granthi-sync/README.md

# granthi-sync v1

The signup → download → link-folders → cloud product spine for the Granthi
forge, tested against the BETA forge (granthi-beta.shre.ai). Python 3 stdlib +
git CLI only — same portability heritage as the estate's `gitea_sync.py` mesh.

```
   ┌──────────────┐   device flow    ┌─────────────────┐
   │ granthi-sync │ ───────────────▶ │ shre-id Zitadel │
   │  (client,    │ ◀─────────────── │  id.shre.ai     │
   │  Mac/laptop) │   access token   └─────────────────┘
   │              │
   │              │  POST /v1/link {zitadel_access_token, device_name}
   │              │ ───────────────▶ ┌───────────────────────────────┐
   │              │ ◀─────────────── │ granthi-link  :3042           │
   │              │  {login, token}  │ (granthi VPS, tailnet-only)   │
   │              │                  │  · userinfo validation        │
   │              │  POST /v1/repos  │  · ensure Gitea user (admin)  │
   │              │ ───────────────▶ │  · mint scoped user token     │
   │              │                  └──────────────┬────────────────┘
   │              │   git push/fetch (user token    │ admin API
   │              │   via credential helper)        ▼
   │              │ ───────────────▶ ┌───────────────────────────────┐
   └──────────────┘                  │ BETA forge  :3041             │
                                     │ granthi-beta.shre.ai          │
                                     └───────────────────────────────┘
```

## Components

### `server/granthi_link.py` — provisioning service (granthi VPS)

* `GET /health`
* `POST /v1/link {zitadel_access_token, device_name}` → validates the token
  against `https://id.shre.ai/oidc/v1/userinfo`, applies the **identity
  binding rules** (below), mints a token scoped
  `write:repository,write:user`, returns
  `{gitea_base, login, token, token_name}`. POST bodies are capped at
  **64 KB** (413 beyond; missing `Content-Length` → 411, invalid → 400).
* `POST /v1/repos {token, name, private}` → creates the user repo with the
  USER token; clone/html URLs are rebased onto `public_gitea_base` because the
  container `ROOT_URL` (https://granthi-beta.shre.ai) does not resolve for
  tailnet-only clients.

Deployment: `/opt/granthi-link/{granthi_link.py,config.json,state.json}` +
systemd unit `granthi-link.service`; binds `127.0.0.1:3042` **and**
`100.111.127.127:3042` (tailnet). **Not publicly exposed** — see promotion
window. The service **refuses to start** (exit 2) unless `config.json` is
mode 0600/0400 and owned by the user it runs as — the config carries the
forge admin password, so permissive perms fail closed, not open.

#### Identity binding (`state.json`)

`/v1/link` originally bound purely by `preferred_username` / email
local-part — any Zitadel identity whose derived login collided with an
existing account got a token for that account (account takeover). The
service now persists a map of Zitadel `sub` → Gitea login in
`/opt/granthi-link/state.json` (0600, atomic tmp+rename writes) and applies:

1. **Mapped sub** → always the mapped login, regardless of what the current
   userinfo claims. If the mapped login was deleted from the forge it is
   re-created only when the service created it originally; adopted accounts
   are refused (409).
2. **Unmapped sub, login free** → create the user, record the mapping
   (`created_by_service: true`). A concurrent-create 409 from Gitea is
   handled idempotently: the user is re-fetched and accepted only if its
   primary email is exactly the one this request would have set.
3. **Unmapped sub, login taken** → bind ONLY when the Gitea user's primary
   email equals the Zitadel userinfo `email` **and** `email_verified` is
   true (recorded with `created_by_service: false`); anything else →
   `409 login exists and is not linked to this identity`.

A Gitea token is **never minted before the binding rule passes**, and a
corrupt/unreadable `state.json` fails closed (500) instead of falling back
to an empty map.

**Migration (pre-1.1.0 accounts):** identities whose userinfo carries no
verified `email` (e.g. Zitadel *machine* users) cannot self-adopt an
existing forge login under rule (c) — for them the first link after the
upgrade would 409 forever. Any forge account the v1 service created before
this change must be seeded into `state.json` once, as
`{"<sub>": {"login": "<login>", "created_by_service": true, ...}}`, written
0600 atomically. As of the beta rollout the only such account is the E2E
machine user `granthi-sync-e2e` (seeded); the forge's human admin `nirpa`
is never provisioned through `/v1/link`, so nothing else needed seeding.

