Fixed CPU / memory issue caused by infinite loop caused by ReadByte retu...

ImapClient.cs

@@ -494,31 +494,77 @@ private string SendCommandGetResponse(string command, bool resolveLiterals = tru
 		/// <param name="resolveLiterals">Set to true to resolve possible literals
 		/// returned by the server (Refer to RFC 3501 Section 4.3 for details).</param>
 		/// <returns>A response string from the server</returns>
-		private string GetResponse(bool resolveLiterals = true) {
+		private string GetResponse(bool resolveLiterals = true)
+		{
 			const int Newline = 10, CarriageReturn = 13;
-			using (var mem = new MemoryStream()) {
-				lock (readLock) {
-					while (true) {
-						byte b = (byte)stream.ReadByte();
-						if (b == CarriageReturn)
-							continue;
-						if (b == Newline) {
-							string s = Encoding.ASCII.GetString(mem.ToArray());
-							if (resolveLiterals) {
-								s = Regex.Replace(s, @"{(\d+)}$", m => {
-									return "\"" + GetData(Convert.ToInt32(m.Groups[1].Value)) +
-										"\"" + GetResponse(false);
-								});
+			const int ConnectionCheckThreshold = 100000;
+			try
+			{
+				using (var mem = new MemoryStream())
+				{
+					var bytesRemainingUntilNextConnectionCheck = ConnectionCheckThreshold;
+
+					lock (readLock)
+					{
+						while (true)
+						{
+							bytesRemainingUntilNextConnectionCheck--;
+
+							if (bytesRemainingUntilNextConnectionCheck == 0)
+							{
+								CheckConnection();
+								bytesRemainingUntilNextConnectionCheck = ConnectionCheckThreshold;
+							}
+
+							byte b = (byte)stream.ReadByte();
+							if (b == CarriageReturn)
+								continue;
+							if (b == Newline)
+							{
+								string s = Encoding.ASCII.GetString(mem.ToArray());
+								if (resolveLiterals)
+								{
+									s = Regex.Replace(s, @"{(\d+)}$", m =>
+									{
+										return "\"" + GetData(Convert.ToInt32(m.Groups[1].Value)) +
+											   "\"" + GetResponse(false);
+									});
+								}
+								ts.TraceInformation("S -> " + s);
+								return s;
 							}
-							ts.TraceInformation("S -> " + s);
-							return s;
-						} else
-							mem.WriteByte(b);
+							else
+								mem.WriteByte(b);
+						}
 					}
 				}
 			}
+			catch (BadServerResponseException)
+			{
+				throw;
+			}
+			catch (Exception ex)
+			{
+				throw new BadServerResponseException("Error encountered during read; see inner exception for details", ex);
+			}
 		}
 
+		/// <summary>
+		/// In the event that the SslStream is disconnected unceremoniously, it will continue to
+		/// return data from ReadByte() indefinitely. The below method should be called periodically
+		/// to check the health of the connection
+		/// </summary>
+		private void CheckConnection()
+		{
+			if (client.Client.Poll(0, SelectMode.SelectRead))
+			{
+				var buffer = new byte[1];
+				if (client.Client.Receive(buffer, SocketFlags.Peek) == 0)
+					throw new BadServerResponseException("Error encountered during read: not connected");
+			}
+		}
+
+
 		/// <summary>
 		/// Reads the specified amount of bytes from the server. This
 		/// method blocks until the specified amount of bytes has been