Use the best TLS version by default.

bgrainger · bgrainger · commit e4c8aece30ec · 2018-03-16T01:53:14.000-07:00
Specifying SslProtocols.None allows the .NET Framework to choose the best TLS version supported by the OS (on .NET 4.7 and later).

However, negotiating TLS 1.2 with a Windows Schannel client against a yaSSL-based MySQL Server will fail; automatically try with a lower TLS version if it's possible we're in this scenario.
diff --git a/.ci/config/config.compression+ssl.json b/.ci/config/config.compression+ssl.json
@@ -3,7 +3,7 @@
       "ConnectionString": "server=127.0.0.1;user id=ssltest;password=test;port=3306;database=mysqltest;ssl mode=required;use compression=true;DefaultCommandTimeout=3600",
       "PasswordlessUser": "no_password",
       "SecondaryDatabase": "testdb2",
-      "UnsupportedFeatures": "RsaEncryption,CachingSha2Password",
+      "UnsupportedFeatures": "RsaEncryption,CachingSha2Password,Tls12",
       "MySqlBulkLoaderLocalCsvFile": "../../../../TestData/LoadData_UTF8_BOM_Unix.CSV",
       "MySqlBulkLoaderLocalTsvFile": "../../../../TestData/LoadData_UTF8_BOM_Unix.TSV",
       "CertificatesPath": "../../../../../.ci/server/certs"
diff --git a/.ci/config/config.compression.json b/.ci/config/config.compression.json
@@ -3,7 +3,7 @@
       "ConnectionString": "server=127.0.0.1;user id=mysqltest;password='test;key=\"val';port=3306;database=mysqltest;ssl mode=none;UseCompression=true;DefaultCommandTimeout=3600",
       "PasswordlessUser": "no_password",
       "SecondaryDatabase": "testdb2",
-      "UnsupportedFeatures": "RsaEncryption,CachingSha2Password",
+      "UnsupportedFeatures": "RsaEncryption,CachingSha2Password,Tls12",
       "MySqlBulkLoaderLocalCsvFile": "../../../../TestData/LoadData_UTF8_BOM_Unix.CSV",
       "MySqlBulkLoaderLocalTsvFile": "../../../../TestData/LoadData_UTF8_BOM_Unix.TSV"
     }
diff --git a/.ci/config/config.json b/.ci/config/config.json
@@ -3,7 +3,7 @@
       "ConnectionString": "server=127.0.0.1;user id=mysqltest;password='test;key=\"val';port=3306;database=mysqltest;ssl mode=none;Use Affected Rows=true;DefaultCommandTimeout=3600",
       "PasswordlessUser": "no_password",
       "SecondaryDatabase": "testdb2",
-      "UnsupportedFeatures": "RsaEncryption,CachingSha2Password",
+      "UnsupportedFeatures": "RsaEncryption,CachingSha2Password,Tls12",
       "MySqlBulkLoaderLocalCsvFile": "../../../../TestData/LoadData_UTF8_BOM_Unix.CSV",
       "MySqlBulkLoaderLocalTsvFile": "../../../../TestData/LoadData_UTF8_BOM_Unix.TSV"
     }
diff --git a/.ci/config/config.ssl.json b/.ci/config/config.ssl.json
@@ -3,7 +3,7 @@
       "ConnectionString": "server=127.0.0.1;user id=ssltest;password=test;port=3306;database=mysqltest;ssl mode=required;certificate file=../../../../../.ci/server/certs/ssl-client.pfx;DefaultCommandTimeout=3600",
       "PasswordlessUser": "no_password",
       "SecondaryDatabase": "testdb2",
-      "UnsupportedFeatures": "RsaEncryption,CachingSha2Password",
+      "UnsupportedFeatures": "RsaEncryption,CachingSha2Password,Tls12",
       "MySqlBulkLoaderLocalCsvFile": "../../../../TestData/LoadData_UTF8_BOM_Unix.CSV",
       "MySqlBulkLoaderLocalTsvFile": "../../../../TestData/LoadData_UTF8_BOM_Unix.TSV",
       "CertificatesPath": "../../../../../.ci/server/certs"
diff --git a/.travis.yml b/.travis.yml
@@ -5,10 +5,10 @@ services: docker
 env:
   - IMAGE=mysql:5.6
     NAME=mysql
-    OMIT_FEATURES=Json,Sha256Password,RsaEncryption,LargePackets,CachingSha2Password,SessionTrack
+    OMIT_FEATURES=Json,Sha256Password,RsaEncryption,LargePackets,CachingSha2Password,SessionTrack,Tls11,Tls12
   - IMAGE=mysql:5.7
     NAME=mysql
-    OMIT_FEATURES=RsaEncryption,CachingSha2Password
+    OMIT_FEATURES=RsaEncryption,CachingSha2Password,Tls12
   - IMAGE=mysql:8.0
     NAME=mysql
     OMIT_FEATURES=None
diff --git a/src/MySqlConnector/Core/ConnectionPool.cs b/src/MySqlConnector/Core/ConnectionPool.cs
@@ -2,6 +2,7 @@
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
+using System.Security.Authentication;
 using System.Threading;
 using System.Threading.Tasks;
 using MySql.Data.MySqlClient;
@@ -17,6 +18,8 @@ internal sealed class ConnectionPool
 
