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 * Copyright (C) 2020 Intel Corporation
 6 */
 7
 8#include <linux/kernel.h>
 9#include <linux/types.h>
10#include <linux/crypto.h>
11#include <linux/export.h>
12#include <linux/err.h>
13#include <crypto/aes.h>
14
15#include <net/mac80211.h>
16#include "key.h"
17#include "aes_cmac.h"
18
19#define AAD_LEN 20
20
21static const u8 zero[IEEE80211_CMAC_256_MIC_LEN];
22
23int ieee80211_aes_cmac(struct crypto_shash *tfm, const u8 *aad,
24		       const u8 *data, size_t data_len, u8 *mic,
25		       unsigned int mic_len)
26{
27	int err;
28	SHASH_DESC_ON_STACK(desc, tfm);
29	u8 out[AES_BLOCK_SIZE];
30	const __le16 *fc;
31
32	desc->tfm = tfm;
33
34	err = crypto_shash_init(desc);
35	if (err)
36		return err;
37	err = crypto_shash_update(desc, aad, AAD_LEN);
38	if (err)
39		return err;
40	fc = (const __le16 *)aad;
41	if (ieee80211_is_beacon(*fc)) {
42		/* mask Timestamp field to zero */
43		err = crypto_shash_update(desc, zero, 8);
44		if (err)
45			return err;
46		err = crypto_shash_update(desc, data + 8,
47					  data_len - 8 - mic_len);
48		if (err)
49			return err;
50	} else {
51		err = crypto_shash_update(desc, data, data_len - mic_len);
52		if (err)
53			return err;
54	}
55	err = crypto_shash_finup(desc, zero, mic_len, out);
56	if (err)
57		return err;
58	memcpy(mic, out, mic_len);
59
60	return 0;
61}
62
63struct crypto_shash *ieee80211_aes_cmac_key_setup(const u8 key[],
64						  size_t key_len)
65{
66	struct crypto_shash *tfm;
67
68	tfm = crypto_alloc_shash("cmac(aes)", 0, 0);
69	if (!IS_ERR(tfm)) {
70		int err = crypto_shash_setkey(tfm, key, key_len);
71
72		if (err) {
73			crypto_free_shash(tfm);
74			return ERR_PTR(err);
75		}
76	}
77
78	return tfm;
79}
80
81void ieee80211_aes_cmac_key_free(struct crypto_shash *tfm)
82{
83	crypto_free_shash(tfm);
84}