1 /*
2  * Host AP crypt: host-based CCMP encryption implementation for Host AP driver
3  *
4  * Copyright (c) 2003-2004, Jouni Malinen <jkmaline@cc.hut.fi>
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation. See README and COPYING for
9  * more details.
10  */
11 
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/slab.h>
15 #include <linux/random.h>
16 #include <linux/skbuff.h>
17 #include <linux/netdevice.h>
18 #include <linux/if_ether.h>
19 #include <linux/if_arp.h>
20 #include <linux/string.h>
21 #include <linux/wireless.h>
22 #include "rtllib.h"
23 
24 #include <linux/crypto.h>
25 
26 #include <linux/scatterlist.h>
27 
28 #define AES_BLOCK_LEN 16
29 #define CCMP_HDR_LEN 8
30 #define CCMP_MIC_LEN 8
31 #define CCMP_TK_LEN 16
32 #define CCMP_PN_LEN 6
33 
34 struct rtllib_ccmp_data {
35 	u8 key[CCMP_TK_LEN];
36 	int key_set;
37 
38 	u8 tx_pn[CCMP_PN_LEN];
39 	u8 rx_pn[CCMP_PN_LEN];
40 
41 	u32 dot11RSNAStatsCCMPFormatErrors;
42 	u32 dot11RSNAStatsCCMPReplays;
43 	u32 dot11RSNAStatsCCMPDecryptErrors;
44 
45 	int key_idx;
46 
47 	struct crypto_tfm *tfm;
48 
49 	/* scratch buffers for virt_to_page() (crypto API) */
50 	u8 tx_b0[AES_BLOCK_LEN], tx_b[AES_BLOCK_LEN],
51 		tx_e[AES_BLOCK_LEN], tx_s0[AES_BLOCK_LEN];
52 	u8 rx_b0[AES_BLOCK_LEN], rx_b[AES_BLOCK_LEN], rx_a[AES_BLOCK_LEN];
53 };
54 
55 static void rtllib_ccmp_aes_encrypt(struct crypto_tfm *tfm,
56 			     const u8 pt[16], u8 ct[16])
57 {
58 	crypto_cipher_encrypt_one((void *)tfm, ct, pt);
59 }
60 
61 static void *rtllib_ccmp_init(int key_idx)
62 {
63 	struct rtllib_ccmp_data *priv;
64 
65 	priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
66 	if (priv == NULL)
67 		goto fail;
68 	priv->key_idx = key_idx;
69 
70 	priv->tfm = (void *)crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
71 	if (IS_ERR(priv->tfm)) {
72 		pr_debug("Could not allocate crypto API aes\n");
73 		priv->tfm = NULL;
74 		goto fail;
75 	}
76 	return priv;
77 
78 fail:
79 	if (priv) {
80 		if (priv->tfm)
81 			crypto_free_cipher((void *)priv->tfm);
82 		kfree(priv);
83 	}
84 
85 	return NULL;
86 }
87 
88 
89 static void rtllib_ccmp_deinit(void *priv)
90 {
91 	struct rtllib_ccmp_data *_priv = priv;
92 
93 	if (_priv && _priv->tfm)
94 		crypto_free_cipher((void *)_priv->tfm);
95 	kfree(priv);
96 }
97 
98 
99 static inline void xor_block(u8 *b, u8 *a, size_t len)
100 {
101 	int i;
102 
103 	for (i = 0; i < len; i++)
104 		b[i] ^= a[i];
105 }
106 
107 
108 
109 static void ccmp_init_blocks(struct crypto_tfm *tfm,
110 			     struct rtllib_hdr_4addr *hdr,
111 			     u8 *pn, size_t dlen, u8 *b0, u8 *auth,
112 			     u8 *s0)
113 {
114 	u8 *pos, qc = 0;
115 	size_t aad_len;
116 	u16 fc;
117 	int a4_included, qc_included;
118 	u8 aad[2 * AES_BLOCK_LEN];
119 
120 	fc = le16_to_cpu(hdr->frame_ctl);
121 	a4_included = ((fc & (RTLLIB_FCTL_TODS | RTLLIB_FCTL_FROMDS)) ==
122 		       (RTLLIB_FCTL_TODS | RTLLIB_FCTL_FROMDS));
123 
124 	qc_included = ((WLAN_FC_GET_TYPE(fc) == RTLLIB_FTYPE_DATA) &&
125 		       (WLAN_FC_GET_STYPE(fc) & 0x80));
126 	aad_len = 22;
127 	if (a4_included)
