libssh C SSH Server Example

A lightweight SSH honeypot/server implementation written in C using the libssh library. This project demonstrates low-level SSH server development for security research, network testing, and educational purposes.

Features

• Native C implementation for performance
• Multi-threaded connection handling with pthreads
• Password-based authentication
• Interactive shell session support
• Custom command handling
• Non-blocking channel I/O
• Clean session management and cleanup

Requirements

• GCC or compatible C compiler
• libssh development libraries
• pthread library (usually included with GCC)
• Linux/Unix environment (or WSL on Windows)

Installation

1. Clone the repository:

git clone https://github.com/vibheksoni/libssh-c-example.git
cd libssh-c-example

2. Install libssh development libraries:

Ubuntu/Debian:

sudo apt-get install libssh-dev

Fedora/RHEL:

sudo dnf install libssh-devel

macOS:

brew install libssh

3. Generate SSH host key:

mkdir ssh_keys
ssh-keygen -t rsa -b 2048 -f ssh_keys/rsa.key -N ""

Compilation

Compile the project using GCC:

gcc -o ssh_server main.c ssh.c user.c -lssh -lpthread

Or use the provided Makefile if available:

make

Usage

Run the SSH server with host, key path, and port:

./ssh_server 0.0.0.0 ./ssh_keys/rsa.key 2222

Connect using any SSH client:

ssh admin@localhost -p 2222

Default credentials:

• Username: admin
• Password: admin

Project Structure

libssh-c-example/
├── main.c              # Entry point and argument parsing
├── ssh.c               # SSH server configuration and connection handler
├── user.c              # User authentication and session management
├── headers/
│   ├── ssh.h          # SSH server function declarations
│   └── user.h         # User session function declarations
└── ssh_keys/          # Directory for SSH host keys
    └── rsa.key        # RSA private key for the server

Key Components

ssh.c

• SshConfig(): Initialize server configuration
• SshInit(): Set up SSH bind options
• SshStart(): Start listening for connections
• SshConnectionHandler(): Accept and handle incoming connections

user.c

• UserCreate(): Create new user session
• UserAuth(): Authenticate user credentials
• UserSessionInit(): Initialize SSH session and channel
• ClientHandler(): Main client interaction loop
• SshPrintf(): Write formatted output to SSH channel
• SshRead(): Read input from SSH channel

Security Notice

This is a honeypot/research tool intended for:

• Security research and testing
• Educational purposes
• Controlled lab environments
• Network security analysis

Do not expose this server to the public internet without proper security measures.

License

MIT License - See LICENSE file for details