hmac_sha256.c

void hmac_sha256 (const unsigned char* input, int inputlength, unsigned char* output, unsigned int* outputlength)
{
    const EVP_MD* engine = EVP_sha256 ();

#if OPENSSL_VERSION_NUMBER < 0x10100000L
    HMAC_CTX ctx;
    HMAC_CTX_init (&ctx);
    HMAC_Init_ex (&ctx, API_SECRET_KEY, strlen (API_SECRET_KEY), engine, NULL);
    HMAC_Update (&ctx, (const unsigned char*)input, inputlength);
    HMAC_Final (&ctx, output, outputlength);
#else
    HMAC_CTX* ctx = HMAC_CTX_new ();
    HMAC_Init_ex (ctx, API_SECRET_KEY, strlen (API_SECRET_KEY), engine, NULL);
    HMAC_Update (ctx, (const unsigned char*)input, inputlength);
    HMAC_Final (ctx, output, outputlength);
    HMAC_CTX_free (ctx);
#endif
}