src/crypto/fips_prf_internal.c

/*
 * FIPS 186-2 PRF for internal crypto implementation
 * Copyright (c) 2006-2007, Jouni Malinen <j@w1.fi>
 *
 * This software may be distributed under the terms of the BSD license.
 * See README 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];
	int i, j, m, k;
	u8 *xpos = x;
	u32 carry;
	struct SHA1Context ctx;

	if (seed_len < sizeof(xkey))
		os_memset(xkey + seed_len, 0, sizeof(xkey) - seed_len);
	else
		seed_len = sizeof(xkey);

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

	os_memcpy(xkey, seed, seed_len);
	SHA1Init(&ctx);

	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, ctx.state, 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;
}