1 /*
2  * lib80211 crypt: host-based CCMP encryption implementation for lib80211
3  *
4  * Copyright (c) 2003-2004, Jouni Malinen <j@w1.fi>
5  * Copyright (c) 2008, John W. Linville <linville@tuxdriver.com>
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License version 2 as
9  * published by the Free Software Foundation. See README and COPYING for
10  * more details.
11  */
12 
13 #include <linux/kernel.h>
14 #include <linux/err.h>
15 #include <linux/module.h>
16 #include <linux/init.h>
17 #include <linux/slab.h>
18 #include <linux/random.h>
19 #include <linux/skbuff.h>
20 #include <linux/netdevice.h>
21 #include <linux/if_ether.h>
22 #include <linux/if_arp.h>
23 #include <asm/string.h>
24 #include <linux/wireless.h>
25 
26 #include <linux/ieee80211.h>
27 
28 #include <linux/crypto.h>
29 
30 #include <net/lib80211.h>
31 
32 MODULE_AUTHOR("Jouni Malinen");
33 MODULE_DESCRIPTION("Host AP crypt: CCMP");
34 MODULE_LICENSE("GPL");
35 
36 #define AES_BLOCK_LEN 16
37 #define CCMP_HDR_LEN 8
38 #define CCMP_MIC_LEN 8
39 #define CCMP_TK_LEN 16
40 #define CCMP_PN_LEN 6
41 
42 struct lib80211_ccmp_data {
43 	u8 key[CCMP_TK_LEN];
44 	int key_set;
45 
46 	u8 tx_pn[CCMP_PN_LEN];
47 	u8 rx_pn[CCMP_PN_LEN];
48 
49 	u32 dot11RSNAStatsCCMPFormatErrors;
50 	u32 dot11RSNAStatsCCMPReplays;
51 	u32 dot11RSNAStatsCCMPDecryptErrors;
52 
53 	int key_idx;
54 
55 	struct crypto_cipher *tfm;
56 
57 	/* scratch buffers for virt_to_page() (crypto API) */
58 	u8 tx_b0[AES_BLOCK_LEN], tx_b[AES_BLOCK_LEN],
59 	    tx_e[AES_BLOCK_LEN], tx_s0[AES_BLOCK_LEN];
60 	u8 rx_b0[AES_BLOCK_LEN], rx_b[AES_BLOCK_LEN], rx_a[AES_BLOCK_LEN];
61 };
62 
63 static inline void lib80211_ccmp_aes_encrypt(struct crypto_cipher *tfm,
64 					      const u8 pt[16], u8 ct[16])
65 {
66 	crypto_cipher_encrypt_one(tfm, ct, pt);
67 }
68 
69 static void *lib80211_ccmp_init(int key_idx)
70 {
71 	struct lib80211_ccmp_data *priv;
72 
73 	priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
74 	if (priv == NULL)
75 		goto fail;
76 	priv->key_idx = key_idx;
77 
78 	priv->tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
79 	if (IS_ERR(priv->tfm)) {
80 		priv->tfm = NULL;
81 		goto fail;
82 	}
83 
84 	return priv;
85 
86       fail:
87 	if (priv) {
88 		if (priv->tfm)
89 			crypto_free_cipher(priv->tfm);
90 		kfree(priv);
91 	}
92 
93 	return NULL;
94 }
95 
96 static void lib80211_ccmp_deinit(void *priv)
97 {
98 	struct lib80211_ccmp_data *_priv = priv;
99 	if (_priv && _priv->tfm)
100 		crypto_free_cipher(_priv->tfm);
101 	kfree(priv);
102 }
103 
104 static inline void xor_block(u8 * b, u8 * a, size_t len)
105 {
106 	int i;
107 	for (i = 0; i < len; i++)
108 		b[i] ^= a[i];
109 }
110 
111 static void ccmp_init_blocks(struct crypto_cipher *tfm,
