CPipeHMAC_SHA1.cpp

Go to the documentation of this file.

#include "stdafx.h"
#include "CPipeHMAC_SHA1.h"

// Make for some more convenient notation below
// using AxPipe::Stock::CPipeHMAC_SHA1;
// using AxPipe::Stock::TBits;
namespace AxPipe {
    namespace Stock {
        // Instantiate explicitly to generate code for supported bit-lengths.
        template CPipeHMAC_SHA1<128>;       
        template CPipeHMAC_SHA1<160>;       

        template<int iBits> void
        CPipeHMAC_SHA1<iBits>::XorPad(unsigned char oPad) {
            for  (int i=0; i < sizeof m_HMAC; i++) {
                ((unsigned char *)&m_HMAC)[i] = oPad;
                if (i < sizeof m_Key) {
                    ((unsigned char *)&m_HMAC)[i] ^= ((unsigned char *)&m_Key)[i];
                }
            }
        }

        template<int iBits> CPipeHMAC_SHA1<iBits> *
        CPipeHMAC_SHA1<iBits>::Init(TBits<iBits> *pKey, size_t cbOffset) {
            CopyMemory(&m_Key, pKey, sizeof m_Key);
            m_cbOffset = cbOffset;          // Number of bytes to skip before starting to HMAC
            return this;
        }

        template<int iBits> void
        CPipeHMAC_SHA1<iBits>::Out(AxPipe::CSeg *pSeg) {
            if (pSeg->Len() <= m_cbOffset) {
                m_cbOffset -= pSeg->Len();
                Pump(pSeg);
            } else {
                if (m_cbOffset) {
                    CSeg *pPartialSeg = pSeg->Clone();
                    pPartialSeg->Len(m_cbOffset);
                    Pump(pPartialSeg);

                    pSeg->Drop(m_cbOffset);
                    m_cbOffset = 0;
                }
                CPipeSHA1::Out(pSeg);
            }
        }

        template<int iBits> bool
        CPipeHMAC_SHA1<iBits>::OutOpen() {
            bool fReturn = CPipeSHA1::OutOpen();

            // K xor ipad
            XorPad(0x36);

            // Hash(iPad xor Key)
            ASSAPI(CryptHashData(m_hHash, (unsigned char *)&m_HMAC, sizeof m_HMAC, 0));
            
            return fReturn;
        }

        template<int iBits> bool
        CPipeHMAC_SHA1<iBits>::OutClose() {
            // Save the inner hash
            TBits<160> innerHash;
            DWORD dwHashLen = sizeof innerHash;
            ASSAPI(CryptGetHashParam(m_hHash, HP_HASHVAL, (unsigned char *)&innerHash, &dwHashLen, 0));

            // Re-initialize our hash-object.
            CryptDestroyHash(m_hHash); 
            ASSAPI(CryptCreateHash(m_hCryptProv, CALG_SHA1, 0, 0, &m_hHash));

            // K xor opad
            XorPad(0x5c);

            // Hash(oPad xor Key)
            ASSAPI(CryptHashData(m_hHash, (unsigned char *)&m_HMAC, sizeof m_HMAC, 0));

            // Hash(InnerHash)
            ASSAPI(CryptHashData(m_hHash, (unsigned char *)&innerHash, sizeof innerHash, 0));

            // Prepare the final hash as output.
            return CPipeSHA1::OutClose();
        }
    }
}

---