jwinterm 586f681287 feat: Grin slatepack relay (non-custodial async mailbox, feature-flagged)
Final wallet-handler slice. An async store-and-forward mailbox for interactive
Grin transfers between two registered Smirk users, over the grin_slatepacks db.
Reworked clean from the legacy relay — NOT a port.

Endpoints (under /api/v1/wallet/grin/relay, JWT-gated):
- POST create   {recipient_user_id, slate_id, slatepack, amount_nanogrin}
- GET  pending  -> the caller's inbox
- POST get      {slate_id} -> poll a relay's state (sender/recipient)
- POST respond  {slate_id, response_slatepack} (recipient)
- POST finalize {slate_id, tx_hash} (sender; RECORDS the txid only)
- POST cancel   {slate_id} (sender or recipient)

Non-custodial: stores only opaque (encrypted) slatepacks + lifecycle status;
never holds keys, finalizes, or broadcasts. The wallet broadcasts locally (via
/wallet/grin/broadcast) and reports the txid here — diverging from the legacy
server-side post_tx (see docs/private/OWN_BACKEND_CONVERGENCE.md).

Controls + hardening (incl. fixes from the adversarial review workflow):
- Per-action authz: caller must be the slate's sender/recipient; a non-party
  gets 404 (no existence oracle).
- slate_id is UNIQUE (+ validated as a UUID) and mutations key on the
  authorized row's PRIMARY KEY, not slate_id — so a duplicate slate_id can't
  brick a relay (fetch_optional-on-2-rows 500) or let a slate_id-keyed UPDATE
  touch another row. create maps the unique violation to 409.
- State transitions are ATOMIC: the status + expiry preconditions live in the
  UPDATE WHERE clause (not a Rust read-check-write), so respond-twice and
  cancel-races-finalize cannot occur; a non-qualifying transition -> 409.
- TTL enforced at the action boundary (respond/finalize require expires_at >
  now) + a periodic expire_old_slatepacks sweep in main.rs (relay-enabled only).
- Recipient must be a registered user; slatepack sizes capped (64 KiB).
- Behind FEATURE_GRIN_RELAY (default on).

6 paths + schemas + grin_relay tag in openapi (drift-clean). 4 L1 integration
tests against live Postgres: full lifecycle, unregistered-recipient 400, auth
gate, non-party/non-recipient 404s.
2026-06-23 17:39:13 -04:00

smirk-backend-core

Open, self-hostable backend for the Smirk non-custodial, multi-chain wallet. It provides the chain-access and identity surface a Smirk wallet needs — authentication, per-chain wallet access (Bitcoin, Litecoin, Monero, Wownero, Grin), the Grin slatepack relay, and Nostr-based identity — so anyone can run their own backend and a Smirk wallet can connect to it.

Status: early, under active development. Interfaces and the database schema may change before the first tagged release. Not yet recommended for production self-hosting.

What it is

  • Non-custodial. The server never holds spend keys or seeds. It brokers access to blockchain data and relays wallet-to-wallet messages.
  • Open core, feature-flagged. Every feature ships in this codebase and is toggled per deployment; the wallet reads GET /api/v1/capabilities and adapts to what a given backend offers.
  • Identity via "Sign in with Smirk". Authentication uses a seed-derived Nostr key (NIP-98); the server stores only public keys.
  • Privacy first. No PII is required to use it; operator and user privacy are explicit design goals.

Architecture

Rust + Axum, PostgreSQL via sqlx. The public HTTP contract is generated from the handlers with utoipa (OpenAPI), which in turn drives the wallet's generated TypeScript client — one source of truth, checked for drift in CI.

Quickstart

cp .env.example .env        # then fill in DATABASE_URL, JWT_SECRET, node URLs
cargo run                   # starts the API server

A full self-hosting guide (node requirements, reverse proxy, Tor admin onion, backups) will live in docs/ as it stabilises.

Security

Please report vulnerabilities privately — see SECURITY.md. Do not open public issues for security reports.

License

To be finalized (MIT vs AGPL-3.0-or-later). Until a LICENSE file is added, all rights are reserved.

S
Description
Mirror of github.com/Such-Software/smirk-backend-core
Readme MIT
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