aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/net/wireguard/peer.c
blob: 508f1d5b44446e37e6935d3568bde51d69851aa2 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
 */

#include "peer.h"
#include "device.h"
#include "queueing.h"
#include "timers.h"
#include "peerlookup.h"
#include "noise.h"

#include <linux/kref.h>
#include <linux/lockdep.h>
#include <linux/rcupdate.h>
#include <linux/list.h>

static atomic64_t peer_counter = ATOMIC64_INIT(0);

struct wg_peer *wg_peer_create(struct wg_device *wg,
			       const u8 public_key[NOISE_PUBLIC_KEY_LEN],
			       const u8 preshared_key[NOISE_SYMMETRIC_KEY_LEN])
{
	struct wg_peer *peer;

	lockdep_assert_held(&wg->device_update_lock);

	if (wg->num_peers >= MAX_PEERS_PER_DEVICE)
		return NULL;

	peer = kzalloc(sizeof(*peer), GFP_KERNEL);
	if (unlikely(!peer))
		return NULL;
	peer->device = wg;

	if (!wg_noise_handshake_init(&peer->handshake, &wg->static_identity,
				     public_key, preshared_key, peer))
		goto err_1;
	if (dst_cache_init(&peer->endpoint_cache, GFP_KERNEL))
		goto err_1;
	if (wg_packet_queue_init(&peer->tx_queue, wg_packet_tx_worker, false,
				 MAX_QUEUED_PACKETS))
		goto err_2;
	if (wg_packet_queue_init(&peer->rx_queue, NULL, false,
				 MAX_QUEUED_PACKETS))
		goto err_3;

	peer->internal_id = atomic64_inc_return(&peer_counter);
	peer->serial_work_cpu = nr_cpumask_bits;
	wg_cookie_init(&peer->latest_cookie);
	wg_timers_init(peer);
	wg_cookie_checker_precompute_peer_keys(peer);
	spin_lock_init(&peer->keypairs.keypair_update_lock);
	INIT_WORK(&peer->transmit_handshake_work,
		  wg_packet_handshake_send_worker);
	rwlock_init(&peer->endpoint_lock);
	kref_init(&peer->refcount);
	skb_queue_head_init(&peer->staged_packet_queue);
	atomic64_set(&peer->last_sent_handshake,
		     ktime_get_boot_fast_ns() -
			     (u64)(REKEY_TIMEOUT + 1) * NSEC_PER_SEC);
	set_bit(NAPI_STATE_NO_BUSY_POLL, &peer->napi.state);
	netif_napi_add(wg->dev, &peer->napi, wg_packet_rx_poll,
		       NAPI_POLL_WEIGHT);
	napi_enable(&peer->napi);
	list_add_tail(&peer->peer_list, &wg->peer_list);
	INIT_LIST_HEAD(&peer->allowedips_list);
	wg_pubkey_hashtable_add(wg->peer_hashtable, peer);
	++wg->num_peers;
	pr_debug("%s: Peer %llu created\n", wg->dev->name, peer->internal_id);
	return peer;

err_3:
	wg_packet_queue_free(&peer->tx_queue, false);
err_2:
	dst_cache_destroy(&peer->endpoint_cache);
err_1:
	kfree(peer);
	return NULL;
}

struct wg_peer *wg_peer_get_maybe_zero(struct wg_peer *peer)
{
	RCU_LOCKDEP_WARN(!rcu_read_lock_bh_held(),
			 "Taking peer reference without holding the RCU read lock");
	if (unlikely(!peer || !kref_get_unless_zero(&peer->refcount)))
		return NULL;
	return peer;
}

static void peer_make_dead(struct wg_peer *peer)
{
	/* Remove from configuration-time lookup structures. */
	list_del_init(&peer->peer_list);
	wg_allowedips_remove_by_peer(&peer->device->peer_allowedips, peer,
				     &peer->device->device_update_lock);
	wg_pubkey_hashtable_remove(peer->device->peer_hashtable, peer);

	/* Mark as dead, so that we don't allow jumping contexts after. */
	WRITE_ONCE(peer->is_dead, true);

	/* The caller must now synchronize_rcu() for this to take effect. */
}

static void peer_remove_after_dead(struct wg_peer *peer)
{
	WARN_ON(!peer->is_dead);

	/* No more keypairs can be created for this peer, since is_dead protects
	 * add_new_keypair, so we can now destroy existing ones.
	 */
	wg_noise_keypairs_clear(&peer->keypairs);

	/* Destroy all ongoing timers that were in-flight at the beginning of
	 * this function.
	 */
	wg_timers_stop(peer);

