summaryrefslogtreecommitdiffstats
path: root/net/mac80211/fils_aead.c
blob: a13ae148937ec6e17dfd59618d90ec4d7d45d96d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
// 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/algapi.h>
#include <crypto/hash.h>
#include <crypto/skcipher.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], *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, 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], *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;
}