112 			     struct ieee80211_hdr *hdr,
113 			     u8 * pn, size_t dlen, u8 * b0, u8 * auth, u8 * s0)
114 {
115 	u8 *pos, qc = 0;
116 	size_t aad_len;
117 	int a4_included, qc_included;
118 	u8 aad[2 * AES_BLOCK_LEN];
119 
120 	a4_included = ieee80211_has_a4(hdr->frame_control);
121 	qc_included = ieee80211_is_data_qos(hdr->frame_control);
122 
123 	aad_len = 22;
124 	if (a4_included)
125 		aad_len += 6;
126 	if (qc_included) {
127 		pos = (u8 *) & hdr->addr4;
128 		if (a4_included)
129 			pos += 6;
130 		qc = *pos & 0x0f;
131 		aad_len += 2;
132 	}
133 
134 	/* CCM Initial Block:
135 	 * Flag (Include authentication header, M=3 (8-octet MIC),
136 	 *       L=1 (2-octet Dlen))
137 	 * Nonce: 0x00 | A2 | PN
138 	 * Dlen */
139 	b0[0] = 0x59;
140 	b0[1] = qc;
141 	memcpy(b0 + 2, hdr->addr2, ETH_ALEN);
142 	memcpy(b0 + 8, pn, CCMP_PN_LEN);
143 	b0[14] = (dlen >> 8) & 0xff;
144 	b0[15] = dlen & 0xff;
145 
146 	/* AAD:
147 	 * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
148 	 * A1 | A2 | A3
149 	 * SC with bits 4..15 (seq#) masked to zero
150 	 * A4 (if present)
151 	 * QC (if present)
152 	 */
153 	pos = (u8 *) hdr;
154 	aad[0] = 0;		/* aad_len >> 8 */
155 	aad[1] = aad_len & 0xff;
156 	aad[2] = pos[0] & 0x8f;
157 	aad[3] = pos[1] & 0xc7;
158 	memcpy(aad + 4, hdr->addr1, 3 * ETH_ALEN);
159 	pos = (u8 *) & hdr->seq_ctrl;
160 	aad[22] = pos[0] & 0x0f;
161 	aad[23] = 0;		/* all bits masked */
162 	memset(aad + 24, 0, 8);
163 	if (a4_included)
164 		memcpy(aad + 24, hdr->addr4, ETH_ALEN);
165 	if (qc_included) {
166 		aad[a4_included ? 30 : 24] = qc;
167 		/* rest of QC masked */
168 	}
169 
170 	/* Start with the first block and AAD */
171 	lib80211_ccmp_aes_encrypt(tfm, b0, auth);
172 	xor_block(auth, aad, AES_BLOCK_LEN);
173 	lib80211_ccmp_aes_encrypt(tfm, auth, auth);
174 	xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);
175 	lib80211_ccmp_aes_encrypt(tfm, auth, auth);
176 	b0[0] &= 0x07;
177 	b0[14] = b0[15] = 0;
178 	lib80211_ccmp_aes_encrypt(tfm, b0, s0);
179 }
180 
181 static int lib80211_ccmp_hdr(struct sk_buff *skb, int hdr_len,
182 			      u8 *aeskey, int keylen, void *priv)
183 {
184 	struct lib80211_ccmp_data *key = priv;
185 	int i;
186 	u8 *pos;
187 
188 	if (skb_headroom(skb) < CCMP_HDR_LEN || skb->len < hdr_len)
189 		return -1;
190 
191 	if (aeskey != NULL && keylen >= CCMP_TK_LEN)
192 		memcpy(aeskey, key->key, CCMP_TK_LEN);
193 
194 	pos = skb_push(skb, CCMP_HDR_LEN);
195 	memmove(pos, pos + CCMP_HDR_LEN, hdr_len);
196 	pos += hdr_len;
197 
198 	i = CCMP_PN_LEN - 1;
199 	while (i >= 0) {
200 		key->tx_pn[i]++;
201 		if (key->tx_pn[i] != 0)
202 			break;
203 		i--;
204 	}
205 
206 	*pos++ = key->tx_pn[5];
