Function hmac

extra/yassl/src/handshake.cpp:621–656

compute SSLv3 HMAC into digest see * buffer is of sz size and includes HandShake Header but not a Record Header * verify means to check peers hmac */

 * verify means to check peers hmac
*/
void hmac(SSL& ssl, byte* digest, const byte* buffer, uint sz,
          ContentType content, bool verify)
{
    Digest& mac = ssl.useCrypto().use_digest();
    opaque inner[SHA_LEN + PAD_MD5 + SEQ_SZ + SIZEOF_ENUM + LENGTH_SZ];
    opaque outer[SHA_LEN + PAD_MD5 + SHA_LEN]; 
    opaque result[SHA_LEN];                              // max possible sizes
    uint digestSz = mac.get_digestSize();              // actual sizes
    uint padSz    = mac.get_padSize();
    uint innerSz  = digestSz + padSz + SEQ_SZ + SIZEOF_ENUM + LENGTH_SZ;
    uint outerSz  = digestSz + padSz + digestSz;

    // data
    const opaque* mac_secret = ssl.get_macSecret(verify);
    opaque seq[SEQ_SZ] = { 0x00, 0x00, 0x00, 0x00 };
    opaque length[LENGTH_SZ];
    c16toa(sz, length);
    c32toa(ssl.get_SEQIncrement(verify), &seq[sizeof(uint32)]);

    // make inner
    memcpy(inner, mac_secret, digestSz);
    memcpy(&inner[digestSz], PAD1, padSz);
    memcpy(&inner[digestSz + padSz], seq, SEQ_SZ);
    inner[digestSz + padSz + SEQ_SZ] = content;
    memcpy(&inner[digestSz + padSz + SEQ_SZ + SIZEOF_ENUM], length, LENGTH_SZ);

    mac.update(inner, innerSz);
    mac.get_digest(result, buffer, sz);      // append content buffer

    // make outer
    memcpy(outer, mac_secret, digestSz);
    memcpy(&outer[digestSz], PAD2, padSz);
    memcpy(&outer[digestSz + padSz], result, digestSz);

    mac.get_digest(digest, outer, outerSz);
}


// TLS type HAMC