Use your own domain as an alias of your Mastodon handle.
When presented with a string like ps@infosec.exchange, Mastodon clients use the WebFinger protocol to retrieve a JSON document pointing to resources related to this account.
We can make use of this by proxying requests to our own custom domain at /.well-known/webfinger to the actual Mastodon instance using Cloudflare Workers.
sequenceDiagram
actor C as Client
participant W as Cloudflare Worker
participant M as Mastodon Instance
C->>+W: GET https://pstadler.dev/.well-known/webfinger<br>?resource=acct:ps@pstadler.dev
Note over W: Find target for alias in mapping:<br>ps@pstadler.dev → ps@infosec.exchange
W->>+M: GET https://infosec.exchange/.well-known/webfinger<br>?resource=acct:ps@infosec.exchange
M-->>-W: Response for ps@infosec.exchange
W-->>-C: Response for ps@infosec.exchange
Configure your aliases at the top of webfinger.js. Multiple entries are supported.
const MAPPING = new Map([
['ps@pstadler.dev', 'ps@infosec.exchange'],
['foo@pstadler.dev', 'bar@example.org']
])You can test this worker locally using miniflare.
$ npm install
$ npm run dev
$ curl http://127.0.0.1:8787\?resource\=acct:ps@pstadler.dev
{"subject":"acct:ps@infosec.exchange","aliases":["https://infosec.exchange/@ps","https://infosec.exchange/users/ps"],"links":[{"rel":"http://webfinger.net/rel/profile-page","type":"text/html","href":"https://infosec.exchange/@ps"},{"rel":"self","type":"application/activity+json","href":"https://infosec.exchange/users/ps"},{"rel":"http://ostatus.org/schema/1.0/subscribe","template":"https://infosec.exchange/authorize_interaction?uri={uri}"}]}Change values in wrangler.toml according to your needs.
# Either make sure `wrangler` is available on your system, or run
# `npm install` and add `./node_modules/.bin` to your PATH variable.
$ wrangler login
$ wrangler publish
$ curl https://pstadler.dev/.well-known/webfinger\?resource\=acct:ps@pstadler.dev
{"subject":"acct:ps@infosec.exchange","aliases":["https://infosec.exchange/@ps","https://infosec.exchange/users/ps"],"links":[{"rel":"http://webfinger.net/rel/profile-page","type":"text/html","href":"https://infosec.exchange/@ps"},{"rel":"self","type":"application/activity+json","href":"https://infosec.exchange/users/ps"},{"rel":"http://ostatus.org/schema/1.0/subscribe","template":"https://infosec.exchange/authorize_interaction?uri={uri}"}]}As of early 2023, some native Mastodon clients don't seem to make use of WebFinger when searching for users, which will result in your profile not being found with this approach.