net/mac80211/fils_aead.c - linux - Git at Google

 /*
  * FILS AEAD for (Re)Association Request/Response frames
  * Copyright 2016, Qualcomm Atheros, Inc.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */

 #include <crypto/aes.h>
 #include <crypto/algapi.h>
 #include <crypto/skcipher.h>

 #include "ieee80211_i.h"
 #include "aes_cmac.h"
 #include "fils_aead.h"

 static int aes_s2v(struct crypto_cipher *tfm,
 		   size_t num_elem, const u8 *addr[], size_t len[], u8 *v)
 {
 	u8 d[AES_BLOCK_SIZE], tmp[AES_BLOCK_SIZE];
 	size_t i;
 	const u8 *data[2];
 	size_t data_len[2], data_elems;

 	/* D = AES-CMAC(K, <zero>) */
 	memset(tmp, 0, AES_BLOCK_SIZE);
 	data[0] = tmp;
 	data_len[0] = AES_BLOCK_SIZE;
 	aes_cmac_vector(tfm, 1, data, data_len, d, AES_BLOCK_SIZE);

 	for (i = 0; i < num_elem - 1; i++) {
 		/* D = dbl(D) xor AES_CMAC(K, Si) */
 		gf_mulx(d); /* dbl */
 		aes_cmac_vector(tfm, 1, &addr[i], &len[i], tmp,
 				AES_BLOCK_SIZE);
 		crypto_xor(d, tmp, AES_BLOCK_SIZE);
 	}

 	if (len[i] >= AES_BLOCK_SIZE) {
 		/* len(Sn) >= 128 */
 		size_t j;
 		const u8 *pos;

 		/* T = Sn xorend D */

 		/* Use a temporary buffer to perform xorend on Sn (addr[i]) to
 		 * avoid modifying the const input argument.
 		 */
 		data[0] = addr[i];
 		data_len[0] = len[i] - AES_BLOCK_SIZE;
 		pos = addr[i] + data_len[0];
 		for (j = 0; j < AES_BLOCK_SIZE; j++)
 			tmp[j] = pos[j] ^ d[j];
 		data[1] = tmp;
 		data_len[1] = AES_BLOCK_SIZE;
 		data_elems = 2;
 	} else {
 		/* len(Sn) < 128 */
 		/* T = dbl(D) xor pad(Sn) */
 		gf_mulx(d); /* dbl */
 		memset(tmp, 0, AES_BLOCK_SIZE);
 		memcpy(tmp, addr[i], len[i]);
 		tmp[len[i]] = 0x80;
 		crypto_xor(d, tmp, AES_BLOCK_SIZE);
 		data[0] = d;
 		data_len[0] = sizeof(d);
 		data_elems = 1;
 	}
 	/* V = AES-CMAC(K, T) */
 	aes_cmac_vector(tfm, data_elems, data, data_len, v, AES_BLOCK_SIZE);

 	return 0;
 }

 /* Note: addr[] and len[] needs to have one extra slot at the end. */
 static int aes_siv_encrypt(const u8 *key, size_t key_len,
 			   const u8 *plain, size_t plain_len,
 			   size_t num_elem, const u8 *addr[],
 			   size_t len[], u8 *out)
 {
 	u8 v[AES_BLOCK_SIZE];
 	struct crypto_cipher *tfm;
 	struct crypto_skcipher *tfm2;
 	struct skcipher_request *req;
 	int res;
 	struct scatterlist src[1], dst[1];
 	u8 *tmp;

 	key_len /= 2; /* S2V key || CTR key */

 	addr[num_elem] = plain;
 	len[num_elem] = plain_len;
 	num_elem++;

 	/* S2V */

 	tfm = crypto_alloc_cipher("aes", 0, 0);
 	if (IS_ERR(tfm))
 		return PTR_ERR(tfm);
 	/* K1 for S2V */
 	res = crypto_cipher_setkey(tfm, key, key_len);
 	if (!res)
 		res = aes_s2v(tfm, num_elem, addr, len, v);
 	crypto_free_cipher(tfm);
 	if (res)
 		return res;

 	/* Use a temporary buffer of the plaintext to handle need for
 	 * overwriting this during AES-CTR.
 	 */
 	tmp = kmemdup(plain, plain_len, GFP_KERNEL);
 	if (!tmp)
 		return -ENOMEM;