 		public ConnectionSettings ConnectionSettings { get; }
 
+		public SslProtocols SslProtocols { get; set; }
+
 		public async ValueTask<ServerSession> GetSessionAsync(MySqlConnection connection, IOBehavior ioBehavior, CancellationToken cancellationToken)
 		{
 			cancellationToken.ThrowIfCancellationRequested();
@@ -411,6 +414,7 @@ private static IReadOnlyList<ConnectionPool> GetAllPools()
 		private ConnectionPool(ConnectionSettings cs)
 		{
 			ConnectionSettings = cs;
+			SslProtocols = Utility.GetDefaultSslProtocols();
 			m_generation = 0;
 			m_cleanSemaphore = new SemaphoreSlim(1);
 			m_sessionSemaphore = new SemaphoreSlim(cs.MaximumPoolSize);
diff --git a/src/MySqlConnector/Core/ServerSession.cs b/src/MySqlConnector/Core/ServerSession.cs
@@ -225,60 +225,93 @@ public async Task ConnectAsync(ConnectionSettings cs, ILoadBalancer loadBalancer
 					VerifyState(State.Created);
 					m_state = State.Connecting;
 				}
-				var connected = false;
-				if (cs.ConnectionType == ConnectionType.Tcp)
-					connected = await OpenTcpSocketAsync(cs, loadBalancer, ioBehavior, cancellationToken).ConfigureAwait(false);
-				else if (cs.ConnectionType == ConnectionType.Unix)
-					connected = await OpenUnixSocketAsync(cs, ioBehavior, cancellationToken).ConfigureAwait(false);
-				if (!connected)
+
+				// TLS negotiation should automatically fall back to the best version supported by client and server. However,
+				// Windows Schannel clients will fail to connect to a yaSSL-based MySQL Server if TLS 1.2 is requested and
+				// have to use only TLS 1.1: https://github.com/mysql-net/MySqlConnector/pull/101
+				// In order to use the best protocol possible (i.e., not always default to TLS 1.1), we try the OS-default protocol
+				// (which is SslProtocols.None; see https://docs.microsoft.com/en-us/dotnet/framework/network-programming/tls),
+				// then fall back to SslProtocols.Tls11 if that fails and it's possible that the cause is a yaSSL server.
+				bool shouldRetrySsl;
+				var sslProtocols = Pool?.SslProtocols ?? Utility.GetDefaultSslProtocols();
+				PayloadData payload;
+				InitialHandshakePayload initialHandshake;
+				do
 				{
-					lock (m_lock)
-						m_state = State.Failed;
-					Log.Error("{0} connecting failed", m_logArguments);
-					throw new MySqlException("Unable to connect to any of the specified MySQL hosts.");
-				}
+					shouldRetrySsl = (sslProtocols == SslProtocols.None || (sslProtocols & SslProtocols.Tls12) == SslProtocols.Tls12) && Utility.IsWindows();
+
+					var connected = false;
+					if (cs.ConnectionType == ConnectionType.Tcp)
+						connected = await OpenTcpSocketAsync(cs, loadBalancer, ioBehavior, cancellationToken).ConfigureAwait(false);
+					else if (cs.ConnectionType == ConnectionType.Unix)
+						connected = await OpenUnixSocketAsync(cs, ioBehavior, cancellationToken).ConfigureAwait(false);
+					if (!connected)
+					{
+						lock (m_lock)
+							m_state = State.Failed;
+						Log.Error("{0} connecting failed", m_logArguments);
+						throw new MySqlException("Unable to connect to any of the specified MySQL hosts.");
+					}
 
