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tsunagiandClaude Opus 5 21be7e9b44 Separate control and data logically, move WireGuard into userspace, add a CLI

Corrects the architecture on two points raised in review, while the project
is still small enough to change cheaply.

1. Control and data are separated *logically*, not physically.

The old reading — "nothing but control may ride on iroh" — threw away iroh's
whole value and would have forced the data plane to reimplement STUN, ICE and
a relay. Now both planes ride on iroh with different ALPNs and different
connections, so the data plane inherits hole punching and relay fallback,
while proto/ still knows nothing about packets and dataplane/ knows nothing
about the control protocol.

New boundary: PacketTransport / PacketLink, an authenticated unreliable
datagram channel per (network, peer, protocol). tsunagi/data/1 runs the same
membership handshake, then DataOpen/DataOpenAck, then QUIC datagrams. Only
the smaller endpoint id dials, so exactly one link exists per pair.

A plugin is handed links and never learns reachability, so the WireGuard
announcement shrank to a public key: there is no address left to lie about.

2. WireGuard now runs in userspace, on boringtun's protocol state machine.

No kernel module, no wg tool, no ip shell-out, no loopback proxy: the wgtool,
backend and bridge modules are gone. Only creating a TUN device needs
privileges, and that sits behind TunFactory, so the entire data plane —
handshake, encryption, routing, address ownership — is tested with none.

Address ownership is enforced rather than believed: outbound packets go to
the owner of the destination address, inbound packets are dropped unless
their source is the address derived for the peer that sent them.

3. A `tsunagi` binary: secret, doctor, id, up. It owns the runtime, the
logging subscriber and Ctrl-C, which the library still refuses to.

Also fixes a reference cycle where IrohTransport held Arc<Inner>, which kept
the databases open and the directory lock held after shutdown; two storage
tests caught it once the cycle existed.

81 tests pass offline with no privileges, including real IPv6 packets
crossing a real WireGuard tunnel over real iroh connections. Verified by
hand: two CLI processes forming a mesh both on loopback and via n0 discovery
using only an endpoint id.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

2026-09-21 11:55:20 +01:00

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Threat model and known limits

Read this before relying on anything here. The protocol is in protocol.md.

What is protected

Network membership. A peer must prove knowledge of auth_key, derived from the network name and shared secret, to get an authenticated session. Knowing the public NetworkId, or an agent's address, is not enough.
Endpoint authenticity. iroh's QUIC/TLS handshake authenticates the remote endpoint id, which is its public key. Identities in the membership transcript are taken from the certificate, never from a peer's claim.
Connection binding. The membership proof includes TLS exporter output, so a proof captured on one connection does not verify on another.
Role separation. Initiator and responder proofs cover different transcripts, so a proof cannot be reflected back at its sender.
Network isolation. A session authenticated for network A cannot carry messages for network B, even over a shared physical connection.
Confidentiality and integrity in transit. Provided by QUIC/TLS. This crate adds no encryption of its own.
Overlay address ownership. A peer's overlay address is derived from its public key, not taken from its announcement. Outbound packets go to the owner of the destination address; inbound packets are dropped unless their source is the address derived for the peer that sent them. A member can therefore neither receive nor forge another member's traffic. See wireguard.md.
Tunnelled traffic is end-to-end encrypted by WireGuard, independently of this crate. The transport underneath is also encrypted by iroh, but the tunnel's confidentiality does not depend on that.
Resource bounds. Frame lengths are validated before allocation; strings, lists, queues, concurrent dials and in-flight handshakes are all bounded; handshakes, dials and writes have timeouts.

What is not protected

Anyone who knows the secret is a full participant. They can create arbitrarily many identities, flood the network with records and collide with other participants' names. This is why a majority is not a root of trust. Signatures protect authorship; they do not make a participant honest.
Weak secrets. This targets high-entropy secrets. There is no PAKE, so a short human passphrase can be guessed offline by anyone who can reach the handshake. Use NetworkSecret::generate().
Addresses and metadata are observable. Anyone able to watch the network sees addresses, timing and volume. Discovery backends see the discovery_key and the addresses published under it, which is enough to map a network's participants. This library does not make a network anonymous, and having iroh under it does not make it so.
A cloned state directory is a cloned identity. state.sqlite holds the device secret key and the network secrets. Copying it copies the participant. Restoring an old backup rolls the agent's state back, which — once signed records exist — can resurrect revoked information or replay stale versions.
A compromised host. The secret is on disk to survive restarts. File permissions are owner-only where the platform supports it, and the state directory takes an ownership lock, but neither defends against a user who can read the file or against malware running as that user.
User IP traffic. Carried by the WireGuard plugin over an iroh data connection, and encrypted by WireGuard end to end. Filtering it is still the operating system's and the user's job: the plugin creates connectivity between members and does not police what flows over it.
Traffic metadata reaches the relay when one is used. If iroh cannot hole punch, the data connection goes through a relay, which then sees the volume and timing of tunnelled traffic — though not its contents, which WireGuard encrypted, nor the iroh layer's contents.
Overlay address squatting. A member can mint many WireGuard keys and therefore occupy many overlay addresses. It cannot pick which ones, but it can consume them and appear as many participants.
Plugin keys on disk. The WireGuard private keys live in the plugin's own wireguard.sqlite, owner-only where the platform supports it. Copying that file copies this agent's overlay identity, exactly as copying state.sqlite copies its control plane identity.
What the data plane does not police. Address ownership stops a member impersonating another member. It does not stop a member sending whatever it likes from its own address.
Denial of service. Bounds and timeouts stop trivial resource exhaustion from a single peer. They do not make the agent resistant to a determined attacker who knows the secret, and no rate limiting per identity exists yet.
Global freshness. A signature proves authorship, not that you have the newest state. See sync-model.md.
Discovery is not trustworthy. It returns candidates. A hostile or stale discovery backend can waste dial attempts and learn addresses; it cannot forge membership.

Deliberate design consequences

No owner, no vote. Nobody can evict anybody. Removing a participant means changing the secret, which creates a different network space that the removed participant cannot enter.
Rotating the secret is not revocation of past access. Anyone who held the old secret keeps whatever they already saw.
Local deactivation is not revocation. Deactivating a network stops this agent participating. It says nothing about anyone else.
Failures are contained, not escalated. A bad proof, wrong secret, malformed frame or unknown version rejects one message or one session. It never stops another network and never stops the agent, and there is no irreversible global error flag.

Cryptographic choices

Standard primitives only, no home-made constructions: HKDF-SHA256 (RFC 5869) for key separation, HMAC-SHA256 for the membership proof, constant-time verification, iroh's Ed25519 endpoint keys and QUIC/TLS for the transport, and RFC 5705 TLS exporter output for channel binding. There is no custom encryption layer and no custom PAKE.

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