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https://github.com/expressjs/cookie-session

Simple cookie-based session middleware
https://github.com/expressjs/cookie-session

cookie expressjs javascript middleware nodejs session

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Simple cookie-based session middleware

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README 

        
# cookie-session



[![NPM Version][npm-version-image]][npm-url]

[![NPM Downloads][npm-downloads-image]][npm-url]

[![Build Status][ci-image]][ci-url]

[![Test Coverage][coveralls-image]][coveralls-url]



Simple cookie-based session middleware.



A user session can be stored in two main ways with cookies: on the server or on

the client. This module stores the session data on the client within a cookie,

while a module like [express-session](https://www.npmjs.com/package/express-session)

stores only a session identifier on the client within a cookie and stores the

session data on the server, typically in a database.



The following points can help you choose which to use:



  * `cookie-session` does not require any database / resources on the server side,

    though the total session data cannot exceed the browser's max cookie size.

  * `cookie-session` can simplify certain load-balanced scenarios.

  * `cookie-session` can be used to store a "light" session and include an identifier

    to look up a database-backed secondary store to reduce database lookups.



**NOTE** This module does not encrypt the session contents in the cookie, only provides

signing to prevent tampering. The client will be able to read the session data by

examining the cookie's value. Secret data should not be set in `req.session` without

encrypting it, or use a server-side session instead.



**NOTE** This module does not prevent session replay, as the expiration set is that

of the cookie only; if that is a concern of your application, you can store an expiration

date in `req.session` object and validate it on the sever, and implement any other logic

to extend the session as your application needs.



## Install



This is a [Node.js](https://nodejs.org/en/) module available through the

[npm registry](https://www.npmjs.com/). Installation is done using the

[`npm install` command](https://docs.npmjs.com/getting-started/installing-npm-packages-locally):



```sh

$ npm install cookie-session

```



## API



```js

var cookieSession = require('cookie-session')

var express = require('express')



var app = express()



app.use(cookieSession({

  name: 'session',

  keys: [/* secret keys */],



  // Cookie Options

  maxAge: 24 * 60 * 60 * 1000 // 24 hours

}))

```



### cookieSession(options)



Create a new cookie session middleware with the provided options. This middleware

will attach the property `session` to `req`, which provides an object representing

the loaded session. This session is either a new session if no valid session was

provided in the request, or a loaded session from the request.



The middleware will automatically add a `Set-Cookie` header to the response if the

contents of `req.session` were altered. _Note_ that no `Set-Cookie` header will be

in the response (and thus no session created for a specific user) unless there are

contents in the session, so be sure to add something to `req.session` as soon as

you have identifying information to store for the session.



#### Options



Cookie session accepts these properties in the options object.



##### name



The name of the cookie to set, defaults to `session`.



##### keys



The list of keys to use to sign & verify cookie values, or a configured

[`Keygrip`](https://www.npmjs.com/package/keygrip) instance. Set cookies are always

signed with `keys[0]`, while the other keys are valid for verification, allowing

for key rotation. If a `Keygrip` instance is provided, it can be used to

change signature parameters like the algorithm of the signature.



##### secret



A string which will be used as single key if `keys` is not provided.



##### Cookie Options



Other options are passed to `cookies.get()` and `cookies.set()` allowing you

to control security, domain, path, and signing among other settings.



The options can also contain any of the following (for the full list, see

[cookies module documentation](https://www.npmjs.org/package/cookies#readme):



  - `maxAge`: a number representing the milliseconds from `Date.now()` for expiry

  - `expires`: a `Date` object indicating the cookie's expiration date (expires at the end of session by default).

  - `path`: a string indicating the path of the cookie (`/` by default).

  - `domain`: a string indicating the domain of the cookie (no default).

  - `partitioned`: a boolean indicating whether to partition the cookie in Chrome for the [CHIPS Update](https://developers.google.com/privacy-sandbox/3pcd/chips) (`false` by default). If this is true, Cookies from embedded sites will be partitioned and only readable from the same top level site from which it was created.

  - `priority`: a string indicating the cookie priority. This can be set to `'low'`, `'medium'`, or `'high'`.

  - `sameSite`: a boolean or string indicating whether the cookie is a "same site" cookie (`false` by default). This can be set to `'strict'`, `'lax'`, `'none'`, or `true` (which maps to `'strict'`).

  - `secure`: a boolean indicating whether the cookie is only to be sent over HTTPS (`false` by default for HTTP, `true` by default for HTTPS). If this is set to `true` and Node.js is not directly over a TLS connection, be sure to read how to [setup Express behind proxies](https://expressjs.com/en/guide/behind-proxies.html) or the cookie may not ever set correctly.

