policy: manifest with subresource integrity checks

This enables code loaded via the module system to be checked for
integrity to ensure the code loaded matches expectations.

PR-URL: nodejs#23834
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Vladimir de Turckheim <vlad2t@hotmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

doc/api/cli.md

@@ -90,6 +90,13 @@ added: v8.5.0
 
 Enable experimental ES module support and caching modules.
 
+### `--experimental-policy`
+<!-- YAML
+added: TODO
+-->
+
+Use the specified file as a security policy.
+
 ### `--experimental-repl-await`
 <!-- YAML
 added: v10.0.0

doc/api/errors.md

@@ -1380,6 +1380,39 @@ An attempt was made to open an IPC communication channel with a synchronously
 forked Node.js process. See the documentation for the [`child_process`][] module
 for more information.
 
+<a id="ERR_MANIFEST_ASSERT_INTEGRITY"></a>
+### ERR_MANIFEST_ASSERT_INTEGRITY
+
+An attempt was made to load a resource, but the resource did not match the
+integrity defined by the policy manifest. See the documentation for [policy]
+manifests for more information.
+
+<a id="ERR_MANIFEST_INTEGRITY_MISMATCH"></a>
+### ERR_MANIFEST_INTEGRITY_MISMATCH
+
+An attempt was made to load a policy manifest, but the manifest had multiple
+entries for a resource which did not match each other. Update the manifest
+entries to match in order to resolve this error. See the documentation for
+[policy] manifests for more information.
+
+<a id="ERR_MANIFEST_PARSE_POLICY"></a>
+### ERR_MANIFEST_PARSE_POLICY
+
+An attempt was made to load a policy manifest, but the manifest was unable to
+be parsed. See the documentation for [policy] manifests for more information.
+
+<a id="ERR_MANIFEST_TDZ"></a>
+### ERR_MANIFEST_TDZ
+
+An attempt was made to read from a policy manifest, but the manifest
+initialization has not yet taken place. This is likely a bug in Node.js.
+
+<a id="ERR_MANIFEST_UNKNOWN_ONERROR"></a>
+### ERR_MANIFEST_UNKNOWN_ONERROR
+
+A policy manifest was loaded, but had an unknown value for its "onerror"
+behavior. See the documentation for [policy] manifests for more information.
+
 <a id="ERR_MEMORY_ALLOCATION_FAILED"></a>
 ### ERR_MEMORY_ALLOCATION_FAILED
 
@@ -1590,6 +1623,13 @@ An attempt was made to operate on an already closed socket.
 
 A call was made and the UDP subsystem was not running.
 
+<a id="ERR_SRI_PARSE"></a>
+### ERR_SRI_PARSE
+
+A string was provided for a Subresource Integrity check, but was unable to be
+parsed. Check the format of integrity attributes by looking at the
+[Subresource Integrity specification][].
+
 <a id="ERR_STREAM_CANNOT_PIPE"></a>
 ### ERR_STREAM_CANNOT_PIPE
 
@@ -2229,7 +2269,9 @@ such as `process.stdout.on('data')`.
 [domains]: domain.html
 [event emitter-based]: events.html#events_class_eventemitter
 [file descriptors]: https://en.wikipedia.org/wiki/File_descriptor
+[policy]: policy.html
 [stream-based]: stream.html
 [syscall]: http://man7.org/linux/man-pages/man2/syscalls.2.html
+[Subresource Integrity specification]: https://www.w3.org/TR/SRI/#the-integrity-attribute
 [try-catch]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/try...catch
 [vm]: vm.html

doc/api/index.md

@@ -39,6 +39,7 @@
 * [OS](os.html)
 * [Path](path.html)
 * [Performance Hooks](perf_hooks.html)
+* [Policies](policy.html)
 * [Process](process.html)
 * [Punycode](punycode.html)
 * [Query Strings](querystring.html)

