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mac80211: FILS AEAD protection for station mode association frames 

This adds support for encrypting (Re)Association Request frame and
decryption (Re)Association Response frame when using FILS in station
mode.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Jouni Malinen 2016-10-27 00:42:05 +03:00 committed by Johannes Berg
parent dbc0c2cb2f
commit 39404feee6
7 changed files with 403 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
net/mac80211/Makefile
View File

@ -19,6 +19,7 @@ mac80211-y := \
aes_gcm.o \
aes_cmac.o \
aes_gmac.o \
fils_aead.o \
cfg.o \
ethtool.o \
rx.o \

8
net/mac80211/aes_cmac.c
View File

@ -23,7 +23,7 @@
#define AAD_LEN 20
static void gf_mulx(u8 *pad)
void gf_mulx(u8 *pad)
{
int i, carry;
@ -35,9 +35,9 @@ static void gf_mulx(u8 *pad)
pad[AES_BLOCK_SIZE - 1] ^= 0x87;
}
static void aes_cmac_vector(struct crypto_cipher *tfm, size_t num_elem,
const u8 *addr[], const size_t *len, u8 *mac,
size_t mac_len)
void aes_cmac_vector(struct crypto_cipher *tfm, size_t num_elem,
const u8 *addr[], const size_t *len, u8 *mac,
size_t mac_len)
{
u8 cbc[AES_BLOCK_SIZE], pad[AES_BLOCK_SIZE];
const u8 *pos, *end;

4
net/mac80211/aes_cmac.h
View File

@ -11,6 +11,10 @@
#include <linux/crypto.h>
void gf_mulx(u8 *pad);
void aes_cmac_vector(struct crypto_cipher *tfm, size_t num_elem,
const u8 *addr[], const size_t *len, u8 *mac,
size_t mac_len);
struct crypto_cipher *ieee80211_aes_cmac_key_setup(const u8 key[],
size_t key_len);
void ieee80211_aes_cmac(struct crypto_cipher *tfm, const u8 *aad,

344
net/mac80211/fils_aead.c Normal file
View File

@ -0,0 +1,344 @@
/*
* 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) {
res = -ENOMEM;
goto fail;
}
/* 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;
}

19
net/mac80211/fils_aead.h Normal file
View File

@ -0,0 +1,19 @@
/*
* 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.
*/
#ifndef FILS_AEAD_H
#define FILS_AEAD_H
int fils_encrypt_assoc_req(struct sk_buff *skb,
struct ieee80211_mgd_assoc_data *assoc_data);
int fils_decrypt_assoc_resp(struct ieee80211_sub_if_data *sdata,
u8 *frame, size_t *frame_len,
struct ieee80211_mgd_assoc_data *assoc_data);
#endif /* FILS_AEAD_H */

4
net/mac80211/ieee80211_i.h
View File

@ -401,6 +401,10 @@ struct ieee80211_mgd_assoc_data {
struct ieee80211_vht_cap ap_vht_cap;
u8 fils_nonces[2 * FILS_NONCE_LEN];
u8 fils_kek[FILS_MAX_KEK_LEN];
size_t fils_kek_len;
size_t ie_len;
u8 ie[];
};

27
net/mac80211/mlme.c
View File

@ -30,6 +30,7 @@
#include "driver-ops.h"
#include "rate.h"
#include "led.h"
#include "fils_aead.h"
#define IEEE80211_AUTH_TIMEOUT (HZ / 5)
#define IEEE80211_AUTH_TIMEOUT_LONG (HZ / 2)
@ -652,6 +653,7 @@ static void ieee80211_send_assoc(struct ieee80211_sub_if_data *sdata)
2 + sizeof(struct ieee80211_ht_cap) + /* HT */
2 + sizeof(struct ieee80211_vht_cap) + /* VHT */
assoc_data->ie_len + /* extra IEs */
(assoc_data->fils_kek_len ? 16 /* AES-SIV */ : 0) +
9, /* WMM */
GFP_KERNEL);
if (!skb)
@ -875,6 +877,12 @@ static void ieee80211_send_assoc(struct ieee80211_sub_if_data *sdata)
memcpy(pos, assoc_data->ie + offset, noffset - offset);
}
if (assoc_data->fils_kek_len &&
fils_encrypt_assoc_req(skb, assoc_data) < 0) {
dev_kfree_skb(skb);
return;
}
drv_mgd_prepare_tx(local, sdata);
IEEE80211_SKB_CB(skb)->flags |= IEEE80211_TX_INTFL_DONT_ENCRYPT;
@ -3146,6 +3154,10 @@ static void ieee80211_rx_mgmt_assoc_resp(struct ieee80211_sub_if_data *sdata,
reassoc ? "Rea" : "A", mgmt->sa,
capab_info, status_code, (u16)(aid & ~(BIT(15) | BIT(14))));
if (assoc_data->fils_kek_len &&
fils_decrypt_assoc_resp(sdata, (u8 *)mgmt, &len, assoc_data) < 0)
return;
pos = mgmt->u.assoc_resp.variable;
ieee802_11_parse_elems(pos, len - (pos - (u8 *) mgmt), false, &elems);
@ -4707,6 +4719,21 @@ int ieee80211_mgd_assoc(struct ieee80211_sub_if_data *sdata,
assoc_data->ie_len = req->ie_len;
}
if (req->fils_kek) {
/* should already be checked in cfg80211 - so warn */
if (WARN_ON(req->fils_kek_len > FILS_MAX_KEK_LEN)) {
err = -EINVAL;
goto err_free;
}
memcpy(assoc_data->fils_kek, req->fils_kek,
req->fils_kek_len);
assoc_data->fils_kek_len = req->fils_kek_len;
}
if (req->fils_nonces)
memcpy(assoc_data->fils_nonces, req->fils_nonces,
2 * FILS_NONCE_LEN);
assoc_data->bss = req->bss;
if (ifmgd->req_smps == IEEE80211_SMPS_AUTOMATIC) {