# Architecture `geth` is a single-binary local-first mesh runtime. One executable provides both daemon mode and control mode. The daemon owns local identity, metadata storage, the shared Iroh endpoint, resource registry, module routing, and local control socket. Control commands connect to the Unix socket and send typed JSONL requests. Service management is also exposed through the single binary. `geth daemon service ...` installs and controls a user-level service definition for the local daemon. The initial backends are systemd user units on Linux, launchd user agents on macOS, and per-user scheduled tasks on Windows. Geth does not install itself as a privileged system service. ## Iroh-Only Remote Communication Remote geth node-to-node communication is Iroh-only. The daemon will own one shared Iroh endpoint and register module protocols on ALPNs such as `/geth/cas/1`, `/geth/kv/1`, `/geth/pipe/1`, and `/geth/ssh-proxy/1`. The first pinned Iroh integration uses `iroh = 0.90.0`, because newer Rust-1.85-compatible candidates in the 0.93-0.95 range failed to compile through a transitive `ed25519-dalek` prerelease dependency. `geth-iroh` wraps `iroh::Endpoint::builder()`, configures geth ALPNs with `Builder::alpns`, uses `Builder::relay_mode`, persists an `iroh::SecretKey` as hex-encoded 32-byte key material, and shuts down through `Endpoint::close().await`. The default config uses Iroh's default relay policy; local-only/offline development can set `[iroh].relay_mode = "disabled"`. Named custom relay maps are configured under `[iroh.relay_maps.]`, selected with `relay_mode = "custom"` plus `relay_map = ""`, validated at config load, and reported in status as `custom:` without exposing relay URLs. Module ALPNs are registered through `geth-iroh`'s protocol router scaffold. The router owns the default protocol descriptors, rejects duplicate ALPN registrations, and returns explicit unknown-ALPN errors. It does not yet accept or dispatch remote streams; peer authentication and module handlers are later Phase 1 work. The target product should use Iroh relay support for practical internet connectivity and mDNS/LAN discovery for local networks. These are connectivity and candidate-discovery mechanisms only. They do not grant trust, mutate authorization state, or make EndpointID knowledge sufficient for access. The current daemon can enable Iroh's local-network discovery service through `[iroh].local_discovery = true`, which is the default. This publishes and discovers Iroh node addressing. Signed geth peer-card payloads over LAN discovery remain separate future work. Peer cards are the discovery payload. A peer card carries node ID, agent ID, endpoint candidates, timestamp, and signature metadata. The current scaffold stores peer cards as untrusted metadata in `peer_cards`; signature verification and trust reduction are future work. `auth explain` reports when a subject is only a discovered peer candidate and denies access. The daemon starts this endpoint during `geth daemon run` and keeps it alive for the daemon lifetime. When endpoint startup succeeds, the Iroh EndpointID is recorded as a transport binding for the stable geth node identity. If local UDP binding is unavailable, the daemon keeps local control running and reports the Iroh startup error through status output. SSH keys are not transport keys. They are admin trust anchors and signing identities for keychain and authorization operations. SSH proxying, when added, will carry SSH bytes over an authorized Iroh stream and will not make SSH a geth transport backend. SSH certificate flows use the same split. Nodes can request new OpenSSH certificates or renewals through geth metadata. A machine with the CA key or YubiKey can approve the request and run an explicit `ssh-keygen -s ...` command, then import the resulting certificate for distribution. Certificate and key revocations are stored as signed-list-ready records and will be replicated over Iroh in later phases. ## Resource Model Everything meaningful is modeled as a resource. Resources have a kind, name, authority reference, local role, replication policy, retention policy, and status. Authorization is resource-scoped and capability-based. Resource kinds: - `db`: cr-sqlite-backed SQLite synchronization - `kv`: Iroh Documents backed key-value data - `pipe`: authorized byte streams and forwarding - `document`: Automerge CRDT documents - `pubsub`: lossy notifications and presence - `cas`: content-addressed blobs - `ssh-proxy`: SSH/admin proxying over Iroh ## Module Overview `geth-cas` is implemented locally first using BLAKE3 hashes and filesystem blob storage. Local pin/unpin metadata is tracked in SQLite and surfaced in `cas list`. `cas cleanup` removes