KeiSeiKit-1.0/skills/auth-setup/SKILL.md

name	description	argument-hint
auth-setup	Hub-and-spoke pipeline that produces a production-grade auth/IAM plan for a new or existing app — user flows, identity providers, session strategy, authorization model, and threat mitigations — via pure-click decisions across five phases. Emits a scaffolded env-var list, library picks, and a per-threat checklist; never writes secrets.	<one-line app description, e.g. "B2C SaaS, Next.js + Postgres, needs Google + passkeys">

Auth-Setup — Identity, Session & Authorization Pipeline (index)

When to use

• Setting up user authentication for a new or existing app (social login, passkeys, magic link).
• Choosing and configuring an identity provider, session strategy, or authorization model.
• Auditing an app's auth/IAM posture and generating a threat mitigation checklist.

See _blocks/pipeline-5phase-template.md for the 5-phase wizard contract and _blocks/rule-pure-click-contract.md for the AskUserQuestion rule. Skill-specific phase tables are inline below.

You are converting "I need auth for app X" into a concrete, reviewable plan: which identity methods to ship, which providers to register, which session strategy to pick, which authorization model to enforce, and which threats to mitigate up front. Every decision is a click; the only typed input is the one-line app description in Phase 1.

This skill does NOT write production code. It emits a plan, the env-var scaffold, the library picks, and a per-threat checklist. Code scaffolding is a separate task owned by new-agent or the project's own code-implementer.

The skill reads the four companion blocks heavily — every phase references at least one of them:

• _blocks/auth-oauth2-oidc.md — OAuth2 / OIDC flows, PKCE, providers.
• _blocks/auth-passkeys.md — WebAuthn registration + assertion, RP ID.
• _blocks/auth-sessions.md — server sessions vs JWT tradeoff, cookies.
• _blocks/auth-authorization.md — RBAC / ABAC / ReBAC, policy engines.

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Pipeline overview (5 phases, ≥6 AskUserQuestion calls)

Phase	File	Purpose	AskUserQuestion
1	phase-1-intake.md	App flows, stack, storage, MFA	4×
2	phase-2-identity-provider.md	Pick + configure IdPs; env scaffold	1×
3	phase-3-session-strategy.md	Server-session vs JWT; cookie flags	1×
4	phase-4-authorization.md	RBAC / ABAC / ReBAC; permission matrix	1×
5	phase-5-threats.md	CSRF / XSS / timing / enumeration	1×

Minimum AskUserQuestion count across a full session: 8 (4 in Phase 1 + 1 each in Phases 2–5). Exceeds the ≥6 hub-and-spoke contract.

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Variables the pipeline produces

Name	Set in	Meaning
FLOWS	Phase 1	subset of {email+password, magic-link, OAuth, passkey, SSO}
STACK	Phase 1	Next / Remix / SvelteKit / Astro / Rust axum / FastAPI / other
STORAGE	Phase 1	Postgres / SQLite / MySQL / Supabase / managed-auth
MFA	Phase 1	none / TOTP / passkey / WebAuthn-as-2FA
PROVIDERS	Phase 2	list of OAuth/OIDC providers with env-var names
SESSION	Phase 3	server-session OR JWT + cookie config
AUTHZ	Phase 4	RBAC / ABAC / ReBAC + policy engine (or none)
THREATS	Phase 5	mitigation checklist, per threat class

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Final report (emit after Phase 5)

=== AUTH-SETUP REPORT ===
App:        <first 80 chars of intake>...
Stack:      <STACK> + <STORAGE>
Flows:      <FLOWS list>  MFA: <MFA>
Providers:  <PROVIDERS with env var names>
Session:    <SESSION summary line>
Authz:      <AUTHZ model + engine if any>
Threats:    <N mitigations selected>
Libraries:  <pick per language, one line>
Env vars:   <count> new entries for secrets/<file>.env
Next:       run `compose-solution` or hand off to project code-implementer

---

Rules (apply throughout)

• Pure-click contract. Only the Phase 1 intake paragraph is typed. Every other decision is AskUserQuestion.
• RULE 0.8 Secrets SSoT. The skill emits env VARIABLE NAMES only (GOOGLE_CLIENT_ID, APPLE_TEAM_ID, ...). It NEVER echoes a token value, never writes to secrets/*.env, never suggests hard-coding. Storage path is <repo>/secrets/auth.env per domain-has-secrets.md.
• NO DOWNGRADE. If the chosen combination is unsafe (e.g. passkey-only without a recovery flow) the skill returns 2–3 constructive alternatives, never "not supported".
• Fail-closed default. Every authz / session / threat decision defaults to the safer option when the user is unsure.
• Surgical scope. Reads the four auth blocks; writes nothing outside its own phase files. Production scaffolding is delegated.

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References

• _blocks/auth-oauth2-oidc.md, _blocks/auth-passkeys.md, _blocks/auth-sessions.md, _blocks/auth-authorization.md.
• _blocks/domain-has-secrets.md — storage path + loading convention.
• _blocks/rule-pre-dev-gate.md — analogue check before inventing.
• Evidence grade [E2] — pipeline mirrors OWASP ASVS v4.0.3 chapters 2–4.