无法使用WebClient.DownloadFile方法从启用了TLS 1.1/1.2协议的计算机下载文件

Question

我正在尝试使用Webclient.DownloadFile方法通过TLS 1.1/1.2协议实现一个简单的控制台应用程序来下载文件.这是应用程序的代码:

var downloadUrl = "https://serverURL.com/sample.mp3";
var filename = "sample.mp3";
var myWebClient = new WebClient();
myWebClient.DownloadFile(downloadUrl, filename);

每次我运行它我收到以下错误信息:

Unhandled Exception: System.Net.WebException: 
The underlying connection was closed: An unexpected error occurred on a receive. --->   

System.ComponentModel.Win32Exception: The client and server cannot communicate, because they do not possessa common algorithm
at System.Net.SSPIWrapper.AcquireCredentialsHandle(SSPIInterface SecModule, String package, CredentialUse intent, SecureCredential scc)
at System.Net.Security.SecureChannel.AcquireCredentialsHandle(CredentialUse credUsage, SecureCredential& secureCredential)
at System.Net.Security.SecureChannel.AcquireClientCredentials(Byte[]& thumbPrint)
at System.Net.Security.SecureChannel.GenerateToken(Byte[] input, Int32 offset, Int32 count, Byte[]& output)
at System.Net.Security.SecureChannel.NextMessage(Byte[] incoming, Int32 offset, Int32 count)
at System.Net.Security.SslState.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslState.ForceAuthentication(Boolean receiveFirst, Byte[] buffer, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslState.ProcessAuthentication(LazyAsyncResult lazyResult)
at System.Net.TlsStream.CallProcessAuthentication(Object state)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Net.TlsStream.ProcessAuthentication(LazyAsyncResult result)
at System.Net.TlsStream.Write(Byte[] buffer, Int32 offset, Int32 size)
at System.Net.PooledStream.Write(Byte[] buffer, Int32 offset, Int32 size)
at System.Net.ConnectStream.WriteHeaders(Boolean async)
--- End of inner exception stack trace ---
at System.Net.WebClient.DownloadFile(Uri address, String fileName)
at System.Net.WebClient.DownloadFile(String address, String fileName)
at web_downloader.Program.Main(String[] args) in c:\Users\user\Documents\Visual Studio 2013\Projects\web_downloader\web_downloader\Program.cs:line 27

我有以下设置:web_downloader应用程序位于ServerA(Windows Server 2012 R2/64bit)上,其在HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Control/SecurityProviders/SCHANNEL/Protocols下的注册表项中包含以下内容:

PCT 1.0
--Client
----DisabledByDefault=1
----Enabled=0
--Server
----DisabledByDefault=1
----Enabled=0
SSL 2.0
--Client
----DisabledByDefault=1
----Enabled=0
--Server
----DisabledByDefault=1
----Enabled=0
SSL 3.0
--Client
----DisabledByDefault=1
----Enabled=0
--Server
----DisabledByDefault=1
----Enabled=0
TLS 1.0
--Client
----DisabledByDefault=1
----Enabled=0
--Server
----DisabledByDefault=1
----Enabled=0
TLS 1.1
--Client
----DisabledByDefault=0
----Enabled=1
--Server
----DisabledByDefault=0
----Enabled=1
TLS 1.2
--Client
----DisabledByDefault=0
----Enabled=1
--Server
----DisabledByDefault=0
----Enabled=1

而服务器B,存储sample.mp3文件,有以下几点:

SSL 2.0
  Client
    DisabledByDefault=1
TLS 1.1
  Client
    DisabledByDefault=0
    Enabled=1
  Server
    DisabledByDefault=0
    Enabled=1
TLS 1.2
  Client
    DisabledByDefault=0
    Enabled=1
  Server
    DisabledByDefault=0
    Enabled=1

一旦我在ServerA上启用TLS 1.0,我就可以从ServerB(Windows 7/64bit/Net Framework 4.5.1)下载mp3文件而不会出现任何问题.

系统加密:在两台计算机上禁用使用FIPS兼容算法进行加密,散列和签名策略.

我是否缺少DownloadFile方法的任何配置参数以使用TLS 1.1/1.2？

Answer 1

.NET Framework使用自己的设置来确定默认情况下要使用的HTTPS版本.见/sf/answers/11857751/为ServicePointManager.SecurityProtocol设置在客户端上设置,以确保它试图协商TLS1.1连接.

您还可以使用Fiddler(查看CONNECTTunnel的TextView请求检查器)来查看出站流量,以获取ClientHello消息的细分.请注意,启用HTTPS解密的运行Fiddler会产生干扰,因为Fiddler本身默认使用SSL3 + TLS1与服务器通信.