 	/* IV for CTR before encrypted data */
 	memcpy(out, v, AES_BLOCK_SIZE);

 	/* Synthetic IV to be used as the initial counter in CTR:
 	 * Q = V bitand (1^64 || 0^1 || 1^31 || 0^1 || 1^31)
 	 */
 	v[8] &= 0x7f;
 	v[12] &= 0x7f;

 	/* CTR */

 	tfm2 = crypto_alloc_skcipher("ctr(aes)", 0, 0);
 	if (IS_ERR(tfm2)) {
 		kfree(tmp);
 		return PTR_ERR(tfm2);
 	}
 	/* K2 for CTR */
 	res = crypto_skcipher_setkey(tfm2, key + key_len, key_len);
 	if (res)
 		goto fail;

 	req = skcipher_request_alloc(tfm2, GFP_KERNEL);
 	if (!req) {
 		res = -ENOMEM;
 		goto fail;
 	}

 	sg_init_one(src, tmp, plain_len);
 	sg_init_one(dst, out + AES_BLOCK_SIZE, plain_len);
 	skcipher_request_set_crypt(req, src, dst, plain_len, v);
 	res = crypto_skcipher_encrypt(req);
 	skcipher_request_free(req);
 fail:
 	kfree(tmp);
 	crypto_free_skcipher(tfm2);
 	return res;
 }

 /* Note: addr[] and len[] needs to have one extra slot at the end. */
 static int aes_siv_decrypt(const u8 *key, size_t key_len,
 			   const u8 *iv_crypt, size_t iv_c_len,
 			   size_t num_elem, const u8 *addr[], size_t len[],
 			   u8 *out)
 {
 	struct crypto_cipher *tfm;
 	struct crypto_skcipher *tfm2;
 	struct skcipher_request *req;
 	struct scatterlist src[1], dst[1];
 	size_t crypt_len;
 	int res;
 	u8 frame_iv[AES_BLOCK_SIZE], iv[AES_BLOCK_SIZE];
 	u8 check[AES_BLOCK_SIZE];

 	crypt_len = iv_c_len - AES_BLOCK_SIZE;
 	key_len /= 2; /* S2V key || CTR key */
 	addr[num_elem] = out;
 	len[num_elem] = crypt_len;
 	num_elem++;

 	memcpy(iv, iv_crypt, AES_BLOCK_SIZE);
 	memcpy(frame_iv, iv_crypt, AES_BLOCK_SIZE);

 	/* Synthetic IV to be used as the initial counter in CTR:
 	 * Q = V bitand (1^64 || 0^1 || 1^31 || 0^1 || 1^31)
 	 */
 	iv[8] &= 0x7f;
 	iv[12] &= 0x7f;

 	/* CTR */

 	tfm2 = crypto_alloc_skcipher("ctr(aes)", 0, 0);
 	if (IS_ERR(tfm2))
 		return PTR_ERR(tfm2);
 	/* K2 for CTR */
 	res = crypto_skcipher_setkey(tfm2, key + key_len, key_len);
 	if (res) {
 		crypto_free_skcipher(tfm2);
 		return res;
 	}

 	req = skcipher_request_alloc(tfm2, GFP_KERNEL);
 	if (!req) {
 		crypto_free_skcipher(tfm2);
 		return -ENOMEM;
 	}

 	sg_init_one(src, iv_crypt + AES_BLOCK_SIZE, crypt_len);
 	sg_init_one(dst, out, crypt_len);
 	skcipher_request_set_crypt(req, src, dst, crypt_len, iv);
 	res = crypto_skcipher_decrypt(req);
 	skcipher_request_free(req);
 	crypto_free_skcipher(tfm2);
 	if (res)
 		return res;

 	/* S2V */

 	tfm = crypto_alloc_cipher("aes", 0, 0);
 	if (IS_ERR(tfm))
 		return PTR_ERR(tfm);
 	/* K1 for S2V */
 	res = crypto_cipher_setkey(tfm, key, key_len);
 	if (!res)
 		res = aes_s2v(tfm, num_elem, addr, len, check);
 	crypto_free_cipher(tfm);
 	if (res)
 		return res;
 	if (memcmp(check, frame_iv, AES_BLOCK_SIZE) != 0)
 		return -EINVAL;
 	return 0;
 }

