Lab2 /70201, Казанджи Михаил. Ntp server & Snmp client

Lab2/Lab2.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+#
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NtpServer", "NtpServer\NtpServer.csproj", "{B5B6FA59-0FCF-4894-AB47-62EA69934381}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SnmpClient", "SnmpClient\SnmpClient.csproj", "{C6EC7EA8-5892-4033-AFED-D97E2EBB8C01}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{B5B6FA59-0FCF-4894-AB47-62EA69934381}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{B5B6FA59-0FCF-4894-AB47-62EA69934381}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{B5B6FA59-0FCF-4894-AB47-62EA69934381}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{B5B6FA59-0FCF-4894-AB47-62EA69934381}.Release|Any CPU.Build.0 = Release|Any CPU
+		{C6EC7EA8-5892-4033-AFED-D97E2EBB8C01}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{C6EC7EA8-5892-4033-AFED-D97E2EBB8C01}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{C6EC7EA8-5892-4033-AFED-D97E2EBB8C01}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{C6EC7EA8-5892-4033-AFED-D97E2EBB8C01}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+EndGlobal

Lab2/NtpServer/NtpServer.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>netcoreapp3.1</TargetFramework>
+    </PropertyGroup>
+
+</Project>

Lab2/NtpServer/Program.cs

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+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Net;
+using System.Net.Sockets;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace NtpServer
+{
+    internal class Packet
+    {
+        public readonly byte Head = 0x1C;
+        public byte Layer;
+        public byte Interval;
+        public byte Precisions;
+        public byte[] Delay;
+        public byte[] Disp;
+        public byte[] Id = Encoding.ASCII.GetBytes("ZHMR");
+        public byte[] TimeUpdate;
+        public byte[] TimeStart;
+        public byte[] TimeIncome;
+        public byte[] TimeSend;
+
+        public byte[] GetBytes() => new[] {Head, Layer, Interval, Precisions}
+            .Concat(Delay).Concat(Disp).Concat(Id).Concat(TimeUpdate)
+            .Concat(TimeStart).Concat(TimeIncome).Concat(TimeSend).ToArray();
+    }
+
+    internal static class Program
+    {
+        private static readonly DateTime Century = 
+            new DateTime(1900, 1, 1, 0, 0, 0, DateTimeKind.Utc);
+
+        private static byte[] GetTimestamp(DateTime? timestamp) {
+            if (timestamp == null) { return new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 }; }
+
+            DateTime time = timestamp.Value;
+            if (time.Kind == DateTimeKind.Local) { time = time.ToUniversalTime(); }
+
+            var eraTime = Century;
+            var n1 = (UInt32)(time - eraTime).TotalSeconds;
+            var buffer1LE = BitConverter.GetBytes(n1);
+
+            var n2 = (UInt32)Math.Min(Math.Max((time.Ticks - eraTime.AddSeconds(n1).Ticks) / 10_000_000.0 * 0x100000000, 0), 0x100000000);
+            var buffer2LE = BitConverter.GetBytes(n2);
+
+            return buffer1LE.Reverse().Concat(buffer2LE.Reverse()).ToArray();
+        }
+
+        private static DateTime? GetTimestamp(byte[] bytes, int offset) {
+            long n1 = BitConverter.ToUInt32(bytes.Skip(offset).Take(4).Reverse().ToArray(), 0);
+            long n2 = BitConverter.ToUInt32(bytes.Skip(offset + 4).Take(4).Reverse().ToArray(), 0);
+
+            if (n1 == 0 && n2 == 0) { return null; }
+
+            var time = Century;
+            time = time.AddTicks(n1 * 10_000_000);
+            time = time.AddTicks((long)(n2 / 4294967296.0 * 10_000_000));
+            return time;
+        }
+
+        private static void Main(string[] args)
+        {      
+            var buffer = new byte[48];
+            buffer[0] = 0x1B; //LI = 0 (no warning), VN = 3 (IPv4 only), Mode = 3 (Client Mode)
+            var ipEndPoint = new IPEndPoint(Dns.GetHostEntry("pool.ntp.org").AddressList[0], 123);
+            // ReSharper disable once ConvertToUsingDeclaration
+            using (var socket =
+                new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp) {ReceiveTimeout = 3000})
+            {
+                socket.Connect(ipEndPoint);
+                socket.Send(buffer);
+                socket.Receive(buffer);
+            }
+            var time = GetTimestamp(buffer, 40);
+            Console.WriteLine("Server online");
+            Console.WriteLine("Global time: {0}", time);
+            Console.WriteLine("Server time: {0}", GetTimestamp(DateTime.UtcNow));
+            Debug.Assert(time != null, nameof(time) + " != null");
+            Console.WriteLine(DateTime.UtcNow.Subtract((DateTime) time).Seconds <= 1
+                ? "Server time correct"
+                : "Server time need to correction");
+            var template = new Packet {Layer = (byte) (buffer[1] + 1), Interval = buffer[2], 
+                Precisions = buffer[3], Delay = buffer.Skip(4).Take(4).ToArray(), 
+                Disp = buffer.Skip(8).Take(4).ToArray(), TimeUpdate = GetTimestamp(time)};
+            using (var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp))
+            {
+                Console.CancelKeyPress += (sender, eventArgs) => { socket.Shutdown(SocketShutdown.Both); Environment.Exit(0); };
+                socket.Bind(new IPEndPoint(IPAddress.Any, 123));
+                while (true)
+                {
+                    var package = template;
+                    EndPoint ip = new IPEndPoint(IPAddress.Any, 0);
+                    var buf = new byte[49];
+                    var i = socket.ReceiveFrom(buf, ref ip);
+                    package.TimeIncome = GetTimestamp(DateTime.UtcNow);
+                    if (i != 48) return;
+                    package.TimeStart = buffer.Skip(24).Take(8).ToArray();
+                    package.TimeSend = GetTimestamp(DateTime.UtcNow);
+                    Console.WriteLine("{0}", ip);
+                    socket.SendTo(package.GetBytes(), ip);
+                }
+            }
+        }
+    }
+}

