shmac.cpp

伯克利做的SFTP安全文件传输协议

// shmac.cc
// code for shmac.h
// copyright SafeTP Development Group, Inc., 2000  Terms of use are as specified in license.txt
// Scott McPeak's transmogrify of Wei Dai's public domain code

#include "shmac.h"      // this module
#include "cryptlib.h"   // HashModule


HMAC::HMAC(HashModule &h,
           const byte *userKey, unsigned int keylength)
	: k_ipad(h.DataSize()), k_opad(h.DataSize()),
          hash(h)
{
	int ds = DataSize();
        byte *tempKey = NULL;

        if (keylength > (unsigned)ds) {
          // RFC 2202's source code and test vectors indicate we are
          // supposed to hash the key if it is longer than the
          // hash's block size; Wei Dai's code didn't do this
          tempKey = new byte[h.DigestSize()];

          // hash userKey into tempKey
          hash.CalculateDigest(tempKey, userKey, keylength);

          // point userKey at tempKey, so we use the key's hash instead
          userKey = tempKey;
          keylength = h.DigestSize();

          // NOTE: I had a tricky bug in here where I was using 'ds' instead
          //       of h.DigestSize().  It should be digest size.  See RFC2202,
          //       in particular its accompanying source code.  (When you get
          //       down to it, source code specs rock!  So do automated test
          //       suites, which detected the error in the first place....)
        }

	memset(k_ipad, IPAD, ds);
	xorbuf(k_ipad, userKey, keylength);

	memset(k_opad, OPAD, ds);
	xorbuf(k_opad, userKey, keylength);

	Init();

        if (tempKey != NULL) {
          delete[] tempKey;
        }
}


void HMAC::Init()
{
	hash.Update(k_ipad, DataSize());
}


void HMAC::Update(const byte *input, unsigned int length)
{
	hash.Update(input, length);
}


void HMAC::Final(byte *mac)
{
	hash.Final(mac);

	hash.Update(k_opad, DataSize());
	hash.Update(mac, DigestSize());
	hash.Final(mac);
	Init();
}


unsigned int HMAC::DigestSize() const
{
  return hash.DigestSize();
}

unsigned int HMAC::DataSize() const
{
  return hash.DataSize();
}