Support for Hotspot wifi captive portal via RFC 8910 and RFC 8908

[pparent]

Hi,

Just wanted to mention that a nice and easy addition to Ubuntu touch would be wifi captive portal via RFC 8910 and RFC 8908.

It is actually very simple:

1- When you get a DHCP lease in the wifi interface look for option 114
2- If there is a URL in option 114 it's an API, just make a simple HTTP GET request on this URL (no parameters or header)
3- The result will be a json, if it contains "captive"="true" and has an "user-portal-url" field then we should just open this "user-portal-url" in the browser and it will allow the user to authenticate to the captive portal and use the wifi!

Really I think that's any easy addition, I may try to contribute this inside the OS when I have time.

Ps: Adding a simple script in /etc/dhcp/dhclient-exit-hooks.d/ to do that should do the trick I guess.

[pparent]

So I've found a way to have hotspot detection working with rfc8910.

Here is the behaviour when I connect to a Hotspot Wifi compatible with rfc8910: https://www.youtube.com/shorts/0et6I-lwwwQ

To have it working you need to add to the filesystem the following script:

/etc/NetworkManager/dispatcher.d/99-rfc8910

#!/bin/bash
# NetworkManager dispatcher script for handling DHCP Option 114 (RFC8910)
# Opens the captive portal with URLDispatcher if the network indicates a captive portal

logger "Option 114 init $1 $2" 
IFACE="$1"
STATUS="$2"

# Only proceed if the interface is up or dhcp4-change
if [ "$STATUS" != "dhcp4-change" ]; then
    exit 0
fi

# --- Retrieve the Option 114 value using dhclient test request ---
dhclient -1 -v -lf /var/lib/NetworkManager/dhclient-rfc8910-wlan0.lease wlan0
LEASE_FILE="/var/lib/NetworkManager/dhclient-rfc8910-wlan0.lease"
CAPTIVE_API=$(grep 'option default-url' "$LEASE_FILE" | tail -n1 | awk -F'"' '{print $2}')

# Remove escaped ampersands (\&) from the URL
CAPTIVE_API=$(echo "$CAPTIVE_API" | sed 's/\\//g')

if [ -z "$CAPTIVE_API" ]; then
    logger "No DHCP Option 114 found for interface $IFACE"
    exit 0
fi

logger "DHCP Option 114 detected for $IFACE: $CAPTIVE_API"

# --- Query the captive portal API using wget ---
API_RESPONSE=$(wget -qO- "$CAPTIVE_API")

if [ -z "$API_RESPONSE" ]; then
    logger "Failed to reach captive portal API: $CAPTIVE_API"
    exit 0
fi

# --- Parse JSON for 'captive' and 'user-portal-url' ---
# Extract the 'captive' status (true/false)
CAPTIVE=$(echo "$API_RESPONSE" | grep -oP '"captive"\s*:\s*\K(true|false)')

# Extract the 'user-portal-url' and remove all backslashes
PORTAL_URL=$(echo "$API_RESPONSE" | grep -oP '"user-portal-url"\s*:\s*"\K[^"]+' | sed 's/\\//g')

logger "Captive portal API response: captive=$CAPTIVE, portal_url=$PORTAL_URL"

# --- If the network is captive, open the portal URL via D-Bus ---
if [ "$CAPTIVE" = "true" ] && [ -n "$PORTAL_URL" ]; then
    USER_NAME=phablet
    sudo -u "$USER_NAME" \
        DBUS_SESSION_BUS_ADDRESS="unix:path=/run/user/32011/bus" \
        gdbus call \
            --session \
            --dest com.lomiri.URLDispatcher \
            --object-path /com/lomiri/URLDispatcher \
            --method com.lomiri.URLDispatcher.DispatchURL \
            "$PORTAL_URL" ""

    logger "Captive portal opened: $PORTAL_URL"
fi

Don't forget to chmod +x /etc/NetworkManager/dispatcher.d/99-rfc8910

Tested on 24.04-1.x daily on OnePlus Nord N10

Unfortunatly the script is slightly hacky because it requires to make an external dhclient request. I've not found any other way around. We'll see if it can integrated to the system despite this, and if it can be slightly improved.

On what canal should I discuss with system devs about that?

[pparent]

Ps: we could add in the same script the "legacy" hotspot detection (on top of the RFC8010 detection) based on make a dummy http request on a dummy URL, and it could allow have a large compatibility to detect most hotspot portals on the market.