Running an unfamiliar binary by name should tell you what it does, not bind a
dozen ports and start answering the internet. --serve (or --daemon) now does
that, and a bare invocation prints usage and exits 2 - non-zero on purpose, so a
service manager sees a failure rather than concluding the server ran and
finished cleanly.
The hazard this creates is worth spelling out, because it bites once and
silently: three places started the binary with no arguments - the systemd unit,
the unit template, and the Dockerfile - and --self-update replaces the binary
but never the unit. A routine update would therefore leave a service that cannot
start, discovered whenever the host next rebooted.
So the updater repairs it: after replacing the binary it appends --serve to an
ExecStart that has no flags, but only in a unit this program wrote (identified
by its description). Editing an operator's hand-written unit would be overreach;
leaving ours broken would be negligence.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
If the IdP is misconfigured, unreachable, or the admin group is a typo, the
operator is locked out of their own server with no way back short of editing
JSON on disk. A fallback that only matters when everything else is broken is
exactly the thing you cannot add later - by then you cannot get in to add it.
Stored as PBKDF2-HMAC-SHA256 from the standard library (Go 1.24+ has it, so no
dependency), 600k iterations, per-credential salt. A password rather than a
bearer token on purpose: a break-glass credential is the one most likely to end
up in a backup or a config-management repo, and a hash survives that where a
token does not. There is no email reset flow and should not be -
--set-admin-password on the host is the reset, and whoever can run it already
has the machine.
The password is read from stdin, never a flag, so it stays out of shell history
and the process list; piping still works for automation.
Details the tests pin, each for a reason:
- the username is compared in constant time too, or a fast rejection is a
timing oracle for which usernames exist;
- the *stored* iteration count is used, so raising the constant later does not
lock out existing passwords;
- the throttle grows with consecutive failures but stays bounded and forgives
after a quiet minute - a break-glass credential an attacker can lock out is
a denial of service against the one person who needs it;
- sessions are MAC-checked before anything in them is read, and rotating the
secret invalidates every one at once, which is how they are revoked.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
- 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>
Pure stdlib. Implements the spec's core: enrollment (single-use tokens),
profile (SPKI pin, only real capabilities advertised), sessions with the
§2.4 HKDF-SHA256 key schedule; UDP data plane with the 32-byte ELT1
header, 4-byte HMAC gate, 1024-wide anti-replay window, ECHO_RESP with
observation block, TIMESYNC, and the §3.4 anti-amplification cap. Wire
format has tests (roundtrip + silent-drop cases); enroll→profile→session
smoke-tested live.
Modes: container (autodetect /.dockerenv|/run/.containerenv|cgroup, or
--docker/ECHOLOT_DOCKER=1; config via ECHOLOT_* env; distroless image;
network_mode host required — Docker NAT would falsify observed sources)
and native (--install-systemd/--uninstall-systemd with a hardened unit,
opt-in --self-update from Gitea releases; refused in containers).
CI: tests on any server/ push; server-v* tags build+push the image to the
Gitea registry and attach linux amd64/arm64 binaries + SHA256SUMS to a
release — the artifact self-update consumes.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
