Hashing script in node.js

Question

i have an electron app, that will in the end load a script on html as

<script>require('../../lib/i18n-translate.js')</script>.

As electron (resp. chromium) complained about a missing Content-Security-Policy i wanted to add the csp with a hash programmatically, so when i build my app, it will automatically insert the hash and everybody is happy. Unfortunately i currently don't succeed to create the same hash as electron does:

• Electron shows me a hash on console, which makes the csp pass if i just copy it manually.
• Creating a hash on node.js with the following code, just creates me a different hash.
• I'm meanwhile relatively sure, that i need the base64 encoded output. Apart from that, i tried several encodings on readFile, with or without toString(), with trim()...
• My current assumption is, that the text/binary given to createHash.update() differs somehow from the one, that electron passes to its hashing.

Thus:

• Does anybody know, which text exactly is hashed by the browser to get the csp-hash?
• Or does anybody see my obvious fault on the hash-creation? ;)

Thank you in advance! :) Jonas

function getCspHash(file) {
  const fs = require('fs')
  const { createHash } = require('crypto')

  const hash = createHash('sha256').update(
    fs.readFileSync(file).toString()
  ).digest('base64')

  return str.concat(" 'sha256-", hash, "'")
}