doc/api/policy.md

@@ -0,0 +1,104 @@
+# Policies
+
+<!--introduced_in=TODO-->
+<!-- type=misc -->
+
+> Stability: 1 - Experimental
+
+<!-- name=policy -->
+
+Node.js contains experimental support for creating policies on loading code.
+
+Policies are a security feature intended to allow guarantees
+about what code Node.js is able to load. The use of policies assumes
+safe practices for the policy files such as ensuring that policy
+files cannot be overwritten by the Node.js application by using
+file permissions.
+
+A best practice would be to ensure that the policy manifest is read only for
+the running Node.js application, and that the file cannot be changed
+by the running Node.js application in any way. A typical setup would be to
+create the policy file as a different user id than the one running Node.js
+and granting read permissions to the user id running Node.js.
+
+## Enabling
+
+<!-- type=misc -->
+
+The `--experimental-policy` flag can be used to enable features for policies
+when loading modules.
+
+Once this has been set, all modules must conform to a policy manifest file
+passed to the flag:
+
+```sh
+node --experimental-policy=policy.json app.js
+```
+
+The policy manifest will be used to enforce constraints on code loaded by
+Node.js.
+
+## Features
+
+### Error Behavior
+
+When a policy check fails, Node.js by default will throw an error.
+It is possible to change the error behavior to one of a few possibilities
+by defining an "onerror" field in a policy manifest. The following values are
+available to change the behavior:
+
+* `"exit"` - will exit the process immediately.
+    No cleanup code will be allowed to run.
+* `"log"` - will log the error at the site of the failure.
+* `"throw"` (default) - will throw a JS error at the site of the failure.
+
+```json
+{
+  "onerror": "log",
+  "resources": {
+    "./app/checked.js": {
+      "integrity": "sha384-SggXRQHwCG8g+DktYYzxkXRIkTiEYWBHqev0xnpCxYlqMBufKZHAHQM3/boDaI/0"
+    }
+  }
+}
+```
+
+### Integrity Checks
+
+Policy files must use integrity checks with Subresource Integrity strings
+compatible with the browser
+[integrity attribute](https://www.w3.org/TR/SRI/#the-integrity-attribute)
+associated with absolute URLs.
+
+When using `require()` all resources involved in loading are checked for
+integrity if a policy manifest has been specified. If a resource does not match
+the integrity listed in the manifest, an error will be thrown.
+
+An example policy file that would allow loading a file `checked.js`:
+
+```json
+{
+  "resources": {
+    "./app/checked.js": {
+      "integrity": "sha384-SggXRQHwCG8g+DktYYzxkXRIkTiEYWBHqev0xnpCxYlqMBufKZHAHQM3/boDaI/0"
+    }
+  }
+}
+```
+
+Each resource listed in the policy manifest can be of one the following
+formats to determine its location:
+
+1. A [relative url string][] to a resource from the manifest such as `./resource.js`, `../resource.js`, or `/resource.js`.
+2. A complete url string to a resource such as `file:///resource.js`.
+
+When loading resources the entire URL must match including search parameters
+and hash fragment. `./a.js?b` will not be used when attempting to load
+`./a.js` and vice versa.
+
+In order to generate integrity strings, a script such as
+`printf "sha384-$(cat checked.js | openssl dgst -sha384 -binary | base64)"`
+can be used.
+
+
+[relative url string]: https://url.spec.whatwg.org/#relative-url-with-fragment-string

doc/node.1

@@ -86,6 +86,9 @@ Requires Node.js to be built with
 .It Fl -experimental-modules
 Enable experimental ES module support and caching modules.
 .
+.It Fl -experimental-policy
+Use the specified file as a security policy.
+.
 .It Fl -experimental-repl-await
 Enable experimental top-level
 .Sy await

lib/internal/bootstrap/node.js

@@ -175,6 +175,28 @@ function startup() {
     mainThreadSetup.setupChildProcessIpcChannel();
   }
 
+  // TODO(joyeecheung): move this down further to get better snapshotting
+  if (getOptionValue('[has_experimental_policy]')) {
+    process.emitWarning('Policies are experimental.',
+                        'ExperimentalWarning');
+    const experimentalPolicy = getOptionValue('--experimental-policy');
+    const { pathToFileURL, URL } = NativeModule.require('url');
+    // URL here as it is slightly different parsing
+    // no bare specifiers for now
+    let manifestURL;
+    if (NativeModule.require('path').isAbsolute(experimentalPolicy)) {
+      manifestURL = new URL(`file:///${experimentalPolicy}`);
+    } else {
+      const cwdURL = pathToFileURL(process.cwd());
+      cwdURL.pathname += '/';
+      manifestURL = new URL(experimentalPolicy, cwdURL);
+    }
+    const fs = NativeModule.require('fs');
+    const src = fs.readFileSync(manifestURL, 'utf8');
+    NativeModule.require('internal/process/policy')
+      .setup(src, manifestURL.href);
+  }
+
   const browserGlobals = !process._noBrowserGlobals;
   if (browserGlobals) {
     setupGlobalTimeouts();

