org.bouncycastle.tls.crypto.impl.TlsNullCipher Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of bctls-fips Show documentation
The Bouncy Castle Java APIs for the TLS, including a JSSE provider. The APIs are designed primarily to be used in conjunction with the BC FIPS provider. The APIs may also be used with other providers although if being used in a FIPS context it is the responsibility of the user to ensure that any other providers used are FIPS certified and used appropriately.
There is a newer version: 2.0.19
Show newest version
package org.bouncycastle.tls.crypto.impl;

import java.io.IOException;

import org.bouncycastle.tls.AlertDescription;
import org.bouncycastle.tls.ContentType;
import org.bouncycastle.tls.ProtocolVersion;
import org.bouncycastle.tls.SecurityParameters;
import org.bouncycastle.tls.TlsFatalAlert;
import org.bouncycastle.tls.TlsUtils;
import org.bouncycastle.tls.crypto.TlsCipher;
import org.bouncycastle.tls.crypto.TlsCryptoParameters;
import org.bouncycastle.tls.crypto.TlsDecodeResult;
import org.bouncycastle.tls.crypto.TlsEncodeResult;
import org.bouncycastle.tls.crypto.TlsHMAC;

/**
 * The NULL cipher.
 */
public final class TlsNullCipher
    implements TlsCipher
{
    private final TlsSuiteHMac readMac, writeMac;
    private final byte[] decryptConnectionID, encryptConnectionID;
    private final boolean decryptUseInnerPlaintext, encryptUseInnerPlaintext;

    public TlsNullCipher(TlsCryptoParameters cryptoParams, TlsHMAC clientMac, TlsHMAC serverMac)
        throws IOException
    {
        SecurityParameters securityParameters = cryptoParams.getSecurityParametersHandshake();
        ProtocolVersion negotiatedVersion = securityParameters.getNegotiatedVersion();

        if (TlsImplUtils.isTLSv13(negotiatedVersion))
        {
            throw new TlsFatalAlert(AlertDescription.internal_error);
        }

        this.decryptConnectionID = securityParameters.getConnectionIDPeer();
        this.encryptConnectionID = securityParameters.getConnectionIDLocal();

        this.decryptUseInnerPlaintext = !ArrayUtil.isNullOrEmpty(decryptConnectionID);
        this.encryptUseInnerPlaintext = !ArrayUtil.isNullOrEmpty(encryptConnectionID);

        int key_block_size = clientMac.getMacLength() + serverMac.getMacLength();
        byte[] key_block = TlsImplUtils.calculateKeyBlock(cryptoParams, key_block_size);

        int offset = 0;

        clientMac.setKey(key_block, offset, clientMac.getMacLength());
        offset += clientMac.getMacLength();
        serverMac.setKey(key_block, offset, serverMac.getMacLength());
        offset += serverMac.getMacLength();

        if (offset != key_block_size)
        {
            throw new TlsFatalAlert(AlertDescription.internal_error);
        }

        if (cryptoParams.isServer())
        {
            writeMac = new TlsSuiteHMac(cryptoParams, serverMac);
            readMac = new TlsSuiteHMac(cryptoParams, clientMac);
        }
        else
        {
            writeMac = new TlsSuiteHMac(cryptoParams, clientMac);
            readMac = new TlsSuiteHMac(cryptoParams, serverMac);
        }
    }

    public int getCiphertextDecodeLimit(int plaintextLimit)
    {
        int innerPlaintextLimit = plaintextLimit + (decryptUseInnerPlaintext ? 1 : 0);

        return innerPlaintextLimit + readMac.getSize();        
    }

    public int getCiphertextEncodeLimit(int plaintextLimit)
    {
        int innerPlaintextLimit = plaintextLimit + (encryptUseInnerPlaintext ? 1 : 0);

        return innerPlaintextLimit + writeMac.getSize();        
    }

    public int getPlaintextDecodeLimit(int ciphertextLimit)
    {
        int innerPlaintextLimit = ciphertextLimit - readMac.getSize();

        return innerPlaintextLimit - (decryptUseInnerPlaintext ? 1 : 0);        
    }

    public int getPlaintextEncodeLimit(int ciphertextLimit)
    {
        int innerPlaintextLimit = ciphertextLimit - writeMac.getSize();

        return innerPlaintextLimit - (encryptUseInnerPlaintext ? 1 : 0);        
    }

    public TlsEncodeResult encodePlaintext(long seqNo, short contentType, ProtocolVersion recordVersion, int headerAllocation,
        byte[] plaintext, int offset, int len) throws IOException
    {
        int macSize = writeMac.getSize();

        // TODO[cid] If we support adding padding to DTLSInnerPlaintext, this will need review
        int innerPlaintextLength = len + (encryptUseInnerPlaintext ? 1 : 0);

        byte[] ciphertext = new byte[headerAllocation + innerPlaintextLength + macSize];
        System.arraycopy(plaintext, offset, ciphertext, headerAllocation, len);

        short recordType = contentType;
        if (encryptUseInnerPlaintext)
        {
            ciphertext[headerAllocation + len] = (byte)contentType;
            recordType = ContentType.tls12_cid;
        }

        byte[] mac = writeMac.calculateMac(seqNo, recordType, encryptConnectionID, ciphertext, headerAllocation,
            innerPlaintextLength);
        System.arraycopy(mac, 0, ciphertext, headerAllocation + innerPlaintextLength, mac.length);

        return new TlsEncodeResult(ciphertext, 0, ciphertext.length, recordType);
    }

    public TlsDecodeResult decodeCiphertext(long seqNo, short recordType, ProtocolVersion recordVersion,
        byte[] ciphertext, int offset, int len) throws IOException
    {
        int macSize = readMac.getSize();

        int innerPlaintextLength = len - macSize;

        if (innerPlaintextLength < (decryptUseInnerPlaintext ? 1 : 0))
            throw new TlsFatalAlert(AlertDescription.decode_error);

        byte[] expectedMac = readMac.calculateMac(seqNo, recordType, decryptConnectionID, ciphertext, offset,
            innerPlaintextLength);

        boolean badMac = !TlsUtils.constantTimeAreEqual(macSize, expectedMac, 0, ciphertext,
            offset + innerPlaintextLength);
        if (badMac)
        {
            throw new TlsFatalAlert(AlertDescription.bad_record_mac);
        }

        short contentType = recordType;
        int plaintextLength = innerPlaintextLength;

        if (decryptUseInnerPlaintext)
        {
            // Strip padding and read true content type from DTLSInnerPlaintext
            for (;;)
            {
                if (--plaintextLength < 0)
                {
                    throw new TlsFatalAlert(AlertDescription.unexpected_message);
                }

                byte octet = ciphertext[offset + plaintextLength];
                if (0 != octet)
                {
                    contentType = (short)(octet & 0xFF);
                    break;
                }
            }
        }

        return new TlsDecodeResult(ciphertext, offset, plaintextLength, contentType);
    }

    public void rekeyDecoder() throws IOException
    {
        throw new TlsFatalAlert(AlertDescription.internal_error);
    }

    public void rekeyEncoder() throws IOException
    {
        throw new TlsFatalAlert(AlertDescription.internal_error);
    }

    public boolean usesOpaqueRecordTypeDecode()
    {
        return decryptUseInnerPlaintext;
    }

    public boolean usesOpaqueRecordTypeEncode()
    {
        return encryptUseInnerPlaintext;
    }
}