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const config = require('./config')
const { v4: uuidv4 } = require('uuid')
const CspStrategy = {}
const defaultDirectives = {
defaultSrc: ['\'self\''],
scriptSrc: ['\'self\'', 'vimeo.com', 'https://gist.github.com', 'www.slideshare.net', '\'unsafe-eval\''],
// ^ TODO: Remove unsafe-eval - webpack script-loader issues https://github.com/hackmdio/codimd/issues/594
imgSrc: ['*'],
styleSrc: ['\'self\'', '\'unsafe-inline\'', 'https://github.githubassets.com'], // unsafe-inline is required for some libs, plus used in views
fontSrc: ['\'self\'', 'data:', 'https://public.slidesharecdn.com'],
objectSrc: ['*'], // Chrome PDF viewer treats PDFs as objects :/
mediaSrc: ['*'],
childSrc: ['*'],
connectSrc: ['*']
}
const cdnDirectives = {
scriptSrc: ['https://cdnjs.cloudflare.com', 'https://cdn.mathjax.org'],
styleSrc: ['https://cdnjs.cloudflare.com', 'https://fonts.googleapis.com'],
fontSrc: ['https://cdnjs.cloudflare.com', 'https://fonts.gstatic.com']
}
const disqusDirectives = {
scriptSrc: ['https://disqus.com', 'https://*.disqus.com', 'https://*.disquscdn.com'],
styleSrc: ['https://*.disquscdn.com'],
fontSrc: ['https://*.disquscdn.com']
}
const googleAnalyticsDirectives = {
scriptSrc: ['https://www.google-analytics.com']
}
const dropboxDirectives = {
scriptSrc: ['https://www.dropbox.com', '\'unsafe-inline\'']
}
CspStrategy.computeDirectives = function () {
const directives = {}
mergeDirectives(directives, config.csp.directives)
mergeDirectivesIf(config.csp.addDefaults, directives, defaultDirectives)
mergeDirectivesIf(config.useCDN, directives, cdnDirectives)
mergeDirectivesIf(config.csp.addDisqus, directives, disqusDirectives)
mergeDirectivesIf(config.csp.addGoogleAnalytics, directives, googleAnalyticsDirectives)
mergeDirectivesIf(config.dropbox.appKey, directives, dropboxDirectives)
if (!areAllInlineScriptsAllowed(directives)) {
addInlineScriptExceptions(directives)
}
addUpgradeUnsafeRequestsOptionTo(directives)
addReportURI(directives)
return directives
}
function mergeDirectives (existingDirectives, newDirectives) {
for (const propertyName in newDirectives) {
const newDirective = newDirectives[propertyName]
if (newDirective) {
const existingDirective = existingDirectives[propertyName] || []
existingDirectives[propertyName] = existingDirective.concat(newDirective)
}
}
}
function mergeDirectivesIf (condition, existingDirectives, newDirectives) {
if (condition) {
mergeDirectives(existingDirectives, newDirectives)
}
}
function areAllInlineScriptsAllowed (directives) {
return directives.scriptSrc.indexOf('\'unsafe-inline\'') !== -1
}
function addInlineScriptExceptions (directives) {
directives.scriptSrc.push(getCspNonce)
// TODO: This is the SHA-256 hash of the inline script in build/reveal.js/plugins/notes/notes.html
// Any more clean solution appreciated.
directives.scriptSrc.push('\'sha256-81acLZNZISnyGYZrSuoYhpzwDTTxi7vC1YM4uNxqWaM=\'')
}
function getCspNonce (req, res) {
return "'nonce-" + res.locals.nonce + "'"
}
function addUpgradeUnsafeRequestsOptionTo (directives) {
if (config.csp.upgradeInsecureRequests === 'auto' && config.useSSL) {
directives.upgradeInsecureRequests = []
} else if (config.csp.upgradeInsecureRequests === true) {
directives.upgradeInsecureRequests = []
}
}
function addReportURI (directives) {
if (config.csp.reportURI) {
directives.reportUri = config.csp.reportURI
}
}
CspStrategy.addNonceToLocals = function (req, res, next) {
res.locals.nonce = uuidv4()
next()
}
module.exports = CspStrategy
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