Fix critical and high security issues

- exec_script: relay now enforces admin role before forwarding to agent
- relay CORS: restrict allow_origins via ALLOWED_ORIGINS env var (docker-compose passes app URL)
- session-code: replace Math.random() with crypto.randomInt, add per-key rate limit (10 req/min)
- sessions GET: fix IDOR — users can only read their own sessions (admins see all)
- signal API: validate session ownership on create; enforce ownerUserId on all subsequent actions

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/api/agent/session-code/route.ts

@@ -2,16 +2,34 @@ import { db } from '@/lib/db'
 import { machines, sessionCodes } from '@/lib/db/schema'
 import { eq, and } from 'drizzle-orm'
 import { NextRequest, NextResponse } from 'next/server'
+import { randomInt } from 'crypto'
 
 function generateSessionCode(): string {
   const chars = 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789'
   let code = ''
   for (let i = 0; i < 6; i++) {
-    code += chars.charAt(Math.floor(Math.random() * chars.length))
+    code += chars.charAt(randomInt(chars.length))
   }
   return code
 }
 
+// Simple in-process rate limiter: max 10 requests per minute per access key
+const rateLimitMap = new Map<string, { count: number; resetAt: number }>()
+const RATE_LIMIT = 10
+const RATE_WINDOW_MS = 60_000
+
+function isRateLimited(key: string): boolean {
+  const now = Date.now()
+  const entry = rateLimitMap.get(key)
+  if (!entry || now >= entry.resetAt) {
+    rateLimitMap.set(key, { count: 1, resetAt: now + RATE_WINDOW_MS })
+    return false
+  }
+  if (entry.count >= RATE_LIMIT) return true
+  entry.count++
+  return false
+}
+
 export async function POST(request: NextRequest) {
   try {
     const { accessKey } = await request.json()
@@ -20,6 +38,10 @@ export async function POST(request: NextRequest) {
       return NextResponse.json({ error: 'Access key required' }, { status: 400 })
     }
 
+    if (isRateLimited(accessKey)) {
+      return NextResponse.json({ error: 'Too many requests' }, { status: 429 })
+    }
+
     const machineResult = await db
       .select()
       .from(machines)