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