Refuse to bundle symbolic links in static assets

packages/rollup-plugin-webbundle/test/test.js

@@ -15,6 +15,8 @@
  */
 
 import test from 'ava';
+import * as fs from 'fs';
+import * as os from 'os';
 import * as path from 'path';
 import * as rollup from 'rollup';
 import crypto from 'crypto';
@@ -146,6 +148,71 @@ test('static', async (t) => {
   t.snapshot(parseWebBundle(output[keys[0]].source));
 });
 
+test('static with symbolic link throws error', async (t) => {
+  const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'wbn-rollup-symlink-'));
+  try {
+    const targetFile = path.join(tmpDir, 'target.txt');
+    fs.writeFileSync(targetFile, 'sensitive data');
+    const symlinkFile = path.join(tmpDir, 'symlink.txt');
+    fs.symlinkSync(targetFile, symlinkFile);
+
+    const bundle = await rollup.rollup({
+      input: 'fixtures/index.js',
+      plugins: [
+        webbundle({
+          baseURL: 'https://wbn.example.com/',
+          output: 'out.wbn',
+          static: { dir: tmpDir },
+        }),
+      ],
+    });
+
+    const error = await t.throwsAsync(
+      async () => {
+        await bundle.generate({ format: 'esm' });
+      },
+      { instanceOf: Error }
+    );
+    t.is(
+      error.message,
+      `Refusing to bundle symbolic link at ${symlinkFile}. Replace it with a regular file or directory.`
+    );
+  } finally {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  }
+});
+
+test('static with directory-symlink loop throws refusal error without ELOOP', async (t) => {
+  const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'wbn-rollup-loop-'));
+  try {
+    const loopLink = path.join(tmpDir, 'loop');
+    fs.symlinkSync('.', loopLink);
+
+    const bundle = await rollup.rollup({
+      input: 'fixtures/index.js',
+      plugins: [
+        webbundle({
+          output: 'out.wbn',
+          static: { dir: tmpDir },
+        }),
+      ],
+    });
+
+    const error = await t.throwsAsync(
+      async () => {
+        await bundle.generate({ format: 'esm' });
+      },
+      { instanceOf: Error }
+    );
+    t.is(
+      error.message,
+      `Refusing to bundle symbolic link at ${loopLink}. Replace it with a regular file or directory.`
+    );
+  } finally {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  }
+});
+
 test('relative', async (t) => {
   const bundle = await rollup.rollup({
     input: 'fixtures/index.js',

packages/shared/test/test.js

@@ -15,7 +15,12 @@
  */
 
 import test from 'ava';
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import { BundleBuilder } from 'wbn';
 import { getValidatedOptionsWithDefaults } from '../lib/types.js';
+import { addFilesRecursively } from '../lib/utils.js';
 import * as wbnSign from 'wbn-sign';
 
 const TEST_ED25519_PRIVATE_KEY = wbnSign.parsePemKey(
@@ -50,3 +55,92 @@ test('headerOverride - IWA with bad headers', async (t) => {
     }
   }
 });
+
+test('addFilesRecursively - refuses symbolic link to file', (t) => {
+  const tmpDir = fs.mkdtempSync(
+    path.join(os.tmpdir(), 'wbn-test-symlink-file-')
+  );
+  try {
+    const targetFile = path.join(tmpDir, 'target.txt');
+    fs.writeFileSync(targetFile, 'sensitive data');
+    const symlinkFile = path.join(tmpDir, 'symlink.txt');
+    fs.symlinkSync(targetFile, symlinkFile);
+
+    const builder = new BundleBuilder();
+    const error = t.throws(
+      () => {
+        addFilesRecursively(builder, 'https://example.com/', tmpDir, {
+          baseURL: 'https://example.com/',
+          output: 'out.wbn',
+        });
+      },
+      { instanceOf: Error }
+    );
+    t.is(
+      error.message,
+      `Refusing to bundle symbolic link at ${symlinkFile}. Replace it with a regular file or directory.`
+    );
+  } finally {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  }
+});
+
+test('addFilesRecursively - refuses symbolic link to directory', (t) => {
+  const tmpDir = fs.mkdtempSync(
+    path.join(os.tmpdir(), 'wbn-test-symlink-dir-')
+  );
+  try {
+    const targetDir = path.join(tmpDir, 'target-dir');
+    fs.mkdirSync(targetDir);
+    fs.writeFileSync(path.join(targetDir, 'inner.txt'), 'sensitive data');
+    const symlinkDir = path.join(tmpDir, 'symlink-dir');
+    fs.symlinkSync(targetDir, symlinkDir);
+
+    const builder = new BundleBuilder();
+    const error = t.throws(
+      () => {
+        addFilesRecursively(builder, 'https://example.com/', tmpDir, {
+          baseURL: 'https://example.com/',
+          output: 'out.wbn',
+        });
+      },
+      { instanceOf: Error }
+    );
+    t.is(
+      error.message,
+      `Refusing to bundle symbolic link at ${symlinkDir}. Replace it with a regular file or directory.`
+    );
+  } finally {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  }
+});
+
+test('addFilesRecursively - refuses root directory being a symbolic link', (t) => {
+  const tmpDir = fs.mkdtempSync(
+    path.join(os.tmpdir(), 'wbn-test-root-symlink-')
+  );
+  try {
+    const targetDir = path.join(tmpDir, 'target-dir');
+    fs.mkdirSync(targetDir);
+    fs.writeFileSync(path.join(targetDir, 'inner.txt'), 'some data');
+    const symlinkDir = path.join(tmpDir, 'symlink-root');
+    fs.symlinkSync(targetDir, symlinkDir);
+
+    const builder = new BundleBuilder();
+    const error = t.throws(
+      () => {
+        addFilesRecursively(builder, 'https://example.com/', symlinkDir, {
+          baseURL: 'https://example.com/',
+          output: 'out.wbn',
+        });
+      },
+      { instanceOf: Error }
+    );
+    t.is(
+      error.message,
+      `Refusing to bundle symbolic link at ${symlinkDir}. Replace it with a regular file or directory.`
+    );
+  } finally {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  }
+});

