express-session-jwt

Express session using JWT. Drop-in replacement of express-session with enhanced security (blog post).

Compared to the original express-session, this fork:
1. Uses JWT as session tokens
2. Uses public-key cryptography (ES256) for better access to secrets
3. Prevents session fixation (e.g., when a user logs in a new token is emitted)
4. Guarantees that destroyed sessions can't be re-saved (e.g., a logged out session can't become alive again)
5. Reduces the impact of data theft from the store (stores hash(sessId) instead of sessId)
6. Improves upon deprecated default config options

It's a drop-in replacement of express-session in the sense than you can replace the npm package and existing sessions will be transparently upgraded to JWT without logging your users out. See the Examples below.

Features

- [x] Pass all original express-session tests (only changes are the default config values)
- [x] Add keys option with public/private keys
- [x] Add jwtFromReq option to return content of JWT token
- [x] Issue a new JWT token when the result of jwtFromReq changes (e.g., set a user id)
- [x] Transparently upgrade existing original Express sessions (retrieve data from db with old id, generate JWT token, store data with new id)
- [x] Use hash(sessId) instead of sessId as primary key in the store
- [x] Prevent race condition that would re-save a destroyed session (fix in MemoryStore)
- [x] Support key rotation (sign with the latest private key, try to verify with older public keys as well)
- [ ] Add async keys provider (retrieve keys from req and/or token)
- [ ] Support verifier only mode (public keys only, no private key)
- [ ] Richer interface for stores

Installation

This is a Node.js module available through the
npm registry. Installation is done using the
npm install command:

``sh
$ npm install express-session-jwt
`

API

`js
var session = require('express-session-jwt')
`

$3

Create a session middleware with the given options.

Note Session data is _not_ saved in the cookie itself, just the session ID.
Session data is stored server-side.

Note Since version 1.5.0, the cookie-parser middleware
no longer needs to be used for this module to work. This module now directly reads
and writes cookies on req/res. Using cookie-parser may result in issues
if the secret is not the same between this module and cookie-parser.

Warning The default server-side session storage, MemoryStore, is _purposely_
not designed for a production environment. It will leak memory under most
conditions, does not scale past a single process, and is meant for debugging and
developing.

For a list of stores, see compatible session stores.

#### Options

express-session-jwt accepts these properties in the options object.


##### keys

Required option

Set the private and public key(s) to sign/verify the JWT tokens.

Keys should either be an object with public and private properties, or an array of such objects.
When an array, the first element is the most recent key. For older keys only the public key is required, the private key can be omitted.

Examples:
`js
keys: { public: '...', private: '...' }
`
or
`js
keys: [{ public: 'latest', private: '...' }, { public: 'old1' }, { public: 'old2' }]
`

We currenlty use the ES256 algorithm. Keys can be generated with:
`bash
openssl ecparam -name secp256k1 -genkey -noout -out private-key.pem
openssl ec -in ec-secp256k1-priv-key.pem -pubout > public-key.pem
`

##### jwtFromReq

Function to call to generate the payload of a JWT token.
Provide a function that returns an object that will be used as payload.
The function is given req as the first argument if you want to use
some value attached to req when generating the JWT token.

Example:
`js
function jwtFromReq(req) {
return req.user ? {
user_id: req.user.id,
roles: ['user', 'editor']
} : null
}
`

#### Options (same as the original express-session)

express-session-jwt also accepts these properties as the original express-session.

##### cookie

Settings object for the session ID cookie. The default value is
{ path: '/', httpOnly: true, secure: false, maxAge: null }.

The following are options that can be set in this object.

##### cookie.domain

Specifies the value for the Domain Set-Cookie attribute. By default, no domain
is set, and most clients will consider the cookie to apply to only the current
domain.

##### cookie.expires

Specifies the Date object to be the value for the Expires Set-Cookie attribute.
By default, no expiration is set, and most clients will consider this a
"non-persistent cookie" and will delete it on a condition like exiting a web browser
application.

Note If both expires and maxAge are set in the options, then the last one
defined in the object is what is used.

Note The expires option should not be set directly; instead only use the maxAge
option.

##### cookie.httpOnly

Specifies the boolean value for the HttpOnly Set-Cookie attribute. When truthy,
the HttpOnly attribute is set, otherwise it is not. By default, the HttpOnly
attribute is set.

