Gulp Sub-Resource Integrity Hash plugin

A gulp plugin for adding Subresource Integrity (SRI) hashes to HTML files when referencing external assets.

Adds Subresource Integrity (SRI) hashes to HTML files.

It does so, by parsing the contents of passed in HTML files with cheerio, looking for <link rel=stylesheet href=URL> and <script src=URL> DOM-nodes, computing checksums for found referenced files, and adding integrity=<HASH> attributes in-place to respective DOM-nodes.

Inspiration for this plugin came from working with static site generators.

For an alternative approach, have a look at the gulp-sri plugin.

Installation

Install package with NPM and add it to your development dependencies:

npm install gulp-sri-hash --save-dev

Usage

var sriHash = require('gulp-sri-hash');

gulp.task('sri', function() {
  return gulp.src('./**/*.html')
    // do not modify contents of any referenced css- and js-files after this task...
    .pipe(sriHash())
    // ... manipulating html files further, is perfectly fine
    .pipe(gulp.dest('./dist/'));
});

This will look for css and js file references contained in all html-files, calculate SRI-hashes for those files, and add integrity=<HASH> attributes for those references.

Referenced css- and js-files must be accessible from the local filesystem. In order to calculate correct hashes, style and script files should not be modified any further by build steps running later.

Line Endings:

Content hashing is sensitive to differences in line-endings. On Windows, the default is CRLF, whereas (all?) other Operating Systems default to LF. You’re good, as long the files use the same end-of-line sequence locally as well as on the server that delivers those asset files. On the other hand, a change of line-endings after content hashing will cause a file checksum mismatch.

API

algo (optional)

• Type: String
• Default: sha384
• Since: v1.0.0

Select hashing algorithm. Supported algorithms: sha256, sha384, and sha512.

prefix (optional)

• Type: String
• Default: ''
• Since: v1.1.0

Strips string from beginning of referenced URI in HTML files. Useful if references do not match directory structure or already contain CDN hostname.

selector (optional)

• Type: String
• Default: link[href][rel=stylesheet]:not([integrity]), script[src]:not([integrity])
• Since: v1.1.0

Only look for nodes matching this custom (jQuery-style) selector.

relative (optional)

• Type: Boolean
• Default: false
• Since: v1.2.0

Controls whether referenced files should be resolved relative to a base folder, or relative to the location of the HTML file.

Inspired by https://github.com/macedigital/gulp-sri-hash/pull/1.

Example

Following snippet shows all options in action:

  // ...
  .pipe(sriHash({
    algo: 'sha512',         // use strong hashing
    prefix: '/assets',      // no trailing slash
    selector: 'link[href]', // limit selector
    relative: true          // assets reside relative to html file
  }))
  // ...

Changelog

Since v1.3.0:

A crossorigin=anonymous attribute will be added to all updated DOM nodes, unless the attribute has been already been set to value use-credentials. In the latter case the crossorigin attribute is left unchanged.

Since v1.4.0:

Querystring-like components in file paths are ignored when resolving local files. As an example, the given string /folder/style.css?v=somehash will resolve to local file /folder/style.css.

LICENSE

MIT License