FoxLearn.AspNetCore.Captcha 1.0.1

🔷 FoxLearn.AspNetCore.Captcha

FoxLearn.AspNetCore.Captcha is a lightweight and customizable CAPTCHA generator for ASP.NET Core applications. It helps protect your forms from automated bots by generating image-based CAPTCHA challenges.

✅ Features

• ⚙️ Simple integration with ASP.NET Core

• 🔐 Session-based CAPTCHA validation

• 🖼️ Generates image CAPTCHAs on-the-fly

• 🎛️ Customizable via options

• 🧩 Supports MVC & Razor Pages

📥 Installation

Install via the .NET CLI:

dotnet add package FoxLearn.AspNetCore.Captcha

Or via the NuGet UI in Visual Studio by searching for FoxLearn.AspNetCore.Captcha

📦 Usage

1. Configure Services in Program.cs or Startup.cs

var builder = WebApplication.CreateBuilder(args);

...

builder.Services.AddCaptcha();

builder.Services.AddControllersWithViews();

builder.Services.AddSession(options =>
{
    options.IdleTimeout = TimeSpan.FromMinutes(10);
    options.Cookie.HttpOnly = true;
    options.Cookie.IsEssential = true;
});

var app = builder.Build();

app.UseSession();
...

2. Create a CAPTCHA Controller

public class CaptchaController : Controller
{
    private readonly ICaptchaGenerator _captchaGenerator;

    public CaptchaController(ICaptchaGenerator captchaGenerator)
    {
        _captchaGenerator = captchaGenerator ?? throw new ArgumentNullException(nameof(captchaGenerator));
    }

    public FileResult Image()
    {
        var (imageData, text) = _captchaGenerator.GenerateCaptcha();
        HttpContext.Session.SetString("CaptchaCode", text);
        return File(imageData, "image/png");
    }

    [AcceptVerbs("Get", "Post")]
    public IActionResult Validate(string captcha)
    {
        if (!string.IsNullOrEmpty(captcha))
        {
            string? code = HttpContext.Session.GetString("CaptchaCode");
            if (code != null)
            {
                if (string.Equals(code, captcha, StringComparison.OrdinalIgnoreCase))
                {
                    HttpContext.Session.Remove("CaptchaCode"); // Prevent replay attacks
                    return Json(data: true);
                }
            }
        }
        return Json(data: false);
    }
}

🧪 Sample View

<form asp-controller="Home" asp-action="Submit" method="post">
    <img src="/Captcha/Image" alt="Captcha" />
    <input type="text" name="captcha" required />
    <button type="submit">Submit</button>
</form>

🔐 Validation Tips

• CAPTCHA text is stored in session under "CaptchaCode".

• Always remove it from session after successful validation to prevent replay attacks.

• Combine with client-side validation for a better UX.

🔒 License

This project is licensed under the MIT License. Free for personal and commercial use.