gomagiclink

Magic Link authentication framework for Go. The idea is to avoid asking the user for the password every time they login, and send them a "magic link" to their e-mail address. Once they confirm the login by clicking the link, the user is considered logged in. This has the advantage of not handling user passwords at all, and the disadvantage that if their e-mail account is compromised, this will cascade to services dependant on the e-mail account, such as ones implementing the magic link login.

This package implements the core part of this process, by generating a cryptographically safe magic link challenge and a session id (useful for web cookies). To keep the process safe, you need to maintain the security of the secret key, passed to the NewAuthMagicLinkController() function.

API reference

Design decisions

• We don't write down information about the user until they verify the challenge
• We don't write down session information at all, but verify the cookie JWT-style
• We allow the app to attach arbitrary data about a user, and store it with the user record
• We allow easy implementation of different data stores

Workflows

See these examples for more info:

• the web app example
• the CLI example

Registration / Login

1. Construct an AuthUserDatabase
2. Construct an AuthMagicLinkController
3. Collect user e-mail (web form, etc)
4. Generate a challenge string (magic cookie) with GenerateChallenge(), construct a link with it and send it to user's e-mail
5. Verify the challenge with VerifyChallenge(). If successful, it will return an UserAuthRecord
6. Optionally attach custom user data to the CustomData field of the record and store the AuthUserRecord with StoreUser(). Note that this data will be stored and retrieved as JSON, so the CustomData needs to be of a type that can survive a round-trip through JSON. For example, ints will be returned as float64s.

Session

1. Generate a session ID with GenerateSessionId(), send to browser, e.g. as a HTTP cookie, or a Bearer token
2. Each time the browser sends back the session ID, verify it with VerifySessionId(). It will return an AuthUserRecord if successful. Inspect the CustomData field if you've set it before.

Sending e-mail

Configuring an e-mail server, etc. is waaaay out of scope for this package, but here's a good e-mail library for Go.