julien
da2bd6d481
## Summary Documents the security middleware stack shipped across the five most recent BFF PRs (#115, #117, #120, #122, #123) as a single MADR ADR. Today the rationale for each choice lives in code comments and PR descriptions; the next contributor reaching for `csurf`, a cookie-only CSRF, or a hardcoded localhost CORS fallback won't have a single place to read why those are wrong here. ADR-0021 covers: - **Response envelope** — `{ error: { code, message, traceId } }`, single contract shared between Nest's `StructuredErrorFilter` and raw Express middlewares (CSRF, rate-limit) via the exported `errorResponse()` helper. Status code → code mapping documented. 500s never leak the underlying exception. - **CSRF — session-bound double-submit**, not pure cookie-vs-header. Rationale: a subdomain-takeover cookie injection can't bypass the comparison because the source of truth is the server-side session token, not the cookie. Cookie is the SPA's read-only mirror. - **CORS allowlist** — `CORS_ALLOWED_ORIGINS` mandatory at boot, no fallback. "Works in dev, breaks in prod" is the exact trap the validator catches. - **Rate limiting** — buckets keyed by session id (auth) or IP (anonymous), 10/min on `/auth/login` + `/auth/callback`, 120/min general, `/api/health` skipped. In-memory v1 store; Redis-backed migration is one constructor arg. - **Helmet config** — defaults plus three overrides (HSTS prod-only, `crossOriginResourcePolicy: cross-origin`, CSP prod-only). Each override has a code-anchored justification. ## Scope This is the **implementation-level** security ADR. The **strategic** security baseline ADR — OWASP ASVS reference level, HDS / GDPR / NIS 2 framing, RSSI sign-off — remains paused per the note in [CLAUDE.md](CLAUDE.md). When that ADR lands it'll either confirm 0021 or supersede pieces of it; 0021 is explicit about which choices are tactical and revisitable. ## Notable structural choices in the ADR - **"Considered Options" mirrors the actual debate.** For CSRF: session-bound vs pure double-submit vs `csurf` vs synchronizer. For rate-limit bucket key: sessionID-then-IP vs IP-only vs Entra `oid`. Each rejected option has its "Bad, because …" so the reader sees why we didn't go that way. - **Each "Decision Outcome" line points at the file / function that enforces it.** Cross-references are absolute paths so they survive folder reorgs. - **The "Consequences" section is brutally honest about trade-offs.** In-memory rate-limit doesn't scale horizontally. The CSRF cookie is XSS-readable. No `details` field in the envelope for field-level validation errors yet. These aren't hidden in the prose. ## Other doc touches - [docs/decisions/README.md](docs/decisions/README.md) index entry added. - [notes/handoff.md](notes/handoff.md) refreshed (gitignored; not part of the commit but useful for the next session). ## Noted for a separate PR (out of scope here) [CLAUDE.md](CLAUDE.md) §"Repository status" still says "The Nx workspace is **not yet bootstrapped**" and refs ADRs up to 0020. The whole paragraph is stale (the project is fully scaffolded, 22 ADRs in place). Worth a small dedicated docs PR. ## Test plan - [x] `pnpm exec prettier --check docs/decisions/` → clean. - [x] ADR follows the MADR 4.0.0 template (frontmatter with `status`, `date`, `decision-makers`, `tags`; sections in the canonical order). - [x] Tags drawn from the vocabulary in [docs/decisions/README.md](docs/decisions/README.md#tag-vocabulary): `security`, `backend`. - [x] Index in `docs/decisions/README.md` updated in the same change. - [x] Cross-references to ADRs 0009, 0010, 0012, 0015 verified. - [ ] Renders in Gitea / IDE markdown preview without parser warnings. --------- Co-authored-by: Julien Gautier <julien.gautier@apf.asso.fr> Reviewed-on: #124
Architectural Decision Records
This project records architecturally-significant decisions as ADRs in the MADR 4.0.0 format. References: adr.github.io.
Why ADRs
ADRs capture the why behind a decision — context, drivers, options considered, trade-offs accepted — at the moment the decision is made. They make architecture reviewable, onboarding faster, and prevent the same debate from being re-litigated later.
Conventions
- Format: MADR 4.0.0. Start from template.md.
- Filename:
NNNN-kebab-case-title.md, e.g.0007-adopt-tailwind-for-design-tokens.md. - Numbering: globally sequential 4-digit prefix. Numbers never reset, never get reused — even when an ADR is superseded or deprecated.
- Layout: flat folder. ADRs are not nested into category subfolders; topical organization happens via tags.