Lab2/NtpServer/Readme.md

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+## Лабораторная №2 - NTP Сервер
+
+### Сборка
+
+Для сборки необходим .NET Core v3.10+. По команде `dotnet run` программа будет запущена без создания исполняемого файла.  
+Для полной сборки проекта команда `dotnet build`.
+
+### Запуск
+
+Необходим запускать с правами администратора, так как 123 порт находится в зарезервированных системой.
+
+### Ntp Сервер
+
+Сервер реализует протокол NTPv3. Со следующей структурой протокола
+
+![Структура пакета NTP](packet.png)
+
+Сервер тестировался с помощью пакета ntpd.

Lab2/SnmpClient/Program.cs

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+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Net;
+using System.Net.Sockets;
+using System.Text;
+
+namespace SnmpClient
+{
+    internal static class Program
+    {
+        public static void Main(string[] args)
+        {
+            Console.Write("Manager ip> ");
+            var ip = Console.ReadLine();
+            Debug.Assert(ip != null, nameof(ip) + " != null");
+            if (ip.Trim().Length == 0)
+            {
+                Console.WriteLine("Wrong ip");
+                return;
+            }
+            var sock = new Socket(AddressFamily.InterNetwork, SocketType.Dgram,
+                ProtocolType.Udp);
+            sock.SetSocketOption(SocketOptionLevel.Socket,
+                SocketOptionName.ReceiveTimeout, 5000);
+
+            var iep = new IPEndPoint(IPAddress.Parse(ip!), 161);
+            var ep = (EndPoint)iep;
+            uint rid = 0;
+            Console.Write("Your community tag> ");
+            var com = Console.ReadLine()?.Trim();
+            while (true)
+            {
+                Console.Write(">");
+                string oib;
+                int offset;
+                byte[] packet;
+                switch (Console.ReadLine()?.Trim())
+                {
+                    case "get":
+                        Console.Write("oib>");
+                        oib = Console.ReadLine()?.Trim();
+                        packet = Snmp.GenGetPacket(com, oib, ref rid);
+                        sock.SendTo(packet, packet.Length, SocketFlags.None, iep);
+                        try
+                        {
+                            var recv = sock.ReceiveFrom(packet, ref ep);
+                        }
+                        catch (SocketException)
+                        {
+                            Console.WriteLine("Receive error. Maybe wrong ip?");
+                            break;
+                        }
+
+                        offset = 6 + packet[6] + 1;
+                        if (packet[offset] == 0xa2) //not Response
+                        {
+                            offset += 4;
+                            var arid = (uint) BitConverter.ToInt32(packet, offset);
+                            if (arid != rid || packet[offset + 6] != 0 || packet[offset + 9] != 0)
+                            {
+                                Console.WriteLine("Wrong answer");
+                                break;
+                            }
+
+                            offset += 16 + packet[offset + 15];
+                            switch (packet[offset])
+                            {
+                                case 2:
+                                    Console.WriteLine("Integer type [{0}]", packet[offset + 1]);
+                                    Console.WriteLine(BitConverter.ToInt32(packet, offset + 2));
+                                    break;
+                                case 4:
+                                    Console.WriteLine("String type [{0}]", packet[offset + 1]);
+                                    Console.WriteLine(Encoding.ASCII.GetString(packet.Skip(offset + 2).ToArray()));
+                                    break;
+                                case 5:
+                                    Console.WriteLine("Null type");
+                                    break;
+                            }
+                        }
+                        else
+                        {
