linux/net/mac80211/aes_cmac.c
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   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
  25static 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
  38static 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 cbc[AES_BLOCK_SIZE], pad[AES_BLOCK_SIZE];
  42        const u8 *pos, *end;
  43        size_t i, e, left, total_len;
  44
  45        memset(cbc, 0, AES_BLOCK_SIZE);
  46
  47        total_len = 0;
  48        for (e = 0; e < num_elem; e++)
  49                total_len += len[e];
  50        left = total_len;
  51
  52        e = 0;
  53        pos = addr[0];
  54        end = pos + len[0];
  55
  56        while (left >= AES_BLOCK_SIZE) {
  57                for (i = 0; i < AES_BLOCK_SIZE; i++) {
  58                        cbc[i] ^= *pos++;
  59                        if (pos >= end) {
  60                                e++;
  61                                pos = addr[e];
  62                                end = pos + len[e];
  63                        }
  64                }
  65                if (left > AES_BLOCK_SIZE)
  66                        crypto_cipher_encrypt_one(tfm, cbc, cbc);
  67                left -= AES_BLOCK_SIZE;
  68        }
  69
  70        memset(pad, 0, AES_BLOCK_SIZE);
  71        crypto_cipher_encrypt_one(tfm, pad, pad);
  72        gf_mulx(pad);
  73
  74        if (left || total_len == 0) {
  75                for (i = 0; i < left; i++) {
  76                        cbc[i] ^= *pos++;
  77                        if (pos >= end) {
  78                                e++;
  79                                pos = addr[e];
  80                                end = pos + len[e];
  81                        }
  82                }
  83                cbc[left] ^= 0x80;
  84                gf_mulx(pad);
  85        }
  86
  87        for (i = 0; i < AES_BLOCK_SIZE; i++)
  88                pad[i] ^= cbc[i];
  89        crypto_cipher_encrypt_one(tfm, pad, pad);
  90        memcpy(mac, pad, CMAC_TLEN);
  91}
  92
  93
  94void ieee80211_aes_cmac(struct crypto_cipher *tfm, const u8 *aad,
  95                        const u8 *data, size_t data_len, u8 *mic)
  96{
  97        const u8 *addr[3];
  98        size_t len[3];
  99        u8 zero[CMAC_TLEN];
 100
 101        memset(zero, 0, CMAC_TLEN);
 102        addr[0] = aad;
 103        len[0] = AAD_LEN;
 104        addr[1] = data;
 105        len[1] = data_len - CMAC_TLEN;
 106        addr[2] = zero;
 107        len[2] = CMAC_TLEN;
 108
 109        aes_128_cmac_vector(tfm, 3, addr, len, mic);
 110}
 111
 112
 113struct crypto_cipher * ieee80211_aes_cmac_key_setup(const u8 key[])
 114{
 115        struct crypto_cipher *tfm;
 116
 117        tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
 118        if (!IS_ERR(tfm))
 119                crypto_cipher_setkey(tfm, key, AES_CMAC_KEY_LEN);
 120
 121        return tfm;
 122}
 123
 124
 125void ieee80211_aes_cmac_key_free(struct crypto_cipher *tfm)
 126{
 127        crypto_free_cipher(tfm);
 128}
 129
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