From: Matthew Endsley <mendsley@gmail.com>
Date: Wed, 13 Jan 2021 09:30:55 +0000 (-0800)
Subject: Add record wire format conversions
X-Git-Tag: 1.0.0~20^2~25^2
X-Git-Url: https://git.deb.at/?a=commitdiff_plain;h=113c1215a368590f649b3b3ba9d10f342b63de90;p=rhonda%2Fimpostor.hazel.git

Add record wire format conversions
---

diff --git a/Hazel/Dtls/Record.cs b/Hazel/Dtls/Record.cs
new file mode 100644
index 0000000..affb8a6
--- /dev/null
+++ b/Hazel/Dtls/Record.cs
@@ -0,0 +1,76 @@
+namespace Hazel.Dtls
+{
+    /// <summary>
+    /// DTLS version constants
+    /// </summary>
+    public enum ProtocolVersion : ushort
+    {
+        /// <summary>
+        /// DTLS 1.2
+        /// </summary>
+        DTLS1_2 = 0xFEFD,
+    }
+
+    /// <summary>
+    /// DTLS record content type
+    /// </summary>
+    public enum ContentType : byte
+    {
+        ChangeCipherSpec = 20,
+        Alert = 21,
+        Handshake = 22,
+        ApplicationData = 23,
+    }
+
+    /// <summary>
+    /// Encode/decode DTLS record header
+    /// </summary>
+    public struct Record
+    {
+        public ContentType ContentType;
+        public ushort Epoch;
+        public ulong SequenceNumber;
+        public ushort Length;
+
+        public const int Size = 13;
+
+        /// <summary>
+        /// Parse a DTLS record from wire format
+        /// </summary>
+        /// <returns>True if we successfully parse the record header. Otherwise false</returns>
+        public static bool Parse(out Record record, ByteSpan span)
+        {
+            record = new Record();
+
+            if (span.Length < Size)
+            {
+                return false;
+            }
+
+            record.ContentType = (ContentType)span[0];
+            ProtocolVersion version = (ProtocolVersion)span.ReadBigEndian16(1);
+            record.Epoch = span.ReadBigEndian16(3);
+            record.SequenceNumber = span.ReadBigEndian48(5);
+            record.Length = span.ReadBigEndian16(11);
+
+            if (version != ProtocolVersion.DTLS1_2)
+            {
+                return false;
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        /// Encode a DTLS record to wire format
+        /// </summary>
+        public void Encode(ByteSpan span)
+        {
+            span[0] = (byte)this.ContentType;
+            span.WriteBigEndian16((ushort)ProtocolVersion.DTLS1_2);
+            span.WriteBigEndian16(this.Epoch, 3);
+            span.WriteBigEndian48(this.SequenceNumber, 5);
+            span.WriteBigEndian16(this.Length, 11);
+        }
+    }
+}
diff --git a/Hazel/Hazel.csproj b/Hazel/Hazel.csproj
index e75bb1e..e102524 100644
--- a/Hazel/Hazel.csproj
+++ b/Hazel/Hazel.csproj
@@ -81,6 +81,7 @@
     <Compile Include="Dtls\Handshake.cs" />
     <Compile Include="Dtls\IHandshakeCipherSuite.cs" />
     <Compile Include="Dtls\PrfSha256.cs" />
+    <Compile Include="Dtls\Record.cs" />
     <Compile Include="Dtls\X25519EcdheRsaSha256.cs" />
     <Compile Include="FewerThreads\HazelThreadPool.cs" />
     <Compile Include="FewerThreads\ThreadLimitedUdpConnectionListener.cs" />