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package org.bouncycastle.crypto.tls;
import java.io.IOException;
import org.bouncycastle.crypto.modes.AEADBlockCipher;
import org.bouncycastle.crypto.params.AEADParameters;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.util.Arrays;
public class TlsAEADCipher
implements TlsCipher
{
protected TlsContext context;
protected int macSize;
protected int nonce_explicit_length;
protected AEADBlockCipher encryptCipher;
protected AEADBlockCipher decryptCipher;
protected byte[] encryptImplicitNonce, decryptImplicitNonce;
public TlsAEADCipher(TlsContext context, AEADBlockCipher clientWriteCipher, AEADBlockCipher serverWriteCipher,
int cipherKeySize, int macSize) throws IOException
{
if (!TlsUtils.isTLSv12(context))
{
throw new TlsFatalAlert(AlertDescription.internal_error);
}
this.context = context;
this.macSize = macSize;
// NOTE: Valid for RFC 5288/6655 ciphers but may need review for other AEAD ciphers
this.nonce_explicit_length = 8;
// TODO SecurityParameters.fixed_iv_length
int fixed_iv_length = 4;
int key_block_size = (2 * cipherKeySize) + (2 * fixed_iv_length);
byte[] key_block = TlsUtils.calculateKeyBlock(context, key_block_size);
int offset = 0;
KeyParameter client_write_key = new KeyParameter(key_block, offset, cipherKeySize);
offset += cipherKeySize;
KeyParameter server_write_key = new KeyParameter(key_block, offset, cipherKeySize);
offset += cipherKeySize;
byte[] client_write_IV = Arrays.copyOfRange(key_block, offset, offset + fixed_iv_length);
offset += fixed_iv_length;
byte[] server_write_IV = Arrays.copyOfRange(key_block, offset, offset + fixed_iv_length);
offset += fixed_iv_length;
if (offset != key_block_size)
{
throw new TlsFatalAlert(AlertDescription.internal_error);
}
KeyParameter encryptKey, decryptKey;
if (context.isServer())
{
this.encryptCipher = serverWriteCipher;
this.decryptCipher = clientWriteCipher;
this.encryptImplicitNonce = server_write_IV;
this.decryptImplicitNonce = client_write_IV;
encryptKey = server_write_key;
decryptKey = client_write_key;
}
else
{
this.encryptCipher = clientWriteCipher;
this.decryptCipher = serverWriteCipher;
this.encryptImplicitNonce = client_write_IV;
this.decryptImplicitNonce = server_write_IV;
encryptKey = client_write_key;
decryptKey = server_write_key;
}
byte[] dummyNonce = new byte[fixed_iv_length + nonce_explicit_length];
this.encryptCipher.init(true, new AEADParameters(encryptKey, 8 * macSize, dummyNonce));
this.decryptCipher.init(false, new AEADParameters(decryptKey, 8 * macSize, dummyNonce));
}
public int getPlaintextLimit(int ciphertextLimit)
{
// TODO We ought to be able to ask the decryptCipher (independently of it's current state!)
return ciphertextLimit - macSize - nonce_explicit_length;
}
public byte[] encodePlaintext(long seqNo, short type, byte[] plaintext, int offset, int len)
throws IOException
{
byte[] nonce = new byte[this.encryptImplicitNonce.length + nonce_explicit_length];
System.arraycopy(encryptImplicitNonce, 0, nonce, 0, encryptImplicitNonce.length);
/*
* RFC 5288/6655 The nonce_explicit MAY be the 64-bit sequence number.
*
* (May need review for other AEAD ciphers).
*/
TlsUtils.writeUint64(seqNo, nonce, encryptImplicitNonce.length);
int plaintextOffset = offset;
int plaintextLength = len;
int ciphertextLength = encryptCipher.getOutputSize(plaintextLength);
byte[] output = new byte[nonce_explicit_length + ciphertextLength];
System.arraycopy(nonce, encryptImplicitNonce.length, output, 0, nonce_explicit_length);
int outputPos = nonce_explicit_length;
byte[] additionalData = getAdditionalData(seqNo, type, plaintextLength);
AEADParameters parameters = new AEADParameters(null, 8 * macSize, nonce, additionalData);
try
{
encryptCipher.init(true, parameters);
outputPos += encryptCipher.processBytes(plaintext, plaintextOffset, plaintextLength, output, outputPos);
outputPos += encryptCipher.doFinal(output, outputPos);
}
catch (Exception e)
{
throw new TlsFatalAlert(AlertDescription.internal_error);
}
if (outputPos != output.length)
{
// NOTE: Existing AEAD cipher implementations all give exact output lengths
throw new TlsFatalAlert(AlertDescription.internal_error);
}
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);
}
byte[] nonce = new byte[this.decryptImplicitNonce.length + nonce_explicit_length];
System.arraycopy(decryptImplicitNonce, 0, nonce, 0, decryptImplicitNonce.length);
System.arraycopy(ciphertext, offset, nonce, decryptImplicitNonce.length, nonce_explicit_length);
int ciphertextOffset = offset + nonce_explicit_length;
int ciphertextLength = len - nonce_explicit_length;
int plaintextLength = decryptCipher.getOutputSize(ciphertextLength);
byte[] output = new byte[plaintextLength];
int outputPos = 0;
byte[] additionalData = getAdditionalData(seqNo, type, plaintextLength);
AEADParameters parameters = new AEADParameters(null, 8 * macSize, nonce, additionalData);
try
{
decryptCipher.init(false, parameters);
outputPos += decryptCipher.processBytes(ciphertext, ciphertextOffset, ciphertextLength, output, outputPos);
outputPos += decryptCipher.doFinal(output, outputPos);
}
catch (Exception e)
{
throw new TlsFatalAlert(AlertDescription.bad_record_mac);
}
if (outputPos != output.length)
{
// NOTE: Existing AEAD cipher implementations all give exact output lengths
throw new TlsFatalAlert(AlertDescription.internal_error);
}
return output;
}
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;
}
}
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