Function TLS_hmac

extra/yassl/src/handshake.cpp:660–688

TLS type HAMC

// TLS type HAMC
void TLS_hmac(SSL& ssl, byte* digest, const byte* buffer, uint sz,
              ContentType content, bool verify)
{
    mySTL::auto_ptr<Digest> hmac;
    opaque seq[SEQ_SZ] = { 0x00, 0x00, 0x00, 0x00 };
    opaque length[LENGTH_SZ];
    opaque inner[SIZEOF_ENUM + VERSION_SZ + LENGTH_SZ]; // type + version + len

    c16toa(sz, length);
    c32toa(ssl.get_SEQIncrement(verify), &seq[sizeof(uint32)]);

    MACAlgorithm algo = ssl.getSecurity().get_parms().mac_algorithm_;

    if (algo == sha)
        hmac.reset(NEW_YS HMAC_SHA(ssl.get_macSecret(verify), SHA_LEN));
    else if (algo == rmd)
        hmac.reset(NEW_YS HMAC_RMD(ssl.get_macSecret(verify), RMD_LEN));
    else
        hmac.reset(NEW_YS HMAC_MD5(ssl.get_macSecret(verify), MD5_LEN));
    
    hmac->update(seq, SEQ_SZ);                                       // seq_num
    inner[0] = content;                                              // type
    inner[SIZEOF_ENUM] = ssl.getSecurity().get_connection().version_.major_;  
    inner[SIZEOF_ENUM + SIZEOF_ENUM] = 
        ssl.getSecurity().get_connection().version_.minor_;          // version
    memcpy(&inner[SIZEOF_ENUM + VERSION_SZ], length, LENGTH_SZ);     // length
    hmac->update(inner, sizeof(inner));
    hmac->get_digest(digest, buffer, sz);                            // content
}


// compute TLSv1 PRF (pseudo random function using HMAC)