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package org.spongycastle.crypto.tls;
import org.spongycastle.crypto.CipherParameters;
import org.spongycastle.crypto.Digest;
import org.spongycastle.crypto.Mac;
import org.spongycastle.crypto.params.KeyParameter;
import org.spongycastle.util.Arrays;
/**
* HMAC implementation based on original internet draft for HMAC (RFC 2104)
* <p/>
* The difference is that padding is concatenated versus XORed with the key
* <p/>
* H(K + opad, H(K + ipad, text))
*/
public class SSL3Mac
implements Mac
{
private final static byte IPAD_BYTE = (byte)0x36;
private final static byte OPAD_BYTE = (byte)0x5C;
static final byte[] IPAD = genPad(IPAD_BYTE, 48);
static final byte[] OPAD = genPad(OPAD_BYTE, 48);
private Digest digest;
private byte[] secret;
private int padLength;
/**
* Base constructor for one of the standard digest algorithms that the byteLength of
* the algorithm is know for. Behaviour is undefined for digests other than MD5 or SHA1.
*
* @param digest the digest.
*/
public SSL3Mac(Digest digest)
{
this.digest = digest;
if (digest.getDigestSize() == 20)
{
this.padLength = 40;
}
else
{
this.padLength = 48;
}
}
public String getAlgorithmName()
{
return digest.getAlgorithmName() + "/SSL3MAC";
}
public Digest getUnderlyingDigest()
{
return digest;
}
public void init(CipherParameters params)
{
secret = Arrays.clone(((KeyParameter)params).getKey());
reset();
}
public int getMacSize()
{
return digest.getDigestSize();
}
public void update(byte in)
{
digest.update(in);
}
public void update(byte[] in, int inOff, int len)
{
digest.update(in, inOff, len);
}
public int doFinal(byte[] out, int outOff)
{
byte[] tmp = new byte[digest.getDigestSize()];
digest.doFinal(tmp, 0);
digest.update(secret, 0, secret.length);
digest.update(OPAD, 0, padLength);
digest.update(tmp, 0, tmp.length);
int len = digest.doFinal(out, outOff);
reset();
return len;
}
/**
* Reset the mac generator.
*/
public void reset()
{
digest.reset();
digest.update(secret, 0, secret.length);
digest.update(IPAD, 0, padLength);
}
private static byte[] genPad(byte b, int count)
{
byte[] padding = new byte[count];
Arrays.fill(padding, b);
return padding;
}
}
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