Azure Functions OAuth 1.0 Authorization Header Generator

A semi-elegant way of navigating a rather clunky scenario, allowing you to create an OAuth 1.0 authorization header.

Info

Microsoft Custom Connectors are great, however they lack the ability to integrate custom APIs that use OAuth 1.0. As a work around I've hodgepodged this PowerShell script together based on elements from Miguel Gutierrez Rodriguez and That API Guy.

The intended use case is to have Azure deal with creating the authorization header, then pass it's output into a Power Automate HTTP Action "Authorization" header parameter.

The downside of this is that you need to pass the query parameters into both this function and the HTTP request you want to make.

I've chosen, for security (and simplicity), to store the API credentials within the function environment variables. This means you'll need to create a new function for each API you're using.

Contents

• Azure Setup
• Power Automate Usage
• Known Issues

Azure Setup

1. Go to Azure > All services > Functions App (you'll find it under the Compute heading)
2. Click on Create:
   • Select the Subscription
   • Select the Resource Group (or create a new one)
   • Enter a Function App name (e.g. TwitterApiAuthorization)
   • Leave Publish set to Code
   • Set Runtime stack to PowerShell Core
   • Set Version to 7.0
   • Choose the Region closest to your local
   • Click Review + create
   • Confirm your configuration, then click Create and wait for your function to be deployed
3. Once deployed, open the function app you just created
4. Navigate to Functions (conveniently under the Functions heading)
5. Click Create:
   • Set the Development environment to Develop in portal
   • Set the Template to HTTP trigger
6. You'll be redirected to the newly created function, click on Code + Test
7. Copy raw contents from OAuth.ps1 and paste it into your functions run.ps1 file, then click Save
8. Navigate to Integration in the function:
   • Click HTTP (Request) and set the Selected HTTP methods that you require (it's best to include only the ones that you're going to use to avoid accidents)
   • Click Save
9. Navigate back to the functions app (easiest way I've found is to go to Overview, and then clicking on the Functions app link)
10. Navigate to Configuration (under the Settings heading)
11. Here we're going to be creating the API credentials environment variables using the names as follows; 'apiConsumerKey', 'apiConsumerSecret', 'apiAccessToken', 'apiAccessTokenSecret'). For each:
    • Click New application setting
    • Set the Name accordingly
    • Set the Value to your corresponding API credential
    • Click OK to confirm each entry
12. Navigate back to Functions, open the function you created earlier
13. Click Get Function Url and save it for later

Power Automate Usage

1. Go to Power Automate
2. Click Create > Instant cloud flow
3. Name the Flow
4. Select the Manually trigger a flow trigger, then click Create
5. Add a New step > Initialize variable action
   • Rename the action to URL
   • Set Name to URL
   • Set Type to String
   • Set Value to the API URL you want to make the request (don't include the query parameters in the URL)
6. Add a New step > HTTP action
   • Rename the action to Authorization Header
   • Set Method to the same method that you're requesting the API with
   • Set URI to the function URL that we saved earlier
   • Add a Header parameter called BaseUrl and set the value to the URL variable (@{variables('URL')})
   • Add any additional headers, or queries as required
7. Add another New step > HTTP action (this will be for the actual API request)
   • Set Method to the required method (it should be identical the previous step)
   • Set URI to the URL variable (@{variables('URL')})
   • Add a Header parameter called Authorization and set the value to the Body of the Authorization Header action (@body('Authorization_Header'))
   • Add any additional headers, or queries as required (they should be identical the previous step)
   • Add Body content if making a PUT, or POST request (if required)
8. Click Save
9. Click Test
   • Select Manually, and then click Test
   • Click Run flow, then click Done
   • Sit tight while it runs
10. Success (hopefully; see Known Issues)!

Known Issues

• Power Automate may return the Authorization Header step as Unauthenticated. To fix this go to the functions app > open the function > Integration > click HTTP (Request) > set Authorization level to Anonymous. Be aware, this is unsecure and will leave your function (and it's abilities) exposed to anyone with the URL