Implement SRI support in importmap-rails

.github/workflows/ci.yml

@@ -37,6 +37,7 @@ jobs:
 
     env:
       BUNDLE_GEMFILE: gemfiles/rails_${{ matrix.rails-version }}_${{ matrix.assets-pipeline }}.gemfile
+      ASSETS_PIPELINE: ${{ matrix.assets-pipeline }}
 
     steps:
       - uses: actions/checkout@v4

Appraisals

@@ -17,7 +17,6 @@ end
 
 appraise "rails_7.0_propshaft" do
   gem "rails", github: "rails/rails", branch: "7-0-stable"
-  gem "propshaft"
   gem "sqlite3", "~> 1.4"
 end
 
@@ -29,7 +28,6 @@ end
 
 appraise "rails_7.1_propshaft" do
   gem "rails", "~> 7.1.0"
-  gem "propshaft"
 end
 
 appraise "rails_7.2_sprockets" do
@@ -40,7 +38,6 @@ end
 
 appraise "rails_7.2_propshaft" do
   gem "rails", "~> 7.2.0"
-  gem "propshaft"
 end
 
 appraise "rails_8.0_sprockets" do
@@ -51,7 +48,6 @@ end
 
 appraise "rails_8.0_propshaft" do
   gem "rails", "~> 8.0.0"
-  gem "propshaft"
 end
 
 appraise "rails_main_sprockets" do
@@ -62,5 +58,4 @@ end
 
 appraise "rails_main_propshaft" do
   gem "rails", github: "rails/rails", branch: "main"
-  gem "propshaft"
 end

Gemfile

@@ -5,7 +5,7 @@ git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 gemspec
 
 gem "rails"
-gem "propshaft"
+gem "propshaft", ">= 1.2.0"
 
 gem "sqlite3"
 

Gemfile.lock

@@ -105,13 +105,13 @@ GEM
     crass (1.0.6)
     date (3.4.1)
     drb (2.2.3)
-    erb (5.0.1)
+    erb (5.0.2)
     erubi (1.13.1)
     globalid (1.2.1)
       activesupport (>= 6.1)
     i18n (1.14.7)
       concurrent-ruby (~> 1.0)
-    io-console (0.8.0)
+    io-console (0.8.1)
     irb (1.15.2)
       pp (>= 0.6.0)
       rdoc (>= 4.0.0)
@@ -150,11 +150,10 @@ GEM
     pp (0.6.2)
       prettyprint
     prettyprint (0.2.0)
-    propshaft (1.1.0)
+    propshaft (1.2.0)
       actionpack (>= 7.0.0)
       activesupport (>= 7.0.0)
       rack
-      railties (>= 7.0.0)
     psych (5.2.6)
       date
       stringio
@@ -257,7 +256,7 @@ DEPENDENCIES
   byebug
   capybara
   importmap-rails!
-  propshaft
+  propshaft (>= 1.2.0)
   rails
   rexml
   selenium-webdriver

README.md

@@ -44,7 +44,7 @@ import React from "./node_modules/react"
 import React from "https://ga.jspm.io/npm:[email protected]/index.js"
 ```
 
-Importmap-rails provides a clean API for mapping "bare module specifiers" like `"react"` 
+Importmap-rails provides a clean API for mapping "bare module specifiers" like `"react"`
 to 1 of the 3 viable ways of loading ES Module javascript packages.
 
 For example:
@@ -54,11 +54,11 @@ For example:
 pin "react", to: "https://ga.jspm.io/npm:[email protected]/index.js"
 ```
 
-means "everytime you see `import React from "react"` 
+means "every time you see `import React from "react"`
 change it to `import React from "https://ga.jspm.io/npm:[email protected]/index.js"`"
 
 ```js
-import React from "react" 
+import React from "react"
 // => import React from "https://ga.jspm.io/npm:[email protected]/index.js"
 ```
 
@@ -79,10 +79,15 @@ If you want to import local js module files from `app/javascript/src` or other s
 ```rb
 # config/importmap.rb
 pin_all_from 'app/javascript/src', under: 'src', to: 'src'
+
+# With automatic integrity calculation for enhanced security
+pin_all_from 'app/javascript/controllers', under: 'controllers', integrity: true
 ```
 
 The `:to` parameter is only required if you want to change the destination logical import name. If you drop the :to option, you must place the :under option directly after the first parameter.
 
