Arch Linux

burny02

Member

Registered: 2021-07-01

Posts: 129

iptables

Hi

Is there any way to allow captive portal traffic through a firewall (iptables)

Currently everything is routed via my VPN and I don’t allow any other traffic out other interfaces. I noticed on Android, that it still allows captive portal traffic, though.

Is there a way to achieve this through iptables ? Some port or something?

seth

Member

From: Won't reply 2 private help req

Registered: 2012-09-03

Posts: 76,034

Re: iptables

The captive portal is most likely DNS based, so archlinux.org will not be resolved to the portals IP, ideally by the provider intercepting traffic on #53 (ie. forcing DNS on you at this point)
You could wireshark the traffic w/o VPN to see what's going on and will have to allow the providers IP. Instead of allowing them to fudge your DNS you perhaps get away w/ just calling that IP directly to enter the portal.

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Brocellous

Member

Registered: 2017-11-27

Posts: 161

Re: iptables

ios and android use passive detection of captive portals now, when available. [1] [2]

systemd-networkd also supports this, and should show the captive portal URI in the networkctl status output, on supported networks. Otherwise then yeah you'll have to probe for some kinda DNS interception.

[1] https://developer.apple.com/news/?id=q78sq5rv
[2] https://developer.android.com/about/ver … ive-portal