terdut-server/SERVICE-ACCOUNTS.md

Service accounts: a scoped, non-human credential type

This is a design note for a feature, not an implementation plan — it exists to propose the shape before writing code. It's raised directly by terdut-operator (a separate repo, no shared code — see its DESIGN.md §6, §9, §13), which needs a credential for unattended, repeatable API access and currently has no good one available. Anything automating terdut-server long-term (this operator, CI, future integrations) hits the same gap, so this is written as a general primitive, not operator-specific.

The problem

terdut-server has two credential types today, and neither fits "an unattended process that manages teams/schedules/policies on someone's behalf":

• User API keys (api_keys, internal/api/users.go) are always tied to a real users row and carry that user's full rights — every team they're a member of, their admin flag if set. There's no kind/service marker distinguishing "a human's personal automation key" from "a login session," and no way to mint one scoped to less than the full user.
• Integration keys (integrations, internal/api/*teams*.go) are team-scoped, but narrowly: they authenticate exactly one inbound Alertmanager webhook call (POST /api/integrations/{key}/alertmanager) and nothing else. They're not a general management-API credential and shouldn't become one — overloading a narrow, one-way ingestion credential with broad read/write access would weaken the one property that makes it safe to embed in an Alertmanager config today.

The result: any automation that needs to create teams, set escalation policies, manage dead-man switches, or rotate integration keys has to hold a real human admin's or team owner's API key. That key is exactly as powerful as that person logging in — full team access, and full instance access if they're an admin. terdut-operator's design ran directly into this (its DESIGN.md §6): its described bootstrap/rotation flow assumed a repeatable, identity-scoped way to get a credential, and /api/bootstrap's actual behavior (single-shot per install, gated on COUNT(*) FROM users, confirmed via internal/api/users.go and charts/terdut-server/templates/bootstrap-job.yaml) doesn't provide one — it mints exactly one founding admin, once, ever.

Goals

• A credential type that isn't a human: doesn't touch OIDC group sync, login, session, or the is_admin/account-management semantics that come with a real users row.
• Two scopes matching the two shapes automation actually needs: instance-wide (create/list teams — what a server-owning controller needs) and team-scoped (manage one team's escalation policy, dead-man switches, integrations, schedule, OIDC group bindings — what a per-team controller or integration needs).
• Repeatable issuance and rotation — unlike /api/bootstrap, callable more than once, by anything that already holds admin rights, without destroying and recreating state to get a fresh credential.
• Visibly distinct from a human in every place identity shows up (audit trails, timeline entries, UI attribution) — a service account acting on a team should never be indistinguishable from a person.

Non-goals

• Not a general OAuth2/OIDC client-credentials flow — this is a bearer-token primitive matching the shape api_keys already uses (SHA-256 hash stored, raw key shown once at creation), not a new auth protocol.
• Not replacing integration keys — those stay as the narrow, one-way webhook credential they are today.
• Not modeling per-endpoint or per-verb permissions within a scope — instance and team are the only two scopes for now; finer-grained scoping is future work if a real need shows up.

Proposed shape

Schema

CREATE TABLE service_accounts (
    id          BIGSERIAL PRIMARY KEY,
    name        TEXT NOT NULL UNIQUE,       -- e.g. "terdut-operator"
    scope       TEXT NOT NULL CHECK (scope IN ('instance', 'team')),
    team_id     BIGINT REFERENCES teams(id) ON DELETE CASCADE,
    -- team_id required iff scope = 'team'; NULL iff scope = 'instance'
    created_by  BIGINT REFERENCES users(id),
    created_at  TIMESTAMPTZ NOT NULL DEFAULT now()
);

CREATE TABLE service_account_keys (
    id                  BIGSERIAL PRIMARY KEY,
    service_account_id  BIGINT NOT NULL REFERENCES service_accounts(id) ON DELETE CASCADE,
    key_hash            TEXT NOT NULL UNIQUE,
    name                TEXT NOT NULL,       -- e.g. "initial", "2026-Q4-rotation"
    created_at           TIMESTAMPTZ NOT NULL DEFAULT now(),
    last_used_at         TIMESTAMPTZ
);

Deliberately not a users row: no password_hash, no is_admin, no user_identities linkage, so it's structurally impossible for a service account to be pulled into OIDC group sync or password login. Multiple keys per account (mirroring api_keys' existing one-user-many-keys shape) so rotation is "mint a new key, revoke the old one," not "recreate the account."

