Automating OAuth 1.0 Authorization header for Sellsy CRM API integration

How To
,
1

Hello Make Community! :waving_hand:

I’m a French beginner in automation and I need your help with a challenging OAuth 1.0 integration (at least for me :sweat_smile:).

My Goal

I want to automate API calls to my CRM (Sellsy) using Make’s HTTP module. The integration works perfectly when I manually create the OAuth 1.0 Authorization header in Postman, but I can’t figure out how to automate this header generation in Make.

What Works (Manual Process)

In Postman, I can successfully generate this OAuth 1.0 Authorization header:
"
OAuth oauth_consumer_key=“…”,oauth_token=“…”,oauth_signature_method=“HMAC-SHA1”,oauth_timestamp=“1749217218”,oauth_nonce=“SJ3HbEVKegK”,oauth_version=“1.0”,oauth_signature=“e%2FLrQh74zijApFt4SV1Qtp1S%2FBQ%3D”
"

My Current Scenario Setup

  1. compose a string: Generating OAuth nonce
  2. JavaScript module: Attempting to generate HMAC-SHA1 signature
  3. HTTP module: Making API call to Sellsy

The Problem

I’ve tried using AI assistants (GPT-4-mini and Claude 4) to generate JavaScript code for the HMAC-SHA1 signature, but I keep getting errors like:
SyntaxError: ‘return’ outside of function, ReferenceError: CryptoJS is not defined, Empty Output / No Result in Bundle, SyntaxError: Missing semicolon, Still Empty Output After Fixing Syntax, etc., etc.

What I’ve Tried

  • Multiple JavaScript implementations for OAuth signature generation
  • Different ways to structure the code in Make’s JavaScript environment
  • Various approaches suggested by AI

What I Need Help With

  1. How to properly generate the oauth_signature using HMAC-SHA1 in Make’s JavaScript environment (or other solutions)
  2. Correct way to structure the JavaScript code so it works in Make
  3. Any working examples of OAuth 1.0 automation for Sellsy or similar CRMs

Additional Info

  • I have my consumer key, consumer secret, token, and token secret from Sellsy
  • The API calls work perfectly in Postman with manual OAuth headers
  • I’m comfortable sharing screenshots of my scenario if that helps

Has anyone successfully automated OAuth 1.0 signatures in Make before? Any guidance would be incredibly appreciated!

Merci beaucoup! :folded_hands: