ActivityPub: use Webfinger `subject` to support Mastodon split domain aka WEB_DOMAIN

[trbutler]

My Mastodon instance has a LOCAL_DOMAIN of "faithtree.social" and WEB_DOMAIN of "mastodon.faithtree.social." So, while it is accessed on the web at "mastodon.faithtree.social," the proper Fediverse identifier is "@trbutler@faithtree.social" (for example) not "@trbutler@mastodon.faithtree.social." However, when Bridgy bridges to Bluesky, the account adopts the WEB_DOMAIN, rendering it "@trbutler.mastodon.faithtree.social.ap.brid.gy" instead of the proper to the canonical handle "@trbutler.faithtree.social.ap.brid.gy."

Near as I can tell, web finger is properly configured.

Thanks for your help!

[snarfed]

Thanks for filing! Related: https://github.com/snarfed/bridgy/issues/1638

This is an interesting one. Bridgy Fed doesn't start from Webfinger, it starts from AP actor id URLs. Yours is https://mastodon.faithtree.social/users/trbutler . Nothing in your AP actor that I can see says to use faithtree.social instead of mastodon.faithtree.social. Looking at your Webfinger, the only thing I see is "subject": "acct:trbutler@faithtree.social", which I don't currently look at, but definitely could!

Your AP actor (pruned down a bit):

{
   "alsoKnownAs" : [
      "https://mastodon.cloud/users/Trbutler"
   ],
   "attachment" : ["..."],
   "devices" : "https://mastodon.faithtree.social/users/trbutler/collections/devices",
   "discoverable" : true,
   "endpoints" : {
      "sharedInbox" : "https://mastodon.faithtree.social/inbox"
   },
   "featured" : "https://mastodon.faithtree.social/users/trbutler/collections/featured",
   "featuredTags" : "https://mastodon.faithtree.social/users/trbutler/collections/tags",
   "followers" : "https://mastodon.faithtree.social/users/trbutler/followers",
   "following" : "https://mastodon.faithtree.social/users/trbutler/following",
   "icon" : {
      "mediaType" : "image/jpeg",
      "type" : "Image",
      "url" : "https://files.faithtree.social/accounts/avatars/109/762/503/392/984/571/original/3f58a809494a1dc3.jpg"
   },
   "id" : "https://mastodon.faithtree.social/users/trbutler",
   "image" : {
      "mediaType" : "image/jpeg",
      "type" : "Image",
      "url" : "https://files.faithtree.social/accounts/headers/109/762/503/392/984/571/original/0cefaf1528f2be20.jpg"
   },
   "inbox" : "https://mastodon.faithtree.social/users/trbutler/inbox",
   "indexable" : true,
   "manuallyApprovesFollowers" : false,
   "memorial" : false,
   "name" : "Timothy R. Butler",
   "outbox" : "https://mastodon.faithtree.social/users/trbutler/outbox",
   "preferredUsername" : "trbutler",
   "publicKey" : "...",
   "published" : "2023-01-27T00:00:00Z",
   "summary" : "<p>Pastor, <span class=\"h-card\" translate=\"no\"><a href=\"https://mastodon.faithtree.social/@littlehillschurch\" class=\"u-url mention\">@<span>littlehillschurch</span></a></span> and <span class=\"h-card\" translate=\"no\"><a href=\"https://mastodon.faithtree.social/@faithtreecf\" class=\"u-url mention\">@<span>faithtreecf</span></a></span> (outreach ministry). Editor, <span class=\"h-card\" translate=\"no\"><a href=\"https://mastodon.faithtree.social/@ofb\" class=\"u-url mention\">@<span>ofb</span></a></span>. Shakespeare lover, Apple/*nix geek in <a href=\"https://mastodon.faithtree.social/tags/StLouis\" class=\"mention hashtag\" rel=\"tag\">#<span>StLouis</span></a> <a href=\"https://mastodon.faithtree.social/tags/Missouri\" class=\"mention hashtag\" rel=\"tag\">#<span>Missouri</span></a>.</p><p><a href=\"https://mastodon.faithtree.social/tags/Christian\" class=\"mention hashtag\" rel=\"tag\">#<span>Christian</span></a> <a href=\"https://mastodon.faithtree.social/tags/ChurchHistory\" class=\"mention hashtag\" rel=\"tag\">#<span>ChurchHistory</span></a> <a href=\"https://mastodon.faithtree.social/tags/Reformed\" class=\"mention hashtag\" rel=\"tag\">#<span>Reformed</span></a> <a href=\"https://mastodon.faithtree.social/tags/Theology\" class=\"mention hashtag\" rel=\"tag\">#<span>Theology</span></a> <a href=\"https://mastodon.faithtree.social/tags/Aquinas\" class=\"mention hashtag\" rel=\"tag\">#<span>Aquinas</span></a> <a href=\"https://mastodon.faithtree.social/tags/Shakespeare\" class=\"mention hashtag\" rel=\"tag\">#<span>Shakespeare</span></a> <a href=\"https://mastodon.faithtree.social/tags/Photography\" class=\"mention hashtag\" rel=\"tag\">#<span>Photography</span></a> <a href=\"https://mastodon.faithtree.social/tags/Technology\" class=\"mention hashtag\" rel=\"tag\">#<span>Technology</span></a> <a href=\"https://mastodon.faithtree.social/tags/Apple\" class=\"mention hashtag\" rel=\"tag\">#<span>Apple</span></a> <a href=\"https://mastodon.faithtree.social/tags/Linux\" class=\"mention hashtag\" rel=\"tag\">#<span>Linux</span></a> <a href=\"https://mastodon.faithtree.social/tags/Perl\" class=\"mention hashtag\" rel=\"tag\">#<span>Perl</span></a> </p><p>Tags for Fediverse tools: <a href=\"https://mastodon.faithtree.social/tags/Searchable\" class=\"mention hashtag\" rel=\"tag\">#<span>Searchable</span></a> <a href=\"https://mastodon.faithtree.social/tags/fedi22\" class=\"mention hashtag\" rel=\"tag\">#<span>fedi22</span></a></p>",
   "tag" : [],
   "type" : "Person",
   "url" : "https://mastodon.faithtree.social/@trbutler"
}

Your Webfinger:

{
  "subject": "acct:trbutler@faithtree.social",
  "aliases": [
    "https://mastodon.faithtree.social/@trbutler",
    "https://mastodon.faithtree.social/users/trbutler"
  ],
  "links": [
    {
      "rel": "http://webfinger.net/rel/profile-page",
      "type": "text/html",
      "href": "https://mastodon.faithtree.social/@trbutler"
    },
    {
      "rel": "self",
      "type": "application/activity+json",
      "href": "https://mastodon.faithtree.social/users/trbutler"
    },
    {
      "rel": "http://ostatus.org/schema/1.0/subscribe",
      "template": "https://mastodon.faithtree.social/authorize_interaction?uri={uri}"
    },
    {
      "rel": "http://webfinger.net/rel/avatar",
      "type": "image/jpeg",
      "href": "https://files.faithtree.social/accounts/avatars/109/762/503/392/984/571/original/3f58a809494a1dc3.jpg"
    }
  ]
}

[trbutler]

Interesting, thank you! I guess Mastodon only exposes the difference between LOCAL_DOMAIN and WEB_DOMAIN in Webfinger then? I actually regret splitting them, much like it sounds like the person on the other ticket you referred to, although since one is not supposed to change it after beginning usage, I'm stuck with the configuration. The tricky thing is if anyone looks on the web, it will say my user id is @trbutler@faithtree.social, so the bridge ends up being unexpectedly in a different location. Picking up support for paying attention to subject seems like it would be a wonderful help for this sort of configuration. (Short of Mastodon upstream adding an explicit reference to the account handle in the AP actor.)

[qazmlp]

(Short of Mastodon upstream adding an explicit reference to the account handle in the AP actor.)

There's work on that being done here, could arrive relatively shortly for certain software: https://socialhub.activitypub.rocks/t/fep-2c59-discovery-of-a-webfinger-address-from-an-activitypub-actor/3813

[cooperaj]

Just adding my plus one to this boat.

Would be nice if I wasn't bridged to bsky with 'social' in my handle when it's not actually my "proper" handle.

[tesaguri]

There is now a community group report that describes the reverse discovery mechanism of the WebFinger username of a given ActivityPub actor:

https://www.w3.org/community/reports/socialcg/CG-FINAL-apwf-20240608/#reverse-discovery

[jfietkau]

I have started a project (combined minimal test case and documentation) to keep track of the implementation status of split-domain awareness in different ActivityPub platforms. Bridgy Fed is listed there too, with a link to this very issue: https://correct.webfinger-canary.fietkau.software/#implementation-status

[snarfed]

Oh wow, awesome project, congrats on launching it @jfietkau, and thank you for including Bridgy Fed!

[jfietkau]

Don't praise me too much, if the AP-verse at large ever gets around to fully implementing my checklist then that'll enable people to change both their account names and handle domains willy-nilly, and I bet that would cause you all sorts of headaches over here. 😛 But thank you!

[joshtriplett]

I'm having the same problem here; I'm showing up as @josh@social.joshtriplett.org, rather than @josh@joshtriplett.org. I think I've got everything properly configured.