 int fils_encrypt_assoc_req(struct sk_buff *skb,
 			   struct ieee80211_mgd_assoc_data *assoc_data)
 {
 	struct ieee80211_mgmt *mgmt = (void *)skb->data;
 	u8 *capab, *ies, *encr;
 	const u8 *addr[5 + 1], *session;
 	size_t len[5 + 1];
 	size_t crypt_len;

 	if (ieee80211_is_reassoc_req(mgmt->frame_control)) {
 		capab = (u8 *)&mgmt->u.reassoc_req.capab_info;
 		ies = mgmt->u.reassoc_req.variable;
 	} else {
 		capab = (u8 *)&mgmt->u.assoc_req.capab_info;
 		ies = mgmt->u.assoc_req.variable;
 	}

 	session = cfg80211_find_ext_ie(WLAN_EID_EXT_FILS_SESSION,
 				       ies, skb->data + skb->len - ies);
 	if (!session || session[1] != 1 + 8)
 		return -EINVAL;
 	/* encrypt after FILS Session element */
 	encr = (u8 *)session + 2 + 1 + 8;

 	/* AES-SIV AAD vectors */

 	/* The STA's MAC address */
 	addr[0] = mgmt->sa;
 	len[0] = ETH_ALEN;
 	/* The AP's BSSID */
 	addr[1] = mgmt->da;
 	len[1] = ETH_ALEN;
 	/* The STA's nonce */
 	addr[2] = assoc_data->fils_nonces;
 	len[2] = FILS_NONCE_LEN;
 	/* The AP's nonce */
 	addr[3] = &assoc_data->fils_nonces[FILS_NONCE_LEN];
 	len[3] = FILS_NONCE_LEN;
 	/* The (Re)Association Request frame from the Capability Information
 	 * field to the FILS Session element (both inclusive).
 	 */
 	addr[4] = capab;
 	len[4] = encr - capab;

 	crypt_len = skb->data + skb->len - encr;
 	skb_put(skb, AES_BLOCK_SIZE);
 	return aes_siv_encrypt(assoc_data->fils_kek, assoc_data->fils_kek_len,
 			       encr, crypt_len, 1, addr, len, encr);
 }

 int fils_decrypt_assoc_resp(struct ieee80211_sub_if_data *sdata,
 			    u8 *frame, size_t *frame_len,
 			    struct ieee80211_mgd_assoc_data *assoc_data)
 {
 	struct ieee80211_mgmt *mgmt = (void *)frame;
 	u8 *capab, *ies, *encr;
 	const u8 *addr[5 + 1], *session;
 	size_t len[5 + 1];
 	int res;
 	size_t crypt_len;

 	if (*frame_len < 24 + 6)
 		return -EINVAL;

 	capab = (u8 *)&mgmt->u.assoc_resp.capab_info;
 	ies = mgmt->u.assoc_resp.variable;
 	session = cfg80211_find_ext_ie(WLAN_EID_EXT_FILS_SESSION,
 				       ies, frame + *frame_len - ies);
 	if (!session || session[1] != 1 + 8) {
 		mlme_dbg(sdata,
 			 "No (valid) FILS Session element in (Re)Association Response frame from %pM",
 			 mgmt->sa);
 		return -EINVAL;
 	}
 	/* decrypt after FILS Session element */
 	encr = (u8 *)session + 2 + 1 + 8;

 	/* AES-SIV AAD vectors */

 	/* The AP's BSSID */
 	addr[0] = mgmt->sa;
 	len[0] = ETH_ALEN;
 	/* The STA's MAC address */
 	addr[1] = mgmt->da;
 	len[1] = ETH_ALEN;
 	/* The AP's nonce */
 	addr[2] = &assoc_data->fils_nonces[FILS_NONCE_LEN];
 	len[2] = FILS_NONCE_LEN;
 	/* The STA's nonce */
 	addr[3] = assoc_data->fils_nonces;
 	len[3] = FILS_NONCE_LEN;
 	/* The (Re)Association Response frame from the Capability Information
 	 * field to the FILS Session element (both inclusive).
 	 */
 	addr[4] = capab;
 	len[4] = encr - capab;

 	crypt_len = frame + *frame_len - encr;
 	if (crypt_len < AES_BLOCK_SIZE) {
 		mlme_dbg(sdata,
 			 "Not enough room for AES-SIV data after FILS Session element in (Re)Association Response frame from %pM",
 			 mgmt->sa);
 		return -EINVAL;
 	}
 	res = aes_siv_decrypt(assoc_data->fils_kek, assoc_data->fils_kek_len,
 			      encr, crypt_len, 5, addr, len, encr);
 	if (res != 0) {
 		mlme_dbg(sdata,
 			 "AES-SIV decryption of (Re)Association Response frame from %pM failed",
 			 mgmt->sa);
 		return res;
 	}
 	*frame_len -= AES_BLOCK_SIZE;
 	return 0;
 }
	/*
	* FILS AEAD for (Re)Association Request/Response frames
	* Copyright 2016, Qualcomm Atheros, Inc.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/

