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TOMOYO Linux Cross Reference
Linux/net/tls/tls_device_fallback.c

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  1 /* Copyright (c) 2018, Mellanox Technologies All rights reserved.
  2  *
  3  * This software is available to you under a choice of one of two
  4  * licenses.  You may choose to be licensed under the terms of the GNU
  5  * General Public License (GPL) Version 2, available from the file
  6  * COPYING in the main directory of this source tree, or the
  7  * OpenIB.org BSD license below:
  8  *
  9  *     Redistribution and use in source and binary forms, with or
 10  *     without modification, are permitted provided that the following
 11  *     conditions are met:
 12  *
 13  *      - Redistributions of source code must retain the above
 14  *        copyright notice, this list of conditions and the following
 15  *        disclaimer.
 16  *
 17  *      - Redistributions in binary form must reproduce the above
 18  *        copyright notice, this list of conditions and the following
 19  *        disclaimer in the documentation and/or other materials
 20  *        provided with the distribution.
 21  *
 22  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 23  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 24  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 25  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 26  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 27  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 28  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 29  * SOFTWARE.
 30  */
 31 
 32 #include <net/tls.h>
 33 #include <crypto/aead.h>
 34 #include <crypto/scatterwalk.h>
 35 #include <net/ip6_checksum.h>
 36 
 37 static void chain_to_walk(struct scatterlist *sg, struct scatter_walk *walk)
 38 {
 39         struct scatterlist *src = walk->sg;
 40         int diff = walk->offset - src->offset;
 41 
 42         sg_set_page(sg, sg_page(src),
 43                     src->length - diff, walk->offset);
 44 
 45         scatterwalk_crypto_chain(sg, sg_next(src), 2);
 46 }
 47 
 48 static int tls_enc_record(struct aead_request *aead_req,
 49                           struct crypto_aead *aead, char *aad,
 50                           char *iv, __be64 rcd_sn,
 51                           struct scatter_walk *in,
 52                           struct scatter_walk *out, int *in_len)
 53 {
 54         unsigned char buf[TLS_HEADER_SIZE + TLS_CIPHER_AES_GCM_128_IV_SIZE];
 55         struct scatterlist sg_in[3];
 56         struct scatterlist sg_out[3];
 57         u16 len;
 58         int rc;
 59 
 60         len = min_t(int, *in_len, ARRAY_SIZE(buf));
 61 
 62         scatterwalk_copychunks(buf, in, len, 0);
 63         scatterwalk_copychunks(buf, out, len, 1);
 64 
 65         *in_len -= len;
 66         if (!*in_len)
 67                 return 0;
 68 
 69         scatterwalk_pagedone(in, 0, 1);
 70         scatterwalk_pagedone(out, 1, 1);
 71 
 72         len = buf[4] | (buf[3] << 8);
 73         len -= TLS_CIPHER_AES_GCM_128_IV_SIZE;
 74 
 75         tls_make_aad(aad, len - TLS_CIPHER_AES_GCM_128_TAG_SIZE,
 76                 (char *)&rcd_sn, sizeof(rcd_sn), buf[0],
 77                 TLS_1_2_VERSION);
 78 
 79         memcpy(iv + TLS_CIPHER_AES_GCM_128_SALT_SIZE, buf + TLS_HEADER_SIZE,
 80                TLS_CIPHER_AES_GCM_128_IV_SIZE);
 81 
 82         sg_init_table(sg_in, ARRAY_SIZE(sg_in));
 83         sg_init_table(sg_out, ARRAY_SIZE(sg_out));
 84         sg_set_buf(sg_in, aad, TLS_AAD_SPACE_SIZE);
 85         sg_set_buf(sg_out, aad, TLS_AAD_SPACE_SIZE);
 86         chain_to_walk(sg_in + 1, in);
 87         chain_to_walk(sg_out + 1, out);
 88 
 89         *in_len -= len;
 90         if (*in_len < 0) {
 91                 *in_len += TLS_CIPHER_AES_GCM_128_TAG_SIZE;
 92                 /* the input buffer doesn't contain the entire record.
