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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2015-2019 Jason A. Donenfeld <[email protected]>. All Rights Reserved.
4 */
5
6#include "queueing.h"
7#include "timers.h"
8#include "device.h"
9#include "peer.h"
10#include "socket.h"
11#include "messages.h"
12#include "cookie.h"
13
14#include <linux/uio.h>
15#include <linux/inetdevice.h>
16#include <linux/socket.h>
17#include <net/ip_tunnels.h>
18#include <net/udp.h>
19#include <net/sock.h>
20
21static void wg_packet_send_handshake_initiation(struct wg_peer *peer)
22{
23 struct message_handshake_initiation packet;
24
25 if (!wg_birthdate_has_expired(atomic64_read(&peer->last_sent_handshake),
26 REKEY_TIMEOUT))
27 return; /* This function is rate limited. */
28
29 atomic64_set(&peer->last_sent_handshake, ktime_get_coarse_boottime_ns());
30 net_dbg_ratelimited("%s: Sending handshake initiation to peer %llu (%pISpfsc)\n",
31 peer->device->dev->name, peer->internal_id,
32 &peer->endpoint.addr);
33
34 if (wg_noise_handshake_create_initiation(&packet, &peer->handshake)) {
35 wg_cookie_add_mac_to_packet(&packet, sizeof(packet), peer);
36 wg_timers_any_authenticated_packet_traversal(peer);
37 wg_timers_any_authenticated_packet_sent(peer);
38 atomic64_set(&peer->last_sent_handshake,
39 ktime_get_coarse_boottime_ns());
40 wg_socket_send_buffer_to_peer(peer, &packet, sizeof(packet),
41 HANDSHAKE_DSCP);
42 wg_timers_handshake_initiated(peer);
43 }
44}
45
46void wg_packet_handshake_send_worker(struct work_struct *work)
47{
48 struct wg_peer *peer = container_of(work, struct wg_peer,
49 transmit_handshake_work);
50
51 wg_packet_send_handshake_initiation(peer);
52 wg_peer_put(peer);
53}
54
55void wg_packet_send_queued_handshake_initiation(struct wg_peer *peer,
56 bool is_retry)
57{
58 if (!is_retry)
59 peer->timer_handshake_attempts = 0;
60
61 rcu_read_lock_bh();
62 /* We check last_sent_handshake here in addition to the actual function
63 * we're queueing up, so that we don't queue things if not strictly
64 * necessary:
65 */
66 if (!wg_birthdate_has_expired(atomic64_read(&peer->last_sent_handshake),
67 REKEY_TIMEOUT) ||
68 unlikely(READ_ONCE(peer->is_dead)))
69 goto out;
70
71 wg_peer_get(peer);
72 /* Queues up calling packet_send_queued_handshakes(peer), where we do a
73 * peer_put(peer) after:
74 */
75 if (!queue_work(peer->device->handshake_send_wq,
76 &peer->transmit_handshake_work))
77 /* If the work was already queued, we want to drop the
78 * extra reference:
79 */
80 wg_peer_put(peer);
81out:
82 rcu_read_unlock_bh();
83}
84
85void wg_packet_send_handshake_response(struct wg_peer *peer)
86{
87 struct message_handshake_response packet;
88
89 atomic64_set(&peer->last_sent_handshake, ktime_get_coarse_boottime_ns());
90 net_dbg_ratelimited("%s: Sending handshake response to peer %llu (%pISpfsc)\n",
91 peer->device->dev->name, peer->internal_id,
92 &peer->endpoint.addr);
93
94 if (wg_noise_handshake_create_response(&packet, &peer->handshake)) {
95 wg_cookie_add_mac_to_packet(&packet, sizeof(packet), peer);
96 if (wg_noise_handshake_begin_session(&peer->handshake,
97 &peer->keypairs)) {
98 wg_timers_session_derived(peer);
99 wg_timers_any_authenticated_packet_traversal(peer);
100 wg_timers_any_authenticated_packet_sent(peer);
101 atomic64_set(&peer->last_sent_handshake,
102 ktime_get_coarse_boottime_ns());
103 wg_socket_send_buffer_to_peer(peer, &packet,
