Improving the experience with public Wi-Fi hotspots

When travelling, I tend to rely on public Wi-Fi hotspots a lot, for example on trains, while waiting at the station, in cafe’s and so on.

Accepting the same terms and conditions every time gets annoying pretty quickly, so a few years ago I decided to automate this. The project that came out of that is freewifid.

It continously scans for Wi-Fi networks it knows, and sends you a notification when it found one it can automatically connect to. You can then allow it to connect to that network automatically in the future.

Adding support for new captive portals

Adding support for a new kind of captive portal is pretty easy. You just need to implement a small rust trait that includes a function that sends the specific request for the captive portal. Often this is very simple and looks like this:

pub struct LtgLinkProvider {}

impl LtgLinkProvider {
    pub fn new() -> LtgLinkProvider { LtgLinkProvider {} }
}

impl CaptivePortal for LtgLinkProvider {
    fn can_handle(&self, ssid: &str) -> bool {
        ["Link WIFI"].contains(&ssid)
    }

    fn login(&self, http_client: &ureq::Agent) -> anyhow::Result<()> {
        // Store any cookies the landing page might send
        common::follow_automatic_redirect(http_client)?;

        http_client
            .post("http://192.168.1.100:8880/guest/s/default/login")
            .send_form([
                ("checkbox", "on"),
                ("landing_url", crate::GENERIC_CHECK_URL),
                ("accept", "PRISIJUNGTI"),
            ])?;

        Ok(())
    }
}

For finding out what needs to be sent, you can use your favoute browser’s inspection tools.

For testing, Plasma’s feature for assigning a random MAC-address comes very handy.

Integration with Plasma

It could be interesting to write a KCM for freewifid, so you can graphically remove networks again. Support for ignoring public networks in the presence of a given SSID is also already implemented, but currently needs to be enabled by editing the config file. Writing a KCM is not high on my list of priorities right now, but if this sounds like something you’d like to do, I’d happily help with with the freewifid interfacing parts.

Project

The project is hosted on Codeberg. I’ll happily accept merge requests for additional captive portals there.

There are some prebuilt release binaries, but I’m not too certain they’ll work on every distribution. With a rust compiler installed, the project is very simple to build (cargo build). A systemd unit is provided in the repository, which you can use to run freewifid as a user unit.

Freewifid also supports running as a system service non-interactively for use in embedded projects.