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lib80211_crypt_ccmp.c
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1 /*
2  * lib80211 crypt: host-based CCMP encryption implementation for lib80211
3  *
4  * Copyright (c) 2003-2004, Jouni Malinen <[email protected]>
5  * Copyright (c) 2008, John W. Linville <[email protected]>
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 
44  int key_set;
45 
48 
52 
53  int key_idx;
54 
55  struct crypto_cipher *tfm;
56 
57  /* scratch buffers for virt_to_page() (crypto API) */
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) {
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);
310  return -2;
311  }
312  keyidx >>= 6;
313  if (key->key_idx != keyidx) {
314  printk(KERN_DEBUG "CCMP: RX tkey->key_idx=%d frame "
315  "keyidx=%d priv=%p\n", key->key_idx, keyidx, priv);
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
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);
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 char *lib80211_ccmp_print_stats(char *p, void *priv)
434 {
435  struct lib80211_ccmp_data *ccmp = priv;
436 
437  p += sprintf(p, "key[%d] alg=CCMP key_set=%d "
438  "tx_pn=%02x%02x%02x%02x%02x%02x "
439  "rx_pn=%02x%02x%02x%02x%02x%02x "
440  "format_errors=%d replays=%d decrypt_errors=%d\n",
441  ccmp->key_idx, ccmp->key_set,
442  ccmp->tx_pn[0], ccmp->tx_pn[1], ccmp->tx_pn[2],
443  ccmp->tx_pn[3], ccmp->tx_pn[4], ccmp->tx_pn[5],
444  ccmp->rx_pn[0], ccmp->rx_pn[1], ccmp->rx_pn[2],
445  ccmp->rx_pn[3], ccmp->rx_pn[4], ccmp->rx_pn[5],
449 
450  return p;
451 }
452 
453 static struct lib80211_crypto_ops lib80211_crypt_ccmp = {
454  .name = "CCMP",
455  .init = lib80211_ccmp_init,
456  .deinit = lib80211_ccmp_deinit,
457  .encrypt_mpdu = lib80211_ccmp_encrypt,
458  .decrypt_mpdu = lib80211_ccmp_decrypt,
459  .encrypt_msdu = NULL,
460  .decrypt_msdu = NULL,
461  .set_key = lib80211_ccmp_set_key,
462  .get_key = lib80211_ccmp_get_key,
463  .print_stats = lib80211_ccmp_print_stats,
464  .extra_mpdu_prefix_len = CCMP_HDR_LEN,
465  .extra_mpdu_postfix_len = CCMP_MIC_LEN,
466  .owner = THIS_MODULE,
467 };
468 
469 static int __init lib80211_crypto_ccmp_init(void)
470 {
471  return lib80211_register_crypto_ops(&lib80211_crypt_ccmp);
472 }
473 
474 static void __exit lib80211_crypto_ccmp_exit(void)
475 {
476  lib80211_unregister_crypto_ops(&lib80211_crypt_ccmp);
477 }
478 
479 module_init(lib80211_crypto_ccmp_init);
480 module_exit(lib80211_crypto_ccmp_exit);