Allow empty softwareversion string (#822) (#1441)

Co-authored-by: Martin Dörig <martin.doerig@protecdata.ch>

src/Renci.SshNet/Connection/ProtocolVersionExchange.cs

@@ -22,7 +22,7 @@ namespace Renci.SshNet.Connection
     internal sealed partial class ProtocolVersionExchange : IProtocolVersionExchange
     {
         private const byte Null = 0x00;
-        private const string ServerVersionPattern = "^SSH-(?<protoversion>[^-]+)-(?<softwareversion>.+?)([ ](?<comments>.+))?$";
+        private const string ServerVersionPattern = "^SSH-(?<protoversion>[^-]+)-(?<softwareversion>.*?)([ ](?<comments>.+))?$";
 
 #if NET7_0_OR_GREATER
         private static readonly Regex ServerVersionRegex = GetServerVersionRegex();

test/Renci.SshNet.Tests/Classes/Connection/ProtocolVersionExchangeTest_ServerResponseValid_EmptySoftwareVersion.cs

@@ -0,0 +1,123 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net;
+using System.Net.Sockets;
+using System.Text;
+using System.Threading;
+
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+using Renci.SshNet.Common;
+using Renci.SshNet.Connection;
+using Renci.SshNet.Tests.Common;
+
+namespace Renci.SshNet.Tests.Classes.Connection
+{
+    [TestClass]
+    public class ProtocolVersionExchangeTest_ServerResponseValid_EmptySoftwareVersion
+    {
+        private AsyncSocketListener _server;
+        private ProtocolVersionExchange _protocolVersionExchange;
+        private string _clientVersion;
+        private TimeSpan _timeout;
+        private IPEndPoint _serverEndPoint;
+        private List<byte> _dataReceivedByServer;
+        private byte[] _serverIdentification;
+        private bool _clientDisconnected;
+        private Socket _client;
+        private SshIdentification _actual;
+
+        [TestInitialize]
+        public void Setup()
+        {
+            Arrange();
+            Act();
+        }
+
+        [TestCleanup]
+        public void Cleanup()
+        {
+            if (_server != null)
+            {
+                _server.Dispose();
+                _server = null;
+            }
+
+            if (_client != null)
+            {
+                _client.Shutdown(SocketShutdown.Both);
+                _client.Close();
+                _client = null;
+            }
+        }
+
+        protected void Arrange()
+        {
+            _clientVersion = "SSH-2.0-Renci.SshNet.SshClient.0.0.1";
+            _timeout = TimeSpan.FromSeconds(5);
+            _serverEndPoint = new IPEndPoint(IPAddress.Loopback, 8122);
+            _dataReceivedByServer = new List<byte>();
+            _serverIdentification = Encoding.UTF8.GetBytes("SSH-78.5-\r\n");
+
+            _server = new AsyncSocketListener(_serverEndPoint);
+            _server.Start();
+            _server.BytesReceived += (bytes, socket) =>
+                {
+                    _dataReceivedByServer.AddRange(bytes);
+
+                    _ = socket.Send(_serverIdentification);
+
+                    socket.Shutdown(SocketShutdown.Send);
+                };
+            _server.Disconnected += (socket) => _clientDisconnected = true;
+
+            _client = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
+            _client.Connect(_serverEndPoint);
+
+            _protocolVersionExchange = new ProtocolVersionExchange();
+        }
+
+        protected void Act()
+        {
+            _actual = _protocolVersionExchange.Start(_clientVersion, _client, _timeout);
+
+            // Give some time to process all messages
+            Thread.Sleep(200);
+        }
+
+        [TestMethod]
+        public void StartShouldReturnIdentificationOfServer()
+        {
+            Assert.IsNotNull(_actual);
+            Assert.AreEqual("78.5", _actual.ProtocolVersion);
+            Assert.AreEqual(string.Empty, _actual.SoftwareVersion);
+            Assert.IsNull(_actual.Comments);
+        }
+
+        [TestMethod]
+        public void ClientIdentificationWasSentToServer()
+        {
+            var expected = Encoding.UTF8.GetBytes(_clientVersion);
+
+            Assert.AreEqual(expected.Length + 2, _dataReceivedByServer.Count);
+
+            Assert.IsTrue(expected.SequenceEqual(_dataReceivedByServer.Take(expected.Length)));
+            Assert.AreEqual(Session.CarriageReturn, _dataReceivedByServer[_dataReceivedByServer.Count - 2]);
+            Assert.AreEqual(Session.LineFeed, _dataReceivedByServer[_dataReceivedByServer.Count - 1]);
+        }
+
+        [TestMethod]
+        public void ConnectionIsClosedByServer()
+        {
+            Assert.IsTrue(_client.Connected);
+            Assert.IsFalse(_clientDisconnected);
+
+            var bytesReceived = _client.Receive(new byte[1]);
+            Assert.AreEqual(0, bytesReceived);
+
+            Assert.IsTrue(_client.Connected);
+            Assert.IsFalse(_clientDisconnected);
+        }
+    }
+}