1 files changed, 156 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/crypto/tls/Chacha20Poly1305.java b/core/src/main/java/org/spongycastle/crypto/tls/Chacha20Poly1305.java
new file mode 100644
index 00000000..aa2c8960
--- /dev/null
+++ b/core/src/main/java/org/spongycastle/crypto/tls/Chacha20Poly1305.java
@@ -0,0 +1,156 @@
+package org.spongycastle.crypto.tls;
+
+import java.io.IOException;
+
+import org.spongycastle.crypto.Mac;
+import org.spongycastle.crypto.engines.ChaChaEngine;
+import org.spongycastle.crypto.generators.Poly1305KeyGenerator;
+import org.spongycastle.crypto.macs.Poly1305;
+import org.spongycastle.crypto.params.KeyParameter;
+import org.spongycastle.crypto.params.ParametersWithIV;
+import org.spongycastle.util.Arrays;
+import org.spongycastle.util.Pack;
+
+public class Chacha20Poly1305 implements TlsCipher
+{
+    protected TlsContext context;
+
+    protected ChaChaEngine encryptCipher;
+    protected ChaChaEngine decryptCipher;
+
+    public Chacha20Poly1305(TlsContext context) throws IOException
+    {
+        if (!TlsUtils.isTLSv12(context))
+        {
+            throw new TlsFatalAlert(AlertDescription.internal_error);
+        }
+
+        this.context = context;
+
+        byte[] key_block = TlsUtils.calculateKeyBlock(context, 64);
+
+        KeyParameter client_write_key = new KeyParameter(key_block, 0, 32);
+        KeyParameter server_write_key = new KeyParameter(key_block, 32, 32);
+
+        this.encryptCipher = new ChaChaEngine(20);
+        this.decryptCipher = new ChaChaEngine(20);
+
+        KeyParameter encryptKey, decryptKey;
+        if (context.isServer())
+        {
+            encryptKey = server_write_key;
+            decryptKey = client_write_key;
+        }
+        else
+        {
+            encryptKey = client_write_key;
+            decryptKey = server_write_key;
+        }
+
+        byte[] dummyNonce = new byte[8];
+
+        this.encryptCipher.init(true, new ParametersWithIV(encryptKey, dummyNonce));
+        this.decryptCipher.init(false, new ParametersWithIV(decryptKey, dummyNonce));
+    }
+
+    public int getPlaintextLimit(int ciphertextLimit)
+    {
+        return ciphertextLimit - 16;
+    }
+
+    public byte[] encodePlaintext(long seqNo, short type, byte[] plaintext, int offset, int len) throws IOException
+    {
+        int ciphertextLength = len + 16;
+
+        KeyParameter macKey = initRecordMAC(encryptCipher, true, seqNo);
+
+        byte[] output = new byte[ciphertextLength];
+        encryptCipher.processBytes(plaintext, offset, len, output, 0);
+
+        byte[] additionalData = getAdditionalData(seqNo, type, len);
+        byte[] mac = calculateRecordMAC(macKey, additionalData, output, 0, len);
+        System.arraycopy(mac, 0, output, len, mac.length);
+
+        return output;
+    }
+
+    public byte[] decodeCiphertext(long seqNo, short type, byte[] ciphertext, int offset, int len) throws IOException
+    {
+        if (getPlaintextLimit(len) < 0)
+        {
+            throw new TlsFatalAlert(AlertDescription.decode_error);
+        }
+
+        int plaintextLength = len - 16;
+
+        byte[] receivedMAC = Arrays.copyOfRange(ciphertext, offset + plaintextLength, offset + len);
+
+        KeyParameter macKey = initRecordMAC(decryptCipher, false, seqNo);
+
+        byte[] additionalData = getAdditionalData(seqNo, type, plaintextLength);
+        byte[] calculatedMAC = calculateRecordMAC(macKey, additionalData, ciphertext, offset, plaintextLength);
+
+        if (!Arrays.constantTimeAreEqual(calculatedMAC, receivedMAC))
+        {
+            throw new TlsFatalAlert(AlertDescription.bad_record_mac);
+        }
+
+        byte[] output = new byte[plaintextLength];
+        decryptCipher.processBytes(ciphertext, offset, plaintextLength, output, 0);
+
+        return output;
+    }
+
+    protected KeyParameter initRecordMAC(ChaChaEngine cipher, boolean forEncryption, long seqNo)
+    {
+        byte[] nonce = new byte[8];
+        TlsUtils.writeUint64(seqNo, nonce, 0);
+
+        cipher.init(forEncryption, new ParametersWithIV(null, nonce));
+
+        byte[] firstBlock = new byte[64];
+        cipher.processBytes(firstBlock, 0, firstBlock.length, firstBlock, 0);
+
+        // NOTE: The BC implementation puts 'r' after 'k'
+        System.arraycopy(firstBlock, 0, firstBlock, 32, 16);
+        KeyParameter macKey = new KeyParameter(firstBlock, 16, 32);
+        Poly1305KeyGenerator.clamp(macKey.getKey());
+        return macKey;
+    }
+
+    protected byte[] calculateRecordMAC(KeyParameter macKey, byte[] additionalData, byte[] buf, int off, int len)
+    {
+        Mac mac = new Poly1305();
+        mac.init(macKey);
+
+        updateRecordMAC(mac, additionalData, 0, additionalData.length);
+        updateRecordMAC(mac, buf, off, len);
+
+        byte[] output = new byte[mac.getMacSize()];
+        mac.doFinal(output, 0);
+        return output;
+    }
+
+    protected void updateRecordMAC(Mac mac, byte[] buf, int off, int len)
+    {
+        mac.update(buf, off, len);
+
+        byte[] longLen = Pack.longToLittleEndian(len & 0xFFFFFFFFL);
+        mac.update(longLen, 0, longLen.length);
+    }
+
+    protected byte[] getAdditionalData(long seqNo, short type, int len) throws IOException
+    {
+        /*
+         * additional_data = seq_num + TLSCompressed.type + TLSCompressed.version +
+         * TLSCompressed.length
+         */
+        byte[] additional_data = new byte[13];
+        TlsUtils.writeUint64(seqNo, additional_data, 0);
+        TlsUtils.writeUint8(type, additional_data, 8);
+        TlsUtils.writeVersion(context.getServerVersion(), additional_data, 9);
+        TlsUtils.writeUint16(len, additional_data, 11);
+
+        return additional_data;
+    }
+}