在之前的项目中，如果有需要使用验证码，基本都是自己用GDI+画图出来，简单好用，但是却也存在了一些小问题，首先若较少干扰线，则安全性不是很高，验证码容易被机器识别，若多画太多干扰线条，机器人识别率下降的同时，人眼的识别率也同步下降（震惊哭）。更为重要的是，GDI+绘制的验证码一般来说也不会很美观，如果做一个炫酷的登陆界面却配了这样一个验证码，画风诡异，丑到极致。

再后来浏览网页的过程中，发现很多很多网站项目中都使用了一种叫极验验证的验证码，采用移动滑块的方式进行验证，方便美观。而一番搜索之后了解到，官方提供的免费版也足以应付我手头的大多数项目了，不禁想把在MVC学习过程中试着使用极验验证来作为登录的验证码。

极验官方提供了C#的SDK和Demo供开发者参考，不过是Webform版本的，可读性不是很高，而现在使用Webform进行网站开发的也基本消失了，我将在官方Webform代码的基础上，将其用在ASP.NET MVC程序中。

注册极验

到极验官网注册账号之后进入后台管理界面，点击添加验证

添加后我们可以得到ID和KEY

完成验证逻辑

1. 首先我们需要引入官方的Geetestlib类

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 极验验证C# SDK基本库 /// </summary> public class GeetestLib { /// <summary> /// SDK版本号 /// </summary> public const String version = "3.2.0"; /// <summary> /// SDK开发语言 /// </summary> public const String sdkLang = "csharp"; /// <summary> /// 极验验证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> /// 极验验证API服务状态Session Key /// </summary> public const String gtServerStatusSessionKey = "gt_server_status"; /// <summary> /// 极验验证二次验证表单数据 Chllenge /// </summary> public const String fnGeetestChallenge = "geetest_challenge"; /// <summary> /// 极验验证二次验证表单数据 Validate /// </summary> public const String fnGeetestValidate = "geetest_validate"; /// <summary> /// 极验验证二次验证表单数据 Seccode /// </summary> public const String fnGeetestSeccode = "geetest_seccode"; private String userID = ""; private String responseStr = ""; private String captchaID = ""; private String privateKey = ""; /// <summary> /// 验证成功结果字符串 /// </summary> public const int successResult = 1; /// <summary> /// 证结失败验果字符串 /// </summary> public const int failResult = 0; /// <summary> /// 判定为机器人结果字符串 /// </summary> public const String forbiddenResult = "forbidden"; /// <summary> /// GeetestLib构造函数 /// </summary> /// <param name="publicKey">极验验证公钥</param> /// <param name="privateKey">极验验证私钥</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> /// 验证初始化预处理 /// </summary> /// <returns>初始化结果</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> /// 预处理失败后的返回格式串 /// </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> /// 预处理成功后的标准串 /// </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模式的验证方式 /// </summary> /// <param name="challenge">failback模式下用于与validate一起解码答案， 判断验证是否正确</param> /// <param name="validate">failback模式下用于与challenge一起解码答案， 判断验证是否正确</param> /// <param name="seccode">failback模式下，其实是个没用的参数</param> /// <returns>验证结果</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进行二次验证 /// </summary> /// <param name="challenge">本次验证会话的唯一标识</param> /// <param name="validate">拖动完成后server端返回的验证结果标识字符串</param> /// <param name="seccode">验证结果的校验码，如果gt-server返回的不与这个值相等则表明验证失败</param> /// <returns>二次验证结果</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-puteHash(UTF8Encoding.Default.GetBytes(plainText))); t2 = t2.Replace("-", ""); t2 = t2.ToLower(); return t2; } }}

2. 获取验证码

引入Jquery库

<script src="~/Content/plugins/jquery/jquery-1.8.2.min.js"></script>

添加用于放置验证码的div（需要放到form表单中）

<div id="geetest-container">

</div>
添加JS代码用于获取验证码

<script> window.addEventListener('load', processGeeTest); function processGeeTest() { $.ajax({ // 获取id，challenge，success（是否启用failback） url: "/Login/GeekTest", type: "get", dataType: "json", // 使用jsonp格式 success: function (data) { // 使用initGeetest接口 // 参数1：配置参数，与创建Geetest实例时接受的参数一致 // 参数2：回调，回调的第一个参数验证码对象，之后可以使用它做appendTo之类的事件 initGeetest({ gt: data.gt, challenge: data.challenge, product: "float", // 产品形式 offline: !data.success }, handler); } }); } var handler = function (captchaObj) { // 将验证码加到id为captcha的元素里 captchaObj.appendTo("#geetest-container"); captchaObj.onSuccess = function (e) { console.log(e); } };</script>

processGeeTest方法中我们异步请求的地址“/Login/GeekTest”就是获取验证码是后台需要执行的方法

public ActionResult GeekTest(){ return Content(GetCaptcha(),"application/json");}private string GetCaptcha(){ var geetest = new GeetestLib("3594e0d834df77cedc7351a02b5b06a4", "b961c8081ce88af7e32a3f45d00dff84"); var gtServerStatus = geetest.preProcess(); Session[GeetestLib.gtServerStatusSessionKey] = gtServerStatus; return geetest.getResponseStr();}

3. 校验验证码

注意，当提交form表单时，会将三个和极验有关的参数传到后台方法（geetest_challenge、geetest_validate、geetest_seccode），若验证码未验证成功，则参数为空值。

后台验证方法为：

private bool CheckGeeTestResult(){ var geetest = new GeetestLib("3594e0d834df77cedc7351a02b5b06a4", "b961c8081ce88af7e32a3f45d00dff84 "); var gtServerStatusCode = (byte)Session[GeetestLib.gtServerStatusSessionKey]; var userId = (string)Session["userID"]; var challenge = Request.Form.Get(GeetestLib.fnGeetestChallenge); var validate = Request.Form.Get(GeetestLib.fnGeetestValidate); var seccode = Request.Form.Get(GeetestLib.fnGeetestSeccode); var result = gtServerStatusCode == 1 ? geetest.enhencedValidateRequest(challenge, validate, seccode, userId) : geetest.failbackValidateRequest(challenge, validate, seccode); return result == 1;}

我们可以在表单中判断验证码是否成功校验：

public ActionResult Login(){ if (!CheckGeeTestResult()) return Content("no:请先完成验证操作。"); ....}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。