jschoubben
a6872ac099
Issue 014: the node's serving key was stored in the host's own encoding, so every check that reads the file passed and no server could start. Same shape as 013 — two halves of one mechanism designed separately, each correct about its own half. Where a file exists so a third party can read it, the format is the interface.
49 lines
2.4 KiB
Markdown
49 lines
2.4 KiB
Markdown
---
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status: resolved
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opened: 2026-08-31
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located-in: [mesh-host]
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fixed-by: mesh-host — a node's serving key is stored in the format a server reads
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amended-design:
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---
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# 014 — A node's serving key was present, correct, and unusable
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## Symptom
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A node generates the key it serves TLS with, the mesh certifies the public half, and the
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certificate arrives on the machine as an ordinary file. Everything about that worked. But the host
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stored the private half in its own encoding — base64 of the raw key — and **nothing that serves
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TLS can read it**: not a web server's `ssl_certificate_key`, not Go's `LoadX509KeyPair`, not
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`openssl s_server -key`.
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The file was there, owned by root, mode 0600, holding the right key. The certificate beside it was
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valid and chained to the mesh's authority. The server would not start.
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## Why this matters
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**Every check that reads the file passes.** The key exists, the certificate exists, the mesh
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recorded the public half, the machine reports the declaration applied. The failure surfaces only
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when something connects — the worst place to find out, and the place the certificate work was
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specifically designed to move away from.
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It is the same shape as [013](../013-a-file-arrives-after-the-service-that-needs-it/00-report.md)
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and worth naming as a class: **two halves of one mechanism designed separately, each correct
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about its own half.** The control plane issues PEM because that is what a certificate is. The host
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stored the key in whatever was convenient, because nothing in the host reads it back — the whole
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point of the file is that *something else* does, and that something else was not in view.
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**The generalisation:** where a file exists so a third party can read it, the format is not an
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implementation detail of whoever writes it. It is the interface, and it needs a check that reads
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it the way that third party will.
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## What was done
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PKCS#8 PEM, which is what every TLS server reads. A key in the old encoding is refused **by name**
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rather than reported as corrupt — it is intact, and the remedy is to enrol again, which is a
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different action from repairing a damaged file.
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*Checked by writing a key, decoding the file as PEM, parsing it as PKCS#8, and asserting it is the
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same key — and, in the lab, by a real handshake from a second machine that verifies against the
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mesh's authority and nothing else. A key that parses is not a key a server can use, which is why
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the lab check connects.*
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