docs/middleware/csp.js

import helmet from 'helmet'
import isArchivedVersion from '../lib/is-archived-version.js'
import versionSatisfiesRange from '../lib/version-satisfies-range.js'
// This module defines a Content Security Policy (CSP) to disallow
// inline scripts and content from untrusted sources.

const { contentSecurityPolicy } = helmet

const AZURE_STORAGE_URL = 'githubdocs.azureedge.net'

const isDev = process.env.NODE_ENV === 'development'

export default function csp(req, res, next) {
  const csp = {
    directives: {
      defaultSrc: ["'none'"],
      prefetchSrc: ["'self'"],

      connectSrc: [
        "'self'",
        // When doing local dev, especially in Safari, you need to add `ws:`
        // which NextJS uses for the hot module reloading.
        isDev && 'ws:',
      ].filter(Boolean),
      fontSrc: ["'self'", 'data:', AZURE_STORAGE_URL],
      imgSrc: [
        "'self'",
        'data:',
        'github.githubassets.com',
        AZURE_STORAGE_URL,
        'placehold.it',
        '*.githubusercontent.com',
        'github.com',
      ],
      objectSrc: ["'self'"],
      scriptSrc: [
        "'self'",
        // For use during development only! This allows us to use a performant webpack devtool setting (eval)
        // https://webpack.js.org/configuration/devtool/#devtool
        isDev && "'unsafe-eval'",
      ].filter(Boolean),
      frameSrc: [
        // exceptions for GraphQL Explorer
        'https://graphql.github.com/',
        isDev && 'http://localhost:3000', // development env
        'https://www.youtube-nocookie.com',
      ].filter(Boolean),
      styleSrc: ["'self'", "'unsafe-inline'"],
      childSrc: [
        "'self'", // exception for search in deprecated GHE versions
      ],
    },
  }

  const { requestedVersion } = isArchivedVersion(req)

  // Exception for deprecated Enterprise docs (Node.js era)
  if (
    versionSatisfiesRange(requestedVersion, '<=2.19') &&
    versionSatisfiesRange(requestedVersion, '>2.12')
  ) {
    csp.directives.scriptSrc.push(
      "'unsafe-eval'",
      "'unsafe-inline'",
      'http://www.google-analytics.com',
      'https://ssl.google-analytics.com'
    )
    csp.directives.connectSrc.push('https://www.google-analytics.com')
    csp.directives.imgSrc.push(
      'http://www.google-analytics.com',
      'https://ssl.google-analytics.com'
    )
  }

  // Exception for search in deprecated Enterprise docs <=2.12 (static site era)
  if (versionSatisfiesRange(requestedVersion, '<=2.12')) {
    csp.directives.scriptSrc.push("'unsafe-inline'")
  }

  return contentSecurityPolicy(csp)(req, res, next)
}