nymstr-groupd

nymstr-groupd is a group chat server built on the Nym mixnet, providing privacy-preserving group messaging. It handles group creation and management, encrypted messaging, and real-time delivery over mixnet and Redis.

Features

• Anonymous Messaging: Clients connect to the Nym mixnet for privacy-preserving message transport.
• Group Management: Create public/private groups, join public groups, invite and approve members for private groups.
• Encrypted & Signed Messages: End-to-end encrypted and signed messages ensure confidentiality and integrity.
• Persistent Metadata: SQLite database for users, groups, memberships, and invites.
• Real-time Delivery: Redis Pub/Sub to broadcast messages to group members.
• Configurable Storage & Logging: Easy environment-based configuration for logs, database, keys, and Nym SDK storage.

Prerequisites

• Rust toolchain (Rust 1.70+)
• SQLite
• Redis server
• OpenSSL (for cryptographic operations)

Installation

git clone https://github.com/your_org/nymstr-groupd.git
cd nymstr-groupd
cargo build --release

Configuration

Configure the server via environment variables. The following variables are supported:

Variable	Default	Description
LOG_FILE_PATH	logs/groupd.log	Path to the log file (directories will be created)
DATABASE_PATH	storage/groupd.db	Path to the SQLite database
KEYS_DIR	storage/keys	Directory for storing encrypted key pairs
SECRET_PATH	secrets/encryption_password	File containing the encryption password
NYM_CLIENT_ID	groupd	Nym mixnet client identifier
NYM_SDK_STORAGE	storage/<NYM_CLIENT_ID>	Directory for Nym SDK storage
REDIS_URL	redis://127.0.0.1/	Redis connection URL

Quick start

Copy the example environment file and export all variables:

cp .env.example .env
export $(grep -v '^\s*#' .env | xargs)

Before starting, initialize the encryption password file:

mkdir -p "$(dirname "${SECRET_PATH:-secrets/encryption_password}")"
echo "YOUR_ENCRYPTION_PASSWORD" > "${SECRET_PATH:-secrets/encryption_password}"

# On first run the server will auto-generate its ECDSA keypair for signing replies
#+ using $KEYS_DIR/${NYM_CLIENT_ID}_*.pem

Running the Server

cargo run --release

The server will:

• Load environment variables from the environment
• Initialize logging to console and file
• Set up SQLite database and tables
• Prepare cryptographic key storage
• Connect to the Nym mixnet using nym-sdk
• Subscribe to Redis channels for group pub/sub

Listen for incoming JSON commands over the mixnet

Example Rust CLI client

An example CLI client is provided in examples/client.rs. It uses the Nym mixnet to send JSON actions to the server and print incoming messages.

# after exporting environment variables (see Quick start)
cargo run --example client -- <server_nym_address>

API: JSON Actions

Clients communicate with the server by sending JSON messages over the Nym mixnet. Each message must include an "action" field. Below are the supported actions:

connect

Subscribe to group channels for message delivery.

{ "action": "connect" }

createGroup

Create a new group.

{
  "action": "createGroup",
  "groupName": "My Group",
  "isPublic": true,
  "isDiscoverable": false
}

Response: createGroupResponse with groupId.

joinGroup

Join a public group.

{
  "action": "joinGroup",
  "groupId": "<UUID>"
}

Response: joinGroupResponse with status.

inviteGroup

Invite a user to a private group (admin only).

{
  "action": "inviteGroup",
  "groupId": "<UUID>",
  "username": "alice"
}

Response: inviteGroupResponse with status.

approveGroup

Approve an invited user to join (admin only).

{
  "action": "approveGroup",
  "groupId": "<UUID>",
  "username": "alice"
}

Response: approveGroupResponse with status.

sendGroup

Send an encrypted message to group members.

{
  "action": "sendGroup",
  "groupId": "<UUID>",
  "ciphertext": "<encrypted_payload>"
}

Response: sendGroupResponse with status.

Logging

Logging is provided by [fern] with colored output in the console and timestamped entries in the log file (see LOG_FILE_PATH).

Persistence

Database schema is defined in src/db_utils.rs, with tables for users, groups, group_members, and group_invites.