Serial Diode

Generic wire protocol and implementation for one-way data transfer over UART serial.

Usage

General

The serial device can be specified with --device and baudrate with --baudrate. If device is unspecified, it will attempt to guess the correct device based on platform and name. If baudrate is unspecified, it defaults to 115200 Hz.

See --help for detailed usage information.

Send

Run diode send <path/to/file> to send <file>.

Receive

Run diode listen, which will listen forever. When it receives a valid payload, it will write it to out/<file> where <file> was specified in the payload metadata.

Note that on some systems this may need to be run as root to allow access to the serial port. It is generally preferable to add the user to the appropriate group with something similar to usermod -a -G uucp <username>.

Wire format

┌─────┬──────────┬─────────────┬──────┬─────┬───────┐
│ SOT │ metadata │ data_length │ data │ EXT │ crc32 │
└─────┴──────────┴─────────────┴──────┴─────┴───────┘

Here:

• metadata is 32 bytes,
• data_length is 8 bytes,
• data is data_length bytes,
• crc32 is 8 bytes,
• SOT and EXT are the bytes x02, x03,
• crc32 is the value of the CRC32 function acting on metadata || data.

Installation

Install in developer mode with make install_dev && source venv/bin/activate.

Install as user with make install.

Install from PyPI with pip install data-diode.

Install Bash completion with source bash_completion/diode.

Testing

Run make test.

For ad-hoc testing, socat -d -d pty,raw,echo=0 pty,raw,echo=0 can be useful to connect two virtual serial devices. If a physical serial device exists, connect with screen /dev/<device_name> [<baud_rate>] where <baud_rate> is likely 115200.