CSRF

Logic behind CSRF token creation and verification.

Read Understanding-CSRF for more information on CSRF. Use this module to create custom CSRF middleware.

Looking for a CSRF framework for your favorite framework that uses this module?

• Express/connect: csurf or alt-xsrf
• Koa: koa-csrf or koa-atomic-session

This module is a fork of https://github.com/pillarjs/csrf at f0d66c91ea4be6d30a03bd311ed9518951d9c3e4.

Install

$ npm i @fastify/csrf

TypeScript

This module includes a TypeScript declaration file to enable auto-complete in compatible editors and type information for TypeScript projects.

API

const Tokens = require('@fastify/csrf')

new Tokens([options])

Create a new token generation/verification instance. The options argument is optional and will just use all defaults if missing.

Options

Tokens accept these properties in the options object.

algorithm

The hash-algorithm to generate the token. Defaults to sha256.

saltLength

The length of the internal salt to use, in characters. Internally, the salt is a base 62 string. Defaults to 8 characters.

secretLength

The length of the secret to generate, in bytes. Note that the secret is passed around base-64 encoded and that this length refers to the underlying bytes, not the length of the base-64 string. Defaults to 18 bytes.

userInfo

Require user-specific information in tokens.create() and tokens.verify().

hmacKey

When set, the hmacKey is used to generate the cryptographic HMAC hash instead of the default hash function.

validity

The maximum validity of the token to generate, in milliseconds. Note that the epoch is passed around base-36 encoded. Defaults to 0 milliseconds (disabled).

tokens.create(secret[, userInfo])

Create a new CSRF token attached to the given secret. The secret is a string, typically generated from the tokens.secret() or tokens.secretSync() methods. This token is what you should add into HTML <form> blocks and expect the user's browser to provide back.

const secret = tokens.secretSync()
const token = tokens.create(secret)

The userInfo parameter can be used to protect against cookie tossing attacks (and similar) when the application is deployed with untrusted subdomains. It will encode some user-specific information within the token. It is used only if userInfo: true is passed to the constructor.

tokens.secret(callback)

Asynchronously create a new secret, which is a string. The secret is to be kept on the server, typically stored in a server-side session for the user. The secret should be at least per user.

tokens.secret(function (err, secret) {
  if (err) throw err
  // Do something with the secret
})

tokens.secret()

Asynchronously create a new secret and return a Promise. Please see tokens.secret(callback) documentation for full details.

Note: To use promises in Node.js prior to 0.12, promises must be "polyfilled" using global.Promise = require('bluebird').

tokens.secret().then(function (secret) {
  // Do something with the secret
})

tokens.secretSync()

A synchronous version of tokens.secret(callback). Please see tokens.secret(callback) documentation for full details.

const secret = tokens.secretSync()

tokens.verify(secret, token[, userInfo])

Check whether a CSRF token is valid for the given secret, returning a Boolean.

if (!tokens.verify(secret, token)) {
  throw new Error('invalid token!')
}

The userInfo parameter is required if userInfo: true was configured during initialization. The user-specific information must match what was passed in tokens.create().

License

Licensed under MIT.