Session cookies

This page builds upon the API defined in the Basic session API page.

Framework and library specific guides are also available:

• Astro
• Next.js
• SvelteKit

CSRF protection

CSRF protection is a must when using cookies. A very simple way to prevent CSRF attacks is to check the Origin header for non-GET requests. If you rely on this method, it is crucial that your application does not use GET requests for modifying resources.

// `HTTPRequest` and `HTTPResponse` are generic interfaces.
// Adjust this code to fit your framework's API.

function handleRequest(request: HTTPRequest, response: HTTPResponse): void {
	if (request.method !== "GET") {
		const origin = request.headers.get("Origin");
		// You can also compare it against the Host or X-Forwarded-Host header.
		if (origin === null || origin !== "https://example.com") {
			response.setStatusCode(403);
			return;
		}
	}

	// ...
}

Cookies

If the frontend and backend are hosted on the same domain, session cookies should have the following attributes:

• HttpOnly: Cookies are only accessible server-side
• SameSite=Lax: Use Strict for critical websites
• Secure: Cookies can only be sent over HTTPS (Should be omitted when testing on localhost)
• Max-Age or Expires: Must be defined to persist cookies
• Path=/: Cookies can be accessed from all routes

Lucia v3 used auth_session as the session cookie name.

// `HTTPResponse` is a generic interface.
// Adjust this code to fit your framework's API.

export function setSessionTokenCookie(response: HTTPResponse, token: string, expiresAt): void {
	if (env === Env.PROD) {
		// When deployed over HTTPS
		response.headers.add(
			"Set-Cookie",
			`session=${token}; HttpOnly; SameSite=Lax; Expires=${expiresAt.toUTCString()}; Path=/; Secure;`
		);
	} else {
		// When deployed over HTTP (localhost)
		response.headers.add(
			"Set-Cookie",
			`session=${token}; HttpOnly; SameSite=Lax; Expires=${expiresAt.toUTCString()}; Path=/`
		);
	}
}

export function deleteSessionTokenCookie(response: HTTPResponse): void {
	if (env === Env.PROD) {
		// When deployed over HTTPS
		response.headers.add(
			"Set-Cookie",
			"session=; HttpOnly; SameSite=Lax; Max-Age=0; Path=/; Secure;"
		);
	} else {
		// When deployed over HTTP (localhost)
		response.headers.add("Set-Cookie", "session=; HttpOnly; SameSite=Lax; Max-Age=0; Path=/");
	}
}

Session validation

Sessions can be validated by getting the cookie and using the validateSession() function we created. If the session is invalid, delete the session cookie. Importantly, we recommend setting a new session cookie after validation to persist the cookie for an extended time.

import {
	validateSessionToken,
	deleteSessionTokenCookie,
	setSessionTokenCookie
} from "./session.js";

// `HTTPRequest` and `HTTPResponse` are generic interfaces.
// Adjust this code to fit your framework's API.

function handleRequest(request: HTTPRequest, response: HTTPResponse): void {
	// csrf protection
	if (request.method !== "GET") {
		const origin = request.headers.get("Origin");
		// You can also compare it against the Host or X-Forwarded-Host header.
		if (origin === null || origin !== "https://example.com") {
			response.setStatusCode(403);
			return;
		}
	}

	// session validation
	const cookies = parseCookieHeader(request.headers.get("Cookie") ?? "");
	const token = cookies.get("session");
	if (token === null) {
		response.setStatusCode(401);
		return;
	}

	const { session, user } = await validateSessionToken(token);
	if (session === null) {
		deleteSessionTokenCookie(response);
		response.setStatusCode(401);
		return;
	}
	setSessionTokenCookie(response, token, session, expiresAt);

	// ...
}