- Tags: every ADR carries a
tags:array in the MADR frontmatter, drawn from the tag vocabulary below. An ADR may carry several tags. Propose new tags (or renames) in the same PR that needs them; never invent ad-hoc tags inline. - Status lifecycle:
proposed→accepted→ optionallydeprecatedorsuperseded by [ADR-NNNN](NNNN-other.md). Update the YAML frontmatter; never delete an ADR. - Index maintenance: every ADR addition or status change must update the Index below in the same commit.
When to write an ADR
Write one whenever a development decision is non-trivial: tool or library choice, framework pattern, security control, perf budget, a11y target, naming convention, deprecation, breaking change, or any choice that future contributors would benefit from understanding the why of.
Tag vocabulary
The vocabulary below is the source of truth. It is intentionally coarse — propose extensions only when an existing tag genuinely doesn't fit, and avoid overly narrow tags.
| Tag | Scope |
|---|---|
frontend |
UI, Angular, components, design system, client-side state |
backend |
API, BFF, server-side services |
security |
AuthN, AuthZ, sessions, CSP, dependency scanning, secret management |
performance |
Perf budgets, caching, bundle size, Lighthouse |
accessibility |
WCAG, a11y testing, keyboard, ARIA, contrast |
infrastructure |
CI/CD, hosting, deployment, runtime |
observability |
Logs, metrics, traces, correlation IDs, monitoring |
data |
Persistence, schemas, migrations, data flow |
process |
Team conventions, workflows, repo policy |
Status: starter vocabulary, to be refined as ADRs accumulate. Update this table whenever a tag is added, renamed, or retired.
Index
ADRs are listed in numerical order. To slice by topic, filter on the Tags column.
| # | Title | Status | Tags | Date |
|---|---|---|---|---|
| 0001 | Use ADRs to record architectural decisions | accepted | process |
2026-04-29 |
| 0002 | Adopt Nx monorepo with the apps preset |
accepted | infrastructure, frontend, backend |
2026-04-29 |
| 0003 | Workspace and app naming convention | accepted | process |
2026-04-29 |
| 0004 | Frontend stack — Angular (latest LTS), standalone, zoneless, Signals, CSR-only, Vitest | accepted | frontend |
2026-04-29 |
| 0005 | Backend stack — NestJS over Express, Fastify, Hono | accepted | backend |
2026-04-29 |
| 0006 | Persistence — PostgreSQL with Prisma | accepted | data, backend |
2026-04-29 |
| 0007 | Pre-commit hooks and Conventional Commits | accepted | process |
2026-04-29 |
| 0008 | Identity model — multi-tenant Entra ID for workforce, dual-audience design for future External ID | accepted | security, data |
2026-04-29 |
| 0009 | Authentication flow — OIDC Authorization Code + PKCE via MSAL Node, BFF session pattern | accepted | security, backend |
2026-04-29 |
| 0010 | Session management — opaque session IDs in cookies, payload in self-hosted Redis with AES-GCM at rest | accepted | security, backend, infrastructure |
2026-04-29 |
| 0011 | MFA enforcement — Entra ID Conditional Access baseline, BFF claim sanity-check, step-up hooks designed-in | accepted | security |
2026-04-29 |
| 0012 | Observability — Pino structured logs + OpenTelemetry tracing, W3C Trace Context propagation, stdout + collector | accepted | observability, backend, frontend |
2026-04-29 |
| 0013 | Audit trail — separated append-only Postgres schema, decoupled from app logs | accepted | security, observability, data |
2026-04-29 |
| 0014 | Downstream API access — On-Behalf-Of pattern, unified DownstreamApiClient, audience-aware authorization |
accepted | security, backend |
2026-04-29 |
| 0015 | CI/CD pipeline — Gitea Actions, trunk-based + squash-merge, thin YAML over portable scripts | accepted | infrastructure, process |
2026-04-30 |
| 0016 | Accessibility baseline — WCAG 2.2 AA + targeted AAA, Angular CDK + spartan-ng + Tailwind, APF panel testing | accepted | accessibility, frontend, process |
2026-04-30 |
| 0017 | Performance budgets — Core Web Vitals + Lighthouse CI gates, bundle budgets, BFF p95/p99 SLOs | accepted | performance, frontend, backend, process |
2026-04-30 |
| 0018 | Environment configuration — Angular environment.ts, BFF env vars, audit pool split |
accepted | frontend, backend, infrastructure, process |
2026-05-10 |
| 0019 | Internationalisation — @angular/localize, build-time per-locale bundles, /fr + /en path-based routing |
accepted | frontend, accessibility, performance, process |
2026-05-11 |
| 0020 | portal-admin — dedicated SPA for portal administration, sharing the existing BFF |
accepted | frontend, backend, security, infrastructure, process |
2026-05-11 |
| 0021 | Phase-2 security baseline — helmet, CORS allowlist, double-submit CSRF, rate limiting, structured error envelope | accepted | security, backend |
2026-05-13 |