1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * lib80211 crypt: host-based CCMP encryption implementation for lib80211
4  *
5  * Copyright (c) 2003-2004, Jouni Malinen <j@w1.fi>
6  * Copyright (c) 2008, John W. Linville <linville@tuxdriver.com>
7  */
8 
9 #include <linux/kernel.h>
10 #include <linux/err.h>
11 #include <linux/module.h>
12 #include <linux/init.h>
13 #include <linux/slab.h>
14 #include <linux/random.h>
15 #include <linux/skbuff.h>
16 #include <linux/netdevice.h>
17 #include <linux/if_ether.h>
18 #include <linux/if_arp.h>
19 #include <asm/string.h>
20 #include <linux/wireless.h>
21 
22 #include <linux/ieee80211.h>
23 
24 #include <linux/crypto.h>
25 #include <crypto/aead.h>
26 
27 #include <net/lib80211.h>
28 
29 MODULE_AUTHOR("Jouni Malinen");
30 MODULE_DESCRIPTION("Host AP crypt: CCMP");
31 MODULE_LICENSE("GPL");
32 
33 #define AES_BLOCK_LEN 16
34 #define CCMP_HDR_LEN 8
35 #define CCMP_MIC_LEN 8
36 #define CCMP_TK_LEN 16
37 #define CCMP_PN_LEN 6
38 
39 struct lib80211_ccmp_data {
40 	u8 key[CCMP_TK_LEN];
41 	int key_set;
42 
43 	u8 tx_pn[CCMP_PN_LEN];
44 	u8 rx_pn[CCMP_PN_LEN];
45 
46 	u32 dot11RSNAStatsCCMPFormatErrors;
47 	u32 dot11RSNAStatsCCMPReplays;
48 	u32 dot11RSNAStatsCCMPDecryptErrors;
49 
50 	int key_idx;
51 
52 	struct crypto_aead *tfm;
53 
54 	/* scratch buffers for virt_to_page() (crypto API) */
55 	u8 tx_aad[2 * AES_BLOCK_LEN];
56 	u8 rx_aad[2 * AES_BLOCK_LEN];
57 };
58 
59 static void *lib80211_ccmp_init(int key_idx)
60 {
61 	struct lib80211_ccmp_data *priv;
62 
63 	priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
64 	if (priv == NULL)
65 		goto fail;
66 	priv->key_idx = key_idx;
67 
68 	priv->tfm = crypto_alloc_aead("ccm(aes)", 0, CRYPTO_ALG_ASYNC);
69 	if (IS_ERR(priv->tfm)) {
70 		priv->tfm = NULL;
71 		goto fail;
72 	}
73 
74 	return priv;
75 
76       fail:
77 	if (priv) {
78 		if (priv->tfm)
79 			crypto_free_aead(priv->tfm);
80 		kfree(priv);
81 	}
82 
83 	return NULL;
84 }
85 
86 static void lib80211_ccmp_deinit(void *priv)
87 {
88 	struct lib80211_ccmp_data *_priv = priv;
89 	if (_priv && _priv->tfm)
90 		crypto_free_aead(_priv->tfm);
91 	kfree(priv);
92 }
93 
94 static int ccmp_init_iv_and_aad(const struct ieee80211_hdr *hdr,
95 				const u8 *pn, u8 *iv, u8 *aad)
96 {
97 	u8 *pos, qc = 0;
98 	size_t aad_len;
99 	int a4_included, qc_included;
100 
101 	a4_included = ieee80211_has_a4(hdr->frame_control);
102 	qc_included = ieee80211_is_data_qos(hdr->frame_control);
103 
104 	aad_len = 22;
105 	if (a4_included)
106 		aad_len += 6;
107 	if (qc_included) {
108 		pos = (u8 *) & hdr->addr4;
109 		if (a4_included)
110 			pos += 6;
111 		qc = *pos & 0x0f;
112 		aad_len += 2;
113 	}
114 
115 	/* In CCM, the initial vectors (IV) used for CTR mode encryption and CBC
116 	 * mode authentication are not allowed to collide, yet both are derived
117 	 * from the same vector. We only set L := 1 here to indicate that the
118 	 * data size can be represented in (L+1) bytes. The CCM layer will take
119 	 * care of storing the data length in the top (L+1) bytes and setting
120 	 * and clearing the other bits as is required to derive the two IVs.