Note be careful when setting this to true, as compliant clients will not allow
client-side JavaScript to see the cookie in document.cookie.

##### cookie.maxAge

Specifies the number (in milliseconds) to use when calculating the Expires
Set-Cookie attribute. This is done by taking the current server time and adding
maxAge milliseconds to the value to calculate an Expires datetime. By default,
no maximum age is set.

Note If both expires and maxAge are set in the options, then the last one
defined in the object is what is used.

##### cookie.path

Specifies the value for the Path Set-Cookie. By default, this is set to '/', which
is the root path of the domain.

##### cookie.sameSite

Specifies the boolean or string to be the value for the SameSite Set-Cookie attribute.

- true will set the SameSite attribute to Strict for strict same site enforcement.
- false will not set the SameSite attribute.
- 'lax' will set the SameSite attribute to Lax for lax same site enforcement.
- 'none' will set the SameSite attribute to None for an explicit cross-site cookie.
- 'strict' will set the SameSite attribute to Strict for strict same site enforcement.

More information about the different enforcement levels can be found in
[the specification][rfc-6265bis-03-4.1.2.7].

Note This is an attribute that has not yet been fully standardized, and may change in
the future. This also means many clients may ignore this attribute until they understand it.

Note There is a draft spec
that requires that the Secure attribute be set to true when the SameSite attribute has been
set to 'none'. Some web browsers or other clients may be adopting this specification.

##### cookie.secure

Specifies the boolean value for the Secure Set-Cookie attribute. When truthy,
the Secure attribute is set, otherwise it is not. By default, the Secure
attribute is not set.

Note be careful when setting this to true, as compliant clients will not send
the cookie back to the server in the future if the browser does not have an HTTPS
connection.

Please note that secure: true is a recommended option. However, it requires
an https-enabled website, i.e., HTTPS is necessary for secure cookies. If secure
is set, and you access your site over HTTP, the cookie will not be set. If you
have your node.js behind a proxy and are using secure: true, you need to set
"trust proxy" in express:

`js
var app = express()
app.set('trust proxy', 1) // trust first proxy
app.use(session({
secret: 'keyboard cat',
resave: false,
saveUninitialized: true,
cookie: { secure: true }
}))
`

For using secure cookies in production, but allowing for testing in development,
the following is an example of enabling this setup based on NODE_ENV in express:

`js
var app = express()
var sess = {
secret: 'keyboard cat',
cookie: {}
}

if (app.get('env') === 'production') {
app.set('trust proxy', 1) // trust first proxy
sess.cookie.secure = true // serve secure cookies
}

app.use(session(sess))
`

The cookie.secure option can also be set to the special value 'auto' to have
this setting automatically match the determined security of the connection. Be
careful when using this setting if the site is available both as HTTP and HTTPS,
as once the cookie is set on HTTPS, it will no longer be visible over HTTP. This
is useful when the Express "trust proxy" setting is properly setup to simplify
development vs production configuration.

##### genid

Function to call to generate a new session ID. Provide a function that returns
a string that will be used as a session ID. The function is given req as the
first argument if you want to use some value attached to req when generating
the ID.

The default value is a function which uses the uid-safe library to generate IDs.

NOTE be careful to generate unique IDs so your sessions do not conflict.

`js
app.use(session({
genid: function(req) {
return genuuid() // use UUIDs for session IDs
},
secret: 'keyboard cat'
}))
`

##### name

The name of the session ID cookie to set in the response (and read from in the
request).

The default value is 'connect.sid'.

Note if you have multiple apps running on the same hostname (this is just
the name, i.e. localhost or 127.0.0.1; different schemes and ports do not
name a different hostname), then you need to separate the session cookies from
each other. The simplest method is to simply set different names per app.

##### proxy

Trust the reverse proxy when setting secure cookies (via the "X-Forwarded-Proto"
header).

The default value is undefined.

- true The "X-Forwarded-Proto" header will be used.
- false All headers are ignored and the connection is considered secure only
if there is a direct TLS/SSL connection.
- undefined Uses the "trust proxy" setting from express

##### resave

Forces the session to be saved back to the session store, even if the session
was never modified during the request. Depending on your store this may be
necessary, but it can also create race conditions where a client makes two
parallel requests to your server and changes made to the session in one
request may get overwritten when the other request ends, even if it made no
changes (this behavior also depends on what store you're using).

