Multi-Threaded File Server

This is a multi-threaded file server with secure user authentication and access control.

Features

• Secure user authentication with password hashing and salting (SHA-256)
• Role-based access control (read/write permissions)
• File upload and download functionality
• Multi-threaded client handling

---

Building the Server

To build the server, you'll need CMake (version 3.10 or higher), a C compiler, and OpenSSL development libraries.

Install Dependencies

On Ubuntu/Debian:

sudo apt-get install build-essential cmake libssl-dev

On CentOS/RHEL:

sudo yum install gcc gcc-c++ make cmake openssl-devel

Build

# Create a build directory
mkdir build
cd build

# Configure and build
cmake ..
make

# Run the server
./file_server

User Management

The server comes with a user management utility for creating and managing user accounts:

# Add a new user with read access
./user_manager -a username password read

# Add a new user with write access
./user_manager -a username password write

# List all users
./user_manager -l

# Delete a user
./user_manager -d username

Authentication Security

The system uses a secure authentication scheme:

• Passwords are never stored in plaintext
• Each password is hashed using SHA-256 with a unique random salt
• Salt values prevent rainbow table attacks
• User data is stored in the format: username:password_hash:salt:role

Client Commands

• upload <filename> - Upload a file to the server (requires write permission)
• download <filename> - Download a file from the server (requires read permission)