Different methods of authentication

You have many ways to create an authentication flow, which will be partially covered here.

Delay method

As seen before, doing a lightdm.respond inmediately after a lightdm.authenticate provokes a failed authentication. So we need to add a delay of 100ms or more.

async function wait(ms) {
  return new Promise((resolve) => {
    setTimeout(() => resolve(), ms);
  });
}

async function initGreeter() {
  lightdm.authenticate("superuser")
  await wait(100);
  lightdm.respond("superpassword")
  lightdm.start_session("ubuntu")
}

window.addEventListener("GreeterReady", initGreeter)

Signals approach

web-greeter provides signals to do automatic stuff when something happens from LightDM or web-greeter itself. The most relevant ones for this case are:

• lightdm.show_prompt to provide the password automatically.
• lightdm.authentication_complete to start_session automatically.

So, you could have something like this:

lightdm.show_prompt.connect((text, type) => {
  lightdm.respond("password");
})
lightdm.authentication_complete.connect(() => {
  lightdm.start_session("session");
})

lightdm.authenticate("user");
// Everything is handled by signals from here

lightdm.respond and lightdm.show_prompt

Aditionally, you could check the type provided to the callback of lightdm.show_prompt to either respond with the user or respond with the password.

lightdm.respond, as documented, provides a response to a prompt. Therefore, if you do not start the authentication process with an user, LightDM will prompt to provide it. You can experiment with it on --debug mode:

> lightdm.show_prompt.connect((text, type) => {console.log({text, type})});
> lightdm.authentication_complete.connect(() => {console.log("Authenticated")});
> lightdm.authenticate();
{text: "login:", type: 0}
> lightdm.respond("user");
{text: "Password:", type: 1}
> lightdm.respond("password");
"Authenticated"

According to this, LightDM provides two kind of prompts:

• {text: "login:", type: 0} when no user provided to lightdm.authenticate
  • Then, use lightdm.respond("user")
  • If user provided with lightdm.authenticate, LightDM will prompt for a password
• {text: "Password:", type: 1} after providing an user
  • Use lightdm.respond("password")

And so, you could have something like this:

lightdm.show_prompt.connect((text, type) => {
  if (type == 0) // Login
    lightdm.respond("user");
  else if (type == 1) // Password
    lightdm.respond("password");
})
lightdm.authentication_complete.connect(() => {
  lightdm.start_session("session");
})

lightdm.authenticate();

Manual approach

This might be the simplest to implement, but will require a nice web design to not mess everything up.

Basically, the authentication flow is "managed" by the user:

1. The user selects their user, and run lightdm.authenticate(user)
2. They will provide their password, and run lightdm.respond(password)
3. And so, they click on something that will run their selected session: lightdm.start_session(session)