121 	 */
122 	iv[0] = 0x1;
123 
124 	/* Nonce: QC | A2 | PN */
125 	iv[1] = qc;
126 	memcpy(iv + 2, hdr->addr2, ETH_ALEN);
127 	memcpy(iv + 8, pn, CCMP_PN_LEN);
128 
129 	/* AAD:
130 	 * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
131 	 * A1 | A2 | A3
132 	 * SC with bits 4..15 (seq#) masked to zero
133 	 * A4 (if present)
134 	 * QC (if present)
135 	 */
136 	pos = (u8 *) hdr;
137 	aad[0] = pos[0] & 0x8f;
138 	aad[1] = pos[1] & 0xc7;
139 	memcpy(aad + 2, hdr->addr1, 3 * ETH_ALEN);
140 	pos = (u8 *) & hdr->seq_ctrl;
141 	aad[20] = pos[0] & 0x0f;
142 	aad[21] = 0;		/* all bits masked */
143 	memset(aad + 22, 0, 8);
144 	if (a4_included)
145 		memcpy(aad + 22, hdr->addr4, ETH_ALEN);
146 	if (qc_included) {
147 		aad[a4_included ? 28 : 22] = qc;
148 		/* rest of QC masked */
149 	}
150 	return aad_len;
151 }
152 
153 static int lib80211_ccmp_hdr(struct sk_buff *skb, int hdr_len,
154 			      u8 *aeskey, int keylen, void *priv)
155 {
156 	struct lib80211_ccmp_data *key = priv;
157 	int i;
158 	u8 *pos;
159 
160 	if (skb_headroom(skb) < CCMP_HDR_LEN || skb->len < hdr_len)
161 		return -1;
162 
163 	if (aeskey != NULL && keylen >= CCMP_TK_LEN)
164 		memcpy(aeskey, key->key, CCMP_TK_LEN);
165 
166 	pos = skb_push(skb, CCMP_HDR_LEN);
167 	memmove(pos, pos + CCMP_HDR_LEN, hdr_len);
168 	pos += hdr_len;
169 
170 	i = CCMP_PN_LEN - 1;
171 	while (i >= 0) {
172 		key->tx_pn[i]++;
173 		if (key->tx_pn[i] != 0)
174 			break;
175 		i--;
176 	}
177 
178 	*pos++ = key->tx_pn[5];
179 	*pos++ = key->tx_pn[4];
180 	*pos++ = 0;
181 	*pos++ = (key->key_idx << 6) | (1 << 5) /* Ext IV included */ ;
182 	*pos++ = key->tx_pn[3];
183 	*pos++ = key->tx_pn[2];
184 	*pos++ = key->tx_pn[1];
185 	*pos++ = key->tx_pn[0];
186 
187 	return CCMP_HDR_LEN;
188 }
189 
190 static int lib80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
191 {
192 	struct lib80211_ccmp_data *key = priv;
193 	struct ieee80211_hdr *hdr;
194 	struct aead_request *req;
195 	struct scatterlist sg[2];
196 	u8 *aad = key->tx_aad;
197 	u8 iv[AES_BLOCK_LEN];
198 	int len, data_len, aad_len;
199 	int ret;
200 
201 	if (skb_tailroom(skb) < CCMP_MIC_LEN || skb->len < hdr_len)
202 		return -1;
203 
204 	data_len = skb->len - hdr_len;
205 	len = lib80211_ccmp_hdr(skb, hdr_len, NULL, 0, priv);
206 	if (len < 0)
207 		return -1;
208 
209 	req = aead_request_alloc(key->tfm, GFP_ATOMIC);
210 	if (!req)
211 		return -ENOMEM;
212 
213 	hdr = (struct ieee80211_hdr *)skb->data;
214 	aad_len = ccmp_init_iv_and_aad(hdr, key->tx_pn, iv, aad);
215 
216 	skb_put(skb, CCMP_MIC_LEN);
217 
218 	sg_init_table(sg, 2);
219 	sg_set_buf(&sg[0], aad, aad_len);
220 	sg_set_buf(&sg[1], skb->data + hdr_len + CCMP_HDR_LEN,
221 		   data_len + CCMP_MIC_LEN);
222 
223 	aead_request_set_callback(req, 0, NULL, NULL);
224 	aead_request_set_ad(req, aad_len);
225 	aead_request_set_crypt(req, sg, sg, data_len, iv);
226 
227 	ret = crypto_aead_encrypt(req);
228 	aead_request_free(req);
229 
230 	return ret;
231 }
232 
233 /*
234  * deal with seq counter wrapping correctly.
