private byte[] ComputeHeaderHmac(byte[] pbHeader, byte[] pbKey)
{
byte[] pbHeaderHmac;
byte[] pbBlockKey = HmacBlockStream.GetHmacKey64(
pbKey, ulong.MaxValue);
using(HMACSHA256 h = new HMACSHA256(pbBlockKey))
{
pbHeaderHmac = h.ComputeHash(pbHeader);
}
MemUtil.ZeroByteArray(pbBlockKey);
return pbHeaderHmac;
}
private void WriteSafeBlock()
{
byte[] pbBlockIndex = MemUtil.UInt64ToBytes(m_uBlockIndex);
int cbBlockSize = m_iBufferPos;
byte[] pbBlockSize = MemUtil.Int32ToBytes(cbBlockSize);
byte[] pbBlockHmac;
byte[] pbBlockKey = GetHmacKey64(m_pbKey, m_uBlockIndex);
using (HMACSHA256 h = new HMACSHA256(pbBlockKey))
{
h.TransformBlock(pbBlockIndex, 0, pbBlockIndex.Length,
pbBlockIndex, 0);
h.TransformBlock(pbBlockSize, 0, pbBlockSize.Length,
pbBlockSize, 0);
if (cbBlockSize > 0)
{
h.TransformBlock(m_pbBuffer, 0, cbBlockSize, m_pbBuffer, 0);
}
h.TransformFinalBlock(MemUtil.EmptyByteArray, 0, 0);
pbBlockHmac = h.Hash;
}
MemUtil.ZeroByteArray(pbBlockKey);
MemUtil.Write(m_sBase, pbBlockHmac);
// MemUtil.Write(m_sBase, pbBlockIndex); // Implicit
MemUtil.Write(m_sBase, pbBlockSize);
if (cbBlockSize > 0)
{
m_sBase.Write(m_pbBuffer, 0, cbBlockSize);
}
++m_uBlockIndex;
m_iBufferPos = 0;
}
private bool ReadSafeBlock()
{
if (m_bEos)
{
return(false); // End of stream reached already
}
byte[] pbStoredHmac = MemUtil.Read(m_sBase, 32);
if ((pbStoredHmac == null) || (pbStoredHmac.Length != 32))
{
throw new EndOfStreamException(KLRes.FileCorrupted + " " +
KLRes.FileIncomplete);
}
// Block index is implicit: it's used in the HMAC computation,
// but does not need to be stored
// byte[] pbBlockIndex = MemUtil.Read(m_sBase, 8);
// if((pbBlockIndex == null) || (pbBlockIndex.Length != 8))
// throw new EndOfStreamException();
// ulong uBlockIndex = MemUtil.BytesToUInt64(pbBlockIndex);
// if((uBlockIndex != m_uBlockIndex) && m_bVerify)
// throw new InvalidDataException();
byte[] pbBlockIndex = MemUtil.UInt64ToBytes(m_uBlockIndex);
byte[] pbBlockSize = MemUtil.Read(m_sBase, 4);
if ((pbBlockSize == null) || (pbBlockSize.Length != 4))
{
throw new EndOfStreamException(KLRes.FileCorrupted + " " +
KLRes.FileIncomplete);
}
int nBlockSize = MemUtil.BytesToInt32(pbBlockSize);
if (nBlockSize < 0)
{
throw new InvalidDataException(KLRes.FileCorrupted);
}
m_iBufferPos = 0;
m_pbBuffer = MemUtil.Read(m_sBase, nBlockSize);
if ((m_pbBuffer == null) || ((m_pbBuffer.Length != nBlockSize) && m_bVerify))
{
throw new EndOfStreamException(KLRes.FileCorrupted + " " +
KLRes.FileIncompleteExpc);
}
if (m_bVerify)
{
byte[] pbCmpHmac;
byte[] pbBlockKey = GetHmacKey64(m_pbKey, m_uBlockIndex);
using (HMACSHA256 h = new HMACSHA256(pbBlockKey))
{
h.TransformBlock(pbBlockIndex, 0, pbBlockIndex.Length,
pbBlockIndex, 0);
h.TransformBlock(pbBlockSize, 0, pbBlockSize.Length,
pbBlockSize, 0);
if (m_pbBuffer.Length > 0)
{
h.TransformBlock(m_pbBuffer, 0, m_pbBuffer.Length,
m_pbBuffer, 0);
}
h.TransformFinalBlock(MemUtil.EmptyByteArray, 0, 0);
pbCmpHmac = h.Hash;
}
MemUtil.ZeroByteArray(pbBlockKey);
if (!MemUtil.ArraysEqual(pbCmpHmac, pbStoredHmac))
{
throw new InvalidDataException(KLRes.FileCorrupted);
}
}
++m_uBlockIndex;
if (nBlockSize == 0)
{
m_bEos = true;
return(false); // No further data available
}
return(true);
}
/// <summary>
/// Create a cryptographic key of length <paramref name="cbOut" />
/// (in bytes) from <paramref name="pbIn" />.
/// </summary>
public static byte[] ResizeKey(byte[] pbIn, int iInOffset,
int cbIn, int cbOut)
{
if (pbIn == null)
{
throw new ArgumentNullException("pbIn");
}
if (cbOut < 0)
{
throw new ArgumentOutOfRangeException("cbOut");
}
if (cbOut == 0)
{
return(MemUtil.EmptyByteArray);
}
byte[] pbHash;
if (cbOut <= 32)
{
pbHash = HashSha256(pbIn, iInOffset, cbIn);
}
else
{
using (SHA512Managed h = new SHA512Managed())
{
pbHash = h.ComputeHash(pbIn, iInOffset, cbIn);
}
}
if (cbOut == pbHash.Length)
{
return(pbHash);
}
byte[] pbRet = new byte[cbOut];
if (cbOut < pbHash.Length)
{
Array.Copy(pbHash, pbRet, cbOut);
}
else
{
int iPos = 0;
ulong r = 0;
while (iPos < cbOut)
{
Debug.Assert(pbHash.Length == 64);
using (HMACSHA256 h = new HMACSHA256(pbHash))
{
byte[] pbR = MemUtil.UInt64ToBytes(r);
byte[] pbPart = h.ComputeHash(pbR);
int cbCopy = Math.Min(cbOut - iPos, pbPart.Length);
Debug.Assert(cbCopy > 0);
Array.Copy(pbPart, 0, pbRet, iPos, cbCopy);
iPos += cbCopy;
++r;
MemUtil.ZeroByteArray(pbPart);
}
}
Debug.Assert(iPos == cbOut);
}
#if DEBUG
byte[] pbZero = new byte[pbHash.Length];
Debug.Assert(!MemUtil.ArraysEqual(pbHash, pbZero));
#endif
MemUtil.ZeroByteArray(pbHash);
return(pbRet);
}
