SvelteKitAuth

Authentication library for use with SvelteKit featuring built-in OAuth providers and zero restriction customization!

Getting Started

SvelteKitAuth is very easy to setup! All you need to do is instantiate the SvelteKitAuth class, and configure it with some default providers:

export const appAuth = new SvelteKitAuth({
  providers: [
    new GoogleOAuthProvider({
      clientId: import.meta.env.VITE_GOOGLE_OAUTH_CLIENT_ID,
      clientSecret: import.meta.env.VITE_GOOGLE_OAUTH_CLIENT_SECRET,
      profile(profile) {
        return { ...profile, provider: "google" };
      },
    }),
  ],
  callbacks: {
    jwt(token, profile) {
      if (profile?.provider) {
        const { provider, ...account } = profile;
        token = {
          ...token,
          user: {
            ...token.user,
            connections: { [provider]: account },
          },
        };
      }

      return token;
    },
  },
  jwtSecret: import.meta.env.JWT_SECRET_KEY,
});

If you want to augment the default SvelteKit session to get access to the user in the session store, you can use the getSession hook:

// overriding the default session
export const { getSession } = appAuth;

// augmenting it
export const getSession: GetSession = async (request) => {
  const { user } = await appAuth.getSession(request);

  return { user };
};

Adding more Providers

SvelteKitAuth uses a object-oriented approach towards creating providers. It is unopionated and allows you to implement any three-legged authentication flow such as OAuth, SAML SSO, and even regular credential logins by omitting the signin() route.

You can implement your own using the Provider base provider class, and by implementing the signin() and callback() methods:

export abstract class Provider<T extends ProviderConfig = ProviderConfig> {
  abstract signin<Locals extends Record<string, any> = Record<string, any>, Body = unknown>(
    request: ServerRequest<Locals, Body>,
  ): EndpointOutput | Promise<EndpointOutput>;

  abstract callback<Locals extends Record<string, any> = Record<string, any>, Body = unknown>(
    request: ServerRequest<Locals, Body>,
  ): CallbackResult | Promise<CallbackResult>;
}

signin() must return a generic endpoint output, this can be a redirect, or the path to the provider's sign-in page. When implementing a HTTP POST route, signin() can simply return an empty body and callback() should handle the user login flow.

callback() takes a ServerRequest and must return a CallbackResult which is a custom type exported by svelte-kit-auth:

export type Profile = any;
export type CallbackResult = [Profile, string | null];

The first item in the tuple is the user profile, which gets stored in the token, and is provided to the jwt() callback as the second argument. The second item is a redirect route, which may be tracked using the state query parameter for OAuth providers, or other implementations depending on the sign-in method.

Motivation

SvelteKitAuth is inspired by the NextAuth.js package built for the Next.js SSR framework for React. Unlike NextAuth.js, though, it is completely unopinionated and only provides implementations for default flows, while still enabling users to add their own providers.

As it leverages classes and Typescript, the implementation of such providers is very straightforward, and in the future it will even be possible to register multiple SvelteKitAuth handlers in the same project, should the need arise, by leveraging a class-based client and server setup.

Contributing

🚧 Work in Progress!

License

This project is licensed under the terms of the MIT license.