	#include <crypto/aes.h>
	#include <crypto/algapi.h>
	#include <crypto/skcipher.h>

	#include "ieee80211_i.h"
	#include "aes_cmac.h"
	#include "fils_aead.h"

	static int aes_s2v(struct crypto_cipher *tfm,
	size_t num_elem, const u8 addr[], size_t len[], u8 v)
	{
	u8 d[AES_BLOCK_SIZE], tmp[AES_BLOCK_SIZE];
	size_t i;
	const u8 *data[2];
	size_t data_len[2], data_elems;

	/* D = AES-CMAC(K, <zero>) */
	memset(tmp, 0, AES_BLOCK_SIZE);
	data[0] = tmp;
	data_len[0] = AES_BLOCK_SIZE;
	aes_cmac_vector(tfm, 1, data, data_len, d, AES_BLOCK_SIZE);

	for (i = 0; i < num_elem - 1; i++) {
	/* D = dbl(D) xor AES_CMAC(K, Si) */
	gf_mulx(d); /* dbl */
	aes_cmac_vector(tfm, 1, &addr[i], &len[i], tmp,
	AES_BLOCK_SIZE);
	crypto_xor(d, tmp, AES_BLOCK_SIZE);
	}

	if (len[i] >= AES_BLOCK_SIZE) {
	/* len(Sn) >= 128 */
	size_t j;
	const u8 *pos;

	/* T = Sn xorend D */

	/* Use a temporary buffer to perform xorend on Sn (addr[i]) to
	* avoid modifying the const input argument.
	*/
	data[0] = addr[i];
	data_len[0] = len[i] - AES_BLOCK_SIZE;
	pos = addr[i] + data_len[0];
	for (j = 0; j < AES_BLOCK_SIZE; j++)
	tmp[j] = pos[j] ^ d[j];
	data[1] = tmp;
	data_len[1] = AES_BLOCK_SIZE;
	data_elems = 2;
	} else {
	/* len(Sn) < 128 */
	/* T = dbl(D) xor pad(Sn) */
	gf_mulx(d); /* dbl */
	memset(tmp, 0, AES_BLOCK_SIZE);
	memcpy(tmp, addr[i], len[i]);
	tmp[len[i]] = 0x80;
	crypto_xor(d, tmp, AES_BLOCK_SIZE);
	data[0] = d;
	data_len[0] = sizeof(d);
	data_elems = 1;
	}
	/* V = AES-CMAC(K, T) */
	aes_cmac_vector(tfm, data_elems, data, data_len, v, AES_BLOCK_SIZE);

	return 0;
	}

	/* Note: addr[] and len[] needs to have one extra slot at the end. */
	static int aes_siv_encrypt(const u8 *key, size_t key_len,
	const u8 *plain, size_t plain_len,
	size_t num_elem, const u8 *addr[],
	size_t len[], u8 *out)
	{
	u8 v[AES_BLOCK_SIZE];
	struct crypto_cipher *tfm;
	struct crypto_skcipher *tfm2;
	struct skcipher_request *req;
	int res;
	struct scatterlist src[1], dst[1];
	u8 *tmp;

	key_len /= 2; /* S2V key \|\| CTR key */

	addr[num_elem] = plain;
	len[num_elem] = plain_len;
	num_elem++;

	/* S2V */

	tfm = crypto_alloc_cipher("aes", 0, 0);
	if (IS_ERR(tfm))
	return PTR_ERR(tfm);
	/* K1 for S2V */
	res = crypto_cipher_setkey(tfm, key, key_len);
	if (!res)
	res = aes_s2v(tfm, num_elem, addr, len, v);
	crypto_free_cipher(tfm);
	if (res)
	return res;

	/* Use a temporary buffer of the plaintext to handle need for
	* overwriting this during AES-CTR.
	*/
	tmp = kmemdup(plain, plain_len, GFP_KERNEL);
	if (!tmp)
	return -ENOMEM;

