grunt-sri

This tool generates a JSON manifest of file hashes & sub-resource integrity data.

Install

npm install --save-dev grunt-sri

Usage

Add the following to your Gruntfile.js:

module.exports = function (grunt) {
    "use strict";
 
    grunt.loadNpmTasks("grunt-sri");
 
    grunt.initConfig({
        "sri": {
 
            // Use the default settings for *everything* in ./public/css
            "bobsDefaultTask": {
                "src": [
                    "public/**/*.css"
                ]
            },
 
            // Create a second manifest with custom settings
            "janesCustomTask": {
                "options": {
                    "algorithms": ["sha256"],
                    "dest": "./public/sri-directives.json",
                    "targetProp": "payload"
                },
                "files": [
                    {
                        src: "public/css/example.css",
                        type: "text/css",
                        id: "cssfile1"
                    },
                    {
                        src: "public/css/other.css"
                    }
                ]
            }
 
        }
 
    });
 
    grunt.registerTask("default", ["sri"]);
};

Run the command grunt. The manifest file will be created.

Options

• String dest: Target JSON file.
  Default "./payload.json"
• Boolean merge: Merge results with existing JSON file.
  Default false (overwrite)
• Array algorithms: List of desired hash algorithms.
  Default ["sha256", "sha512"]
• String targetProp: Target JS object property name.
  Default null
• Boolean pretty: Stringify the JSON output in a pretty format.
  Default false

Manifest

Metadata is stored in JSON format.

• The default manifest dest is ./payload.json.
• File paths are relative to the CWD of Grunt.
  This should be the project root.
• File identifiers are prefixed with the "@" symbol.
  If no ID is specified, the path will be used.

Example:

{
    "@cssfile1": {
        "path": "public/css/example.css",
        "type": "text/css",
        "integrity": "type:text/css sha256-XXXX sha512-XXXXXXXX",
        "hashes": {
            "sha256": "XXXX",
            "sha512": "XXXXXXXX"
        }
    }
}

Implementation

Data from the manifest can be loaded into markup. Use the integrity property for SRI integrity attributes, a hash from hashes as a URL parameter for client-side caching, etc.

PHP

// In production, consider compiling JSON to PHP assoc arrays
$payload = json_decode(file_get_contents("./payload.json"), true);
$sri = function (id) {
    return $payload["payload"][id];
}
 
$element = "<link
    href='/style.css?cache={ sri("@cssfile1")["hashes"]["sha256"] }'
    integrity='{ $sri("@cssfile1")["integrity"] }'
    rel='stylesheet'>";

JavaScript

Note: Node apps should use subresource or handlebars-helper-sri, which don't require a build step.

// ES6
var payload = require("./payload.json");
var sri = (id) => payload.payload[id];
 
var element = `<link
    href='/style.css?cache=${ sri("@cssfile1").hashes.sha256 }'
    integrity='${ sri("@cssfile1").integrity }'
    rel='stylesheet'>`;

SemVer

This tool follows SemVer from v0.1.0, as SRI is now a W3C recommendation.

Changes to the V1 SRI spec will be tracked with minor releases.