+The `integrity: true` option automatically calculates integrity hashes for all files in the directory, providing security benefits without manual hash management.
+
 Allows you to:
 
 ```js
@@ -131,6 +136,137 @@ If you later wish to remove a downloaded pin:
 Unpinning and removing "react"
 ```
 
+## Subresource Integrity (SRI)
+
+For enhanced security, importmap-rails automatically includes [Subresource Integrity (SRI)](https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity) hashes by default when pinning packages. This ensures that JavaScript files loaded from CDNs haven't been tampered with.
+
+### Default behavior with integrity
+
+When you pin a package, integrity hashes are automatically included:
+
+```bash
+./bin/importmap pin lodash
+Pinning "lodash" to vendor/javascript/lodash.js via download from https://ga.jspm.io/npm:[email protected]/lodash.js
+  Using integrity: sha384-PkIkha4kVPRlGtFantHjuv+Y9mRefUHpLFQbgOYUjzy247kvi16kLR7wWnsAmqZF
+```
+
+This generates a pin in your `config/importmap.rb` with the integrity hash:
+
+```ruby
+pin "lodash", integrity: "sha384-PkIkha4kVPRlGtFantHjuv+Y9mRefUHpLFQbgOYUjzy247kvi16kLR7wWnsAmqZF" # @4.17.21
+```
+
+### Opting out of integrity
+
+If you need to disable integrity checking (not recommended for security reasons), you can use the `--no-integrity` flag:
+
+```bash
+./bin/importmap pin lodash --no-integrity
+Pinning "lodash" to vendor/javascript/lodash.js via download from https://ga.jspm.io/npm:[email protected]/lodash.js
+```
+
+This generates a pin without integrity:
+
+```ruby
+pin "lodash" # @4.17.21
+```
+
+### Adding integrity to existing pins
+
+If you have existing pins without integrity hashes, you can add them using the `integrity` command:
+
+```bash
+# Add integrity to specific packages
+./bin/importmap integrity lodash react
+
+# Add integrity to all pinned packages
+./bin/importmap integrity
+
+# Update your importmap.rb file with integrity hashes
+./bin/importmap integrity --update
+```
+
+### Automatic integrity for local assets
+
+For local assets served by the Rails asset pipeline (like those created with `pin` or `pin_all_from`), you can use `integrity: true` to automatically calculate integrity hashes from the compiled assets:
+
+```ruby
+# config/importmap.rb
+
+# Automatically calculate integrity from asset pipeline
+pin "application", integrity: true
+pin "admin", to: "admin.js", integrity: true
+
+# Works with pin_all_from too
+pin_all_from "app/javascript/controllers", under: "controllers", integrity: true
+pin_all_from "app/javascript/lib", under: "lib", integrity: true
+
+# Mixed usage
+pin "local_module", integrity: true              # Auto-calculated
+pin "cdn_package", integrity: "sha384-abc123..." # Pre-calculated
+pin "no_integrity_package"                       # No integrity (default)
+```
+
+This is particularly useful for:
+* **Local JavaScript files** managed by your Rails asset pipeline
+* **Bulk operations** with `pin_all_from` where calculating hashes manually would be tedious
+* **Development workflow** where asset contents change frequently
+
+The `integrity: true` option:
+* Uses the Rails asset pipeline's built-in integrity calculation
+* Works with both Sprockets and Propshaft
+* Automatically updates when assets are recompiled
+* Gracefully handles missing assets (returns `nil` for non-existent files)
+
+**Example output with `integrity: true`:**
+```json
+{
+  "imports": {
+    "application": "/assets/application-abc123.js",
+    "controllers/hello_controller": "/assets/controllers/hello_controller-def456.js"
+  },
+  "integrity": {
+    "/assets/application-abc123.js": "sha256-xyz789...",
+    "/assets/controllers/hello_controller-def456.js": "sha256-uvw012..."
+  }
+}
+```
+
+### How integrity works
+
+The integrity hashes are automatically included in your import map and module preload tags:
+
+**Import map JSON:**
+```json
+{
+  "imports": {
+    "lodash": "https://ga.jspm.io/npm:[email protected]/lodash.js"
+  },
+  "integrity": {
+    "https://ga.jspm.io/npm:[email protected]/lodash.js": "sha384-PkIkha4kVPRlGtFantHjuv+Y9mRefUHpLFQbgOYUjzy247kvi16kLR7wWnsAmqZF"
+  }
+}
+```
+
+**Module preload tags:**
+```html
+<link rel="modulepreload" href="https://ga.jspm.io/npm:[email protected]/lodash.js" integrity="sha384-PkIkha4kVPRlGtFantHjuv+Y9mRefUHpLFQbgOYUjzy247kvi16kLR7wWnsAmqZF">
+```
+
+Modern browsers will automatically validate these integrity hashes when loading the JavaScript modules, ensuring the files haven't been modified.
+
+### Redownloading packages with integrity
+
+The `pristine` command also includes integrity by default:
+
+```bash
+# Redownload all packages with integrity (default)
+./bin/importmap pristine
+
+# Redownload packages without integrity
+./bin/importmap pristine --no-integrity
+```
+
 ## Preloading pinned modules
 
