BcSsl3Hmac
HMAC implementation based on original internet draft for HMAC (RFC 2104).
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Utilities;
using System;
namespace Org.BouncyCastle.Tls.Crypto.Impl.BC
{
internal class BcSsl3Hmac : TlsHmac, TlsMac
{
private const byte IPAD_BYTE = 54;
private const byte OPAD_BYTE = 92;
private static readonly byte[] IPAD = GenPad(54, 48);
private static readonly byte[] OPAD = GenPad(92, 48);
private readonly IDigest m_digest;
private readonly int m_padLength;
private byte[] m_secret;
public virtual int InternalBlockSize => m_digest.GetByteLength();
public virtual int MacLength => m_digest.GetDigestSize();
internal BcSsl3Hmac(IDigest digest)
{
m_digest = digest;
if (digest.GetDigestSize() == 20)
m_padLength = 40;
else
m_padLength = 48;
}
public virtual void SetKey(byte[] key, int keyOff, int keyLen)
{
m_secret = TlsUtilities.CopyOfRangeExact(key, keyOff, keyOff + keyLen);
Reset();
}
public void SetKey(ReadOnlySpan<byte> key)
{
m_secret = key.ToArray();
Reset();
}
public virtual void Update(byte[] input, int inOff, int len)
{
m_digest.BlockUpdate(input, inOff, len);
}
public void Update(ReadOnlySpan<byte> input)
{
m_digest.BlockUpdate(input);
}
public virtual byte[] CalculateMac()
{
byte[] array = new byte[m_digest.GetDigestSize()];
DoFinal(array, 0);
return array;
}
public virtual void CalculateMac(byte[] output, int outOff)
{
DoFinal(output, outOff);
}
public virtual void Reset()
{
m_digest.Reset();
m_digest.BlockUpdate(m_secret, 0, m_secret.Length);
m_digest.BlockUpdate(IPAD, 0, m_padLength);
}
private void DoFinal(byte[] output, int outOff)
{
byte[] array = new byte[m_digest.GetDigestSize()];
m_digest.DoFinal(array, 0);
m_digest.BlockUpdate(m_secret, 0, m_secret.Length);
m_digest.BlockUpdate(OPAD, 0, m_padLength);
m_digest.BlockUpdate(array, 0, array.Length);
m_digest.DoFinal(output, outOff);
Reset();
}
private static byte[] GenPad(byte b, int count)
{
byte[] obj = new byte[count];
Arrays.Fill(obj, b);
return obj;
}
}
}