我有一个在.NET 4.7中运行的应用程序。默认情况下，它会尝试使用TLS1.2。
在执行例如以下HTTP请求时，是否可以知道已经协商了哪个TLS版本？
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(decodedUri);
if (requestPayload.Length > 0)
{
using (Stream requestStream = request.GetRequestStream())
{
requestStream.Write(requestPayload, 0, requestPayload.Length);
}
}
我只需要这些信息用于日志记录/调试目的，因此在写入请求流或接收响应之前拥有这些信息并不重要。我不希望解析网络跟踪日志以获取这些信息，也不想创建第二个连接（使用SslStream或类似方式）。
TlsStream->SslState->SslProtocol属性的值。HttpWebRequest.GetRequestStream()和HttpWebRequest.GetResponseStream()返回的流中提取。ExtractSslProtocol()还处理启用了WebRequest AutomaticDecompression时返回的压缩GzipStream或DeflateStream。ServerCertificateValidationCallback中进行，在使用request.GetRequestStream()初始化请求时调用。SecurityProtocolType.Tls13包含在 .Net Framework 4.8+和.Net Core 3.0+ 中。using System.IO.Compression;
using System.Net;
using System.Net.Security;
using System.Reflection;
using System.Security.Authentication;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
//(...)
// Allow all, to then check what the Handshake will agree upon
ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 |
SecurityProtocolType.Tls |
SecurityProtocolType.Tls11 |
SecurityProtocolType.Tls12 |
SecurityProtocolType.Tls13;
// Handle the Server certificate exchange, to inspect the certificates received
ServicePointManager.ServerCertificateValidationCallback += TlsValidationCallback;
Uri requestUri = new Uri("https://somesite.com");
var request = WebRequest.CreateHttp(requestUri);
request.Method = WebRequestMethods.Http.Post;
request.ServicePoint.Expect100Continue = false;
request.AllowAutoRedirect = true;
request.CookieContainer = new CookieContainer();
request.ContentType = "application/x-www-form-urlencoded";
var postdata = Encoding.UTF8.GetBytes("Some postdata here");
request.ContentLength = postdata.Length;
request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64; Trident / 7.0; rv: 11.0) like Gecko";
request.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;
request.Headers.Add(HttpRequestHeader.AcceptEncoding, "gzip, deflate;q=0.8");
request.Headers.Add(HttpRequestHeader.CacheControl, "no-cache");
using (var requestStream = request.GetRequestStream()) {
//Here the request stream is already validated
SslProtocols sslProtocol = ExtractSslProtocol(requestStream);
if (sslProtocol < SslProtocols.Tls12)
{
// Refuse/close the connection
}
}
//(...)
private SslProtocols ExtractSslProtocol(Stream stream)
{
if (stream is null) return SslProtocols.None;
BindingFlags bindingFlags = BindingFlags.Instance | BindingFlags.NonPublic;
Stream metaStream = stream;
if (stream.GetType().BaseType == typeof(GZipStream)) {
metaStream = (stream as GZipStream).BaseStream;
}
else if (stream.GetType().BaseType == typeof(DeflateStream)) {
metaStream = (stream as DeflateStream).BaseStream;
}
var connection = metaStream.GetType().GetProperty("Connection", bindingFlags).GetValue(metaStream);
if (!(bool)connection.GetType().GetProperty("UsingSecureStream", bindingFlags).GetValue(connection)) {
// Not a Https connection
return SslProtocols.None;
}
var tlsStream = connection.GetType().GetProperty("NetworkStream", bindingFlags).GetValue(connection);
var tlsState = tlsStream.GetType().GetField("m_Worker", bindingFlags).GetValue(tlsStream);
return (SslProtocols)tlsState.GetType().GetProperty("SslProtocol", bindingFlags).GetValue(tlsState);
}
RemoteCertificateValidationCallback 包含一些关于所使用的安全协议的有用信息（参见：传输层安全（TLS）参数（IANA）和RFC 5246）。
所使用的安全协议类型足以提供足够的信息，因为每个协议版本支持哈希和加密算法的子集。
Tls 1.2 引入了 HMAC-SHA256 并停用了 IDEA 和 DES 密码（所有变量均列在链接的文档中）。
在这里，我插入了一个 OIDExtractor，它列出了所使用的算法。
请注意，TcpClient() 和 WebRequest() 都将到达此处。
private bool TlsValidationCallback(object sender, X509Certificate CACert, X509Chain CAChain, SslPolicyErrors sslPolicyErrors)
{
List<Oid> oidExtractor = CAChain
.ChainElements
.Cast<X509ChainElement>()
.Select(x509 => new Oid(x509.Certificate.SignatureAlgorithm.Value))
.ToList();
// Inspect the oidExtractor list
var certificate = new X509Certificate2(CACert);
//If you needed/have to pass a certificate, add it here.