  - `httpOnly`: a boolean indicating whether the cookie is only to be sent over HTTP(S), and not made available to client JavaScript (`true` by default).

  - `signed`: a boolean indicating whether the cookie is to be signed (`true` by default).

  - `overwrite`: a boolean indicating whether to overwrite previously set cookies of the same name (`true` by default).



### req.session



Represents the session for the given request.



#### .isChanged



Is `true` if the session has been changed during the request.



#### .isNew



Is `true` if the session is new.



#### .isPopulated



Determine if the session has been populated with data or is empty.



### req.sessionOptions



Represents the session options for the current request. These options are a

shallow clone of what was provided at middleware construction and can be

altered to change cookie setting behavior on a per-request basis.



### Destroying a session



To destroy a session simply set it to `null`:



```js

req.session = null

```



### Saving a session



Since the entire contents of the session is kept in a client-side cookie, the

session is "saved" by writing a cookie out in a `Set-Cookie` response header.

This is done automatically if there has been a change made to the session when

the Node.js response headers are being written to the client and the session

was not destroyed.



## Examples



### Simple view counter example



```js

var cookieSession = require('cookie-session')

var express = require('express')



var app = express()



app.set('trust proxy', 1) // trust first proxy



app.use(cookieSession({

  name: 'session',

  keys: ['key1', 'key2']

}))



app.get('/', function (req, res, next) {

  // Update views

  req.session.views = (req.session.views || 0) + 1



  // Write response

  res.end(req.session.views + ' views')

})



app.listen(3000)

```



### Per-user sticky max age



```js

var cookieSession = require('cookie-session')

var express = require('express')



var app = express()



app.set('trust proxy', 1) // trust first proxy



app.use(cookieSession({

  name: 'session',

  keys: ['key1', 'key2']

}))



// This allows you to set req.session.maxAge to let certain sessions

// have a different value than the default.

app.use(function (req, res, next) {

  req.sessionOptions.maxAge = req.session.maxAge || req.sessionOptions.maxAge

  next()

})



// ... your logic here ...

```



### Extending the session expiration



This module does not send a `Set-Cookie` header if the contents of the session

have not changed. This means that to extend the expiration of a session in the

user's browser (in response to user activity, for example) some kind of

modification to the session needs be made.



```js

var cookieSession = require('cookie-session')

var express = require('express')



var app = express()



app.use(cookieSession({

  name: 'session',

  keys: ['key1', 'key2']

}))



// Update a value in the cookie so that the set-cookie will be sent.

// Only changes every minute so that it's not sent with every request.

app.use(function (req, res, next) {

  req.session.nowInMinutes = Math.floor(Date.now() / 60e3)

  next()

})



// ... your logic here ...

```



### Using a custom signature algorithm



This example shows creating a custom `Keygrip` instance as the `keys` option

to provide keys and additional signature configuration.



```js

var cookieSession = require('cookie-session')

var express = require('express')

var Keygrip = require('keygrip')



var app = express()



app.use(cookieSession({

  name: 'session',

  keys: new Keygrip(['key1', 'key2'], 'SHA384', 'base64')

}))



// ... your logic here ...

```



## Usage Limitations



### Max Cookie Size



Because the entire session object is encoded and stored in a cookie, it is

possible to exceed the maximum cookie size limits on different browsers. The

[RFC6265 specification](https://tools.ietf.org/html/rfc6265#section-6.1)

recommends that a browser **SHOULD** allow



> At least 4096 bytes per cookie (as measured by the sum of the length of

> the cookie's name, value, and attributes)



In practice this limit differs slightly across browsers. See a list of

[browser limits here](http://browsercookielimits.iain.guru). As a rule

of thumb **don't exceed 4093 bytes per domain**.



If your session object is large enough to exceed a browser limit when encoded,

in most cases the browser will refuse to store the cookie. This will cause the

following requests from the browser to either a) not have any session

information or b) use old session information that was small enough to not

exceed the cookie limit.



If you find your session object is hitting these limits, it is best to

consider if  data in your session should be loaded from a database on the

server instead of transmitted to/from the browser with every request. Or

move to an [alternative session strategy](https://github.com/expressjs/session#compatible-session-stores)



## License



[MIT](LICENSE)



[ci-image]: https://badgen.net/github/checks/expressjs/cookie-session/master?label=ci

[ci-url]: https://github.com/expressjs/cookie-session/actions?query=workflow%3Aci

[coveralls-image]: https://badgen.net/coveralls/c/github/expressjs/cookie-session/master

[coveralls-url]: https://coveralls.io/r/expressjs/cookie-session?branch=master

[npm-downloads-image]: https://badgen.net/npm/dm/cookie-session

[npm-url]: https://npmjs.org/package/cookie-session

[npm-version-image]: https://badgen.net/npm/v/cookie-session