net/mac80211/aes_ccm.c

   1 /*
   2  * Copyright 2003-2004, Instant802 Networks, Inc.
   3  * Copyright 2005-2006, 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/kernel.h>
  11 #include <linux/types.h>
  12 #include <linux/crypto.h>
  13 #include <linux/err.h>
  14
  15 #include <net/mac80211.h>
  16 #include "key.h"
  17 #include "aes_ccm.h"
  18
  19
  20 static void ieee80211_aes_encrypt(struct crypto_cipher *tfm,
  21                                   const u8 pt[16], u8 ct[16])
  22 {
  23         crypto_cipher_encrypt_one(tfm, ct, pt);
  24 }
  25
  26
  27 static inline void aes_ccm_prepare(struct crypto_cipher *tfm, u8 *b_0, u8 *aad,
  28                                    u8 *b, u8 *s_0, u8 *a)
  29 {
  30         int i;
  31
  32         ieee80211_aes_encrypt(tfm, b_0, b);
  33
  34         /* Extra Authenticate-only data (always two AES blocks) */
  35         for (i = 0; i < AES_BLOCK_LEN; i++)
  36                 aad[i] ^= b[i];
  37         ieee80211_aes_encrypt(tfm, aad, b);
  38
  39         aad += AES_BLOCK_LEN;
  40
  41         for (i = 0; i < AES_BLOCK_LEN; i++)
  42                 aad[i] ^= b[i];
  43         ieee80211_aes_encrypt(tfm, aad, a);
  44
  45         /* Mask out bits from auth-only-b_0 */
  46         b_0[0] &= 0x07;
  47
  48         /* S_0 is used to encrypt T (= MIC) */
  49         b_0[14] = 0;
  50         b_0[15] = 0;
  51         ieee80211_aes_encrypt(tfm, b_0, s_0);
  52 }
  53
  54
  55 void ieee80211_aes_ccm_encrypt(struct crypto_cipher *tfm, u8 *scratch,
  56                                u8 *data, size_t data_len,
  57                                u8 *cdata, u8 *mic)
  58 {
  59         int i, j, last_len, num_blocks;
  60         u8 *pos, *cpos, *b, *s_0, *e, *b_0, *aad;
  61
  62         b = scratch;
  63         s_0 = scratch + AES_BLOCK_LEN;
  64         e = scratch + 2 * AES_BLOCK_LEN;
  65         b_0 = scratch + 3 * AES_BLOCK_LEN;
  66         aad = scratch + 4 * AES_BLOCK_LEN;
  67
  68         num_blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
  69         last_len = data_len % AES_BLOCK_LEN;
  70         aes_ccm_prepare(tfm, b_0, aad, b, s_0, b);
  71
  72         /* Process payload blocks */
  73         pos = data;
  74         cpos = cdata;
  75         for (j = 1; j <= num_blocks; j++) {
  76                 int blen = (j == num_blocks && last_len) ?
  77                         last_len : AES_BLOCK_LEN;
  78
  79                 /* Authentication followed by encryption */
  80                 for (i = 0; i < blen; i++)
  81                         b[i] ^= pos[i];
  82                 ieee80211_aes_encrypt(tfm, b, b);
  83
  84                 b_0[14] = (j >> 8) & 0xff;
  85                 b_0[15] = j & 0xff;
  86                 ieee80211_aes_encrypt(tfm, b_0, e);
  87                 for (i = 0; i < blen; i++)
  88                         *cpos++ = *pos++ ^ e[i];
  89         }
  90
  91         for (i = 0; i < CCMP_MIC_LEN; i++)
  92                 mic[i] = b[i] ^ s_0[i];
  93 }
  94
  95
  96 int ieee80211_aes_ccm_decrypt(struct crypto_cipher *tfm, u8 *scratch,
  97                               u8 *cdata, size_t data_len, u8 *mic, u8 *data)
  98 {
  99         int i, j, last_len, num_blocks;
 100         u8 *pos, *cpos, *b, *s_0, *a, *b_0, *aad;
 101
 102         b = scratch;
 103         s_0 = scratch + AES_BLOCK_LEN;
 104         a = scratch + 2 * AES_BLOCK_LEN;
 105         b_0 = scratch + 3 * AES_BLOCK_LEN;
 106         aad = scratch + 4 * AES_BLOCK_LEN;
 107
 108         num_blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
 109         last_len = data_len % AES_BLOCK_LEN;
 110         aes_ccm_prepare(tfm, b_0, aad, b, s_0, a);
 111
 112         /* Process payload blocks */
 113         cpos = cdata;
 114         pos = data;
 115         for (j = 1; j <= num_blocks; j++) {
 116                 int blen = (j == num_blocks && last_len) ?
 117                         last_len : AES_BLOCK_LEN;
 118
 119                 /* Decryption followed by authentication */
 120                 b_0[14] = (j >> 8) & 0xff;
 121                 b_0[15] = j & 0xff;
 122                 ieee80211_aes_encrypt(tfm, b_0, b);
 123                 for (i = 0; i < blen; i++) {
 124                         *pos = *cpos++ ^ b[i];
 125                         a[i] ^= *pos++;
 126                 }
 127
 128                 ieee80211_aes_encrypt(tfm, a, a);
 129         }
 130
 131         for (i = 0; i < CCMP_MIC_LEN; i++) {
 132                 if ((mic[i] ^ s_0[i]) != a[i])
 133                         return -1;
 134         }
 135
 136         return 0;
 137 }
 138
 139
 140 struct crypto_cipher *ieee80211_aes_key_setup_encrypt(const u8 key[])
 141 {
 142         struct crypto_cipher *tfm;
 143
 144         tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
 145         if (IS_ERR(tfm))
 146                 return NULL;
 147
 148         crypto_cipher_setkey(tfm, key, ALG_CCMP_KEY_LEN);
 149
 150         return tfm;
 151 }
 152
 153
 154 void ieee80211_aes_key_free(struct crypto_cipher *tfm)
 155 {
 156         if (tfm)
 157                 crypto_free_cipher(tfm);
 158 }