Webmentiond and redirects

For the last months I’ve been getting tons of mentions from Hyde as we comment on each other’s thoughts but something about them made webmentiond always mark them as “invalid” on my side. I was immediately quite certain that it had to have something to do with redirects as the mentions where coming from “http” while his blog usually serves content via HTTPS, but I simply couldn’t find the issue and, to be frank: The pain wasn’t big enough. I simply created the mentions manually 🙃

Yesterday, I again got two mentions and again they were marked as invalid but this time I went bug-hunting. The redirect counter had a little bug. Whenever webmentiond finds a link, it follows it before analysing the underlying document. In order to avoid endless redirects I added a little counter. If the number of redirects exceeds that counter, the mention is marked as invalid and we’re done.

There are some situations, though, where I simply don’t care about the number of redirects and in those cases I set the counter to -1. The bug was now, that I had forgotten to also handle that special value:

client := &http.Client{}
client.CheckRedirect = func(r *http.Request, via []*http.Request) error {
    if len(via) > cfg.MaxRedirects {
        return errors.New("too many redirects")
    }
    return nil
}

Nothing in that little code snippet from pkg/webmention/verify.go tells the code to handle -1 somehow different from any other value. Getting a redirect and the value is -1? Too bad! One is more than -1 and so it’s invalid.

If you’re using a build that was made on 2020-09-12 or later, this should be fixed now. That being said, I actually don’t know why I wouldn’t care about the number of redirects and so I’ve now set it to 10 by default (you can override it using --verification-max-redirects <VALUE> if that value doesn’t work for you 🙂

Do you want to give me feedback about this article? Please send it to comments@zerokspot.com.

Alternatively, I'm also experimenting with Webmentions. If you write a post on a blog that supports this technique, I should get notified about your link 🙂