nilsandClaude Opus 5.5
acb7e1969e
The update relay logs every check (car, number of releases, newest pre-release) and every download (car, file, size, then bytes and time, or that it was cut short); never the forge's address or token, tested. Go 1.27.3 for the build image and toolchain: govulncheck had found GO-2026-6809 in crypto/x509 under 1.26.9; source and binary now clean. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01LhzAVaUyqcw5PkGjz4mWW6
129 lines
6.5 KiB
Markdown
129 lines
6.5 KiB
Markdown
# Nils' MG4 — car server
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A small Go service at car.k8s.stinnesbeck.com: the API the car writes to. Data lives in
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InfluxDB 2; Grafana reads it from there for the dashboards (`../k8s/grafana/`). The car sends
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its live data to ABRP itself; the server does not talk to ABRP (removed in 2.4.0).
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```
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car ──live telemetry───▶ server
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──daily chunks─────▶ │
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──charging sessions▶ ▼
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InfluxDB 2 ◀── Grafana
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```
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## Configuration
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Environment only; the server refuses to start when a required value is missing.
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| Name | Notes |
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|---|---|
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| `INFLUX_URL`, `INFLUX_TOKEN`, `INFLUX_ORG` | required; the token needs read/write on the bucket |
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| `INFLUX_BUCKET` | default `mg4` |
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| `INGEST_TOKEN` | required, at least 24 characters: `openssl rand -hex 32` |
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| `APPROVAL_PASSWORD` | optional, at least 12 characters; switches pairing on (see below) |
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| `PUBLIC_URL` | the address a phone uses, for the pairing QR code; derived from the request if empty |
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| `FORGE_URL`, `FORGE_REPO`, `FORGE_TOKEN` | optional; app updates (below). The token only needs to read the repository |
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| `LISTEN_ADDR` | default `:8080` |
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## Endpoints
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The ingest endpoints accept `Authorization: Bearer <token>` with either the shared `INGEST_TOKEN`
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or a paired car's own token. A paired token only works for the installation id it was paired
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with (403 otherwise); the shared token works for any.
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- `POST /v1/telemetry` — `{ installationId, samples: [...] }`, up to 500 samples in ABRP's `tlm`
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field names and units (`utc` in epoch seconds; flags as 0/1 or booleans). Unknown fields are
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dropped, known ones bounded: a value out of range is dropped on its own, and a sample without
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a plausible time (before 2001, or more than an hour ahead) is dropped whole. The rest is stored
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and the answer is `200 {stored, droppedCount, dropped}`, even when nothing was usable, since
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the car would only send it again.
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- `PUT /v1/consumption/daily` — one delta chunk of a day's consumption.
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- `PUT /v1/charging-sessions/{sessionId}` — a finished charging session (AC or DC, as far as the car was awake) with its curve.
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- `GET /v1/consumption/history/{installationId}` — the car reads its own totals back.
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- `GET /v1/health` — `{"status":"ok"}`.
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A malformed request is a 400 naming the field; a database failure is a 500 without detail.
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## App updates
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`GET /v1/app/releases` and `GET /v1/app/assets/{release}/{asset}/{name}`, with the car's token:
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the repository's releases, read from the forge with `FORGE_TOKEN`, in GitHub's field names
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with download URLs pointing back at this server, and their attachments streamed through. The
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repository stays private and the forge token never reaches the car; redirects away from the
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forge are not followed. The car verifies everything itself (`OTA.md`). 404 when unset.
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Each check and each download is logged with the car's installation ID ("shared token" for the
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shared ingest token): `update check` (how many releases, the newest pre-release), `update
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download started` (file, size), then `update handed out` (bytes sent, time taken) or `update
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download cut short`. The forge's address and token never appear in the log.
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## Settings from a phone
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The ABRP credentials are long to type on the car. With pairing on, the car (with its own token)
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opens `POST /v1/settings/start` `{installationId}` and shows `verificationUriComplete` as a QR
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code. The phone fills in the form at `/settings?code=…` (ABRP API key and user token, charging
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price, usable capacity; empty fields are left alone) and sends it with the approval password.
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The car polls `POST /v1/settings/poll` `{deviceCode}`: 202 pending, 200 with the values (handed
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out once, `Cache-Control: no-store`), 410 expired or unknown. A paired token only reaches its own
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installation's request. The values live in memory only, at most ten minutes, and are never
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stored, logged or put back into the page.
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## Pairing a car by QR code
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So nobody types a token in the car. Modelled on the OAuth device authorization grant (RFC 8628);
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on only when `APPROVAL_PASSWORD` is set.
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1. The car calls `POST /v1/pair/start` `{installationId}` and shows the returned
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`verificationUriComplete` as a QR code, plus the short `userCode` (e.g. `K7F-3QX`).
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2. The phone opens `/pair?code=…`, the owner checks the code and approves with the approval
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password. Five wrong passwords from one address lock that address out for a minute; other
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addresses are unaffected (the address is the last `X-Forwarded-For` entry, which Traefik sets).
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An address may hold three open requests; a car starting again replaces its own.
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3. The car polls `POST /v1/pair/poll` `{deviceCode}`: 202 pending, 200 with its own token
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(handed out once), 403 denied, 410 expired (after 10 minutes) or unknown.
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Each car gets its own 43-character token; only its SHA-256 is stored (measurement `device` in
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the same bucket), and the token is only handed out, and only accepted, once the device is
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persisted, so a restart never loses a paired car. Manage cars with the approval password:
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```sh
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curl -H "Authorization: Bearer $APPROVAL_PASSWORD" https://car.k8s.stinnesbeck.com/v1/devices
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curl -X POST -H "Authorization: Bearer $APPROVAL_PASSWORD" https://car.k8s.stinnesbeck.com/v1/devices/<id>/revoke
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```
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## Storage
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One bucket, `installationId` tag on every point:
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| Measurement | Timestamp | Tags | Fields |
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|---|---|---|---|
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| `telemetry` | sample `utc` | — | the ABRP fields that were sent |
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| `consumption_chunk` | `recordedAt` | `date` | km, kwh, hours, socDrop, sohPercent |
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| `charging_session` | `startedAt` | `sessionId` | endedAtMs, duration, energy, cost, start/end SOC |
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| `charging_curve` | point time | `sessionId` | powerKw, socPercent |
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| `device` | paired at | `deviceId` | tokenHash, installationId, revoked |
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A point with the same measurement, tags and timestamp replaces the earlier one, so the car's
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retries are idempotent: a cached chunk is re-sent with its original `recordedAt`. Days and the
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lifetime total are summed from the chunks when read. Numbers are always written as floats,
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because InfluxDB fixes a field's type on first write.
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## Development
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```sh
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nix develop # from the repository root: Go, govulncheck, InfluxDB 2
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cd server
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go test ./...
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govulncheck ./...
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```
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## Container image
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```sh
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podman build -t git.stinnesbeck.com/nils/mg4-server:<version> .
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podman push git.stinnesbeck.com/nils/mg4-server:<version>
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```
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The build runs `go vet` and the tests. The image is a static binary on distroless (about
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11 MB), running as UID 65532 on port 8080.
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