aes_gmac.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * AES-GMAC for IEEE 802.11 BIP-GMAC-128 and BIP-GMAC-256
 * Copyright 2015, Qualcomm Atheros, Inc.
 */

#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/err.h>
#include <crypto/aead.h>
#include <crypto/aes.h>

#include <net/mac80211.h>
#include "key.h"
#include "aes_gmac.h"

int ieee80211_aes_gmac(struct crypto_aead *tfm, const u8 *aad, u8 *nonce,
		       const u8 *data, size_t data_len, u8 *mic)
{
	struct scatterlist sg[5];
	u8 *zero, *__aad, iv[AES_BLOCK_SIZE];
	struct aead_request *aead_req;
	int reqsize = sizeof(*aead_req) + crypto_aead_reqsize(tfm);
	const __le16 *fc;
	int ret;

	if (data_len < IEEE80211_GMAC_MIC_LEN)
		return -EINVAL;

	aead_req = kzalloc(reqsize + IEEE80211_GMAC_MIC_LEN + GMAC_AAD_LEN,
			   GFP_ATOMIC);
	if (!aead_req)
		return -ENOMEM;

	zero = (u8 *)aead_req + reqsize;
	__aad = zero + IEEE80211_GMAC_MIC_LEN;
	memcpy(__aad, aad, GMAC_AAD_LEN);

	fc = (const __le16 *)aad;
	if (ieee80211_is_beacon(*fc)) {
		/* mask Timestamp field to zero */
		sg_init_table(sg, 5);
		sg_set_buf(&sg[0], __aad, GMAC_AAD_LEN);
		sg_set_buf(&sg[1], zero, 8);
		sg_set_buf(&sg[2], data + 8,
			   data_len - 8 - IEEE80211_GMAC_MIC_LEN);
		sg_set_buf(&sg[3], zero, IEEE80211_GMAC_MIC_LEN);
		sg_set_buf(&sg[4], mic, IEEE80211_GMAC_MIC_LEN);
	} else {
		sg_init_table(sg, 4);
		sg_set_buf(&sg[0], __aad, GMAC_AAD_LEN);
		sg_set_buf(&sg[1], data, data_len - IEEE80211_GMAC_MIC_LEN);
		sg_set_buf(&sg[2], zero, IEEE80211_GMAC_MIC_LEN);
		sg_set_buf(&sg[3], mic, IEEE80211_GMAC_MIC_LEN);
	}

	memcpy(iv, nonce, GMAC_NONCE_LEN);
	memset(iv + GMAC_NONCE_LEN, 0, sizeof(iv) - GMAC_NONCE_LEN);
	iv[AES_BLOCK_SIZE - 1] = 0x01;

	aead_request_set_tfm(aead_req, tfm);
	aead_request_set_crypt(aead_req, sg, sg, 0, iv);
	aead_request_set_ad(aead_req, GMAC_AAD_LEN + data_len);

	ret = crypto_aead_encrypt(aead_req);
	kfree_sensitive(aead_req);

	return ret;
}

struct crypto_aead *ieee80211_aes_gmac_key_setup(const u8 key[],
						 size_t key_len)
{
	struct crypto_aead *tfm;
	int err;

	tfm = crypto_alloc_aead("gcm(aes)", 0, CRYPTO_ALG_ASYNC);
	if (IS_ERR(tfm))
		return tfm;

	err = crypto_aead_setkey(tfm, key, key_len);
	if (!err)
		err = crypto_aead_setauthsize(tfm, IEEE80211_GMAC_MIC_LEN);
	if (!err)
		return tfm;

	crypto_free_aead(tfm);
	return ERR_PTR(err);
}

void ieee80211_aes_gmac_key_free(struct crypto_aead *tfm)
{
	crypto_free_aead(tfm);
}