	/* IV for CTR before encrypted data */
	memcpy(out, v, AES_BLOCK_SIZE);

	/* Synthetic IV to be used as the initial counter in CTR:
	* Q = V bitand (1^64 \|\| 0^1 \|\| 1^31 \|\| 0^1 \|\| 1^31)
	*/
	v[8] &= 0x7f;
	v[12] &= 0x7f;

	/* CTR */

	tfm2 = crypto_alloc_skcipher("ctr(aes)", 0, 0);
	if (IS_ERR(tfm2)) {
	kfree(tmp);
	return PTR_ERR(tfm2);
	}
	/* K2 for CTR */
	res = crypto_skcipher_setkey(tfm2, key + key_len, key_len);
	if (res)
	goto fail;

	req = skcipher_request_alloc(tfm2, GFP_KERNEL);
	if (!req) {
	res = -ENOMEM;
	goto fail;
	}

	sg_init_one(src, tmp, plain_len);
	sg_init_one(dst, out + AES_BLOCK_SIZE, plain_len);
	skcipher_request_set_crypt(req, src, dst, plain_len, v);
	res = crypto_skcipher_encrypt(req);
	skcipher_request_free(req);
	fail:
	kfree(tmp);
	crypto_free_skcipher(tfm2);
	return res;
	}

	/* Note: addr[] and len[] needs to have one extra slot at the end. */
	static int aes_siv_decrypt(const u8 *key, size_t key_len,
	const u8 *iv_crypt, size_t iv_c_len,
	size_t num_elem, const u8 *addr[], size_t len[],
	u8 *out)
	{
	struct crypto_cipher *tfm;
	struct crypto_skcipher *tfm2;
	struct skcipher_request *req;
	struct scatterlist src[1], dst[1];
	size_t crypt_len;
	int res;
	u8 frame_iv[AES_BLOCK_SIZE], iv[AES_BLOCK_SIZE];
	u8 check[AES_BLOCK_SIZE];

	crypt_len = iv_c_len - AES_BLOCK_SIZE;
	key_len /= 2; /* S2V key \|\| CTR key */
	addr[num_elem] = out;
	len[num_elem] = crypt_len;
	num_elem++;

	memcpy(iv, iv_crypt, AES_BLOCK_SIZE);
	memcpy(frame_iv, iv_crypt, AES_BLOCK_SIZE);

	/* Synthetic IV to be used as the initial counter in CTR:
	* Q = V bitand (1^64 \|\| 0^1 \|\| 1^31 \|\| 0^1 \|\| 1^31)
	*/
	iv[8] &= 0x7f;
	iv[12] &= 0x7f;

	/* CTR */

	tfm2 = crypto_alloc_skcipher("ctr(aes)", 0, 0);
	if (IS_ERR(tfm2))
	return PTR_ERR(tfm2);
	/* K2 for CTR */
	res = crypto_skcipher_setkey(tfm2, key + key_len, key_len);
	if (res) {
	crypto_free_skcipher(tfm2);
	return res;
	}

	req = skcipher_request_alloc(tfm2, GFP_KERNEL);
	if (!req) {
	crypto_free_skcipher(tfm2);
	return -ENOMEM;
	}

	sg_init_one(src, iv_crypt + AES_BLOCK_SIZE, crypt_len);
	sg_init_one(dst, out, crypt_len);
	skcipher_request_set_crypt(req, src, dst, crypt_len, iv);
	res = crypto_skcipher_decrypt(req);
	skcipher_request_free(req);
	crypto_free_skcipher(tfm2);
	if (res)
	return res;

	/* S2V */

	tfm = crypto_alloc_cipher("aes", 0, 0);
	if (IS_ERR(tfm))
	return PTR_ERR(tfm);
	/* K1 for S2V */
	res = crypto_cipher_setkey(tfm, key, key_len);
	if (!res)
	res = aes_s2v(tfm, num_elem, addr, len, check);
	crypto_free_cipher(tfm);
	if (res)
	return res;
	if (memcmp(check, frame_iv, AES_BLOCK_SIZE) != 0)
	return -EINVAL;
	return 0;
	}

	int fils_encrypt_assoc_req(struct sk_buff *skb,
	struct ieee80211_mgd_assoc_data *assoc_data)
	{
	struct ieee80211_mgmt mgmt = (void )skb->data;
	u8 capab, ies, *encr;
	const u8 addr[5 + 1], session;
	size_t len[5 + 1];
	size_t crypt_len;

