TLS made usable — named, renewed, and every key served

TLS, made usable rather than merely present.

The login page, behind a certificate a browser will accept.

Firmware v2.23.0, 11 September 2026. Every item below is the repository's own changelog entry, taken apart; the whole entry is a click away under each one.

New

/metrics says when the serving certificate expires

— bmcd_tls_certificate_expiry_timestamp_seconds — and which key it is built on, bmcd_tls_certificate_info{key="ecdsa-p384"}.

The whole entry

A number a scrape can alert on is the difference between noticing an expiry and a calendar reminder somebody stops reading. A date the daemon cannot parse reports no series at all rather than a zero, which would read as 1970 and fire every rule written against it.

Confirmed

Every key an operator might install is served

Over TLS 1.3 and 1.2 alike: RSA, EC P-256, P-384 and P-521, and Ed25519. Already true, now a test that performs a real handshake per key type against the real acceptor.

Changed

• bmcd v2.30.0 → v2.32.0: the daemon offers TLS 1.3, with 1.2 as the fallback. (SQU-136). Its acceptor was built from Mozilla's version 4 intermediate profile, which pins the maximum protocol version to TLS 1.2. The board's OpenSSL is 3.5.7 and was capable of 1.3 the whole time.

  The whole entry

  Not housekeeping. Under TLS 1.2 a client's supported_groups extension constrains the curve of the server's certificate as well as the key exchange, so a client whose list stops at P-256 — Envoy's default — cannot use a P-384 certificate at all. Every certificate in the estate these boards run in is P-384, so the gateway in front of them failed every handshake and both boards showed as unreachable behind a login page that worked perfectly.

• The self-signed certificate is one a client can actually trust, and it renews itself. The script that issues it, when nobody has installed a real certificate, had four problems, each now fixed:

  The whole entry

  • It set no subjectAltName. Every browser since 2017 matches on the SAN and ignores the common name, so that certificate could not be accepted by any of them. A self-signed certificate nobody can choose to trust is decoration. It now names the board's hostname, its .local name and every global address it holds.
  • It was valid for 30 days — openssl's default, never passed — and only ever regenerated when a file was missing. A board left running served an expired certificate for as long as it stayed up; one here did for over a year (SQU-115). It now issues for 825 days and reissues 30 days before expiry, so neither a long uptime nor a month powered off produces an expired certificate.
  • It generated RSA 4096 on a board with about 87 MB of usable RAM. Now EC P-384, the estate's standing key type: stronger per bit, faster, smaller.
  • Its pair check ran openssl rsa -noout -modulus, which fails on any key that is not RSA — and the failure branch deletes both files and regenerates. An operator installing an EC or Ed25519 certificate could have it destroyed at the next boot. It now compares public keys, which works for every key type, and refuses to touch any certificate it did not issue: a certificate from a real CA is left exactly where it is, expired or not, with a warning rather than a replacement.

  Fifteen assertions cover this in CI, including the two that matter most: a certificate this script did not issue comes out byte for byte unchanged.

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