try to decode ESP frames

PacketDotNet/EspFields.cs

@@ -0,0 +1,32 @@
+/*
+This file is part of PacketDotNet.
+
+This Source Code Form is subject to the terms of the Mozilla Public
+License, v. 2.0. If a copy of the MPL was not distributed with this
+file, You can obtain one at https://mozilla.org/MPL/2.0/.
+*/
+/*
+ * Copyright 2009 Chris Morgan <[email protected]>
+ */
+
+namespace PacketDotNet
+{
+    public struct EspFields
+    {
+        /// <summary>Length of the Base Header in bytes.</summary>
+        public static readonly int HeaderLength = 8;
+
+        /// <summary>Length of the Security Parameters Index (SPI) in bytes.</summary>
+        public static readonly int SecurityParametersIndexLength = 4;
+
+        /// <summary>Length of the Sequence Number in bytes.</summary>
+        public static readonly int SequenceNumberLength = 4;
+
+        /// <summary>Length of the Pad Length in bytes.</summary>
+        public static readonly int PadLengthLength = 1;
+
+        /// <summary>Length of the Next Header in bytes.</summary>
+        public static readonly int NextHeaderLength = 1;
+
+    }
+}

PacketDotNet/EspPacket.cs

@@ -0,0 +1,179 @@
+/*
+This file is part of PacketDotNet.
+
+This Source Code Form is subject to the terms of the Mozilla Public
+License, v. 2.0. If a copy of the MPL was not distributed with this
+file, You can obtain one at https://mozilla.org/MPL/2.0/.
+*/
+/*
+ * Copyright 2010 Chris Morgan <[email protected]>
+ */
+
+
+using System;
+using PacketDotNet.Utils;
+using PacketDotNet.Utils.Converters;
+#if DEBUG
+using log4net;
+using System.Reflection;
+#endif
+
+namespace PacketDotNet
+{
+    /// <summary>
+    /// EspPacket
+    /// See: https://en.wikipedia.org/wiki/IPsec#Encapsulating_Security_Payload
+    /// </summary>
+    public sealed class EspPacket : Packet
+    {
+#if DEBUG
+        private static readonly ILog Log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
+#else
+// NOTE: No need to warn about lack of use, the compiler won't
+//       put any calls to 'log' here but we need 'log' to exist to compile
+#pragma warning disable 0169, 0649
+        private static readonly ILogInactive Log;
+#pragma warning restore 0169, 0649
+#endif
+
+        /// <summary>
+        /// Create from values.
+        /// </summary>
+        public EspPacket(TransportPacket payloadPacket, byte[] authenticationData)
+        {
+            Log.Debug("");
+
+            // allocate memory for this packet
+            var length = EspFields.HeaderLength;
+            var headerBytes = new byte[length];
+            Header = new ByteArraySegment(headerBytes, 0, length);
+            NextHeader = payloadPacket is TcpPacket ? ProtocolType.Tcp : ProtocolType.Udp;
+            payloadPacket.ParentPacket = this;
+            this.AuthenticationData = authenticationData;
+            this.PadLength = (payloadPacket.TotalPacketLength + 2) % 4;
+            this.Pad = new byte[this.PadLength];
+            for (var i = 0; i < this.PadLength; i++)
+            {
+                this.Pad[i] = (byte) (i + 1);
+            }
+            PayloadPacketOrData = new LazySlim<PacketOrByteArraySegment>(() => new PacketOrByteArraySegment
+            {
+                Packet = payloadPacket
+            });
+        }
+
+        /// <summary>
+        /// Constructor.
+        /// </summary>
+        /// <param name="byteArraySegment">
+        /// A <see cref="ByteArraySegment" />
+        /// </param>
+        /// <param name="parentPacket">
+        /// A <see cref="Packet" />
+        /// </param>
+        public EspPacket(ByteArraySegment byteArraySegment, Packet parentPacket)
+        {
+            Log.Debug("");
+
+            // set the header field, header field values are retrieved from this byte array
+            Header = new ByteArraySegment(byteArraySegment) {Length = EspFields.HeaderLength};
+
+            ParentPacket = parentPacket;
+
+            var next = Header.NextSegment();
+
+            // try to decode, assuming a Null ciphering. Get first the last 96 bits (12 bytes) for the Authentication Data
+            // + 1 byte for the Next Header + 1 byte for the pad length
+            if (next.Length > 14)
+            {
+                AuthenticationData = new byte[12];
+
+                // copy the last 12 bytes
+                Array.Copy(next.Bytes, next.BytesLength - 12, AuthenticationData, 0, 12);
+                var nextHeader = next.Bytes[next.BytesLength - 13];
+                // Continue only if next header is Tcp or Udp
+                if ((ProtocolType)nextHeader == ProtocolType.Tcp || (ProtocolType)nextHeader == ProtocolType.Udp)
+                {
+                    NextHeader = (ProtocolType) nextHeader;
+                    PadLength = next.Bytes[next.BytesLength - 14];
+
+                    if (next.Length > 14 + PadLength)
+                    {
+                        // so far ok, continue
+                        Pad = new byte[PadLength];
+                        Array.Copy(next.Bytes, next.BytesLength - 14 - PadLength, Pad, 0, PadLength);
+
+                        var startingOffset = Header.Offset + Header.Length;
+                        var segmentLength = Math.Max(0, next.Length - 14 - PadLength);
+                        var payloadData = new byte[segmentLength];
+                        Array.Copy(next.Bytes, startingOffset, payloadData, 0, segmentLength);
+                        var payload = new ByteArraySegment(payloadData, 0, segmentLength, segmentLength);
+
+                        if (NextHeader == ProtocolType.Tcp && segmentLength > 0)
+                        {
+                            PayloadPacketOrData = new LazySlim<PacketOrByteArraySegment>(() => new PacketOrByteArraySegment
+                            {
+                                Packet = new TcpPacket(payload, this)
+                            });
+
+                            return;
+                        }
+
+                        if (NextHeader == ProtocolType.Udp && segmentLength > 0)
+                        {
+                            PayloadPacketOrData = new LazySlim<PacketOrByteArraySegment>(() => new PacketOrByteArraySegment
+                            {
+                                Packet = new UdpPacket(payload, this)
+                            });
+
+                            return;
+                        }
+                    }
+                }
+            }
+
+            // store the payload bytes
+            PayloadPacketOrData = new LazySlim<PacketOrByteArraySegment>(() =>
+            {
+                var result = new PacketOrByteArraySegment {ByteArraySegment = Header.NextSegment()};
+                return result;
+            });
+        }
+
+        /// <summary>
+        /// Gets or sets the SecurityParametersIndex (SPI).
+        /// </summary>
+        public uint SecurityParametersIndex
+        {
+            get => EndianBitConverter.Big.ToUInt32(Header.Bytes, Header.Offset);
+            set => EndianBitConverter.Big.CopyBytes(value, Header.Bytes, Header.Offset);
+        }
+
+        /// <summary>
+        /// Gets or sets the SecurityParametersIndex (SPI).
+        /// </summary>
+        public uint SequenceNumber
+        {
+            get => EndianBitConverter.Big.ToUInt32(Header.Bytes, Header.Offset + EspFields.SecurityParametersIndexLength);
+            set => EndianBitConverter.Big.CopyBytes(value, Header.Bytes, Header.Offset + EspFields.SecurityParametersIndexLength);
+        }
+
+        /// <summary>
+        /// Identifies the next header field, which is the protocol of the encapsulated in packet unless there are extended headers.
+        /// </summary>
+        public ProtocolType NextHeader { get; set; }
+
+        /// <summary>Pad length.</summary>
+        public int PadLength { get; }
+
+        /// <summary>
+        /// Gets or sets the Authentication Data.
+        /// </summary>
+        public byte[] AuthenticationData { get; set; }
+
+        /// <summary>
+        /// Gets or sets the Pad.
+        /// </summary>
+        public byte[] Pad { get; }
+    }
+}

