James Finnigan : Setup

The Shell Extensions Approved list is not a complete list of shell extensions on the system

jamesfinnigan — Sat, 08 Sep 2007 07:42:02 GMT

I've noticed that a number of different programs just look at the Approved list of shell extensions [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Shell Extensions\Approved] and figure that all shell extensions will be in that list. It's not true, because lots of folks don't really care about that policy. I don't know how often it's used - it doesn't really make your system more secure as far as I can tell. (It may reduce the TCO related to folks installing poorly written shell extensions.)

It also doesn't apply to all shell extensions. There are many of them (probably some of them with HKCU extensibility) that haven't been moved to the policy system yet. (So you should always register your shell extensions there, even if it doesn't seem to be necessary.)

(That said, it certainly does give you quite a few of them for very little work. On my system, it finds about 325/400 - about 80%. Because of that, if you're thinking about turning on this policy consider the fact that you'll be disabling 1 in 5 shell extensions; will that generate more or less support calls?)

Supplemental Registrations (aka. Context Menu Handers (etc) - where are they loaded from...)

jamesfinnigan — Thu, 06 Sep 2007 19:00:00 GMT

I've been thinking about the registration problem where you want to add a context menu (much of this applies to static verbs as well) to a file type (we'll say .ogg). You don't want the default verb, you just want to add some verbs. Because you don't want the default, you shouldn't put your progid in the HKCR\.ogg default value, so you put an entry under HKCR\.ogg\shellex\ContextMenuHandler. And this works great.. until someone comes along and puts a progid in HKCR\.ogg's default value. Look at the fallthrough logic below - #2 (where we registered), and #3 are only used if there is no progid!

Fallthrough logic when loading context menu handlers (static verbs and then context menu handlers are collected from the following places):

(DO NOT USE THIS LOGIC IN YOUR CODE - it is a simplification of the real logic and it will change. Instead, use IQueryAssociations or AssocQuery* for all these kinds of file association related things.)

HKCR\<ProgID>
HKCR\<.ext> (only if #1 does not exist)
HKCR\Unknown (only if #1 does not exist)
HKCR\SystemFileAssociations\<.ext>
HKCR\SystemFileAssociations\<PerceivedType>
HKCR\Folder (only used if the selected item has the SFGAO_FOLDER attribute, such as a folder, zip, cab, etc.)
HKCR\*
HKCR\AllFilesystemObjects

But there is a way! You can register supplemental verbs associated with the SystemFileAssociations key. Note that those keys (#4 and #5) are folded in regardless of the association having a progid registered. In our example, that would be HKCR\SystemFileAssociations\.ogg\shellex\ContextMenuHandler

The important thing here is that you should never put the registration under HKCR\<.ext>(!) because you should either be putting it under your progid (#1), or in SystemFileAssociations (#4). Why do we disable #2 and #3 in those cases? If folks are interested, I'll talk more about that later - or feel free to guess. :)

(A quick comment about #5 - I think it is often misused. Applications don't know how to handle very many perceived types (one exception is text). How are you going to handle the "video" perceived type? I guarantee that we'll come out with more codecs/container formats, etc. Unless you can guarantee that you can handle everything that will map into the perceived type, don't register for it - instead register for the individual associations that you really can handle.)

This technique is used for a lot of other things besides context menu handlers. It's also used for Property Handlers for Windows Search, Windows Imaging Component codecs, etc, etc, etc.

Cheers,
James

[Update: finished the sentence beginning "In our example, that would be..."]

Installing shell extensions - please complain here

jamesfinnigan — Sat, 11 Aug 2007 04:02:00 GMT

So... I've been looking more closely at Wix and I think I'm going to build some custom actions to do a really good job installing shell extensions. Which ones do you find most problematic? I realize this is a bit of a change of pace for the blog, so I'll probably hit a few other forums, but please feel free to add comments/complaints about which extensions are problematic.

Maybe you've already done the work to install these properly, but in some cases that can be quite complicated and I could see a lot of folks just accepting some minor bugs and moving on.

