halkyon/packages/halkyon_base_server/README.md

halkyon_base

What every Halkyon server has, as a Serverpod module (halkyon_base_server, with its generated client halkyon_base_client): signing in, the account's ways in and its deletion, the pruning of what nobody can return to, what an instance tells its apps before anyone signs in, and people's public profiles with their pages on the web, which the instance's register keeps (ADR 0016). It comes from Halkyon Learn's server, whose rules it keeps.

What it provides

Endpoints, under the nickname base in a host's client (client.modules.base.emailCode):

Endpoint	Methods	Who may call
anonymousIdp	login (Serverpod's anonymous sign-in, at most 30 new accounts per IP address and hour)	anyone
gitHubUpgrade	upgrade: links a GitHub account to the caller, who becomes identified	signed in
gitHubSignIn	signIn: a session for whoever has that GitHub account	without a session
emailCode	sendCode, verifyCode: a code by mail; a new address becomes the caller's, another person's gives a switch token	signed in
emailSignIn	signIn: a session for the person a switch token names	without a session
account	delete, signInWays	signed in
instance	basics: the app it serves, GitHub's client ID if any, whether email sign-in is on, the source link, the oldest app build, where data and backups are	anyone
profile	mine, save, checkHandle, checkLinks (at most 10 an hour), setAvatar, removeAvatar, remove: the caller's own public profile	identified
profiles	byHandle: anyone's public profile, whatever the handle's case	signed in

• GitHub keeps only the numeric GitHub ID, in Serverpod's own table; email keeps only HMAC-SHA256 of the address, keyed with emailSignInPepper (email_identity), and its codes as Argon2id hashes (email_code_request). Codes are eight Crockford characters, valid 15 minutes, 3 tries; at most 3 an hour per address and 10 per network.
• Profiles: a handle as Mastodon's (1 to 30 letters, digits or underscores, unique whatever their case, a few reserved for the instance), fixed once the host says so (fixHandle; Halkyon Learn at the first publish); a display name, a bio, up to 4 links verified as Mastodon verifies them (rel="me" back to the profile's page, fetched over HTTPS from public addresses only), and an avatar, a PNG of at most 1 MB in the public storage at avatars/<SHA-256>.png. The page is at https://<account domain>/@handle (ACCOUNT_DOMAIN, else the server's public host), served by addProfilePageRoute, in English or German, its foot what the host's profilePageNote says.
• Refusals are GitHubSignInRefusedException, EmailSignInRefusedException and ProfileRefusedException, each with a reason; ProfileNotFoundException where there is no profile.
• For the host's own code, package:halkyon_base_server/base.dart: the configuration, tokenManagerBuilders and identityProviderBuilders, the identified scope and grantIdentified, deletePerson, the pruning (pruneAbandonedAnonymousPeople, forgetOldSignUpAttempts, forgetExpiredEmailCodes), short codes, sourceCodeUrl, dataLocation, backupLocation, people's profiles as the host's code reads them (profileOf, profilesOf, personWithHandle, fixHandle; saveProfile for its tests), accountDomain, profilePageUrl, addProfilePageRoute, the register (AccountRegister), and the models. A host never reads the profiles' table itself.

Taking it into a host

1. Depend on both packages by path, within the repository's workspace (an app's packages sit in apps/<app>/):

   # the server's pubspec.yaml
   halkyon_base_server:
     path: ../../../packages/halkyon_base_server
   # the client's pubspec.yaml: the same with halkyon_base_client
   

2. Name it in the server's config/generator.yaml:

   modules:
     halkyon_base:
       nickname: base
   

3. Configure it once, before the pod starts, and run its authentication and pruning:

   final pod = Serverpod(args); // the host's generated Serverpod
   HalkyonBase.configure(
     pod,
     HalkyonBase(
       app: 'todo', // its apps accept only instances naming it; never change it
       appName: 'Halkyon Todo', // in sign-in mails
       upstreamSourceCodeUrl: 'https://code.halkyon.app/project-halkyon/halkyon_todo',
       minimumAppBuild: 1, // raise it in the commit that breaks older apps
       deletePersonData: [deleteTodosOf], // the host's own data of a person
       profilePageNote: ( // what profile pages say of the app at their foot
         english: 'On Halkyon Todo, a to-do list:',
         german: 'Auf Halkyon Todo, einer Aufgabenliste:',
         link: Uri.parse('https://halkyon.app/todo'),
       ),
     ),
   );
   pod.initializeAuthServices(
     tokenManagerBuilders: tokenManagerBuilders,
     identityProviderBuilders: identityProviderBuilders(pod),
   );
   

   Serve the profile pages on its web server: addProfilePageRoute(pod), after any literal routes of its own.

   Then schedule the pruning in a future call of the host's own: daily pruneAbandonedAnonymousPeople, hourly forgetOldSignUpAttempts and forgetExpiredEmailCodes.

4. A host's deletion (PersonDataDeletion) runs inside deletePerson's transaction, after the person's sessions ended and before their identities and the person go, in the order given; it deletes the person's rows in the host's tables, and returns what has to wait until the deletion is committed (files outside the database), or null. Pruning deletes through the same function.

5. Create the host's migration. A host taking the tables over from its own models (as Halkyon Learn does) finds no change once its copies are gone: Serverpod matches tables by name, and these are identical. create-migration --empty then records the module's version, with no SQL besides.

The passwords it reads: serverSideSessionKeyHashPepper; for GitHub githubClientId and githubClientSecret; for email emailSignInPepper and emailSmtpHost, emailSmtpPort, emailSmtpUser, emailSmtpPassword, emailFrom. Never change either pepper once people sign in: every session or address hash would be lost. The environment: ACCOUNT_DOMAIN, the domain handles are on, which can never change once anyone follows one; SOURCE_URL, DATA_LOCATION, BACKUP_LOCATION: where the instance keeps people's data and its backups, each EU, a country's code (DE) or a subdivision's (ISO 3166-2, US-CA, DE-BY), the backups also none; where the disks are, not which law governs.

Developing it

serverpod --no-analytics generate here after changing a model or an endpoint, and serverpod --no-analytics create-migration after changing a table. Tests need no Docker: dart test here starts Serverpod's embedded PostgreSQL. They read config/passwords.yaml (git-ignored) with throwaway values under test: for database, serviceSecret, serverSideSessionKeyHashPepper and emailSignInPepper.

Licences

The server package is under the Server Side Public License 1.0, as the Halkyon servers are; the client package under the GNU Affero General Public License 3.0 or later, as the Halkyon apps are. So each combines with its counterpart in a host exactly as the host's own do.