fips_prf_internal.c

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/*
 * FIPS 186-2 PRF for internal crypto implementation
 * Copyright (c) 2006-2007, Jouni Malinen <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 */

#include "includes.h"

#include "common.h"
#include "sha1.h"
#include "sha1_i.h"
#include "crypto.h"


int fips186_2_prf(const u8 *seed, size_t seed_len, u8 *x, size_t xlen)
{
        u8 xkey[64];
        u32 t[5], _t[5];
        int i, j, m, k;
        u8 *xpos = x;
        u32 carry;

        if (seed_len > sizeof(xkey))
                seed_len = sizeof(xkey);

        /* FIPS 186-2 + change notice 1 */

        os_memcpy(xkey, seed, seed_len);
        os_memset(xkey + seed_len, 0, 64 - seed_len);
        t[0] = 0x67452301;
        t[1] = 0xEFCDAB89;
        t[2] = 0x98BADCFE;
        t[3] = 0x10325476;
        t[4] = 0xC3D2E1F0;

        m = xlen / 40;
        for (j = 0; j < m; j++) {
                /* XSEED_j = 0 */
                for (i = 0; i < 2; i++) {
                        /* XVAL = (XKEY + XSEED_j) mod 2^b */

                        /* w_i = G(t, XVAL) */
                        os_memcpy(_t, t, 20);
                        SHA1Transform(_t, xkey);
                        _t[0] = host_to_be32(_t[0]);
                        _t[1] = host_to_be32(_t[1]);
                        _t[2] = host_to_be32(_t[2]);
                        _t[3] = host_to_be32(_t[3]);
                        _t[4] = host_to_be32(_t[4]);
                        os_memcpy(xpos, _t, 20);

                        /* XKEY = (1 + XKEY + w_i) mod 2^b */
                        carry = 1;
                        for (k = 19; k >= 0; k--) {
                                carry += xkey[k] + xpos[k];
                                xkey[k] = carry & 0xff;
                                carry >>= 8;
                        }

                        xpos += SHA1_MAC_LEN;
                }
                /* x_j = w_0|w_1 */
        }

        return 0;
}