The default value is false.

How do I know if this is necessary for my store? The best way to know is to
check with your store if it implements the touch method. If it does, then
you can safely set resave: false. If it does not implement the touch
method and your store sets an expiration date on stored sessions, then you
likely need resave: true.

##### rolling

Force the session identifier cookie to be set on every response. The expiration
is reset to the original maxAge, resetting the expiration
countdown.

The default value is false.

With this enabled, the session identifier cookie will expire in
maxAge since the last response was sent instead of in
maxAge since the session was last modified by the server.

This is typically used in conjuction with short, non-session-length
maxAge values to provide a quick timeout of the session data
with reduced potential of it occurring during on going server interactions.

Note When this option is set to true but the saveUninitialized option is
set to false, the cookie will not be set on a response with an uninitialized
session. This option only modifies the behavior when an existing session was
loaded for the request.

##### saveUninitialized

Forces a session that is "uninitialized" to be saved to the store. A session is
uninitialized when it is new but not modified.

The default value is false.

Note if you are using Session in conjunction with PassportJS, Passport
will add an empty Passport object to the session for use after a user is
authenticated, which will be treated as a modification to the session, causing
it to be saved. This has been fixed in PassportJS 0.3.0

##### secret

This is the secret used to sign the session ID cookie by the original Express session.

This option is required to upgrade existing Express sessions into the new format.

This can be either a string
for a single secret, or an array of multiple secrets. If an array of secrets is
provided, only the first element will be used to sign the session ID cookie, while
all the elements will be considered when verifying the signature in requests. The
secret itself should be not easily parsed by a human and would best be a random set
of characters. A best practice may include:

- The use of environment variables to store the secret, ensuring the secret itself
does not exist in your repository.
- Periodic updates of the secret, while ensuring the previous secret is in the
array.

Using a secret that cannot be guessed will reduce the ability to hijack a session to
only guessing the session ID (as determined by the genid option).

Changing the secret value will invalidate all existing sessions. In order to rotate
the secret without invalidating sessions, provide an array of secrets, with the new
secret as first element of the array, and including previous secrets as the later
elements.

##### store

The session store instance, defaults to a new MemoryStore instance.

##### unset

Control the result of unsetting req.session (through delete, setting to null,
etc.).

The default value is 'keep'.

- 'destroy' The session will be destroyed (deleted) when the response ends.
- 'keep' The session in the store will be kept, but modifications made during
the request are ignored and not saved.

$3

To store or access session data, simply use the request property req.session,
which is (generally) serialized as JSON by the store, so nested objects
are typically fine. For example below is a user-specific view counter:

`js
// Use the session middleware
app.use(session({ secret: 'keyboard cat', cookie: { maxAge: 60000 }}))

// Access the session as req.session
app.get('/', function(req, res, next) {
if (req.session.views) {
req.session.views++
res.setHeader('Content-Type', 'text/html')
res.write('

views: ' + req.session.views + '

')
res.write('

expires in: ' + (req.session.cookie.maxAge / 1000) + 's

')
res.end()
} else {
req.session.views = 1
res.end('welcome to the session demo. refresh!')
}
})
`

#### Session.regenerate(callback)

To regenerate the session simply invoke the method. Once complete,
a new SID and Session instance will be initialized at req.session
and the callback will be invoked.

`js
req.session.regenerate(function(err) {
// will have a new session here
})
`

#### Session.destroy(callback)

Destroys the session and will unset the req.session property.
Once complete, the callback will be invoked.

`js
req.session.destroy(function(err) {
// cannot access session here
})
`

#### Session.reload(callback)

Reloads the session data from the store and re-populates the
req.session object. Once complete, the callback will be invoked.

`js
req.session.reload(function(err) {
// session updated
})
`

#### Session.save(callback)

Save the session back to the store, replacing the contents on the store with the
contents in memory (though a store may do something else--consult the store's
documentation for exact behavior).

This method is automatically called at the end of the HTTP response if the
session data has been altered (though this behavior can be altered with various
options in the middleware constructor). Because of this, typically this method
does not need to be called.

There are some cases where it is useful to call this method, for example,
redirects, long-lived requests or in WebSockets.