packages/shared/utils.ts

@@ -19,8 +19,8 @@ import * as path from 'path';
 import mime from 'mime';
 import { combineHeadersForUrl, BundleBuilder } from 'wbn';
 import { IntegrityBlockSigner } from 'wbn-sign';
-import { checkAndAddIwaHeaders } from './iwa-headers';
-import { ValidIbSignPluginOptions, ValidPluginOptions } from './types';
+import { checkAndAddIwaHeaders } from './iwa-headers.js';
+import { ValidIbSignPluginOptions, ValidPluginOptions } from './types.js';
 
 // If the file name is 'index.html', create an entry for both baseURL/dir/ and
 // baseURL/dir/index.html which redirects to the aforementioned. Otherwise just
@@ -84,13 +84,29 @@ export function addFilesRecursively(
   pluginOptions: ValidPluginOptions,
   recPath = ''
 ) {
+  if (recPath === '' && fs.lstatSync(dir).isSymbolicLink()) {
+    throw new Error(
+      `Refusing to bundle symbolic link at ${dir}. ` +
+        `Replace it with a regular file or directory.`
+    );
+  }
+
   const files = fs.readdirSync(dir);
   files.sort(); // Sort entries for reproducibility.
 
   for (const fileName of files) {
     const filePath = path.join(dir, fileName);
 
-    if (fs.statSync(filePath).isDirectory()) {
+    const stat = fs.lstatSync(filePath);
+    if (stat.isSymbolicLink()) {
+      // Refuse to follow symlinks so that files outside the static directory
+      // (credentials, SSH keys, etc.) cannot be pulled into the bundle.
+      throw new Error(
+        `Refusing to bundle symbolic link at ${filePath}. ` +
+          `Replace it with a regular file or directory.`
+      );
+    }
+    if (stat.isDirectory()) {
       addFilesRecursively(
         builder,
         baseURL,

packages/webbundle-webpack-plugin/test/test.js

@@ -20,6 +20,7 @@ import webpack from 'webpack';
 import MemoryFS from 'memory-fs';
 import url from 'url';
 import fs from 'fs';
+import * as os from 'os';
 import * as path from 'path';
 import * as wbn from 'wbn';
 import * as wbnSign from 'wbn-sign';
@@ -101,6 +102,34 @@ test('static', async (t) => {
   t.is(new TextDecoder('utf-8').decode(resp.body), html.toString());
 });
 
+test('static with symbolic link throws error', async (t) => {
+  const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'wbn-webpack-symlink-'));
+  try {
+    const targetFile = path.join(tmpDir, 'target.txt');
+    fs.writeFileSync(targetFile, 'sensitive data');
+    const symlinkFile = path.join(tmpDir, 'symlink.txt');
+    fs.symlinkSync(targetFile, symlinkFile);
+
+    const error = await t.throwsAsync(
+      async () => {
+        await run({
+          baseURL: 'https://example.com/',
+          static: { dir: tmpDir },
+          output: 'example.wbn',
+        });
+      },
+      { instanceOf: Error }
+    );
+    t.true(
+      error.message.includes(
+        `Refusing to bundle symbolic link at ${symlinkFile}. Replace it with a regular file or directory.`
+      )
+    );
+  } finally {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  }
+});
+
 test('relative', async (t) => {
   const { memfs } = await run({
     static: { dir: path.join(__dirname, 'fixtures', 'static') },