-				var byteHandler = new SocketByteHandler(m_socket);
-				m_payloadHandler = new StandardPayloadHandler(byteHandler);
+					var byteHandler = new SocketByteHandler(m_socket);
+					m_payloadHandler = new StandardPayloadHandler(byteHandler);
 
-				var payload = await ReceiveAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
-				var initialHandshake = InitialHandshakePayload.Create(payload);
+					payload = await ReceiveAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
+					initialHandshake = InitialHandshakePayload.Create(payload);
 
-				// if PluginAuth is supported, then use the specified auth plugin; else, fall back to protocol capabilities to determine the auth type to use
-				string authPluginName;
-				if ((initialHandshake.ProtocolCapabilities & ProtocolCapabilities.PluginAuth) != 0)
-					authPluginName = initialHandshake.AuthPluginName;
-				else
-					authPluginName = (initialHandshake.ProtocolCapabilities & ProtocolCapabilities.SecureConnection) == 0 ? "mysql_old_password" : "mysql_native_password";
-				m_logArguments[1] = authPluginName;
-				Log.Debug("{0} server sent auth_plugin_name '{1}'", m_logArguments);
-				if (authPluginName != "mysql_native_password" && authPluginName != "sha256_password" && authPluginName != "caching_sha2_password")
-				{
-					Log.Error("{0} unsupported authentication method '{1}'", m_logArguments);
-					throw new NotSupportedException("Authentication method '{0}' is not supported.".FormatInvariant(initialHandshake.AuthPluginName));
-				}
+					// if PluginAuth is supported, then use the specified auth plugin; else, fall back to protocol capabilities to determine the auth type to use
+					string authPluginName;
+					if ((initialHandshake.ProtocolCapabilities & ProtocolCapabilities.PluginAuth) != 0)
+						authPluginName = initialHandshake.AuthPluginName;
+					else
+						authPluginName = (initialHandshake.ProtocolCapabilities & ProtocolCapabilities.SecureConnection) == 0 ? "mysql_old_password" : "mysql_native_password";
+					m_logArguments[1] = authPluginName;
+					Log.Debug("{0} server sent auth_plugin_name '{1}'", m_logArguments);
+					if (authPluginName != "mysql_native_password" && authPluginName != "sha256_password" && authPluginName != "caching_sha2_password")
+					{
+						Log.Error("{0} unsupported authentication method '{1}'", m_logArguments);
+						throw new NotSupportedException("Authentication method '{0}' is not supported.".FormatInvariant(initialHandshake.AuthPluginName));
+					}
 
-				ServerVersion = new ServerVersion(Encoding.ASCII.GetString(initialHandshake.ServerVersion));
-				ConnectionId = initialHandshake.ConnectionId;
-				AuthPluginData = initialHandshake.AuthPluginData;
-				m_useCompression = cs.UseCompression && (initialHandshake.ProtocolCapabilities & ProtocolCapabilities.Compress) != 0;
+					ServerVersion = new ServerVersion(Encoding.ASCII.GetString(initialHandshake.ServerVersion));
+					ConnectionId = initialHandshake.ConnectionId;
+					AuthPluginData = initialHandshake.AuthPluginData;
+					m_useCompression = cs.UseCompression && (initialHandshake.ProtocolCapabilities & ProtocolCapabilities.Compress) != 0;
 
