File Transfer Server

A small HTTPS file transfer server written in C. It supports user registration/login, cookie-based sessions, and file uploads.

Features

• HTTPS Support: TLS/SSL encryption using OpenSSL
• User Authentication: Registration and login with secure password hashing (PBKDF2-SHA256)
• Session Management: Cookie-based authentication with cryptographically secure random session tokens
• File Upload: Support for multipart/form-data file uploads
• IPv4/IPv6 Support: Dual-stack networking
• Multiple Content Types: Serves HTML, CSS, JavaScript, images, PDFs, and more

Requirements

• GCC compiler
• OpenSSL development libraries
• Linux environment

Installation

1. Clone or download the repository

2. Install dependencies (Ubuntu/Debian):

sudo apt-get install libssl-dev

3. Generate SSL certificates:

openssl req -x509 -newkey rsa:2048 -nodes -keyout key.pem -out cert.pem -days 365

Note: the generated certificate is self-signed, so your browser will likely show a security warning when accessing https://localhost:8080.

4. Build the project:

make

Usage

Start the server:

./file_transfer

The server will listen on port 8080. Access it via:

• https://localhost:8080

Project Structure

├── Src/              # Source files
│   ├── file_transfer.c    # Main server implementation
│   ├── client_info.c      # Client connection management
│   └── cookie.c           # Cookie implementation
├── Inc/              # Header files
│   ├── client_info.h      # Client data structures
│   ├── users.h            # User authentication functions
│   └── cookie.h           # Session cookie management
├── Data/             # Persistent data storage
│   ├── users.txt          # User credentials
│   └── cookies.txt        # Active sessions
├── public/           # Web content
│   ├── *.html             # Public pages (login, register, home)
├── Makefile          # Build configuration
└── README.md         # This file

Routes

• GET / - Home page
• GET /login.html - Login page
• POST /login - User login
• GET /register.html - Registration page
• POST /register - User registration
• POST /upload - File upload (authenticated)

Security Features

• Password hashing with PBKDF2-SHA256 (10,000 iterations)
• 16-byte cryptographic salt per user
• 256-byte random session tokens, stored as 512-character hex cookies
• HTTPS/TLS encryption for all communications
• Session-based authentication

Development

Clean build artifacts:

make clean

Rebuild from scratch:

make re

Notes

• Default port: 8080
• User data persists in Data/users.txt
• Active sessions stored in Data/cookies.txt