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TOMOYO Linux Cross Reference
Linux/net/wireless/lib80211_crypt_ccmp.c

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  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 

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