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Krzysztof kuhy Rudnicki
4c024a24f0
database.rules.json carries YOUR_FIREBASE_UID on purpose -- this repo is public and the uid is the one value that must not be in it. But nothing stopped anyone publishing the template as-is, and rules pinned to a uid that matches no account deny every read and write. The symptom is every device failing at once with a bare permission error, which reads like an outage rather than a bad paste. render_rules.sh substitutes the uid from ~/.config/crdt-sync/firebase.json and fails closed on anything unsafe: a surviving placeholder, missing `auth != null`, a missing uid pin (that one matters -- `auth != null` alone lets any stranger who self-registers through the public Web API key read everything), or output that is not JSON. Verified: its output is byte-identical to the deployed ~/.config/crdt-sync/database.rules.json, and the live database still answers an unauthenticated read with 401. All three failure paths exercised. Also corrects the README, which described the in-repo copy as "the deployed rules, with the real uid filled in" -- it never was. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01CFSGeWxHPY5rHUGrPqhcmG
88 lines
3.5 KiB
Markdown
88 lines
3.5 KiB
Markdown
# firebase/
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Deployable configuration for the Firebase project backing `crdt_sync` /
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`crdt_sync_dart` sync. Language-neutral, so it lives here rather than under
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either library.
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**This repository is public.** Nothing here names a concrete project, database
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URL, account or uid. Those live in a local, `0600` config file — see
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[Local configuration](#local-configuration).
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## Why Realtime Database, over REST
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* **No SDK.** Official FlutterFire has no Linux desktop support, and one
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caller (`wake_alarm`'s PC side) is a dependency-free systemd job. The REST
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endpoints are plain HTTPS and behave identically on Linux, Android and
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headless.
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* **No per-operation quota on the Spark (no-cost) plan.** RTDB bills only
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storage and bandwidth, so a misbehaving sync loop cannot exhaust a daily
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budget and silently stop working mid-day. Firestore's 20k-writes/day cap
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would be a second way to hit a wall, for querying this workload never does.
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* **Path model matches the existing layout** — `<prefix>/<deviceId>/<file>` —
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so no data remodelling.
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Deliberately **not** used: Cloud Storage (requires a linked billing account
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since 2026‑02‑03) and Cloud Functions. Avoiding both keeps the project
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structurally incapable of generating a bill.
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## `database.rules.json`
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Scopes the whole database to a single Firebase Auth uid.
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`auth != null` alone would **not** be safe: email/password sign-up is open
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through the identitytoolkit REST API to anyone holding the Web API key, and
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that key ships inside the Android APKs. Pinning the uid means a stranger who
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registers an account still reads and writes nothing.
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The uid here is a **placeholder on purpose** — this repo is public, and the
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uid is the one value that must not appear in it. Publishing this file
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verbatim yields rules matching no account, which locks every app out of the
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project until someone notices; the failure looks like a permission error
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from every device at once.
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So do not hand-substitute. Render it:
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```bash
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./render_rules.sh # prints deployable rules, real uid filled in
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./render_rules.sh --check # validates without printing the uid
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```
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It reads the uid from `~/.config/crdt-sync/firebase.json` and refuses to emit
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anything still containing the placeholder, missing `auth != null`, missing a
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uid pin, or not parsing as JSON. Paste its output into **Realtime Database →
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Rules → Publish**.
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Verify the rules are live — an unauthenticated request must be refused:
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```bash
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curl -s "$DATABASE_URL/.json"
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# {"error" : "Permission denied"} <- expected
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```
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## Local configuration
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Everything environment-specific lives in `~/.config/crdt-sync/`, mode `0600`,
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outside version control:
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| File | Contents |
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|---|---|
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| `firebase.json` | `apiKey`, `databaseUrl`, `projectId`, `uid`, `email` |
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| `password` | the sync account's password, no trailing newline |
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| `database.rules.json` | the rendered rules, real uid filled in (see `render_rules.sh`) |
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The Web API key is **not** a secret — it is a public project identifier that
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ships inside client apps. The password and refresh tokens are the real
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secrets.
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## Credentials at runtime
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No service-account key is used anywhere: it would bypass the security rules
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entirely and is trivially extractable from an installed APK. Devices sign in
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as the single user and hold a refresh token:
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* Android — `flutter_secure_storage`
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* Linux — `~/.config/<app>/firebase.json`, mode `0600`
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ID tokens last about an hour, so the refresh exchange is mandatory rather than
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optional — `diet_guard`'s PC timer alone runs 96 times a day.
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