feat(sandbox): expose screened $axios in script context

Add $axios to the VM sandbox with a request interceptor that blocks
non-http(s) URLs and common SSRF targets (localhost, private IPs,
link-local, and cloud metadata hosts). require('axios') and import
axios resolve to the same screened instance so scripts cannot bypass
URL screening.

Co-authored-by: Nasyarobby Putra <nasyarobby@gmail.com>

script-sandbox.js

@@ -2,6 +2,7 @@ import fs from "fs";
 import vm from "node:vm";
 import { fileURLToPath } from "node:url";
 import { createRequire } from "node:module";
+import axios from "axios";
 
 const hostRequire = createRequire(import.meta.url);
 
@@ -185,11 +186,94 @@ function createConsole(logger) {
   };
 }
 
-function createRestrictedRequire() {
+function isBlockedHostname(hostname) {
+  const host = hostname.toLowerCase().replace(/\.$/, "");
+  if (
+    host === "localhost" ||
+    host === "0.0.0.0" ||
+    host === "[::]" ||
+    host === "[::1]" ||
+    host.endsWith(".localhost")
+  ) {
+    return true;
+  }
+
+  if (host === "metadata.google.internal" || host === "metadata.goog") {
+    return true;
+  }
+
+  const ipv4Match = host.match(/^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/);
+  if (!ipv4Match) {
+    return false;
+  }
+
+  const octets = ipv4Match.slice(1).map(Number);
+  if (octets.some((octet) => octet > 255)) {
+    return true;
+  }
+
+  const [a, b] = octets;
+  if (a === 10) return true;
+  if (a === 127) return true;
+  if (a === 0) return true;
+  if (a === 169 && b === 254) return true;
+  if (a === 172 && b >= 16 && b <= 31) return true;
+  if (a === 192 && b === 168) return true;
+  if (a === 100 && b >= 64 && b <= 127) return true;
+  return false;
+}
+
+function resolveRequestUrl(config) {
+  const target = config.url;
+  if (typeof target !== "string" || target.length === 0) {
+    throw new Error("axios request URL is required");
+  }
+
+  if (/^https?:\/\//i.test(target)) {
+    return new URL(target);
+  }
+
+  const base = config.baseURL;
+  if (typeof base !== "string" || base.length === 0) {
+    throw new Error(`axios request URL must be absolute: ${target}`);
+  }
+
+  return new URL(target, base);
+}
+
+function screenRequestUrl(url, log) {
+  if (url.protocol !== "http:" && url.protocol !== "https:") {
+    throw new Error(`Request blocked: unsupported protocol ${url.protocol}`);
+  }
+
+  if (isBlockedHostname(url.hostname)) {
+    const message = `Request blocked: ${url.href}`;
+    log.warn({ url: url.href, hostname: url.hostname }, message);
+    throw new Error(message);
+  }
+}
+
+/**
+ * @param {import("pino").Logger} log
+ */
+function createScreenedAxios(log) {
+  const instance = axios.create();
+  instance.interceptors.request.use((config) => {
+    const url = resolveRequestUrl(config);
+    screenRequestUrl(url, log);
+    return config;
+  });
+  return instance;
+}
+
+function createRestrictedRequire(screenedAxios) {
   return function restrictedRequire(id) {
     if (typeof id !== "string" || !ALLOWED_MODULES.has(id)) {
       throw new Error(`require(${JSON.stringify(id)}) is not allowed`);
     }
+    if (id === "axios") {
+      return screenedAxios;
+    }
     return hostRequire(id);
   };
 }
@@ -199,11 +283,13 @@ function createRestrictedRequire() {
  */
 function createScriptSandbox({ log, script, workflowName }) {
   const scriptLog = log.child({ workflow: workflowName, script });
+  const $axios = createScreenedAxios(scriptLog);
   const sandbox = {
     ...pickBuiltins(),
     log: scriptLog,
     console: createConsole(scriptLog),
-    require: createRestrictedRequire(),
+    $axios,
+    require: createRestrictedRequire($axios),
   };
 
   vm.createContext(sandbox, {

scripts/ntfy.js

@@ -1,5 +1,4 @@
-import axios from "axios";
-export default function ntfy(ctx) {
+export default async function ntfy(ctx) {
     log.info({ ctx }, "ntfy");
     const headers = {}
     
@@ -7,7 +6,7 @@ export default function ntfy(ctx) {
         headers.Title = ctx.data.title
     }
 
-    axios.post(ctx.config?.url || "https://ntfy.sh/scrunner", ctx.data?.message || "Hello from scrunner", {
+    await $axios.post(ctx.config?.url || "https://ntfy.sh/scrunner", ctx.data?.message || "Hello from scrunner", {
         headers: headers
     })
     return {sent: "true"}