104 sizeof(packet),
105 HANDSHAKE_DSCP);
106 }
107 }
108}
109
110void wg_packet_send_handshake_cookie(struct wg_device *wg,
111 struct sk_buff *initiating_skb,
112 __le32 sender_index)
113{
114 struct message_handshake_cookie packet;
115
116 net_dbg_skb_ratelimited("%s: Sending cookie response for denied handshake message for %pISpfsc\n",
117 wg->dev->name, initiating_skb);
118 wg_cookie_message_create(&packet, initiating_skb, sender_index,
119 &wg->cookie_checker);
120 wg_socket_send_buffer_as_reply_to_skb(wg, initiating_skb, &packet,
121 sizeof(packet));
122}
123
124static void keep_key_fresh(struct wg_peer *peer)
125{
126 struct noise_keypair *keypair;
127 bool send;
128
129 rcu_read_lock_bh();
130 keypair = rcu_dereference_bh(peer->keypairs.current_keypair);
131 send = keypair && READ_ONCE(keypair->sending.is_valid) &&
132 (atomic64_read(&keypair->sending_counter) > REKEY_AFTER_MESSAGES ||
133 (keypair->i_am_the_initiator &&
134 wg_birthdate_has_expired(keypair->sending.birthdate, REKEY_AFTER_TIME)));
135 rcu_read_unlock_bh();
136
137 if (unlikely(send))
138 wg_packet_send_queued_handshake_initiation(peer, false);
139}
140
141static unsigned int calculate_skb_padding(struct sk_buff *skb)
142{
143 unsigned int padded_size, last_unit = skb->len;
144
145 if (unlikely(!PACKET_CB(skb)->mtu))
146 return ALIGN(last_unit, MESSAGE_PADDING_MULTIPLE) - last_unit;
147
148 /* We do this modulo business with the MTU, just in case the networking
149 * layer gives us a packet that's bigger than the MTU. In that case, we
150 * wouldn't want the final subtraction to overflow in the case of the
151 * padded_size being clamped. Fortunately, that's very rarely the case,
152 * so we optimize for that not happening.
153 */
154 if (unlikely(last_unit > PACKET_CB(skb)->mtu))
155 last_unit %= PACKET_CB(skb)->mtu;
156
157 padded_size = min(PACKET_CB(skb)->mtu,
158 ALIGN(last_unit, MESSAGE_PADDING_MULTIPLE));
159 return padded_size - last_unit;
160}
161
162static bool encrypt_packet(struct sk_buff *skb, struct noise_keypair *keypair)
163{
164 unsigned int padding_len, plaintext_len, trailer_len;
165 struct scatterlist sg[MAX_SKB_FRAGS + 8];
166 struct message_data *header;
167 struct sk_buff *trailer;
168 int num_frags;
169
170 /* Force hash calculation before encryption so that flow analysis is
171 * consistent over the inner packet.
172 */
173 skb_get_hash(skb);
174
175 /* Calculate lengths. */
176 padding_len = calculate_skb_padding(skb);
177 trailer_len = padding_len + noise_encrypted_len(0);
178 plaintext_len = skb->len + padding_len;
179
180 /* Expand head section to have room for our header and the network
181 * stack's headers.
182 */
183 if (unlikely(skb_cow_head(skb, DATA_PACKET_HEAD_ROOM) < 0))
184 return false;
185
186 /* Finalize checksum calculation for the inner packet, if required. */
187 if (unlikely(skb->ip_summed == CHECKSUM_PARTIAL &&
188 skb_checksum_help(skb)))
189 return false;
190
191 /* Expand data section to have room for padding and auth tag. */
192 num_frags = skb_cow_data(skb, trailer_len, &trailer);
193 if (unlikely(num_frags < 0 || num_frags > ARRAY_SIZE(sg)))
194 return false;
195
196 /* Set the padding to zeros, and make sure it and the auth tag are part
197 * of the skb.
198 */
199 memset(skb_tail_pointer(trailer), 0, padding_len);
200
201 /* Only after checksumming can we safely add on the padding at the end
202 * and the header.
