mrambossekandClaude Opus 5
43e1ba778a
- Comma-separated ECHOLOT_{CONTROL,UDP,TCP}_LISTEN; one listener/socket per
address. Explicit binds matter on multi-IP hosts (a wildcard would also
claim the SSH-only management address) and per-address UDP sockets are
the substrate stun-5780 needs.
- systemd unit reads /etc/echolot-server.env (seeded once, never
overwritten); --install-systemd with --self-update-api also installs a
daily randomized update timer that try-restarts the service.
- selfupdate: SHA256SUMS verification is now mandatory before the atomic
replace (integrity, not authenticity — signing still TODO).
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
121 lines
5.4 KiB
Markdown
121 lines
5.4 KiB
Markdown
# echolot-server
|
|
|
|
The probe server ([spec](../docs/probe-protocol.md)). Pure Go, stdlib only, GPL-3.0-or-later.
|
|
|
|
**Skeleton status:** control plane (enroll / profile / sessions with the spec's HKDF key
|
|
schedule), UDP data plane (ECHO with observation block, TIMESYNC, HMAC gate, anti-replay,
|
|
anti-amplification — wire format covered by tests). Not yet: TCP/TLS echo, STUN, canary DNS,
|
|
actions, observations API, admin UI beyond token minting.
|
|
|
|
## Deployment requirements
|
|
|
|
**No reverse proxy, no 80/443 — by design.** Traefik/nginx on the same host are fine; this
|
|
server never touches their ports, and putting it *behind* them would break two protocol
|
|
properties:
|
|
|
|
- Clients trust the control plane **only** via the SPKI pin from enrollment (self-signed is
|
|
first-class). A proxy terminates TLS with its own rotating ACME cert → pins break. The pin
|
|
model exists so no real certificate is ever needed.
|
|
- On the data plane, **the observed source address/port/TTL/DSCP *is* the measurement**. Any
|
|
proxy or NAT layer (including Docker's) substitutes its own — hence host networking.
|
|
|
|
What a target host actually needs:
|
|
|
|
| Port | Proto | Purpose | Notes |
|
|
|---|---|---|---|
|
|
| 8443 | tcp | control plane (pinned HTTPS) | any port — it travels in the enrollment QR + profile |
|
|
| 8442 | udp | UDP probe data plane | any port, profile-driven |
|
|
| 8441 | tcp | TCP/TLS echo | any port (not yet implemented) |
|
|
| 3478 | udp | STUN | keep standard: vanilla RFC 5389 for tool interop; rarely contended |
|
|
| 8444 | tcp | admin | loopback-only by design — reach via SSH tunnel |
|
|
|
|
All configurable via `ECHOLOT_*_LISTEN`. Plus:
|
|
|
|
1. **A public IP on the host** (v4, ideally also v6 — v6 topology issues are half of what
|
|
clients want to measure). Behind NAT, plain port-forwards work.
|
|
2. **Second IP (optional):** full RFC 5780 NAT-behavior discovery (`stun-5780`) needs an
|
|
alternate reply address; without it the profile advertises `stun-basic` and clients degrade
|
|
gracefully.
|
|
3. **Delegated DNS subzone (optional, later):** the `canary-dns` capability needs port 53 on
|
|
some IP + an NS delegation (mind systemd-resolved on 127.0.0.53). Absent → capability simply
|
|
not advertised.
|
|
4. **Outbound freedom** for connect-back / delayed-echo actions — no extra inbound ports;
|
|
generated traffic goes only to the session's observed source.
|
|
|
|
Deliberately out of scope here: an echo listener on 443 (to detect port-based egress filtering)
|
|
— that genuinely needs 443 and belongs on a dedicated IP, not on a host running a reverse proxy.
|
|
|
|
## Run in Docker (config via env)
|
|
|
|
```sh
|
|
docker compose up -d # see compose.yaml — network_mode: host is required
|
|
```
|
|
|
|
Host networking is not negotiable: behind Docker NAT the server would observe the proxy's
|
|
source addresses and TTLs instead of the client's — falsifying exactly what it measures.
|
|
Container mode is autodetected (`/.dockerenv` etc.); `--docker` / `ECHOLOT_DOCKER=1` forces it.
|
|
In this mode systemd install and self-update are refused — update by pulling a new image tag.
|
|
|
|
## Run native (systemd)
|
|
|
|
```sh
|
|
go build -o /usr/local/bin/echolot-server ./cmd/echolot-server
|
|
sudo /usr/local/bin/echolot-server --install-systemd # writes unit, enables, starts
|
|
sudo /usr/local/bin/echolot-server --uninstall-systemd
|
|
```
|
|
|
|
Config precedence: flags > `ECHOLOT_*` env > defaults. Every flag has an env twin
|
|
(`--udp-listen` ↔ `ECHOLOT_UDP_LISTEN`). Host config lives in `/etc/echolot-server.env`
|
|
(seeded by `--install-systemd`, never overwritten).
|
|
|
|
**Multi-IP hosts:** listen specs are comma-separated, and you should bind explicit addresses —
|
|
a wildcard bind would also claim management-only IPs:
|
|
|
|
```sh
|
|
ECHOLOT_CONTROL_LISTEN=203.0.113.10:8443,[2001:db8::10]:8443
|
|
ECHOLOT_UDP_LISTEN=203.0.113.10:8442,203.0.113.11:8442,[2001:db8::10]:8442,[2001:db8::11]:8442
|
|
```
|
|
|
|
Passing `--self-update-api` to `--install-systemd` additionally installs a daily randomized
|
|
self-update timer (`echolot-server-update.timer`) that restarts the service after a successful
|
|
update. Updates are checksum-verified against the release's `SHA256SUMS` (integrity, not
|
|
authenticity — signature verification remains TODO before treating the update source as
|
|
untrusted).
|
|
|
|
### Self-update (opt-in, native only)
|
|
|
|
```sh
|
|
echolot-server --self-update \
|
|
--self-update-api https://git.example.net/api/v1/repos/owner/repo
|
|
```
|
|
|
|
Fetches the newest `server-v*` release asset for this OS/arch and atomically replaces the
|
|
binary; systemd's `Restart=` brings up the new version. Run it from a systemd timer for
|
|
unattended updates. TODO before enabling anywhere untrusted: signature verification of the
|
|
downloaded asset.
|
|
|
|
## First contact
|
|
|
|
```sh
|
|
# 1. mint an enrollment token (admin listener is loopback-only)
|
|
curl -s -X POST 'http://127.0.0.1:8444/admin/enroll-tokens?note=phone'
|
|
# 2. device enrolls with it (normally via the echolot:// QR code)
|
|
curl -sk -X POST https://<host>:8443/v1/enroll -H 'Authorization: Bearer <token>'
|
|
# 3. device fetches its profile
|
|
curl -sk https://<host>:8443/v1/profile -H 'Authorization: Bearer <credential>'
|
|
```
|
|
|
|
The SPKI pin clients must verify is logged at startup (`pin-sha256`).
|
|
|
|
## Development
|
|
|
|
```sh
|
|
go test ./... # includes wire-format tests for the UDP data plane
|
|
go vet ./...
|
|
```
|
|
|
|
CI (`.gitea/workflows/build-server.yml`): tests on every push touching `server/`;
|
|
tagging `server-v1.2.3` builds + pushes the container image to the Gitea registry and
|
|
attaches static linux amd64/arm64 binaries (+ SHA256SUMS) to a release — the same
|
|
artifacts `--self-update` consumes.
|