sha1-tprf.c

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/*
 * SHA1 T-PRF for EAP-FAST
 * 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 "crypto.h"

int sha1_t_prf(const u8 *key, size_t key_len, const char *label,
               const u8 *seed, size_t seed_len, u8 *buf, size_t buf_len)
{
        unsigned char counter = 0;
        size_t pos, plen;
        u8 hash[SHA1_MAC_LEN];
        size_t label_len = os_strlen(label);
        u8 output_len[2];
        const unsigned char *addr[5];
        size_t len[5];

        addr[0] = hash;
        len[0] = 0;
        addr[1] = (unsigned char *) label;
        len[1] = label_len + 1;
        addr[2] = seed;
        len[2] = seed_len;
        addr[3] = output_len;
        len[3] = 2;
        addr[4] = &counter;
        len[4] = 1;

        output_len[0] = (buf_len >> 8) & 0xff;
        output_len[1] = buf_len & 0xff;
        pos = 0;
        while (pos < buf_len) {
                counter++;
                plen = buf_len - pos;
                if (hmac_sha1_vector(key, key_len, 5, addr, len, hash))
                        return -1;
                if (plen >= SHA1_MAC_LEN) {
                        os_memcpy(&buf[pos], hash, SHA1_MAC_LEN);
                        pos += SHA1_MAC_LEN;
                } else {
                        os_memcpy(&buf[pos], hash, plen);
                        break;
                }
                len[0] = SHA1_MAC_LEN;
        }

        return 0;
}