I'll start:

Protocol Handlers (http://msdn2.microsoft.com/en-us/library/bb266527.aspx) and Schema Extensions (http://msdn2.microsoft.com/en-us/library/ms647576.aspx). Both of these require custom actions to be installed correctly - and there's no standard for it so everyone is probably doing it themselves which is going to lead to some really inconsistent behavior. None of that is going to help system stability at all.

Another one I came across recently was installing a shell folder that should appear on the desktop. I added it to the desktop namespace but until the user refreshes the desktop it isn't going to appear. You need to send a SHChangeNotify to get it to show up without user intervention. Anyway, there's no standard action for that. So unless you can accept a shortcut to the shell folder (which sends a notification), you'll want a CA there as well. And there again, you want to send as minimal a notification as possible to avoid having the system reload everything when all that you needed is a new icon to show up.

File Associations:
This one is going to be a bit of a laundry list of issues, but I'll start off the first couple issues.

If previous handlers didn't register under openwith then your registration may blow away any record that they wanted to handle that file association.
If you register under a meta-type like TXTFile and then someone else claims .txt then you don't get invoked at all.
Man that thing is complicated. Way, way complicated. (I'm still learning the subtleties - feel free to correct me if I miss a beat.)

So there's a start - let me know as you come across other issues.

Cheers,
James

The best way to make UAC shut up for a while

jamesfinnigan — Sat, 09 Jun 2007 06:25:00 GMT

Let's say you want to install a few things and want UAC to stop bugging you while you install them. Should you turn off UAC and install the apps? Since that disables UAC's virtualization, it can destabilize things that depend on data written to those virtual locations. Here's an alternative that keeps all the virtualization intact while getting UAC to lay off for a while.

Fire up gpedit.msc and adjust this policy (pictured below):

Change it to be Elevate without prompting:

Of course, remember to turn it back when you're done! :)

Cheers,

James

[Update: how to do this without using gpedit.msc]

Run this command (from an elevated command prompt) to make UAC elevate without prompting:

reg ADD HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System /v ConsentPromptBehaviorAdmin /t REG_DWORD /d 0 /f

When you're done, run this command (from an elevated command prompt) to set it back to the default:

reg ADD HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System /v ConsentPromptBehaviorAdmin /t REG_DWORD /d 2 /f

Making an MSI that doesn't need a UAC/LUA prompt

jamesfinnigan — Thu, 03 May 2007 08:03:00 GMT

The goal

I think that most things don't need to require a UAC prompt to install - just install it for that user. Why not make the MSI so it doesn't prompt and your users get a smoother experience? (Also, I feel much better installing a program that doesn't require elevation to install - at a minimum I know it's not disabling my anti-malware software.) Ideally, with that same package you could optionally install per-machine (which requires elevation). Here's some information on how to make it happen...

Background

I was recently asked to make an MSI for an extremely minimal replacement of the Run As menu item that was removed in Vista (by calling runas.exe). Although I doubt we would ever ship something like that I decided to make an installation that didn't elevate, or that could elevate and install per-machine. It was an interesting experience, although I didn't entirely get the behavior I was going for - there are some limitations that make it impossible to do with a MSI in Windows Vista, but still possible in a single download. (More on that later).

The technical details

All MSIs elevate on Windows Vista by default. However there is a flag that you can set that will tell MSI that you don't need to elevate. The 3rd bit of the word count summary property can be set by using the msiinfo tool (comes with the platform SDK). Since I also used an embedded cab, that means my word count summary property should be set to 10 (8 | 2 == 10).

msiinfo RunAsNewUser.msi -w 10

You need to have the feature include both the per-user and per-machine information if you're trying to put both in one package like I did (not a best practice - more on that later).

    <Feature Id='RunAsNewUser' Title='Run as New User' Level='1'>
      <ComponentRef Id='pm.runasnewuser.cmd' />
      <ComponentRef Id='pm.runasnewuser.reg.exe' />
      <ComponentRef Id='pm.runasnewuser.reg.msc' />
      <ComponentRef Id='pu.runasnewuser.cmd' />
      <ComponentRef Id='pu.runasnewuser.reg.exe' />
      <ComponentRef Id='pu.runasnewuser.reg.msc' />
    </Feature>

Your standard MSI that installs to the system directories doesn't face the (fairly simple) issues involved. Here's the per-machine version of my components (you need two versions of the components in order to put them in different directories(*). [I build all my MSIs using Wix - it gives me fine-grained control for making really solid MSIs and it tends to match the way I want to think about MSIs.]

