/*-
 * Copyright 2005,2007,2009 Colin Percival
 * 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 AUTHOR 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 AUTHOR 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 <limits.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#include <sys/types.h>

#include "core.h"
#include "crypto_auth_hmacsha256.h"
#include "crypto_pwhash_scryptsalsa208sha256.h"
#include "pbkdf2-sha256.h"
#include "private/common.h"
#include "utils.h"

/**
 * PBKDF2_SHA256(passwd, passwdlen, salt, saltlen, c, buf, dkLen):
 * Compute PBKDF2(passwd, salt, c, dkLen) using HMAC-SHA256 as the PRF, and
 * write the output to buf.  The value dkLen must be at most 32 * (2^32 - 1).
 */
void
PBKDF2_SHA256(const uint8_t *passwd, size_t passwdlen, const uint8_t *salt,
              size_t saltlen, uint64_t c, uint8_t *buf, size_t dkLen)
{
    crypto_auth_hmacsha256_state PShctx, hctx;
    size_t                       i;
    uint8_t                      ivec[4];
    uint8_t                      U[32];
    uint8_t                      T[32];
    uint64_t                     j;
    int                          k;
    size_t                       clen;

#if SIZE_MAX > 0x1fffffffe0ULL
    COMPILER_ASSERT(crypto_pwhash_scryptsalsa208sha256_BYTES_MAX
                    <= 0x1fffffffe0ULL);
    if (dkLen > 0x1fffffffe0ULL) {
        sodium_misuse(); /* LCOV_EXCL_LINE */
    }
#endif
    crypto_auth_hmacsha256_init(&PShctx, passwd, passwdlen);
    crypto_auth_hmacsha256_update(&PShctx, salt, saltlen);

    for (i = 0; i * 32 < dkLen; i++) {
        STORE32_BE(ivec, (uint32_t)(i + 1));
        memcpy(&hctx, &PShctx, sizeof(crypto_auth_hmacsha256_state));
        crypto_auth_hmacsha256_update(&hctx, ivec, 4);
        crypto_auth_hmacsha256_final(&hctx, U);

        memcpy(T, U, 32);
        /* LCOV_EXCL_START */
        for (j = 2; j <= c; j++) {
            crypto_auth_hmacsha256_init(&hctx, passwd, passwdlen);
            crypto_auth_hmacsha256_update(&hctx, U, 32);
            crypto_auth_hmacsha256_final(&hctx, U);

            for (k = 0; k < 32; k++) {
                T[k] ^= U[k];
            }
        }
        /* LCOV_EXCL_STOP */

        clen = dkLen - i * 32;
        if (clen > 32) {
            clen = 32;
        }
        memcpy(&buf[i * 32], T, clen);
    }
    sodium_memzero((void *) &PShctx, sizeof PShctx);
}