235  * refer to timer_after() for jiffies wrapping handling
236  */
237 static inline int ccmp_replay_check(u8 *pn_n, u8 *pn_o)
238 {
239 	u32 iv32_n, iv16_n;
240 	u32 iv32_o, iv16_o;
241 
242 	iv32_n = (pn_n[0] << 24) | (pn_n[1] << 16) | (pn_n[2] << 8) | pn_n[3];
243 	iv16_n = (pn_n[4] << 8) | pn_n[5];
244 
245 	iv32_o = (pn_o[0] << 24) | (pn_o[1] << 16) | (pn_o[2] << 8) | pn_o[3];
246 	iv16_o = (pn_o[4] << 8) | pn_o[5];
247 
248 	if ((s32)iv32_n - (s32)iv32_o < 0 ||
249 	    (iv32_n == iv32_o && iv16_n <= iv16_o))
250 		return 1;
251 	return 0;
252 }
253 
254 static int lib80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
255 {
256 	struct lib80211_ccmp_data *key = priv;
257 	u8 keyidx, *pos;
258 	struct ieee80211_hdr *hdr;
259 	struct aead_request *req;
260 	struct scatterlist sg[2];
261 	u8 *aad = key->rx_aad;
262 	u8 iv[AES_BLOCK_LEN];
263 	u8 pn[6];
264 	int aad_len, ret;
265 	size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN;
266 
267 	if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) {
268 		key->dot11RSNAStatsCCMPFormatErrors++;
269 		return -1;
270 	}
271 
272 	hdr = (struct ieee80211_hdr *)skb->data;
273 	pos = skb->data + hdr_len;
274 	keyidx = pos[3];
275 	if (!(keyidx & (1 << 5))) {
276 		net_dbg_ratelimited("CCMP: received packet without ExtIV flag from %pM\n",
277 				    hdr->addr2);
278 		key->dot11RSNAStatsCCMPFormatErrors++;
279 		return -2;
280 	}
281 	keyidx >>= 6;
282 	if (key->key_idx != keyidx) {
283 		net_dbg_ratelimited("CCMP: RX tkey->key_idx=%d frame keyidx=%d\n",
284 				    key->key_idx, keyidx);
285 		return -6;
286 	}
287 	if (!key->key_set) {
288 		net_dbg_ratelimited("CCMP: received packet from %pM with keyid=%d that does not have a configured key\n",
289 				    hdr->addr2, keyidx);
290 		return -3;
291 	}
292 
293 	pn[0] = pos[7];
294 	pn[1] = pos[6];
295 	pn[2] = pos[5];
296 	pn[3] = pos[4];
297 	pn[4] = pos[1];
298 	pn[5] = pos[0];
299 	pos += 8;
300 
301 	if (ccmp_replay_check(pn, key->rx_pn)) {
302 #ifdef CONFIG_LIB80211_DEBUG
303 		net_dbg_ratelimited("CCMP: replay detected: STA=%pM previous PN %02x%02x%02x%02x%02x%02x received PN %02x%02x%02x%02x%02x%02x\n",
304 				    hdr->addr2,
305 				    key->rx_pn[0], key->rx_pn[1], key->rx_pn[2],
306 				    key->rx_pn[3], key->rx_pn[4], key->rx_pn[5],
307 				    pn[0], pn[1], pn[2], pn[3], pn[4], pn[5]);
308 #endif
309 		key->dot11RSNAStatsCCMPReplays++;
310 		return -4;
311 	}
312 
313 	req = aead_request_alloc(key->tfm, GFP_ATOMIC);
314 	if (!req)
315 		return -ENOMEM;
316 
317 	aad_len = ccmp_init_iv_and_aad(hdr, pn, iv, aad);
318 
319 	sg_init_table(sg, 2);
320 	sg_set_buf(&sg[0], aad, aad_len);
321 	sg_set_buf(&sg[1], pos, data_len);
322 
323 	aead_request_set_callback(req, 0, NULL, NULL);
324 	aead_request_set_ad(req, aad_len);
325 	aead_request_set_crypt(req, sg, sg, data_len, iv);
326 
327 	ret = crypto_aead_decrypt(req);
328 	aead_request_free(req);
329 
330 	if (ret) {
331 		net_dbg_ratelimited("CCMP: decrypt failed: STA=%pM (%d)\n",
332 				    hdr->addr2, ret);
333 		key->dot11RSNAStatsCCMPDecryptErrors++;
334 		return -5;
335 	}
336 
337 	memcpy(key->rx_pn, pn, CCMP_PN_LEN);
338 
339 	/* Remove hdr and MIC */