207 	*pos++ = key->tx_pn[4];
208 	*pos++ = 0;
209 	*pos++ = (key->key_idx << 6) | (1 << 5) /* Ext IV included */ ;
210 	*pos++ = key->tx_pn[3];
211 	*pos++ = key->tx_pn[2];
212 	*pos++ = key->tx_pn[1];
213 	*pos++ = key->tx_pn[0];
214 
215 	return CCMP_HDR_LEN;
216 }
217 
218 static int lib80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
219 {
220 	struct lib80211_ccmp_data *key = priv;
221 	int data_len, i, blocks, last, len;
222 	u8 *pos, *mic;
223 	struct ieee80211_hdr *hdr;
224 	u8 *b0 = key->tx_b0;
225 	u8 *b = key->tx_b;
226 	u8 *e = key->tx_e;
227 	u8 *s0 = key->tx_s0;
228 
229 	if (skb_tailroom(skb) < CCMP_MIC_LEN || skb->len < hdr_len)
230 		return -1;
231 
232 	data_len = skb->len - hdr_len;
233 	len = lib80211_ccmp_hdr(skb, hdr_len, NULL, 0, priv);
234 	if (len < 0)
235 		return -1;
236 
237 	pos = skb->data + hdr_len + CCMP_HDR_LEN;
238 	hdr = (struct ieee80211_hdr *)skb->data;
239 	ccmp_init_blocks(key->tfm, hdr, key->tx_pn, data_len, b0, b, s0);
240 
241 	blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
242 	last = data_len % AES_BLOCK_LEN;
243 
244 	for (i = 1; i <= blocks; i++) {
245 		len = (i == blocks && last) ? last : AES_BLOCK_LEN;
246 		/* Authentication */
247 		xor_block(b, pos, len);
248 		lib80211_ccmp_aes_encrypt(key->tfm, b, b);
249 		/* Encryption, with counter */
250 		b0[14] = (i >> 8) & 0xff;
251 		b0[15] = i & 0xff;
252 		lib80211_ccmp_aes_encrypt(key->tfm, b0, e);
253 		xor_block(pos, e, len);
254 		pos += len;
255 	}
256 
257 	mic = skb_put(skb, CCMP_MIC_LEN);
258 	for (i = 0; i < CCMP_MIC_LEN; i++)
259 		mic[i] = b[i] ^ s0[i];
260 
261 	return 0;
262 }
263 
264 /*
265  * deal with seq counter wrapping correctly.
266  * refer to timer_after() for jiffies wrapping handling
267  */
268 static inline int ccmp_replay_check(u8 *pn_n, u8 *pn_o)
269 {
270 	u32 iv32_n, iv16_n;
271 	u32 iv32_o, iv16_o;
272 
273 	iv32_n = (pn_n[0] << 24) | (pn_n[1] << 16) | (pn_n[2] << 8) | pn_n[3];
274 	iv16_n = (pn_n[4] << 8) | pn_n[5];
275 
276 	iv32_o = (pn_o[0] << 24) | (pn_o[1] << 16) | (pn_o[2] << 8) | pn_o[3];
277 	iv16_o = (pn_o[4] << 8) | pn_o[5];
278 
279 	if ((s32)iv32_n - (s32)iv32_o < 0 ||
280 	    (iv32_n == iv32_o && iv16_n <= iv16_o))
281 		return 1;
282 	return 0;
283 }
284 
285 static int lib80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
286 {
287 	struct lib80211_ccmp_data *key = priv;
288 	u8 keyidx, *pos;
289 	struct ieee80211_hdr *hdr;
290 	u8 *b0 = key->rx_b0;
291 	u8 *b = key->rx_b;
292 	u8 *a = key->rx_a;
293 	u8 pn[6];
294 	int i, blocks, last, len;
295 	size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN - CCMP_MIC_LEN;
296 	u8 *mic = skb->data + skb->len - CCMP_MIC_LEN;
297 
