policy: ensure workers do not read fs for policy

This prevents a main thread from rewriting the policy file and loading
a worker that has a different policy from the main thread.

PR-URL: https://github.com/nodejs/node/pull/25710
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/lib/internal/process/policy.js b/lib/internal/process/policy.js
index 0b037d4ef5..823130e3c1 100644
--- a/lib/internal/process/policy.js
+++ b/lib/internal/process/policy.js
@@ -5,10 +5,14 @@ const {
 } = require('internal/errors').codes;
 const { Manifest } = require('internal/policy/manifest');
 let manifest;
+let manifestSrc;
+let manifestURL;
 
 module.exports = Object.freeze({
   __proto__: null,
   setup(src, url) {
+    manifestSrc = src;
+    manifestURL = url;
     if (src === null) {
       manifest = null;
       return;
@@ -31,6 +35,20 @@ module.exports = Object.freeze({
     return manifest;
   },
 
+  get src() {
+    if (typeof manifestSrc === 'undefined') {
+      throw new ERR_MANIFEST_TDZ();
+    }
+    return manifestSrc;
+  },
+
+  get url() {
+    if (typeof manifestURL === 'undefined') {
+      throw new ERR_MANIFEST_TDZ();
+    }
+    return manifestURL;
+  },
+
   assertIntegrity(moduleURL, content) {
     this.manifest.matchesIntegrity(moduleURL, content);
   }