marketplaces/docs/backend/TENANT-API-DOMAIN-HANDOFF.md

# Final handoff: tenant API domains

This is the required production contract between the shared frontend, nginx,
and the backend. It supersedes any fixed `api.dexarmarket.ru` or same-origin
`/backend` routing proposal.

## 1. Deterministic hostname rule

The frontend prefixes the **complete** storefront hostname with `api.`:

| Storefront | API origin | Bootstrap |
|---|---|---|
| `example.com` | `https://api.example.com` | `https://api.example.com/bootstrap` |
| `store1.example.com` | `https://api.store1.example.com` | `https://api.store1.example.com/bootstrap` |
| `www.example.com` | `https://api.www.example.com` | `https://api.www.example.com/bootstrap` |

Bootstrap, auth, legacy routes, and `/api/...` routes all use this origin.
Localhost is the only exception and continues through the local `/api` proxy.

## 2. Backend changes required

For every request received publicly on `api.<storefront-host>`:

1. Behind the trusted project nginx, use `X-Storefront-Host`. nginx deliberately
   sends the same storefront value as upstream `Host` for compatibility with the
   currently live backend and preserves the public API hostname in
   `X-Forwarded-Host`.
2. Without that trusted proxy, normalize the request `Host`: lowercase, remove
   the port, remove exactly one leading `api.` label when present, and retain
   every remaining label.
3. Resolve that normalized storefront hostname through the tenant-domain
   registry. Do not infer a tenant from only the first label.
4. Reject unknown, disabled, or unverified domains with `403` before reading
   tenant data. Never fall back to the default/Dexar tenant.
5. Bind the authenticated session to the resolved tenant and reject a mismatch.
6. Trust `X-Storefront-Host` / `X-Forwarded-*` only from the known nginx proxy;
   direct clients can forge them.
7. Return JSON for `/bootstrap`, including a tenant identity that matches the
   normalized storefront domain. HTML or a default tenant response is a fault.

Pseudo-code:

```text
if request.remoteAddress is trustedProxy:
    storefrontHost = lower(stripPort(request.header["X-Storefront-Host"]))
else:
    requestHost = lower(stripPort(request.host))
    storefrontHost = removeAtMostOnePrefix(requestHost, "api.")
tenant = registry.findVerifiedDomain(storefrontHost) ?? forbidden()
request.tenant = tenant
```

## 3. CORS contract

For API host `api.<storefront-host>`, allow exactly:

```http
Access-Control-Allow-Origin: https://<storefront-host>
Access-Control-Allow-Credentials: true
Vary: Origin
Access-Control-Allow-Methods: GET, POST, PUT, PATCH, DELETE, OPTIONS
Access-Control-Allow-Headers: Authorization, Content-Type, AdminWebSessionID, X-Requested-With
```

Answer valid preflight requests with `204`. Do not use `*` together with
credentials. nginx applies this policy now; the backend should enforce the same
allowlist when it is reached without that proxy.

## 4. nginx and TLS

Run the idempotent project script as root:

```bash
scripts/deploy/configure-api-domain.sh \
  --domain gorbushka.market \
  --email ops@example.com \
  --upstream https://127.0.0.1:445
```

It creates `api.gorbushka.market`, issues/renews its certificate, configures
CORS, and proxies all paths to the backend. Upstream receives
`Host: gorbushka.market`, `X-Forwarded-Host: api.gorbushka.market`, and
`X-Storefront-Host: gorbushka.market`; the script then reloads nginx and verifies
that `/bootstrap` returns a JSON object.

For `store1.example.com`, both DNS and TLS must exist for
`api.store1.example.com`. A certificate for `*.example.com` does **not** cover
that two-label-deep hostname.

## 5. CI/CD contract

`deploy.yml` runs the same root-owned configurator before activating a frontend
release. Required production secrets:

| Secret | Example |
|---|---|
| `DEPLOY_HOST` | server hostname/IP |
| `DEPLOY_USER` | `deploy` |
| `DEPLOY_SSH_KEY` | private deploy key |
| `DEPLOY_KNOWN_HOSTS` | pinned SSH host-key line |
| `STOREFRONT_DOMAINS` | `gorbushka.market store1.example.com` |
| `CERTBOT_EMAIL` | operations email |
| `BACKEND_UPSTREAM` | `https://127.0.0.1:445` (optional default) |

One-time provisioning must first run `server-setup.sh`; it installs the helper
as root-owned `/usr/local/sbin/marketplaces-configure-api-domain` and grants the
deploy user permission to run only that validated command plus nginx reload.

## 6. Acceptance checks

For every storefront domain, all of these must pass:

```bash
curl -fsS https://api.example.com/bootstrap | jq -e 'type == "object"'
curl -i -X OPTIONS https://api.example.com/bootstrap \
  -H 'Origin: https://example.com' \
  -H 'Access-Control-Request-Method: GET'
```

- Frontend bundle contains no fixed marketplace API hostname.
- Root and nested storefronts call their matching `api.<full-hostname>`.
- Unknown API hosts return `403`, not the default tenant.
- `/bootstrap` returns JSON and the correct tenant.
- API responses never return the Angular `index.html` fallback.