jwt-csrf

jwt-csrf

CSRF protection using the power of JWTs. Provides a number of stateless methods of csrf protection, if you don't want to keep a session.

Defaults to the double submit method of csrf protection, but supports a number of different strategies.

Middleware

Example

var express = require('express');
var app = express();

var jwtCSRF = require('jwt-csrf');
var jwtMiddleware = jwtCSRF.middleware(options); // This can be used like any other Express middleware

app.use(jwtMiddleware); // Executed on all requests

The middleware must be included before others to be effective.

Handling errors

On errors, jwt-csrf will call next(err) with a jwtCSRF.CSRFError. If you want to handle this specifically, you can do so in a middleware:

function(err, req, res, next) {
    if (err instanceof jwtCSRF.CSRFError) {
        explode();
    }
}

Options

options is an Object with the following format:

• secret : String (Required) - Your application's secret, must be cryptographically complex.
• csrfDriver : String (Optional) - CSRF driver/strategy to use. Defaults to DOUBLE_SUBMIT.
• expiresInMinutes : Number (Optional) - A token's expiration time. Defaults to 60.
• headerName : String (Optional) - The name of the response header that will contain the csrf token. Defaults to x-csrf-jwt.
• excludeUrls : Array (Optional) - An array of elements that can be comprised of any of the following
• A regular expression object. The request url will be compared using RegExp.test() using the regular expression supplied here
• A two element array with the first being a string based regular expression and the second being the regular expression options such as "i" or "g". A regular expression will be created and tested against the request url. This is the ideal way to create a regular expression if the excludUrls are defined in a JSON file.
• A string. This string will be tested as a regular expression with no regexp options. If this doesn't match the request.originalUrl, then it will be tested against the url as a direct string match.
• getUserToken : Function (Optional) - Get a user specific token for the AUTHED_TOKEN and AUTHED_DOUBLE_SUBMIT strategies. Must accept req and return a user-specific token (like a user id) for a known user.
• getCookieDomain : Function (Optional) - Must accept req and return a domain that the cookie will be scoped for (Ex: ".mysite.com"). Otherwise, defaults to the domain inside of the request.

CSRF Drivers

DOUBLE_SUBMIT

Persist two linked tokens on the client side, one via an http header, another via a cookie. On incoming requests, match the tokens.

AUTHED_TOKEN

Persist a token via an http header linked to the currently authenticated user. Validate against the user for incoming requests.

Requires getUserToken to be set in options

AUTHED_DOUBLE_SUBMIT

A combination of DOUBLE_SUBMIT and AUTHED_TOKEN, either strategy passing will allow the request to go through.

Client side

Note that jwt-csrf only works for ajax calls, not full-page posts, since it relies on being able to set and read http headers.

Persisting the csrf token

Firstly, you will need to pass the token down in your initial page render. You can get the value as follows on the server-side, to insert into your initial html:

var jwtCsrf = require('jwt-csrf');
var token = jwtCsrf.getHeaderToken(req, res, { secret: mySecret });

You have two options for persisting the csrf token on the client side:

1. Manually

• On every ajax response, persist the x-csrf-jwt header
• On every ajax request, send the persisted x-csrf-jwt header

For example:

var csrfJwt;

jQuery.ajax({
    type: 'POST',
    url: '/api/some/action',
    headers: {
        'x-csrf-jwt': csrfJwt
    },
    success: function(data, textStatus, request){
        csrfJwt = request.getResponseHeader('x-csrf-jwt');
    }
});

2. Automatically, by patching XMLHttpRequest

var jwtCsrf = require('jwt-csrf/client');
jwtCsrf.setToken(initialToken);
jwtCsrf.patchXhr();

This will hook into each request and response and automatically persist the token on the client side for you.