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3.0.1 • Public • Published

Double CSRF

A utility package to help implement stateless CSRF protection using the Double Submit Cookie Pattern in express.

Dos and Don'tsGetting StartedConfigurationUtilitiesSupport


This module provides the necessary pieces required to implement CSRF protection using the Double Submit Cookie Pattern. This is a stateless CSRF protection pattern, if you are using sessions and would prefer a stateful CSRF strategy, please see csrf-sync for the Synchroniser Token Pattern.

Since csurf has been deprecated I struggled to find alternative solutions that were accurately implemented and configurable, so I decided to write my own! Thanks to NextAuth as I referenced their implementation. From experience CSRF protection libraries tend to complicate their configuration, and if misconfigured, can render the protection completely useless.

This is why csrf-csrf aims to provide a simple and targeted implementation to simplify it's use.

Dos and Don'ts

Getting Started

This section will guide you through using the default setup, which does sufficiently implement the Double Submit Cookie Pattern. If you'd like to customise the configuration, see the configuration section.

You will need to be using cookie-parser and the middleware should be registered before Double CSRF. In case you want to use signed CSRF cookies, you will need to provide cookie-parser with a unique secret for cookie signing. This utility will set a cookie containing both the csrf token and a hash of the csrf token and provide the non-hashed csrf token so you can include it within your response.

If you're using TypeScript, requires TypeScript >= 3.8

npm install cookie-parser csrf-csrf
// ESM
import { doubleCsrf } from "csrf-csrf";

// CommonJS
const { doubleCsrf } = require("csrf-csrf");
const {
  invalidCsrfTokenError, // This is just for convenience if you plan on making your own middleware.
  generateToken, // Use this in your routes to provide a CSRF hash + token cookie and token.
  validateRequest, // Also a convenience if you plan on making your own middleware.
  doubleCsrfProtection, // This is the default CSRF protection middleware.
} = doubleCsrf(doubleCsrfOptions);

This will extract the default utilities, you can configure these and re-export them from your own module. You should only transmit your token to the frontend as part of a response payload, do not include the token in response headers or in a cookie, and do not transmit the token hash by any other means.

To create a route which generates a CSRF token and a cookie containing ´${token|tokenHash}´:

const myRoute = (request, response) => {
  const csrfToken = generateToken(request, response);
  // You could also pass the token into the context of a HTML response.
  res.json({ csrfToken });
const myProtectedRoute = (req, res) =>
  res.json({ unpopularOpinion: "Game of Thrones was amazing" });

Instead of importing and using generateToken, you can also use req.csrfToken any time after the doubleCsrfProtection middleware has executed on your incoming request.

request.csrfToken(); // same as generateToken(req, res);

You can also put the token into the context of a templated HTML response. Just make sure you register this route before registering the middleware so you don't block yourself from getting a token.

// Make sure your session middleware is registered before these
express.get("/csrf-token", myRoute);
// Any non GET routes registered after this will be considered "protected"

By default, any request that are not GET, HEAD, or OPTIONS methods will be protected. You can configure this with the ignoredMethods option.

You can also protect routes on a case-to-case basis:

app.get("/secret-stuff", doubleCsrfProtection, myProtectedRoute);

Once a route is protected, you will need to ensure the hash cookie is sent along with the request and by default you will need to include the generated token in the x-csrf-token header, otherwise you'll receive a `403 - ForbiddenError: invalid csrf token`. If your cookie is not being included in your requests be sure to check your withCredentials and CORS configuration.


If you plan on using express-session then please ensure your cookie-parser middleware is registered after express-session, as express session parses it's own cookies and may cionflict.

Using asynchronously

csrf-csrf itself will not support promises or async, however there is a way around this. If your csrf token is stored externally and needs to be retrieved asynchronously, you can register an asynchronous middleware first, which exposes the token.

