/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS 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 AUTHORS 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.
 */

#include <sys/param.h>
#ifdef _KERNEL
#include <sys/systm.h>
#include <sys/kernel.h>
#else
#include <sys/resource.h>
#include <stdint.h>
#include <strings.h>
#endif

#include <geom/eli/g_eli.h>
#include <geom/eli/pkcs5v2.h>

static __inline void
xor(uint8_t *dst, const uint8_t *src, size_t size)
{

        for (; size > 0; size--)
                *dst++ ^= *src++;
}

void
pkcs5v2_genkey(uint8_t *key, unsigned keylen, const uint8_t *salt,
    size_t saltsize, const char *passphrase, u_int iterations)
{

        pkcs5v2_genkey_raw(key, keylen, salt, saltsize, passphrase,
            strlen(passphrase), iterations);
}

void
pkcs5v2_genkey_raw(uint8_t *key, unsigned keylen, const uint8_t *salt,
    size_t saltsize, const uint8_t *passphrase, size_t passlen,
    u_int iterations)
{
        uint8_t md[SHA512_MDLEN], saltcount[saltsize + sizeof(uint32_t)];
        uint8_t *counter, *keyp;
        u_int i, bsize;
        uint32_t count;
        struct hmac_ctx startpoint, ctx;

        bzero(key, keylen);
        bcopy(salt, saltcount, saltsize);
        counter = saltcount + saltsize;

        keyp = key;
        for (count = 1; keylen > 0; count++, keylen -= bsize, keyp += bsize) {
                bsize = MIN(keylen, sizeof(md));

                be32enc(counter, count);

                g_eli_crypto_hmac_init(&startpoint, passphrase, passlen);
                ctx = startpoint;
                g_eli_crypto_hmac_update(&ctx, saltcount, sizeof(saltcount));
                g_eli_crypto_hmac_final(&ctx, md, sizeof(md));
                xor(keyp, md, bsize);

                for(i = 1; i < iterations; i++) {
                        ctx = startpoint;
                        g_eli_crypto_hmac_update(&ctx, md, sizeof(md));
                        g_eli_crypto_hmac_final(&ctx, md, sizeof(md));
                        xor(keyp, md, bsize);
                }
        }
        explicit_bzero(&startpoint, sizeof(startpoint));
        explicit_bzero(&ctx, sizeof(ctx));
}

#ifndef _KERNEL
#ifndef _STANDALONE
/*
 * Return the number of microseconds needed for 'interations' iterations.
 */
static int
pkcs5v2_probe(int iterations)
{
        uint8_t key[G_ELI_USERKEYLEN], salt[G_ELI_SALTLEN];
        const char passphrase[] = "passphrase";
        struct rusage start, end;
        int usecs;

        getrusage(RUSAGE_SELF, &start);
        pkcs5v2_genkey(key, sizeof(key), salt, sizeof(salt), passphrase,
            iterations);
        getrusage(RUSAGE_SELF, &end);

        usecs = end.ru_utime.tv_sec - start.ru_utime.tv_sec;
        usecs *= 1000000;
        usecs += end.ru_utime.tv_usec - start.ru_utime.tv_usec;
        return (usecs);
}

/*
 * Return the number of iterations which takes 'usecs' microseconds.
 */
int
pkcs5v2_calculate(int usecs)
{
        int iterations, v;

        for (iterations = 1; ; iterations <<= 1) {
                v = pkcs5v2_probe(iterations);
                if (v > 2000000)
                        break;
        }
        return (((intmax_t)iterations * (intmax_t)usecs) / v);
}
#endif  /* !_STANDALONE */
#endif  /* !_KERNEL */