geth/docs/architecture.md

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".

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 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. Iroh-blobs, providers, encrypted blobs, manifests, and file sync trees are future work.

geth-kv, geth-db, geth-document, 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.

The authorization plane is geth-auth: resource-local signed operation logs, grants, revocations, groups, and auth explain.

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.

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.