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TOMOYO Linux Cross Reference
Linux/net/wireless/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 <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                 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
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 

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