Empirically verified mechanics on Gitea **1.27.1** (beta forge):

* Token minting: `POST /api/v1/users/{login}/tokens` returns **401 for
  token-authenticated sudo** (both `Sudo:` header and `?sudo=`); it only works
  with **admin basic auth + `Sudo: <login>` header** (201). The config
  therefore carries `admin_login`/`admin_password` (root-only, 0600) in
  addition to `admin_token` (minted via
  `gitea admin user generate-access-token`, used for all other admin calls).
* User creation: `source_id` is omitted → **local user** with a random
  30-char password, `must_change_password=false`, `visibility=private`.
  Rationale: `/api/v1/admin/identity-auth-sources` 404s on 1.27.1; the
  shre-id OAuth2 source is ID 1 (via `gitea admin auth list`), but users
  attached to an OAuth2 source cannot basic-auth and admin-created users get
  no `external_login_user` row anyway — first OIDC web login links by email
  regardless of this choice.
* `test_mode` (config flag, **never in production**): allows `/v1/link` to
  accept `test_userinfo` in the body instead of a Zitadel round-trip, so E2E
  can exercise the ensure-user + mint path headlessly. It is honored **only
  when the service environment also sets `GRANTHI_LINK_ALLOW_TEST_MODE=1`**;
  a config flag without the env gate is logged as an ERROR and ignored.

### `client/granthi_sync_client.py` (+ `bin/granthi-sync`) — client daemon

* `link [--server URL] [--token TOK]` — Zitadel **device flow** (native app
  `granthi-sync-device`, client_id `386909715541590022`, project
  granthi-forge `386906525790109702`; grants: device_code + refresh_token):
  prints the verification URL + user code, polls the token endpoint
  (`authorization_pending`/`slow_down` handled), then calls `/v1/link`.
  `--token` skips the device flow with a ready Zitadel token (headless/dev).
  Result stored in `~/.granthi-sync/config.json` (0600).
* `add <folder> [--name N] [--private|--public]` — `git init -b main` if
  needed, creates the cloud repo via `/v1/repos`, adds remote `granthi`,
  initial commit + push. The token is delivered by a **git credential
  helper** (the client's hidden `git-credential` subcommand reading the 0600
  config) — never embedded in the remote URL (estate rule).
* `watch [--interval 30] [--once]` — per folder: autocommit
  (`sync: <ISO ts>`) → fetch → ff-pull if remote strictly ahead → push if
  local strictly ahead. **DIVERGED → log + record + SKIP. Never force, never
  merge** — the same policy as the mesh. SIGTERM-clean.
* `status` — table of linked folders, last sync, divergence flags.
* Run as a daemon on macOS with `client/launchd/ai.granthi.sync.plist`
  (edit the script path, then `launchctl bootstrap gui/$UID <plist>`).

## Tests

* `python3 -m unittest discover -s tests` — 53 tests: autocommit/ff/diverged
  logic against real temp git repos (including "diverged never touches the
  remote"), config 0600 handling (including umask-proof creation and a
  no-chmod guard), credential-helper quoting/injection, mocked device-flow
  polling, the full `/v1/link` + `/v1/repos` service flows against an
  in-process stub playing Zitadel + Gitea, all identity-binding rules
  (collision 409, verified-email adoption, deleted-login re-create/refuse,
  concurrent-create race, corrupt-state fail-closed), the test_mode env
  gate, config-permission refusal, and the 64 KB body cap.
* Live E2E against the beta forge is recorded in the delivery notes
  (link → add → watch ff/push → forced divergence → DIVERGED skip verified
  via API, remote sha untouched).

## Invite-only story (v1)

There is no open signup. An operator invites a user by creating them in
shre-id (Zitadel org). The user downloads the client, runs
`granthi-sync link`, signs in at id.shre.ai with the printed device code, and
the provisioning service creates their forge account + scoped token on the
fly — the forge never sees a password and the user never sees the forge admin.
Every linked folder becomes a private repo under their account.

## Promotion window (beta → prod)

1. **Expose :3042** behind cloudflared (granthi.shre.ai vhost or
   link.granthi.shre.ai) — today it is tailnet-only by design.
2. **Swap forge base URLs** in `/opt/granthi-link/config.json`:
   `gitea_base` → prod forge, `public_gitea_base` →
   `https://granthi.shre.ai`; the client default server URL moves to the
   public endpoint.
3. The `granthi-web` OIDC app already lists the prod callback; the device
   app is host-independent. Rotate the beta admin token/password out of the
   config when pointing at prod (prod forge is READ-ONLY to this estate —
   promotion is an operator action, not an agent action).
4. Add rate limiting / abuse controls before public exposure (one token mint
   per link call today).
5. **Hardening checklist (must all hold before exposing):**
   - [ ] `config.json` is 0600 (or 0400) and owned by the service user —
         the service refuses to start otherwise; verify with
         `systemctl status granthi-link` after any config edit.
   - [ ] `test_mode` is absent from the production config **and**
         `GRANTHI_LINK_ALLOW_TEST_MODE` is not set in the unit environment.
   - [ ] `/opt/granthi-link/state.json` exists, is 0600, and is included in
         VPS backups — losing it orphans sub→login bindings (existing users
         would need verified-email re-adoption).
   - [ ] `GET /health` returns 200 on both binds after restart.
   - [ ] Spot-check the identity map: a repeat link for a known sub returns
         the same login; a colliding username with a different sub gets 409.

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