 93                  * trim len accordingly. The resulting authentication tag
 94                  * will contain garbage, but we don't care, so we won't
 95                  * include any of it in the output skb
 96                  * Note that we assume the output buffer length
 97                  * is larger then input buffer length + tag size
 98                  */
 99                 if (*in_len < 0)
100                         len += *in_len;
101 
102                 *in_len = 0;
103         }
104 
105         if (*in_len) {
106                 scatterwalk_copychunks(NULL, in, len, 2);
107                 scatterwalk_pagedone(in, 0, 1);
108                 scatterwalk_copychunks(NULL, out, len, 2);
109                 scatterwalk_pagedone(out, 1, 1);
110         }
111 
112         len -= TLS_CIPHER_AES_GCM_128_TAG_SIZE;
113         aead_request_set_crypt(aead_req, sg_in, sg_out, len, iv);
114 
115         rc = crypto_aead_encrypt(aead_req);
116 
117         return rc;
118 }
119 
120 static void tls_init_aead_request(struct aead_request *aead_req,
121                                   struct crypto_aead *aead)
122 {
123         aead_request_set_tfm(aead_req, aead);
124         aead_request_set_ad(aead_req, TLS_AAD_SPACE_SIZE);
125 }
126 
127 static struct aead_request *tls_alloc_aead_request(struct crypto_aead *aead,
128                                                    gfp_t flags)
129 {
130         unsigned int req_size = sizeof(struct aead_request) +
131                 crypto_aead_reqsize(aead);
132         struct aead_request *aead_req;
133 
134         aead_req = kzalloc(req_size, flags);
135         if (aead_req)
136                 tls_init_aead_request(aead_req, aead);
137         return aead_req;
138 }
139 
140 static int tls_enc_records(struct aead_request *aead_req,
141                            struct crypto_aead *aead, struct scatterlist *sg_in,
142                            struct scatterlist *sg_out, char *aad, char *iv,
143                            u64 rcd_sn, int len)
144 {
145         struct scatter_walk out, in;
146         int rc;
147 
148         scatterwalk_start(&in, sg_in);
149         scatterwalk_start(&out, sg_out);
150 
151         do {
152                 rc = tls_enc_record(aead_req, aead, aad, iv,
153                                     cpu_to_be64(rcd_sn), &in, &out, &len);
154                 rcd_sn++;
155 
156         } while (rc == 0 && len);
157 
158         scatterwalk_done(&in, 0, 0);
159         scatterwalk_done(&out, 1, 0);
160 
161         return rc;
162 }
163 
164 /* Can't use icsk->icsk_af_ops->send_check here because the ip addresses
165  * might have been changed by NAT.
166  */
167 static void update_chksum(struct sk_buff *skb, int headln)
168 {
169         struct tcphdr *th = tcp_hdr(skb);
170         int datalen = skb->len - headln;
171         const struct ipv6hdr *ipv6h;
172         const struct iphdr *iph;
173 
174         /* We only changed the payload so if we are using partial we don't
175          * need to update anything.
176          */
177         if (likely(skb->ip_summed == CHECKSUM_PARTIAL))
178                 return;
179 
180         skb->ip_summed = CHECKSUM_PARTIAL;
181         skb->csum_start = skb_transport_header(skb) - skb->head;
182         skb->csum_offset = offsetof(struct tcphdr, check);
183 
184         if (skb->sk->sk_family == AF_INET6) {
185                 ipv6h = ipv6_hdr(skb);
186                 th->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
187                                              datalen, IPPROTO_TCP, 0);
188         } else {
189                 iph = ip_hdr(skb);
190                 th->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, datalen,
191                                                IPPROTO_TCP, 0);
192         }
193 }
194 
195 static void complete_skb(struct sk_buff *nskb, struct sk_buff *skb, int headln)
196 {
197         struct sock *sk = skb->sk;
198         int delta;
199 
200         skb_copy_header(nskb, skb);
201 
202         skb_put(nskb, skb->len);
203         memcpy(nskb->data, skb->data, headln);
204 
205         nskb->destructor = skb->destructor;
206         nskb->sk = sk;
207         skb->destructor = NULL;
208         skb->sk = NULL;
209 
210         update_chksum(nskb, headln);
211 
212         /* sock_efree means skb must gone through skb_orphan_partial() */
213         if (nskb->destructor == sock_efree)
214                 return;
215 
216         delta = nskb->truesize - skb->truesize;
217         if (likely(delta < 0))
218                 WARN_ON_ONCE(refcount_sub_and_test(-delta, &sk->sk_wmem_alloc));
219         else if (delta)
220                 refcount_add(delta, &sk->sk_wmem_alloc);
221 }
222 
223 /* This function may be called after the user socket is already
224  * closed so make sure we don't use anything freed during
225  * tls_sk_proto_close here
226  */
227 
228 static int fill_sg_in(struct scatterlist *sg_in,
229                       struct sk_buff *skb,
230                       struct tls_offload_context_tx *ctx,
231                       u64 *rcd_sn,
232                       s32 *sync_size,
233                       int *resync_sgs)
234 {
235         int tcp_payload_offset = skb_transport_offset(skb) + tcp_hdrlen(skb);
236         int payload_len = skb->len - tcp_payload_offset;
237         u32 tcp_seq = ntohl(tcp_hdr(skb)->seq);
238         struct tls_record_info *record;
239         unsigned long flags;
240         int remaining;
241         int i;
242 
243         spin_lock_irqsave(&ctx->lock, flags);
244         record = tls_get_record(ctx, tcp_seq, rcd_sn);
245         if (!record) {
246                 spin_unlock_irqrestore(&ctx->lock, flags);
247                 return -EINVAL;
248         }
249 
250         *sync_size = tcp_seq - tls_record_start_seq(record);
251         if (*sync_size < 0) {
252                 int is_start_marker = tls_record_is_start_marker(record);
253 
254                 spin_unlock_irqrestore(&ctx->lock, flags);
255                 /* This should only occur if the relevant record was
256                  * already acked. In that case it should be ok
257                  * to drop the packet and avoid retransmission.