	/* The transition between packet encryption/decryption queues isn't
	 * guarded by is_dead, but each reference's life is strictly bounded by
	 * two generations: once for parallel crypto and once for serial
	 * ingestion, so we can simply flush twice, and be sure that we no
	 * longer have references inside these queues.
	 */

	/* a) For encrypt/decrypt. */
	flush_workqueue(peer->device->packet_crypt_wq);
	/* b.1) For send (but not receive, since that's napi). */
	flush_workqueue(peer->device->packet_crypt_wq);
	/* b.2.1) For receive (but not send, since that's wq). */
	napi_disable(&peer->napi);
	/* b.2.1) It's now safe to remove the napi struct, which must be done
	 * here from process context.
	 */
	netif_napi_del(&peer->napi);

	/* Ensure any workstructs we own (like transmit_handshake_work or
	 * clear_peer_work) no longer are in use.
	 */
	flush_workqueue(peer->device->handshake_send_wq);

	/* After the above flushes, a peer might still be active in a few
	 * different contexts: 1) from xmit(), before hitting is_dead and
	 * returning, 2) from wg_packet_consume_data(), before hitting is_dead
	 * and returning, 3) from wg_receive_handshake_packet() after a point
	 * where it has processed an incoming handshake packet, but where
	 * all calls to pass it off to timers fails because of is_dead. We won't
	 * have new references in (1) eventually, because we're removed from
	 * allowedips; we won't have new references in (2) eventually, because
	 * wg_index_hashtable_lookup will always return NULL, since we removed
	 * all existing keypairs and no more can be created; we won't have new
	 * references in (3) eventually, because we're removed from the pubkey
	 * hash table, which allows for a maximum of one handshake response,
	 * via the still-uncleared index hashtable entry, but not more than one,
	 * and in wg_cookie_message_consume, the lookup eventually gets a peer
	 * with a refcount of zero, so no new reference is taken.
	 */

	--peer->device->num_peers;
	wg_peer_put(peer);
}

/* We have a separate "remove" function make sure that all active places where
 * a peer is currently operating will eventually come to an end and not pass
 * their reference onto another context.
 */
void wg_peer_remove(struct wg_peer *peer)
{
	if (unlikely(!peer))
		return;
	lockdep_assert_held(&peer->device->device_update_lock);

	peer_make_dead(peer);
	synchronize_rcu();
	peer_remove_after_dead(peer);
}

void wg_peer_remove_all(struct wg_device *wg)
{
	struct list_head dead_peers = LIST_HEAD_INIT(dead_peers);
	struct wg_peer *peer, *temp;

	lockdep_assert_held(&wg->device_update_lock);

	/* Avoid having to traverse individually for each one. */
	wg_allowedips_free(&wg->peer_allowedips, &wg->device_update_lock);

	list_for_each_entry_safe(peer, temp, &wg->peer_list, peer_list) {
		peer_make_dead(peer);
		list_add_tail(&peer->peer_list, &dead_peers);
	}
	synchronize_rcu();
	list_for_each_entry_safe(peer, temp, &dead_peers, peer_list)
		peer_remove_after_dead(peer);
}

static void rcu_release(struct rcu_head *rcu)
{
	struct wg_peer *peer = container_of(rcu, struct wg_peer, rcu);

	dst_cache_destroy(&peer->endpoint_cache);
	wg_packet_queue_free(&peer->rx_queue, false);
	wg_packet_queue_free(&peer->tx_queue, false);

	/* The final zeroing takes care of clearing any remaining handshake key
	 * material and other potentially sensitive information.
	 */
	kzfree(peer);
}

static void kref_release(struct kref *refcount)
{
	struct wg_peer *peer = container_of(refcount, struct wg_peer, refcount);

	pr_debug("%s: Peer %llu (%pISpfsc) destroyed\n",
		 peer->device->dev->name, peer->internal_id,
		 &peer->endpoint.addr);

	/* Remove ourself from dynamic runtime lookup structures, now that the
	 * last reference is gone.
	 */
	wg_index_hashtable_remove(peer->device->index_hashtable,
				  &peer->handshake.entry);

	/* Remove any lingering packets that didn't have a chance to be
	 * transmitted.
	 */
	wg_packet_purge_staged_packets(peer);

	/* Free the memory used. */
	call_rcu(&peer->rcu, rcu_release);
}

void wg_peer_put(struct wg_peer *peer)
{
	if (unlikely(!peer))
		return;
	kref_put(&peer->refcount, kref_release);
}