1 files changed, 74 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/crypto/tls/TlsSRTPUtils.java b/core/src/main/java/org/spongycastle/crypto/tls/TlsSRTPUtils.java
new file mode 100644
index 00000000..edc48795
--- /dev/null
+++ b/core/src/main/java/org/spongycastle/crypto/tls/TlsSRTPUtils.java
@@ -0,0 +1,74 @@
+package org.spongycastle.crypto.tls;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.util.Hashtable;
+
+import org.spongycastle.util.Integers;
+
+/**
+ * RFC 5764 DTLS Extension to Establish Keys for SRTP.
+ */
+public class TlsSRTPUtils
+{
+    public static final Integer EXT_use_srtp = Integers.valueOf(ExtensionType.use_srtp);
+
+    public static void addUseSRTPExtension(Hashtable extensions, UseSRTPData useSRTPData)
+        throws IOException
+    {
+        extensions.put(EXT_use_srtp, createUseSRTPExtension(useSRTPData));
+    }
+
+    public static UseSRTPData getUseSRTPExtension(Hashtable extensions)
+        throws IOException
+    {
+        byte[] extensionData = TlsUtils.getExtensionData(extensions, EXT_use_srtp);
+        return extensionData == null ? null : readUseSRTPExtension(extensionData);
+    }
+
+    public static byte[] createUseSRTPExtension(UseSRTPData useSRTPData)
+        throws IOException
+    {
+        if (useSRTPData == null)
+        {
+            throw new IllegalArgumentException("'useSRTPData' cannot be null");
+        }
+
+        ByteArrayOutputStream buf = new ByteArrayOutputStream();
+
+        // SRTPProtectionProfiles
+        TlsUtils.writeUint16ArrayWithUint16Length(useSRTPData.getProtectionProfiles(), buf);
+
+        // srtp_mki
+        TlsUtils.writeOpaque8(useSRTPData.getMki(), buf);
+
+        return buf.toByteArray();
+    }
+
+    public static UseSRTPData readUseSRTPExtension(byte[] extensionData)
+        throws IOException
+    {
+        if (extensionData == null)
+        {
+            throw new IllegalArgumentException("'extensionData' cannot be null");
+        }
+
+        ByteArrayInputStream buf = new ByteArrayInputStream(extensionData);
+
+        // SRTPProtectionProfiles
+        int length = TlsUtils.readUint16(buf);
+        if (length < 2 || (length & 1) != 0)
+        {
+            throw new TlsFatalAlert(AlertDescription.decode_error);
+        }
+        int[] protectionProfiles = TlsUtils.readUint16Array(length / 2, buf);
+
+        // srtp_mki
+        byte[] mki = TlsUtils.readOpaque8(buf);
+
+        TlsProtocol.assertEmpty(buf);
+
+        return new UseSRTPData(protectionProfiles, mki);
+    }
+}