RPC PDUs: Improved implementation: Hid FragmentLength variable and added Length property

SMBLibrary/RPC/PDU/BindAckPDU.cs

@@ -53,8 +53,7 @@ namespace SMBLibrary.RPC
         {
             AuthLength = (ushort)AuthVerifier.Length;
             int padding = (4 - ((SecondaryAddress.Length + 3) % 4)) % 4;
-            FragmentLength = (ushort)(CommonFieldsLength + BindAckFieldsFixedLength + SecondaryAddress.Length + 3 + padding + ResultList.Length + AuthLength);
-            byte[] buffer = new byte[FragmentLength];
+            byte[] buffer = new byte[Length];
             WriteCommonFieldsBytes(buffer);
             int offset = CommonFieldsLength;
             LittleEndianWriter.WriteUInt16(buffer, ref offset, MaxTransmitFragmentSize);
@@ -67,5 +66,14 @@ namespace SMBLibrary.RPC
             
             return buffer;
         }
+
+        public override int Length
+        {
+            get
+            {
+                int padding = (4 - ((SecondaryAddress.Length + 3) % 4)) % 4;
+                return CommonFieldsLength + BindAckFieldsFixedLength + SecondaryAddress.Length + 3 + padding + ResultList.Length + AuthLength;
+            }
+        }
     }
 }

SMBLibrary/RPC/PDU/BindPDU.cs

@@ -45,8 +45,7 @@ namespace SMBLibrary.RPC
         public override byte[] GetBytes()
         {
             AuthLength =(ushort)AuthVerifier.Length;
-            FragmentLength = (ushort)(CommonFieldsLength + BindFieldsFixedLength + ContextList.Length + AuthLength);
-            byte[] buffer = new byte[FragmentLength];
+            byte[] buffer = new byte[Length];
             WriteCommonFieldsBytes(buffer);
             int offset = CommonFieldsLength;
             LittleEndianWriter.WriteUInt16(buffer, ref offset, MaxTransmitFragmentSize);
@@ -58,5 +57,12 @@ namespace SMBLibrary.RPC
             return buffer;
         }
 
+        public override int Length
+        {
+            get
+            {
+                return CommonFieldsLength + BindFieldsFixedLength + ContextList.Length + AuthLength;
+            }
+        }
     }
 }

SMBLibrary/RPC/PDU/FaultPDU.cs

@@ -50,8 +50,7 @@ namespace SMBLibrary.RPC
         public override byte[] GetBytes()
         {
             AuthLength = (ushort)AuthVerifier.Length;
-            FragmentLength = (ushort)(CommonFieldsLength + FaultFieldsLength + Data.Length + AuthVerifier.Length);
-            byte[] buffer = new byte[FragmentLength];
+            byte[] buffer = new byte[Length];
             WriteCommonFieldsBytes(buffer);
             int offset = CommonFieldsLength;
             LittleEndianWriter.WriteUInt32(buffer, ref offset, AllocationHint);
@@ -64,5 +63,13 @@ namespace SMBLibrary.RPC
             ByteWriter.WriteBytes(buffer, ref offset, AuthVerifier);
             return buffer;
         }
+
+        public override int Length
+        {
+            get
+            {
+                return CommonFieldsLength + FaultFieldsLength + Data.Length + AuthVerifier.Length;
+            }
+        }
     }
 }

SMBLibrary/RPC/PDU/RPCPDU.cs

@@ -24,7 +24,7 @@ namespace SMBLibrary.RPC
         public PacketTypeName PacketType;
         public PacketFlags Flags;
         public DataRepresentationFormat DataRepresentation;
-        public ushort FragmentLength; // The length of the entire PDU
+        protected ushort FragmentLength; // The length of the entire PDU
         public ushort AuthLength;
         public uint CallID;
 
@@ -55,11 +55,19 @@ namespace SMBLibrary.RPC
             ByteWriter.WriteByte(buffer, 2, (byte)PacketType);
             ByteWriter.WriteByte(buffer, 3, (byte)Flags);
             DataRepresentation.WriteBytes(buffer, 4);
-            LittleEndianWriter.WriteUInt16(buffer, 8, FragmentLength);
+            LittleEndianWriter.WriteUInt16(buffer, 8, (ushort)Length);
             LittleEndianWriter.WriteUInt16(buffer, 10, AuthLength);
             LittleEndianWriter.WriteUInt32(buffer, 12, CallID);
         }
 
+        /// <summary>
+        /// The length of the entire PDU
+        /// </summary>
+        public abstract int Length
+        {
+            get;
+        }
+
         public static RPCPDU GetPDU(byte[] buffer, int offset)
         {
             PacketTypeName packetType = (PacketTypeName)ByteReader.ReadByte(buffer, 2);
@@ -79,5 +87,11 @@ namespace SMBLibrary.RPC
                     throw new NotImplementedException();
             }
         }
+
+        public static ushort GetPDULength(byte[] buffer, int offset)
+        {
+            ushort fragmentLength = LittleEndianConverter.ToUInt16(buffer, offset + 8);
+            return fragmentLength;
+        }
     }
 }

SMBLibrary/RPC/PDU/RequestPDU.cs

@@ -49,12 +49,7 @@ namespace SMBLibrary.RPC
         public override byte[] GetBytes()
         {
             AuthLength = (ushort)AuthVerifier.Length;
-            FragmentLength = (ushort)(CommonFieldsLength + RequestFieldsFixedLength + Data.Length + AuthVerifier.Length);
-            if ((Flags & PacketFlags.ObjectUUID) > 0)
-            {
-                FragmentLength += 16;
-            }
-            byte[] buffer = new byte[FragmentLength];
+            byte[] buffer = new byte[Length];
             WriteCommonFieldsBytes(buffer);
             int offset = CommonFieldsLength;
             LittleEndianWriter.WriteUInt32(buffer, ref offset, AllocationHint);
@@ -69,6 +64,17 @@ namespace SMBLibrary.RPC
             return buffer;
         }
 
-
+        public override int Length
+        {
+            get
+            {
+                int length = CommonFieldsLength + RequestFieldsFixedLength + Data.Length + AuthVerifier.Length;
+                if ((Flags & PacketFlags.ObjectUUID) > 0)
+                {
+                    length += 16;
+                }
+                return length;
+            }
+        }
     }
 }

SMBLibrary/RPC/PDU/ResponsePDU.cs

@@ -46,9 +46,7 @@ namespace SMBLibrary.RPC
         public override byte[] GetBytes()
         {
             AuthLength = (ushort)AuthVerifier.Length;
-            FragmentLength = (ushort)(CommonFieldsLength + ResponseFieldsLength + Data.Length + AuthVerifier.Length);
-            
-            byte[] buffer = new byte[FragmentLength];
+            byte[] buffer = new byte[Length];
             WriteCommonFieldsBytes(buffer);
             int offset = CommonFieldsLength;
             LittleEndianWriter.WriteUInt32(buffer, ref offset, AllocationHint);
@@ -59,5 +57,13 @@ namespace SMBLibrary.RPC
             ByteWriter.WriteBytes(buffer, ref offset, AuthVerifier);
             return buffer;
         }
+
+        public override int Length
+        {
+            get
+            {
+                return CommonFieldsLength + ResponseFieldsLength + Data.Length + AuthVerifier.Length;
+            }
+        }
     }
 }