Endpoints

• POST /api/service-accounts — instance-scope/admin-only. Body: {"name": ..., "scope": "instance"|"team", "teamID": ... } (teamID required iff scope=team, and caller must be that team's owner or a system admin). Returns the account plus its first raw key (shown once, same pattern as POST /api/users/{id}/api-keys). Safe to call again with the same name — see "idempotent lookup" below — unlike /api/bootstrap, which is inherently one-shot by design (it's answering "does any user exist yet," a question with no analogue once one already does).
• POST /api/service-accounts/{id}/keys — mint an additional key on an existing account (self-service-equivalent: instance admin for instance scope, team owner or system admin for team scope). Enables rotation without recreating the account or losing its identity/audit history.
• DELETE /api/service-accounts/{id}/keys/{keyID} — revoke one key, mirroring DELETE /api/users/{id}/api-keys/{keyID}.
• GET /api/service-accounts?name= — look up an existing account by name. This is what turns "I tried to create my account and got a conflict" into a normal flow instead of an error: a controller that expects to have already registered itself calls this first, and only falls through to POST if nothing comes back.

Auth middleware

Revised (this section originally described an aspiration that didn't match what shipped — TEAM-LOOKUP.md already caught one instance of that, and a fuller audit found three more; this is the corrected, as-built description, not the original proposal).

internal/api/middleware.go's dual resolution (Authorization: Bearer → apiKeyUser(), or session cookie → sessionUser()) and the service-account path (serviceAccountFor()) both resolve into one Caller type (internal/api/caller.go), not two parallel, un-unified context representations the way an earlier version of this server kept them. Every authorization predicate reads Caller's methods:

• Caller.IsAdmin() — true only for a human system administrator, never for a service account of either scope, under any circumstance. AdminOnly and requireSelfOrAdmin key on this alone — user management (POST /api/users, PUT /api/users/{id}/admin, etc.) and GET/PUT /api/admin/settings stay human-only, forever. The original text here claimed an instance-scoped service account satisfies AdminOnly "for team-creation/listing purposes" — that was never true of the shipped code (TEAM-LOOKUP.md caught the listing half; the creation half was always a separate, bespoke check in handleCreateTeam, not AdminOnly itself) and is not being made true now. Don't widen AdminOnly: every time this has come up, the fix has been a narrower, purpose-built capability instead (?name= lookups for teams and service accounts; now terdut-operator's own invite-minting feature for the one real gap this boundary left — how a human ever gets a first login on a no-OIDC, operator-managed install. See the bottom of "What this unblocks.")
• Caller.IsInstanceServiceAccount() — true only for an instance-scoped service account, never for a human (including a human admin). handleCreateTeam uses exactly this: a human creates a team by being a human (and becomes its owner); an instance-scoped service account creates one with no human owner at all. The two paths are not interchangeable, so this predicate deliberately does not also admit a human admin.
• Caller.Role(teamID)/TeamIDs() — a human's real team_members rows, or a team-scoped service account's single synthetic owner membership (serveAsServiceAccount). This is what makes requireTeamMember/ requireTeamOwner treat a team-scoped service account as owner-equivalent for that one team, with no separate branch needed in either function.
• Caller.ServiceAccountID() — used by OperatorModeBlock ("any service account passes") and by callerMayManageServiceAccount's self-rotation check.
• Caller.AsHuman() — the accessor every handler that needs a real user_id to act on behalf of must call and check, instead of reading a user off context unconditionally. Before the Caller type existed, four handlers did the latter and silently misbehaved for a service-account caller: handleMe and handleTestNotification 500'd (a zero-value user id that matches no row), handleDismissOnboarding silently no-op'd (UPDATE ... WHERE id = 0 affects nothing, still returns 204), and handleCreateInvite wrote that same zero value into invites.created_by — a real foreign-key violation, not just a wrong answer, since that column is nullable but was never passed as nil. All four now call AsHuman() and return an explicit 403 ("this endpoint is for human accounts only") or, for the invite case, leave created_by NULL the same way handleCreateServiceAccount already did for the analogous situation.

