CODEWITHSUNDEEP
javascriptfirefox-addonprotocolsbrowser-extensionfirefox-addon-webextensions
Forivin
Forivin

Reputation: 15548

WebExtensions: Intercept special protocol links

I'd like to write a simple WebExtension that handles certain types of links. I don't want a system wide protocol handler, it should simply work for websites open in my browser.
So for instance when anything causes a magnet:// link to be opened, I'd like to intercept that so that the WebExtension handles it.
And if possible I'd like to prevent system applications from handling it while the WebExtension is enabled.

At first I thought that I could use registerProtocolHandler:

navigator.registerProtocolHandler("magnet", "*%s", "Magnet handler");

But I don't think that this would do what I want it to...
My next idea was to use a click event on all a-elements:

document.getElementsByTagName('a').addEventListener('click', event => {
    let link = event.target.href
    if (link.startsWith('magnet://')) {
        // handle magnet link
        return false
    }
}

But that would only work for links that were clicked on. A link that is opened using JavaScript would not be affected, so that wouldn't work either..

Upvotes: 3

Views: 597

Answers (2)

Simon
Simon

Reputation: 432

I used a trick in an extension to do just that: Register your protocol handler in the manifest:

  "protocol_handlers": [
    {
      "protocol": "magnet",
      "name": "Torrent Control Reloaded Magnet Handler",
      "uriTemplate": "https://torrent-control-reloaded.invalid/%s"
    }
  ]

then handle the request as you wish:

   browser.webRequest.onBeforeRequest.addListener(
        (details) => {
            var parser = document.createElement('a');
            parser.href = details.url;
            var magnetUri = decodeURIComponent(parser.pathname).substr(1);
            // do what you want with magnetUri
            return {cancel: true}
        },
        {urls: ['https://torrent-control-reloaded.invalid/*']},
        ['blocking']
    );

It's not nice, but it works. You can find the extension here: https://github.com/Mika-/torrent-control/

Upvotes: 2

Andrew Swan
Andrew Swan

Reputation: 1343

Work is underway here to support custom protocol handlers: https://bugzilla.mozilla.org/show_bug.cgi?id=1271553

Upvotes: 1

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