ESP32 Sniffer

This project is using Espressif IoT Development Framework (ESP-IDF) and has been tested on ESP-WROOM-32 module and esp-idf v3.2.

An overview of the full project (i.e. ESP32 firmware, server and GUI) can be found here.

This firmware is written with the purpose to sniff Probe Request packets sent by smartphones that are looking for Wi-Fi connection. When the Wi-Fi connection is active on a smartphone, it will send in broadcast (in all channels frequencies) a probe request messagge asking if there are any free Wi-Fi or some known ones (i.e. the smartphone knows the password for that Wi-Fi). The ESP32 will sniff it and extract different types of information.

The following information is taken from each sniffed packet:

• MAC of the smartphone that has sent the request
• SSID of the wifi to which the request is sent
• The Timestamp of when the request was sent
• Received Signal Strength Indicator (RSSI)
• Sequence Number (SN)
• HT Capabilities Info

After each minute these informations are sent to a server and processed. Finally, it is possible to see the processed informations (smartphones real time location, smartphone frequency, etc.) through a GUI.

Demo

Table of Contents

• Firmware Overview
• ESP-IDF Environment Configuration
• Usage
• File Configuration
  • Variables Configuration
  • Add Customised Menu
• Components
• Resources

Firmware Overview

The firmware consits in two main threads/tasks:

• Sniffer Task

  • Sniff Probe Request packet and save infomation described above into a file.

• Wi-Fi Task

  • Each minute, take the information saved by the Sniffer Task and send it to the server.
  • A lock is used in order to manage critical section for I/O operations in the file.

The ESP32 is configured in WIFI_MODE_APSTA mode: i.e. it creates "soft-AP and station control block" and starts "soft-AP and station". Thanks to this, the ESP32 is able to sniff and send informations to the server at the same time avoiding to lose packets information while sending data.

Here is the full list of information fields that can be in a Probe Request (source IEEE 802.11-2012):

And here below a packet sniffed with Wireshark in which you can see, for each field, the number of bits and their position within the packet:

ESP-IDF Environment Configuration

This section might be outdated, checkout the official site for more info and for the latest guide on how to get started with ESP-IDF.

1. Setup Toolchain

   • Windows
   • Linux
   • Mac OS

2. Get ESP-IDF

   Besides the toolchain (that contains programs to compile and build the application), you also need ESP32 specific API / libraries.

   cd ~/esp git clone --recursive https://github.com/espressif/esp-idf.git

3. Checkout to version v3.x

   cd esp-idf git checkout release/v3.2

4. Setup path to ESP-IDF

   The toolchain programs access ESP-IDF using IDF_PATH environment variable. This variable should be set up on your PC, otherwise projects will not build.

   • Windows
   • Linux & Mac OS

5. Install the Required Python Packages

   python -m pip install --user -r $IDF_PATH/requirements.txt

Usage

1. Make sure you have exported the path

   export IDF_PATH=~/esp/esp-idf export PATH=$PATH:$HOME/esp/xtensa-esp32-elf/bin

2. Clone the repo

   git clone https://github.com/ETS-PoliTO/esp32-sniffer.git cd esp32-sniffer

3. Establish serial connection between ESP32 and your PC

   make menuconfig

   Go to Serial flasher config, then Default serial port and set the port in which ESP32 is connected

   Note that, if you are using a bridge, probably you need to download some driver:

   • CP210x

   • FTDI

     This provides a guide on how establish serial connection between ESP32 and PC.

4. Build code and flash the ESP32

   make all && make flash

5. See logs

   make monitor

File Configuration

The file /main/Kconfig.projbuild contains two different menus:

• SPIFFS (SPI Flash File System)

  It contains some important information about the SPIFFS partion:

  • SPIFFS Base address
  • SPIFFS Size
  • SPIFFS Logical block size
  • SPIFFS Logical page size

  SPIFFS is a file system that supports wear leveling, file system consistency checks and more.

• Configurations

  It contains different variables:

  • ESP32_ID: ID of the ESP32
  • WIFI_SSID: SSID of WiFi (network name)
  • WIFI_PASS: WiFi password (WPA or WPA2)
  • BROKER_ADDR: IP of the MQTT broker
  • BROKER_PSW: password of the MQTT broker
  • BROKER_PORT: port of the MQTT broker
  • CHANNEL: channel in which ESP32 will sniff PROBE REQUEST
  • SNIFFING_TIME: time of sniffing
  • etc...

Variables Configuration

In order to configure the variables above:

1. Open your terminal within the project folder and run

   make menuconfig

2. Select the menu you want to modify

3. Edit variables as you like

Add Customised Menu

You can also add different menus with different variables:

1. Open Kconfig.projbuild

2. Start a new menu

   menu YOUR_MENU_NAME

3. Add the variables you need

4. End menu

   endmenu

Components

• SPIFFS

  You need to create a partition table.

  SPIFFS components

• ESP32 MQTT

  It has been used ESP32 MQTT Library.

  MQTT documentation

• MD5

  Hash function used on sniffed packets in order to get a unique identifier.

Resources

• Official esp-idf git repo to see some examples and information about the used data structure.
• Latest Documentation version for Espressif IoT Development Framework.
• ESP32 forum to ask questions and find community resources.
• ESP32-IDF Documentation for browseable modules, namespaces, data structures and files.

Check also this demonstration video to see how ESP32 works.

Seneca

Longum iter est per praecepta, breve et efficax per exempla