/*
 * Copyright (C) 2011-2018 Intel Corporation. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in
 *     the documentation and/or other materials provided with the
 *     distribution.
 *   * Neither the name of Intel Corporation nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */


/* Please add external/rdrand into INCLUDE path and correpondent library to project */

#include <stdint.h>
#include <memory.h>
#include <stdlib.h>
#include "sgx.h"
#include "sgx_defs.h"
#include "se_wrapper.h"
#include "rdrand.h"
#include "cpuid.h"
#include <stdio.h>
#ifndef UINT32_MAX
#define UINT32_MAX 0xFFFFFFFFU
#endif

static int g_is_rdrand_supported=-1;

#define RDRAND_MASK     0x40000000

static int rdrand_cpuid()
{
    int info[4] = {-1, -1, -1, -1};

    /* Are we on an Intel processor? */

    __cpuid(info, 0);

    if (memcmp(&info[1], "Genu", 4) != 0 ||
        memcmp(&info[3], "ineI", 4) != 0 ||
        memcmp(&info[2], "ntel", 4) != 0 ) {
            return 0;
    }

   /* Do we have RDRAND? */

    __cpuid(info, /*feature bits*/1);

    int ecx = info[2];
    if ((ecx & RDRAND_MASK) == RDRAND_MASK)
         return 1;
    else
         return 0;
}


extern "C" sgx_status_t SGXAPI sgx_read_rand(uint8_t *buf, size_t size)
{
    if(buf == NULL || size == 0 || size> UINT32_MAX ){
        return SGX_ERROR_INVALID_PARAMETER;
    }
    if(g_is_rdrand_supported==-1){
        g_is_rdrand_supported = rdrand_cpuid();
    }
    if(!g_is_rdrand_supported){
        uint32_t i;
        for(i=0;i<(uint32_t)size;++i){
            buf[i]=(uint8_t)rand();
        }
    }else{
        int rd_ret =rdrand_get_bytes((uint32_t)size, buf);
        if(rd_ret != RDRAND_SUCCESS){
            rd_ret = rdrand_get_bytes((uint32_t)size, buf);
            if(rd_ret != RDRAND_SUCCESS){
                return SGX_ERROR_UNEXPECTED;
            }
        }
    }
    return SGX_SUCCESS;
}