Automatic negotiation of a captive portal: connect to icomera wifi in CD trains without having to jump through hoops.

CDWiFi (České dráhy) WiFi Internet Access

# I believe this is the necessary and sufficient step to get internet access on board the Czech long distance trains (e.g. EuroCity which runs from Prague to Kiel)
curl -vLA '' 'http://cdwifi.cz/portal/api/vehicle/gateway/user/authenticate'

# It says "500 internal server error" but that doesn't keep it from working.

# check with this request, answer should contain "authenticated":1
curl -vLA '' 'http://cdwifi.cz/portal/api/vehicle/gateway/user'

# Also nice: GPS data (but seems outdated)
curl -vLA '' 'http://cdwifi.cz/portal/internal/api/x6/position'

# Really nice: show connectivity including the LTE uplinks
curl -vLA '' http://www.info.cdwifi.cz/api/jsonp/connectivity

@bzamecnik Nice to see that my solution still works. I've linked to yours in the https://github.com/fnordomat/misc/blob/master/captive-be-gone/minisurvey.txt and hope to expand this even further, especially as travel picks up again :-)

thanks

Some more fun: Using the /connectivity/ endpoint, we can see the currently connected links. A command line shortcut to see those that are connected and their signal level:

curl -s  http://www.info.cdwifi.cz/api/jsonp/connectivity/ \
    | tr -d '(' | tr -d ')' | tr -d ';' |  \
    jq '.links[] | select(.link_state=="available")'

{
  "index": "104",
  "device_type": "modem",
  "device_subtype": "sierra-7710",
  "device_state": "up",
  "link_state": "available",
  "rssi": "-55",
  "technology": "lte",
  "operator_id": "26201",
  "apninfo": "railnet.telekom,-1,-1",
  "umts_info": {
    "net_status": "1",
    "lac": "FFFE",
    "cellid": "0231E502"
  }
}
{
  "index": "105",
  "device_type": "modem",
  "device_subtype": "sierra-7710",
  "device_state": "up",
  "link_state": "available",
  "rssi": "-81",
  "technology": "lte",
  "operator_id": "26202",
  "apninfo": "fv1.deutschebahn.com,-1,-1",
  "umts_info": {
    "net_status": "1",
    "lac": "FFFE",
    "cellid": "002AE302"
  }
}

or show only some fields using

curl -s  http://www.info.cdwifi.cz/api/jsonp/connectivity/ \
    | tr -d '(' | tr -d ')' | tr -d ';' |  \
    jq '.links[] | select(.link_state=="available") | {rssi, apninfo, technology}''

{
  "rssi": "-51",
  "apninfo": "railnet.telekom,-1,-1",
  "technology": "lte"
}
{
  "rssi": "-70",
  "apninfo": "fv1.deutschebahn.com,-1,-1",
  "technology": "lte"
}

Nice!

I was traveling to Praha this weekend and I don't know if it's intentional, but the confirmation page on http://www.cdwifi.cz/ only works with a czech locale (cs-CZ,cs). For this to work, you may have to delete the cockies