lib/internal/errors.js

@@ -818,6 +818,28 @@ E('ERR_IPC_CHANNEL_CLOSED', 'Channel closed', Error);
 E('ERR_IPC_DISCONNECTED', 'IPC channel is already disconnected', Error);
 E('ERR_IPC_ONE_PIPE', 'Child process can have only one IPC pipe', Error);
 E('ERR_IPC_SYNC_FORK', 'IPC cannot be used with synchronous forks', Error);
+E('ERR_MANIFEST_ASSERT_INTEGRITY',
+  (moduleURL, realIntegrities) => {
+    let msg = `The content of "${
+      moduleURL
+    }" does not match the expected integrity.`;
+    if (realIntegrities.size) {
+      const sri = [...realIntegrities.entries()].map(([alg, dgs]) => {
+        return `${alg}-${dgs}`;
+      }).join(' ');
+      msg += ` Integrities found are: ${sri}`;
+    } else {
+      msg += ' The resource was not found in the policy.';
+    }
+    return msg;
+  }, Error);
+E('ERR_MANIFEST_INTEGRITY_MISMATCH',
+  'Manifest resource %s has multiple entries but integrity lists do not match',
+  SyntaxError);
+E('ERR_MANIFEST_TDZ', 'Manifest initialization has not yet run', Error);
+E('ERR_MANIFEST_UNKNOWN_ONERROR',
+  'Manifest specified unknown error behavior "%s".',
+  SyntaxError);
 E('ERR_METHOD_NOT_IMPLEMENTED', 'The %s method is not implemented', Error);
 E('ERR_MISSING_ARGS',
   (...args) => {
@@ -889,6 +911,9 @@ E('ERR_SOCKET_BUFFER_SIZE',
 E('ERR_SOCKET_CANNOT_SEND', 'Unable to send data', Error);
 E('ERR_SOCKET_CLOSED', 'Socket is closed', Error);
 E('ERR_SOCKET_DGRAM_NOT_RUNNING', 'Not running', Error);
+E('ERR_SRI_PARSE',
+  'Subresource Integrity string %s had an unexpected at %d',
+  SyntaxError);
 E('ERR_STREAM_CANNOT_PIPE', 'Cannot pipe, not readable', Error);
 E('ERR_STREAM_DESTROYED', 'Cannot call %s after a stream was destroyed', Error);
 E('ERR_STREAM_NULL_VALUES', 'May not write null values to stream', TypeError);

lib/internal/modules/cjs/loader.js

@@ -22,8 +22,8 @@
 'use strict';
 
 const { NativeModule } = require('internal/bootstrap/loaders');
-const util = require('util');
 const { pathToFileURL } = require('internal/url');
+const util = require('util');
 const vm = require('vm');
 const assert = require('assert').ok;
 const fs = require('fs');
@@ -45,6 +45,9 @@ const { getOptionValue } = require('internal/options');
 const preserveSymlinks = getOptionValue('--preserve-symlinks');
 const preserveSymlinksMain = getOptionValue('--preserve-symlinks-main');
 const experimentalModules = getOptionValue('--experimental-modules');
+const manifest = getOptionValue('[has_experimental_policy]') ?
+  require('internal/process/policy').manifest :
+  null;
 
 const {
   ERR_INVALID_ARG_VALUE,
@@ -168,6 +171,11 @@ function readPackage(requestPath) {
     return false;
   }
 
+  if (manifest) {
+    const jsonURL = pathToFileURL(jsonPath);
+    manifest.assertIntegrity(jsonURL, json);
+  }
+
   try {
     return packageMainCache[requestPath] = JSON.parse(json).main;
   } catch (e) {
@@ -676,6 +684,10 @@ function normalizeReferrerURL(referrer) {
 // the file.
 // Returns exception, if any.
 Module.prototype._compile = function(content, filename) {
+  if (manifest) {
+    const moduleURL = pathToFileURL(filename);
+    manifest.assertIntegrity(moduleURL, content);
+  }
 
   content = stripShebang(content);
 
@@ -715,11 +727,14 @@ Module.prototype._compile = function(content, filename) {
   var depth = requireDepth;
   if (depth === 0) stat.cache = new Map();
   var result;
+  var exports = this.exports;
+  var thisValue = exports;
+  var module = this;
   if (inspectorWrapper) {
-    result = inspectorWrapper(compiledWrapper, this.exports, this.exports,
-                              require, this, filename, dirname);
+    result = inspectorWrapper(compiledWrapper, thisValue, exports,
+                              require, module, filename, dirname);
   } else {
-    result = compiledWrapper.call(this.exports, this.exports, require, this,
+    result = compiledWrapper.call(thisValue, exports, require, module,
                                   filename, dirname);
   }
   if (depth === 0) stat.cache = null;
@@ -736,7 +751,13 @@ Module._extensions['.js'] = function(module, filename) {
 
 // Native extension for .json
 Module._extensions['.json'] = function(module, filename) {
-  var content = fs.readFileSync(filename, 'utf8');
+  const content = fs.readFileSync(filename, 'utf8');
+
+  if (manifest) {
+    const moduleURL = pathToFileURL(filename);
+    manifest.assertIntegrity(moduleURL, content);
+  }
+
   try {
     module.exports = JSON.parse(stripBOM(content));
   } catch (err) {
@@ -748,6 +769,12 @@ Module._extensions['.json'] = function(module, filename) {
 
 // Native extension for .node
 Module._extensions['.node'] = function(module, filename) {
+  if (manifest) {
+    const content = fs.readFileSync(filename);
+    const moduleURL = pathToFileURL(filename);
+    manifest.assertIntegrity(moduleURL, content);
+  }
+  // be aware this doesn't use `content`
   return process.dlopen(module, path.toNamespacedPath(filename));
 };