Sneaky printer - Page 1
Forum section: electronics / general

author: PerranOak
author_rank: Frequent Contributor
timestamp: June 13, 2020, 10:03:41 am
content: I've just installed my first wifi printer (Canon MG5750). All is working well.However, I've just realised that it is connected to my router without my having to give it or the setup prog, the password even though it need a password to access - or so I thought!How can this be?Is my router secure?

author: fordem
author_rank: Regular Contributor
timestamp: June 13, 2020, 02:34:48 pm
content: Since you haven't told us exactly how you set the printer up, we can only guess.First - many printers allow you to connect to them through "WiFi direct" - with WiFi direct, as the name suggests, the printer and the PC are connected directly to one another, without the printer being connected to the WiFi network itself.Second - WiFi security takes many forms, MAC filtering, WEP/WPA encryption, etc., - if we assume WPA (or one of it's variants), as this is the most commonly used, then the only way for a device to be connected is to have the encryption key entered, either manually, or via some sort of automated mechanism, for example the WPS system that many consumer grade routers have (a push button on the router).It is also possible, if you are running the setup program from a device already connected to the WiFi network (which means the encryption key has already been entered), to export the key - this is commonly done with IoT devices, as an example, I've never entered a WiFi encryption key into my Samsung Smart watch, yet it connects to every WiFi network that my smart phone knows, because the watch is synced to the phone, I've also never entered in encryption keys into my current smart phone - when I upgraded from the previous phone, whatever WiFi networks had been configured on the old phone were automatically configured on the new phone.Is your router secure? Sorry - I'm still trying to create an ip stack for my crystal ball - it's proving to be a little more challenging than I first thought.

author: PerranOak
author_rank: Frequent Contributor
timestamp: June 14, 2020, 09:05:23 am
content: Sorry for my half-@rsed post. Crystal ball, yes! If you solve it, I'll buy one!I downloaded the Canon install prog and ran it and a PC. It found the printer on the network (i.e. connected to the router which I can see on the router's "management" page) and simply went ahead an set it all up.The router uses WPA2 and everything else needed the key. I guess it means that the PC exported the key ... sneaky!.

author: PA0PBZ
author_rank: Super Contributor
timestamp: June 14, 2020, 09:30:09 am
content: Quote from: PerranOak on June 14, 2020, 09:05:23 amHmm... How can the PC send the key to the printer while it's not yet connected to the network?

author: PerranOak
author_rank: Frequent Contributor
timestamp: June 14, 2020, 02:13:29 pm
content: Oh yeah?

author: Twoflower
author_rank: Frequent Contributor
timestamp: June 14, 2020, 03:03:47 pm
content: Sending data to a not-connected device isn't that complicated. The side-channel to go is the packet fame length. You write a program that creates two kind of broadcast frames a short one and a long one. Now you can morse that data over the air. For this the PC don't need to be in the WLAN itself but in the same network as the AP. The receiver scans through all WLANs it see and looks for such kind of frames. It's used widely for many Io(s)T to get these devices into the network.Obviously to do this the PC needs to know the SSID and the WLAN password. Most likely it uses the WLAN itself. And here comes the very interesting question: Can any software just ask the OS to provide the WLAN password?Edit: Obviously Windows let you check the passwords very willingly. Only using the PowerShell, no other SW is needed:https://www.howtogeek.com/426257/how-to-see-all-your-pcs-saved-wi-fi-passwords/

author: PA0PBZ
author_rank: Super Contributor
timestamp: June 14, 2020, 03:43:40 pm
content: I've been reading a bit and Canon calls it "cableless setup", where your PC makes a direct connection to the printer to send it the WiFi setup.And yes, any software can read the keys

author: fordem
author_rank: Regular Contributor
timestamp: June 15, 2020, 11:26:38 pm
content: Quote from: PA0PBZ on June 14, 2020, 09:30:09 amThere are a number of different ways you can go about this ...Many WiFi enabled printers are configured "out of the box" to create an "adhoc" WiFi network (one without an access point), they advertise themselves as if they are an access point, and allow any device to connect - assuming you have a smart phone, go into the WiFi setup and look for networks to connect to, in many residential neighborhoods and/or office environments you'll see something like HP-Setup-62-Officejet 7610 (which is my printer on my network, but you get the idea)The setup software will look for these "networks", ask if that is the printer you are setting up and then connect to and configure it - you can actually connect to and configure a printer that does not belong to you.Many WiFi enabled printers also support a feature known as WiFi direct and as long as you are within WiFi range of the printer you can configure your computer to connect directly to the printer and use it that way, without the printer actually being connected to the WiFi network.