Unauthorized error when getting sharepoint list attachment despite having "Files.ReadWrite.All" permission

Question

I am writing an ASP web application that can interact with a Sharepoint list, creating new items and updating existing items. We have an Attachments field in that list. Because accessing sharepoint list item attachment files is not available in the Graph API I am having to use the Sharepoint v1 REST API for that part of a web app. In Entra Id I have granted the application the "Files.ReadWrite.All" permission. When I call this endpoint to get the item details I get a link to the file:

https://{sharepointURL}/sites/{SiteName}/_api/web/lists/GetByTitle('{listName}')/Items('2323')?$expand=AttachmentFiles

It does give me information about the attached file, including the following URL:

https://{sharepointURL}/sites/{SiteName}/Lists/{ListName}/Attachments/2323/{fileName}.pdf

However, when I try and use that URL I get back 401 Unauthorized, but no further details. I can only assume I am missing some permission, as I am using the same authentication token I used for the original request. What am I missing here?

Answer 1

Hi @Josh Earel ,

The 401 Unauthorized error message in SharePoint typically indicates that you do not have the necessary permissions to access the list attachment.

1.To access sharepoint via a web url, first make sure you have access rights (e.g. read, edit, full control, not the “Files.ReadWrite.All” permission in the API) to the list item (attachment).

https://support.microsoft.com/en-us/office/customize-permissions-for-a-sharepoint-list-or-library-02d770f3-59eb-4910-a608-5f84cc297782

2.Try adding the suffix “?web=1” to the url.

https://{sharepointURL}/sites/{SiteName}/Lists/{ListName}/Attachments/2323/{fileName}.pdf?web=1

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Answer 2

I realized I was overthinking this as I had been doing so much work to get the API endpoint stuff working that I had just overlooked that this wasn't an API endpoint, it was providing a direct link to the actual file on sharepoint.