fix(reseed): unique machine-id per clone + entropy hygiene#8
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systemd-machine-id-setup derives the machine-id from the SMBIOS product_uuid in a VM, which a snapshot clone inherits verbatim — so every clone regenerated the SAME id, silently defeating the reseed verb's whole purpose (cocoon assigns no per-clone SMBIOS UUID). Always write a fresh random id instead and drop the DMI-derived path. Writing the new id first also removes the empty-machine-id window a failing drop-dbus step used to leave. Zero the single-use host entropy after the mix, and note the agent's 512-byte cap on the client.
A surviving /var/lib/dbus/machine-id keeps serving the old id to dbus consumers after a clone; a drop failure is a real uniqueness gap, so surface it at Warn instead of Debug.
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Problem
The reseed verb exists so byte-identical snapshot clones don't share CRNG state — but the machine-id half was self-defeating.
systemd-machine-id-setupin a VM derives the id from the SMBIOSproduct_uuid, which a snapshot clone inherits verbatim, and cocoon assigns no per-clone SMBIOS UUID. So every clone regenerated the same machine-id. The random path only fired when the tool failed, not when it succeeded with a shared DMI id.Fix
systemd-machine-id-setuppath entirely.randomMachineIDextracted as a pure, tested function (uniqueness is the whole point)./etc/machine-idwindow a failing drop step used to leave (found by review).req.Data+ the ioctl buffer) after the mix.client.Reseed.Verification
GOWORK=off build/test/
-race(agent+client) green; lint 0 issues on linux/darwin/windows; fmt-check clean. NewTestRandomMachineIDasserts canonical format + uniqueness.Reviewed by an adversarial Opus pass (two should-fix + two nits, all addressed). No backward-compat kept per owner direction.