sha1-pbkdf2.c

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/*
 * SHA1-based key derivation function (PBKDF2) for IEEE 802.11i
 * Copyright (c) 2003-2005, 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 "md5.h"
#include "crypto.h"

static int pbkdf2_sha1_f(const char *passphrase, const char *ssid,
                         size_t ssid_len, int iterations, unsigned int count,
                         u8 *digest)
{
        unsigned char tmp[SHA1_MAC_LEN], tmp2[SHA1_MAC_LEN];
        int i, j;
        unsigned char count_buf[4];
        const u8 *addr[2];
        size_t len[2];
        size_t passphrase_len = os_strlen(passphrase);

        addr[0] = (u8 *) ssid;
        len[0] = ssid_len;
        addr[1] = count_buf;
        len[1] = 4;

        /* F(P, S, c, i) = U1 xor U2 xor ... Uc
         * U1 = PRF(P, S || i)
         * U2 = PRF(P, U1)
         * Uc = PRF(P, Uc-1)
         */

        count_buf[0] = (count >> 24) & 0xff;
        count_buf[1] = (count >> 16) & 0xff;
        count_buf[2] = (count >> 8) & 0xff;
        count_buf[3] = count & 0xff;
        if (hmac_sha1_vector((u8 *) passphrase, passphrase_len, 2, addr, len,
                             tmp))
                return -1;
        os_memcpy(digest, tmp, SHA1_MAC_LEN);

        for (i = 1; i < iterations; i++) {
                if (hmac_sha1((u8 *) passphrase, passphrase_len, tmp,
                              SHA1_MAC_LEN, tmp2))
                        return -1;
                os_memcpy(tmp, tmp2, SHA1_MAC_LEN);
                for (j = 0; j < SHA1_MAC_LEN; j++)
                        digest[j] ^= tmp2[j];
        }

        return 0;
}


int pbkdf2_sha1(const char *passphrase, const char *ssid, size_t ssid_len,
                int iterations, u8 *buf, size_t buflen)
{
        unsigned int count = 0;
        unsigned char *pos = buf;
        size_t left = buflen, plen;
        unsigned char digest[SHA1_MAC_LEN];

        while (left > 0) {
                count++;
                if (pbkdf2_sha1_f(passphrase, ssid, ssid_len, iterations,
                                  count, digest))
                        return -1;
                plen = left > SHA1_MAC_LEN ? SHA1_MAC_LEN : left;
                os_memcpy(pos, digest, plen);
                pos += plen;
                left -= plen;
        }

        return 0;
}