net/mac80211/aes_cmac.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * AES-128-CMAC with TLen 16 for IEEE 802.11w BIP
   4  * Copyright 2008, Jouni Malinen <j@w1.fi>
   5  */
   6
   7 #include <linux/kernel.h>
   8 #include <linux/types.h>
   9 #include <linux/crypto.h>
  10 #include <linux/export.h>
  11 #include <linux/err.h>
  12 #include <crypto/aes.h>
  13
  14 #include <net/mac80211.h>
  15 #include "key.h"
  16 #include "aes_cmac.h"
  17
  18 #define CMAC_TLEN 8 /* CMAC TLen = 64 bits (8 octets) */
  19 #define CMAC_TLEN_256 16 /* CMAC TLen = 128 bits (16 octets) */
  20 #define AAD_LEN 20
  21
  22 static const u8 zero[CMAC_TLEN_256];
  23
  24 void ieee80211_aes_cmac(struct crypto_shash *tfm, const u8 *aad,
  25                         const u8 *data, size_t data_len, u8 *mic)
  26 {
  27         SHASH_DESC_ON_STACK(desc, tfm);
  28         u8 out[AES_BLOCK_SIZE];
  29         const __le16 *fc;
  30
  31         desc->tfm = tfm;
  32
  33         crypto_shash_init(desc);
  34         crypto_shash_update(desc, aad, AAD_LEN);
  35         fc = (const __le16 *)aad;
  36         if (ieee80211_is_beacon(*fc)) {
  37                 /* mask Timestamp field to zero */
  38                 crypto_shash_update(desc, zero, 8);
  39                 crypto_shash_update(desc, data + 8, data_len - 8 - CMAC_TLEN);
  40         } else {
  41                 crypto_shash_update(desc, data, data_len - CMAC_TLEN);
  42         }
  43         crypto_shash_finup(desc, zero, CMAC_TLEN, out);
  44
  45         memcpy(mic, out, CMAC_TLEN);
  46 }
  47
  48 void ieee80211_aes_cmac_256(struct crypto_shash *tfm, const u8 *aad,
  49                             const u8 *data, size_t data_len, u8 *mic)
  50 {
  51         SHASH_DESC_ON_STACK(desc, tfm);
  52         const __le16 *fc;
  53
  54         desc->tfm = tfm;
  55
  56         crypto_shash_init(desc);
  57         crypto_shash_update(desc, aad, AAD_LEN);
  58         fc = (const __le16 *)aad;
  59         if (ieee80211_is_beacon(*fc)) {
  60                 /* mask Timestamp field to zero */
  61                 crypto_shash_update(desc, zero, 8);
  62                 crypto_shash_update(desc, data + 8,
  63                                     data_len - 8 - CMAC_TLEN_256);
  64         } else {
  65                 crypto_shash_update(desc, data, data_len - CMAC_TLEN_256);
  66         }
  67         crypto_shash_finup(desc, zero, CMAC_TLEN_256, mic);
  68 }
  69
  70 struct crypto_shash *ieee80211_aes_cmac_key_setup(const u8 key[],
  71                                                   size_t key_len)
  72 {
  73         struct crypto_shash *tfm;
  74
  75         tfm = crypto_alloc_shash("cmac(aes)", 0, 0);
  76         if (!IS_ERR(tfm))
  77                 crypto_shash_setkey(tfm, key, key_len);
  78
  79         return tfm;
  80 }
  81
  82 void ieee80211_aes_cmac_key_free(struct crypto_shash *tfm)
  83 {
  84         crypto_free_shash(tfm);
  85 }