fix(security): require bearer auth on dashboard approval API

Gate /api/approvals routes with DASHBOARD_API_TOKEN when configured.

Author: Sage Hart

src/api/auth.ts

@@ -0,0 +1,39 @@
+import express, { type Request, type Response, type NextFunction } from "express";
+
+/**
+ * Bearer-token gate for dashboard mutating API routes.
+ * Set DASHBOARD_API_TOKEN in the environment; when unset, auth is disabled (dev only).
+ */
+export function requireDashboardAuth(req: Request, res: Response, next: NextFunction): void {
+  const expected = process.env.DASHBOARD_API_TOKEN?.trim();
+  if (!expected) {
+    next();
+    return;
+  }
+  const header = req.headers.authorization ?? "";
+  const prefix = "Bearer ";
+  if (!header.startsWith(prefix)) {
+    res.status(401).json({ error: "dashboard authentication required" });
+    return;
+  }
+  const token = header.slice(prefix.length).trim();
+  if (token.length !== expected.length || !timingSafeEqual(token, expected)) {
+    res.status(401).json({ error: "dashboard authentication required" });
+    return;
+  }
+  next();
+}
+
+function timingSafeEqual(a: string, b: string): boolean {
+  if (a.length !== b.length) return false;
+  let mismatch = 0;
+  for (let i = 0; i < a.length; i++) {
+    mismatch |= a.charCodeAt(i) ^ b.charCodeAt(i);
+  }
+  return mismatch === 0;
+}
+
+export function installDashboardAuth(app: express.Application): void {
+  app.use("/api/approvals", requireDashboardAuth);
+  app.post("/api/approvals/:id/decide", requireDashboardAuth);
+}

src/api/server.ts

@@ -6,6 +6,7 @@ import express from "express";
 import { WebSocketServer, WebSocket } from "ws";
 
 import { newTask, type CompanyServices, type TaskState } from "../core";
+import { installDashboardAuth } from "./auth";
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 const PUBLIC_DIR = resolve(__dirname, "../dashboard/public");
@@ -19,6 +20,7 @@ export interface HttpServerHandles {
 export function createHttpServer(services: CompanyServices): HttpServerHandles {
   const app = express();
   app.use(express.json());
+  installDashboardAuth(app);
 
   // Suppress the browser's default favicon request (no asset shipped).
   app.get("/favicon.ico", (_req, res) => {
@@ -83,11 +85,14 @@ export function createHttpServer(services: CompanyServices): HttpServerHandles {
     const id = req.params.id;
     const body = req.body ?? {};
     const decision = body.decision;
-    const by = typeof body.by === "string" ? body.by : "human";
+    let by = typeof body.by === "string" ? body.by : "human";
     if (decision !== "approved" && decision !== "rejected") {
       res.status(400).json({ error: "decision must be 'approved' or 'rejected'" });
       return;
     }
+    if (process.env.DASHBOARD_API_TOKEN?.trim()) {
+      by = "dashboard-operator";
+    }
     const approval = services.policy.decide(id, decision, by);
     if (!approval) {
       res.status(404).json({ error: "approval not found" });