Cookie Signature

And lastly, with an introduction of Cookie Schema, and t.Cookie type. We are able to create a unified type for handling sign/verify cookie signature automatically.

Cookie signature is a cryptographic hash appended to a cookie's value, generated using a secret key and the content of the cookie to enhance security by adding a signature to the cookie.

This make sure that the cookie value is not modified by malicious actor, helps in verifying the authenticity and integrity of the cookie data.

Using Cookie Signature

By provide a cookie secret, and sign property to indicate which cookie should have a signature verification.

import { Elysia, t } from 'elysia'

new Elysia()
    .get('/', ({ cookie: { profile } }) => {
        profile.value = {
            id: 617,
            name: 'Summoning 101'
        }
    }, {
        cookie: t.Cookie({
            profile: t.Object({
                id: t.Numeric(),
                name: t.String()
            })
        }, {
            secrets: 'Fischl von Luftschloss Narfidort',
            sign: ['profile']
        })
    })

Elysia then sign and unsign cookie value automatically.

Constructor

You can use Elysia constructor to set global cookie secret, and sign value to apply to all route globally instead of inlining to every route you need.

import { Elysia, t } from 'elysia'

new Elysia({
    cookie: {
        secrets: 'Fischl von Luftschloss Narfidort',
        sign: ['profile']
    }
})
    .get('/', ({ cookie: { profile } }) => {
        profile.value = {
            id: 617,
            name: 'Summoning 101'
        }
    }, {
        cookie: t.Cookie({
            profile: t.Object({
                id: t.Numeric(),
                name: t.String()
            })
        })
    })

Cookie Rotation

Elysia handle Cookie's secret rotation automatically.

Cookie Rotation is a migration technique to sign a cookie with a newer secret, while also be able to verify the old signature of the cookie.

import { Elysia } from 'elysia'

new Elysia({
    cookie: {
        secrets: ['Vengeance will be mine', 'Fischl von Luftschloss Narfidort']
    }
})

Config

Below is a cookie config accepted by Elysia.

secret

The secret key for signing/un-signing cookies.

If an array is passed, will use Key Rotation.

Key rotation is when an encryption key is retired and replaced by generating a new cryptographic key.

---

Below is a config that extends from 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.

encode

@default encodeURIComponent

Specifies a function that will be used to encode a cookie's value.

Since the value of a cookie has a limited character set (and must be a simple string), this function can be used to encode a value into a string suited for a cookie's value.

The default function is the global encodeURIComponent, which will encode a JavaScript string into UTF-8 byte sequences and then URL-encode any that fall outside of the cookie range.

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.

TIP

The cookie storage model specification states that if both expires and maxAge are set, then maxAge takes precedence, but not all clients may obey this, so if both are set, they should point to the same date and time.

httpOnly

@default false

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 not set.

TIP

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

maxAge

@default undefined

Specifies the number (in seconds) to be the value for the Max-Age Set-Cookie attribute.

The given number will be converted to an integer by rounding down. By default, no maximum age is set.

TIP

The cookie storage model specification states that if both expires and maxAge are set, then maxAge takes precedence, but not all clients may obey this, so if both are set, they should point to the same date and time.

path

Specifies the value for the Path Set-Cookie attribute.

By default, the path handler is considered the default path.

priority

Specifies the string to be the value for the Priority Set-Cookie attribute. low will set the Priority attribute to Low. medium will set the Priority attribute to Medium, the default priority when not set. high will set the Priority attribute to High.

More information about the different priority levels can be found in the specification.

TIP

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.

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.

TIP

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.

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.

TIP

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.