(req, res, next) => {
    .then((token) => {
      req.asyncCsrfToken = token;
    .catch((error) => next(error));

And in this example, your getTokenFromRequest would look like this:

(req) => req.asyncCsrfToken;


When creating your doubleCsrf, you have a few options available for configuration, the only required option is getSecret, the rest have sensible defaults (shown below).

const doubleCsrfUtilities = doubleCsrf({
  getSecret: () => "Secret", // A function that optionally takes the request and returns a secret
  cookieName: "__Host-psifi.x-csrf-token", // The name of the cookie to be used, recommend using Host prefix.
  cookieOptions: {
    sameSite = "lax",  // Recommend you make this strict if posible
    path = "/",
    secure = true,
    ...remainingCOokieOptions // See cookieOptions below
  size: 64, // The size of the generated tokens in bits
  ignoredMethods: ["GET", "HEAD", "OPTIONS"], // A list of request methods that will not be protected.
  getTokenFromRequest: (req) => req.headers["x-csrf-token"], // A function that returns the token from the request


(request: Request) => string;


This should return a secret key to be used for hashing the CSRF tokens.



Default: "__Host-psifi.x-csrf-token"

Optional: The name of the httpOnly cookie that will be used to track CSRF protection. If you change this it is recommend that you continue to use the __Host- or __Secure- security prefix.

Change for development

The security prefix requires the secure flag to be true and requires requests to be received via HTTPS, unless you have your local instance running via HTTPS, you will need to change this value in your development environment.


  sameSite?: string;
  path?: string;
  secure?: boolean
  ...remainingCookieOptions // See below.


  sameSite: "lax",
  path: "/",
  secure: true

The options provided to the cookie, see cookie attributes. The remaining options are all undefined by default and consist of:

  maxAge?: number | undefined;
  signed?: boolean | undefined;
  expires?: Date | undefined;
  domain?: string | undefined;
  encode?: (val: string) => string

Change for development

For development you will need to set secure to false unless you're running HTTPS locally. Ensure secure is true in your live environment by using environment variables.


(req: Request) => string | null | undefined;


(req: Request) => req.headers["x-csrf-token"];

This function should return the token sent by the frontend, the doubleCsrfProtection middleware will validate the value returned by this function against the value in the cookie.




An array of request types that the doubleCsrfProtection middleware will ignore, requests made matching these request methods will not be protected. It is recommended you leave this as the default.




The size in bytes of the tokens that will be generated, if you plan on re-generating tokens consider dropping this to 32.


Below is the documentation for what doubleCsrf returns.


(request: Request, response: Response, next: NextFunction) => void

The middleware used to actually protect your routes, see the getting started examples above, or the examples included in the repository.


(request: Request, response: Response, overwrite?: boolean) => string;

By default if a csrf-csrf cookie already exists on an incoming request, generateToken will not overwrite it, it will simply return the existing token. If you wish to force a token generation, you can use the third parameter:

generateToken(req, res, true); // This will force a new token to be generated, and a new cookie to be set, even if one already exists

Instead of importing and using generateToken, you can also use req.csrfToken any time after the doubleCsrfProtection middleware has executed on your incoming request.

req.csrfToken(); // same as generateToken(req, res) and generateToken(req, res, false);
req.csrfToken(true); // same as generateToken(req, res, true);

The generateToken function serves the purpose of establishing a CSRF (Cross-Site Request Forgery) protection mechanism by generating a token and an associated cookie. This function also provides the option to utilize a third parameter called overwrite. By default, this parameter is set to false.

It returns a CSRF token and attaches a cookie to the response object. The cookie content is `${token}|${tokenHash}`.

You should only transmit your token to the frontend as part of a response payload, do not include the token in response headers or in a cookie, and do not transmit the token hash by any other means.

When overwrite is set to false, the function behaves in a way that preserves the existing CSRF cookie and its corresponding token and hash. In other words, if a valid CSRF cookie is already present in the incoming request, the function will reuse this cookie along with its associated token.

On the other hand, if overwrite is set to true, the function will generate a new token and cookie each time it is invoked. This behavior can potentially lead to certain complications, particularly when multiple tabs are being used to interact with your web application. In such scenarios, the creation of new cookies with every call to the function can disrupt the proper functioning of your web app across different tabs, as the changes might not be synchronized effectively (you would need to write your own synchronization logic).


This is the error instance that gets passed as an error to the next call, by default this will be handled by the default error handler.


(req: Request) => boolean;

This function is used by the doubleCsrfProtection middleware to determine whether an incoming request has a valid CSRF token. You can use this to make your own custom middleware (not recommended).


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