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 <asm/scatterlist.h>
  15
  16 #include <net/mac80211.h>
  17 #include "ieee80211_key.h"
  18 #include "aes_ccm.h"
  19
  20
  21 static void ieee80211_aes_encrypt(struct crypto_cipher *tfm,
  22                                   const u8 pt[16], u8 ct[16])
  23 {
  24         crypto_cipher_encrypt_one(tfm, ct, pt);
  25 }
  26
  27
  28 static inline void aes_ccm_prepare(struct crypto_cipher *tfm, u8 *b_0, u8 *aad,
  29                                    u8 *b, u8 *s_0, u8 *a)
  30 {
  31         int i;
  32
  33         ieee80211_aes_encrypt(tfm, b_0, b);
  34
  35         /* Extra Authenticate-only data (always two AES blocks) */
  36         for (i = 0; i < AES_BLOCK_LEN; i++)
  37                 aad[i] ^= b[i];
  38         ieee80211_aes_encrypt(tfm, aad, b);
  39
  40         aad += AES_BLOCK_LEN;
  41
  42         for (i = 0; i < AES_BLOCK_LEN; i++)
  43                 aad[i] ^= b[i];
  44         ieee80211_aes_encrypt(tfm, aad, a);
  45
  46         /* Mask out bits from auth-only-b_0 */
  47         b_0[0] &= 0x07;
  48
  49         /* S_0 is used to encrypt T (= MIC) */
  50         b_0[14] = 0;
  51         b_0[15] = 0;
  52         ieee80211_aes_encrypt(tfm, b_0, s_0);
  53 }
  54
  55
  56 void ieee80211_aes_ccm_encrypt(struct crypto_cipher *tfm, u8 *scratch,
  57                                u8 *b_0, u8 *aad, u8 *data, size_t data_len,
  58                                u8 *cdata, u8 *mic)
  59 {
  60         int i, j, last_len, num_blocks;
  61         u8 *pos, *cpos, *b, *s_0, *e;
  62
  63         b = scratch;
  64         s_0 = scratch + AES_BLOCK_LEN;
  65         e = scratch + 2 * AES_BLOCK_LEN;
  66
  67         num_blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
  68         last_len = data_len % AES_BLOCK_LEN;
  69         aes_ccm_prepare(tfm, b_0, aad, b, s_0, b);
  70
  71         /* Process payload blocks */
  72         pos = data;
  73         cpos = cdata;
  74         for (j = 1; j <= num_blocks; j++) {
  75                 int blen = (j == num_blocks && last_len) ?
  76                         last_len : AES_BLOCK_LEN;
  77
  78                 /* Authentication followed by encryption */
  79                 for (i = 0; i < blen; i++)
  80                         b[i] ^= pos[i];
  81                 ieee80211_aes_encrypt(tfm, b, b);
  82
  83                 b_0[14] = (j >> 8) & 0xff;
  84                 b_0[15] = j & 0xff;
  85                 ieee80211_aes_encrypt(tfm, b_0, e);
  86                 for (i = 0; i < blen; i++)
  87                         *cpos++ = *pos++ ^ e[i];
  88         }
  89
  90         for (i = 0; i < CCMP_MIC_LEN; i++)
  91                 mic[i] = b[i] ^ s_0[i];
  92 }
  93
  94
  95 int ieee80211_aes_ccm_decrypt(struct crypto_cipher *tfm, u8 *scratch,
  96                               u8 *b_0, u8 *aad, u8 *cdata, size_t data_len,
  97                               u8 *mic, u8 *data)
  98 {
  99         int i, j, last_len, num_blocks;
 100         u8 *pos, *cpos, *b, *s_0, *a;
 101
 102         b = scratch;
 103         s_0 = scratch + AES_BLOCK_LEN;
 104         a = scratch + 2 * AES_BLOCK_LEN;
 105
 106         num_blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
 107         last_len = data_len % AES_BLOCK_LEN;
 108         aes_ccm_prepare(tfm, b_0, aad, b, s_0, a);
 109
 110         /* Process payload blocks */
 111         cpos = cdata;
 112         pos = data;
 113         for (j = 1; j <= num_blocks; j++) {
 114                 int blen = (j == num_blocks && last_len) ?
 115                         last_len : AES_BLOCK_LEN;
 116
 117                 /* Decryption followed by authentication */
 118                 b_0[14] = (j >> 8) & 0xff;
 119                 b_0[15] = j & 0xff;
 120                 ieee80211_aes_encrypt(tfm, b_0, b);
 121                 for (i = 0; i < blen; i++) {
 122                         *pos = *cpos++ ^ b[i];
 123                         a[i] ^= *pos++;
 124                 }
 125
 126                 ieee80211_aes_encrypt(tfm, a, a);
 127         }
 128
 129         for (i = 0; i < CCMP_MIC_LEN; i++) {
 130                 if ((mic[i] ^ s_0[i]) != a[i])
 131                         return -1;
 132         }
 133
 134         return 0;
 135 }
 136
 137
 138 struct crypto_cipher * ieee80211_aes_key_setup_encrypt(const u8 key[])
 139 {
 140         struct crypto_cipher *tfm;
 141
 142         tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
 143         if (IS_ERR(tfm))
 144                 return NULL;
 145
 146         crypto_cipher_setkey(tfm, key, ALG_CCMP_KEY_LEN);
 147
 148         return tfm;
 149 }
 150
 151
 152 void ieee80211_aes_key_free(struct crypto_cipher *tfm)
 153 {
 154         if (tfm)
 155                 crypto_free_cipher(tfm);
 156 }