298 	if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) {
299 		key->dot11RSNAStatsCCMPFormatErrors++;
300 		return -1;
301 	}
302 
303 	hdr = (struct ieee80211_hdr *)skb->data;
304 	pos = skb->data + hdr_len;
305 	keyidx = pos[3];
306 	if (!(keyidx & (1 << 5))) {
307 		net_dbg_ratelimited("CCMP: received packet without ExtIV flag from %pM\n",
308 				    hdr->addr2);
309 		key->dot11RSNAStatsCCMPFormatErrors++;
310 		return -2;
311 	}
312 	keyidx >>= 6;
313 	if (key->key_idx != keyidx) {
314 		net_dbg_ratelimited("CCMP: RX tkey->key_idx=%d frame keyidx=%d\n",
315 				    key->key_idx, keyidx);
316 		return -6;
317 	}
318 	if (!key->key_set) {
319 		net_dbg_ratelimited("CCMP: received packet from %pM with keyid=%d that does not have a configured key\n",
320 				    hdr->addr2, keyidx);
321 		return -3;
322 	}
323 
324 	pn[0] = pos[7];
325 	pn[1] = pos[6];
326 	pn[2] = pos[5];
327 	pn[3] = pos[4];
328 	pn[4] = pos[1];
329 	pn[5] = pos[0];
330 	pos += 8;
331 
332 	if (ccmp_replay_check(pn, key->rx_pn)) {
333 #ifdef CONFIG_LIB80211_DEBUG
334 		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",
335 				    hdr->addr2,
336 				    key->rx_pn[0], key->rx_pn[1], key->rx_pn[2],
337 				    key->rx_pn[3], key->rx_pn[4], key->rx_pn[5],
338 				    pn[0], pn[1], pn[2], pn[3], pn[4], pn[5]);
339 #endif
340 		key->dot11RSNAStatsCCMPReplays++;
341 		return -4;
342 	}
343 
344 	ccmp_init_blocks(key->tfm, hdr, pn, data_len, b0, a, b);
345 	xor_block(mic, b, CCMP_MIC_LEN);
346 
347 	blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
348 	last = data_len % AES_BLOCK_LEN;
349 
350 	for (i = 1; i <= blocks; i++) {
351 		len = (i == blocks && last) ? last : AES_BLOCK_LEN;
352 		/* Decrypt, with counter */
353 		b0[14] = (i >> 8) & 0xff;
354 		b0[15] = i & 0xff;
355 		lib80211_ccmp_aes_encrypt(key->tfm, b0, b);
356 		xor_block(pos, b, len);
357 		/* Authentication */
358 		xor_block(a, pos, len);
359 		lib80211_ccmp_aes_encrypt(key->tfm, a, a);
360 		pos += len;
361 	}
362 
363 	if (memcmp(mic, a, CCMP_MIC_LEN) != 0) {
364 		net_dbg_ratelimited("CCMP: decrypt failed: STA=%pM\n",
365 				    hdr->addr2);
366 		key->dot11RSNAStatsCCMPDecryptErrors++;
367 		return -5;
368 	}
369 
370 	memcpy(key->rx_pn, pn, CCMP_PN_LEN);
371 
372 	/* Remove hdr and MIC */
373 	memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len);
374 	skb_pull(skb, CCMP_HDR_LEN);
375 	skb_trim(skb, skb->len - CCMP_MIC_LEN);
376 
377 	return keyidx;
378 }
379 
380 static int lib80211_ccmp_set_key(void *key, int len, u8 * seq, void *priv)
381 {
382 	struct lib80211_ccmp_data *data = priv;
383 	int keyidx;
384 	struct crypto_cipher *tfm = data->tfm;
385 
386 	keyidx = data->key_idx;
387 	memset(data, 0, sizeof(*data));