//X509Certificate2 cert = new X509Certificate2(@"[localstorage]/[ca.cert]");
//CAChain.ChainPolicy.ExtraStore.Add(cert);
CAChain.Build(certificate);
foreach (X509ChainStatus CACStatus in CAChain.ChainStatus)
{
if ((CACStatus.Status != X509ChainStatusFlags.NoError) &
(CACStatus.Status != X509ChainStatusFlags.UntrustedRoot))
return false;
}
return true;
}
更新2:
secur32.dll -> QueryContextAttributesW() 方法，允许查询已初始化流的连接安全上下文。
[DllImport("secur32.dll", CharSet = CharSet.Auto, ExactSpelling=true, SetLastError=false)]
private static extern int QueryContextAttributesW(
SSPIHandle contextHandle,
[In] ContextAttribute attribute,
[In] [Out] ref SecPkgContext_ConnectionInfo ConnectionInfo
);
根据文档，该方法返回一个引用SecPkgContext_ConnectionInfo结构的void*缓冲区：
private struct SecPkgContext_ConnectionInfo
{
public SchProtocols dwProtocol;
public ALG_ID aiCipher;
public int dwCipherStrength;
public ALG_ID aiHash;
public int dwHashStrength;
public ALG_ID aiExch;
public int dwExchStrength;
}
SchProtocols dwProtocol成员是SslProtocol。
然而，引用连接上下文句柄的TlsStream.Context.m_SecurityContext._handle并不是公开的。因此，您只能通过反射或通过TcpClient.GetStream()返回的System.Net.Security.AuthenticatedStream派生类(System.Net.Security.SslStream和System.Net.Security.NegotiateStream)获取它。
不幸的是，由WebRequest/WebResponse返回的流无法转换为这些类。连接和流类型仅通过非公开属性和字段引用。
我正在发布组装好的文档，它可能会帮助您找到另一条路径来获取到该上下文句柄。
声明、结构体和枚举列表可以在QueryContextAttributesW (PASTEBIN)中找到。
Microsoft TechNet
身份验证结构
MSDN
使用Schannel创建安全连接
QueryContextAttributes (Schannel)
代码库(部分)
更新 1：
我看到你在对另一个答案的评论中提到使用
TcpClient()的解决方案对你来说不可接受。我还是把它留在这里，以便Ben Voigt在此回答中的评论对其他人有用。此外，三种可能的解决方案总比两种好。
在提供的上下文中，关于TcpClient()和SslStream的一些实现细节。
如果在初始化WebRequest之前需要协议信息，则可以在同一上下文中使用与TLS连接所需相同的工具建立TcpClient()连接。即，使用ServicePointManager.SecurityProtocol定义支持的协议和ServicePointManager.ServerCertificateValidationCallback验证服务器证书。
TcpClient()和WebRequest都可以使用这些设置：
RemoteCertificateValidationCallback()委托以验证服务器传递的X509Certificates。在实践中，建立TcpClient或WebRequest连接时，TLS握手相同。
这种方法可以让您知道您的HttpWebRequest将与同一服务器协商哪种Tls协议。
设置一个TcpClient()来接收和评估SslStream。
checkCertificateRevocation标志设置为false，因此该过程不会浪费时间查找吊销列表。
证书验证回调与ServicePointManager中指定的相同。
TlsInfo tlsInfo = null;
IPHostEntry dnsHost = await Dns.GetHostEntryAsync(HostURI.Host);
using (TcpClient client = new TcpClient(dnsHost.HostName, 443))
{
using (SslStream sslStream = new SslStream(client.GetStream(), false,
TlsValidationCallback, null))
{
sslstream.AuthenticateAsClient(dnsHost.HostName, null,
(SslProtocols)ServicePointManager.SecurityProtocol, false);
tlsInfo = new TlsInfo(sslStream);
}
}
//The HttpWebRequest goes on from here.
HttpWebRequest httpRequest = WebRequest.CreateHttp(HostURI);
//(...)
