linux/net/mac80211/aes_ccm.c
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   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
  20static 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
  53void 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
  93int 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
 135struct 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
 147void ieee80211_aes_key_free(struct crypto_cipher *tfm)
 148{
 149        crypto_free_cipher(tfm);
 150}
 151
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