128 		aad_len += 6;
129 	if (qc_included) {
130 		pos = (u8 *) &hdr->addr4;
131 		if (a4_included)
132 			pos += 6;
133 		qc = *pos & 0x0f;
134 		aad_len += 2;
135 	}
136 	/* CCM Initial Block:
137 	 * Flag (Include authentication header, M=3 (8-octet MIC),
138 	 *       L=1 (2-octet Dlen))
139 	 * Nonce: 0x00 | A2 | PN
140 	 * Dlen
141 	 */
142 	b0[0] = 0x59;
143 	b0[1] = qc;
144 	memcpy(b0 + 2, hdr->addr2, ETH_ALEN);
145 	memcpy(b0 + 8, pn, CCMP_PN_LEN);
146 	b0[14] = (dlen >> 8) & 0xff;
147 	b0[15] = dlen & 0xff;
148 
149 	/* AAD:
150 	 * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
151 	 * A1 | A2 | A3
152 	 * SC with bits 4..15 (seq#) masked to zero
153 	 * A4 (if present)
154 	 * QC (if present)
155 	 */
156 	pos = (u8 *) hdr;
157 	aad[0] = 0; /* aad_len >> 8 */
158 	aad[1] = aad_len & 0xff;
159 	aad[2] = pos[0] & 0x8f;
160 	aad[3] = pos[1] & 0xc7;
161 	memcpy(aad + 4, hdr->addr1, 3 * ETH_ALEN);
162 	pos = (u8 *) &hdr->seq_ctl;
163 	aad[22] = pos[0] & 0x0f;
164 	aad[23] = 0; /* all bits masked */
165 	memset(aad + 24, 0, 8);
166 	if (a4_included)
167 		memcpy(aad + 24, hdr->addr4, ETH_ALEN);
168 	if (qc_included) {
169 		aad[a4_included ? 30 : 24] = qc;
170 		/* rest of QC masked */
171 	}
172 
173 	/* Start with the first block and AAD */
174 	rtllib_ccmp_aes_encrypt(tfm, b0, auth);
175 	xor_block(auth, aad, AES_BLOCK_LEN);
176 	rtllib_ccmp_aes_encrypt(tfm, auth, auth);
177 	xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);
178 	rtllib_ccmp_aes_encrypt(tfm, auth, auth);
179 	b0[0] &= 0x07;
180 	b0[14] = b0[15] = 0;
181 	rtllib_ccmp_aes_encrypt(tfm, b0, s0);
182 }
183 
184 
185 
186 static int rtllib_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
187 {
188 	struct rtllib_ccmp_data *key = priv;
189 	int data_len, i;
190 	u8 *pos;
191 	struct rtllib_hdr_4addr *hdr;
192 	struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
193 				    MAX_DEV_ADDR_SIZE);
194 	if (skb_headroom(skb) < CCMP_HDR_LEN ||
195 	    skb_tailroom(skb) < CCMP_MIC_LEN ||
196 	    skb->len < hdr_len)
197 		return -1;
198 
199 	data_len = skb->len - hdr_len;
200 	pos = skb_push(skb, CCMP_HDR_LEN);
201 	memmove(pos, pos + CCMP_HDR_LEN, hdr_len);
202 	pos += hdr_len;
203 
204 	i = CCMP_PN_LEN - 1;
205 	while (i >= 0) {
206 		key->tx_pn[i]++;
207 		if (key->tx_pn[i] != 0)
208 			break;
209 		i--;
210 	}
211 
212 	*pos++ = key->tx_pn[5];
213 	*pos++ = key->tx_pn[4];
214 	*pos++ = 0;
215 	*pos++ = (key->key_idx << 6) | (1 << 5) /* Ext IV included */;
216 	*pos++ = key->tx_pn[3];
217 	*pos++ = key->tx_pn[2];
218 	*pos++ = key->tx_pn[1];
219 	*pos++ = key->tx_pn[0];
220 
221 
222 	hdr = (struct rtllib_hdr_4addr *) skb->data;
223 	if (!tcb_desc->bHwSec) {
224 		int blocks, last, len;
225 		u8 *mic;
226 		u8 *b0 = key->tx_b0;
227 		u8 *b = key->tx_b;
228 		u8 *e = key->tx_e;
229 		u8 *s0 = key->tx_s0;
230 
231 		mic = skb_put(skb, CCMP_MIC_LEN);
232 
233 		ccmp_init_blocks(key->tfm, hdr, key->tx_pn, data_len,
234 				 b0, b, s0);
235 
236 		blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
237 		last = data_len % AES_BLOCK_LEN;
