Guide to DevSecOps

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Setting Up .NET on Ubuntu Server ​

This guide walks you through installing .NET on Ubuntu Server, configuring your development environment, and implementing security best practices.

1. Prerequisites ​

Before installing .NET, ensure your system is up to date:

bash
sudo apt update
sudo apt upgrade -y

2. Installing .NET SDK ​

Add Microsoft package repository ​

bash
wget https://packages.microsoft.com/config/ubuntu/$(lsb_release -rs)/packages-microsoft-prod.deb -O packages-microsoft-prod.deb
sudo dpkg -i packages-microsoft-prod.deb
rm packages-microsoft-prod.deb

Install .NET SDK ​

bash
sudo apt update
sudo apt install -y apt-transport-https
sudo apt install -y dotnet-sdk-9.0  # Change version as needed

Verify installation ​

bash
dotnet --version

3. Development Environment Setup ​

Install essential tools ​

bash
sudo apt install -y git

Configure VS Code Remote Development (Optional) ​

If developing remotely:

  1. Install VS Code on your local machine
  2. Install the "Remote Development" extension pack
  3. Connect to your Ubuntu server via SSH
  4. Install C# extension in the remote VS Code instance

Creating your first .NET project ​

bash
mkdir ~/dotnet-projects
cd ~/dotnet-projects
dotnet new console -n MyFirstApp
cd MyFirstApp
dotnet run

4. Installing .NET for Production Environments ​

When deploying to production servers, you should install only the .NET Runtime instead of the full SDK. This reduces the attack surface and resource usage.

Understanding Runtime vs SDK ​

  • SDK: Includes everything needed for development (compiler, tools, libraries)
  • Runtime: Contains only components needed to run applications

Add Microsoft package repository (if not already added) ​

bash
wget https://packages.microsoft.com/config/ubuntu/$(lsb_release -rs)/packages-microsoft-prod.deb -O packages-microsoft-prod.deb
sudo dpkg -i packages-microsoft-prod.deb
rm packages-microsoft-prod.deb

Install .NET Runtime ​

For console or worker applications:

bash
sudo apt update
sudo apt install -y apt-transport-https
sudo apt install -y dotnet-runtime-9.0  # Change version as needed

For web applications (ASP.NET Core):

bash
sudo apt update
sudo apt install -y apt-transport-https
sudo apt install -y aspnetcore-runtime-9.0  # Change version as needed

Verify installation ​

bash
dotnet --list-runtimes

Running applications in production ​

bash
cd /path/to/application
dotnet YourApplication.dll

For production deployment, consider using a service manager like systemd:

bash
sudo nano /etc/systemd/system/your-app.service

Example service file:

[Unit]
Description=.NET Web Application
After=network.target

[Service]
WorkingDirectory=/path/to/application
ExecStart=/usr/bin/dotnet /path/to/application/YourApplication.dll
Restart=always
# Restart service after 10 seconds if the dotnet service crashes
RestartSec=10
KillSignal=SIGINT
SyslogIdentifier=your-app
User=www-data
Environment=ASPNETCORE_ENVIRONMENT=Production

[Install]
WantedBy=multi-user.target

Enable and start the service:

bash
sudo systemctl enable your-app.service
sudo systemctl start your-app.service
sudo systemctl status your-app.service

5. Security Best Practices ​

Secure your application ​

  1. Keep .NET updated:

    bash
    sudo apt update
sudo apt upgrade

  2. Use HTTPS in production:

    • Always configure SSL/TLS certificates
    • Use Let's Encrypt for free certificates

  3. Implement proper authentication:

    • Use ASP.NET Core Identity for user management
    • Consider OAuth/OpenID Connect for enterprise applications

  4. Data protection:

    • Use Entity Framework parameterized queries to prevent SQL injection
    • Implement proper input validation
    • Use Data Protection API for sensitive information

  5. Secure Docker containers (if using containerization):

    bash
    # Run containers with limited privileges
docker run --security-opt=no-new-privileges my-dotnet-app

  6. Network security:

    • Configure firewall rules with UFW
    bash
    sudo ufw allow ssh
sudo ufw allow 443/tcp  # HTTPS
sudo ufw enable

Secret management ​

  1. Use user secrets during development:

    bash
    dotnet user-secrets init
dotnet user-secrets set "ConnectionStrings:DefaultConnection" "your-connection-string"

  2. In production, use environment variables or a vault solution:

    • Azure Key Vault
    • HashiCorp Vault
    • Docker secrets

5. Development Guidelines ​

Code organization ​

  • Follow the Model-View-Controller (MVC) pattern for web applications
  • Use Clean Architecture principles
  • Organize code into small, focused classes with single responsibilities

Testing ​

bash
# Create a test project
dotnet new xunit -n MyApp.Tests
# Add a reference to your main project
dotnet add MyApp.Tests/MyApp.Tests.csproj reference MyApp/MyApp.csproj

CI/CD setup ​

  • Consider using GitHub Actions or Azure DevOps for CI/CD pipelines
  • Automate testing, building, and deployment processes

Performance optimization ​

  • Use async/await for I/O operations
  • Implement caching where appropriate
  • Profile your application to identify bottlenecks

6. Additional Resources ​

7. Troubleshooting ​

Common issues and solutions:

  1. SSL certificate issues: Install libnss3-tools package
  2. Database connection problems: Check firewall settings and connection strings
  3. Permission issues: Review file ownership and permissions in your project directory