在之前的項目中，如果有需要使用驗證碼，基本都是自己用GDI+畫圖出來，簡單好用，但是卻也存在了一些小問題，首先若較少干擾線，則安全性不是很高，驗證碼容易被機器識別，若多畫太多干擾線條，機器人識別率下降的同時，人眼的識別率也同步下降（震驚哭）。更為重要的是，GDI+繪制的驗證碼一般來說也不會很美觀，如果做一個炫酷的登陸界面卻配了這樣一個驗證碼，畫風詭異，丑到極致。
再后來瀏覽網頁的過程中，發現很多很多網站項目中都使用了一種叫極驗驗證的驗證碼，采用移動滑塊的方式進行驗證，方便美觀。而一番搜索之后了解到，官方提供的免費版也足以應付我手頭的大多數項目了，不禁想把在MVC學習過程中試著使用極驗驗證來作為登錄的驗證碼。
極驗官方提供了C#的SDK和Demo供開發者參考，不過是Webform版本的，可讀性不是很高，而現在使用Webform進行網站開發的也基本消失了，我將在官方Webform代碼的基礎上，將其用在ASP.NET MVC程序中。
注冊極驗
到極驗官網注冊賬號之后進入后臺管理界面，點擊添加驗證
添加后我們可以得到ID和KEY
完成驗證邏輯
1. 首先我們需要引入官方的Geetestlib類
using System;using System.Collections;using System.Collections.Generic;using System.Linq;using System.Text;using System.Security.Cryptography;using System.Net;using System.IO;namespace PMS.WebApp.Models{ /// <summary> /// GeetestLib 極驗驗證C# SDK基本庫 /// </summary> public class GeetestLib { /// <summary> /// SDK版本號 /// </summary> public const String version = "3.2.0"; /// <summary> /// SDK開發語言 /// </summary> public const String sdkLang = "csharp"; /// <summary> /// 極驗驗證API URL /// </summary> protected const String apiUrl = "http://api.geetest.com"; /// <summary> /// register url /// </summary> protected const String registerUrl = "/register.php"; /// <summary> /// validate url /// </summary> protected const String validateUrl = "/validate.php"; /// <summary> /// 極驗驗證API服務狀態Session Key /// </summary> public const String gtServerStatusSessionKey = "gt_server_status"; /// <summary> /// 極驗驗證二次驗證表單數據 Chllenge /// </summary> public const String fnGeetestChallenge = "geetest_challenge"; /// <summary> /// 極驗驗證二次驗證表單數據 Validate /// </summary> public const String fnGeetestValidate = "geetest_validate"; /// <summary> /// 極驗驗證二次驗證表單數據 Seccode /// </summary> public const String fnGeetestSeccode = "geetest_seccode"; private String userID = ""; private String responseStr = ""; private String captchaID = ""; private String privateKey = ""; /// <summary> /// 驗證成功結果字符串 /// </summary> public const int successResult = 1; /// <summary> /// 證結失敗驗果字符串 /// </summary> public const int failResult = 0; /// <summary> /// 判定為機器人結果字符串 /// </summary> public const String forbiddenResult = "forbidden"; /// <summary> /// GeetestLib構造函數 /// </summary> /// <param name="publicKey">極驗驗證公鑰</param> /// <param name="privateKey">極驗驗證私鑰</param> public GeetestLib(String publicKey, String privateKey) { this.privateKey = privateKey; this.captchaID = publicKey; } private int getRandomNum() { Random rand =new Random(); int randRes = rand.Next(100); return randRes; } /// <summary> /// 驗證初始化預處理 /// </summary> /// <returns>初始化結果</returns> public Byte preProcess() { if (this.captchaID == null) { Console.WriteLine("publicKey is null!"); } else { String challenge = this.registerChallenge(); if (challenge.Length == 32) { this.getSuccessPreProcessRes(challenge); return 1; } else { this.getFailPreProcessRes(); Console.WriteLine("Server regist challenge failed!"); } } return 0; } public Byte preProcess(String userID) { if (this.captchaID == null) { Console.WriteLine("publicKey is null!"); } else { this.userID = userID; String challenge = this.registerChallenge(); if (challenge.Length == 32) { this.getSuccessPreProcessRes(challenge); return 1; } else { this.getFailPreProcessRes(); Console.WriteLine("Server regist challenge failed!"); } } return 0; } public String getResponseStr() { return this.responseStr; } /// <summary> /// 預處理失敗后的返回格式串 /// </summary> private void getFailPreProcessRes() { int rand1 = this.getRandomNum(); int rand2 = this.getRandomNum(); String md5Str1 = this.md5Encode(rand1 + ""); String md5Str2 = this.md5Encode(rand2 + ""); String challenge = md5Str1 + md5Str2.Substring(0, 2); this.responseStr = "{" + string.Format( "/"success/":{0},/"gt/":/"{1}/",/"challenge/":/"{2}/"", 0, this.captchaID, challenge) + "}"; } /// <summary> /// 預處理成功后的標準串 /// </summary> private void getSuccessPreProcessRes(String challenge) { challenge = this.md5Encode(challenge + this.privateKey); this.responseStr ="{" + string.Format( "/"success/":{0},/"gt/":/"{1}/",/"challenge/":/"{2}/"", 1, this.captchaID, challenge) + "}"; } /// <summary> /// failback模式的驗證方式 /// </summary> /// <param name="challenge">failback模式下用于與validate一起解碼答案， 判斷驗證是否正確</param> /// <param name="validate">failback模式下用于與challenge一起解碼答案， 判斷驗證是否正確</param> /// <param name="seccode">failback模式下，其實是個沒用的參數</param> /// <returns>驗證結果</returns> public int failbackValidateRequest(String challenge, String validate, String seccode) { if (!this.requestIsLegal(challenge, validate, seccode)) return GeetestLib.failResult; String[] validateStr = validate.Split('_'); String encodeAns = validateStr[0]; String encodeFullBgImgIndex = validateStr[1]; String encodeImgGrpIndex = validateStr[2]; int decodeAns = this.decodeResponse(challenge, encodeAns); int decodeFullBgImgIndex = this.decodeResponse(challenge, encodeFullBgImgIndex); int decodeImgGrpIndex = this.decodeResponse(challenge, encodeImgGrpIndex); int validateResult = this.validateFailImage(decodeAns, decodeFullBgImgIndex, decodeImgGrpIndex); return validateResult; } private int validateFailImage(int ans, int full_bg_index, int img_grp_index) { const int thread = 3; String full_bg_name = this.md5Encode(full_bg_index + "").Substring(0, 10); String bg_name = md5Encode(img_grp_index + "").Substring(10, 10); String answer_decode = ""; for (int i = 0;i < 9; i++) { if (i % 2 == 0) answer_decode += full_bg_name.ElementAt(i); else if (i % 2 == 1) answer_decode += bg_name.ElementAt(i); } String x_decode = answer_decode.Substring(4); int x_int = Convert.ToInt32(x_decode, 16); int result = x_int % 200; if (result < 40) result = 40; if (Math.Abs(ans - result) < thread) return GeetestLib.successResult; else return GeetestLib.failResult; } private Boolean requestIsLegal(String challenge, String validate, String seccode) { if (challenge.Equals(string.Empty) || validate.Equals(string.Empty) || seccode.Equals(string.Empty)) return false; return true; } /// <summary> /// 向gt-server進行二次驗證 /// </summary> /// <param name="challenge">本次驗證會話的唯一標識</param> /// <param name="validate">拖動完成后server端返回的驗證結果標識字符串</param> /// <param name="seccode">驗證結果的校驗碼，如果gt-server返回的不與這個值相等則表明驗證失敗</param> /// <returns>二次驗證結果</returns> public int enhencedValidateRequest(String challenge, String validate, String seccode) { if (!this.requestIsLegal(challenge, validate, seccode)) return GeetestLib.failResult; if (validate.Length > 0 && checkResultByPrivate(challenge, validate)) { String query = "seccode=" + seccode + "&sdk=csharp_" + GeetestLib.version; String response = ""; try { response = postValidate(query); } catch (Exception e) { Console.WriteLine(e); } if (response.Equals(md5Encode(seccode))) { return GeetestLib.successResult; } } return GeetestLib.failResult; } public int enhencedValidateRequest(String challenge, String validate, String seccode, String userID) { if (!this.requestIsLegal(challenge, validate, seccode)) return GeetestLib.failResult; if (validate.Length > 0 && checkResultByPrivate(challenge, validate)) { String