The HTTP node can be used to access services using REST APIs - so it could be used to access file data in SharePoint (though I've not tried it myself).
The documentation on the SharePoint REST API is here:
Working with folders and files with REST | Microsoft Docs
This is the API to retrieve a file:
GET https://{site_url}/_api/web/GetFolderByServerRelativeUrl('/Folder Name')/Files('{file_name}')/$value
Authorization: "Bearer " + accessToken
You would need to obtain your access token before the API could be used.
There is a roadmap candidate item to create nodes to access SharePoint365. However, this is not assigned to a target release at this time.