trails/openspec/changes/unify-auth-completion/specs/authentication-methods/spec.md at fc2f938cf5b5bff832e874c8f1fa23e538148da2

Ullrich Schäfer d64c47614d

Implement completeAuth chokepoint + caller migration

Implements all of unify-auth-completion (12/14 tasks done; manual
smoke + archive-time spec sync remain).

Design refinement during implementation: completeAuth supports two
response shapes via a `mode` parameter:
- mode: 'redirect' (loaders / direct browser navigation; auth.verify.tsx)
- mode: 'json' (action handlers called by imperative fetch from
  client forms; api.auth.login, api.auth.register)

Both modes share createSession + safeReturnTo + Set-Cookie. JSON mode
carries `{ ok: true, step: "done", redirectTo }` (the `step` field
preserves the existing client-form check).

Why two modes: passkey ceremonies are inherently imperative
(start → browser WebAuthn API → finish), so action handlers can't
move to <Form>/useFetcher. Picking option (B) from the design grill —
the chokepoint owns destination selection while clients navigate —
required this dual shape. The 3 hardcoded client-side targets
(returnTo ?? "/", "/", "/?add-passkey=1") collapse into 1 server-side
sanitization pass (safeReturnTo) inside completeAuth.

New module:
- apps/journal/app/lib/auth/session.ts: cookie session storage
  (sessionStorage, createSession, getSessionUser, destroySession)
  moved from auth.server.ts. Legacy import path kept via re-exports
  with @deprecated JSDoc.
- apps/journal/app/lib/auth/completion.ts: completeAuth + safeReturnTo.
- apps/journal/app/lib/auth/completion.test.ts: 10 contract tests
  covering both modes, returnTo sanitization (path-relative, protocol-
  relative, absolute-URL, malformed), Set-Cookie attachment, redirect
  status, JSON shape.

Caller migration:
- api.auth.register.ts passkey-finish → completeAuth(json)
- api.auth.login.ts finish-passkey → completeAuth(json)
- api.auth.login.ts verify-code → completeAuth(json)
- auth.verify.tsx magic-link consumer → completeAuth(redirect)

Client form updates:
- auth.login.tsx: pass returnTo in fetch body, read result.redirectTo
  on done.
- auth.register.tsx: pass returnTo: "/?add-passkey=1" for the magic-
  link verify-code path (preserves the post-register passkey prompt
  via the chokepoint's safeReturnTo, instead of hardcoding it
  client-side).

Verified:
- pnpm typecheck && pnpm lint: green across all 15 workspaces.
- pnpm --filter @trails-cool/journal test: 126 passed.
- pnpm test:e2e auth: 4/4 passed without modification — confirms the
  refactor is behaviour-preserving for the user-facing flows that
  matter most (passkey register + login).

Spec delta in openspec/changes/unify-auth-completion/specs/ applies at
/opsx:archive time.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

2026-05-08 02:38:15 +02:00

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ADDED Requirements

Requirement: Single web auth completion chokepoint

Every successful web authentication flow — passkey register-finish, passkey login-finish, magic-link 6-digit-code verify, magic-link click-through verify — SHALL complete by calling a single completeAuth function at apps/journal/app/lib/auth/completion.ts. The function SHALL be the sole place where a successful web authentication mints the cookie session and constructs the redirect to returnTo (or / when absent or rejected).

Per-method identity verification (WebAuthn ceremony, magic-token consumption, 6-digit-code consumption) SHALL run in its own function and produce a userId before completeAuth is invoked. completeAuth SHALL NOT know how identity was proved.

Terms recording happens at user creation time inside the per-method registration functions (finishRegistration for passkey, registerWithMagicLink for magic-link), not inside completeAuth. The Terms gate (root-loader redirect for cookie sessions; requireApiUser 403 for bearer-token API requests) SHALL remain the enforcement point for stale terms_version.

OAuth-code issuance at /oauth/authorize SHALL NOT be routed through completeAuth — that flow operates on an already-authenticated user and shares only the trailing redirect, not the full sequence.

Scenario: Passkey register-finish completes through the chokepoint

WHEN a visitor submits a successful WebAuthn step: "finish" registration response
THEN the route handler verifies the credential and creates the user row (with terms recorded) inside finishRegistration, then calls completeAuth({ userId, request, returnTo })
AND completeAuth mints the session cookie and returns a Response redirecting to returnTo (or /)

WHEN a visitor submits a successful WebAuthn step: "finish-passkey" login response
THEN the route handler verifies the credential and calls completeAuth({ userId, request, returnTo })
AND completeAuth mints the session cookie and returns a Response redirecting to returnTo (or /)

Scenario: Magic-link 6-digit-code verify completes through the chokepoint

WHEN a visitor submits a valid 6-digit code via step: "verify-code"
THEN the route handler consumes the magic token (marks used_at) and calls completeAuth({ userId, request, returnTo })

Scenario: Magic-link click-through verify completes through the chokepoint

WHEN a visitor opens /auth/verify?token=<token> with a valid, unused, unexpired token
THEN the route handler consumes the magic token and calls completeAuth({ userId, request, returnTo })

Scenario: returnTo is sanitized inside completeAuth

WHEN completeAuth is called with a returnTo value that is not a same-origin absolute path (e.g. starts with //, an absolute URL, or is malformed)
THEN the redirect target falls back to / rather than honoring the unsafe value
AND every caller benefits from the same check rather than reimplementing it

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