query = "seccode=" + seccode + "&user_id=" + userID + "&sdk=csharp_" + GeetestLib.version; String response = ""; try { response = postValidate(query); } catch (Exception e) { Console.WriteLine(e); } if (response.Equals(md5Encode(seccode))) { return GeetestLib.successResult; } } return GeetestLib.failResult; } private String readContentFromGet(String url) { try { HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url); request.Timeout = 20000; HttpWebResponse response = (HttpWebResponse)request.GetResponse(); Stream myResponseStream = response.GetResponseStream(); StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.GetEncoding("utf-8")); String retString = myStreamReader.ReadToEnd(); myStreamReader.Close(); myResponseStream.Close(); return retString; } catch { return ""; } } private String registerChallenge() { String url = ""; if (string.Empty.Equals(this.userID)) { url = string.Format("{0}{1}?gt={2}", GeetestLib.apiUrl, GeetestLib.registerUrl, this.captchaID); } else { url = string.Format("{0}{1}?gt={2}&user_id={3}", GeetestLib.apiUrl, GeetestLib.registerUrl, this.captchaID, this.userID); } string retString = this.readContentFromGet(url); return retString; } private Boolean checkResultByPrivate(String origin, String validate) { String encodeStr = md5Encode(privateKey + "geetest" + origin); return validate.Equals(encodeStr); } private String postValidate(String data) { String url = string.Format("{0}{1}", GeetestLib.apiUrl, GeetestLib.validateUrl); HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url); request.Method = "POST"; request.ContentType = "application/x-www-form-urlencoded"; request.ContentLength = Encoding.UTF8.GetByteCount(data); // 發送數據 Stream myRequestStream = request.GetRequestStream(); byte[] requestBytes = System.Text.Encoding.ASCII.GetBytes(data); myRequestStream.Write(requestBytes, 0, requestBytes.Length); myRequestStream.Close(); HttpWebResponse response = (HttpWebResponse)request.GetResponse(); // 讀取返回信息 Stream myResponseStream = response.GetResponseStream(); StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.GetEncoding("utf-8")); string retString = myStreamReader.ReadToEnd(); myStreamReader.Close(); myResponseStream.Close(); return retString; } private int decodeRandBase(String challenge) { String baseStr = challenge.Substring(32, 2); List<int> tempList = new List<int>(); for(int i = 0; i < baseStr.Length; i++) { int tempAscii = (int)baseStr[i]; tempList.Add((tempAscii > 57) ? (tempAscii - 87) : (tempAscii - 48)); } int result = tempList.ElementAt(0) * 36 + tempList.ElementAt(1); return result; } private int decodeResponse(String challenge, String str) { if (str.Length>100) return 0; int[] shuzi = new int[] { 1, 2, 5, 10, 50}; String chongfu = ""; Hashtable key = new Hashtable(); int count = 0; for (int i=0;i<challenge.Length;i++) { String item = challenge.ElementAt(i) + ""; if (chongfu.Contains(item)) continue; else { int value = shuzi[count % 5]; chongfu += item; count++; key.Add(item, value); } } int res = 0; for (int i = 0; i < str.Length; i++) res += (int)key[str[i]+""]; res = res - this.decodeRandBase(challenge); return res; } private String md5Encode(String plainText) { MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider(); string t2 = BitConverter.ToString(md5.ComputeHash(UTF8Encoding.Default.GetBytes(plainText))); t2 = t2.Replace("-", ""); t2 = t2.ToLower(); return t2; } }}
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