Team scope is owner-equivalent for every requireTeamOwner endpoint, membership and invites included — by design, not by an unclosed gap. An earlier version of this document flagged this as "acknowledged rather than closed," kept in check only by the social convention that nobody builds automation against those two routes. That convention is retired: terdut-operator's TerdutTeam controller now mints and revokes its own team's invite link through exactly this capability (its existing team-scoped credential, POST/DELETE /api/teams/{teamID}/invites), which is the real fix for the human-onboarding gap below — not a narrower carve-out of this capability. service_accounts_test.go's TestServiceAccount_TeamScopeManagesItsOwnInvites pins it.

A team-scoped account can also mint another service account scoped to its own team (handleCreateServiceAccount's callerOwnsTeam branch, which a team-scoped caller already satisfies for its own team via the synthetic membership above). Kept, not restricted, for the same reason: a team-scoped credential is that team's owner's reach, full stop — carving this one capability out while leaving membership/invites alone would be an arbitrary asymmetry. Pinned by TestServiceAccount_TeamScopeCanMintAnotherAccountForItsOwnTeam.

callerMayManageServiceAccount gained the one load-bearing fix this redesign exists for: an instance-scoped service account may manage (mint/revoke a key on) any team-scoped account, not only one admin, that team's human owner, or the account itself. handleCreateServiceAccount already let an instance-scoped caller create a team-scoped account for any team; this closes the gap where adopting or rotating one it didn't just create in the same call — exactly terdut-operator's documented adopt-on-409 crash-window recovery (its own DESIGN.md §5) — 403'd forever instead of succeeding (terdut-operator#3). Pinned by TestServiceAccount_InstanceScopeAdoptsAnExistingTeamScopedAccountsKey.

Anywhere identity is recorded for a human (incident timeline acknowledged_by/assigned_to, audit-relevant fields), a service-account caller is still coerced into a bare user_id of 0 today — Caller's new Identity() accessor exists for exactly this follow-up, but wiring it in needs a schema migration (an actor-attribution column distinct from user_id) and is deliberately out of scope here. Tracked separately, not by this document.

What this unblocks

Directly resolves terdut-operator DESIGN.md §6's two broken assumptions:

1. Bootstrap becomes single-purpose again. /api/bootstrap mints exactly the founding human admin, once. The operator's actual first-reconcile flow: call /api/bootstrap only on a genuinely empty install; otherwise (or immediately after, if it won the bootstrap race) call GET /api/service-accounts?name=terdut-operator, and POST one if it doesn't exist yet. From then on the operator never touches /api/bootstrap again.
2. Rotation becomes real. POST /api/service-accounts/{id}/keys + revoke the old one — no destructive DB-level workaround, no re-triggering a single-shot endpoint that can't fire twice.
3. Cross-namespace credential mirroring is no longer needed at all. terdut-operator's current design holds every credential — instance- and team-scoped alike — privately in the operator's own namespace, never in the namespace of the CR each one authenticates for; reconciliation happens entirely inside the operator's controller loop, so no CR owner ever needs read access to a terdut-server credential regardless of same- or cross-namespace serverRef. Team scoping is still what bounds the blast radius of any individual credential: a leaked team-scoped key exposes exactly one team's resources, never the whole server, which is what makes holding many credentials in one place (the operator's namespace) an acceptable trade rather than reintroducing the mirrored design's server-admin-equivalent-everywhere problem.
4. A human can get a first login on a no-OIDC, operator-managed install — without ever touching AdminOnly or /api/admin/settings. This was filed as terdut-server#23 ("no API path to create a human login after bootstrap") and diagnosed, at the time, as this server needing to let a service account through AdminOnly. It doesn't: the fix lives entirely in terdut-operator, because a team-scoped credential was already owner-equivalent for POST /api/teams/{teamID}/invites, and invite redemption (POST /api/signup with an invite token) bypasses signup_mode entirely — terdut-operator just never grew a feature to use either fact. Its TerdutTeam controller now mints and surfaces one via its own existing team-scoped credential (spec.invite, status.inviteSecretRef, see that repo's own docs), so a human joins a CRD-managed team by a real invite link, the same way anyone else would. terdut-server#23 is closed with this note once that feature ships — its named routes stay human-only, correctly, not a gap.

Suggested sequencing

Land this before terdut-operator implements any bootstrap/credential-handling code — that code would otherwise be written against the current one-shot, user-only credential model as a known-temporary workaround, which is wasted effort on a repo that currently has zero implementation to begin with.