tsunagiandClaude Opus 5
5cc92d7067
Running `tsunagi up` twice with the same arguments failed with "network ... is already active", and then dropped the iroh endpoint without closing it. A configured network is activated automatically at startup, so the second run found it already up. `join_network` is declarative — "be a member of this network" — so joining one that is already active now succeeds and changes nothing. `activate_network` stays strict for callers that specifically want to know whether an inactive network was started. The CLI now closes the agent on the error path too, and handles SIGTERM as well as Ctrl-C, so a service manager stopping the agent gets the same clean shutdown an interactive user does. Also documents the two lookups people conflate: resolving one endpoint's address is iroh's public pkarr/DNS service and works today, which is why `--peer <endpoint-id>` needs no address; finding who is in a network is this project's `NetworkDiscovery` and is still static bootstrap only. Notes in the README and the threat model that `n0` and `direct` publish this endpoint's addresses to a public third-party service. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
111 lines
6.6 KiB
Markdown
111 lines
6.6 KiB
Markdown
# Threat model and known limits
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Read this before relying on anything here. The protocol is in
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[protocol.md](protocol.md).
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## What is protected
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- **Network membership.** A peer must prove knowledge of `auth_key`, derived
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from the network name and shared secret, to get an authenticated session.
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Knowing the public `NetworkId`, or an agent's address, is not enough.
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- **Endpoint authenticity.** iroh's QUIC/TLS handshake authenticates the
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remote endpoint id, which is its public key. Identities in the membership
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transcript are taken from the certificate, never from a peer's claim.
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- **Connection binding.** The membership proof includes TLS exporter output, so
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a proof captured on one connection does not verify on another.
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- **Role separation.** Initiator and responder proofs cover different
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transcripts, so a proof cannot be reflected back at its sender.
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- **Network isolation.** A session authenticated for network A cannot carry
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messages for network B, even over a shared physical connection.
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- **Confidentiality and integrity in transit.** Provided by QUIC/TLS. This
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crate adds no encryption of its own.
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- **Overlay address ownership.** A peer's overlay address is derived from its
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public key, not taken from its announcement. Outbound packets go to the owner
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of the destination address; inbound packets are dropped unless their source
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is the address derived for the peer that sent them. A member can therefore
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neither receive nor forge another member's traffic. See
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[wireguard.md](wireguard.md#address-ownership-is-enforced-not-announced).
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- **Tunnelled traffic is end-to-end encrypted by WireGuard**, independently of
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this crate. The transport underneath is also encrypted by iroh, but the
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tunnel's confidentiality does not depend on that.
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- **Resource bounds.** Frame lengths are validated before allocation; strings,
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lists, queues, concurrent dials and in-flight handshakes are all bounded;
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handshakes, dials and writes have timeouts.
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## What is not protected
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- **Anyone who knows the secret is a full participant.** They can create
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arbitrarily many identities, flood the network with records and collide with
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other participants' names. This is why a majority is not a root of trust.
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Signatures protect authorship; they do not make a participant honest.
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- **Weak secrets.** This targets high-entropy secrets. There is no PAKE, so a
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short human passphrase can be guessed offline by anyone who can reach the
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handshake. Use `NetworkSecret::generate()`.
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- **Public address publication.** With `TransportPolicy::N0Defaults` or
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`DirectOnly`, iroh publishes a signed record of this endpoint's addresses,
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keyed by its endpoint id, to Number 0's public pkarr/DNS service, and
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resolves peers through it. The network secret is never published and
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membership cannot be inferred from a single record, but the endpoint's
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existence and its addresses become public. `LocalOnly` publishes nothing.
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- **Addresses and metadata are observable.** Anyone able to watch the network
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sees addresses, timing and volume. Discovery backends see the
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`discovery_key` and the addresses published under it, which is enough to map
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a network's participants. This library does not make a network anonymous, and
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having iroh under it does not make it so.
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- **A cloned state directory is a cloned identity.** `state.sqlite` holds the
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device secret key and the network secrets. Copying it copies the participant.
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Restoring an old backup rolls the agent's state back, which — once signed
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records exist — can resurrect revoked information or replay stale versions.
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- **A compromised host.** The secret is on disk to survive restarts. File
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permissions are owner-only where the platform supports it, and the state
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directory takes an ownership lock, but neither defends against a user who can
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read the file or against malware running as that user.
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- **User IP traffic.** Carried by the WireGuard plugin over an iroh data
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connection, and encrypted by WireGuard end to end. *Filtering* it is still
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the operating system's and the user's job: the plugin creates connectivity
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between members and does not police what flows over it.
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- **Traffic metadata reaches the relay when one is used.** If iroh cannot hole
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punch, the data connection goes through a relay, which then sees the volume
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and timing of tunnelled traffic — though not its contents, which WireGuard
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encrypted, nor the iroh layer's contents.
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- **Overlay address squatting.** A member can mint many WireGuard keys and
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therefore occupy many overlay addresses. It cannot pick which ones, but it
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can consume them and appear as many participants.
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- **Plugin keys on disk.** The WireGuard private keys live in the plugin's own
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`wireguard.sqlite`, owner-only where the platform supports it. Copying that
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file copies this agent's overlay identity, exactly as copying `state.sqlite`
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copies its control plane identity.
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- **What the data plane does not police.** Address ownership stops a member
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impersonating another member. It does not stop a member sending whatever it
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likes *from its own* address.
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- **Denial of service.** Bounds and timeouts stop trivial resource exhaustion
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from a single peer. They do not make the agent resistant to a determined
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attacker who knows the secret, and no rate limiting per identity exists yet.
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- **Global freshness.** A signature proves authorship, not that you have the
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newest state. See [sync-model.md](sync-model.md).
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- **Discovery is not trustworthy.** It returns candidates. A hostile or stale
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discovery backend can waste dial attempts and learn addresses; it cannot
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forge membership.
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## Deliberate design consequences
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- **No owner, no vote.** Nobody can evict anybody. Removing a participant means
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changing the secret, which creates a different network space that the removed
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participant cannot enter.
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- **Rotating the secret is not revocation of past access.** Anyone who held the
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old secret keeps whatever they already saw.
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- **Local deactivation is not revocation.** Deactivating a network stops this
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agent participating. It says nothing about anyone else.
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- **Failures are contained, not escalated.** A bad proof, wrong secret,
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malformed frame or unknown version rejects one message or one session. It
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never stops another network and never stops the agent, and there is no
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irreversible global error flag.
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## Cryptographic choices
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Standard primitives only, no home-made constructions: HKDF-SHA256 (RFC 5869)
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for key separation, HMAC-SHA256 for the membership proof, constant-time
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verification, iroh's Ed25519 endpoint keys and QUIC/TLS for the transport, and
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RFC 5705 TLS exporter output for channel binding. There is no custom encryption
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layer and no custom PAKE.
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