+                            Console.WriteLine("Not RESPONSE was received");
+                        }
+                        break;
+                    case "set":
+                        Console.Write("oib> ");
+                        oib = Console.ReadLine()?.Trim();
+                        Console.Write("type(1 - int, 2 - string, 3 - null)> ");
+                        var type = Console.ReadLine()?.Trim();
+                        Console.Write("val> ");
+                        var val = Console.ReadLine()?.Trim();
+                        var data = type switch
+                        {
+                            "1" => new byte[] {2, (byte) BitConverter
+                                .GetBytes(Convert.ToInt32(val)).Count(i => i > 0)}
+                                .Concat(BitConverter.GetBytes(Convert.ToInt32(val))
+                                .Where(i => i > 0)).ToArray(),
+                            "2" => new byte[] {4, (byte) (val.Length % 128)}.Concat(Encoding.ASCII.GetBytes(val)).ToArray(),
+                            "3" => new byte[] {5, 0}
+                        };
+                        packet = Snmp.GenSetPacket(com, oib, data, ref rid);
+                        sock.SendTo(packet, packet.Length, SocketFlags.None, iep);
+                        try
+                        {
+                            var recv = sock.ReceiveFrom(packet, ref ep);
+                        }
+                        catch (SocketException)
+                        {
+                            Console.WriteLine("Receive error. Maybe wrong ip?");
+                            break;
+                        }
+
+                        offset = 6 + packet[6] + 1;
+                        if (packet[offset] == 0xa2) //not Response
+                        {
+                            offset += 4;
+                            var arid = (uint) BitConverter.ToInt32(packet, offset);
+                            if (arid != rid || packet[offset + 6] != 0 || packet[offset + 9] != 0)
+                            {
+                                Console.WriteLine("Wrong answer");
+                                break;
+                            }
+
+                            offset += 16 + packet[offset + 15];
+                            switch (packet[offset])
+                            {
+                                case 2:
+                                    Console.WriteLine("Integer type [{0}]", packet[offset + 1]);
+                                    Console.WriteLine(BitConverter.ToInt32(packet, offset + 2));
+                                    break;
+                                case 4:
+                                    Console.WriteLine("String type [{0}]", packet[offset + 1]);
+                                    Console.WriteLine(Encoding.ASCII.GetString(packet.Skip(offset + 2).ToArray()));
+                                    break;
+                                case 5:
+                                    Console.WriteLine("Null type");
+                                    break;
+                            }
+                        }
+                        else
+                        {
+                            Console.WriteLine("Not RESPONSE was received");
+                        }
+                        break;
+                    default:
+                        Console.WriteLine("Only get and set implemented");
+                        break;
+                }
+            }
+        }
+    }
+}

Lab2/SnmpClient/Readme.md

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+## Лабораторная №2 - SNMP клиент
+
+### Сборка
+
+Для сборки необходим .NET Core v3.10+. По команде `dotnet run` программа будет запущена без создания исполняемого файла.  
+Для полной сборки проекта команда `dotnet build`.
+
+### Запуск
+
+Необходим запускать с правами администратора, так как 123 порт находится в зарезервированных системой.
+
+### Snmp клиент
+
+Клиент работает с SNMP v2c. Реализованы только простые команды set и get для типов Integer и OctetString.
+
+Клиент тестировался подключением к старому роутеру tp-link, откопанном в шкафу.