helmet-csp/index.cjs

Content Security Policy middleware

"use strict"

Object.defineProperties(exports, {__esModule: {value: true}, [Symbol.toStringTag]: {value: "Module"}})

const dangerouslyDisableDefaultSrc = Symbol("dangerouslyDisableDefaultSrc")
const DEFAULT_DIRECTIVES = {
	"default-src": ["'self'"],
	"base-uri": ["'self'"],
	"font-src": ["'self'", "https:", "data:"],
	"form-action": ["'self'"],
	"frame-ancestors": ["'self'"],
	"img-src": ["'self'", "data:"],
	"object-src": ["'none'"],
	"script-src": ["'self'"],
	"script-src-attr": ["'none'"],
	"style-src": ["'self'", "https:", "'unsafe-inline'"],
	"upgrade-insecure-requests": []
}
const SHOULD_BE_QUOTED = new Set(["none", "self", "strict-dynamic", "report-sample", "inline-speculation-rules", "unsafe-inline", "unsafe-eval", "unsafe-hashes", "wasm-unsafe-eval"])
const getDefaultDirectives = () => Object.assign({}, DEFAULT_DIRECTIVES)
const dashify = str => str.replace(/[A-Z]/g, capitalLetter => "-" + capitalLetter.toLowerCase())
const isDirectiveValueInvalid = directiveValue => /;|,/.test(directiveValue)
const shouldDirectiveValueEntryBeQuoted = directiveValueEntry => SHOULD_BE_QUOTED.has(directiveValueEntry) || directiveValueEntry.startsWith("nonce-") || directiveValueEntry.startsWith("sha256-") || directiveValueEntry.startsWith("sha384-") || directiveValueEntry.startsWith("sha512-")
const warnIfDirectiveValueEntryShouldBeQuoted = value => {
	if (shouldDirectiveValueEntryBeQuoted(value)) {
		console.warn(`Content-Security-Policy got directive value \`${value}\` which should be single-quoted and changed to \`'${value}'\`. This will be an error in future versions of Helmet.`)
	}
}
const has = (obj, key) => Object.prototype.hasOwnProperty.call(obj, key)
function normalizeDirectives(options) {
	const defaultDirectives = getDefaultDirectives()
	const {useDefaults = true, directives: rawDirectives = defaultDirectives} = options
	const result = new Map()
	const directiveNamesSeen = new Set()
	const directivesExplicitlyDisabled = new Set()
	for (const rawDirectiveName in rawDirectives) {
		if (!has(rawDirectives, rawDirectiveName)) {
			continue
		}
		if (rawDirectiveName.length === 0 || /[^a-zA-Z0-9-]/.test(rawDirectiveName)) {
			throw new Error(`Content-Security-Policy received an invalid directive name ${JSON.stringify(rawDirectiveName)}`)
		}
		const directiveName = dashify(rawDirectiveName)
		if (directiveNamesSeen.has(directiveName)) {
			throw new Error(`Content-Security-Policy received a duplicate directive ${JSON.stringify(directiveName)}`)
		}
		directiveNamesSeen.add(directiveName)
		const rawDirectiveValue = rawDirectives[rawDirectiveName]
		let directiveValue
		if (rawDirectiveValue === null) {
			if (directiveName === "default-src") {
				throw new Error("Content-Security-Policy needs a default-src but it was set to `null`. If you really want to disable it, set it to `contentSecurityPolicy.dangerouslyDisableDefaultSrc`.")
			}
			directivesExplicitlyDisabled.add(directiveName)
			continue
		} else if (typeof rawDirectiveValue === "string") {
			directiveValue = [rawDirectiveValue]
		} else if (!rawDirectiveValue) {
			throw new Error(`Content-Security-Policy received an invalid directive value for ${JSON.stringify(directiveName)}`)
		} else if (rawDirectiveValue === dangerouslyDisableDefaultSrc) {
			if (directiveName === "default-src") {
				directivesExplicitlyDisabled.add("default-src")
				continue
			} else {
				throw new Error(`Content-Security-Policy: tried to disable ${JSON.stringify(directiveName)} as if it were default-src; simply omit the key`)
			}
		} else {
			directiveValue = rawDirectiveValue
		}
		for (const element of directiveValue) {
			if (typeof element === "string") {
				if (isDirectiveValueInvalid(element)) {
					throw new Error(`Content-Security-Policy received an invalid directive value for ${JSON.stringify(directiveName)}`)
				}
				warnIfDirectiveValueEntryShouldBeQuoted(element)
			}
		}
		result.set(directiveName, directiveValue)
	}
	if (useDefaults) {
		Object.entries(defaultDirectives).forEach(([defaultDirectiveName, defaultDirectiveValue]) => {
			if (!result.has(defaultDirectiveName) && !directivesExplicitlyDisabled.has(defaultDirectiveName)) {
				result.set(defaultDirectiveName, defaultDirectiveValue)
			}
		})
	}
	if (!result.size) {
		throw new Error("Content-Security-Policy has no directives. Either set some or disable the header")
	}
	if (!result.has("default-src") && !directivesExplicitlyDisabled.has("default-src")) {
		throw new Error("Content-Security-Policy needs a default-src but none was provided. If you really want to disable it, set it to `contentSecurityPolicy.dangerouslyDisableDefaultSrc`.")
	}
	return result
}
function getHeaderValue(req, res, normalizedDirectives) {
	let err
	const result = []
	normalizedDirectives.forEach((rawDirectiveValue, directiveName) => {
		let directiveValue = ""
		for (const element of rawDirectiveValue) {
			if (typeof element === "function") {
				const newElement = element(req, res)
				warnIfDirectiveValueEntryShouldBeQuoted(newElement)
				directiveValue += " " + newElement
			} else {
				directiveValue += " " + element
			}
		}
		if (!directiveValue) {
			result.push(directiveName)
		} else if (isDirectiveValueInvalid(directiveValue)) {
			err = new Error(`Content-Security-Policy received an invalid directive value for ${JSON.stringify(directiveName)}`)
		} else {
			result.push(`${directiveName}${directiveValue}`)
		}
	})
	return err ? err : result.join(";")
}
const contentSecurityPolicy = function contentSecurityPolicy(options = {}) {
	const headerName = options.reportOnly ? "Content-Security-Policy-Report-Only" : "Content-Security-Policy"
	const normalizedDirectives = normalizeDirectives(options)
	return function contentSecurityPolicyMiddleware(req, res, next) {
		const result = getHeaderValue(req, res, normalizedDirectives)
		if (result instanceof Error) {
			next(result)
		} else {
			res.setHeader(headerName, result)
			next()
		}
	}
}
contentSecurityPolicy.getDefaultDirectives = getDefaultDirectives
contentSecurityPolicy.dangerouslyDisableDefaultSrc = dangerouslyDisableDefaultSrc

exports.dangerouslyDisableDefaultSrc = dangerouslyDisableDefaultSrc
exports.default = contentSecurityPolicy
exports.getDefaultDirectives = getDefaultDirectives

module.exports = exports.default
module.exports.default = module.exports