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dnc - Distributed Netcat

Introduction

dnc is a versatile command-line tool designed to facilitate network communication across a Distributed Hash Table (DHT) network. It mirrors the functionality of the traditional nc (netcat) utility, enabling users to initiate TCP connections and create sockets on remote devices within a DHT network framework.

Main Features:

  • Initiates TCP connections on remote devices.
  • Facilitates peer-to-peer network connectivity within a DHT network.
  • Incorporates TURN (Traversal Using Relays around NAT) server support for effective NAT traversal.
  • Manages identities for enhanced security during DHT network interactions.

Connection Process

  1. Launch Server and Share Public ID (Server-side): The server must be launched, and its public ID (hash key) should be shared with the clients who want to connect to it.
  2. Initiate Connection and Request Remote Socket (Client-side): The client starts a peer-to-peer connection within the DHT network using the server's public ID and requests the server to open a socket at the specified <ip> and <port>.
  3. Check Certificate: If anonymous mode is off, the server verifies the client's certificate to ensure it matches the server’s CA. If anonymous mode is on, no certificate check is performed.
  4. Authorize Request: The server checks if the requested <ip>:<port> is authorized based on its rules.
  5. Create Socket:
    • If Authorized: The server opens a socket at the specified <ip>:<port> and links it to the DHT socket.
    • If Not Authorized: The server rejects the connection.

Usage Options

dnc supports a range of command-line arguments:

  • -h, --help: Display help information and exit.
  • -v, --version: Show the version of the program.
  • -P, --port [PORT]: Define the port for socket creation.
  • -i, --ip [IP]: Define the IP address for socket creation.
  • -l, --listen: Launch the program in listening mode.
  • -b, --bootstrap [ADDRESS]: Set the bootstrap node.
  • -t, --turn_host [ADDRESS]: Define the TURN server host.
  • -u, --turn_user [USER]: Define the TURN server username.
  • -w, --turn_pass [SECRET]: Define the TURN server password.
  • -r, --turn_realm [REALM]: Specify the TURN server realm.
  • -c, --certificate [FILE]: Specify the Certificate.
  • -p, --privateKey [FILE]: Provide a private key.
  • -d, --configuration [FILE]: Define the dnc configuration with a YAML file path.
  • -a, --anonymous: Activate anonymous connection mode.
  • -vv, --verbose: Enable verbose mode.

For additional options, use the -d flag with a YAML configuration file:

dnc -d <YAML_FILE> <PEER_IDENTIFIER>

Note: If anonymous mode is off, the server's CA must be shared with the client.

The authorized services <ip>:<port> can only be specified in the YAML configuration file. If none are specified, the server will accept all connections.

Establishing SSH Connections

To facilitate SSH connections to a remote device, dnc establishes a DHT network connection followed by socket creation on port 22 by default, assuming an OpenSSH server is operational.

Prerequisites

Setup the dnc Service

To initiate, generate a certificate authority and a server certificate:

sudo dhtnet-crtmgr --setup -o /usr/local/etc/dhtnet/

The server will cache some values in /var/run/dhtnet. If this must be changed, you can remove the line Environment="DHTNET_CACHE_DIR=/var/run/dhtnet" in dnc.service.in. Then, launch the dnc service:

systemctl start dnc.service

Obtain the user identifier with the following command:

dhtnet-crtmgr -a -p <privateKey_path> -c <cert_path>

For the server, use:

dhtnet-crtmgr -a -c /usr/local/etc/dhtnet/id/id-server.crt -p /usr/local/etc/dhtnet/id/id-server.pem

Client Connection

To establish a secure connection from the client side, it's necessary to generate a certificate authority (CA) and a certificate. Execute the following commands to set up your identity:

dhtnet-crtmgr -o <repo_ca> -n ca
dhtnet-crtmgr -o <repo_crt> -n certificate -c <repo_ca>/ca.crt -p <repo_ca>/ca.pem

Replace <repo_ca> with the directory path for storing the CA files and <repo_crt> with the path for the client certificate files. Update your YAML configuration file to include <repo_crt>/certificate.pem as the privateKey and <repo_crt>/certificate.crt as the certificate.

To integrate dnc with your SSH workflow, append the following configuration to your SSH configuration file (~/.ssh/config), enhancing the utility of SSH through dnc:

Host dnc/*
    IdentityFile /home/<local_user>/.ssh/<key>.pub
    ProxyCommand dnc -d /path/to/yaml/config $(basename %h)

This setup allows you to use the "dnc" alias for seamless SSH connections to remote servers. Simply replace <peer_identifier> with the actual server identifier and <ssh_remote_user> with the intended SSH username when initiating a connection:

ssh <ssh_remote_user>@dnc/<peer_identifier>

For exemple:

ssh mypeer@dnc/2f4975e7b11a0908bd400b27130fe9a496d0f415