41 lines
2 KiB
Markdown
41 lines
2 KiB
Markdown
# swarm-authelia-bridge
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The only thing allowed to write `swarm-authelia`'s users database.
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## Why this exists
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`swarm-controller`'s `CreateIdentity` job needs to add an agent as an
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authelia subject, but `swarm-controller` runs unprivileged and does not own
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`users.yml` — a different uid does (`authelia-swarm`, the user
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`services.authelia.instances.swarm` runs as). Root/`CAP_CHOWN`/a shared
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group were all examined and rejected during this crate's design thread —
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see `swarmctl/README.md`'s identical analysis of this same file, written
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before this crate existed.
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The fix: run **this** process as `User = "authelia-swarm";` instead —
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inside the `swarm-authelia` container, alongside authelia itself — so it
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simply owns the file it writes. No elevated privilege anywhere.
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## Shape
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- One endpoint, `POST /requests`, body = `swarm-authelia-bridge-sock`'s
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`BridgeRequest` verbatim — one variant today (`EnsureAgentIdentity`,
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idempotently ensure an agent exists as an authelia subject).
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- Bearer-authenticated via authelia's own OIDC token introspection (RFC
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7662), against `swarm-controller`'s **existing** machine-client identity
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(already minted for the queue connection) — no new credential.
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- No restart of authelia after a write — relies on
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`authentication_backend.file.watch`, confirmed working against the
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pinned 4.39.20 build during this design work.
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- Network-facing rather than unix-socket-only: `swarm-authelia`'s container
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shares the host netns, so the same listener serves both a co-located
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`swarm-controller` (loopback) and a split-host one (bind wider + firewall)
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with no separate transport.
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## Known limitation
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`swarmctl` still writes an independent `users.json`/`users.yml` for human
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accounts, assuming co-location with `swarm-controller`'s host. Two
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canonical stores for the same physical file is a real seam, not solved
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here — routing `swarmctl` through this bridge too is a plausible follow-up,
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out of scope for the agent-identity slice this crate shipped with.
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