net/mac80211/aes_cmac.c

   1 /*
   2  * AES-128-CMAC with TLen 16 for IEEE 802.11w BIP
   3  * Copyright 2008, Jouni Malinen <j@w1.fi>
   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_cmac.h"
  19
  20 #define AES_CMAC_KEY_LEN 16
  21 #define CMAC_TLEN 8 /* CMAC TLen = 64 bits (8 octets) */
  22 #define AAD_LEN 20
  23
  24
  25 static void gf_mulx(u8 *pad)
  26 {
  27         int i, carry;
  28
  29         carry = pad[0] & 0x80;
  30         for (i = 0; i < AES_BLOCK_SIZE - 1; i++)
  31                 pad[i] = (pad[i] << 1) | (pad[i + 1] >> 7);
  32         pad[AES_BLOCK_SIZE - 1] <<= 1;
  33         if (carry)
  34                 pad[AES_BLOCK_SIZE - 1] ^= 0x87;
  35 }
  36
  37
  38 static void aes_128_cmac_vector(struct crypto_cipher *tfm, size_t num_elem,
  39                                 const u8 *addr[], const size_t *len, u8 *mac)
  40 {
  41         u8 scratch[2 * AES_BLOCK_SIZE];
  42         u8 *cbc, *pad;
  43         const u8 *pos, *end;
  44         size_t i, e, left, total_len;
  45
  46         cbc = scratch;
  47         pad = scratch + AES_BLOCK_SIZE;
  48
  49         memset(cbc, 0, AES_BLOCK_SIZE);
  50
  51         total_len = 0;
  52         for (e = 0; e < num_elem; e++)
  53                 total_len += len[e];
  54         left = total_len;
  55
  56         e = 0;
  57         pos = addr[0];
  58         end = pos + len[0];
  59
  60         while (left >= AES_BLOCK_SIZE) {
  61                 for (i = 0; i < AES_BLOCK_SIZE; i++) {
  62                         cbc[i] ^= *pos++;
  63                         if (pos >= end) {
  64                                 e++;
  65                                 pos = addr[e];
  66                                 end = pos + len[e];
  67                         }
  68                 }
  69                 if (left > AES_BLOCK_SIZE)
  70                         crypto_cipher_encrypt_one(tfm, cbc, cbc);
  71                 left -= AES_BLOCK_SIZE;
  72         }
  73
  74         memset(pad, 0, AES_BLOCK_SIZE);
  75         crypto_cipher_encrypt_one(tfm, pad, pad);
  76         gf_mulx(pad);
  77
  78         if (left || total_len == 0) {
  79                 for (i = 0; i < left; i++) {
  80                         cbc[i] ^= *pos++;
  81                         if (pos >= end) {
  82                                 e++;
  83                                 pos = addr[e];
  84                                 end = pos + len[e];
  85                         }
  86                 }
  87                 cbc[left] ^= 0x80;
  88                 gf_mulx(pad);
  89         }
  90
  91         for (i = 0; i < AES_BLOCK_SIZE; i++)
  92                 pad[i] ^= cbc[i];
  93         crypto_cipher_encrypt_one(tfm, pad, pad);
  94         memcpy(mac, pad, CMAC_TLEN);
  95 }
  96
  97
  98 void ieee80211_aes_cmac(struct crypto_cipher *tfm, const u8 *aad,
  99                         const u8 *data, size_t data_len, u8 *mic)
 100 {
 101         const u8 *addr[3];
 102         size_t len[3];
 103         u8 zero[CMAC_TLEN];
 104
 105         memset(zero, 0, CMAC_TLEN);
 106         addr[0] = aad;
 107         len[0] = AAD_LEN;
 108         addr[1] = data;
 109         len[1] = data_len - CMAC_TLEN;
 110         addr[2] = zero;
 111         len[2] = CMAC_TLEN;
 112
 113         aes_128_cmac_vector(tfm, 3, addr, len, mic);
 114 }
 115
 116
 117 struct crypto_cipher * ieee80211_aes_cmac_key_setup(const u8 key[])
 118 {
 119         struct crypto_cipher *tfm;
 120
 121         tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
 122         if (!IS_ERR(tfm))
 123                 crypto_cipher_setkey(tfm, key, AES_CMAC_KEY_LEN);
 124
 125         return tfm;
 126 }
 127
 128
 129 void ieee80211_aes_cmac_key_free(struct crypto_cipher *tfm)
 130 {
 131         crypto_free_cipher(tfm);
 132 }