HttpWebRequst中https的驗證處理問題

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最近在公司項目中使用了HttpWebRequst相關API，運行環境為.Net/Mono 2.0，是一款針對Unity平台的工具。開發過程中碰到了大家可能都碰到過的問題，Http還是Https？ 為什麼Http可以正常響應，Https就會失敗，返回結果為authorize or decrypt failed.

by th way, .Net 4.0及以上版本好像已經沒有這個問題了，巨硬默默把坑填了。

使用Http的寫法：

public void Get(string Url){HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create (Url);webRequest.Method="GET";webRequest.UserAgent = "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/36.0.1985.125 Safari/537.36";webRequest.BeginGetResponse(GetResponseCallback,webRequest);}private void GetResponseCallback(IAsyncResult ar){//RequestState myRequestState = (RequestState)ar.AsyncState;HttpWebRequest webRequest = (HttpWebRequest)ar.AsyncState;try{WebResponse response = webRequest.EndGetResponse(ar);streamReader = new StreamReader(response.GetResponseStream ());}catch(Exception es){Debug.Log (es.Message);}if (GetDataCompleted != null) {GetDataCompleted(this,new GetDataCompletedArgs(streamReader.ReadToEnd ()));}}

這裡使用了非同步，同步的寫法效果相同。

但是如果此時使用了Https的Url，結果會一直返回失敗。這是為什麼呢？原因是Https基於SSL/TLS協議，需要在請求之前進行認證驗證，而我們上面的寫法並沒有進行相關的驗證，所以導致通訊失敗。怎麼解決此問題呢？很簡單，我們在請求發出前進行驗證，在.Net 2.0或更高版本，我們加入回呼函數即可。

解決辦法：

public void Get(string Url)        {            //SSL/TLS certificate method            ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);            HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create (Url);            webRequest.Method="GET";            webRequest.UserAgent = "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/36.0.1985.125 Safari/537.36";            webRequest.BeginGetResponse(GetResponseCallback,webRequest);        }/// <summary>        /// SSL/TLS certificate callback method        /// Must return true        /// </summary>        /// <returns><c>true</c>, if validation result was checked, <c>false</c> otherwise.</returns>        /// <param name="sender">Sender.</param>        /// <param name="certificate">Certificate.</param>        /// <param name="chain">Chain.</param>        /// <param name="sslPolicyErrors">Ssl policy errors.</param>        public bool CheckValidationResult (object sender, System.Security.Cryptography.X509Certificates.X509Certificate certificate, System.Security.Cryptography.X509Certificates.X509Chain chain, SslPolicyErrors sslPolicyErrors)        {            //Debug.LogWarning (certificate.GetSerialNumberString ());            return true;        }        /// <summary>        /// Gets the response callback.        /// </summary>        /// <param name="ar">Ar.</param>        private void GetResponseCallback(IAsyncResult ar)        {            //RequestState myRequestState = (RequestState)ar.AsyncState;            HttpWebRequest webRequest = (HttpWebRequest)ar.AsyncState;            try{                WebResponse response = webRequest.EndGetResponse(ar);                streamReader = new StreamReader(response.GetResponseStream ());            }            catch(Exception es)            {                Debug.Log (es.Message);            }            if (GetDataCompleted != null) {                GetDataCompleted(this,new GetDataCompletedArgs(streamReader.ReadToEnd ()));            }        }

 

至此就可以，解決此問題，這類問題說大不大，說小不小，屬於我們開發中遇到的小坑之一，.Net4.0以上版本不需注意此問題。

關於更低的.Net 1.1的寫法，大家可以去看一下部落格，本篇博文也是參照他的解決方案：

http://blog.sina.com.cn/s/blog_4ae95c270101qnn1.html