token-gated-economy/artifacts/api-server/src/routes/relay.ts

/**
 * relay.ts — Nostr relay write-policy API
 *
 * POST /api/relay/policy
 *   Internal endpoint called exclusively by the relay-policy sidecar.
 *   Protected by a shared secret (RELAY_POLICY_SECRET env var) sent as a
 *   Bearer token in the Authorization header.
 *
 *   Body: strfry plugin event object
 *   {
 *     event: { id, pubkey, kind, created_at, tags, content, sig },
 *     receivedAt: number,
 *     sourceType: "IP4" | "IP6" | ...,
 *     sourceInfo: string
 *   }
 *
 *   Response: strfry plugin decision
 *   { id: string, action: "accept" | "reject" | "shadowReject", msg?: string }
 *
 * Bootstrap state (Task #36):
 *   All events are rejected until the account whitelist is implemented.
 *   The endpoint and decision contract are stable; future tasks extend the
 *   logic without changing the API shape.
 */

import { Router, type Request, type Response } from "express";
import { makeLogger } from "../lib/logger.js";

const logger = makeLogger("relay-policy");
const router = Router();

const RELAY_POLICY_SECRET = process.env["RELAY_POLICY_SECRET"] ?? "";

// ── Types ─────────────────────────────────────────────────────────────────────

type PolicyAction = "accept" | "reject" | "shadowReject";

interface NostrEvent {
  id: string;
  pubkey: string;
  kind: number;
  created_at: number;
  tags: string[][];
  content: string;
  sig: string;
}

interface PolicyRequest {
  event: NostrEvent;
  receivedAt: number;
  sourceType: string;
  sourceInfo: string;
}

interface PolicyDecision {
  id: string;
  action: PolicyAction;
  msg: string;
}

// ── Helpers ───────────────────────────────────────────────────────────────────

function reject(id: string, msg: string): PolicyDecision {
  return { id, action: "reject", msg };
}

// ── POST /relay/policy ────────────────────────────────────────────────────────

router.post("/relay/policy", (req: Request, res: Response) => {
  // ── Authentication — Bearer token must match RELAY_POLICY_SECRET ──────────
  if (RELAY_POLICY_SECRET) {
    const authHeader = req.headers["authorization"] ?? "";
    const token = authHeader.startsWith("Bearer ") ? authHeader.slice(7).trim() : "";
    if (token !== RELAY_POLICY_SECRET) {
      // Use constant-time-ish comparison for secret matching
      res.status(401).json({ error: "Unauthorized" });
      return;
    }
  } else {
    // No secret configured — warn and allow only from localhost/loopback
    const ip = req.ip ?? "";
    const isLocal = ip === "127.0.0.1" || ip === "::1" || ip === "::ffff:127.0.0.1";
    if (!isLocal) {
      logger.warn("relay/policy: no secret configured, rejecting non-local call", { ip });
      res.status(401).json({ error: "Unauthorized" });
      return;
    }
    logger.warn("relay/policy: RELAY_POLICY_SECRET not set — accepting local-only calls");
  }

  // ── Validate request body ─────────────────────────────────────────────────
  const body = req.body as Partial<PolicyRequest>;
  const event = body.event;

  if (!event || typeof event !== "object") {
    res.status(400).json({ error: "Missing 'event' in request body" });
    return;
  }

  const eventId = typeof event.id === "string" ? event.id : "unknown";
  const pubkey  = typeof event.pubkey === "string" ? event.pubkey : "";
  const kind    = typeof event.kind === "number" ? event.kind : -1;

  // ── Policy decision ───────────────────────────────────────────────────────
  //
  // Bootstrap state: reject everything.
  //
  // This is intentional — the relay is deployed but closed until the account
  // whitelist (Task #37) is implemented. Once the whitelist route is live,
  // this function will:
  //   1. Check nostr_identities whitelist for pubkey
  //   2. Check event pre-approval queue for moderated content
  //   3. Return accept / shadowReject based on tier and moderation status
  //
  const decision = evaluatePolicy(eventId, pubkey, kind);

  logger.info("relay policy decision", {
    eventId: eventId.slice(0, 8),
    pubkey: pubkey.slice(0, 8),
    kind,
    action: decision.action,
    sourceType: body.sourceType,
  });

  res.json(decision);
});

/**
 * Evaluate the write policy for an incoming event.
 *
 * Bootstrap: all events rejected until whitelist is implemented (Task #37).
 * The function signature is stable — future tasks replace the body.
 */
function evaluatePolicy(
  eventId: string,
  pubkey: string,
  _kind: number,
): PolicyDecision {
  void pubkey; // will be used in Task #37 whitelist check

  return reject(
    eventId,
    "relay not yet open — whitelist pending (Task #37)",
  );
}

export default router;