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
  15#include <net/mac80211.h>
  16#include "key.h"
  17#include "aes_ccm.h"
  18
  19static 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
  52void 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, *aad;
  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        aad = scratch + 4 * AES_BLOCK_LEN;
  64
  65        num_blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
  66        last_len = data_len % AES_BLOCK_LEN;
  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_LEN;
  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, *aad;
  98
  99        b = scratch;
 100        s_0 = scratch + AES_BLOCK_LEN;
 101        a = scratch + 2 * AES_BLOCK_LEN;
 102        b_0 = scratch + 3 * AES_BLOCK_LEN;
 103        aad = scratch + 4 * 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, scratch, 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                crypto_cipher_encrypt_one(tfm, b, b_0);
 120                for (i = 0; i < blen; i++) {
 121                        *pos = *cpos++ ^ b[i];
 122                        a[i] ^= *pos++;
 123                }
 124                crypto_cipher_encrypt_one(tfm, a, a);
 125        }
 126
 127        for (i = 0; i < CCMP_MIC_LEN; i++) {
 128                if ((mic[i] ^ s_0[i]) != a[i])
 129                        return -1;
 130        }
 131
 132        return 0;
 133}
 134
 135
 136struct crypto_cipher *ieee80211_aes_key_setup_encrypt(const u8 key[])
 137{
 138        struct crypto_cipher *tfm;
 139
 140        tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
 141        if (IS_ERR(tfm))
 142                return NULL;
 143
 144        crypto_cipher_setkey(tfm, key, ALG_CCMP_KEY_LEN);
 145
 146        return tfm;
 147}
 148
 149
 150void ieee80211_aes_key_free(struct crypto_cipher *tfm)
 151{
 152        if (tfm)
 153                crypto_free_cipher(tfm);
 154}
 155