HMac
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Utilities;
using System;
namespace Org.BouncyCastle.Crypto.Macs
{
public class HMac : IMac
{
private const byte IPAD = 54;
private const byte OPAD = 92;
private readonly IDigest digest;
private readonly int digestSize;
private readonly int blockLength;
private IMemoable ipadState;
private IMemoable opadState;
private readonly byte[] inputPad;
private readonly byte[] outputBuf;
public virtual string AlgorithmName => digest.AlgorithmName + "/HMAC";
public HMac(IDigest digest)
: this(digest, digest.GetByteLength())
{
}
public HMac(IDigest digest, int blockLength)
{
if (blockLength < 16)
throw new ArgumentException("must be at least 16 bytes", "blockLength");
this.digest = digest;
digestSize = digest.GetDigestSize();
this.blockLength = blockLength;
inputPad = new byte[blockLength];
outputBuf = new byte[blockLength + digestSize];
}
public virtual IDigest GetUnderlyingDigest()
{
return digest;
}
public virtual void Init(ICipherParameters parameters)
{
digest.Reset();
KeyParameter keyParameter = (KeyParameter)parameters;
int keyLength = keyParameter.KeyLength;
if (keyLength > blockLength) {
byte[] key = keyParameter.GetKey();
digest.BlockUpdate(key, 0, keyLength);
digest.DoFinal(inputPad, 0);
keyLength = digestSize;
} else
keyParameter.CopyTo(inputPad, 0, keyLength);
Array.Clear(inputPad, keyLength, blockLength - keyLength);
Array.Copy(inputPad, 0, outputBuf, 0, blockLength);
XorPad(inputPad, blockLength, 54);
XorPad(outputBuf, blockLength, 92);
IMemoable memoable = digest as IMemoable;
if (memoable != null) {
opadState = memoable.Copy();
((IDigest)opadState).BlockUpdate(outputBuf, 0, blockLength);
digest.BlockUpdate(inputPad, 0, inputPad.Length);
ipadState = memoable.Copy();
} else
digest.BlockUpdate(inputPad, 0, inputPad.Length);
}
public virtual int GetMacSize()
{
return digestSize;
}
public virtual void Update(byte input)
{
digest.Update(input);
}
public virtual void BlockUpdate(byte[] input, int inOff, int len)
{
digest.BlockUpdate(input, inOff, len);
}
public virtual int DoFinal(byte[] output, int outOff)
{
digest.DoFinal(outputBuf, blockLength);
if (opadState != null) {
((IMemoable)digest).Reset(opadState);
digest.BlockUpdate(outputBuf, blockLength, digestSize);
} else
digest.BlockUpdate(outputBuf, 0, outputBuf.Length);
int result = digest.DoFinal(output, outOff);
Array.Clear(outputBuf, blockLength, digestSize);
if (ipadState != null) {
((IMemoable)digest).Reset(ipadState);
return result;
}
digest.BlockUpdate(inputPad, 0, inputPad.Length);
return result;
}
public virtual void Reset()
{
if (ipadState != null)
((IMemoable)digest).Reset(ipadState);
else {
digest.Reset();
digest.BlockUpdate(inputPad, 0, inputPad.Length);
}
}
private static void XorPad(byte[] pad, int len, byte n)
{
for (int i = 0; i < len; i++) {
pad[i] ^= n;
}
}
}
}