258                  *
259                  * There is a corner case where the packet contains
260                  * both an acked and a non-acked record.
261                  * We currently don't handle that case and rely
262                  * on TCP to retranmit a packet that doesn't contain
263                  * already acked payload.
264                  */
265                 if (!is_start_marker)
266                         *sync_size = 0;
267                 return -EINVAL;
268         }
269 
270         remaining = *sync_size;
271         for (i = 0; remaining > 0; i++) {
272                 skb_frag_t *frag = &record->frags[i];
273 
274                 __skb_frag_ref(frag);
275                 sg_set_page(sg_in + i, skb_frag_page(frag),
276                             skb_frag_size(frag), skb_frag_off(frag));
277 
278                 remaining -= skb_frag_size(frag);
279 
280                 if (remaining < 0)
281                         sg_in[i].length += remaining;
282         }
283         *resync_sgs = i;
284 
285         spin_unlock_irqrestore(&ctx->lock, flags);
286         if (skb_to_sgvec(skb, &sg_in[i], tcp_payload_offset, payload_len) < 0)
287                 return -EINVAL;
288 
289         return 0;
290 }
291 
292 static void fill_sg_out(struct scatterlist sg_out[3], void *buf,
293                         struct tls_context *tls_ctx,
294                         struct sk_buff *nskb,
295                         int tcp_payload_offset,
296                         int payload_len,
297                         int sync_size,
298                         void *dummy_buf)
299 {
300         sg_set_buf(&sg_out[0], dummy_buf, sync_size);
301         sg_set_buf(&sg_out[1], nskb->data + tcp_payload_offset, payload_len);
302         /* Add room for authentication tag produced by crypto */
303         dummy_buf += sync_size;
304         sg_set_buf(&sg_out[2], dummy_buf, TLS_CIPHER_AES_GCM_128_TAG_SIZE);
305 }
306 
307 static struct sk_buff *tls_enc_skb(struct tls_context *tls_ctx,
308                                    struct scatterlist sg_out[3],
309                                    struct scatterlist *sg_in,
310                                    struct sk_buff *skb,
311                                    s32 sync_size, u64 rcd_sn)
312 {
313         int tcp_payload_offset = skb_transport_offset(skb) + tcp_hdrlen(skb);
314         struct tls_offload_context_tx *ctx = tls_offload_ctx_tx(tls_ctx);
315         int payload_len = skb->len - tcp_payload_offset;
316         void *buf, *iv, *aad, *dummy_buf;
317         struct aead_request *aead_req;
318         struct sk_buff *nskb = NULL;
319         int buf_len;
320 
321         aead_req = tls_alloc_aead_request(ctx->aead_send, GFP_ATOMIC);
322         if (!aead_req)
323                 return NULL;
324 
325         buf_len = TLS_CIPHER_AES_GCM_128_SALT_SIZE +
326                   TLS_CIPHER_AES_GCM_128_IV_SIZE +
327                   TLS_AAD_SPACE_SIZE +
328                   sync_size +
329                   TLS_CIPHER_AES_GCM_128_TAG_SIZE;
330         buf = kmalloc(buf_len, GFP_ATOMIC);
331         if (!buf)
332                 goto free_req;
333 
334         iv = buf;
335         memcpy(iv, tls_ctx->crypto_send.aes_gcm_128.salt,
336                TLS_CIPHER_AES_GCM_128_SALT_SIZE);
337         aad = buf + TLS_CIPHER_AES_GCM_128_SALT_SIZE +
338               TLS_CIPHER_AES_GCM_128_IV_SIZE;
339         dummy_buf = aad + TLS_AAD_SPACE_SIZE;
340 
341         nskb = alloc_skb(skb_headroom(skb) + skb->len, GFP_ATOMIC);
342         if (!nskb)
343                 goto free_buf;
344 
345         skb_reserve(nskb, skb_headroom(skb));
346 
347         fill_sg_out(sg_out, buf, tls_ctx, nskb, tcp_payload_offset,
348                     payload_len, sync_size, dummy_buf);
349 
350         if (tls_enc_records(aead_req, ctx->aead_send, sg_in, sg_out, aad, iv,
351                             rcd_sn, sync_size + payload_len) < 0)
352                 goto free_nskb;
353 
354         complete_skb(nskb, skb, tcp_payload_offset);
355 
