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using System;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Crypto.Macs
{
/**
* HMAC implementation based on RFC2104
*
* H(K XOR opad, H(K XOR ipad, text))
*/
public class HMac
: IMac
{
private const byte IPAD = (byte)0x36;
private const byte OPAD = (byte)0x5C;
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 HMac(IDigest digest)
{
this.digest = digest;
this.digestSize = digest.GetDigestSize();
this.blockLength = digest.GetByteLength();
this.inputPad = new byte[blockLength];
this.outputBuf = new byte[blockLength + digestSize];
}
public virtual string AlgorithmName
{
get { return digest.AlgorithmName + "/HMAC"; }
}
public virtual IDigest GetUnderlyingDigest()
{
return digest;
}
public virtual void Init(ICipherParameters parameters)
{
digest.Reset();
byte[] key = ((KeyParameter)parameters).GetKey();
int keyLength = key.Length;
if (keyLength > blockLength)
{
digest.BlockUpdate(key, 0, keyLength);
digest.DoFinal(inputPad, 0);
keyLength = digestSize;
}
else
{
Array.Copy(key, 0, inputPad, 0, keyLength);
}
Array.Clear(inputPad, keyLength, blockLength - keyLength);
Array.Copy(inputPad, 0, outputBuf, 0, blockLength);
XorPad(inputPad, blockLength, IPAD);
XorPad(outputBuf, blockLength, OPAD);
if (digest is IMemoable)
{
opadState = ((IMemoable)digest).Copy();
((IDigest)opadState).BlockUpdate(outputBuf, 0, blockLength);
}
digest.BlockUpdate(inputPad, 0, inputPad.Length);
if (digest is IMemoable)
{
ipadState = ((IMemoable)digest).Copy();
}
}
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);
}
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
public virtual void BlockUpdate(ReadOnlySpan<byte> input)
{
digest.BlockUpdate(input);
}
#endif
public virtual int DoFinal(byte[] output, int outOff)
{
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
return DoFinal(output.AsSpan(outOff));
#else
digest.DoFinal(outputBuf, blockLength);
if (opadState != null)
{
((IMemoable)digest).Reset(opadState);
digest.BlockUpdate(outputBuf, blockLength, digestSize);
}
else
{
digest.BlockUpdate(outputBuf, 0, outputBuf.Length);
}
int len = digest.DoFinal(output, outOff);
Array.Clear(outputBuf, blockLength, digestSize);
if (ipadState != null)
{
((IMemoable)digest).Reset(ipadState);
}
else
{
digest.BlockUpdate(inputPad, 0, inputPad.Length);
}
return len;
#endif
}
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
public virtual int DoFinal(Span<byte> output)
{
digest.DoFinal(outputBuf.AsSpan(blockLength));
if (opadState != null)
{
((IMemoable)digest).Reset(opadState);
digest.BlockUpdate(outputBuf.AsSpan(blockLength, digestSize));
}
else
{
digest.BlockUpdate(outputBuf);
}
int len = digest.DoFinal(output);
Array.Clear(outputBuf, blockLength, digestSize);
if (ipadState != null)
{
((IMemoable)digest).Reset(ipadState);
}
else
{
digest.BlockUpdate(inputPad);
}
return len;
}
#endif
/**
* Reset the mac generator.
*/
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;
}
}
}
}
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