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 *b_0, u8 *aad, 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;
  61
  62         b = scratch;
  63         s_0 = scratch + AES_BLOCK_LEN;
  64         e = scratch + 2 * AES_BLOCK_LEN;
  65
  66         num_blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
  67         last_len = data_len % AES_BLOCK_LEN;
  68         aes_ccm_prepare(tfm, b_0, aad, b, s_0, b);
  69
  70         /* Process payload blocks */
  71         pos = data;
  72         cpos = cdata;
  73         for (j = 1; j <= num_blocks; j++) {
  74                 int blen = (j == num_blocks && last_len) ?
  75                         last_len : AES_BLOCK_LEN;
  76
  77                 /* Authentication followed by encryption */
  78                 for (i = 0; i < blen; i++)
  79                         b[i] ^= pos[i];
  80                 ieee80211_aes_encrypt(tfm, b, b);
  81
  82                 b_0[14] = (j >> 8) & 0xff;
  83                 b_0[15] = j & 0xff;
  84                 ieee80211_aes_encrypt(tfm, b_0, e);
  85                 for (i = 0; i < blen; i++)
  86                         *cpos++ = *pos++ ^ e[i];
  87         }
  88
  89         for (i = 0; i < CCMP_MIC_LEN; i++)
  90                 mic[i] = b[i] ^ s_0[i];
  91 }
  92
  93
  94 int ieee80211_aes_ccm_decrypt(struct crypto_cipher *tfm, u8 *scratch,
  95                               u8 *b_0, u8 *aad, u8 *cdata, size_t data_len,
  96                               u8 *mic, u8 *data)
  97 {
  98         int i, j, last_len, num_blocks;
  99         u8 *pos, *cpos, *b, *s_0, *a;
 100
 101         b = scratch;
 102         s_0 = scratch + AES_BLOCK_LEN;
 103         a = scratch + 2 * 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, b_0, aad, b, s_0, 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                 ieee80211_aes_encrypt(tfm, b_0, b);
 120                 for (i = 0; i < blen; i++) {
 121                         *pos = *cpos++ ^ b[i];
 122                         a[i] ^= *pos++;
 123                 }
 124
 125                 ieee80211_aes_encrypt(tfm, a, a);
 126         }
 127
 128         for (i = 0; i < CCMP_MIC_LEN; i++) {
 129                 if ((mic[i] ^ s_0[i]) != a[i])
 130                         return -1;
 131         }
 132
 133         return 0;
 134 }
 135
 136
 137 struct crypto_cipher *ieee80211_aes_key_setup_encrypt(const u8 key[])
 138 {
 139         struct crypto_cipher *tfm;
 140
 141         tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
 142         if (IS_ERR(tfm))
 143                 return NULL;
 144
 145         crypto_cipher_setkey(tfm, key, ALG_CCMP_KEY_LEN);
 146
 147         return tfm;
 148 }
 149
 150
 151 void ieee80211_aes_key_free(struct crypto_cipher *tfm)
 152 {
 153         if (tfm)
 154                 crypto_free_cipher(tfm);
 155 }