courier

README

Courier

CourierCLI, an anonymous command-line messaging app. Messages are end-to-end encrypted using AES256 operating in GCM mode.

Important note:

Because courier is peer-to-peer, and currently requires peers to know a user's IP address to connect, using a VPN or Proxy is STRONGLY reccomended when running Courier.

Roadmap/ToDo

• Allow for multiple chats simulataneously (each chat having its own "tab")
  • Once this is implemented, implement peer discovery, allowing for more complete p2p functionality
• Add support for public "nodes" for peers to discover eachother on
• Add support for Windows

Installation and Setup

Linux Installation

• At the moment, there is no offical install script, so the app must be compiled manually
• Ensure you have golang installed
• Clone this repo
• Run the following command in this repo's directory:
  • go build .
• The directory will now contain a binary named courier. This is the executable for the Courier application. Run it from the command line to use the app.
• Optional: Run the following command to allow for calling courier anywhere
  • sudo mv courier /usr/bin/courier

Setup:

• Courier uses RSA encryption and signing for user veirification and key exchanges.
• To create a new RSA key pair:
  • Run courier init <keyPath>
  • The keyPath is the relative path to the directory you'd like to store your RSA keys for courier. This will generate new directories as needed.
  • The directory will now contain two files: pub.pem and prv.pem which will be used as your public and private keys respectively.

Usage:

Once you've logged in, you'll be greeted with a prompt for a command. As of 10/16/2024, there are 3 available commands

• connect
  • Takes a peer's IP address and attempts to connect to them
• await
  • Awaits incoming connections.
  • Note: In future versions, this command will be removed and will automatically run in the background
• clear:
  • Clears the screen
• read-archive :
  • Prompts the user for the password for the archive file at filepath and displays the decrypted chat archive if the password is correct.
• exit:
  • Exits courier

Logging in

When logging into courier you will recieve the following prompts

• Username:
  • This will be your display name. Can be anything you want as long as it is >= 64 characters in length.
• Color:
  • This will be the color your name is displayed in
  • Valid options:
    • Red
    • Green
    • Blue
    • Yellow
    • Cyan
    • Magenta
    • White
• Key path:
  • The path to the RSA key pair you'll be using for key transmission/message signing

Commands

Because courier is a CLI application, interaction other than sending messages is done via commands. To use a command, type ">" in the message entry immediately followed by the command (no space). More commands will be added in future builds

Current Commands

• clear:
  • Clears the chat history and clears all messages off screen
  • This only affects the client and has no effect on the peer's message history
• disconnect:
  • Terminates the connection with the peer
• peerid:
  • Returns the peer's user ID. Because Courier is P2P with no centralized infrastructure, these IDs are the only way to verify a peer's identity, so it's important to ensure your peer has the ID you expect them to have.
• archive <path> [rounds]:
  • Creates a password-protected archive of the chat, and stores it to the specified directory (creating new directories as needed). The archive's file name is based on the current time, and it is name as <HOUR>-<MINUTE>-<SECOND>.arc
  • Specifiying the number of rounds is optional. Rounds determines the number of rounds of hashing your password will undergo to create an encryption key.