TlsInfo类收集建立安全连接时的一些信息：
public class TlsInfo
{
public TlsInfo(SslStream secStream)
{
this.ProtocolVersion = secStream.SslProtocol;
this.CipherAlgorithm = secStream.CipherAlgorithm;
this.HashAlgorithm = secStream.HashAlgorithm;
this.RemoteCertificate = secStream.RemoteCertificate;
}
public SslProtocols ProtocolVersion { get; set; }
public CipherAlgorithmType CipherAlgorithm { get; set; }
public HashAlgorithmType HashAlgorithm { get; set; }
public X509Certificate RemoteCertificate { get; set; }
}
m_NetworkStream是相关属性返回的同一对象。当然，你不能拥有所有的属性名称。 - JimiHttpWebRequest request = (HttpWebRequest)WebRequest.Create("...");
request.Method = "POST";
if (requestPayload.Length > 0)
{
using (Stream requestStream = request.GetRequestStream())
{
SslProtocols? protocol = GetSslProtocol(requestStream);
requestStream.Write(requestPayload, 0, requestPayload.Length);
}
}
方法如下：
public static SslProtocols? GetSslProtocol(Stream stream)
{
if (stream == null)
return null;
if (typeof(SslStream).IsAssignableFrom(stream.GetType()))
{
var ssl = stream as SslStream;
return ssl.SslProtocol;
}
var flags = BindingFlags.NonPublic | BindingFlags.Instance;
if (stream.GetType().FullName == "System.Net.ConnectStream")
{
var connection = stream.GetType().GetProperty("Connection", flags).GetValue(stream);
var netStream = connection.GetType().GetProperty("NetworkStream", flags).GetValue(connection) as Stream;
return GetSslProtocol(netStream);
}
if (stream.GetType().FullName == "System.Net.TlsStream")
{
// type SslState
var ssl = stream.GetType().GetField("m_Worker", flags).GetValue(stream);
if (ssl.GetType().GetProperty("IsAuthenticated", flags).GetValue(ssl) as bool? != true)
{
// we're not authenticated yet. see: https://referencesource.microsoft.com/#System/net/System/Net/_TLSstream.cs,115
var processAuthMethod = stream.GetType().GetMethod("ProcessAuthentication", flags);
processAuthMethod.Invoke(stream, new object[] { null });
}
var protocol = ssl.GetType().GetProperty("SslProtocol", flags).GetValue(ssl) as SslProtocols?;
return protocol;
}
return null;
}
我将一些想法汇集起来，编写了一个简单的方法来测试每种可用的协议，每次尝试强制使用一种特定类型的连接。
最终，我会得到一个结果列表，可以根据需要使用。
附注：此测试仅在您知道该网站在线时有效-您可以进行先前的测试以检查此内容。
public static IEnumerable<T> GetValues<T>()
{
return Enum.GetValues(typeof(T)).Cast<T>();
}
private Dictionary<SecurityProtocolType, bool> ProcessProtocols(string address)
{
var protocolResultList = new Dictionary<SecurityProtocolType, bool>();
var defaultProtocol = ServicePointManager.SecurityProtocol;
ServicePointManager.Expect100Continue = true;
foreach (var protocol in GetValues<SecurityProtocolType>())
{
try
{
ServicePointManager.SecurityProtocol = protocol;
var request = WebRequest.Create(address);
var response = request.GetResponse();
protocolResultList.Add(protocol, true);
}
catch
{
protocolResultList.Add(protocol, false);
}
}
ServicePointManager.SecurityProtocol = defaultProtocol;
return protocolResultList;
}
我能想到的唯一方法是使用SslStream进行测试连接，然后检查SslProtocol属性。
TcpClient client = new TcpClient(decodedUri.DnsSafeHost, 443);
SslStream sslStream = new SslStream(client.GetStream());
// use this overload to ensure SslStream has the same scope of enabled protocol as HttpWebRequest
sslStream.AuthenticateAsClient(decodedUri.Host, null,
(SslProtocols)ServicePointManager.SecurityProtocol, true);
// Check sslStream.SslProtocol here
client.Close();
sslStream.Close();
我已经确认了sslStream.SslProtocl始终与TlsStream.m_worker.SslProtocol相同，这是由HttpWebRequest的Connection使用的。
RemoteCertificateValidationCallback 只提供了发送方、需要验证的证书、证书链和由默认验证器检测到的验证错误，但未提供任何其他的 TLS 连接信息。很遗憾，这是个死胡同。 - Alex.Wei
System.Net跟踪，它将记录这些信息，然后你可能可以解析出来，例如：System.Net 信息: 0 : [18984] EndProcessAuthentication(Protocol=Tls12, Cipher=Aes256 256 bit strength,....等等..- CrowcoderSslStream之上自己重新实现HTTP的方式来获取。这可能值得为其提交一个问题（issue）。 - Jeroen Mostert