express-csp-header

Content-Security-Policy middleware for Express

Usage

const { expressCspHeader, INLINE, NONE, SELF } = require('express-csp-header');

app.use(expressCspHeader({
    directives: {
        'default-src': [SELF],
        'script-src': [SELF, INLINE, 'somehost.com'],
        'style-src': [SELF, 'mystyles.net'],
        'img-src': ['data:', 'images.com'],
        'worker-src': [NONE],
        'block-all-mixed-content': true
    }
}));

// express will send header "Content-Security-Policy: default-src 'self'; script-src 'self' 'unsafe-inline' somehost.com; style-src 'self' mystyles.net; img-src data: images.com; workers-src 'none'; block-all-mixed-content; report-uri https://cspreport.com/send;'

nonce parameter

If you want to use nonce parameter you should use NONCE constant. Nonce key will be generated automatically. Also generated nonce key will be stored in req.nonce:

const { expressCspHeader, NONCE } = require('express-csp-header');

app.use(expressCspHeader({
    directives: {
        'script-src': [NONCE]
    }
}));
// express will send header with a random nonce key "Content-Security-Policy: script-src 'nonce-pSQ9TwXOMI+HezKshnuRaw==';"

app.use((req, res) => {
    console.log(req.nonce); // 'pSQ9TwXOMI+HezKshnuRaw=='
})

Auto tld

If you have more than one tlds you may want to have only current tld in your security policy. You can do this by replacing tld by TLD constant:

const { expressCspHeader, TLD } = require('express-csp-header');

app.use(expressCspHeader({
    directives: {
        'script-src': [`mystatic.${TLD}`]
    }
}));
// for myhost.com it will send: "Content-Security-Policy: script-src mystatic.com;"
// for myhost.net it will send: "Content-Security-Policy: script-src mystatic.net;"
// etc

TLD parsing options

express-csp-header uses parse-domain module to replace tld. You can pass its options into domainOptions parameter

const { expressCspHeader, TLD } = require('express-csp-header');

app.use(expressCspHeader({
    directives: {
        'script-src': [`mystatic.${TLD}`]
    },
    domainOptions: {
        customTlds: ['example.com']
    }
}));
// for myhost.com it will send: "Content-Security-Policy: script-src mystatic.com;"
// for myhost.example.com it will send: "Content-Security-Policy: script-src mystatic.example.com;"
// etc

Presets

Read about preset in csp-header docs

Content-Security-Policy-Report-Only mode

To switch on Report-Only mode just specify reportOnly param:

const { expressCspHeader, SELF } = require('express-csp-header');

app.use(expressCspHeader({
    directives: {
        'script-src': [SELF]
    },
    reportOnly: true
}));
// it will send: "Content-Security-Policy-Report-Only: script-src 'self';"

report-uri parameter

const { expressCspHeader, SELF } = require('express-csp-header');

app.use(expressCspHeader({
    directives: {
        'script-src': [SELF]
    },
    reportUri: 'https://cspreport.com/send'
}));
// express will send header "Content-Security-Policy: script-src 'self'; report-uri https://cspreport.com/send;"

If you want to pass some params to the report uri just pass function instead of string:

const { expressCspHeader, SELF } = require('express-csp-header');

app.use(expressCspHeader({
    directives: {
        'script-src': [SELF]
    },
    reportUri: (req, res) => {
        return `https://cspreport.com/send?time=${Number(new Date())}`;
    }
}));
// express will send header "Content-Security-Policy: script-src 'self'; report-uri https://cspreport.com/send?time=1460467355592;"

BREAKING CHANGES in express-csp-header@3

💥 No default export

For compability with JS we have to export expressCspHeader as a named export.

const { expressCspHeader } = require('express-csp-header');

💥 policies was renamed to directives

💥 Minimal supported version of Node.JS is 8

💥 Dropped support of extend

extend was marked as deprecated in previous versions. It doesn't work anymore. Use presets instead.

💥 Dropped support of specifying presets as a string

express-csp-header used to require preset if you specify it as a string. Now, you should require it by yourself. Before:

{
    //...
    presets: ['csp-preset-myservice']
}

Now:

{
    //...
    presets: [require('csp-preset-myservice')]
}