scar-chat/README.md

SCAR Chat Application

A cross-platform GUI chat client and server with SSL/TLS encryption, built in C++.

Features

Server (chat_server)

• Listens on TCP port 42317 with TLS/SSL encryption
• Multi-client support with broadcast messaging
• Uses OpenSSL for secure communication
• Linux/cross-platform compatible

Qt Client (chat_client_qt)

• Cross-platform GUI using Qt5/6 Widgets
• TLS/SSL encrypted connection to server
• Customizable UI:
  • Background color selector for all windows
  • Chat text color customization
  • Transparency/opacity slider (0-100%)
• Message history display
• Real-time message sending and receiving
• Linux/cross-platform compatible

Windows Client (chat_client_win)

• Native Win32 GUI client
• Same UI features as Qt client
• Windows-only build

Prerequisites

Linux / macOS

# Ubuntu/Debian
sudo apt-get install cmake qtbase5-dev libssl-dev build-essential

# macOS (Homebrew)
brew install cmake qt5 openssl

Windows

• Visual Studio 2019+ or MinGW
• CMake 3.16+
• Qt5/6 SDK
• OpenSSL for Windows (vcpkg or prebuilt binaries)

Building

Linux / macOS

1. Create and generate certificates:

   cd certs
   ./generate_certs.sh
   cd ..
   

2. Build the project:

   mkdir build
   cd build
   cmake ..
   make
   

3. Install (optional):

   make install
   

Windows

1. Generate certificates (use OpenSSL for Windows or WSL):

   cd certs
   # On Windows, use Git Bash or WSL to run generate_certs.sh
   # Or generate manually using OpenSSL
   cd ..
   

2. Build:

   mkdir build
   cd build
   cmake -G "Visual Studio 16 2019" ..
   cmake --build . --config Release
   

Running

Server

# Linux / macOS
./build/chat_server certs/server.crt certs/server.key

# Windows
.\build\Release\chat_server.exe certs\server.crt certs\server.key

The server will listen on localhost:42317.

Qt Client

# Linux / macOS
./build/chat_client_qt

# Windows (if built on Windows)
.\build\Release\chat_client_qt.exe

Connect to server by entering host/port and clicking "Connect".

Windows Client

# Windows only
.\build\Release\chat_client_win.exe

Customization Features

Background Color

• Click "BG Color" button to select background color for all windows
• Color choice is applied immediately

Text Color

• Click "Text Color" button to select chat text color
• Updates chat display in real-time

Transparency

• Use the transparency slider (0-100%) to adjust window opacity
• 0% = fully transparent, 100% = fully opaque

SSL/TLS Certificates

Generate Self-Signed Certificates

For development and testing:

cd certs

# Generate private key
openssl genrsa -out server.key 2048

# Generate certificate (valid for 365 days)
openssl req -new -x509 -key server.key -out server.crt -days 365 \
  -subj "/C=US/ST=State/L=City/O=SCAR/CN=localhost"

cd ..

Note: For production, use certificates signed by a trusted Certificate Authority (CA).

Ignoring Self-Signed Certificates

The Qt client is configured to ignore self-signed certificate errors during development:

socket->ignoreSslErrors();

For production, implement proper certificate validation.

Project Structure

scar-chat/
├── CMakeLists.txt          # Top-level CMake configuration
├── README.md               # This file
├── certs/                  # SSL certificates directory
│   └── generate_certs.sh   # Certificate generation script
├── src/
│   ├── server/
│   │   └── server.cpp      # TLS server (OpenSSL)
│   ├── qt_client/
│   │   └── main.cpp        # Qt GUI client
│   └── windows_client/
│       └── main_win.cpp    # Win32 GUI client
└── build/                  # Build output directory (created after cmake)

Troubleshooting

"Connection refused" error

• Ensure server is running on the same host/port
• Check firewall settings on port 42317

SSL/TLS errors

• Verify certificates exist in certs/ directory
• Regenerate certificates if expired or corrupted
• Ensure certificate and key files are readable

Qt not found during CMake

# Set Qt path explicitly
cmake -DQt5_DIR=/path/to/Qt5/lib/cmake/Qt5 ..

OpenSSL not found during CMake

# Set OpenSSL path explicitly (macOS example)
cmake -DOPENSSL_DIR=/usr/local/opt/openssl ..

Development Notes

• C++17 standard is required
• Qt5/6 for cross-platform GUI
• OpenSSL 1.1+ for TLS/SSL
• Threading used for non-blocking socket operations
• Message protocol: simple newline-delimited UTF-8 text

Security Considerations

• ✅ Uses TLS 1.2+ for encrypted communication
• ⚠️ Development mode: ignores self-signed certificate errors
• ⚠️ No user authentication implemented
• ⚠️ No message encryption at application level (relies on TLS)

For production use, implement:

• Proper certificate validation
• User authentication and authorization
• Message signing/verification
• Rate limiting and DoS protection

License

This project is provided as-is for educational and development purposes.