Refactoring

AMWD.Common.AspNetCore/Attributes/GoogleReCaptchaAttribute.cs

@@ -0,0 +1,131 @@
+using System;
+using System.Collections.Generic;
+using System.Net.Http;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Configuration;
+using Newtonsoft.Json;
+
+namespace Microsoft.AspNetCore.Mvc.Filters
+{
+	/// <summary>
+	/// Custom filter attribute to use Google's reCaptcha (v3).
+	/// Usage: [ServiceFilter(typeof(GoogleReCaptchaAttribute))]
+	/// </summary>
+	public class GoogleReCaptchaAttribute : ActionFilterAttribute
+	{
+		/// <summary>
+		/// The error key used in <see cref="ActionContext.ModelState"/>.
+		/// </summary>
+		public const string ErrorKey = "GoogleReCaptcha";
+
+		/// <summary>
+		/// The key used in forms submitted to the backend.
+		/// </summary>
+		public const string ResponseTokenKey = "g-recaptcha-response";
+
+		/// <summary>
+		/// The key used in <see cref="Http.HttpContext.Items"/> to transport the score (0 - bot, 1 - human).
+		/// </summary>
+		public const string ScoreKey = "GoogleReCaptchaScore";
+
+		private const string VerificationUrl = "https://www.google.com/recaptcha/api/siteverify";
+
+		private readonly string privateKey;
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="GoogleReCaptchaAttribute"/> class.
+		/// </summary>
+		/// <remarks>
+		/// appsettings.json:
+		/// <br/>
+		/// <code>
+		/// {<br/>
+		///   [...]<br/>
+		///   "Google": {<br/>
+		///     "ReCaptcha": {<br/>
+		///       "PrivateKey": "__private reCaptcha key__",<br/>
+		///       "PublicKey": "__public reCaptcha key__"<br/>
+		///     }<br/>
+		///   }<br/>
+		/// }
+		/// </code>
+		/// <br/>
+		/// The score from google can be found on HttpContext.Items[GoogleReCaptchaAttribute.ScoreKey].
+		/// </remarks>
+		/// <param name="configuration">The application configuration.</param>
+		public GoogleReCaptchaAttribute(IConfiguration configuration)
+		{
+			privateKey = configuration.GetValue<string>("Google:ReCaptcha:PrivateKey");
+		}
+
+		/// <summary>
+		/// Executes the validattion in background.
+		/// </summary>
+		/// <param name="context">The action context.</param>
+		/// <param name="next">The following action delegate.</param>
+		/// <returns>An awaitable task.</returns>
+		public override async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
+		{
+			await DoValidation(context);
+			await base.OnActionExecutionAsync(context, next);
+		}
+
+		private async Task DoValidation(ActionExecutingContext context)
+		{
+			if (string.IsNullOrWhiteSpace(privateKey))
+				return;
+
+			if (!context.HttpContext.Request.HasFormContentType)
+				return;
+
+			var token = context.HttpContext.Request.Form[ResponseTokenKey];
+			if (string.IsNullOrWhiteSpace(token))
+			{
+				context.ModelState.TryAddModelError(ErrorKey, "No token to validate Google reCaptcha");
+				return;
+			}
+
+			await Validate(context, token);
+		}
+
+		private async Task Validate(ActionExecutingContext context, string token)
+		{
+			using var httpClient = new HttpClient();
+			var param = new Dictionary<string, string>
+			{
+				{ "secret", privateKey },
+				{ "response", token }
+			};
+			var response = await httpClient.PostAsync(VerificationUrl, new FormUrlEncodedContent(param));
+			string json = await response.Content.ReadAsStringAsync();
+
+			var result = JsonConvert.DeserializeObject<Response>(json);
+			if (result?.Success != true)
+			{
+				context.ModelState.TryAddModelError(ErrorKey, "Google reCaptcha verification failed");
+				context.HttpContext.Items[ScoreKey] = null;
+			}
+			else
+			{
+				context.HttpContext.Items[ScoreKey] = result.Score;
+			}
+		}
+
+		private class Response
+		{
+			public bool Success { get; set; }
+
+			public decimal Score { get; set; }
+
+			public string Action { get; set; }
+
+			[JsonProperty("challenge_ts")]
+			public DateTime Timestamp { get; set; }
+
+			public string Hostname { get; set; }
+
+			[JsonProperty("error-codes")]
+			public List<string> ErrorCodes { get; set; }
+		}
+	}
+}