      <!-- We need a per-machine version as well, with seperate components -->
      <Directory Id='ProgramFilesFolder' Name='AdTools'>
        <Directory Id='pm.Microsoft' Name='Microsoft'>
          <Directory Id='pm.Runas' Name='RunAs'>
            <Component Id='pm.runasnewuser.cmd' Guid='9D448C8B-AF67-423B-9622-D9720770B61E'>
              <File Id='pm.runasnewuser.cmd' Name='runasnewuser.cmd' DiskId='1' Source='runasnewuser.cmd' KeyPath='yes' />
              <Condition>ALLUSERS</Condition>
            </Component>
            <Component Id='pm.runasnewuser.reg.exe' Guid='98A7DE3E-EF1D-434F-80CB-2F878CD0E9F5'>
              <RegistryKey Id='pm.runasnewuser.reg.exe' Key='SystemFileAssociations\.exe\shell\Run as new user...\command' Root='HKCR' Action='createAndRemoveOnUninstall'>
                <RegistryValue Id='pm.runasnewuserCommand.exe' Type='expandable' Value='"[#pm.runasnewuser.cmd]" "%1" %*' KeyPath='yes'/>
              </RegistryKey>
              <Condition>ALLUSERS</Condition>
            </Component>
            <Component Id='pm.runasnewuser.reg.msc' Guid='20D758CC-2774-4532-BD6D-E7C378761C90'>
              <RegistryKey Id='pm.runasnewuser.reg.msc' Key='SystemFileAssociations\.msc\shell\Run as new user...\command' Root='HKCR' Action='createAndRemoveOnUninstall'>
                <RegistryValue Id='pm.runasnewuserCommand.msc' Type='expandable' Value='"[#pm.runasnewuser.cmd]" "%1" %*' KeyPath='yes'/>
              </RegistryKey>
              <Condition>ALLUSERS</Condition>
            </Component>
          </Directory>
        </Directory>
      </Directory>

Notice that I made these components conditional on ALLUSERS. We'll make the per-user version conditional on NOT (ALLUSERS). This is pretty basic stuff, and is more or less simply specifying what goes where without much specialized stuff. You can do a per-user setup that looks quite similar by putting it somewhere that isn't off the user's profile. I decided to put mine in the user's profile which means a little extra baggage.

So we're basically done right? Well, not really, no. We've disabled the elevation, but now you need to make your installation not require elevation. Things like installing to Program Files require admin rights, so we'll need to install to somewhere else. I'm not really sure where that should be - probably %UserProfile%\ProgramFiles or something like that. In this example, I installed to LocalAppData.