-				m_supportsConnectionAttributes = (initialHandshake.ProtocolCapabilities & ProtocolCapabilities.ConnectionAttributes) != 0;
-				m_supportsDeprecateEof = (initialHandshake.ProtocolCapabilities & ProtocolCapabilities.DeprecateEof) != 0;
-				var serverSupportsSsl = (initialHandshake.ProtocolCapabilities & ProtocolCapabilities.Ssl) != 0;
+					m_supportsConnectionAttributes = (initialHandshake.ProtocolCapabilities & ProtocolCapabilities.ConnectionAttributes) != 0;
+					m_supportsDeprecateEof = (initialHandshake.ProtocolCapabilities & ProtocolCapabilities.DeprecateEof) != 0;
+					var serverSupportsSsl = (initialHandshake.ProtocolCapabilities & ProtocolCapabilities.Ssl) != 0;
 
-				Log.Info("{0} made connection; ServerVersion={1}; ConnectionId={2}; Flags: {3}{4}{5}{6}", m_logArguments[0], ServerVersion.OriginalString, ConnectionId,
-					m_useCompression ? "Cmp " :"", m_supportsConnectionAttributes ? "Attr " : "", m_supportsDeprecateEof ? "" : "Eof ", serverSupportsSsl ? "Ssl " : "");
+					Log.Info("{0} made connection; ServerVersion={1}; ConnectionId={2}; Flags: {3}{4}{5}{6}", m_logArguments[0], ServerVersion.OriginalString, ConnectionId,
+						m_useCompression ? "Cmp " : "", m_supportsConnectionAttributes ? "Attr " : "", m_supportsDeprecateEof ? "" : "Eof ", serverSupportsSsl ? "Ssl " : "");
 
-				if (cs.SslMode != MySqlSslMode.None && (cs.SslMode != MySqlSslMode.Preferred || serverSupportsSsl))
-				{
-					if (!serverSupportsSsl)
+					if (cs.SslMode != MySqlSslMode.None && (cs.SslMode != MySqlSslMode.Preferred || serverSupportsSsl))
 					{
-						Log.Error("{0} requires SSL but server doesn't support it", m_logArguments);
-						throw new MySqlException("Server does not support SSL");
+						if (!serverSupportsSsl)
+						{
+							Log.Error("{0} requires SSL but server doesn't support it", m_logArguments);
+							throw new MySqlException("Server does not support SSL");
+						}
+
+						try
+						{
+							await InitSslAsync(initialHandshake.ProtocolCapabilities, cs, sslProtocols, ioBehavior, cancellationToken).ConfigureAwait(false);
+							shouldRetrySsl = false;
+						}
+						catch (Exception ex) when (shouldRetrySsl && ((ex is MySqlException && ex.InnerException is IOException) || ex is IOException))
+						{
+							// negotiating TLS 1.2 with a yaSSL-based server throws an exception on Windows, see comment at top of method
+							Log.Warn(ex, "{0} failed negotiating TLS; falling back to TLS 1.1", m_logArguments);
+							sslProtocols = SslProtocols.Tls | SslProtocols.Tls11;
+							if (Pool != null)
+								Pool.SslProtocols = sslProtocols;
+						}
 					}
-					await InitSslAsync(initialHandshake.ProtocolCapabilities, cs, ioBehavior, cancellationToken).ConfigureAwait(false);
-				}
+					else
+					{
+						shouldRetrySsl = false;
+					}
+				} while (shouldRetrySsl);
 
 				if (m_supportsConnectionAttributes && s_connectionAttributes == null)
 					s_connectionAttributes = CreateConnectionAttributes();
@@ -772,7 +805,7 @@ private async Task<bool> OpenUnixSocketAsync(ConnectionSettings cs, IOBehavior i
 			return false;
 		}
 
-		private async Task InitSslAsync(ProtocolCapabilities serverCapabilities, ConnectionSettings cs, IOBehavior ioBehavior, CancellationToken cancellationToken)
+		private async Task InitSslAsync(ProtocolCapabilities serverCapabilities, ConnectionSettings cs, SslProtocols sslProtocols, IOBehavior ioBehavior, CancellationToken cancellationToken)
 		{
 			Log.Info("{0} initializing TLS connection", m_logArguments);
 			X509CertificateCollection clientCertificates = null;
@@ -861,11 +894,6 @@ bool ValidateRemoteCertificate(object rcbSender, X509Certificate rcbCertificate,
 			else
 				sslStream = new SslStream(m_networkStream, false, ValidateRemoteCertificate, ValidateLocalCertificate);
 