356         /* validate_xmit_skb_list assumes that if the skb wasn't segmented
357          * nskb->prev will point to the skb itself
358          */
359         nskb->prev = nskb;
360 
361 free_buf:
362         kfree(buf);
363 free_req:
364         kfree(aead_req);
365         return nskb;
366 free_nskb:
367         kfree_skb(nskb);
368         nskb = NULL;
369         goto free_buf;
370 }
371 
372 static struct sk_buff *tls_sw_fallback(struct sock *sk, struct sk_buff *skb)
373 {
374         int tcp_payload_offset = skb_transport_offset(skb) + tcp_hdrlen(skb);
375         struct tls_context *tls_ctx = tls_get_ctx(sk);
376         struct tls_offload_context_tx *ctx = tls_offload_ctx_tx(tls_ctx);
377         int payload_len = skb->len - tcp_payload_offset;
378         struct scatterlist *sg_in, sg_out[3];
379         struct sk_buff *nskb = NULL;
380         int sg_in_max_elements;
381         int resync_sgs = 0;
382         s32 sync_size = 0;
383         u64 rcd_sn;
384 
385         /* worst case is:
386          * MAX_SKB_FRAGS in tls_record_info
387          * MAX_SKB_FRAGS + 1 in SKB head and frags.
388          */
389         sg_in_max_elements = 2 * MAX_SKB_FRAGS + 1;
390 
391         if (!payload_len)
392                 return skb;
393 
394         sg_in = kmalloc_array(sg_in_max_elements, sizeof(*sg_in), GFP_ATOMIC);
395         if (!sg_in)
396                 goto free_orig;
397 
398         sg_init_table(sg_in, sg_in_max_elements);
399         sg_init_table(sg_out, ARRAY_SIZE(sg_out));
400 
401         if (fill_sg_in(sg_in, skb, ctx, &rcd_sn, &sync_size, &resync_sgs)) {
402                 /* bypass packets before kernel TLS socket option was set */
403                 if (sync_size < 0 && payload_len <= -sync_size)
404                         nskb = skb_get(skb);
405                 goto put_sg;
406         }
407 
408         nskb = tls_enc_skb(tls_ctx, sg_out, sg_in, skb, sync_size, rcd_sn);
409 
410 put_sg:
411         while (resync_sgs)
412                 put_page(sg_page(&sg_in[--resync_sgs]));
413         kfree(sg_in);
414 free_orig:
415         if (nskb)
416                 consume_skb(skb);
417         else
418                 kfree_skb(skb);
419         return nskb;
420 }
421 
422 struct sk_buff *tls_validate_xmit_skb(struct sock *sk,
423                                       struct net_device *dev,
424                                       struct sk_buff *skb)
425 {
426         if (dev == tls_get_ctx(sk)->netdev)
427                 return skb;
428 
429         return tls_sw_fallback(sk, skb);
430 }
431 EXPORT_SYMBOL_GPL(tls_validate_xmit_skb);
432 
433 struct sk_buff *tls_encrypt_skb(struct sk_buff *skb)
434 {
435         return tls_sw_fallback(skb->sk, skb);
436 }
437 EXPORT_SYMBOL_GPL(tls_encrypt_skb);
438 
439 int tls_sw_fallback_init(struct sock *sk,
440                          struct tls_offload_context_tx *offload_ctx,
441                          struct tls_crypto_info *crypto_info)
442 {
443         const u8 *key;
444         int rc;
445 
446         offload_ctx->aead_send =
447             crypto_alloc_aead("gcm(aes)", 0, CRYPTO_ALG_ASYNC);
448         if (IS_ERR(offload_ctx->aead_send)) {
449                 rc = PTR_ERR(offload_ctx->aead_send);
450                 pr_err_ratelimited("crypto_alloc_aead failed rc=%d\n", rc);
451                 offload_ctx->aead_send = NULL;
452                 goto err_out;
453         }
454 
455         key = ((struct tls12_crypto_info_aes_gcm_128 *)crypto_info)->key;
456 
457         rc = crypto_aead_setkey(offload_ctx->aead_send, key,
458                                 TLS_CIPHER_AES_GCM_128_KEY_SIZE);
459         if (rc)
460                 goto free_aead;
461 
462         rc = crypto_aead_setauthsize(offload_ctx->aead_send,
463                                      TLS_CIPHER_AES_GCM_128_TAG_SIZE);
464         if (rc)
465                 goto free_aead;
466 
467         return 0;
468 free_aead:
469         crypto_free_aead(offload_ctx->aead_send);
470 err_out:
471         return rc;
472 }
473 

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