 To avoid the waterfall effect where the browser has to load one file after another before it can get to the deepest nested import, importmap-rails uses [modulepreload links](https://developers.google.com/web/updates/2017/12/modulepreload) by default. If you don't want to preload a dependency, because you want to load it on-demand for efficiency, append `preload: false` to the pin.
@@ -217,7 +353,7 @@ Pin your js file:
 pin "checkout", preload: false
 ```
 
-Import your module on the specific page. Note: you'll likely want to use a `content_for` block on the specifc page/partial, then yield it in your layout.
+Import your module on the specific page. Note: you'll likely want to use a `content_for` block on the specific page/partial, then yield it in your layout.
 
 ```erb
 <% content_for :head do %>

app/helpers/importmap/importmap_tags_helper.rb

@@ -25,13 +25,23 @@ def javascript_import_module_tag(*module_names)
   # (defaults to Rails.application.importmap), such that they'll be fetched
   # in advance by browsers supporting this link type (https://caniuse.com/?search=modulepreload).
   def javascript_importmap_module_preload_tags(importmap = Rails.application.importmap, entry_point: "application")
-    javascript_module_preload_tag(*importmap.preloaded_module_paths(resolver: self, entry_point:, cache_key: entry_point))
+    packages = importmap.preloaded_module_packages(resolver: self, entry_point:, cache_key: entry_point)
+
+    _generate_preload_tags(packages) { |path, package| [path, { integrity: package.integrity }] }
   end
 
   # Link tag(s) for preloading the JavaScript module residing in `*paths`. Will return one link tag per path element.
   def javascript_module_preload_tag(*paths)
-    safe_join(Array(paths).collect { |path|
-      tag.link rel: "modulepreload", href: path, nonce: request&.content_security_policy_nonce
-    }, "\n")
+    _generate_preload_tags(paths) { |path| [path, {}] }
   end
+
+  private
+    def _generate_preload_tags(items)
+      content_security_policy_nonce = request&.content_security_policy_nonce
+
+      safe_join(Array(items).collect { |item|
+        path, options = yield(item)
+        tag.link rel: "modulepreload", href: path, nonce: content_security_policy_nonce, **options
+      }, "\n")
+    end
 end

gemfiles/rails_7.0_propshaft.gemfile

@@ -3,7 +3,7 @@
 source "https://rubygems.org"
 
 gem "rails", branch: "7-0-stable", git: "https://github.com/rails/rails.git"
-gem "propshaft"
+gem "propshaft", ">= 1.2.0"
 gem "sqlite3", "~> 1.4"
 
 group :development do

gemfiles/rails_7.1_propshaft.gemfile

@@ -3,7 +3,7 @@
 source "https://rubygems.org"
 
 gem "rails", "~> 7.1.0"
-gem "propshaft"
+gem "propshaft", ">= 1.2.0"
 gem "sqlite3"
 
 group :development do

gemfiles/rails_7.2_propshaft.gemfile

@@ -3,7 +3,7 @@
 source "https://rubygems.org"
 
 gem "rails", "~> 7.2.0"
-gem "propshaft"
+gem "propshaft", ">= 1.2.0"
 gem "sqlite3"
 
 group :development do

gemfiles/rails_8.0_propshaft.gemfile

@@ -3,7 +3,7 @@
 source "https://rubygems.org"
 
 gem "rails", "~> 8.0.0"
-gem "propshaft"
+gem "propshaft", ">= 1.2.0"
 gem "sqlite3"
 
 group :development do

gemfiles/rails_main_propshaft.gemfile

@@ -3,7 +3,7 @@
 source "https://rubygems.org"
 
 gem "rails", branch: "main", git: "https://github.com/rails/rails.git"
-gem "propshaft"
+gem "propshaft", ">= 1.2.0"
 gem "sqlite3"
 
 group :development do