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How did a Captive Portal force to open a browser

I've setup a Captive Portal with dd-wrt, wifidog, authpuppy and some plugins from authpuppy as well as my own web app.

  1. I am wondering what's the exact thing that will trigger a browser on the client device to popup?
  2. Is the popup browser from iPhone/iPad a regular browser mode?
    • It seems some JavaScript will fail on the browser mode, like the shake.js, event though iOS Safari version is > 4.2.1 from https://github.com/alexgibson/shake.js/

P.S.:

I've done the research like

  • http://en.wikipedia.org/wiki/Captive_portal
  • https://personaltelco.net/wiki/CaptivePortal

they don't talk much about the popup browser.

Could anyone help?

like image 847
Ace Avatar asked Jul 29 '13 04:07

Ace


People also ask

What triggers captive portal?

Sometimes simply turning off wi-fi, waiting a few seconds, then turning it back on again is enough to trigger the captive portal page to show up again. After you turn the wifi off and on on your device or computer, try re-joining the network, then wait a moment for the captive portal page to reappear.

How does browser detect captive portal?

The Automatic Detection of Captive Portal mechanism is based on a simple verification, done by the Operational System (OS) of the client device (smartphone, tablet, laptop). It simply tries to reach a specific URL and verify that such URL returns a well-known result.

How do I get past the captive portal authorization?

Close everything in your browser. If you have your startup setting “Continue where you left off”, then change it to “Open the new tab page” and open your browser again. If you don't see the captive portal come up, try going to a http:// website as they can trigger the captive portal.

How does a captive portal work?

The captive portal technique makes the user with a Web browser (HTTP client) to see a special Web page before being granted normal Internet access. The captive portal intercepts all packets regardless of address or port, until the browser is used as a form of authentication device.


1 Answers

If you will try to see the network statistics [request/response] you will find out that devices like ios and android both of them continuously hits some particular urls [in case of android it is www.google.com/generate_204 , don't remember exact url for ios]. These url are generated by system internally. These pings let their server know about various details. So as soon as ios gets connected with a captive portal it tries to hit the system generated url, failing to which it understands that this is packet level protected network and open the browser.

Hope this helps.

like image 165
streak Avatar answered Oct 13 '22 07:10

streak