Managed VPP via Self Service

A goal I have had for some time was to get away from users simply “requesting” their VPP apps through Self Service and being able to grant them the ability to self-assign those apps (as long as they were eligible).  After doing some work on a little HTML scraping of the JSS I finally have working code to achieve this goal.

HTML Scraping?

If we’re going to allow a user to self-assign some App Store apps we need the ability to ensure there are enough available seats for them to do so.  As of version 9.62, Content as it relates to managed VPP seats is not accessible using the REST API.  There is no quick call we can make to view unassigned VPP content.

What I spent a little time working on was the method by which I could load an Advanced Content Search and parse the results.  This is different that just making an REST API request to the JSS using HTTP basic authentication (this is what you see in pretty much all examples of interacting with the JSS REST API, among others).  The web app uses session cookies for this.

Enter Python (as always, with me).

Using some code I already wrote for getting a cookie for the JIRA REST API on another project (Nessus2JIRA – you’ll hear more about that later), I wrote a new mini JSS class that incorporated both HTTP basic authentication for some the API calls that would need to be made for User Extension Attributes as well as obtaining a session cookie for when we needed to pull up an advanced content search (the web interface and the REST API do not share authentication methods!).

If you’re looking for that already, don’t worry.  There’s a GitHub link at the bottom (where I am now keeping all my code for you guys to grab) that contains the entire sample script for Self Service.

I’ve seen some impressive examples of HTML scraping in shell scripts using SED and AWK.  For what I’m extracting from the HTML of the JSS page I found the solution to be fairly simple.  Let me break it down:

The Advanced Content Search

We need the ability to pull in the information on all of the OS X apps that we are distributing via managed VPP so we can parse out the app in question and if it has unassigned seats for the user.  In my environment I had two content searches created for us to reference this at a glance for both iOS and OS X.  They report the Content Name, Total Content, the Assigned Content and Unassigned Content for a single criteria: Content Type: is: Mac app (or iOS app for the former).

For the script we only care about Unassigned Content so we really only need that and the Content Name, but the other fields are nice if you are pulling up the search in the GUI to view and don’t conflict with how we’re going to perform the HTML scraping.

Of course, there’s still the problem with generating the search.  Going to the URL to view the search requires us to click the View button to get our results.  As it so happens, Zach Halmstad recently dropped some knowledge on a thread for a feature request related to sharing search result links:

In Zach’s words: “…If you look at the URL of the group or search, it will look like this:  smartMobileDeviceGroups.html?id=2&o=r  If you change the value of the “o” parameter to “v” so it looks like this:  smartMobileDeviceGroups.html?id=2&o=v  It should forward the URL onto the search results.”

Boom.  We can perform an HTTP request using that parameter value and get back a search result!

Now, how do we extract that data? I took a look through the HTML and found the data which is populated into a table by some JavaScript.


	var data = [

	['OS X Server',"20","17","3",],

	var sortable = new Array;

It’s just an array which means I could convert it into a native Python list type and iterate over the values with ease.  As I’m being very specific about what data I need I came up with a solution for finding and extracting these lines:

  1. I took the response from my HTTP request, the HTML of the page, and then converted it into a Python list at every newline character.
  2. I began a loop through this HTML list looking for the index value matching “\tvar data = [“ which denotes the beginning of the array.
  3. I restarted my loop at the above index +1 and started concatenating the lines of the array together into a single string (skipping the blank lines). Once I reached the line matching “\tvar sortable = new Array;” I killed the loop.
  4. I evaluate my string and out comes the list containing each entry of my VPP content with the values.

Here’s what that code looks like in action:

# Breaking up the returned HTML into a list
html =

# The applist string starts with the open bracket for our list
applist = "["

# Here is the loop through the html list pulling 
for item in html:
    if item == "\tvar data = [":
        for line in html[html.index(item) + 1:]:
            if line == "\tvar sortable = new Array;":
            elif line.rstrip():
                applist += line.strip(';')[1:]

# We need the 'ast' module to perform the eval into a list
import ast
applist = ast.literal_eval(applist)

Parsing through this new list is now super easy:

for x in applist:
    if int(x[-1]) > 0:
        print(x[0] + " has " + x[-1] + " seats available.")

Keynote has 2 seats available.
OS X Server has 3 seats available.
Pages has 1 seats available.

The Golden Triangle: Extension Attribute to Smart Group to VPP Assignment

All of the VPP assignments in my environment are handled via User Extension Attribute.  This was done for a number of reasons including the easy of dropping a user into scope for one of these apps, but also to future-proof us for when we would start leveraging the API to handle those assignments.

The setup is very simple.  Each App Store app that we distribute through managed VPP has its own extension attribute.  Let’s take Baldur’s Gate as an example (if you don’t have this available to your org, look deep inside and ask yourself, “why not?”).  For every VPP extension attribute there are two available values from a pop-up menu: Assigned and Unassigned.

(Note: since you can set a pop-up menu back to a blank value, ‘Unassigned’ is actually unnecessary from a technical standpoint, but if you have other IT staff working in a JSS it makes more visual sense to set value to ‘Unassigned’ instead of nothing in my opinion) 

Once the user extension attribute is in place create a matching Smart User Group with the sole criteria being the value is set to ‘Assigned.’  Now you make this smart group the scope for a VPP Assignment that only assigns that app.  That’s it!  You now have an App Store app that you can dynamically assign via the JSS REST API (or with ease by flipping values directly on a user’s record).

Updating a User Extension Attribute

The last piece of this is using the REST API to flip the User Extension Attribute for the logged in user to ‘Assigned’.  If you want to get in deeper with the API you can check out my two earlier blog posts “The JSS REST API for Everyone” which give a general introduction and overview.

The two pieces of information you need to update a User Extension Attribute are the user’s username or ID and the ID of the extension attribute that will be updated.  Perform a PUT on either of these resources with the following XML to change the value (be sure to update the ID values!):



(Note: this is pretty much what you would do for almost ANY extension attribute in the JSS)

Check Out the Full Script on GitHub

As promised, here is a full working example of the script for you to grab:

View the README for a breakdown of how to setup the policy (and be sure to do this in a test environment).  The one omission in this code is inside the function that is triggered when there are no available seats of the app to assign:

def create_ticket():
    """This function would generate a ticket with information on the app and user
    IT staff would purchase additional seats of the app and then to assign it

    This function would be called where the number of available seats was not greater than 0
    Customize to suit your environment"""
    print("Creating ticket.")

In my case I would have code in here to take the different values that were passed to the script and generate a Zendesk ticket on the behalf of the user informing IT that more seats needed to be purchased and that the user should be assigned this app once the purchase process is complete.  That takes the onus off of the user to perform yet another step when they are informed the app isn’t immediately available.

If you’re also a Zendesk user you can review a Python script I have here that creates a request ticket for a user from Self Service:

Otherwise, you should feel free to add your own code for whatever remediation action you would want to take should there not be any available seats for the user.  If you have questions about that please feel free to reach out to me and we can discuss it.

Take it Further

The entire setup described above allows for apps to be assigned and unassigned easily.  You can take the existing code and modify it to allows users to voluntarily return managed VPP seats if they are no longer using them.  The script produces dialog prompts in the event of an error, unavailable seats or success in assigning the app.  You’ll notice these are embedded AppleScripts (a little PyObjC fun that gets around needing to use Tkinter) so you can work with those as well to further customize the feedback to your users.

And as I already said, feel free to hit me up if you have questions.

Happy New Year!


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