Lucia

Username and password auth in Next.js App Router

Before starting, make sure you've set up your database as described in the Getting started page.

An example project based on this tutorial is also available. You can clone the example locally or open it in StackBlitz.

npx degit https://github.com/lucia-auth/examples/tree/v3/nextjs-app/username-and-password

Update database

Add a username and hashed_password column to your user table.

column type attributes
username string unique
hashed_password string

Create a DatabaseUserAttributes interface in the module declaration and add your database columns. By default, Lucia will not expose any database columns to the User type. To add a username field to it, use the getUserAttributes() option.

import { Lucia } from "lucia";

export const lucia = new Lucia(adapter, {
	sessionCookie: {
		expires: false,
		attributes: {
			secure: process.env.NODE_ENV === "production"
		}
	},
	getUserAttributes: (attributes) => {
		return {
			// attributes has the type of DatabaseUserAttributes
			username: attributes.username
		};
	}
});

declare module "lucia" {
	interface Register {
		Lucia: typeof lucia;
		DatabaseUserAttributes: DatabaseUserAttributes;
	}
}

interface DatabaseUserAttributes {
	username: string;
}

Sign up user

Create app/signup/page.tsx and set up a basic form and action.

export default async function Page() {
	return (
		<>
			<h1>Create an account</h1>
			<form action={signup}>
				<label htmlFor="username">Username</label>
				<input name="username" id="username" />
				<br />
				<label htmlFor="password">Password</label>
				<input type="password" name="password" id="password" />
				<br />
				<button>Continue</button>
			</form>
		</>
	);
}

async function signup(_: any, formData: FormData): Promise<ActionResult> {}

interface ActionResult {
	error: string;
}

In the form action, first do a very basic input validation. Hash the password, generate a new user ID, and create a new user. If successful, create a new session with Lucia.createSession() and set a new session cookie.

import { db } from "@/lib/db";
import { Argon2id } from "oslo/password";
import { cookies } from "next/headers";
import { lucia } from "@/lib/auth";
import { redirect } from "next/navigation";
import { generateId } from "lucia";

export default async function Page() {}

async function signup(_: any, formData: FormData): Promise<ActionResult> {
	"use server";
	const username = formData.get("username");
	// username must be between 4 ~ 31 characters, and only consists of lowercase letters, 0-9, -, and _
	// keep in mind some database (e.g. mysql) are case insensitive
	if (
		typeof username !== "string" ||
		username.length < 3 ||
		username.length > 31 ||
		!/^[a-z0-9_-]+$/.test(username)
	) {
		return {
			error: "Invalid username"
		};
	}
	const password = formData.get("password");
	if (typeof password !== "string" || password.length < 6 || password.length > 255) {
		return {
			error: "Invalid password"
		};
	}

	const hashedPassword = await new Argon2id().hash(password);
	const userId = generateId(15);

	// TODO: check if username is already used
	await db.table("user").insert({
		id: userId,
		username: username,
		hashed_password: hashedPassword
	});

	const session = await lucia.createSession(userId, {});
	const sessionCookie = lucia.createSessionCookie(session.id);
	cookies().set(sessionCookie.name, sessionCookie.value, sessionCookie.attributes);
	return redirect("/");
}

We recommend using Argon2id, but Oslo also provides Scrypt and Bcrypt. These only work in Node.js. If you're planning to deploy your project to a non-Node.js runtime, use Scrypt provided by lucia. This is a pure JS implementation but 2~3 times slower. For Bun, use Bun.password.

import { Scrypt } from "lucia";

new Scrypt().hash(password);

If you're using Bcrypt, set the maximum password length to 64 bytes.

const length = new TextEncoder().encode(password).length;

Sign in user

Create app/login/page.tsx and set up a basic form and action.

