/*      $OpenBSD: efirng.c,v 1.2 2021/06/25 17:49:49 krw Exp $  */

/*
 * Copyright (c) 2018 Mark Kettenis <kettenis@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/param.h>

#include <efi.h>
#include <efiapi.h>

#include "libsa.h"

extern EFI_BOOT_SERVICES        *BS;

/* Random Number Generator Protocol */

#define EFI_RNG_PROTOCOL_GUID \
    { 0x3152bca5, 0xeade, 0x433d, {0x86, 0x2e, 0xc0, 0x1c, 0xdc, 0x29, 0x1f, 0x44} }

INTERFACE_DECL(_EFI_RNG_PROTOCOL);

typedef EFI_GUID EFI_RNG_ALGORITHM;

typedef
EFI_STATUS
(EFIAPI *EFI_RNG_GET_INFO) (
    IN struct _EFI_RNG_PROTOCOL         *This,
    IN  OUT UINTN                       *RNGAlgorithmListSize,
    OUT EFI_RNG_ALGORITHM               *RNGAlgorithmList
    );

typedef
EFI_STATUS
(EFIAPI *EFI_RNG_GET_RNG) (
    IN struct _EFI_RNG_PROTOCOL         *This,
    IN EFI_RNG_ALGORITHM                *RNGAlgorithm, OPTIONAL
    IN UINTN                            RNGValueLength,
    OUT UINT8                           *RNGValue
    );

typedef struct _EFI_RNG_PROTOCOL {
        EFI_RNG_GET_INFO        GetInfo;
        EFI_RNG_GET_RNG         GetRNG;
} EFI_RNG_PROTOCOL;

static EFI_GUID                 rng_guid = EFI_RNG_PROTOCOL_GUID;

int
fwrandom(char *buf, size_t buflen)
{
        EFI_STATUS               status;
        EFI_RNG_PROTOCOL        *rng = NULL;
        UINT8                   *random;
        size_t                   i;
        int                      ret = 0;

        status = BS->LocateProtocol(&rng_guid, NULL, (void **)&rng);
        if (rng == NULL || EFI_ERROR(status))
                return -1;

        random = alloc(buflen);

        status = rng->GetRNG(rng, NULL, buflen, random);
        if (EFI_ERROR(status)) {
                printf("RNG GetRNG() failed (%d)\n", status);
                ret = -1;
                goto out;
        }

        for (i = 0; i < buflen; i++)
                buf[i] ^= random[i];

out:
        free(random, buflen);
        return ret;
}