	if (ieee80211_is_reassoc_req(mgmt->frame_control)) {
	capab = (u8 *)&mgmt->u.reassoc_req.capab_info;
	ies = mgmt->u.reassoc_req.variable;
	} else {
	capab = (u8 *)&mgmt->u.assoc_req.capab_info;
	ies = mgmt->u.assoc_req.variable;
	}

	session = cfg80211_find_ext_ie(WLAN_EID_EXT_FILS_SESSION,
	ies, skb->data + skb->len - ies);
	if (!session \|\| session[1] != 1 + 8)
	return -EINVAL;
	/* encrypt after FILS Session element */
	encr = (u8 *)session + 2 + 1 + 8;

	/* AES-SIV AAD vectors */

	/* The STA's MAC address */
	addr[0] = mgmt->sa;
	len[0] = ETH_ALEN;
	/* The AP's BSSID */
	addr[1] = mgmt->da;
	len[1] = ETH_ALEN;
	/* The STA's nonce */
	addr[2] = assoc_data->fils_nonces;
	len[2] = FILS_NONCE_LEN;
	/* The AP's nonce */
	addr[3] = &assoc_data->fils_nonces[FILS_NONCE_LEN];
	len[3] = FILS_NONCE_LEN;
	/* The (Re)Association Request frame from the Capability Information
	* field to the FILS Session element (both inclusive).
	*/
	addr[4] = capab;
	len[4] = encr - capab;

	crypt_len = skb->data + skb->len - encr;
	skb_put(skb, AES_BLOCK_SIZE);
	return aes_siv_encrypt(assoc_data->fils_kek, assoc_data->fils_kek_len,
	encr, crypt_len, 1, addr, len, encr);
	}

	int fils_decrypt_assoc_resp(struct ieee80211_sub_if_data *sdata,
	u8 frame, size_t frame_len,
	struct ieee80211_mgd_assoc_data *assoc_data)
	{
	struct ieee80211_mgmt mgmt = (void )frame;
	u8 capab, ies, *encr;
	const u8 addr[5 + 1], session;
	size_t len[5 + 1];
	int res;
	size_t crypt_len;

	if (*frame_len < 24 + 6)
	return -EINVAL;

	capab = (u8 *)&mgmt->u.assoc_resp.capab_info;
	ies = mgmt->u.assoc_resp.variable;
	session = cfg80211_find_ext_ie(WLAN_EID_EXT_FILS_SESSION,
	ies, frame + *frame_len - ies);
	if (!session \|\| session[1] != 1 + 8) {
	mlme_dbg(sdata,
	"No (valid) FILS Session element in (Re)Association Response frame from %pM",
	mgmt->sa);
	return -EINVAL;
	}
	/* decrypt after FILS Session element */
	encr = (u8 *)session + 2 + 1 + 8;

	/* AES-SIV AAD vectors */

	/* The AP's BSSID */
	addr[0] = mgmt->sa;
	len[0] = ETH_ALEN;
	/* The STA's MAC address */
	addr[1] = mgmt->da;
	len[1] = ETH_ALEN;
	/* The AP's nonce */
	addr[2] = &assoc_data->fils_nonces[FILS_NONCE_LEN];
	len[2] = FILS_NONCE_LEN;
	/* The STA's nonce */
	addr[3] = assoc_data->fils_nonces;
	len[3] = FILS_NONCE_LEN;
	/* The (Re)Association Response frame from the Capability Information
	* field to the FILS Session element (both inclusive).
	*/
	addr[4] = capab;
	len[4] = encr - capab;

	crypt_len = frame + *frame_len - encr;
	if (crypt_len < AES_BLOCK_SIZE) {
	mlme_dbg(sdata,
	"Not enough room for AES-SIV data after FILS Session element in (Re)Association Response frame from %pM",
	mgmt->sa);
	return -EINVAL;
	}
	res = aes_siv_decrypt(assoc_data->fils_kek, assoc_data->fils_kek_len,
	encr, crypt_len, 5, addr, len, encr);
	if (res != 0) {
	mlme_dbg(sdata,
	"AES-SIV decryption of (Re)Association Response frame from %pM failed",
	mgmt->sa);
	return res;
	}
	*frame_len -= AES_BLOCK_SIZE;
	return 0;
	}