How to use an API auth with Lucia

[sudo-sand]

I have an external API that I can send a POST request to /api/v3/user to log in, and I get a cookie and the user in the response.

How can I use this with Lucia?

[pilcrowonpaper]

You want forward cookies when fetching and receiving a response. Just copy the cookies from the request to the SvelteKit app to the request to the external api, and copy the response headers (set-cookie) to the response from the SvelteKit app.

[sudo-sand]

I guess what I'm trying to ask is, how to use an email and password in Lucia?

I can store the cookie and use it, but I'm asking if there is a way to have an adapter that I can do "auth magic" and return a user, which creates a session.

[stefanosandes]

Hey @pilcrowonpaper, I have a similar situation. With NextAuth, we can override the authenticate methods and provide custom authentication logic (an HTTP API in this case) and return the data in the way that NextAuth wants. Is there a way to do this with Lucia?

[pilcrowonpaper]

Sorry I'm missing something. By "authentication logic," do you mean like custom auth/session checks?

[stefanosandes]

Oh, sorry, the method name I mentioned was wrong. The correct name in NextAuth is authorize. It is part of the credentials provider. You can see it being implemented here: https://next-auth.js.org/providers/credentials.

With this method, I can implement my own credentials verification. It's especially useful when integrating with external APIs that require user and password authentication to generate a token for authenticating subsequent requests.

[pilcrowonpaper]

I'm not sure why you wouldn't be able to implement it with Lucia? Check the user credentials (using keys or custom implementation), and then authenticate the user?

[stefanosandes]

Yes, that is my original question. Is there a minimal example on how to do that or does Lucia have a Credentials adapter or something similar?

[pilcrowonpaper]

No? The basics sections in the docs covers almost everything that Lucia provides