Can I connect to a hidden wifi without knowing the ESSID?

Question

Is it theorically possible to connect to a hidden wifi without giving the ESSID?

The way I connect to a hidden wifi requires to give an SSID (nmcli refuses to have a blank 802-11-wireless.ssid field).

 nmcli con add type wifi con-name <con name> ifname wlan0 ssid <SSID>
 nmcli con modify <con name> wifi-sec.key-mgmt wpa-psk
 nmcli con modify <con name> wifi-sec.psk <password>

Answer 1

Is not even theoretically possible to do this. You are trying to access you email, without knowing what is your mailserver or mail provider...

Knowing the SSID(or ESSID - i'll use this terms interchanged cause, with one you can identify the other) is the basic point to get a connection done. Is the way you identify where you want to "phisically" connect(i'm using phisically not to determine the antena hardware itself, but the medium that is being presented nearby through air).

Take a look at this excelent answer at Networking.stackexchange. Basically if you want to connect to a wifi network you need to catch a beacon with SSID information, or you need to send a probe request. I'm not counting here any method to discover hidden ssids, cause those will only be useful to identify the network you want...

How can you station possibly decide what ssid/essid to use, just based on your password?

Your best bet here is to connect using your bssid and this answer at askubuntu explains very well. Note that this setup will be valid inside a network where you have just ONE access point cause bssids are calculated based on AP mac address(and as you can see the example below quoted from that answer, Apolo III ssid has 3 bssid). You just need to adapt to your needs of wifi cipher being used:

Quoting the answer:

$ nmcli -f in-use,ssid,bssid,signal,bars  dev wifi
*  SSID               BSSID              SIGNAL  BARS 
*  Apollo III (TWC)   XX:XX:XX:XX:XX:XX  98      ▂▄▆█ 
   Chromecast8481     XX:XX:XX:XX:XX:XX  97      ▂▄▆█ 
   --                 XX:XX:XX:XX:XX:XX  94      ▂▄▆█ 
   Apollo III (1)     XX:XX:XX:XX:XX:XX  87      ▂▄▆█ 
   TWCWiFi            XX:XX:XX:XX:XX:XX  80      ▂▄▆_ 
   CableWiFi          XX:XX:XX:XX:XX:XX  80      ▂▄▆_ 
   TWCWiFi-Passpoint  XX:XX:XX:XX:XX:XX  80      ▂▄▆_ 
   Apollo III (1)     XX:XX:XX:XX:XX:XX  70      ▂▄▆_

The cli for the connection to the BSSID is:

$ nmcli d wifi connect XX:XX:XX:XX:XX:XX

Related Stuff:

• Understanding the Network Terms SSID, BSSID, and ESSID