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archy/docs/adr/004-tor-for-peer-communication.md
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archipelagoandClaude Opus 5 b33138a13d docs(adr): record what ADR-009 actually enforces and amend ADR-004
**ADR-009** lists six "non-negotiable" mandatory security defaults. Checked each
against `core/container/src/manifest.rs` and `core/security/src/`:

- `seccomp_profile: Default` — the string `seccomp` appears **nowhere in
  `core/`**. Not as code, not as a TODO. This constraint is entirely fictional.
- AppArmor — `container_policies.rs` generates and `apparmor_parser -r`s a
  profile, but its own comment reads `TODO: Configure Podman to use the
  profile`. `security.apparmor_profile` parses into a manifest field that
  nothing ever reads.
- `user` UID > 1000 — no UID validation exists in the runtime parser at all.
- `image_tag` pinned — preflight script only; the parser accepts `:latest`.
- `readonly_root` / `no_new_privileges` — safe defaults when omitted, but
  `validate_security()` never rejects an explicit `false`, so the ADR's
  "Reject manifests that violate mandatory defaults" step does not exist.

Genuinely enforced: the capability allow-list and bind-mount confinement (the
latter stronger than the ADR describes). Added an Implementation status section
saying so per-row. The decision stands; the claim of enforcement did not, and on
a security ADR that gap is the whole point of writing it down.

**ADR-004** said Tor carries *all* inter-node communication and runs as the
`archy-tor` container. Neither holds: transport priority is mesh → LAN → FIPS →
Tor (`TransportKind` 1-4, Tor as last fallback, largely because of the latency
this ADR itself lists), and Tor is the host Debian service driven by
`archipelago-tor-helper` — `container-doctor.sh` actively removes an `archy-tor`
container if it finds one, and no `apps/tor` manifest exists. Added an amendment
rather than rewriting the record. Worth flagging that both changes landed
without their own ADR.

All 10 ADRs are Status: Accepted; 001-003, 005-008 and 011 verified consistent.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-08 04:06:55 -04:00

2.9 KiB
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ADR-004: Tor Hidden Services for Peer Communication

Status: Accepted (2026-03) — partially superseded in practice, see Amendment below Date: 2026-03

Context

Federated nodes need to communicate directly for state sync, app deployment, and peer verification. Options: direct IP, VPN tunnel, Tor hidden services, I2P.

Decision

Use Tor hidden services (.onion addresses) for all inter-node communication.

Consequences

Positive

  • NAT traversal: Works behind any firewall or NAT without port forwarding
  • IP privacy: Nodes never expose their real IP addresses to each other
  • End-to-end encryption: Tor provides encryption without additional TLS setup
  • Censorship resistance: Onion routing makes traffic analysis difficult
  • Stable addressing: .onion addresses persist across IP changes and network migrations
  • No central infrastructure: No VPN server, STUN/TURN server, or relay needed

Negative

  • Latency: Tor adds 200-500ms per hop; 3 hops per direction = noticeable delay
  • Bandwidth: Tor network has limited bandwidth; not suitable for bulk data transfer
  • Reliability: Tor circuits can break; connections may need retry logic
  • Setup complexity: Requires running a Tor daemon (archy-tor container)
  • Blocked networks: Some networks block Tor; bridges can help but add complexity

Mitigation

  • Use Tor only for RPC/control plane; bulk data (container images) pulled from registries
  • Implement retry with backoff for Tor connections
  • Container archy-tor runs automatically with host networking for hidden service access
  • Federation sync interval (5 min) tolerates occasional connection failures

Amendment (recorded 2026-08)

Two things in this ADR no longer describe the system. Both changes happened without their own ADR, which is itself worth noting.

1. Tor is no longer used for all inter-node communication — it is the last fallback. The transport layer now tries, in order, mesh radio → LAN → FIPS overlay → Tor (transport::TransportKind, priority 14). The latency and bandwidth costs listed above are exactly why: FIPS was introduced to carry WAN peering that Tor made too slow, and direct LAN peering skips the overlay entirely for co-located nodes. Tor's NAT-traversal and IP-privacy properties are still what make it the dependable floor when the others are unavailable.

2. Tor does not run as the archy-tor container. It is the host's Debian tor package, running as debian-tor and driven by the archipelago-tor-helper path unit (scripts/tor-helper.sh), which installs a staged /etc/tor/torrc and restarts the service. The migration was deliberate and is still enforced: scripts/container-doctor.sh removes an archy-tor container if it finds one and switches the node to system Tor. There is no apps/tor manifest.

The decision to use onion services for peer reachability stands; only its exclusivity and its packaging changed.