238 
239 		for (i = 1; i <= blocks; i++) {
240 			len = (i == blocks && last) ? last : AES_BLOCK_LEN;
241 			/* Authentication */
242 			xor_block(b, pos, len);
243 			rtllib_ccmp_aes_encrypt(key->tfm, b, b);
244 			/* Encryption, with counter */
245 			b0[14] = (i >> 8) & 0xff;
246 			b0[15] = i & 0xff;
247 			rtllib_ccmp_aes_encrypt(key->tfm, b0, e);
248 			xor_block(pos, e, len);
249 			pos += len;
250 		}
251 
252 		for (i = 0; i < CCMP_MIC_LEN; i++)
253 			mic[i] = b[i] ^ s0[i];
254 	}
255 	return 0;
256 }
257 
258 
259 static int rtllib_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
260 {
261 	struct rtllib_ccmp_data *key = priv;
262 	u8 keyidx, *pos;
263 	struct rtllib_hdr_4addr *hdr;
264 	struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
265 				    MAX_DEV_ADDR_SIZE);
266 	u8 pn[6];
267 
268 	if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) {
269 		key->dot11RSNAStatsCCMPFormatErrors++;
270 		return -1;
271 	}
272 
273 	hdr = (struct rtllib_hdr_4addr *) skb->data;
274 	pos = skb->data + hdr_len;
275 	keyidx = pos[3];
276 	if (!(keyidx & (1 << 5))) {
277 		if (net_ratelimit()) {
278 			pr_debug("CCMP: received packet without ExtIV flag from %pM\n",
279 				 hdr->addr2);
280 		}
281 		key->dot11RSNAStatsCCMPFormatErrors++;
282 		return -2;
283 	}
284 	keyidx >>= 6;
285 	if (key->key_idx != keyidx) {
286 		pr_debug("CCMP: RX tkey->key_idx=%d frame keyidx=%d priv=%p\n",
287 			 key->key_idx, keyidx, priv);
288 		return -6;
289 	}
290 	if (!key->key_set) {
291 		if (net_ratelimit()) {
292 			pr_debug("CCMP: received packet from %pM with keyid=%d that does not have a configured key\n",
293 				 hdr->addr2, keyidx);
294 		}
295 		return -3;
296 	}
297 
298 	pn[0] = pos[7];
299 	pn[1] = pos[6];
300 	pn[2] = pos[5];
301 	pn[3] = pos[4];
302 	pn[4] = pos[1];
303 	pn[5] = pos[0];
304 	pos += 8;
305 	if (memcmp(pn, key->rx_pn, CCMP_PN_LEN) <= 0) {
306 		key->dot11RSNAStatsCCMPReplays++;
307 		return -4;
308 	}
309 	if (!tcb_desc->bHwSec) {
310 		size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN -
311 				  CCMP_MIC_LEN;
312 		u8 *mic = skb->data + skb->len - CCMP_MIC_LEN;
313 		u8 *b0 = key->rx_b0;
314 		u8 *b = key->rx_b;
315 		u8 *a = key->rx_a;
316 		int i, blocks, last, len;
317 
318 
319 		ccmp_init_blocks(key->tfm, hdr, pn, data_len, b0, a, b);
320 		xor_block(mic, b, CCMP_MIC_LEN);
321 
322 		blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);
323 		last = data_len % AES_BLOCK_LEN;
324 
325 		for (i = 1; i <= blocks; i++) {
326 			len = (i == blocks && last) ? last : AES_BLOCK_LEN;
327 			/* Decrypt, with counter */
328 			b0[14] = (i >> 8) & 0xff;
329 			b0[15] = i & 0xff;
330 			rtllib_ccmp_aes_encrypt(key->tfm, b0, b);
331 			xor_block(pos, b, len);
332 			/* Authentication */
333 			xor_block(a, pos, len);
334 			rtllib_ccmp_aes_encrypt(key->tfm, a, a);
335 			pos += len;
336 		}
337 
338 		if (memcmp(mic, a, CCMP_MIC_LEN) != 0) {
339 			if (net_ratelimit()) {
340 				pr_debug("CCMP: decrypt failed: STA= %pM\n",
341 					 hdr->addr2);
342 			}
