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;
  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
  64         num_blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
  65         last_len = data_len % AES_BLOCK_LEN;
  66         aes_ccm_prepare(tfm, scratch, b);
  67
  68         /* Process payload blocks */
  69         pos = data;
  70         cpos = cdata;
  71         for (j = 1; j <= num_blocks; j++) {
  72                 int blen = (j == num_blocks && last_len) ?
  73                         last_len : AES_BLOCK_LEN;
  74
  75                 /* Authentication followed by encryption */
  76                 for (i = 0; i < blen; i++)
  77                         b[i] ^= pos[i];
  78                 crypto_cipher_encrypt_one(tfm, b, b);
  79
  80                 b_0[14] = (j >> 8) & 0xff;
  81                 b_0[15] = j & 0xff;
  82                 crypto_cipher_encrypt_one(tfm, e, b_0);
  83                 for (i = 0; i < blen; i++)
  84                         *cpos++ = *pos++ ^ e[i];
  85         }
  86
  87         for (i = 0; i < CCMP_MIC_LEN; i++)
  88                 mic[i] = b[i] ^ s_0[i];
  89 }
  90
  91
  92 int ieee80211_aes_ccm_decrypt(struct crypto_cipher *tfm, u8 *scratch,
  93                               u8 *cdata, size_t data_len, u8 *mic, u8 *data)
  94 {
  95         int i, j, last_len, num_blocks;
  96         u8 *pos, *cpos, *b, *s_0, *a, *b_0;
  97
  98         b = scratch;
  99         s_0 = scratch + AES_BLOCK_LEN;
 100         a = scratch + 2 * AES_BLOCK_LEN;
 101         b_0 = scratch + 3 * AES_BLOCK_LEN;
 102
 103         num_blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
 104         last_len = data_len % AES_BLOCK_LEN;
 105         aes_ccm_prepare(tfm, scratch, a);
 106
 107         /* Process payload blocks */
 108         cpos = cdata;
 109         pos = data;
 110         for (j = 1; j <= num_blocks; j++) {
 111                 int blen = (j == num_blocks && last_len) ?
 112                         last_len : AES_BLOCK_LEN;
 113
 114                 /* Decryption followed by authentication */
 115                 b_0[14] = (j >> 8) & 0xff;
 116                 b_0[15] = j & 0xff;
 117                 crypto_cipher_encrypt_one(tfm, b, b_0);
 118                 for (i = 0; i < blen; i++) {
 119                         *pos = *cpos++ ^ b[i];
 120                         a[i] ^= *pos++;
 121                 }
 122                 crypto_cipher_encrypt_one(tfm, a, a);
 123         }
 124
 125         for (i = 0; i < CCMP_MIC_LEN; i++) {
 126                 if ((mic[i] ^ s_0[i]) != a[i])
 127                         return -1;
 128         }
 129
 130         return 0;
 131 }
 132
 133
 134 struct crypto_cipher *ieee80211_aes_key_setup_encrypt(const u8 key[])
 135 {
 136         struct crypto_cipher *tfm;
 137
 138         tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
 139         if (!IS_ERR(tfm))
 140                 crypto_cipher_setkey(tfm, key, ALG_CCMP_KEY_LEN);
 141
 142         return tfm;
 143 }
 144
 145
 146 void ieee80211_aes_key_free(struct crypto_cipher *tfm)
 147 {
 148         crypto_free_cipher(tfm);
 149 }