1 files changed, 123 insertions, 0 deletions
diff --git a/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/tls/TlsNullCipher.java b/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/tls/TlsNullCipher.java
new file mode 100644
index 000000000..6972cea68
--- /dev/null
+++ b/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/tls/TlsNullCipher.java
@@ -0,0 +1,123 @@
+package org.spongycastle.crypto.tls;
+
+import java.io.IOException;
+
+import org.spongycastle.crypto.Digest;
+import org.spongycastle.util.Arrays;
+
+/**
+ * A NULL CipherSuite with optional MAC
+ */
+public class TlsNullCipher
+    implements TlsCipher
+{
+    protected TlsContext context;
+
+    protected TlsMac writeMac;
+    protected TlsMac readMac;
+
+    public TlsNullCipher(TlsContext context)
+    {
+        this.context = context;
+        this.writeMac = null;
+        this.readMac = null;
+    }
+
+    public TlsNullCipher(TlsContext context, Digest clientWriteDigest, Digest serverWriteDigest)
+        throws IOException
+    {
+        if ((clientWriteDigest == null) != (serverWriteDigest == null))
+        {
+            throw new TlsFatalAlert(AlertDescription.internal_error);
+        }
+
+        this.context = context;
+
+        TlsMac clientWriteMac = null, serverWriteMac = null;
+
+        if (clientWriteDigest != null)
+        {
+            int key_block_size = clientWriteDigest.getDigestSize()
+                + serverWriteDigest.getDigestSize();
+            byte[] key_block = TlsUtils.calculateKeyBlock(context, key_block_size);
+
+            int offset = 0;
+
+            clientWriteMac = new TlsMac(context, clientWriteDigest, key_block, offset,
+                clientWriteDigest.getDigestSize());
+            offset += clientWriteDigest.getDigestSize();
+
+            serverWriteMac = new TlsMac(context, serverWriteDigest, key_block, offset,
+                serverWriteDigest.getDigestSize());
+            offset += serverWriteDigest.getDigestSize();
+
+            if (offset != key_block_size)
+            {
+                throw new TlsFatalAlert(AlertDescription.internal_error);
+            }
+        }
+
+        if (context.isServer())
+        {
+            writeMac = serverWriteMac;
+            readMac = clientWriteMac;
+        }
+        else
+        {
+            writeMac = clientWriteMac;
+            readMac = serverWriteMac;
+        }
+    }
+
+    public int getPlaintextLimit(int ciphertextLimit)
+    {
+        int result = ciphertextLimit;
+        if (writeMac != null)
+        {
+            result -= writeMac.getSize();
+        }
+        return result;
+    }
+
+    public byte[] encodePlaintext(long seqNo, short type, byte[] plaintext, int offset, int len)
+        throws IOException
+    {
+        if (writeMac == null)
+        {
+            return Arrays.copyOfRange(plaintext, offset, offset + len);
+        }
+
+        byte[] mac = writeMac.calculateMac(seqNo, type, plaintext, offset, len);
+        byte[] ciphertext = new byte[len + mac.length];
+        System.arraycopy(plaintext, offset, ciphertext, 0, len);
+        System.arraycopy(mac, 0, ciphertext, len, mac.length);
+        return ciphertext;
+    }
+
+    public byte[] decodeCiphertext(long seqNo, short type, byte[] ciphertext, int offset, int len)
+        throws IOException
+    {
+        if (readMac == null)
+        {
+            return Arrays.copyOfRange(ciphertext, offset, offset + len);
+        }
+
+        int macSize = readMac.getSize();
+        if (len < macSize)
+        {
+            throw new TlsFatalAlert(AlertDescription.decode_error);
+        }
+
+        int macInputLen = len - macSize;
+
+        byte[] receivedMac = Arrays.copyOfRange(ciphertext, offset + macInputLen, offset + len);
+        byte[] computedMac = readMac.calculateMac(seqNo, type, ciphertext, offset, macInputLen);
+
+        if (!Arrays.constantTimeAreEqual(receivedMac, computedMac))
+        {
+            throw new TlsFatalAlert(AlertDescription.bad_record_mac);
+        }
+
+        return Arrays.copyOfRange(ciphertext, offset, offset + macInputLen);
+    }
+}