src/eap_common/eap_psk_common.c

   1 /*
   2  * EAP server/peer: EAP-PSK shared routines
   3  * Copyright (c) 2004-2006, Jouni Malinen <j@w1.fi>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  *
   9  * Alternatively, this software may be distributed under the terms of BSD
  10  * license.
  11  *
  12  * See README and COPYING for more details.
  13  */
  14
  15 #include "includes.h"
  16
  17 #include "common.h"
  18 #include "crypto/aes_wrap.h"
  19 #include "eap_defs.h"
  20 #include "eap_psk_common.h"
  21
  22 #define aes_block_size 16
  23
  24
  25 int eap_psk_key_setup(const u8 *psk, u8 *ak, u8 *kdk)
  26 {
  27         os_memset(ak, 0, aes_block_size);
  28         if (aes_128_encrypt_block(psk, ak, ak))
  29                 return -1;
  30         os_memcpy(kdk, ak, aes_block_size);
  31         ak[aes_block_size - 1] ^= 0x01;
  32         kdk[aes_block_size - 1] ^= 0x02;
  33         if (aes_128_encrypt_block(psk, ak, ak) ||
  34             aes_128_encrypt_block(psk, kdk, kdk))
  35                 return -1;
  36         return 0;
  37 }
  38
  39
  40 int eap_psk_derive_keys(const u8 *kdk, const u8 *rand_p, u8 *tek, u8 *msk,
  41                         u8 *emsk)
  42 {
  43         u8 hash[aes_block_size];
  44         u8 counter = 1;
  45         int i;
  46
  47         if (aes_128_encrypt_block(kdk, rand_p, hash))
  48                 return -1;
  49
  50         hash[aes_block_size - 1] ^= counter;
  51         if (aes_128_encrypt_block(kdk, hash, tek))
  52                 return -1;
  53         hash[aes_block_size - 1] ^= counter;
  54         counter++;
  55
  56         for (i = 0; i < EAP_MSK_LEN / aes_block_size; i++) {
  57                 hash[aes_block_size - 1] ^= counter;
  58                 if (aes_128_encrypt_block(kdk, hash, &msk[i * aes_block_size]))
  59                         return -1;
  60                 hash[aes_block_size - 1] ^= counter;
  61                 counter++;
  62         }
  63
  64         for (i = 0; i < EAP_EMSK_LEN / aes_block_size; i++) {
  65                 hash[aes_block_size - 1] ^= counter;
  66                 if (aes_128_encrypt_block(kdk, hash,
  67                                           &emsk[i * aes_block_size]))
  68                         return -1;
  69                 hash[aes_block_size - 1] ^= counter;
  70                 counter++;
  71         }
  72
  73         return 0;
  74 }