-			// SslProtocols.Tls1.2 throws an exception in Windows, see https://github.com/mysql-net/MySqlConnector/pull/101
-			var sslProtocols = SslProtocols.Tls | SslProtocols.Tls11;
-			if (!Utility.IsWindows())
-				sslProtocols |= SslProtocols.Tls12;
-
 			var checkCertificateRevocation = cs.SslMode == MySqlSslMode.VerifyFull;
 
 			var initSsl = HandshakeResponse41Payload.CreateWithSsl(serverCapabilities, cs, m_useCompression);
@@ -889,6 +917,8 @@ bool ValidateRemoteCertificate(object rcbSender, X509Certificate rcbCertificate,
 				m_payloadHandler.ByteHandler = sslByteHandler;
 				m_isSecureConnection = true;
 				m_sslStream = sslStream;
+				m_logArguments[1] = sslStream.SslProtocol;
+				Log.Info("{0} connected TLS with protocol {1}", m_logArguments);
 			}
 			catch (Exception ex)
 			{
@@ -1082,6 +1112,8 @@ private void VerifyState(State state1, State state2, State state3)
 
 		internal bool SslIsMutuallyAuthenticated => m_sslStream?.IsMutuallyAuthenticated ?? false;
 
+		internal SslProtocols SslProtocol => m_sslStream?.SslProtocol ?? SslProtocols.None;
+
 		private byte[] CreateConnectionAttributes()
 		{
 			Log.Debug("{0} creating connection attributes", m_logArguments);
diff --git a/src/MySqlConnector/MySql.Data.MySqlClient/MySqlConnection.cs b/src/MySqlConnector/MySql.Data.MySqlClient/MySqlConnection.cs
@@ -3,6 +3,7 @@
 using System.Data;
 using System.Data.Common;
 using System.Net.Sockets;
+using System.Security.Authentication;
 using System.Threading;
 using System.Threading.Tasks;
 using MySqlConnector.Core;
@@ -426,6 +427,8 @@ private async ValueTask<ServerSession> CreateSessionAsync(IOBehavior? ioBehavior
 
 		internal bool SslIsMutuallyAuthenticated => m_session.SslIsMutuallyAuthenticated;
 
+		internal SslProtocols SslProtocol => m_session.SslProtocol;
+
 		internal void SetState(ConnectionState newState)
 		{
 			if (m_connectionState != newState)
diff --git a/src/MySqlConnector/Utilities/Utility.cs b/src/MySqlConnector/Utilities/Utility.cs
@@ -2,7 +2,9 @@
 using System.Globalization;
 using System.IO;
 using System.Linq;
+using System.Net.Security;
 using System.Runtime.InteropServices;
+using System.Security.Authentication;
 using System.Security.Cryptography;
 using System.Text;
 using System.Threading.Tasks;
@@ -254,5 +256,41 @@ public static void GetOSDetails(out string os, out string osDescription, out str
 			architecture = RuntimeInformation.ProcessArchitecture.ToString();
 		}
 #endif
+
+#if NET45 || NET46
+		public static SslProtocols GetDefaultSslProtocols()
+		{
+			if (!s_defaultSslProtocols.HasValue)
+			{
+				try
+				{
+					using (var memoryStream = new MemoryStream())
+					using (var sslStream = new SslStream(memoryStream))
+					{
+						sslStream.AuthenticateAsClient("localhost", null, SslProtocols.None, false);
+					}
+				}
+				catch (ArgumentException ex) when (ex.ParamName == "sslProtocolType")
+				{
+					// Prior to .NET Framework 4.7, SslProtocols.None is not a valid argument to AuthenticateAsClientAsync.
+					// If the NET46 build is loaded by an application that targets. NET 4.7 (or later), or if app.config has set
+					// Switch.System.Net.DontEnableSystemDefaultTlsVersions to false, then SslProtocols.None will work; otherwise,
+					// if the application targets .NET 4.6.2 or earlier and hasn't changed the AppContext switch, then it will
+					// fail at runtime; we catch the exception and explicitly specify the protocols to use.
+					s_defaultSslProtocols = SslProtocols.Tls | SslProtocols.Tls11 | SslProtocols.Tls12;
+				}
+				catch (Exception)
+				{
+					s_defaultSslProtocols = SslProtocols.None;
+				}
+			}
+
+			return s_defaultSslProtocols.Value;
+		}
+
+		static SslProtocols? s_defaultSslProtocols;
+#else
+		public static SslProtocols GetDefaultSslProtocols() => SslProtocols.None;
+#endif
 	}
 }
diff --git a/tests/SideBySide/ServerFeatures.cs b/tests/SideBySide/ServerFeatures.cs
@@ -16,5 +16,7 @@ public enum ServerFeatures
 		Timeout = 128,
 		ErrorCodes = 256,
 		KnownCertificateAuthority = 512,
+		Tls11 = 1024,
+		Tls12 = 2048,
 	}
 }
diff --git a/tests/SideBySide/SslTests.cs b/tests/SideBySide/SslTests.cs
@@ -1,4 +1,5 @@
 using System.IO;
+using System.Security.Authentication;
 using System.Threading.Tasks;
 using MySql.Data.MySqlClient;
 using Xunit;
@@ -118,6 +119,34 @@ public async Task ConnectSslBadCaCertificate()
 			}
 		}
 
