---
kind: task
slug: rate-limit-and-abuse-guardrails
title: Rate-limit credentials sign-in and high-impact mutations
plan_slug: multitenant-saas-hardening
epic_slug: tenant-lifecycle
status: ready
priority: P2
tenant_id: global
owner: unassigned
cursor_todo_id: null
updated_at: "2026-06-01"
---

# Task summary

Add per-IP rate limits to credentials sign-in and to a small set of high-impact mutation endpoints (invite, archive, create-workspace). The goal is to cap brute-force and obvious abuse, not to be a full WAF.

## Description

### Storage

Use the existing Redis instance on CT 102 (already used by Hocuspocus for awareness). Add a thin client in `packages/shared/src/rate-limit/` — token-bucket or sliding-window, your choice; the contract is `consume(key: string, opts: { capacity, refillPerSecond }): Promise<{ ok: boolean, remaining: number, retryAfterMs: number }>`.

If you don't want a new shared lib, `@upstash/ratelimit` is a fine drop-in even though we're not on Upstash — it works against any Redis URL. Don't add a new database for this.

### Where to apply

1. **Credentials sign-in** (`apps/web/app/api/auth/[...nextauth]/route.ts`, or the `authorize` callback): key by IP (`x-forwarded-for`, falling back to remote addr). 5 attempts / 60 seconds, then 429.
2. **Invite create**: key by `actor_user_id`. 30 invites / hour. Workspace-scoped is fine too.
3. **Workspace create**: key by `actor_user_id`. 5 workspaces / hour.
4. **Archive/restore**: key by `(workspace_id, actor_user_id)`. 20 / hour. Cheap insurance against a script flipping state in a loop.

### IP extraction

Use the same helper everywhere; don't recompute in every route. Common gotcha: `x-forwarded-for` is a comma-separated list when there are multiple proxies. Take the first entry. If the deployed stack is behind Cloudflare, `cf-connecting-ip` is more reliable — add that as a higher-priority source if present.

### Response

When a limit trips, return `429 Too Many Requests` with a `Retry-After` header in seconds and a tRPC `TOO_MANY_REQUESTS` error code. The client should surface a friendly message ("try again in ~30 seconds"), not a stack trace.

### Audit logging

Every limit trip writes an `audit_log` row (`action: "rate_limit.tripped"`, `metadata: { route, key_kind, retry_after_ms }`). This is how you discover whether anyone's hitting the limits in practice; without it the limits are silent.

### Anti-goals

- Don't add a CAPTCHA. If brute-forcing becomes a real problem, add Cloudflare in front of the deploy.
- Don't write a generic rate-limit middleware that wraps every tRPC procedure. The set of high-value endpoints is short; explicit is better than universal.

## Subtasks

- [ ] Pick the Redis client and rate-limit lib (or hand-roll).
- [ ] Add IP extraction helper.
- [ ] Apply limits to the 4 routes above.
- [ ] Wire `audit_log` writes on limit trips.
- [ ] Verify by scripting 20 credentials sign-in attempts against a dev deploy.

## Owner or assignee

Unassigned

## Status

ready

## Estimation

M

## Acceptance criteria

- [ ] Brute-forcing credentials sign-in trips at attempt 6 within 60 seconds.
- [ ] Invite-spam attempt trips at invite 31 within an hour.
- [ ] Every trip produces an `audit_log` row.
- [ ] No global tRPC middleware — limits are applied per route.

## Links to related Epic / Plan

- Epic: `./Epic-tenant-lifecycle.md`
- Plan: `../Plan-multitenant-saas-hardening.md`