`js
req.session.save(function(err) {
// session saved
})
`

#### Session.touch()

Updates the .maxAge property. Typically this is
not necessary to call, as the session middleware does this for you.

$3

Each session has a unique ID associated with it. This property is an
alias of req.sessionID and cannot be modified.
It has been added to make the session ID accessible from the session
object.

$3

The content of the JWT token, parsed at the beginning of a request.
Add arbitrary data via the jwtFromReq option.

$3

Each session has a unique cookie object accompany it. This allows
you to alter the session cookie per visitor. For example we can
set req.session.cookie.expires to false to enable the cookie
to remain for only the duration of the user-agent.

#### Cookie.maxAge

Alternatively req.session.cookie.maxAge will return the time
remaining in milliseconds, which we may also re-assign a new value
to adjust the .expires property appropriately. The following
are essentially equivalent

`js
var hour = 3600000
req.session.cookie.expires = new Date(Date.now() + hour)
req.session.cookie.maxAge = hour
`

For example when maxAge is set to 60000 (one minute), and 30 seconds
has elapsed it will return 30000 until the current request has completed,
at which time req.session.touch() is called to reset
req.session.cookie.maxAge to its original value.

`js
req.session.cookie.maxAge // => 30000
`

#### Cookie.originalMaxAge

The req.session.cookie.originalMaxAge property returns the original
maxAge (time-to-live), in milliseconds, of the session cookie.

$3

To get the ID of the loaded session, access the request property
req.sessionID. This is simply a read-only value set when a session
is loaded/created.

Session Store Implementation

Every session store _must_ be an EventEmitter and implement specific
methods. The following methods are the list of required, recommended,
and optional.

* Required methods are ones that this module will always call on the store.
* Recommended methods are ones that this module will call on the store if
available.
* Optional methods are ones this module does not call at all, but helps
present uniform stores to users.

For an example implementation view the connect-redis repo.

$3

Optional

This optional method is used to get all sessions in the store as an array. The
callback should be called as callback(error, sessions).

$3

Required

This required method is used to destroy/delete a session from the store given
a session ID (sid). The callback should be called as callback(error) once
the session is destroyed.

$3

Optional

This optional method is used to delete all sessions from the store. The
callback should be called as callback(error) once the store is cleared.

$3

Optional

This optional method is used to get the count of all sessions in the store.
The callback should be called as callback(error, len).

$3

Required

This required method is used to get a session from the store given a session
ID (sid). The callback should be called as callback(error, session).

The session argument should be a session if found, otherwise null or
undefined if the session was not found (and there was no error). A special
case is made when error.code === 'ENOENT' to act like callback(null, null).

$3

Required

This required method is used to upsert a session into the store given a
session ID (sid) and session (session) object. The callback should be
called as callback(error) once the session has been set in the store.

$3

Recommended

This recommended method is used to "touch" a given session given a
session ID (sid) and session (session) object. The callback should be
called as callback(error) once the session has been touched.

This is primarily used when the store will automatically delete idle sessions
and this method is used to signal to the store the given session is active,
potentially resetting the idle timer.

Compatible Session Stores

For a complete list of compatible stores see the original docs. Any store that works with express-session should work unmodified with our library.

We recommend the following stores because they enforce that destroyed sessions can't be re-saved (e.g., a logged out session can't become alive again). Please make a PR to list additional stores.

[![★][connect-typeorm-image] connect-typeorm][connect-typeorm-url] A TypeORM-based session store.

[connect-typeorm-url]: https://www.npmjs.com/package/connect-typeorm
[connect-typeorm-image]: https://badgen.net/github/stars/makepost/connect-typeorm?label=%E2%98%85

Examples

$3

A simple example using express-session-jwt to store page views for a user.

