signalblast

Signalblast is a tool to send encrypted messages anonymously over Signal to a subscriber list. The sender does not know who the subscribers in the list are, nor the subscribers know who the sender is.

A server is required to host the bot, find instructions on how the set it up below.

The idea for this bot came from Signalboost, which unfortunately is no longer alive.

Usage

Once the bot is up and running, several commands are available:

• !subscribe send this to sign up to the list
• !broadcast after subscribing any message preceded by this will be broadcasted to every subscriber
• !unsubscribe to stop receiving messages
• !help to be reminded of which commands are available
• !admin send a message only to the list admin, useful for getting technical support

Installation

Option 1: local python environment

• Set up signalbot as specified here
• Create a new virtual environment, uv is recommended
• Install with

  pip install signalblast

• Run via

  python -m signalblast.main

Option 2: docker compose

This will pull the project docker images from https://hub.docker.com/r/eradorta/signalblast

• Install docker.
• Configure signal-cli-rest-api as specified here
• Download the docker-compose.yml file.
• Create a data folder

  mkdir -p $HOME/.local/share/signalblast

• Define the relevant environment variables

  export DOCKER_TAG="The version of signalblast to run, can be latest"
  export SIGNALBLAST_PHONE_NUMBER="The phone number of the bot"
  export SIGNALBLAST_PASSWORD="The password for the admin"
  export SIGNALBLAST_HEALTHCHECK_RECEIVER="The contact or group to send health check messages"

• Run via docker compose:

  docker compose up

Development

• Set up docker and signalbot as specified in the installation section.
• Clone the repo
• Install uv
• Install the repo and the dependencies in a new virtual environment with uv sync
• Install the prek hook uv run prek install
• Run
  • Directly via uv run python -m signalblast.main
  • Via systemd with systemd/signalblast.service
    • Run once with the password in the env file.
    • From there one, the password is stored encrypted and it can be removed from the env file
• Optional: install signalbot as an editable dependency uv add --editable ../signalbot/

Docker compose

The docker/compose_build.sh and docker/compose_up.sh are provide for easier development.

Roadmap

• Make instructions clearer and add pictures to the readme
• Add unit testing