388 	data->key_idx = keyidx;
389 	data->tfm = tfm;
390 	if (len == CCMP_TK_LEN) {
391 		memcpy(data->key, key, CCMP_TK_LEN);
392 		data->key_set = 1;
393 		if (seq) {
394 			data->rx_pn[0] = seq[5];
395 			data->rx_pn[1] = seq[4];
396 			data->rx_pn[2] = seq[3];
397 			data->rx_pn[3] = seq[2];
398 			data->rx_pn[4] = seq[1];
399 			data->rx_pn[5] = seq[0];
400 		}
401 		crypto_cipher_setkey(data->tfm, data->key, CCMP_TK_LEN);
402 	} else if (len == 0)
403 		data->key_set = 0;
404 	else
405 		return -1;
406 
407 	return 0;
408 }
409 
410 static int lib80211_ccmp_get_key(void *key, int len, u8 * seq, void *priv)
411 {
412 	struct lib80211_ccmp_data *data = priv;
413 
414 	if (len < CCMP_TK_LEN)
415 		return -1;
416 
417 	if (!data->key_set)
418 		return 0;
419 	memcpy(key, data->key, CCMP_TK_LEN);
420 
421 	if (seq) {
422 		seq[0] = data->tx_pn[5];
423 		seq[1] = data->tx_pn[4];
424 		seq[2] = data->tx_pn[3];
425 		seq[3] = data->tx_pn[2];
426 		seq[4] = data->tx_pn[1];
427 		seq[5] = data->tx_pn[0];
428 	}
429 
430 	return CCMP_TK_LEN;
431 }
432 
433 static void lib80211_ccmp_print_stats(struct seq_file *m, void *priv)
434 {
435 	struct lib80211_ccmp_data *ccmp = priv;
436 
437 	seq_printf(m,
438 		   "key[%d] alg=CCMP key_set=%d "
439 		   "tx_pn=%02x%02x%02x%02x%02x%02x "
440 		   "rx_pn=%02x%02x%02x%02x%02x%02x "
441 		   "format_errors=%d replays=%d decrypt_errors=%d\n",
442 		   ccmp->key_idx, ccmp->key_set,
443 		   ccmp->tx_pn[0], ccmp->tx_pn[1], ccmp->tx_pn[2],
444 		   ccmp->tx_pn[3], ccmp->tx_pn[4], ccmp->tx_pn[5],
445 		   ccmp->rx_pn[0], ccmp->rx_pn[1], ccmp->rx_pn[2],
446 		   ccmp->rx_pn[3], ccmp->rx_pn[4], ccmp->rx_pn[5],
447 		   ccmp->dot11RSNAStatsCCMPFormatErrors,
448 		   ccmp->dot11RSNAStatsCCMPReplays,
449 		   ccmp->dot11RSNAStatsCCMPDecryptErrors);
450 }
451 
452 static struct lib80211_crypto_ops lib80211_crypt_ccmp = {
453 	.name = "CCMP",
454 	.init = lib80211_ccmp_init,
455 	.deinit = lib80211_ccmp_deinit,
456 	.encrypt_mpdu = lib80211_ccmp_encrypt,
457 	.decrypt_mpdu = lib80211_ccmp_decrypt,
458 	.encrypt_msdu = NULL,
459 	.decrypt_msdu = NULL,
460 	.set_key = lib80211_ccmp_set_key,
461 	.get_key = lib80211_ccmp_get_key,
462 	.print_stats = lib80211_ccmp_print_stats,
463 	.extra_mpdu_prefix_len = CCMP_HDR_LEN,
464 	.extra_mpdu_postfix_len = CCMP_MIC_LEN,
465 	.owner = THIS_MODULE,
466 };
467 
468 static int __init lib80211_crypto_ccmp_init(void)
469 {
470 	return lib80211_register_crypto_ops(&lib80211_crypt_ccmp);
471 }
472 
473 static void __exit lib80211_crypto_ccmp_exit(void)
474 {
475 	lib80211_unregister_crypto_ops(&lib80211_crypt_ccmp);
476 }
477 
478 module_init(lib80211_crypto_ccmp_init);
479 module_exit(lib80211_crypto_ccmp_exit);
480