`js
var express = require('express')
var parseurl = require('parseurl')
var session = require('express-session-jwt')

var app = express()

app.use(session({
secret: 'keyboard cat', // to upgrade existing Express sessions
keys: {
public: '-----BEGIN PUBLIC KEY-----\nMFYwEAYHKoZIzj0CAQYFK4EEAAoDQgAEDXMuNS4pyqkpZwij+UCcTPVStZHmG39D\nP1V7qaPCfc0ewXXbcEaJiarqjHOM5a6SVivCaUdJj+25tjMk4sPchQ==\n-----END PUBLIC KEY-----',
private: '-----BEGIN PRIVATE KEY-----\nMIGEAgEAMBAGByqGSM49AgEGBSuBBAAKBG0wawIBAQQgvK1dk5M81nax8lQxpbWo\nsB1oK9YAqRP7MwWc7wDne8ehRANCAAQNcy41LinKqSlnCKP5QJxM9VK1keYbf0M/\nVXupo8J9zR7BddtwRomJquqMc4zlrpJWK8JpR0mP7bm2MyTiw9yF\n-----END PRIVATE KEY-----'
},
}))

app.use(function (req, res, next) {
if (!req.session.views) {
req.session.views = {}
}

// get the url pathname
var pathname = parseurl(req).pathname

// count the views
req.session.views[pathname] = (req.session.views[pathname] || 0) + 1

next()
})

app.get('/foo', function (req, res, next) {
res.send('you viewed this page ' + req.session.views['/foo'] + ' times')
})

app.get('/bar', function (req, res, next) {
res.send('you viewed this page ' + req.session.views['/bar'] + ' times')
})

app.listen(3000);
`

$3

Minimal example for the original express-session:
`js
app.use(session({
secret: 'keyboard cat',
}))
`

Minimal example for express-session-jwt:
`js
app.use(session({
keys: {
public: 'public',
private: 'secret',
}
}))
`

Minimal example for express-session-jwt that also validates and upgrade existing sessions:
`js
app.use(session({
secret: 'keyboard cat', // validate then upgrade original sessions
keys: {
public: 'public',
private: 'secret',
}
}))
`

(Coming soon) Really minimal example for express-session-jwt, verifier only:
`js
app.use(session({
keys: {
public: 'public',
}
}))
`

$3

Recommended example for the original express-session:
`js
const store =
new TypeormStore({
cleanupLimit: 2,
limitSubquery: false,
ttl: 302460*60
}).connect(repository)

app.use(session({
secret: 'keyboard cat',
resave: false,
saveUninitialized: false,
cookie: {
secure: true,
maxAge: 302460601000
},
store: store
}))
`

Recommended example for express-session-jwt (updated some deprecated defaults):
`js
const store =
new TypeormStore({
cleanupLimit: 2,
limitSubquery: false,
ttl: 302460*60
}).connect(repository)

app.use(session({
secret: 'keyboard cat',
keys: {
public: 'public',
private: 'secret',
},
store: store
}))
`

Recommended example for express-session-jwt, storing data in the JWT token:
`js
const store = …

function jwtFromReq(req) {
return req.user ?
{
user_id, req.user.id,
account_id: ...,
roles: ['user', 'editor'],
} : null
}

app.use(session({
secret: 'keyboard cat',
keys: {
public: 'public',
private: 'secret',
},
store: store,
jwtFromReq: jwtFromReq
}))
`

$3

Key rotation example for the original express-session:
`js
app.use(session({
secret: [
'latest',
'old1',
'old2',
]
}))
`

Key rotation example for express-session-jwt (only the latest private key is used, the others can be omitted):
`js
app.use(session({
keys: [
{
public: 'latest',
private: 'secret',
},
{ public: 'old1' },
{ public: 'old2' }
]
}))
`

(Coming soon) Keys provider example for express-session-jwt:
`js
async function keysProvider(req, rawJwtToken, done) {
return done(null, [
{
public: 'latest',
private: 'secret',
},
{ public: 'old1' },
{ public: 'old2' }
])
}

app.use(session({
keysProvider: keysProvider,
}))
`

Debugging

This module uses the debug module
internally to log information about session operations.

To see all the internal logs, set the DEBUG environment variable to
express-session when launching your app (npm start, in this example):

`sh
$ DEBUG=express-session npm start
`

On Windows, use the corresponding command;

`sh
> set DEBUG=express-session & npm start
``

License

MIT

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

[rfc-6265bis-03-4.1.2.7]: https://tools.ietf.org/html/draft-ietf-httpbis-rfc6265bis-03#section-4.1.2.7
[npm-downloads-image]: https://badgen.net/npm/dm/express-session-jwt
[npm-url]: https://www.npmjs.com/package/express-session-jwt
[npm-version-image]: https://badgen.net/npm/v/express-session-jwt