Fix avoidable exception when data length is too long (#823)

* Data lengths longer than stream position when data lengths are greater than int.maxvalue are ignored and do not throw an exception

* Removed unreachable test

* Do not try to load the data (just ignore it)

---------

Co-authored-by: Steve Evans <sevans1@oeconnection.com>
Co-authored-by: Rob Hague <rob.hague00@gmail.com>

Author: 3 people

src/Renci.SshNet/Messages/Transport/IgnoreMessage.cs

@@ -1,6 +1,4 @@
 using System;
-using System.Globalization;
-using Renci.SshNet.Abstractions;
 
 namespace Renci.SshNet.Messages.Transport
 {
@@ -13,7 +11,8 @@ public class IgnoreMessage : Message
         internal const byte MessageNumber = 2;
 
         /// <summary>
-        /// Gets ignore message data if any.
+        /// Gets ignore message data if this message has been initialised
+        /// with data to be sent. Otherwise, returns an empty array.
         /// </summary>
         public byte[] Data { get; private set; }
 
@@ -61,21 +60,7 @@ protected override int BufferCapacity
         /// </summary>
         protected override void LoadData()
         {
-            var dataLength = ReadUInt32();
-            if (dataLength > int.MaxValue)
-            {
-                throw new NotSupportedException(string.Format(CultureInfo.CurrentCulture, "Data longer than {0} is not supported.", int.MaxValue));
-            }
-
-            if (dataLength > (DataStream.Length - DataStream.Position))
-            {
-                DiagnosticAbstraction.Log("SSH_MSG_IGNORE: Length exceeds data bytes, data ignored.");
-                Data = Array.Empty<byte>();
-            }
-            else
-            {
-                Data = ReadBytes((int) dataLength);
-            }
+            // Do nothing - this data is supposed to be ignored.
         }
 
         /// <summary>

test/Renci.SshNet.Tests/Classes/Messages/Transport/IgnoreMessageTest.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Globalization;
 using System.Linq;
 using Renci.SshNet.Common;
 using Renci.SshNet.Messages.Transport;
@@ -80,7 +79,7 @@ public void GetBytes()
         }
 
         [TestMethod]
-        public void Load()
+        public void Load_IgnoresData()
         {
             var ignoreMessage = new IgnoreMessage(_data);
             var bytes = ignoreMessage.GetBytes();
@@ -89,47 +88,7 @@ public void Load()
             target.Load(bytes, 1, bytes.Length - 1);
 
             Assert.IsNotNull(target.Data);
-            Assert.AreEqual(_data.Length, target.Data.Length);
-            Assert.IsTrue(target.Data.SequenceEqual(_data));
-        }
-
-        [TestMethod]
-        public void Load_ShouldIgnoreDataWhenItsLengthIsGreatherThanItsActualBytes()
-        {
-            var ssh = new SshDataStream(1);
-            ssh.WriteByte(2); // Type
-            ssh.Write(5u); // Data length
-            ssh.Write(new byte[3]); // Data
-
-            var ignoreMessageBytes = ssh.ToArray();
-
-            var ignoreMessage = new IgnoreMessage();
-            ignoreMessage.Load(ignoreMessageBytes, 1, ignoreMessageBytes.Length - 1);
-            Assert.IsNotNull(ignoreMessage.Data);
-            Assert.AreEqual(0, ignoreMessage.Data.Length);
-        }
-
-        [TestMethod]
-        public void Load_ShouldThrowNotSupportedExceptionWhenDataLengthIsGreaterThanInt32MaxValue()
-        {
-            var ssh = new SshDataStream(1);
-            ssh.WriteByte(2); // Type
-            ssh.Write(uint.MaxValue); // Data length
-            ssh.Write(new byte[3]);
-
-            var ignoreMessageBytes = ssh.ToArray();
-            var ignoreMessage = new IgnoreMessage();
-
-            try
-            {
-                ignoreMessage.Load(ignoreMessageBytes, 1, ignoreMessageBytes.Length - 1);
-                Assert.Fail();
-            }
-            catch (NotSupportedException ex)
-            {
-                Assert.IsNull(ex.InnerException);
-                Assert.AreEqual(string.Format(CultureInfo.CurrentCulture, "Data longer than {0} is not supported.", int.MaxValue), ex.Message);
-            }
+            Assert.AreEqual(0, target.Data.Length);
         }
     }
 }