to set registry values in HKEY_LOCAL_MACHINE. So far life is good...

I am including an option in the MSI to give the user the option to defer registration until a later point in time. However, if the user is a normal user and they are running the application, if I have a dialog in the app which prompts for name/org/product-key, Windows doesn't the app to write the information to HKEY_LOCAL_MACHINE. So a user cannot use the application itself, running as a normal user, to perform a registration per-machine as the MSI does after prompting for admin credentials.

My thought then was, for post-installation registration, to either (a) find a way from within the application to elevate privileges, with a prompt for admin credentials, allowing it to write HEKY_LOCAL_MACHINE (is this possible?), (b) include an option in the installer that, when run and the app is already installed and not registered, walks through the registration as it would during a normal install. It would then prompt for the admin credentials and life is good again. Alternatively, (c) create a separate MSI that just does registration, install this with the program, and call this MSI from the program when the user selects the "Register..." command in the program.

I've not seen either of these approaches done by any applications before, so I'm not sure either is a good approach. Other than that, however, I'm not sure how, post-installation, I can conveniently allow the user to do a per-machine app registration. Ideally, I'd like to be able to do it from a command within the app, but re-running the installation MSI would be minimally acceptable.

How is this normally done? Or are per-machine installations even normally accompanied by per-machine registrations?

Answer 1

Very good question - I have dealt with this issue many times myself. No ideal solutions, but several options (as you have already discovered).

Before answering, I want to point out that I have a strong aversion against doing too much registration and configuration in the setup itself. It is error prone, and much better done in the application itself for a plethora of reasons: Installer with Online Registration for Windows Application (recommended quick read - tidbits from real life experience).

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Writing to HKCU

As you already know, one option is to keep the license key and registration in HKCU only. This is often acceptable unless you want to share a license key between many users on the box. The license key, if added to HKCU, will also generally roam with the user to other computers - which can be helpful or desirable.

Personally, this is the option I prefer: not registering anything in the setup, but writing to HKCU or the user-profile from the application (as explained in the link above as well). As stated, the only drawback is that you can't write a shared license key to HKLM so it applies to all users and not just a single user. This appears to be the core of the problem you are describing.

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Writing to HKLM

1. Setup writes HKLM: Write the HKLM license key (and registration) during the setup to HKLM as Phil has described above using the default Windows Installer properties (just listing this as an option - which you already know about). This should work OK in my opinion - but your issue seemed to be to allow the "deferred registration".
2. Custom HKLM ACL permissioning: In order to write to HKLM from your non-elevated application, one way to do it is to use your setup to apply custom ACL permissions to the location in HKLM where you want to write the shared registry key from your application. Your application can then freely update this specific location in HKLM at any time without elevated rights. You simply add ACL write access for "Users".
   • WiX supports this, but I don't have a sample for you available, please check the WiX documentation for permissioning.
   • Using custom permissioning is generally frowned upon (and I agree it is not ideal design), but it allows any user to add a license key to HKLM without any elevation after the install (and also allows any users to delete it - which can be a problem).
   • See section 14 here for a quick description of why custom permissioning is not generally recommended: How do I avoid common design flaws in my WiX / MSI deployment solution?
   • In summary, I don't generally suggest setting custom permissions, but it will definitely work. I have done it myself when client requirements are such that this is the only thing they will accept. It will violate logo requirements for Windows applications, but it should be less serious than the security issues that result from option 3 below.
3. Run app as admin: If you don't want to apply ACL permissions, I believe you can prompt the user for admin rights for your application as described here (I believe this is what Phil referred to in his comment if I understand correctly): How do I force my .NET application to run as administrator? (the legendary Hans Passant - one more answer).
   • This is most definitely not recommended (but we want to show people what is possible too). Your whole application will run with admin rights all the time, which is not a good idea at all.
   • Doing this will violate a key part of logo requirements for Windows applications and you will also open your application up to attack from malware.
   • Definitely try to make your users understand the consequences of this "easy fix". I would make sure to put all responsibility on the client if they go for this option - they must understand what they are doing.
   • Note that you should be able to use this manifest approach to launch a separate EXE with elevated rights to do only the registration. See next bullet point.
4. Elevate app on demand: I am not familiar with the technical details of elevating your application on demand whilst it is running - as you invoke a dialog or feature that needs HKLM access. Perhaps Phil knows a way to achieve this? I found some links though:
   • Elevating during runtime (from Code Project)
   • How to elevate privileges only when required? (good read)
   • Skimming the linked content above, it seems like you can launch a separate EXE with elevated rights to do your registration - a known option for you I assume.
   • Would love to hear back if this is something you decide to try. Could be useful for all of us.
5. Internet validation: Just throwing an option out there: what I often want to do is to put the whole registration license key validation online from within the application (never, ever try this from the setup, just so that is mentioned - a setup that tries to access the Internet might be the biggest deployment anti-pattern of all - at least for now).
   • I write the license key from the setup, and the validation of it takes place on application launch against a server on the Internet. Then there is no validation code in your application or your setup to crack.
   • You need an Internet "handshake" and you can repeat this process per user - allowing you to tightly control who is using your license key.
   • Nothing is ever easy, and proxy server issues could cause problems. Corporate deployment would also mean that such "online activation" is frowned upon. They want applications fully installed after deployment.
6. Separate registration MSI: I would prefer not to create a separate MSI just for the registration process as you mention in your question. This just seems like unnecessary complexity that can break easily. For one thing you get a dual source problem that must be permanently maintained. I would guess that this could become a classic support issue.
7. Re-run original MSI: I am honestly not sure if re-running your original setup to do the registration will launch it elevated or not. I think it will be elevated (should be, can't see any reason why it shouldn't - the MSI database stores a flag to determine if elevation is required "Word Count"), and then you should be able to add your registration details provided you access the registration dialog from the setups "modify" or "repair" modes.