// app/login/page.tsx
export default async function Page() {
	return (
		<>
			<h1>Sign in</h1>
			<form action={login}>
				<label htmlFor="username">Username</label>
				<input name="username" id="username" />
				<br />
				<label htmlFor="password">Password</label>
				<input type="password" name="password" id="password" />
				<br />
				<button>Continue</button>
			</form>
		</>
	);
}

async function login(_: any, formData: FormData): Promise<ActionResult> {}

interface ActionResult {
	error: string;
}

In the form action, first do a very basic input validation. Get the user with the username and verify the password. If successful, create a new session with Lucia.createSession() and set a new session cookie.

import { Argon2id } from "oslo/password";
import { cookies } from "next/headers";
import { lucia } from "@/lib/auth";
import { redirect } from "next/navigation";

export default async function Page() {}

async function login(_: any, formData: FormData): Promise<ActionResult> {
	"use server";
	const username = formData.get("username");
	if (
		typeof username !== "string" ||
		username.length < 3 ||
		username.length > 31 ||
		!/^[a-z0-9_-]+$/.test(username)
	) {
		return {
			error: "Invalid username"
		};
	}
	const password = formData.get("password");
	if (typeof password !== "string" || password.length < 6 || password.length > 255) {
		return {
			error: "Invalid password"
		};
	}

	const existingUser = await db
		.table("username")
		.where("username", "=", username.toLowerCase())
		.get();
	if (!existingUser) {
		// NOTE:
		// Returning immediately allows malicious actors to figure out valid usernames from response times,
		// allowing them to only focus on guessing passwords in brute-force attacks.
		// As a preventive measure, you may want to hash passwords even for invalid usernames.
		// However, valid usernames can be already be revealed with the signup page among other methods.
		// It will also be much more resource intensive.
		// Since protecting against this is none-trivial,
		// it is crucial your implementation is protected against brute-force attacks with login throttling etc.
		// If usernames are public, you may outright tell the user that the username is invalid.
		return {
			error: "Incorrect username or password"
		};
	}

	const validPassword = await new Argon2id().verify(existingUser.password, password);
	if (!validPassword) {
		return {
			error: "Incorrect username or password"
		};
	}

	const session = await lucia.createSession(existingUser.id, {});
	const sessionCookie = lucia.createSessionCookie(session.id);
	cookies().set(sessionCookie.name, sessionCookie.value, sessionCookie.attributes);
	return redirect("/");
}

Validate requests

Create validateRequest(). This will check for the session cookie, validate it, and set a new cookie if necessary. Make sure to catch errors when setting cookies and wrap the function with cache() to prevent unnecessary database calls. To learn more, see the Validating requests page.

CSRF protection should be implemented but Next.js handles it when using form actions (but not for API routes).

import { cookies } from "next/headers";
import { cache } from "react";

import type { Session, User } from "lucia";

export const lucia = new Lucia();

export const validateRequest = cache(
	async (): Promise<{ user: User; session: Session } | { user: null; session: null }> => {
		const sessionId = cookies().get(lucia.sessionCookieName)?.value ?? null;
		if (!sessionId) {
			return {
				user: null,
				session: null
			};
		}

		const result = await lucia.validateSession(sessionId);
		// next.js throws when you attempt to set cookie when rendering page
		try {
			if (result.session && result.session.fresh) {
				const sessionCookie = lucia.createSessionCookie(result.session.id);
				cookies().set(sessionCookie.name, sessionCookie.value, sessionCookie.attributes);
			}
			if (!result.session) {
				const sessionCookie = lucia.createBlankSessionCookie();
				cookies().set(sessionCookie.name, sessionCookie.value, sessionCookie.attributes);
			}
		} catch {}
		return result;
	}
);

This function can then be used in server components and form actions to get the current session and user.

import { redirect } from "next/navigation";
import { validateRequest } from "@/lib/auth";

export default async function Page() {
	const { user } = await validateRequest();
	if (!user) {
		return redirect("/login");
	}
	return <h1>Hi, {user.username}!</h1>;
}

Sign out

Sign out users by invalidating their session with Lucia.invalidateSession(). Make sure to remove their session cookie by setting a blank session cookie created with Lucia.createBlankSessionCookie().

import { lucia, validateRequest } from "@/lib/auth";
import { redirect } from "next/navigation";
import { cookies } from "next/headers";

export default async function Page() {
	return (
		<form action={logout}>
			<button>Sign out</button>
		</form>
	);
}

async function logout(): Promise<ActionResult> {
	"use server";
	const { session } = await validateRequest();
	if (!session) {
		return {
			error: "Unauthorized"
		};
	}

	await lucia.invalidateSession(session.id);

	const sessionCookie = lucia.createBlankSessionCookie();
	cookies().set(sessionCookie.name, sessionCookie.value, sessionCookie.attributes);
	return redirect("/login");
}