I keep hearing of people who have used Lemmy for a few days or a few weeks and want to start using a mobile version – often Voyager.
They open Voyager for the first time, and get a screen with a button for logging in. They get a choice for which Lemmy instance to join, but no place for entering their existing username or password.
I’ve told them that “in the first screen there is a button that is very difficult to notice, allowing you to use a pre-existing Lemmy username. Find that semi-hidden button, click it, and you can login.”
It is of course a working workaround to pre-emptively tell people that the button exists, is just very well hidden, and needs to be clicked by most people who download Voyager. But still, it would be cool if the screen for new users could be altered so that the ability to log in with a pre-existing username was equally visible as the choice to create a new account!
You would only be able to login this way with your username. If you by mistake use your email, then it simply doesn’t resolve to a Lemmy server and the login fails.
Meldrik@notlemmyserver.com would simply fail, because that Lemmy instance does not exist.
But what if it does exist? But your have an email server on the same domain? Or what if that domain is being malicious and masquerading as a Lemmy instance to steal your credentials?
It doesn’t matter if there’s an email server or not.
I am not logging in with the credentials “meldrik@lemmy.wtf”. I am telling Voyager that I want to log into “Lemmy.wtf” with my user “Meldrik”. Before I type a password, the app will check if “Lemmy.wtf” exists and maybe even check if there is in fact a user named “Meldrik”. If all are true, then it will ask for password.
Something like that. I don’t know how Voyager works 😁
that’s still making assumptions about where you want to login to. The fact is that you can login, today, to Lemmy.world with “username” of “me@lemmy.wtf” assuming Lemmy.wtf has an email server setup. And it’s not a safe assumption because users DO have email addresses saved in their passwords manager as a username for whatever random instance, and there should be a 0% chance of sending user credentials to the wrong domain.
I can’t just trust that domain to say they’re a Lemmy instance, and there is a user with that username on the domain. That’s trivial to exploit.
It’s true you can login with your email, instead of your username. But what I am saying is, in Voyager, it should only ask for your username+instance (meldrik@lemmy.wtf).
If I by mistake type my email: meldrik@protonmail.com it will obviously fail, right? Because there’s no Lemmy server at that domain.
You already validate Lemmy servers in Voyager, right? So if “Meldrik@lemmy.wtf” doesn’t match a Lemmy server, an error would show.
I validate lemmy servers by asking the server if it’s a lemmy server. If the protonmail.com is malicious and says, “sure I’m a lemmy server” then credentials would be sent to it, which is not good
If I typed the wrong domain here and it turned out it’s a malicious server pretending to be a Lemmy server, then what happens?
Also, wouldn’t it be highly unlikely that the users email domain is malicious?
You explicitly select the instance, so there is no question of what domain Voyager will contact. Also, on the next screen where you enter credentials, you see the domain and its icon, and you can click to open in the browser to further confirm that you are connecting to the correct instance (if you accidentally select the wrong one)
I can also enter the instance name myself on that screen and then it checks if it’s a Lemmy server, right?
So if there was a “login with username”, you would type your username@instance, then Voyager would check the domain and show the next page you are talking about, with a pre-filled username.