Edge-CSRF

Edge-CSRF is a CSRF protection library that runs on the edge runtime.

This library helps you to implement the signed double submit cookie pattern except it only uses edge runtime dependencies so it can be used in both node environments and in edge functions (e.g. Vercel Edge Functions, Cloudflare Page Functions). The recommended way to use this library is via its drop-in integrations for Next.js and SvelteKit though it also has a lower-level API for more custom implementations.

We hope you enjoy using this software. Contributions and suggestions are welcome!

Features

• Runs on both node and edge runtimes
• Includes a Next.js integration (see here)
• Includes a SvelteKit integration (see here)
• Includes a low-level API for custom integrations (see below)
• Gets token from HTTP request header (X-CSRF-Token) or from request body field (csrf_token)
• Handles form-urlencoded, multipart/form-data or json-encoded HTTP request bodies
• Supports Server Actions via form and non-form submission
• Customizable cookie options

Install

To use Edge-CSRF, just add it as a dependency to your app:

1npm install edge-csrf
2# or
3pnpm add edge-csrf
4# or
5yarn add edge-csrf

Quickstart (Next.js)

To use Edge-CSRF with your Next.js app, first create a middleware file (middleware.ts) for your project and add the Edge-CSRF middleware:

1// middleware.ts
2
3import { createMiddleware } from 'edge-csrf/nextjs';
4
5// initalize csrf protection middleware
6const csrfMiddleware = createMiddleware({
7  cookie: {
8    secure: process.env.NODE_ENV === 'production',
9  },
10});
11
12export const middleware = csrfMiddleware;

Now, all HTTP submission requests (e.g. POST, PUT, DELETE, PATCH) will be rejected if they do not include a valid CSRF token. To add the CSRF token to your forms, you can fetch it from the X-CSRF-Token HTTP response header server-side or client-side. For example:

1// app/page.tsx
2
3import { headers } from 'next/headers';
4
5export default function Page() {
6  const csrfToken = headers().get('X-CSRF-Token') || 'missing';
7
8  return (
9    <form action="/api/form-handler" method="post">
10      <input type="hidden" value={csrfToken}>
11      <input type="text" name="my-input">
12      <input type="submit">
13    </form>
14  );
15}

1// app/form-handler/route.ts
2
3import { NextResponse } from 'next/server';
4
5export async function POST() {
6  return NextResponse.json({ status: 'success' });
7}

Quickstart (SvelteKit)

To use Edge-CSRF with your SvelteKit app, first create a server-side hooks file (hooks.server.ts) for your project and add the Edge-CSRF handle:

1// src/hooks.server.ts
2
3import { createHandle } from 'edge-csrf/sveltekit';
4
5// initalize csrf protection handle
6const csrfHandle = createHandle({
7  cookie: {
8    secure: process.env.NODE_ENV === 'production',
9  },
10});
11
12export const handle = csrfHandle;

Now, all HTTP submission requests (e.g. POST, PUT, DELETE, PATCH) will be rejected if they do not include a valid CSRF token. To add the CSRF token to your forms, you can fetch it from the event's locals data object server-side. For example:

1// src/routes/+page.server.ts
2
3export async function load({ locals }) {
4  return {
5    csrfToken: locals.csrfToken,
6  };
7}
8
9export const actions = {
10  default: async () => {
11    return { success: true };
12  },
13};

1<!-- src/routes/+page.svelte -->
2
3<script lang="ts">
4  export let data;
5
6  export let form;
7</script>
8
9{#if form?.success}
10<span>success</span>
11{:else}
12<form method="post">
13  <input type="hidden" value={data.csrfToken}>
14  <input type="text" name="my-input">
15  <input type="submit">
16</form>
17{/if}

Finally, to make typescript aware of the new locals attributes you can add Edge-CSRF types to your app's types:

1// src/app.d.ts
2
3import type { EdgeCsrfLocals } from 'edge-csrf/sveltekit';
4
5declare global {
6  namespace App {
7    // ...
8    interface Locals extends EdgeCsrfLocals {}
9    // ...
10  }
11}
12
13export {};

Integrations

For details about each integration see:

• Next.js README
• SvelteKit README

Low-level API

The following methods are named exports in the the top-level edge-csrf module:

createSecret(length) - Create new secret (cryptographically secure)

  * @param {int} length - Byte length of secret
  * @returns {Uint8Array} - The secret

createToken(secret, saltByteLength) - Create new CSRF token (cryptographically insecure
                                      salt hashed with secret)

  * @param {Uint8Array} secret - The secret
  * @param {int} saltByteLength - Salt length in number of bytes
  * @returns {Promise<Uint8Array>} - A promise returning the token in Uint8Array format

getTokenString(request) - Get the CSRF token from the request

  * @param {Request} request - The request object
  * @returns {Promise<string>} - A promise returning the token in string format

verifyToken(token, secret) - Verify the CSRF token and secret obtained from the request

  * @param {Uint8Array} token - The CSRF token
  * @param {Uint8Array} secret - The CSRF secret
  * @returns {Promise<boolean>} - A promise returning result of verification

utoa(input) - Encode Uint8Array as base64 string

  * @param {Uint8Array} input - The data to be converted from Uint8Array to base64
  * @returns {string} The base64 encoded string

atou(input) - Decode base64 string into Uint8Array

  * @param {string} input - The data to be converted from base64 to Uint8Array
  * @returns {Uint8Array} - The Uint8Array representing the input string

Note: If you're using these methods you're probably working on a custom framework integration. If so, please consider contributing it back to this project!

Development

Get the code

To develop edge-csrf, first clone the repository then install the dependencies:

1git clone git@github.com:kubetail-org/edge-csrf.git
2cd edge-csrf
3pnpm install

Run the unit tests

Edge-CSRF uses jest for testing (via vitest). To run the tests in node, edge and miniflare environments, use the test-all command:

1pnpm test-all

The test files are colocated with the source code in the src/ directory, with the filename format {name}.test.ts.

Build for production

To build Edge-CSRF for production, run the build command:

1pnpm build

The build artifacts will be located in the dist/ directory.