org.bouncycastle.tls.crypto.impl.jcajce.JceBlockCipherWithCBCImplicitIVImpl Maven / Gradle / Ivy

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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.

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package org.bouncycastle.tls.crypto.impl.jcajce;

import java.security.GeneralSecurityException;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import org.bouncycastle.tls.crypto.impl.TlsBlockCipherImpl;
import org.bouncycastle.util.Arrays;

/**
 * A basic wrapper for a JCE Cipher class to provide the needed block cipher functionality for TLS where the
 * cipher requires the IV to be continued between calls.
 */
public class JceBlockCipherWithCBCImplicitIVImpl
    implements TlsBlockCipherImpl
{
    private final Cipher cipher;
    private final String algorithm;
    private final boolean isEncrypting;

    private SecretKey key;
    private byte[] nextIV;

    public JceBlockCipherWithCBCImplicitIVImpl(Cipher cipher, String algorithm, boolean isEncrypting)
        throws GeneralSecurityException
    {
        this.cipher = cipher;
        this.algorithm = algorithm;
        this.isEncrypting = isEncrypting;
    }

    public void setKey(byte[] key, int keyOff, int keyLen)
    {
        this.key = new SecretKeySpec(key, keyOff, keyLen, algorithm);
    }

    public void init(byte[] iv, int ivOff, int ivLen)
    {
        if (nextIV != null)
        {
            throw new IllegalStateException("unexpected reinitialization of an implicit-IV cipher");
        }

        nextIV = Arrays.copyOfRange(iv, ivOff, ivOff + ivLen);
    }

    public int doFinal(byte[] input, int inputOffset, int inputLength, byte[] output, int outputOffset)
    {
        try
        {
            cipher.init(isEncrypting ? Cipher.ENCRYPT_MODE : Cipher.DECRYPT_MODE, key, new IvParameterSpec(nextIV));

            nextIV = null;

            if (!isEncrypting)
            {
                nextIV = Arrays.copyOfRange(input, inputOffset + inputLength - cipher.getBlockSize(), inputOffset + inputLength);
            }

            int len = cipher.doFinal(input, inputOffset, inputLength, output, outputOffset);

            if (isEncrypting)
            {
                nextIV = Arrays.copyOfRange(output, outputOffset + inputLength - cipher.getBlockSize(), outputOffset + inputLength);
            }

            return len;
        }
        catch (GeneralSecurityException e)
        {
            throw new IllegalStateException(e);
        }
    }

    public int getBlockSize()
    {
        return cipher.getBlockSize();
    }
}