203 */
204 skb_set_inner_network_header(skb, 0);
205 header = (struct message_data *)skb_push(skb, sizeof(*header));
206 header->header.type = cpu_to_le32(MESSAGE_DATA);
207 header->key_idx = keypair->remote_index;
208 header->counter = cpu_to_le64(PACKET_CB(skb)->nonce);
209 pskb_put(skb, trailer, trailer_len);
210
211 /* Now we can encrypt the scattergather segments */
212 sg_init_table(sg, num_frags);
213 if (skb_to_sgvec(skb, sg, sizeof(struct message_data),
214 noise_encrypted_len(plaintext_len)) <= 0)
215 return false;
216 return chacha20poly1305_encrypt_sg_inplace(sg, plaintext_len, NULL, 0,
217 PACKET_CB(skb)->nonce,
218 keypair->sending.key);
219}
220
221void wg_packet_send_keepalive(struct wg_peer *peer)
222{
223 struct sk_buff *skb;
224
225 if (skb_queue_empty_lockless(&peer->staged_packet_queue)) {
226 skb = alloc_skb(DATA_PACKET_HEAD_ROOM + MESSAGE_MINIMUM_LENGTH,
227 GFP_ATOMIC);
228 if (unlikely(!skb))
229 return;
230 skb_reserve(skb, DATA_PACKET_HEAD_ROOM);
231 skb->dev = peer->device->dev;
232 PACKET_CB(skb)->mtu = skb->dev->mtu;
233 skb_queue_tail(&peer->staged_packet_queue, skb);
234 net_dbg_ratelimited("%s: Sending keepalive packet to peer %llu (%pISpfsc)\n",
235 peer->device->dev->name, peer->internal_id,
236 &peer->endpoint.addr);
237 }
238
239 wg_packet_send_staged_packets(peer);
240}
241
242static void wg_packet_create_data_done(struct wg_peer *peer, struct sk_buff *first)
243{
244 struct sk_buff *skb, *next;
245 bool is_keepalive, data_sent = false;
246
247 wg_timers_any_authenticated_packet_traversal(peer);
248 wg_timers_any_authenticated_packet_sent(peer);
249 skb_list_walk_safe(first, skb, next) {
250 is_keepalive = skb->len == message_data_len(0);
251 if (likely(!wg_socket_send_skb_to_peer(peer, skb,
252 PACKET_CB(skb)->ds) && !is_keepalive))
253 data_sent = true;
254 }
255
256 if (likely(data_sent))
257 wg_timers_data_sent(peer);
258
259 keep_key_fresh(peer);
260}
261
262void wg_packet_tx_worker(struct work_struct *work)
263{
264 struct wg_peer *peer = container_of(work, struct wg_peer, transmit_packet_work);
265 struct noise_keypair *keypair;
266 enum packet_state state;
267 struct sk_buff *first;
268
269 while ((first = wg_prev_queue_peek(&peer->tx_queue)) != NULL &&
270 (state = atomic_read_acquire(&PACKET_CB(first)->state)) !=
271 PACKET_STATE_UNCRYPTED) {
272 wg_prev_queue_drop_peeked(&peer->tx_queue);
273 keypair = PACKET_CB(first)->keypair;
274
275 if (likely(state == PACKET_STATE_CRYPTED))
276 wg_packet_create_data_done(peer, first);
277 else
278 kfree_skb_list(first);
279
280 wg_noise_keypair_put(keypair, false);
281 wg_peer_put(peer);
282 if (need_resched())
283 cond_resched();
284 }
285}
286
287void wg_packet_encrypt_worker(struct work_struct *work)
288{
289 struct crypt_queue *queue = container_of(work, struct multicore_worker,
290 work)->ptr;
291 struct sk_buff *first, *skb, *next;
292
293 while ((first = ptr_ring_consume_bh(&queue->ring)) != NULL) {
294 enum packet_state state = PACKET_STATE_CRYPTED;
295
296 skb_list_walk_safe(first, skb, next) {
297 if (likely(encrypt_packet(skb,
298 PACKET_CB(first)->keypair))) {
299 wg_reset_packet(skb, true);
300 } else {
301 state = PACKET_STATE_DEAD;
302 break;
303 }
304 }
305 wg_queue_enqueue_per_peer_tx(first, state);
306 if (need_resched())
307 cond_resched();
308 }
309}
310
311static void wg_packet_create_data(struct wg_peer *peer, struct sk_buff *first)
312{
313 struct wg_device *wg = peer->device;
314 int ret = -EINVAL;
315
316 rcu_read_lock_bh();
