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package org.bouncycastle.crypto.tls;
import java.io.IOException;
import org.bouncycastle.crypto.Digest;
import org.bouncycastle.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);
}
}
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