--policy-integrity

doc/api/policy.md

@@ -38,6 +38,15 @@ node --experimental-policy=policy.json app.js
 The policy manifest will be used to enforce constraints on code loaded by
 Node.js.
 
+In order to mitigate tampering with policy files on disk, an integrity for
+the policy file itself may be provided via `--policy-integrity`.
+This allows running `node` and asserting the policy file contents
+even if the file is changed on disk.
+
+```sh
+node --experimental-policy=policy.json --policy-integrity="sha384-SggXRQHwCG8g+DktYYzxkXRIkTiEYWBHqev0xnpCxYlqMBufKZHAHQM3/boDaI/0" app.js
+```
+
 ## Features
 
 ### Error Behavior

lib/internal/bootstrap/pre_execution.js

@@ -4,6 +4,7 @@ const { Object, SafeWeakMap } = primordials;
 
 const { getOptionValue } = require('internal/options');
 const { Buffer } = require('buffer');
+const { ERR_MANIFEST_ASSERT_INTEGRITY } = require('internal/errors').codes;
 
 function prepareMainThreadExecution(expandArgv1 = false) {
   // Patch the process object with legacy properties and normalizations
@@ -332,6 +333,32 @@ function initializePolicy() {
     }
     const fs = require('fs');
     const src = fs.readFileSync(manifestURL, 'utf8');
+    const experimentalPolicyIntegrity = getOptionValue('--policy-integrity');
+    if (experimentalPolicyIntegrity) {
+      const SRI = require('internal/policy/sri');
+      const { createHash, timingSafeEqual } = require('crypto');
+      const realIntegrities = new Map();
+      const integrityEntries = SRI.parse(experimentalPolicyIntegrity);
+      let foundMatch = false;
+      for (var i = 0; i < integrityEntries.length; i++) {
+        const {
+          algorithm,
+          value: expected
+        } = integrityEntries[i];
+        const hash = createHash(algorithm);
+        hash.update(src);
+        const digest = hash.digest();
+        if (digest.length === expected.length &&
+          timingSafeEqual(digest, expected)) {
+          foundMatch = true;
+          break;
+        }
+        realIntegrities.set(algorithm, digest.toString('base64'));
+      }
+      if (!foundMatch) {
+        throw new ERR_MANIFEST_ASSERT_INTEGRITY(manifestURL, realIntegrities);
+      }
+    }
     require('internal/process/policy')
       .setup(src, manifestURL.href);
   }

src/node_options.cc

@@ -121,6 +121,13 @@ void EnvironmentOptions::CheckOptions(std::vector<std::string>* errors) {
   if (!userland_loader.empty() && !experimental_modules) {
     errors->push_back("--loader requires --experimental-modules be enabled");
   }
+  if (has_policy_integrity_string && experimental_policy.empty()) {
+    errors->push_back("--policy-integrity requires "
+                      "--experimental-policy be enabled");
+  }
+  if (has_policy_integrity_string && experimental_policy_integrity.empty()) {
+    errors->push_back("--policy-integrity cannot be empty");
+  }
 
   if (!module_type.empty()) {
     if (!experimental_modules) {
@@ -313,6 +320,15 @@ EnvironmentOptionsParser::EnvironmentOptionsParser() {
             "security policy",
             &EnvironmentOptions::experimental_policy,
             kAllowedInEnvironment);
+  AddOption("[has_policy_integrity_string]",
+            "",
+            &EnvironmentOptions::has_policy_integrity_string);
+  AddOption("--policy-integrity",
+            "ensure the security policy contents match "
+            "the specified integrity",
+            &EnvironmentOptions::experimental_policy_integrity,
+            kAllowedInEnvironment);
+  Implies("--policy-integrity", "[has_policy_integrity_string]");
   AddOption("--experimental-repl-await",
             "experimental await keyword support in REPL",
             &EnvironmentOptions::experimental_repl_await,

src/node_options.h

@@ -105,6 +105,8 @@ class EnvironmentOptions : public Options {
   bool experimental_wasm_modules = false;
   std::string module_type;
   std::string experimental_policy;
+  std::string experimental_policy_integrity;
+  bool has_policy_integrity_string;
   bool experimental_repl_await = false;
   bool experimental_vm_modules = false;
   bool expose_internals = false;

test/fixtures/policy/dep-policy.json

@@ -0,0 +1,7 @@
+{
+  "resources": {
+    "./dep.js": {
+      "integrity": "sha512-7CMcc2oytFfMnGQaXbJk84gYWF2J7p/fmWPW7dsnJyniD+vgxtK9VAZ/22UxFOA4q5d27RoGLxSqNZ/nGCJkMw=="
+    }
+  }
+}

test/fixtures/policy/dep.js

@@ -0,0 +1,2 @@
+'use strict';
+module.exports = 'The Secret Ingredient';

test/parallel/test-policy-integrity-flag.js

@@ -0,0 +1,57 @@
+'use strict';
+
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+
+const fixtures = require('../common/fixtures');
+
+const assert = require('assert');
+const { spawnSync } = require('child_process');
+const fs = require('fs');
+const crypto = require('crypto');
+
+const depPolicy =fixtures.path('policy', 'dep-policy.json');
+const dep = fixtures.path('policy', 'dep.js');
+
+const emptyHash = crypto.createHash('sha512');
+emptyHash.update('');
+const emptySRI = `sha512-${emptyHash.digest('base64')}`;
+const policyHash = crypto.createHash('sha512');
+policyHash.update(fs.readFileSync(depPolicy));
+const depPolicySRI = `sha512-${policyHash.digest('base64')}`;
+{
+  const { status, stderr } = spawnSync(
+    process.execPath,
+    [
+      '--policy-integrity', emptySRI,
+      '--experimental-policy', depPolicy, dep,
+    ]
+  );
+
+  assert.ok(stderr.includes('ERR_MANIFEST_ASSERT_INTEGRITY'));
+  assert.strictEqual(status, 1);
+}
+{
+  const { status, stderr } = spawnSync(
+    process.execPath,
+    [
+      '--policy-integrity', '',
+      '--experimental-policy', depPolicy, dep,
+    ]
+  );
+
+  assert.ok(stderr.includes('--policy-integrity'));
+  assert.strictEqual(status, 9);
+}
+{
+  const { status } = spawnSync(
+    process.execPath,
+    [
+      '--policy-integrity', depPolicySRI,
+      '--experimental-policy', depPolicy, dep,
+    ]
+  );
+
+  assert.strictEqual(status, 0);
+}