target/linux/package/ieee80211-dscape/src/aes_ccm.c

   1 /*
   2  * Copyright 2003-2004, Instant802 Networks, Inc.
   3  * Copyright 2005, Devicescape Software, Inc.
   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
  10 #include <linux/types.h>
  11 #include <linux/netdevice.h>
  12
  13 #include <net/ieee80211.h>
  14 #include "ieee80211_key.h"
  15 #include "aes_ccm.h"
  16
  17 #include "aes.c"
  18
  19 static inline void aes_ccm_prepare(u32 *rk, u8 *b_0, u8 *aad, u8 *b,
  20                                    u8 *s_0, u8 *a)
  21 {
  22         int i;
  23
  24         ieee80211_aes_encrypt(rk, b_0, b);
  25
  26         /* Extra Authenticate-only data (always two AES blocks) */
  27         for (i = 0; i < AES_BLOCK_LEN; i++)
  28                 aad[i] ^= b[i];
  29         ieee80211_aes_encrypt(rk, aad, b);
  30
  31         aad += AES_BLOCK_LEN;
  32
  33         for (i = 0; i < AES_BLOCK_LEN; i++)
  34                 aad[i] ^= b[i];
  35         ieee80211_aes_encrypt(rk, aad, a);
  36
  37         /* Mask out bits from auth-only-b_0 */
  38         b_0[0] &= 0x07;
  39
  40         /* S_0 is used to encrypt T (= MIC) */
  41         b_0[14] = 0;
  42         b_0[15] = 0;
  43         ieee80211_aes_encrypt(rk, b_0, s_0);
  44 }
  45
  46
  47 void ieee80211_aes_ccm_encrypt(u32 *rk, u8 *b_0, u8 *aad, u8 *data,
  48                                size_t data_len, u8 *cdata, u8 *mic)
  49 {
  50         int i, j, last_len, num_blocks;
  51         u8 *pos, *cpos;
  52         u8 b[AES_BLOCK_LEN], s_0[AES_BLOCK_LEN], e[AES_BLOCK_LEN];
  53
  54         num_blocks = (data_len + AES_BLOCK_LEN - 1) / AES_BLOCK_LEN;
  55         last_len = data_len % AES_BLOCK_LEN;
  56         aes_ccm_prepare(rk, b_0, aad, b, s_0, b);
  57
  58         /* Process payload blocks */
  59         pos = data;
  60         cpos = cdata;
  61         for (j = 1; j <= num_blocks; j++) {
  62                 int blen = (j == num_blocks && last_len) ?
  63                         last_len : AES_BLOCK_LEN;
  64
  65                 /* Authentication followed by encryption */
  66                 for (i = 0; i < blen; i++)
  67                         b[i] ^= pos[i];
  68                 ieee80211_aes_encrypt(rk, b, b);
  69
  70                 b_0[14] = (j >> 8) & 0xff;
  71                 b_0[15] = j & 0xff;
  72                 ieee80211_aes_encrypt(rk, b_0, e);
  73                 for (i = 0; i < blen; i++)
  74                         *cpos++ = *pos++ ^ e[i];
  75         }
  76
  77         for (i = 0; i < CCMP_MIC_LEN; i++)
  78                 mic[i] = b[i] ^ s_0[i];
  79 }
  80
  81
  82 int ieee80211_aes_ccm_decrypt(u32 *rk, u8 *b_0, u8 *aad, u8 *cdata,
  83                               size_t data_len, u8 *mic, u8 *data)
  84 {
  85         int i, j, last_len, num_blocks;
  86         u8 *pos, *cpos;
  87         u8 b[AES_BLOCK_LEN], s_0[AES_BLOCK_LEN], a[AES_BLOCK_LEN];
  88
  89         num_blocks = (data_len + AES_BLOCK_LEN - 1) / AES_BLOCK_LEN;
  90         last_len = data_len % AES_BLOCK_LEN;
  91         aes_ccm_prepare(rk, b_0, aad, b, s_0, a);
  92
  93         /* Process payload blocks */
  94         cpos = cdata;
  95         pos = data;
  96         for (j = 1; j <= num_blocks; j++) {
  97                 int blen = (j == num_blocks && last_len) ?
  98                         last_len : AES_BLOCK_LEN;
  99
 100                 /* Decryption followed by authentication */
 101                 b_0[14] = (j >> 8) & 0xff;
 102                 b_0[15] = j & 0xff;
 103                 ieee80211_aes_encrypt(rk, b_0, b);
 104                 for (i = 0; i < blen; i++) {
 105                         *pos = *cpos++ ^ b[i];
 106                         a[i] ^= *pos++;
 107                 }
 108
 109                 ieee80211_aes_encrypt(rk, a, a);
 110         }
 111
 112         for (i = 0; i < CCMP_MIC_LEN; i++) {
 113                 if ((mic[i] ^ s_0[i]) != a[i])
 114                         return -1;
 115         }
 116
 117         return 0;
 118 }
 119