343 			key->dot11RSNAStatsCCMPDecryptErrors++;
344 			return -5;
345 		}
346 
347 		memcpy(key->rx_pn, pn, CCMP_PN_LEN);
348 	}
349 	/* Remove hdr and MIC */
350 	memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len);
351 	skb_pull(skb, CCMP_HDR_LEN);
352 	skb_trim(skb, skb->len - CCMP_MIC_LEN);
353 
354 	return keyidx;
355 }
356 
357 
358 static int rtllib_ccmp_set_key(void *key, int len, u8 *seq, void *priv)
359 {
360 	struct rtllib_ccmp_data *data = priv;
361 	int keyidx;
362 	struct crypto_tfm *tfm = data->tfm;
363 
364 	keyidx = data->key_idx;
365 	memset(data, 0, sizeof(*data));
366 	data->key_idx = keyidx;
367 	data->tfm = tfm;
368 	if (len == CCMP_TK_LEN) {
369 		memcpy(data->key, key, CCMP_TK_LEN);
370 		data->key_set = 1;
371 		if (seq) {
372 			data->rx_pn[0] = seq[5];
373 			data->rx_pn[1] = seq[4];
374 			data->rx_pn[2] = seq[3];
375 			data->rx_pn[3] = seq[2];
376 			data->rx_pn[4] = seq[1];
377 			data->rx_pn[5] = seq[0];
378 		}
379 		crypto_cipher_setkey((void *)data->tfm, data->key, CCMP_TK_LEN);
380 	} else if (len == 0)
381 		data->key_set = 0;
382 	else
383 		return -1;
384 
385 	return 0;
386 }
387 
388 
389 static int rtllib_ccmp_get_key(void *key, int len, u8 *seq, void *priv)
390 {
391 	struct rtllib_ccmp_data *data = priv;
392 
393 	if (len < CCMP_TK_LEN)
394 		return -1;
395 
396 	if (!data->key_set)
397 		return 0;
398 	memcpy(key, data->key, CCMP_TK_LEN);
399 
400 	if (seq) {
401 		seq[0] = data->tx_pn[5];
402 		seq[1] = data->tx_pn[4];
403 		seq[2] = data->tx_pn[3];
404 		seq[3] = data->tx_pn[2];
405 		seq[4] = data->tx_pn[1];
406 		seq[5] = data->tx_pn[0];
407 	}
408 
409 	return CCMP_TK_LEN;
410 }
411 
412 
413 static void rtllib_ccmp_print_stats(struct seq_file *m, void *priv)
414 {
415 	struct rtllib_ccmp_data *ccmp = priv;
416 
417 	seq_printf(m,
418 		   "key[%d] alg=CCMP key_set=%d tx_pn=%pM rx_pn=%pM format_errors=%d replays=%d decrypt_errors=%d\n",
419 		   ccmp->key_idx, ccmp->key_set,
420 		   ccmp->tx_pn, ccmp->rx_pn,
421 		   ccmp->dot11RSNAStatsCCMPFormatErrors,
422 		   ccmp->dot11RSNAStatsCCMPReplays,
423 		   ccmp->dot11RSNAStatsCCMPDecryptErrors);
424 }
425 
426 static struct lib80211_crypto_ops rtllib_crypt_ccmp = {
427 	.name			= "R-CCMP",
428 	.init			= rtllib_ccmp_init,
429 	.deinit			= rtllib_ccmp_deinit,
430 	.encrypt_mpdu		= rtllib_ccmp_encrypt,
431 	.decrypt_mpdu		= rtllib_ccmp_decrypt,
432 	.encrypt_msdu		= NULL,
433 	.decrypt_msdu		= NULL,
434 	.set_key		= rtllib_ccmp_set_key,
435 	.get_key		= rtllib_ccmp_get_key,
436 	.print_stats		= rtllib_ccmp_print_stats,
437 	.extra_mpdu_prefix_len = CCMP_HDR_LEN,
438 	.extra_mpdu_postfix_len = CCMP_MIC_LEN,
439 	.owner			= THIS_MODULE,
440 };
441 
442 
443 static int __init rtllib_crypto_ccmp_init(void)
444 {
445 	return lib80211_register_crypto_ops(&rtllib_crypt_ccmp);
446 }
447 
448 
449 static void __exit rtllib_crypto_ccmp_exit(void)
450 {
451 	lib80211_unregister_crypto_ops(&rtllib_crypt_ccmp);
452 }
453 
454 module_init(rtllib_crypto_ccmp_init);
455 module_exit(rtllib_crypto_ccmp_exit);
456 
457 MODULE_LICENSE("GPL");
458