Run jest tests in a simulated disallowed environment

Author: legrego

src/platform/packages/shared/kbn-test/jest-preset.js

@@ -76,6 +76,7 @@ module.exports = {
 
   // A list of paths to modules that run some code to configure or set up the testing framework before each test
   setupFilesAfterEnv: [
+    '<rootDir>/src/platform/packages/shared/kbn-test/src/jest/setup/disallow_code_generation.js',
     '<rootDir>/src/platform/packages/shared/kbn-test/src/jest/setup/setup_test.js',
     '<rootDir>/src/platform/packages/shared/kbn-test/src/jest/setup/mocks.moment_timezone.js',
     '<rootDir>/src/platform/packages/shared/kbn-test/src/jest/setup/mocks.eui.js',

src/platform/packages/shared/kbn-test/jest_integration_node/jest-preset.js

@@ -28,6 +28,7 @@ module.exports = {
     '[/\\\\]node_modules(?![\\/\\\\](langchain|langsmith|@langchain|zod/v4))/dist/util/[/\\\\].+\\.js$',
   ],
   setupFilesAfterEnv: [
+    '<rootDir>/src/platform/packages/shared/kbn-test/src/jest/setup/disallow_code_generation.js',
     '<rootDir>/src/platform/packages/shared/kbn-test/src/jest/setup/after_env.integration.js',
     '<rootDir>/src/platform/packages/shared/kbn-test/src/jest/setup/mocks.moment_timezone.js',
   ],

src/platform/packages/shared/kbn-test/src/jest/setup/disallow_code_generation.js

@@ -0,0 +1,72 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the "Elastic License
+ * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
+ * Public License v 1"; you may not use this file except in compliance with, at
+ * your election, the "Elastic License 2.0", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+/*
+ * Disallow runtime code generation from strings in Jest tests.
+ *
+ * In production and dev mode, Kibana runs with the V8 flag
+ * --disallow-code-generation-from-strings, which causes eval() and
+ * new Function(string) to throw:
+ *
+ *   "Code generation from strings disallowed for this context"
+ *
+ * We cannot use that V8 flag for Jest because Jest's own dependencies
+ * (tmpl -> makeerror -> walker) call new Function() during startup.
+ * Instead, this setup file replaces eval and Function with versions that
+ * throw the same EvalError, scoped to the test sandbox only.
+ *
+ * Jest's own mock system (jest-mock) uses new Function() to create mock
+ * functions that preserve the original function's name. These calls are
+ * exempted by checking the call stack for known Jest internal callers.
+ *
+ * If your test is failing with this error, it means the code under test
+ * uses eval() or new Function() — which would also fail in production.
+ * Fix the underlying code rather than removing this restriction.
+ *
+ * See: packages/kbn-cli-dev-mode/src/using_server_process.ts  (dev flag)
+ *      src/dev/build/tasks/bin/scripts/kibana                  (prod flag)
+ *      src/platform/packages/shared/kbn-security-hardening/    (hardening package)
+ */
+
+const ERROR_MESSAGE = 'Code generation from strings disallowed for this context';
+
+const ALLOWED_CALLERS = [/jest-mock/, /jest-runtime/, /jest-environment/];
+
+function isCallerAllowed() {
+  const stack = new Error().stack || '';
+  return ALLOWED_CALLERS.some((pattern) => pattern.test(stack));
+}
+
+// eslint-disable-next-line no-eval -- intentionally replacing eval to block code generation
+global.eval = function () {
+  throw new EvalError(ERROR_MESSAGE);
+};
+
+const OriginalFunction = global.Function;
+const FunctionProxy = new Proxy(OriginalFunction, {
+  apply(target, thisArg, args) {
+    if (isCallerAllowed()) {
+      return Reflect.apply(target, thisArg, args);
+    }
+    throw new EvalError(ERROR_MESSAGE);
+  },
+  construct(target, args, newTarget) {
+    if (isCallerAllowed()) {
+      return Reflect.construct(target, args, newTarget);
+    }
+    throw new EvalError(ERROR_MESSAGE);
+  },
+});
+
+Object.defineProperty(FunctionProxy, 'prototype', {
+  value: OriginalFunction.prototype,
+  writable: false,
+});
+
+global.Function = FunctionProxy;

src/platform/packages/shared/kbn-test/src/jest/setup/disallow_code_generation.test.ts

@@ -0,0 +1,38 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the "Elastic License
+ * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
+ * Public License v 1"; you may not use this file except in compliance with, at
+ * your election, the "Elastic License 2.0", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+const ERROR_MESSAGE = 'Code generation from strings disallowed for this context';
+
+describe('disallow_code_generation setup', () => {
+  it('blocks eval()', () => {
+    // eslint-disable-next-line no-eval -- verifying that eval is blocked
+    expect(() => eval('1+1')).toThrow(EvalError);
+    // eslint-disable-next-line no-eval -- verifying that eval is blocked
+    expect(() => eval('1+1')).toThrow(ERROR_MESSAGE);
+  });
+
+  it('blocks new Function()', () => {
+    // eslint-disable-next-line no-new-func -- verifying that Function constructor is blocked
+    expect(() => new Function('return 1+1')).toThrow(EvalError);
+    // eslint-disable-next-line no-new-func -- verifying that Function constructor is blocked
+    expect(() => new Function('return 1+1')).toThrow(ERROR_MESSAGE);
+  });
+
+  it('blocks Function() called without new', () => {
+    // eslint-disable-next-line no-new-func -- verifying that Function() is blocked
+    expect(() => Function('return 1+1')).toThrow(EvalError);
+    // eslint-disable-next-line no-new-func -- verifying that Function() is blocked
+    expect(() => Function('return 1+1')).toThrow(ERROR_MESSAGE);
+  });
+
+  it('preserves Function.prototype so instanceof still works', () => {
+    const fn = () => {};
+    expect(fn instanceof Function).toBe(true);
+  });
+});