340 	memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len);
341 	skb_pull(skb, CCMP_HDR_LEN);
342 	skb_trim(skb, skb->len - CCMP_MIC_LEN);
343 
344 	return keyidx;
345 }
346 
347 static int lib80211_ccmp_set_key(void *key, int len, u8 * seq, void *priv)
348 {
349 	struct lib80211_ccmp_data *data = priv;
350 	int keyidx;
351 	struct crypto_aead *tfm = data->tfm;
352 
353 	keyidx = data->key_idx;
354 	memset(data, 0, sizeof(*data));
355 	data->key_idx = keyidx;
356 	data->tfm = tfm;
357 	if (len == CCMP_TK_LEN) {
358 		memcpy(data->key, key, CCMP_TK_LEN);
359 		data->key_set = 1;
360 		if (seq) {
361 			data->rx_pn[0] = seq[5];
362 			data->rx_pn[1] = seq[4];
363 			data->rx_pn[2] = seq[3];
364 			data->rx_pn[3] = seq[2];
365 			data->rx_pn[4] = seq[1];
366 			data->rx_pn[5] = seq[0];
367 		}
368 		if (crypto_aead_setauthsize(data->tfm, CCMP_MIC_LEN) ||
369 		    crypto_aead_setkey(data->tfm, data->key, CCMP_TK_LEN))
370 			return -1;
371 	} else if (len == 0)
372 		data->key_set = 0;
373 	else
374 		return -1;
375 
376 	return 0;
377 }
378 
379 static int lib80211_ccmp_get_key(void *key, int len, u8 * seq, void *priv)
380 {
381 	struct lib80211_ccmp_data *data = priv;
382 
383 	if (len < CCMP_TK_LEN)
384 		return -1;
385 
386 	if (!data->key_set)
387 		return 0;
388 	memcpy(key, data->key, CCMP_TK_LEN);
389 
390 	if (seq) {
391 		seq[0] = data->tx_pn[5];
392 		seq[1] = data->tx_pn[4];
393 		seq[2] = data->tx_pn[3];
394 		seq[3] = data->tx_pn[2];
395 		seq[4] = data->tx_pn[1];
396 		seq[5] = data->tx_pn[0];
397 	}
398 
399 	return CCMP_TK_LEN;
400 }
401 
402 static void lib80211_ccmp_print_stats(struct seq_file *m, void *priv)
403 {
404 	struct lib80211_ccmp_data *ccmp = priv;
405 
406 	seq_printf(m,
407 		   "key[%d] alg=CCMP key_set=%d "
408 		   "tx_pn=%02x%02x%02x%02x%02x%02x "
409 		   "rx_pn=%02x%02x%02x%02x%02x%02x "
410 		   "format_errors=%d replays=%d decrypt_errors=%d\n",
411 		   ccmp->key_idx, ccmp->key_set,
412 		   ccmp->tx_pn[0], ccmp->tx_pn[1], ccmp->tx_pn[2],
413 		   ccmp->tx_pn[3], ccmp->tx_pn[4], ccmp->tx_pn[5],
414 		   ccmp->rx_pn[0], ccmp->rx_pn[1], ccmp->rx_pn[2],
415 		   ccmp->rx_pn[3], ccmp->rx_pn[4], ccmp->rx_pn[5],
416 		   ccmp->dot11RSNAStatsCCMPFormatErrors,
417 		   ccmp->dot11RSNAStatsCCMPReplays,
418 		   ccmp->dot11RSNAStatsCCMPDecryptErrors);
419 }
420 
421 static struct lib80211_crypto_ops lib80211_crypt_ccmp = {
422 	.name = "CCMP",
423 	.init = lib80211_ccmp_init,
424 	.deinit = lib80211_ccmp_deinit,
425 	.encrypt_mpdu = lib80211_ccmp_encrypt,
426 	.decrypt_mpdu = lib80211_ccmp_decrypt,
427 	.encrypt_msdu = NULL,
428 	.decrypt_msdu = NULL,
429 	.set_key = lib80211_ccmp_set_key,
430 	.get_key = lib80211_ccmp_get_key,
431 	.print_stats = lib80211_ccmp_print_stats,
432 	.extra_mpdu_prefix_len = CCMP_HDR_LEN,
433 	.extra_mpdu_postfix_len = CCMP_MIC_LEN,
434 	.owner = THIS_MODULE,
435 };
436 
437 static int __init lib80211_crypto_ccmp_init(void)
438 {
439 	return lib80211_register_crypto_ops(&lib80211_crypt_ccmp);
440 }
441 
442 static void __exit lib80211_crypto_ccmp_exit(void)
443 {
444 	lib80211_unregister_crypto_ops(&lib80211_crypt_ccmp);
445 }
446 
447 module_init(lib80211_crypto_ccmp_init);
448 module_exit(lib80211_crypto_ccmp_exit);
449