+		[SkippableFact(ConfigSettings.RequiresSsl)]
+		public async Task ConnectSslTlsVersion()
+		{
+			using (var connection = new MySqlConnection(AppConfig.ConnectionString))
+			{
+				await connection.OpenAsync();
+#if BASELINE
+				var expectedProtocol = AppConfig.SupportedFeatures.HasFlag(ServerFeatures.Tls11) ? SslProtocols.Tls11 : SslProtocols.Tls;
+#else
+				var expectedProtocol = AppConfig.SupportedFeatures.HasFlag(ServerFeatures.Tls12) ? SslProtocols.Tls12 :
+					AppConfig.SupportedFeatures.HasFlag(ServerFeatures.Tls11) ? SslProtocols.Tls11 :
+					SslProtocols.Tls;
+#endif
+				var expectedProtocolString = expectedProtocol == SslProtocols.Tls12 ? "TLSv1.2" :
+					expectedProtocol == SslProtocols.Tls11 ? "TLSv1.1" : "TLSv1";
+
+#if !BASELINE
+				Assert.Equal(expectedProtocol, connection.SslProtocol);
+#endif
+				using (var cmd = new MySqlCommand("show status like 'Ssl_version';", connection))
+				using (var reader = await cmd.ExecuteReaderAsync())
+				{
+					Assert.True(reader.Read());
+					Assert.Equal(expectedProtocolString, reader.GetString(1));
+				}
+			}
+		}
+
 		readonly DatabaseFixture m_database;
 	}
 }

Original file line number	Diff line number	Diff line change
`@@ -3,7 +3,7 @@`
`3`	`3`	`"ConnectionString": "server=127.0.0.1;user id=mysqltest;password='test;key=\"val';port=3306;database=mysqltest;ssl mode=none;UseCompression=true;DefaultCommandTimeout=3600",`
`4`	`4`	`"PasswordlessUser": "no_password",`
`5`	`5`	`"SecondaryDatabase": "testdb2",`
`6`		`- "UnsupportedFeatures": "RsaEncryption,CachingSha2Password",`
	`6`	`+ "UnsupportedFeatures": "RsaEncryption,CachingSha2Password,Tls12",`
`7`	`7`	`"MySqlBulkLoaderLocalCsvFile": "../../../../TestData/LoadData_UTF8_BOM_Unix.CSV",`
`8`	`8`	`"MySqlBulkLoaderLocalTsvFile": "../../../../TestData/LoadData_UTF8_BOM_Unix.TSV"`
`9`	`9`	`}`
Original file line number	Diff line number	Diff line change
`@@ -16,5 +16,7 @@ public enum ServerFeatures`
`16`	`16`	`Timeout = 128,`
`17`	`17`	`ErrorCodes = 256,`
`18`	`18`	`KnownCertificateAuthority = 512,`
	`19`	`+ Tls11 = 1024,`
	`20`	`+ Tls12 = 2048,`
`19`	`21`	`}`
`20`	`22`	`}`