Wednesday, 1 November 2017

Using a CDN for Custom User Actions

Problem:  I need to inject JavaScript into a couple of hundred thousand site collections and subsites using a Custom User Action.  I want to use a CDN.  Governance will not let me add to the layouts folder on the WFE's.  Using a CDN for a CUA is causing the blank page.

Initial Hypothesis:  I don't want to deploy the same JS file hundreds of thousands of times into the local site collections.  As updating and storage are crazy.  I want a CDN like behaviour, and the closest I can get is to modify the hive directory on each SharePoint on-prem. farm that allows me to reference the JS.  I do have several farms and IT governance won't let me modify the WFE's.

Tobias Lekman has an excellent comprehensive overview of the CUA issue:

Doing the usual testing, bizarrely I can use anonymous for my CUA JS file.
When I allow external access on my personal public O365 E3 tenant, I can use this URL, the CUA works perfectly.  My client does not have an Office 365 external public tenant I can use, so an Akamai (or another CDN)CDN and fake the validation.  It's either SP URL validated, or I need to load it differently if I want to use a CDN.  I used an Akamai CDN and added /_layouts/15/ into the URL using folders, and the CDN started working for my CUA. e.g.

Possible Resolution:
  1. Local Site Collection uploaded files
  2. CDN assuming the JS location has: 


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