Established RecaptchaValidator

The `RecaptchaValidator` class is a concrete implementation of the new `IRequestValidator` (0272136). This accepts a token and an action, and validates them against reCAPTCHA's API. This takes advantage of the recently introduced `RecaptchaResponse` class to model the response from the reCAPTCHA API (3c0ad10).

Services/RecaptchaValidator.cs

@@ -0,0 +1,91 @@
+/*==============================================================================================================================
+| Author        Ignia, LLC
+| Client        GoldSim
+| Project       Website
+\=============================================================================================================================*/
+using System;
+using System.Net;
+using System.Net.Http;
+using System.Text.Json;
+using System.Threading.Tasks;
+using GoldSim.Web.Models.Recaptcha;
+using OnTopic.Internal.Diagnostics;
+
+namespace GoldSim.Web.Services {
+
+  /*============================================================================================================================
+  | CLASS: RECAPTCHA (REQUEST VALIDATOR)
+  \---------------------------------------------------------------------------------------------------------------------------*/
+  /// <summary>
+  ///   Validates that a given request is from a human.
+  /// </summary>
+  public class RecaptchaValidator: IRequestValidator {
+
+    /*==========================================================================================================================
+    | PRIVATE VARIABLES
+    \-------------------------------------------------------------------------------------------------------------------------*/
+    private readonly            string                          _secret;
+    private readonly            string                          _serviceUrl;
+    private static readonly     HttpClient                      _client                         = new();
+
+    /*==========================================================================================================================
+    | CONSTRUCTOR
+    \-------------------------------------------------------------------------------------------------------------------------*/
+    /// <summary>
+    ///   Initializes a new instance of the <see cref="RecaptchaValidator"/> with necessary dependencies.
+    /// </summary>
+    /// <returns>A new instance of the <see cref="RecaptchaValidator"/>.</returns>
+    public RecaptchaValidator(string secret) {
+      _secret                   = secret?? throw new ArgumentNullException(nameof(secret));
+      _serviceUrl               = "https://www.google.com/recaptcha/api/siteverify";
+    }
+
+    /*==========================================================================================================================
+    | IS VALID?
+    \-------------------------------------------------------------------------------------------------------------------------*/
+    /// <summary>
+    ///   Determines that the request is valid, given a <paramref name="requestToken"/>.
+    /// </summary>
+    public async Task<bool> IsValid(string requestType, string requestToken) {
+
+      /*------------------------------------------------------------------------------------------------------------------------
+      | Validate input
+      \-----------------------------------------------------------------------------------------------------------------------*/
+      Contract.Requires(requestToken, nameof(requestToken));
+
+      /*------------------------------------------------------------------------------------------------------------------------
+      | Retrieve value
+      \-----------------------------------------------------------------------------------------------------------------------*/
+      var uri                   = new Uri($"{_serviceUrl}?secret={_secret}&response={requestToken}");
+      var httpResponse          = await _client.GetAsync(uri).ConfigureAwait(false);
+
+      /*------------------------------------------------------------------------------------------------------------------------
+      | Validate response
+      \-----------------------------------------------------------------------------------------------------------------------*/
+      if (httpResponse.StatusCode != HttpStatusCode.OK) {
+        return false;
+      }
+
+      /*------------------------------------------------------------------------------------------------------------------------
+      | Validate score
+      \-----------------------------------------------------------------------------------------------------------------------*/
+      var jsonResponse          = await httpResponse.Content.ReadAsStringAsync().ConfigureAwait(false);
+      var recaptchaResponse     = JsonSerializer.Deserialize<RecaptchaResponse>(
+        jsonResponse,
+        new() {
+          PropertyNameCaseInsensitive = true
+        }
+      );
+
+      /*------------------------------------------------------------------------------------------------------------------------
+      | Validate response
+      \-----------------------------------------------------------------------------------------------------------------------*/
+      return
+        recaptchaResponse.Success &&
+        recaptchaResponse.Score >= 0.5 &&
+        recaptchaResponse.Action.Equals(requestType, StringComparison.Ordinal);
+
+    }
+
+  } // Class
+} // Namespace