feat(core): use virtual file system for SRI

playground/nuxt.config.ts

@@ -2,6 +2,7 @@ import { defineNuxtConfig } from 'nuxt/config'
 
 export default defineNuxtConfig({
   modules: ['../src/module'],
+  devtools: { enabled: true },
 
   // Per route configuration
   routeRules: {
@@ -46,6 +47,7 @@ export default defineNuxtConfig({
   // Global configuration
   security: {
     headers: {
+      crossOriginEmbedderPolicy: false,
       xXSSProtection: '0'
     },
     rateLimiter: {

src/module.ts

@@ -195,8 +195,15 @@ export default defineNuxtModule<ModuleOptions>({
     // Import composables
     addImportsDir(resolver.resolve('./runtime/composables'))
 
-    // Calculates SRI hashes at build time
-    nuxt.hook('nitro:build:before', hashBundledAssets)
+    // Record SRI Hashes in the Virtual File System at build time
+    let sriHashes: Record<string, string> = {}
+    nuxt.options.nitro.virtual = defu(
+      { '#sri-hashes': () => `export default ${JSON.stringify(sriHashes)}` },
+      nuxt.options.nitro.virtual
+    )
+    nuxt.hook('nitro:build:before', async(nitro) => {
+      sriHashes = await hashBundledAssets(nitro)
+    })
   }
 })
 

src/runtime/nitro/plugins/50-subresourceIntegrity.ts

@@ -1,29 +1,16 @@
-import { useStorage, defineNitroPlugin } from '#imports'
+import { defineNitroPlugin } from '#imports'
 import { resolveSecurityRules } from '../utils'
-
+//@ts-expect-error : we are importing from the virtual file system
+import sriHashes from '#sri-hashes'
 
 export default defineNitroPlugin((nitroApp) => {
-  nitroApp.hooks.hook('render:html', async(html, { event }) => {
+  nitroApp.hooks.hook('render:html', (html, { event }) => {
     // Exit if SRI not enabled for this route
     const rules = resolveSecurityRules(event)
     if (!rules.enabled || !rules.sri) {
       return
     }
 
-    // Retrieve the sriHases that we computed at build time
-    //
-    // - If we are in a pre-rendering step of nuxi generate
-    //   Then the /integrity directory does not exist in server assets
-    //   But it is still in the .nuxt build directory
-    //
-    // - Conversely, if we are in a standalone SSR server pre-built by nuxi build
-    //   Then we don't have a .nuxt build directory anymore
-    //   But we did save the /integrity directory into the server assets    
-    const prerendering = !!import.meta.prerender
-    const storageBase = prerendering ? 'build' : 'assets'   
-    const sriHashes = await useStorage(storageBase).getItem<Record<string, string>>('integrity:sriHashes.json') || {}
-
-
     // Scan all relevant sections of the NuxtRenderHtmlContext
     // Note: integrity can only be set on scripts and on links with rel preload, modulepreload and stylesheet
     // However the SRI standard provides that other elements may be added to that list in the future

src/runtime/utils/hashes.ts

@@ -1,6 +1,6 @@
 import { createHash } from 'node:crypto'
 import { existsSync } from 'node:fs'
-import { readdir, readFile, writeFile, mkdir } from 'node:fs/promises'
+import { readdir, readFile } from 'node:fs/promises'
 import type { Nitro } from 'nitropack'
 import { join } from 'pathe'
 
@@ -47,18 +47,7 @@ export async function hashBundledAssets(nitro: Nitro) {
       }
     }
   }
-
-  // Save hashes in a /integrity directory within the .nuxt build for later use with SSG
-  const buildDir = nitro.options.buildDir
-  const integrityDir = join(buildDir, 'integrity')
-  if (!existsSync(integrityDir)) {
-    await mkdir(integrityDir)
-  }
-  const hashFilePath = join(integrityDir, 'sriHashes.json')
-  await writeFile(hashFilePath, JSON.stringify(sriHashes))
-
-  // Mount the /integrity directory into server assets for later use with SSR
-  nitro.options.serverAssets.push({ dir: integrityDir, baseName: 'integrity' })
+  return sriHashes
 }
 
 export function generateHash (content: Buffer | string, hashAlgorithm: string) {