SharePoint Rest API with OAuth and Pfx Cert: ID3035: The request was not valid or is malformed

Question

Hello, Can you help me fix this?

In the past few months the the Rest API for SharePoint was successful via the Pfx Certificate method.

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Now it's failing with an error!
{"error_description":"ID3035: The request was not valid or is malformed."}

I originally followed this method.
https://laurakokkarinen.com/authenticating-to-office-365-apis-with-a-certificate-step-by-step/

How to fix this?

Answer 1

Hi @kartrabby,

Granting access via Azure AD App-Only covers how to register an app with app-only permissions in Azure AD and how to use that app to interact with SharePoint using PnP PowerShell and the SharePoint PnP Sites Core library. Unfortunately, this resource doesn't cover how to use the app with the "plain" REST API. The basic steps to do this would be to use the Microsoft Authentication Library (MSAL) library to get an access token and then make REST API calls with that token included in the headers of the request.

You could refer to the nice article

Testing client certificate authentication to Azure API Management with Postman

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