How to authenticate the user with Designer workflow 2013 and REST API?

Question

I've to call the web service for POST operation.

I'd set "Workflows can use app permissions" but still not getting result. And getting the following error-

{"error":{"code":"-2147024891, System.UnauthorizedAccessException","message":{"lang":"en-US","value":"Access denied. You do not have permission to perform this action or access this resource."}}}

Answer 1

In your REST call are you specifying the X-RequestDigest parameter in its headers? If not, you need to. Every REST call needs to be authenticated.

You can find an excellent step-by-step guide on how to do this here:

http://blog.appliedis.com/2014/10/09/sharepoint-designer-2013-workflow-working-with-web-services/

In case the link goes dead I copy the text below:

When working with the SharePoint REST services you need to authenticate the requests.

There is a service available to take care of this. This step will build a Dictionary object for the request headers and then call the service to get the security token. First we’ll create a new Dictionary action, output it to a variable called contextHeaders, and create entries for Accept, Content-Type, and Content-Length headers. For Accept and Content-Type, we want to use “application/json; odata=verbose.” SharePoint 2013 REST calls require the second parameter, “odata=verbose,” because while the OData specification supports other options, SharePoint’s services do not.

Next, we’ll create a “Call HTTP Web Service” action to get the token.

Also, you must use the POST method to get this token. While you would expect to use a GET call, the reason for POST is to improve security against “shady” requests. Next, we’ll need to assign a variable to the ResponseContent of the action. This is a Dictionary object we’ll call contextResponse. Finally, we need to set the RequestHeaders property of the action to our contextHeaders dictionary.

Right-click on the action and select “Properties…” to access the action’s properties window.