unpinned local blobs while retaining pinned blobs. Iroh-blobs, providers, encrypted blobs, richer cache policies, manifests, and file sync trees are future work. `geth-db` currently registers local SQLite paths as DB resources and reports local-only sync status plus a read-only SQLite schema summary/hash. cr-sqlite loading, change extraction, and DB sync are future work. `geth-kv` currently provides a SQLite-backed local fallback for named KV stores through `kv create/set/get`. Iroh Documents namespaces, prefix authorization enforcement, and replication are future work. `geth-document` currently registers local document resources with an empty JSON state placeholder and local-only sync status. Automerge state, editing, and sync are future work. `geth-pubsub`, `geth-pipe`, and `geth-ssh-proxy` currently define types, command shape, and roadmap stubs. `geth-ssh-identity` defines SSH trust namespaces plus certificate request, approval, certificate import, and revocation-list data models. The bootstrap persists these flows locally and exports revocations as JSONL. It does not yet generate OpenSSH KRL binaries or replicate the lists over Iroh. ## Keychain, Auth, And Secrets The identity plane is `geth-keychain`: admin keys, users, devices, nodes, agents, and endpoint bindings. Endpoint rotation must not destroy higher-level node identity. Keychain operations reduce into an active view containing current admin keys, users, devices, node records, agent bindings, and endpoint-to-node bindings. Revoked identity subtrees are excluded from that active view. The daemon persists local keychain init/admin-key operations and `keychain status` reports the reduced local view. OpenSSH signature capture and verification for those operations is still future work. The authorization plane is `geth-auth`: resource-local signed operation logs, grants, revocations, groups, and `auth explain`. Auth operations reduce into a current permission view for resources, grants, groups, and bearer access. The library can explain direct and group grants. The daemon persists local auth grant/revoke operations and `geth auth explain` evaluates that local operation log. Signature validation, replication, and module enforcement are still future work. Both keychain and auth operations use `geth-codec` canonical envelopes for signature payloads. The envelope includes a version, an explicit signature namespace, and the operation payload encoded with postcard. JSON remains useful for CLI/control output, but it is not the signed representation. The payload access plane is `geth-secrets`: resource master secrets, epochs, key envelopes, bearer secrets, and rotation. Revocation for private data is modeled initially as secret epoch rotation. The daemon persists resource secret epoch metadata through `secret create/rotate/status`. Bearer access is recorded as resource-scoped auth operations and rejects trust-mutation capabilities such as `auth.delegate`, `auth.revoke`, and `node.enroll`. The daemon does not yet store payload key material, encrypt resource data, or distribute key envelopes. ## Multi-User Direction The project is structured for future multi-user local-first authorization: - authorization is replicated data, not one mutable ACL blob - resources can carry or delegate to their own auth state - users, devices, nodes, agents, and endpoints are separate principals - capabilities are the underlying permission unit - bearer access is resource-scoped and does not mutate the trust graph - offline revocation is eventual - encryption key distribution is part of authorization ## Keyhive/BeeKEM Roadmap Resource secret epochs are the v0/v1 approximation for private payload access. Later designs can add Keyhive-like convergent capabilities and BeeKEM/CGKA-style group key evolution. The bootstrap does not implement BeeKEM and does not claim strong forward secrecy or post-compromise security. ## Security Invariants - All remote node-to-node communication is over Iroh. - SSH is not a geth transport. - SSH keys are admin trust anchors and signing identities. - Agent/node keys handle routine local identity. - Discovery is untrusted. - Knowing an EndpointID does not grant access. - Bearer secrets are resource-scoped capabilities. - Bearer access does not imply trust graph mutation rights. - Authorization is capability-based and resource-scoped. - SSH certificate issuance must be explicitly approved by an authorized principal before signing. - SSH certificate and key revocations are durable metadata that should be distributed over Iroh, not fetched through unauthenticated discovery. - Network and control decoders treat input as untrusted. - Service installation targets user service managers, not system service managers.