courier

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

• Add an in-app command pallete for recieving/creating connections
• Add more robust error handling
• Implement support for password protecting private keys
• Allow for archiving messages
• Add additional chat commands
• 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:
  • Create a new empty directory to store the keys in
  • Run courier init
  • When prompted for a "keyPath" enter the relative path to the directory you just created
  • 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

Logging in

When logging into courier you will recieve the following prompts

• Username:
  • This will be your display name. Can be anything you want
• 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.