PacketDotNet/IPPacket.cs

@@ -282,6 +282,11 @@ protected static PacketOrByteArraySegment ParseNextSegment
                     payloadPacketOrData.Packet = new GrePacket(payload, parentPacket);
                     break;
                 }
+                case ProtocolType.IPSecEncapsulatingSecurityPayload:
+                {
+                    payloadPacketOrData.Packet = new EspPacket(payload, parentPacket);
+                    break;
+                }
                 // NOTE: new payload parsing entries go here
                 default:
                 {

Test/PacketType/EspPacketTest.cs

@@ -0,0 +1,57 @@
+/*
+This file is part of PacketDotNet.
+
+This Source Code Form is subject to the terms of the Mozilla Public
+License, v. 2.0. If a copy of the MPL was not distributed with this
+file, You can obtain one at https://mozilla.org/MPL/2.0/.
+*/
+
+using System;
+using NUnit.Framework;
+using PacketDotNet;
+using SharpPcap;
+using SharpPcap.LibPcap;
+
+namespace Test.PacketType
+{
+    [TestFixture]
+    public class EspPacketTest
+    {
+        [Test]
+        public void EspParsing()
+        {
+            var dev = new CaptureFileReaderDevice(NUnitSetupClass.CaptureDirectory + "ipv6_esp.pcap");
+            dev.Open();
+            PacketCapture c;
+            dev.GetNextPacket(out c);
+            var rawCapture = c.GetPacket();
+            dev.Close();
+
+            var p = Packet.ParsePacket(rawCapture.GetLinkLayers(), rawCapture.Data);
+
+            Assert.IsNotNull(p);
+            var esp = p.Extract<EspPacket>();
+            Assert.IsNotNull(esp);
+            Console.WriteLine(esp.GetType());
+            Assert.AreEqual(156633505, esp.SecurityParametersIndex);
+            Assert.AreEqual(1, esp.SequenceNumber);
+            Assert.AreEqual(ProtocolType.Tcp, esp.NextHeader);
+            Assert.AreEqual(2, esp.PadLength);
+            Assert.IsNotNull(esp.PayloadPacket);
+            var tcp = p.Extract<TcpPacket>();
+            Assert.IsNotNull(tcp);
+            Assert.AreEqual(0, tcp.UrgentPointer);
+            Assert.AreEqual(16000, tcp.WindowSize);
+            Assert.AreEqual(4, tcp.OptionsCollection.Count);
+
+            var espCreated = new EspPacket(tcp, esp.AuthenticationData)
+            {
+                SequenceNumber = 1,
+                SecurityParametersIndex = 156633505
+            };
+
+            Assert.NotNull(espCreated);
+            Assert.AreEqual(ProtocolType.Tcp, espCreated.NextHeader);
+        }
+    }
+}