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/export.h>
  14 #include <linux/err.h>
  15 #include <crypto/aes.h>
  16
  17 #include <net/mac80211.h>
  18 #include "key.h"
  19 #include "aes_cmac.h"
  20
  21 #define CMAC_TLEN 8 /* CMAC TLen = 64 bits (8 octets) */
  22 #define CMAC_TLEN_256 16 /* CMAC TLen = 128 bits (16 octets) */
  23 #define AAD_LEN 20
  24
  25
  26 static void gf_mulx(u8 *pad)
  27 {
  28         int i, carry;
  29
  30         carry = pad[0] & 0x80;
  31         for (i = 0; i < AES_BLOCK_SIZE - 1; i++)
  32                 pad[i] = (pad[i] << 1) | (pad[i + 1] >> 7);
  33         pad[AES_BLOCK_SIZE - 1] <<= 1;
  34         if (carry)
  35                 pad[AES_BLOCK_SIZE - 1] ^= 0x87;
  36 }
  37
  38 static void aes_cmac_vector(struct crypto_cipher *tfm, size_t num_elem,
  39                             const u8 *addr[], const size_t *len, u8 *mac,
  40                             size_t mac_len)
  41 {
  42         u8 cbc[AES_BLOCK_SIZE], pad[AES_BLOCK_SIZE];
  43         const u8 *pos, *end;
  44         size_t i, e, left, total_len;
  45
  46         memset(cbc, 0, AES_BLOCK_SIZE);
  47
  48         total_len = 0;
  49         for (e = 0; e < num_elem; e++)
  50                 total_len += len[e];
  51         left = total_len;
  52
  53         e = 0;
  54         pos = addr[0];
  55         end = pos + len[0];
  56
  57         while (left >= AES_BLOCK_SIZE) {
  58                 for (i = 0; i < AES_BLOCK_SIZE; i++) {
  59                         cbc[i] ^= *pos++;
  60                         if (pos >= end) {
  61                                 e++;
  62                                 pos = addr[e];
  63                                 end = pos + len[e];
  64                         }
  65                 }
  66                 if (left > AES_BLOCK_SIZE)
  67                         crypto_cipher_encrypt_one(tfm, cbc, cbc);
  68                 left -= AES_BLOCK_SIZE;
  69         }
  70
  71         memset(pad, 0, AES_BLOCK_SIZE);
  72         crypto_cipher_encrypt_one(tfm, pad, pad);
  73         gf_mulx(pad);
  74
  75         if (left || total_len == 0) {
  76                 for (i = 0; i < left; i++) {
  77                         cbc[i] ^= *pos++;
  78                         if (pos >= end) {
  79                                 e++;
  80                                 pos = addr[e];
  81                                 end = pos + len[e];
  82                         }
  83                 }
  84                 cbc[left] ^= 0x80;
  85                 gf_mulx(pad);
  86         }
  87
  88         for (i = 0; i < AES_BLOCK_SIZE; i++)
  89                 pad[i] ^= cbc[i];
  90         crypto_cipher_encrypt_one(tfm, pad, pad);
  91         memcpy(mac, pad, mac_len);
  92 }
  93
  94
  95 void ieee80211_aes_cmac(struct crypto_cipher *tfm, const u8 *aad,
  96                         const u8 *data, size_t data_len, u8 *mic)
  97 {
  98         const u8 *addr[3];
  99         size_t len[3];
 100         u8 zero[CMAC_TLEN];
 101
 102         memset(zero, 0, CMAC_TLEN);
 103         addr[0] = aad;
 104         len[0] = AAD_LEN;
 105         addr[1] = data;
 106         len[1] = data_len - CMAC_TLEN;
 107         addr[2] = zero;
 108         len[2] = CMAC_TLEN;
 109
 110         aes_cmac_vector(tfm, 3, addr, len, mic, CMAC_TLEN);
 111 }
 112
 113 void ieee80211_aes_cmac_256(struct crypto_cipher *tfm, const u8 *aad,
 114                             const u8 *data, size_t data_len, u8 *mic)
 115 {
 116         const u8 *addr[3];
 117         size_t len[3];
 118         u8 zero[CMAC_TLEN_256];
 119
 120         memset(zero, 0, CMAC_TLEN_256);
 121         addr[0] = aad;
 122         len[0] = AAD_LEN;
 123         addr[1] = data;
 124         len[1] = data_len - CMAC_TLEN_256;
 125         addr[2] = zero;
 126         len[2] = CMAC_TLEN_256;
 127
 128         aes_cmac_vector(tfm, 3, addr, len, mic, CMAC_TLEN_256);
 129 }
 130
 131 struct crypto_cipher *ieee80211_aes_cmac_key_setup(const u8 key[],
 132                                                    size_t key_len)
 133 {
 134         struct crypto_cipher *tfm;
 135
 136         tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
 137         if (!IS_ERR(tfm))
 138                 crypto_cipher_setkey(tfm, key, key_len);
 139
 140         return tfm;
 141 }
 142
 143
 144 void ieee80211_aes_cmac_key_free(struct crypto_cipher *tfm)
 145 {
 146         crypto_free_cipher(tfm);
 147 }