1 files changed, 126 insertions, 0 deletions
diff --git a/core/src/main/java/org/bouncycastle/crypto/tls/TlsStreamCipher.java b/core/src/main/java/org/bouncycastle/crypto/tls/TlsStreamCipher.java
new file mode 100644
index 00000000..1755c2d4
--- /dev/null
+++ b/core/src/main/java/org/bouncycastle/crypto/tls/TlsStreamCipher.java
@@ -0,0 +1,126 @@
+package org.bouncycastle.crypto.tls;
+
+import java.io.IOException;
+
+import org.bouncycastle.crypto.CipherParameters;
+import org.bouncycastle.crypto.Digest;
+import org.bouncycastle.crypto.StreamCipher;
+import org.bouncycastle.crypto.params.KeyParameter;
+import org.bouncycastle.util.Arrays;
+
+public class TlsStreamCipher
+    implements TlsCipher
+{
+    protected TlsContext context;
+
+    protected StreamCipher encryptCipher;
+    protected StreamCipher decryptCipher;
+
+    protected TlsMac writeMac;
+    protected TlsMac readMac;
+
+    public TlsStreamCipher(TlsContext context, StreamCipher clientWriteCipher,
+                           StreamCipher serverWriteCipher, Digest clientWriteDigest, Digest serverWriteDigest,
+                           int cipherKeySize)
+        throws IOException
+    {
+
+        boolean isServer = context.isServer();
+
+        this.context = context;
+
+        this.encryptCipher = clientWriteCipher;
+        this.decryptCipher = serverWriteCipher;
+
+        int key_block_size = (2 * cipherKeySize) + clientWriteDigest.getDigestSize()
+            + serverWriteDigest.getDigestSize();
+
+        byte[] key_block = TlsUtils.calculateKeyBlock(context, key_block_size);
+
+        int offset = 0;
+
+        // Init MACs
+        TlsMac clientWriteMac = new TlsMac(context, clientWriteDigest, key_block, offset,
+            clientWriteDigest.getDigestSize());
+        offset += clientWriteDigest.getDigestSize();
+        TlsMac serverWriteMac = new TlsMac(context, serverWriteDigest, key_block, offset,
+            serverWriteDigest.getDigestSize());
+        offset += serverWriteDigest.getDigestSize();
+
+        // Build keys
+        KeyParameter clientWriteKey = new KeyParameter(key_block, offset, cipherKeySize);
+        offset += cipherKeySize;
+        KeyParameter serverWriteKey = new KeyParameter(key_block, offset, cipherKeySize);
+        offset += cipherKeySize;
+
+        if (offset != key_block_size)
+        {
+            throw new TlsFatalAlert(AlertDescription.internal_error);
+        }
+
+        CipherParameters encryptParams, decryptParams;
+        if (isServer)
+        {
+            this.writeMac = serverWriteMac;
+            this.readMac = clientWriteMac;
+            this.encryptCipher = serverWriteCipher;
+            this.decryptCipher = clientWriteCipher;
+            encryptParams = serverWriteKey;
+            decryptParams = clientWriteKey;
+        }
+        else
+        {
+            this.writeMac = clientWriteMac;
+            this.readMac = serverWriteMac;
+            this.encryptCipher = clientWriteCipher;
+            this.decryptCipher = serverWriteCipher;
+            encryptParams = clientWriteKey;
+            decryptParams = serverWriteKey;
+        }
+
+        this.encryptCipher.init(true, encryptParams);
+        this.decryptCipher.init(false, decryptParams);
+    }
+
+    public int getPlaintextLimit(int ciphertextLimit)
+    {
+        return ciphertextLimit - writeMac.getSize();
+    }
+
+    public byte[] encodePlaintext(long seqNo, short type, byte[] plaintext, int offset, int len)
+    {
+        byte[] mac = writeMac.calculateMac(seqNo, type, plaintext, offset, len);
+
+        byte[] outbuf = new byte[len + mac.length];
+
+        encryptCipher.processBytes(plaintext, offset, len, outbuf, 0);
+        encryptCipher.processBytes(mac, 0, mac.length, outbuf, len);
+
+        return outbuf;
+    }
+
+    public byte[] decodeCiphertext(long seqNo, short type, byte[] ciphertext, int offset, int len)
+        throws IOException
+    {
+        int macSize = readMac.getSize();
+        if (len < macSize)
+        {
+            throw new TlsFatalAlert(AlertDescription.decode_error);
+        }
+
+        byte[] deciphered = new byte[len];
+        decryptCipher.processBytes(ciphertext, offset, len, deciphered, 0);
+
+        int macInputLen = len - macSize;
+
+        byte[] receivedMac = Arrays.copyOfRange(deciphered, macInputLen, len);
+        byte[] computedMac = readMac.calculateMac(seqNo, type, deciphered, 0, macInputLen);
+
+        if (!Arrays.constantTimeAreEqual(receivedMac, computedMac))
+        {
+            throw new TlsFatalAlert(AlertDescription.bad_record_mac);
+        }
+
+        return Arrays.copyOfRange(deciphered, 0, macInputLen);
+    }
+}