// SPDX-License-Identifier: GPL-2.0-only
/*
* FILS AEAD for (Re)Association Request/Response frames
* Copyright 2016, Qualcomm Atheros, Inc.
*/
#include <crypto/aes.h>
#include <crypto/hash.h>
#include <crypto/skcipher.h>
#include <crypto/utils.h>
#include "ieee80211_i.h"
#include "aes_cmac.h"
#include "fils_aead.h"
static void gf_mulx(u8 *pad)
{
u64 a = get_unaligned_be64(pad);
u64 b = get_unaligned_be64(pad + 8);
put_unaligned_be64((a << 1) | (b >> 63), pad);
put_unaligned_be64((b << 1) ^ ((a >> 63) ? 0x87 : 0), pad + 8);
}
static int aes_s2v(struct crypto_shash *tfm,
size_t num_elem, const u8 *addr[], size_t len[], u8 *v)
{
u8 d[AES_BLOCK_SIZE], tmp[AES_BLOCK_SIZE] = {};
SHASH_DESC_ON_STACK(desc, tfm);
size_t i;
desc->tfm = tfm;
/* D = AES-CMAC(K, <zero>) */
crypto_shash_digest(desc, tmp, AES_BLOCK_SIZE, d);
for (i = 0; i < num_elem - 1; i++) {
/* D = dbl(D) xor AES_CMAC(K, Si) */
gf_mulx(d); /* dbl */
crypto_shash_digest(desc, addr[i], len[i], tmp);
crypto_xor(d, tmp, AES_BLOCK_SIZE);
}
crypto_shash_init(desc);
if (len[i] >= AES_BLOCK_SIZE) {
/* len(Sn) >= 128 */
/* T = Sn xorend D */
crypto_shash_update(desc, addr[i], len[i] - AES_BLOCK_SIZE);
crypto_xor(d, addr[i] + len[i] - AES_BLOCK_SIZE,
AES_BLOCK_SIZE);
} else {
/* len(Sn) < 128 */
/* T = dbl(D) xor pad(Sn) */
gf_mulx(d); /* dbl */
crypto_xor(d, addr[i], len[i]);
d[len[i]] ^= 0x80;
}
/* V = AES-CMAC(K, T) */
crypto_shash_finup(desc, d, AES_BLOCK_SIZE, v);
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_shash *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_shash("cmac(aes)", 0, 0);
if (IS_ERR(tfm))
return PTR_ERR(tfm);
/* K1 for S2V */
res = crypto_shash_setkey(tfm, key, key_len);
if (!res)
res = aes_s2v(tfm, num_elem, addr, len, v);
crypto_free_shash(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, CRYPTO_ALG_ASYNC);
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_shash *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, CRYPTO_ALG_ASYNC);
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_shash("cmac(aes)", 0, 0);
if (IS_ERR(tfm))
return PTR_ERR(tfm);
/* K1 for S2V */
res = crypto_shash_setkey(tfm, key, key_len);
if (!res)
res = aes_s2v(tfm, num_elem, addr, len, check);
crypto_free_shash(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];
const struct element *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_elem(WLAN_EID_EXT_FILS_SESSION,
ies, skb->data + skb->len - ies);
if (!session || session->datalen != 1 + 8)
return -EINVAL;
/* encrypt after FILS Session element */
encr = (u8 *)session->data + 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, 5, 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];
const struct element *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_elem(WLAN_EID_EXT_FILS_SESSION,
ies, frame + *frame_len - ies);
if (!session || session->datalen != 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->data + 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;
}
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