How to restrict Wi-Fi sharing via Mobile Hotspot ?

JKnott

That I couldn't tell you, as I've never done it. But if that's done, it will immediately kill DHCP, DNS and everything else. Others here can tell you more about adjusting TTL.

johnpoz

@jknott said in How to restrict Wi-Fi sharing via Mobile Hotspot ?:

Why not set the incoming TTL to 1?.

incoming to where? Pfsense?

This board is about pfsense - incoming would mean to what we are here talking about pfsense.

Setting the ttl to 1 would be leaving pfsense back to the client..

clients to internet ttl 127---> pfsense --> out to isp ttl 126

return traffic some ttl by time it gets to pfsense ---> to client ttl 1

When it hits the sharing device, it should not pass it on to the client..

But in that setup pfsense processed all the traffic.. Why not just block it here

client to internet ttl 127 ---> pfsense = DROP..

Neither option is full proof, and can lead to issues. You don't know, the sharing device might already mangle the ttl, so you don't see an odd ttl, they might set it to 255 as it leaves.

Or maybe the sharing devices says hey I don't care if the ttl is 1, Im going to pass it on to my client anyway..

Either way there is really no way to do this currently in pfsense. You could do some dropping of traffic in snort when you see odd ttl, or you could alert so you know hey this IP might be sharing the connection. This would the lease likely to cause any issues. But let you know IP is possible sharing the connection.

But I am not aware of way you could do anything with the traffic as it is returning to the client from pfsense.

There for sure is no way to do this easy in the gui. If the request is to be able to mangle ttls, or drop ttls that don't meet some criteria - that should be a feature request or a bounty..

stephenw10

We have never seriously considered adding this in the past because most people who come here asking about it are really asking: 'please help me break my providers terms of service so I can avoid paying them'. That's hard to support!

Charging per device has always seem pretty pointless to me anyway. Just set data and bandwidth limits and let people use that however they want.

Steve

mcury

@stephenw10 Something like this would be enough if the TTL from devices reaching my pfsense interface is 64, and my network is 192.168.10.0/27 ?

alert tcp 192.168.10.0/27 any -> any any (ttl:"63"; msg: "connection share"; sid:1; rev:1;)

I wouldn't download any other rules, Snort would run with custom rules only.

JKnott

@johnpoz

Incoming from the 'net and being forwarded to the LAN. If it leaves pfsense with TTL 1, it can't be forwarded to hotspot devices, as the TTL will decrement to 0.

NogBadTheBad

@mcury said in How to restrict Wi-Fi sharing via Mobile Hotspot ?:

@stephenw10 Something like this would be enough if the TTL from devices reaching my pfsense interface is 64, and my network is 192.168.10.0/27 ?

alert tcp 192.168.10.0/27 any -> any any (ttl:"63"; msg: "connection share"; sid:1; rev:1;)

I wouldn't download any other rules, Snort would run with custom rules only.

Your snort logs will fill up with that, have a look at the rule I posted further up.

It logs 1 occurance every 5 mins.

mcury

@nogbadthebad Great, I did read this thread and I don't know how I missed that.
Thanks :)

mcury

It works, I just tested using Suricata.
You can disable all active rules, disable promiscuous mode and create that custom rule.

invoker

@mcury do you have a tutorial for that sir?

mcury

@invoker said in How to restrict Wi-Fi sharing via Mobile Hotspot ?:

@mcury do you have a tutorial for that sir?

I did like this:
1- Install Suricata
2- Disable all active rules if you don't need them, disable promiscuous mode and create a custom rule like mentioned by the user @NogBadTheBad

alert ip 172.16.7.0/24 any -> !$HOME_NET any (msg: "Possible hotspot TTL 63"; threshold:type limit, track by_src, count 1, seconds 300; ttl:63; sid:2000001;rev:1;classtype:misc-activity;)

Change 172.16.7.0/24 by your local subnet and test.

Each OS uses a different OS, Windows if I'm not mistaken goes with 128, so you should create a rule to alert or drop when it sees a 127 TTL, Linux and Android uses 64, so you could create another rule to alert or drop when it sees a 63 TTL.

NogBadTheBad

If you are creating multiple rules for different ttl lengths remember to increment the sid: value for each rule.