These may all produce the same content and therefore cause a duplicate content issue.
A Canonical Link is the URL that you have decided is the official version. For all the pages on your website you can indicate what the Canonical Link is. This way you can tell search engines to only index that particular version of the pages URL. In the above example you may decide the Canonical Link is website.com.
Well as per my knowledge Canonical links are uses to remove the duplication between same content of page, So that google should allow to crawl the pages. In other words it helps search engines figure out duplicate content issues.