1 files changed, 63 insertions, 0 deletions
diff --git a/crypto/src/tls/TlsSrtpUtilities.cs b/crypto/src/tls/TlsSrtpUtilities.cs
new file mode 100644
index 000000000..72a9e774b
--- /dev/null
+++ b/crypto/src/tls/TlsSrtpUtilities.cs
@@ -0,0 +1,63 @@
+using System;
+using System.Collections;
+using System.IO;
+
+namespace Org.BouncyCastle.Tls
+{
+    /// <summary>RFC 5764 DTLS Extension to Establish Keys for SRTP.</summary>
+    public abstract class TlsSrtpUtilities
+{
+        /// <exception cref="IOException"/>
+        public static void AddUseSrtpExtension(IDictionary extensions, UseSrtpData useSrtpData)
+        {
+            extensions[ExtensionType.use_srtp] = CreateUseSrtpExtension(useSrtpData);
+        }
+
+        /// <exception cref="IOException"/>
+        public static UseSrtpData GetUseSrtpExtension(IDictionary extensions)
+        {
+            byte[] extensionData = TlsUtilities.GetExtensionData(extensions, ExtensionType.use_srtp);
+            return extensionData == null ? null : ReadUseSrtpExtension(extensionData);
+        }
+
+        /// <exception cref="IOException"/>
+        public static byte[] CreateUseSrtpExtension(UseSrtpData useSrtpData)
+        {
+            if (useSrtpData == null)
+                throw new ArgumentNullException("useSrtpData");
+
+            MemoryStream buf = new MemoryStream();
+
+            // SRTPProtectionProfiles
+            TlsUtilities.WriteUint16ArrayWithUint16Length(useSrtpData.ProtectionProfiles, buf);
+
+            // srtp_mki
+            TlsUtilities.WriteOpaque8(useSrtpData.Mki, buf);
+
+            return buf.ToArray();
+        }
+
+        /// <exception cref="IOException"/>
+        public static UseSrtpData ReadUseSrtpExtension(byte[] extensionData)
+        {
+            if (extensionData == null)
+                throw new ArgumentNullException("extensionData");
+
+            MemoryStream buf = new MemoryStream(extensionData, false);
+
+            // SRTPProtectionProfiles
+            int length = TlsUtilities.ReadUint16(buf);
+            if (length < 2 || (length & 1) != 0)
+                throw new TlsFatalAlert(AlertDescription.decode_error);
+
+            int[] protectionProfiles = TlsUtilities.ReadUint16Array(length / 2, buf);
+
+            // srtp_mki
+            byte[] mki = TlsUtilities.ReadOpaque8(buf);
+
+            TlsProtocol.AssertEmpty(buf);
+
+            return new UseSrtpData(protectionProfiles, mki);
+        }
+    }
+}