Session support

This package adds support for sessions. Sessions set a unique id in a cookie, and allows you to accociate server-stored data with specific users.


  • It’s lazy. It will only start a session if there is something in the store.
  • It will also automatically wipe the session data if session data was emptied.
  • It provides features for generating and validating CSRF tokens.


npm install @curveball/session

Getting started

Adding the middleware

import session from '@curveball/session';

  store: 'memory',

This will add the in-memory session store to curveball. This store is mostly meant for testing.

Here is another example with more options:

import session from '@curveball/session';

  store: 'memory',
  cookieName: 'MY_SESSION',
  expiry: 7200,
  cookieOptions: {
    secure: true,
    path: '/',
    sameSite: true,
  • cookieName - Updates the name of the HTTP Cookie. It’s CB by default.
  • expiry - The number of seconds of inactivity before the session disappears. this is 3600 seconds by default. It only pertains to the longevity of the session in the store, it doesn’t influence cookie parameters.
  • cookieOptions - If set, override cookie options from the default. The list of supported options can be found in the documentation of the [cookie package][3].

Using the session store

In your own controllers and middlewares, you can set and update session data via the ctx.session property.

app.use( ctx => {

  // Running this will create the session
  ctx.session = { userId: 5 };
  ctx.response.body = 'Hello world';


Deleting a session

To delete an open session, just clear the session data:

app.use( ctx => {

  // Running this will create the session
  ctx.session = null;


Re-generate a session id.

If you clear the session id, but there is still data, the middleware will remove the old session and automatically create a new session id:

app.use( ctx => {

  // This will kill the old session and start a new one with the same data.
  ctx.sessionId = null;


CSRF token support

To obtain a CSRF token for forms, the middleware provides a getCsrf() function:

app.use( async ctx => {

  // Obtain a CSRF token for HTML forms:
  const csrfToken = await ctx.getCsrf();


It’s recommended to embed this token in HTML forms as such:

<input type="hidden" name="csrf-token" value="....token goes here" />

Then on POST requests, you can easily validate the token with the validateCsrf function. If the token was incorrect, this will automatically result in a 403 error:

app.use('/form-submit', ctx => {

  // Throws error if csrf-token was not supplied or incorrect



It’s desirable to create your own stores for product usage. Eventually this project will probably add a few more default stores.

Until then, you must implement the following interface:

interface SessionStore {

  set(id: string, values: SessionValues, expire: number): Promise<void>;
  get(id: string): Promise<SessionValues>,
  delete(id: string): Promise<void>,
  newSessionId(): Promise<string>,


SessionValues is simply a key->value object. expire is expressed as a unix timestamp.