comet

A simple Communication Eavesdropping Tool.

comet is a tool I developed to fit some of my needs while performing hardware security assessments. Its main goal is to help sniffing UART communications, for instance between a microcontroller and a modem.

comet will automatically save the captured data in two formats:

1. The raw line data as received
2. The individual lines captured in a JSON file (the raw bytes are encoded to a hex string)

By default, it will try to decode the data before displaying it to the console. If it fails to do so, the data is encoded to a hex string before being displayed.

[*] session: comet_20220206_185814
[*] port 1: /dev/tty.usbmodem
[*] baudrate for port 1: 115200
[*] start listening on port 1...
[<][2022-02-06 18:58:14.245977 UTC] Hello world!
[<][2022-02-06 18:58:14.622941 UTC] deadbeef
[<][2022-02-06 18:58:14.661773 UTC] Hello world!
[<][2022-02-06 18:58:15.037780 UTC] deadbeef
[<][2022-02-06 18:58:15.076815 UTC] Hello world!
[<][2022-02-06 18:58:15.452969 UTC] deadbeef

comet can also handle two different "sources" (port 1 and 2) and will multiplex them (Note: be aware there is no guaranty on the order). This allows to sniff on both RX and TX simultaneously.

Getting started

After having cloned this repo and cd into it, you can install comet by issuing:

$ cargo install --path .

Simple usage

In its simplest usage (listening on a port with all default parameters):

$ comet -p /dev/tty.port

This will listen on /dev/tty.port with a baudrate of 115200 bd/s, and will save the two resulting files in a folder comet_yyyymmdd_hhmmss.

Usage

USAGE:
    comet [OPTIONS]

OPTIONS:
        --baud <baud>                    Baudrate for port [default: 115200]
        --baud2 <baud2>                  Baudrate for port 2 [default: 115200]
        --common-baudrates               List common baudrates
    -h, --help                           Print help information
        --list-ports                     List available TTY ports
        --no-colour                      Do not display colours
        --no-direction                   Do not display message direction information
        --no-timestamp                   Do not display timestamps
        --nout                           Do not save captured data to files
    -p, --port <port>                    Port 1
        --port2 <port2>                  Port 2
        --session-name <session-name>    Name of the capture session
    -V, --version                        Print version information

Additional functionalities

comet comes with two little "utils": one to list the available ports and one to display a table of the most common baudrates. I have added those functionalities because I often found myself having to do it during an assessment (for instance when the baudrates is not known, but the bit duration is).

List available port

$ comet --list-ports

Common baudrates

$ comet --common-baudrates

Result:

$ comet --common-baudrates
+--------+--------------+
| Bauds  | Bit duration |
+--------+--------------+
| 50     | 20.000 ms    |
+--------+--------------+
| 75     | 13.333 ms    |
+--------+--------------+
| 110    | 9.091 ms     |
+--------+--------------+
...

Contributing

Any contribution to the tool is welcome!

Writing this tool was also for me a way to try out rust and as such, any contribution to the code quality (to make it more rustacean for instance) is more than welcome!