/recaptcha-plugins/dotnet/library/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.



using System;

using System.Diagnostics;

using System.IO;

using System.Net;

using System.Net.Sockets;

using System.Text;

using System.Web;



namespace Recaptcha

{

    /// <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

    {

        private const string VerifyUrl = "http://www.google.com/recaptcha/api/verify";



        private string privateKey;

        private string remoteIp;



        private string challenge;

        private string response;



        private IWebProxy proxy;



        public string PrivateKey

        {

            get { return this.privateKey; }

            set { this.privateKey = value; }

        }



        public string RemoteIP

        {

            get

            {

                return this.remoteIp;

            }



            set

            {

                IPAddress ip = IPAddress.Parse(value);



                if (ip == null ||

                    (ip.AddressFamily != AddressFamily.InterNetwork &&

                    ip.AddressFamily != AddressFamily.InterNetworkV6))

                {

                    throw new ArgumentException("Expecting an IP address, got " + ip);

                }



                this.remoteIp = ip.ToString();

            }

        }



        public string Challenge

        {

            get { return this.challenge; }

            set { this.challenge = value; }

        }



        public string Response

        {

            get { return this.response; }

            set { this.response = value; }

        }



        public IWebProxy Proxy

        {

            get { return this.proxy; }

            set { this.proxy = value; }

        }



        private void CheckNotNull(object obj, string name)

        {

            if (obj == null)

            {

                throw new ArgumentNullException(name);

            }

        }



        public RecaptchaResponse Validate()

        {

            this.CheckNotNull(this.PrivateKey, "PrivateKey");

            this.CheckNotNull(this.RemoteIP, "RemoteIp");

            this.CheckNotNull(this.Challenge, "Challenge");

            this.CheckNotNull(this.Response, "Response");



            if (this.challenge == string.Empty || this.response == string.Empty)

            {

                return RecaptchaResponse.InvalidSolution;

            }



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

            request.ProtocolVersion = HttpVersion.Version10;

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

            request.Method = "POST";

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

            if (this.proxy != null)

            {

                request.Proxy = this.proxy;

            }



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



            string 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));



            byte[] formbytes = Encoding.ASCII.GetBytes(formdata);



            using (Stream requestStream = request.GetRequestStream())

            {

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

            }



            string[] results;



            try

            {

                using (WebResponse httpResponse = request.GetResponse())

                {

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

                    {

                        results = readStream.ReadToEnd().Split(new string[] { "\n", "\\n" }, StringSplitOptions.RemoveEmptyEntries);

                    }

                }

            }

            catch (WebException ex)

            {

                EventLog.WriteEntry("Application", ex.Message, EventLogEntryType.Error);

                return RecaptchaResponse.RecaptchaNotReachable;

            }



            switch (results[0])

            {

                case "true":

                    return RecaptchaResponse.Valid;

                case "false":

                    return new RecaptchaResponse(false, results[1].Trim(new char[] { '\'' }));

                default:

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

            }

        }

    }

}