/BlogEngine/BlogEngine.NET/App_Code/Extensions/Recaptcha/RecaptchaValidator.cs

// Copyright (c) 2007 Adrian Godong, Ben Maurer

// Permission is hereby granted, free of charge, to any person obtaining a copy

// of this software and associated documentation files (the "Software"), to deal

// in the Software without restriction, including without limitation the rights

// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

// copies of the Software, and to permit persons to whom the Software is

// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in

// all copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

// THE SOFTWARE.



// Adapted for dotnetblogengine by Filip Stanek ( http://www.bloodforge.com )



namespace Recaptcha

{

    using System;

    using System.IO;

    using System.Net;

    using System.Net.Sockets;

    using System.Text;

    using System.Web;



    /// <summary>

    /// Calls the reCAPTCHA server to validate the answer to a reCAPTCHA challenge. Normally,

    ///     you will use the RecaptchaControl class to insert a web control on your page. However

    /// </summary>

    public class RecaptchaValidator

    {

        #region Constants and Fields



        /// <summary>

        /// The verify url.

        /// </summary>

        private const string VerifyUrl = "http://api-verify.recaptcha.net/verify";



        /// <summary>

        /// The remote ip.

        /// </summary>

        private string remoteIp;



        #endregion



        #region Properties



        /// <summary>

        /// Gets or sets Challenge.

        /// </summary>

        public string Challenge { get; set; }



        /// <summary>

        /// Gets or sets PrivateKey.

        /// </summary>

        public string PrivateKey { get; set; }



        /// <summary>

        /// Gets or sets RemoteIP.

        /// </summary>

        /// <exception cref="ArgumentException">

        /// </exception>

        public string RemoteIP

        {

            get

            {

                return this.remoteIp;

            }



            set

            {

                var ip = IPAddress.Parse(value);



                if (ip.AddressFamily != AddressFamily.InterNetwork && ip.AddressFamily != AddressFamily.InterNetworkV6)

                {

                    throw new ArgumentException(string.Format("Expecting an IP address, got {0}", ip));

                }



                this.remoteIp = ip.ToString();

            }

        }



        /// <summary>

        /// Gets or sets Response.

        /// </summary>

        public string Response { get; set; }



        #endregion



        #region Public Methods



        /// <summary>

        /// Validates this instance.

        /// </summary>

        /// <returns>The response.</returns>

        public RecaptchaResponse Validate()

        {

            CheckNotNull(this.PrivateKey, "PrivateKey");

            CheckNotNull(this.RemoteIP, "RemoteIp");

            CheckNotNull(this.Challenge, "Challenge");

            CheckNotNull(this.Response, "Response");



            if (this.Challenge == string.Empty || this.Response == string.Empty)

            {

                return RecaptchaResponse.InvalidSolution;

            }



            var request = (HttpWebRequest)WebRequest.Create(VerifyUrl);



            // to avoid issues with Expect headers

            request.ProtocolVersion = HttpVersion.Version10;

            request.Timeout = 30 * 1000 /* 30 seconds */;

            request.Method = "POST";

            request.UserAgent = "reCAPTCHA/ASP.NET";



            request.ContentType = "application/x-www-form-urlencoded";



            var formdata = String.Format(

                "privatekey={0}&remoteip={1}&challenge={2}&response={3}",

                HttpUtility.UrlEncode(this.PrivateKey),

                HttpUtility.UrlEncode(this.RemoteIP),

                HttpUtility.UrlEncode(this.Challenge),

                HttpUtility.UrlEncode(this.Response));



            var formbytes = Encoding.ASCII.GetBytes(formdata);



            using (var requestStream = request.GetRequestStream())

            {

                requestStream.Write(formbytes, 0, formbytes.Length);

            }



            string[] results;



            try

            {

                using (var httpResponse = request.GetResponse())

                {

                    var httpResponseStream = httpResponse.GetResponseStream();

                    if (httpResponseStream == null)

                    {

                        return RecaptchaResponse.RecaptchaNotReachable;

                    }



                    using (TextReader readStream = new StreamReader(httpResponseStream, Encoding.UTF8))

                    {

                        results = readStream.ReadToEnd().Split();

                    }

                }

            }

            catch (WebException)

            {

                return RecaptchaResponse.RecaptchaNotReachable;

            }



            switch (results[0])

            {

                case "true":

                    return RecaptchaResponse.Valid;

                case "false":

                    return new RecaptchaResponse(false, results[1]);

                default:

                    throw new InvalidProgramException("Unknown status response.");

            }

        }



        #endregion



        #region Methods



        /// <summary>

        /// Checks the not null.

        /// </summary>

        /// <param name="obj">The object to check.</param>

        /// <param name="name">The object name.</param>

        private static void CheckNotNull(object obj, string name)

        {

            if (obj == null)

            {

                throw new ArgumentNullException(name);

            }

        }



        #endregion

    }

}