      <Directory Id='LocalAppDataFolder' Name='AdTools'>
        <Directory Id='pu.Microsoft' Name='Microsoft'>
          <Directory Id='pu.Runas' Name='RunAs'>
            <Component Id='pu.runasnewuser.cmd' Guid='06A57A74-7639-4A96-A1FF-6C434ED50CEF'>
              <File Id='pu.runasnewuser.cmd' Name='runasnewuser.cmd' DiskId='1' Source='runasnewuser.cmd' />
              <RegistryValue Id='pu.runasnewuser.cmd.keypath' Root='HKCU' Key='Software\Microsoft\RunAs\KeyPaths' Type='string' Value='RunAsNewUser.cmd' KeyPath='yes' />
              <RemoveFolder Id='pu.Runas' Directory='pu.Runas' On='uninstall'/>
              <RemoveFolder Id='pu.Microsoft' Directory='pu.Microsoft' On='uninstall'/>
              <Condition>NOT (ALLUSERS)</Condition>
            </Component>
            <Component Id='pu.runasnewuser.reg.exe' Guid='C0DB0776-441A-4AB9-871A-5AF1F326FA0A'>
              <RegistryKey Id='pu.runasnewuser.reg.exe' Key='SystemFileAssociations\.exe\shell\Run as new user...\command' Root='HKCR' Action='createAndRemoveOnUninstall'>
                <RegistryValue Id='pu.runasnewuserCommand.exe' Type='expandable' Value='"[#pu.runasnewuser.cmd]" "%1" %*' />
              </RegistryKey>
              <RegistryValue Id='pu.runasnewuser.reg.keypath' Root='HKCU' Key='Software\Microsoft\RunAs\KeyPaths' Type='string' Value='RunAsNewUser.reg' KeyPath='yes' />
              <Condition>NOT (ALLUSERS)</Condition>
            </Component>
            <Component Id='pu.runasnewuser.reg.msc' Guid='C5B94A3B-7D87-4FC0-AC28-111B86679251'>
              <RegistryKey Id='pu.runasnewuser.reg.msc' Key='SystemFileAssociations\.msc\shell\Run as new user...\command' Root='HKCR' Action='createAndRemoveOnUninstall'>
                <RegistryValue Id='pu.runasnewuserCommand.msc' Type='expandable' Value='"[#pu.runasnewuser.cmd]" "%1" %*' />
              </RegistryKey>
              <RegistryValue Id='pu.runasnewuser.reg.msc.keypath' Root='HKCU' Key='Software\Microsoft\RunAs\KeyPaths' Type='string' Value='RunAsNewUser.reg.msc' KeyPath='yes' />
              <Condition>NOT (ALLUSERS)</Condition>
            </Component>
          </Directory>
        </Directory>
      </Directory>

The extra baggage is the HKCU keypath RegistryValue, and the RemoveFolder entries. Nothing crazy, but a little extra to be aware of. These are necessary because of things like roaming profiles.

The experience

You can install it and it goes through without any elevation. The installation is per-user by default. (Yay! Per-user works and has a smokin' experience, and supports all kinds of scenarios.)

If you want to install it per-machine, you need to launch it via this command:

msiexec /i RunAsNewUser.msi ALLUSERS=1

This is obviously not ideal - but there's a hidden hiccup. I thought that it would prompt for elevation if you specified ALLUSERS=1 - it does not. You get this error message:

It's not the end of the world. If you run the same command from an already elevated process (e.g. an elevated command prompt) the installation goes through just fine (as the error message implies). It's a bit of a shame, but I've confirmed with Carolyn that you can't build a single package that will elevate sometimes and sometimes not (because the flag is in the MSI summary information it can't be changed in-flight).

The best practice for building a per-user (without elevation) and per-machine app (with elevation)

Because of the limitations noted above, here's what is the best practice for building a per-user and per-machine app: Have a bootstrapper exe, and two separate MSIs (one per-user package and one per-machine package). If these are embedded in the bootstrapper exe as resources that are extracted at install, then you can a single download that installs either as per-machine or per-user.

Why? Well, not many folks are trying to do this at the moment. Of course, more will as Vista is on more and more computers - ultimately I think this is a huge step forward for keeping your computer free of malware. I think it's worth saying twice: I feel much better installing a program that doesn't require elevation to install - at a minimum I know it's not disabling my anti-malware software.

Other Resources

http://blogs.msdn.com/windows_installer_team/ - Get it straight from the horse's mouth

http://blogs.msdn.com/astebner/archive/2006/12/13/some-useful-things-i-have-learned-about-windows-installer-and-uac.aspx - Good intro article that doesn't bury you in information like Roberts' (great) blog entries

http://blogs.msdn.com/rflaming/archive/2006/10/01/uac-in-msi-notes-answers-to-questions-in-comments-from-earlier-blog-posts.aspx - Summary of Robert's huge series about MSI and UAC

http://blogs.msdn.com/rflaming/archive/2006/09/30/778690.aspx - Robert gives his take on the question: Should I write my installer as a Standard User install? If yes, how?

* I imagine that you don't really need two versions of the components because I imagine that you could change the directory location using a custom action that set it, but I just found things a lot simpler if I used two different components