basic questions about sniffing 802.15.4

Questions, comments, issues about the Wireshark Bridge go here.

basic questions about sniffing 802.15.4

Postby neverdie » Thu Jun 12, 2014 11:46 pm

I'm attempting to use the long range freakduino to sniff packets being sent by a wireless soil moisture sensor (SMS) that allegedly uses the same Atmel transceiver chip as the freakduino.

I'm starting the process by putting the freakduino into promiscuous mode and just dumping whatever it finds to the serial terminal (as described in the wireshark bridge tutorial). That didn't find anything using the default OQPSK, so I'm now re-running it in BPSK mode.

The SMS transmits every 10 minutes, but so far (after more like 20 minutes) I haven't received anything in BPSK mode either.

1. If it turns out that the SMS is using Atmel's encryption (and I'm hoping that it isn't), would I at least be seeing some encrypted gibberish on the serial terminal, or would it not display anything at all?

2. Will a freakduino receiving in promiscuous mode pickup whatever is sent over any channel, or do I have to manually switch from channel to channel until I hit on the channel that the SMS is using? If the latter case, what channel does the freakduino default to?

What else might I be forgetting to do that might explain why I'm not receiving the SMS signal?
neverdie
 
Posts: 33
Joined: Thu Jun 12, 2014 10:11 pm

Re: basic questions about sniffing 802.15.4

Postby neverdie » Thu Jun 12, 2014 11:51 pm

By the way, below is the code I'm now running. It's taken from the tutorial. The only modification was in the setup loop to switch to BPSK for receiving.

// Freakduino receiver code

#include <chibi.h>

void setup()
{
Serial.begin(57600);
chibiInit();
chibiSetShortAddr(5);
chibiSetMode(3); // set to BPSK
}


void loop()
{
// Check if any data was received from the radio. If so, then handle it.
if (chibiDataRcvd() == true)
{
byte len, buf[100];

len = chibiGetData(buf);
if (len == 0) {
return; // if no len, its a dupe packet. discard.
}
else {
Serial.print("Message: ");
Serial.println((char *)buf);
}
}
}
neverdie
 
Posts: 33
Joined: Thu Jun 12, 2014 10:11 pm

Re: basic questions about sniffing 802.15.4

Postby akiba » Thu Jun 12, 2014 11:52 pm

You have to make sure the device is in promiscuous mode, using the same modulation, and also on the same channel as the transmitting device. If those are all cool, then you should be able to see data from the Atmel device. From what it sounds like to me, you probably need to change your channel settings if you're not getting any data. I'd probably initially assume Atmel is using OQPSK which is the default and fastest modulation mode.
Akiba
Akiba
Freaklabs
Twitter: @freaklabs
Blog: http://www.freaklabs.org
Shop: http://www.freaklabsstore.com
akiba
 
Posts: 64
Joined: Fri Aug 30, 2013 1:07 am

Re: basic questions about sniffing 802.15.4

Postby neverdie » Fri Jun 13, 2014 12:04 am

OK, I'll try that. Meanwhile, in parallel to that, do you happen to know the answer to question #1, regarding the effect on the receiver of possible Atmel encryption? Does Atmel's transceiver encrypt just the data payload, or does it encrypt the entire frame (in which case maybe the receiver rejects it, thinking it's total garbage?)
neverdie
 
Posts: 33
Joined: Thu Jun 12, 2014 10:11 pm

Re: basic questions about sniffing 802.15.4

Postby akiba » Fri Jun 13, 2014 3:01 am

Just the payload. The headers are plaintext.
Akiba
Freaklabs
Twitter: @freaklabs
Blog: http://www.freaklabs.org
Shop: http://www.freaklabsstore.com
akiba
 
Posts: 64
Joined: Fri Aug 30, 2013 1:07 am


Return to FreakLabs Software - Wireshark Bridge

Who is online

Users browsing this forum: No registered users and 1 guest
cron