317 if (unlikely(READ_ONCE(peer->is_dead)))
318 goto err;
319
320 ret = wg_queue_enqueue_per_device_and_peer(&wg->encrypt_queue, &peer->tx_queue, first,
321 wg->packet_crypt_wq);
322 if (unlikely(ret == -EPIPE))
323 wg_queue_enqueue_per_peer_tx(first, PACKET_STATE_DEAD);
324err:
325 rcu_read_unlock_bh();
326 if (likely(!ret || ret == -EPIPE))
327 return;
328 wg_noise_keypair_put(PACKET_CB(first)->keypair, false);
329 wg_peer_put(peer);
330 kfree_skb_list(first);
331}
332
333void wg_packet_purge_staged_packets(struct wg_peer *peer)
334{
335 spin_lock_bh(&peer->staged_packet_queue.lock);
336 DEV_STATS_ADD(peer->device->dev, tx_dropped,
337 peer->staged_packet_queue.qlen);
338 __skb_queue_purge(&peer->staged_packet_queue);
339 spin_unlock_bh(&peer->staged_packet_queue.lock);
340}
341
342void wg_packet_send_staged_packets(struct wg_peer *peer)
343{
344 struct noise_keypair *keypair;
345 struct sk_buff_head packets;
346 struct sk_buff *skb;
347
348 /* Steal the current queue into our local one. */
349 __skb_queue_head_init(&packets);
350 spin_lock_bh(&peer->staged_packet_queue.lock);
351 skb_queue_splice_init(&peer->staged_packet_queue, &packets);
352 spin_unlock_bh(&peer->staged_packet_queue.lock);
353 if (unlikely(skb_queue_empty(&packets)))
354 return;
355
356 /* First we make sure we have a valid reference to a valid key. */
357 rcu_read_lock_bh();
358 keypair = wg_noise_keypair_get(
359 rcu_dereference_bh(peer->keypairs.current_keypair));
360 rcu_read_unlock_bh();
361 if (unlikely(!keypair))
362 goto out_nokey;
363 if (unlikely(!READ_ONCE(keypair->sending.is_valid)))
364 goto out_nokey;
365 if (unlikely(wg_birthdate_has_expired(keypair->sending.birthdate,
366 REJECT_AFTER_TIME)))
367 goto out_invalid;
368
369 /* After we know we have a somewhat valid key, we now try to assign
370 * nonces to all of the packets in the queue. If we can't assign nonces
371 * for all of them, we just consider it a failure and wait for the next
372 * handshake.
373 */
374 skb_queue_walk(&packets, skb) {
375 /* 0 for no outer TOS: no leak. TODO: at some later point, we
376 * might consider using flowi->tos as outer instead.
377 */
378 PACKET_CB(skb)->ds = ip_tunnel_ecn_encap(0, ip_hdr(skb), skb);
379 PACKET_CB(skb)->nonce =
380 atomic64_inc_return(&keypair->sending_counter) - 1;
381 if (unlikely(PACKET_CB(skb)->nonce >= REJECT_AFTER_MESSAGES))
382 goto out_invalid;
383 }
384
385 packets.prev->next = NULL;
386 wg_peer_get(keypair->entry.peer);
387 PACKET_CB(packets.next)->keypair = keypair;
388 wg_packet_create_data(peer, packets.next);
389 return;
390
391out_invalid:
392 WRITE_ONCE(keypair->sending.is_valid, false);
393out_nokey:
394 wg_noise_keypair_put(keypair, false);
395
396 /* We orphan the packets if we're waiting on a handshake, so that they
397 * don't block a socket's pool.
398 */
399 skb_queue_walk(&packets, skb)
400 skb_orphan(skb);
401 /* Then we put them back on the top of the queue. We're not too
402 * concerned about accidentally getting things a little out of order if
403 * packets are being added really fast, because this queue is for before
404 * packets can even be sent and it's small anyway.
405 */
406 spin_lock_bh(&peer->staged_packet_queue.lock);
407 skb_queue_splice(&packets, &peer->staged_packet_queue);
408 spin_unlock_bh(&peer->staged_packet_queue.lock);
409
410 /* If we're exiting because there's something wrong with the key, it
411 * means we should initiate a new handshake.
412 */
413 wg_packet_send_queued_handshake_initiation(peer, false);
414}