Igrantio Issuer Backend

iGrant.io issuer backend (OpenID4VCI)

When to use

Build or extend the server that an issuer frontend talks to. It composes three building blocks for the issuance flow only (least privilege): igrantio-backend-proxy + igrantio-backend-webhooks + igrantio-backend-sse. For the verifier equivalent use igrantio-verifier-backend (separate skill). Read igrantio-ows-overview first for the API and architecture.

Before you build: run the integrator intake in igrantio-ows-overview - environment, API key, tenancy, backend host, webhooks, frontend - one question at a time, a recommended default with each.

What it does

• Proxy GET|POST|PUT|DELETE ${PROXY_PREFIX}/{tenant}/... → OWS, injecting the tenant's ApiKey. Allow-lists only OWS credential endpoints (issue, history).
• Register the issuer webhook idempotently (ISSUER_TOPICS) via scripts/register-webhook.ts.
• Receive POST /webhook, verify the X-iGrant-Signature HMAC, extract the CredentialExchangeId, store the event.
• SSE GET /webhook/sse/{CredentialExchangeId} streams the event to the browser; DELETE /webhook/{id} lets it consume-and-delete.

Reference implementation

Runnable Express + TypeScript app in ./references:

references/
  src/config.ts          env config
  src/tenants.ts         TenantStore - per-tenant API-key resolution (env or pluggable)
  src/eventStore.ts      in-memory event store (swap for Redis/Postgres)
  src/topics.ts          ISSUER_TOPICS + topic→exchangeId extraction
  src/proxy.ts           API-key-injecting reverse proxy (allow-list param)
  src/webhooks.ts        HMAC verify + receiver
  src/sse.ts             SSE stream + consume-and-delete
  src/server.ts          composition (issuer allow-list = credential/* only)
  src/registerWebhook.ts idempotent register helper
  scripts/register-webhook.ts   CLI
  .env.example  Dockerfile  package.json  tsconfig.json

Steps

1. cd references && cp .env.example .env, then set OWS_BASE_URL, WEBHOOK_SECRET_KEY, PUBLIC_BASE_URL, CORS_ORIGINS, and one OWS_TENANT_<SLUG>_API_KEY per organisation.
2. npm install && npm run dev - backend on :6001.
3. Register the webhook once per tenant: npm run register-webhook -- <tenant> (idempotent - safe to re-run; skips if the payloadUrl already exists).
4. Point the issuer frontend base URL at ${PUBLIC_BASE_URL}${PROXY_PREFIX}/<tenant> and the webhook base at ${PUBLIC_BASE_URL}/webhook.

Issuance contract (what the frontend drives through this backend)

• POST …/credential/issue → response credentialHistory.CredentialExchangeId (SSE key) + credentialHistory.credentialOffer (QR URI).
• Deferred: on webhook openid.credential.offer_received, PUT …/credential/history/{CredentialExchangeId} with the claims.
• Done on webhook openid.credential.credential_accepted / token_issued. See igrantio-ows-overview/references/api-reference.md §1 and §4.

Adapting

• Multi-instance: replace InMemoryEventStore with a shared store (Redis/Postgres) implementing EventStore.
• Key storage: replace EnvTenantStore with a DB/secret-manager TenantStore.
• Path scope: ISSUER_PERMITTED_PREFIXES in server.ts is the allow-list.

Validation / done criteria

• npm run typecheck passes.
• A wrong/absent X-iGrant-Signature yields 401; a valid one stores the event.
• Hitting a non-credential OWS path through the proxy yields 404 (least privilege).
• The browser SSE fires within ~1s of the webhook arriving, keyed by CredentialExchangeId.

Documentation & workflows

When anything is unclear, consult the iGrant.io documentation before guessing:

• iGrant.io developer APIs (index): https://docs.igrant.io/docs/developer-apis
• Getting started: https://docs.igrant.io/docs/get-started/
• OpenID4VC API (issuer / verifier / webhook): https://docs.igrant.io/docs/category/openid4vc-api/issuer
• Workflow: issue a credential (OID4VCI): https://docs.igrant.io/docs/openID4vci-issue-credential-intime/
• Configure a webhook: https://docs.igrant.io/docs/openid4vc-api/config-create-webhook