rlsgrid

Catch cross-tenant Row-Level Security leaks in Postgres and Supabase before your users do.

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What it does

Point it at your database. rlsgrid reads the live schema and:

1. Maps every role × table × operation and labels it allow / deny / conditional / unrestricted.
2. Fuzzes for real cross-tenant leaks — it seeds synthetic tenants and actively tries to read, insert, update, and delete one tenant's rows from another tenant's session.
3. Emits a pgTAP suite you can run in CI.

Why

Postgres RLS is powerful and easy to get subtly wrong: a missing WITH CHECK, a FOR ALL where you meant FOR SELECT, a forgotten ENABLE ROW LEVEL SECURITY, a service_role bypass leaking client-side. Your application unit tests will not catch any of these — they test your code, not the policies. rlsgrid tests the policies, against a real database.

Use it

sudo apt install python3-venv -y
python3 -m venv ~/venvs/rlsgrid-env
source ~/venvs/rlsgrid-env/bin/activate
pip install rlsgrid
# if ipv6
export DATABASE_URL=postgresql://user:pw@host/db   # use staging, never prod
# if ipv4
getent ahosts db-host | grep STREAM | grep 4
export DATABASE_URL=postgresql://user:pw@<response>/db
rlsgrid init --from-db      # read the schema, write an annotated config
rlsgrid check --tenants 5   # seed → fuzz → teardown. exit 1 on any leak.

check is the whole loop: it leaves nothing behind and returns non-zero on a breach, so it drops straight into CI. A leak looks like:

✗ 1 cross-tenant breach detected
  LEAK role=authenticated actor_tenant=a1b2 → target_tenant=c3d4
       on public.documents UPDATE: target-owned row visible across tenants

In CI (GitHub Action)

- uses: matte97p/rlsgrid@v1
  with:
    command: check
    database-url: ${{ secrets.STAGING_DB_URL }}

Lower-level commands

rlsgrid introspect          # tables, RLS state, policies
rlsgrid plan --explain      # the full matrix, with a "why" column
rlsgrid gen pgtap --out tests/rls/generated.sql   # emit a pgTAP suite
rlsgrid fuzz --tenants 5    # fuzz only (auto-cleans up)
rlsgrid seed --dry-run      # show the seed plan without writing
rlsgrid check --sarif-out rls.sarif   # SARIF for GitHub code scanning

From pytest

Installing rlsgrid registers a rlsgrid fixture, so you can gate your existing suite:

def test_no_cross_tenant_leaks(rlsgrid):
    report = rlsgrid.check()
    assert report.ok, [b.detail for b in report.breaches]

Point it with --rlsgrid-config path/to/rlsgrid.toml.

Config for your stack — Supabase, Prisma, Drizzle, SQLAlchemy, Rails, function-based access checks — is in docs/RECIPES.md.

How it classifies a cell

• allow — a permissive policy applies and gates nothing.
• deny — RLS is on and no policy matches the role/op.
• conditional — a policy applies but a USING / WITH CHECK expression gates which rows. This is where the fuzz earns its keep.
• unrestricted — RLS is off, or the role has BYPASSRLS. Surfaced explicitly so you notice when you did not mean it.

Two enforcement models

• RLS at the database (the Supabase default): the fuzz finds leaks directly. Set tenancy.mode = "jwt".
• Access enforced by a SQL function (e.g. check_user_has_access_to_store(user_id, store_id)): set tenancy.mode = "function" and rlsgrid calls the helper with cross-tenant arguments, asserting it returns false.

How it compares

	hand-written pgTAP	static linters	rlsgrid
New table lands without a test	silent	maybe	shows up in plan
Cross-tenant write leaks	only if you wrote that test	no	probed automatically
Function-based access	no	no	first-class
Setup	per-test	low	one config

It composes with supabase-test-helpers: keep your bespoke business-rule pgTAP, let rlsgrid watch the floor.

Safety

seed, fuzz, and check write to the database, so they refuse any URL matching [safety].forbid_url_patterns (default ["prod", "production"]). Point DATABASE_URL at staging or a disposable database.

Status

Alpha, but exercised end to end in CI against a rich multi-tenant schema and run through pg_prove. The config shape may still shift before 1.0. Issues and PRs welcome — see CONTRIBUTING.

Built by Matteo Perino while shipping GeoSuite, a multi-tenant Supabase app.

License

MIT — see LICENSE.

Related tools

Part of my open-source toolkit — github.com/matte97p:

• pentest-framework — low-noise pentest orchestration, normalized to one schema and rendered to a PDF
• demowright — record polished product-demo videos from a script that lives in your repo
• GeoSuite CLIs — zero-dep Generative Engine Optimization toolkit

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⭐ If rlsgrid caught a leak (or proved you safe), give it a star — it helps other Supabase teams find it.