server/src/Core/Utilities/CaptchaProtectedAttribute.cs

using Bit.Core.Context;
using Bit.Core.Exceptions;
using Bit.Core.Models.Api;
using Bit.Core.Services;
using Microsoft.AspNetCore.Mvc.Filters;
using Microsoft.Extensions.DependencyInjection;

namespace Bit.Core.Utilities
{
    public class CaptchaProtectedAttribute : ActionFilterAttribute
    {
        public string ModelParameterName { get; set; } = "model";

        public override void OnActionExecuting(ActionExecutingContext context)
        {
            var currentContext = context.HttpContext.RequestServices.GetRequiredService<ICurrentContext>();
            var captchaValidationService = context.HttpContext.RequestServices.GetRequiredService<ICaptchaValidationService>();

            if (captchaValidationService.RequireCaptchaValidation(currentContext))
            {
                var captchaResponse = (context.ActionArguments[ModelParameterName] as ICaptchaProtectedModel)?.CaptchaResponse;

                if (string.IsNullOrWhiteSpace(captchaResponse))
                {
                    throw new BadRequestException(captchaValidationService.SiteKeyResponseKeyName, captchaValidationService.SiteKey);
                }

                var captchaValid = captchaValidationService.ValidateCaptchaResponseAsync(captchaResponse,
                    currentContext.IpAddress).GetAwaiter().GetResult();
                if (!captchaValid)
                {
                    throw new BadRequestException("Captcha is invalid. Please refresh and try again");
                }
            }
        }
    }
}