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 #include <crypto/aes.h>
  15
  16 #include <net/mac80211.h>
  17 #include "key.h"
  18 #include "aes_ccm.h"
  19
  20 static void aes_ccm_prepare(struct crypto_cipher *tfm, u8 *scratch, u8 *a)
  21 {
  22         int i;
  23         u8 *b_0, *aad, *b, *s_0;
  24
  25         b_0 = scratch + 3 * AES_BLOCK_SIZE;
  26         aad = scratch + 4 * AES_BLOCK_SIZE;
  27         b = scratch;
  28         s_0 = scratch + AES_BLOCK_SIZE;
  29
  30         crypto_cipher_encrypt_one(tfm, b, b_0);
  31
  32         /* Extra Authenticate-only data (always two AES blocks) */
  33         for (i = 0; i < AES_BLOCK_SIZE; i++)
  34                 aad[i] ^= b[i];
  35         crypto_cipher_encrypt_one(tfm, b, aad);
  36
  37         aad += AES_BLOCK_SIZE;
  38
  39         for (i = 0; i < AES_BLOCK_SIZE; i++)
  40                 aad[i] ^= b[i];
  41         crypto_cipher_encrypt_one(tfm, a, aad);
  42
  43         /* Mask out bits from auth-only-b_0 */
  44         b_0[0] &= 0x07;
  45
  46         /* S_0 is used to encrypt T (= MIC) */
  47         b_0[14] = 0;
  48         b_0[15] = 0;
  49         crypto_cipher_encrypt_one(tfm, s_0, b_0);
  50 }
  51
  52
  53 void ieee80211_aes_ccm_encrypt(struct crypto_cipher *tfm, u8 *scratch,
  54                                u8 *data, size_t data_len,
  55                                u8 *cdata, u8 *mic)
  56 {
  57         int i, j, last_len, num_blocks;
  58         u8 *pos, *cpos, *b, *s_0, *e, *b_0;
  59
  60         b = scratch;
  61         s_0 = scratch + AES_BLOCK_SIZE;
  62         e = scratch + 2 * AES_BLOCK_SIZE;
  63         b_0 = scratch + 3 * AES_BLOCK_SIZE;
  64
  65         num_blocks = DIV_ROUND_UP(data_len, AES_BLOCK_SIZE);
  66         last_len = data_len % AES_BLOCK_SIZE;
  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_SIZE;
  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;
  98
  99         b = scratch;
 100         s_0 = scratch + AES_BLOCK_SIZE;
 101         a = scratch + 2 * AES_BLOCK_SIZE;
 102         b_0 = scratch + 3 * AES_BLOCK_SIZE;
 103
 104         num_blocks = DIV_ROUND_UP(data_len, AES_BLOCK_SIZE);
 105         last_len = data_len % AES_BLOCK_SIZE;
 106         aes_ccm_prepare(tfm, scratch, a);
 107
 108         /* Process payload blocks */
 109         cpos = cdata;
 110         pos = data;
 111         for (j = 1; j <= num_blocks; j++) {
 112                 int blen = (j == num_blocks && last_len) ?
 113                         last_len : AES_BLOCK_SIZE;
 114
 115                 /* Decryption followed by authentication */
 116                 b_0[14] = (j >> 8) & 0xff;
 117                 b_0[15] = j & 0xff;
 118                 crypto_cipher_encrypt_one(tfm, b, b_0);
 119                 for (i = 0; i < blen; i++) {
 120                         *pos = *cpos++ ^ b[i];
 121                         a[i] ^= *pos++;
 122                 }
 123                 crypto_cipher_encrypt_one(tfm, a, a);
 124         }
 125
 126         for (i = 0; i < CCMP_MIC_LEN; i++) {
 127                 if ((mic[i] ^ s_0[i]) != a[i])
 128                         return -1;
 129         }
 130
 131         return 0;
 132 }
 133
 134
 135 struct crypto_cipher *ieee80211_aes_key_setup_encrypt(const u8 key[])
 136 {
 137         struct crypto_cipher *tfm;
 138
 139         tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
 140         if (!IS_ERR(tfm))
 141                 crypto_cipher_setkey(tfm, key, ALG_CCMP_KEY_LEN);
 142
 143         return tfm;
 144 }
 145
 146
 147 void ieee80211_aes_key_free(struct crypto_cipher *tfm)
 148 {
 149         crypto_free_cipher(tfm);
 150 }