1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
  4 */
  5
  6#include "peer.h"
  7#include "device.h"
  8#include "queueing.h"
  9#include "timers.h"
 10#include "peerlookup.h"
 11#include "noise.h"
 12
 13#include <linux/kref.h>
 14#include <linux/lockdep.h>
 15#include <linux/rcupdate.h>
 16#include <linux/list.h>
 17
 18static struct kmem_cache *peer_cache;
 19static atomic64_t peer_counter = ATOMIC64_INIT(0);
 20
 21struct wg_peer *wg_peer_create(struct wg_device *wg,
 22			       const u8 public_key[NOISE_PUBLIC_KEY_LEN],
 23			       const u8 preshared_key[NOISE_SYMMETRIC_KEY_LEN])
 24{
 25	struct wg_peer *peer;
 26	int ret = -ENOMEM;
 27
 28	lockdep_assert_held(&wg->device_update_lock);
 29
 30	if (wg->num_peers >= MAX_PEERS_PER_DEVICE)
 31		return ERR_PTR(ret);
 32
 33	peer = kmem_cache_zalloc(peer_cache, GFP_KERNEL);
 34	if (unlikely(!peer))
 35		return ERR_PTR(ret);
 36	if (unlikely(dst_cache_init(&peer->endpoint_cache, GFP_KERNEL)))
 37		goto err;
 38
 39	peer->device = wg;
 40	wg_noise_handshake_init(&peer->handshake, &wg->static_identity,
 41				public_key, preshared_key, peer);
 42	peer->internal_id = atomic64_inc_return(&peer_counter);
 43	peer->serial_work_cpu = nr_cpumask_bits;
 44	wg_cookie_init(&peer->latest_cookie);
 45	wg_timers_init(peer);
 46	wg_cookie_checker_precompute_peer_keys(peer);
 47	spin_lock_init(&peer->keypairs.keypair_update_lock);
 48	INIT_WORK(&peer->transmit_handshake_work, wg_packet_handshake_send_worker);
 49	INIT_WORK(&peer->transmit_packet_work, wg_packet_tx_worker);
 50	wg_prev_queue_init(&peer->tx_queue);
 51	wg_prev_queue_init(&peer->rx_queue);
 52	rwlock_init(&peer->endpoint_lock);
 53	kref_init(&peer->refcount);
 54	skb_queue_head_init(&peer->staged_packet_queue);
 55	wg_noise_reset_last_sent_handshake(&peer->last_sent_handshake);
 56	set_bit(NAPI_STATE_NO_BUSY_POLL, &peer->napi.state);
 57	netif_napi_add(wg->dev, &peer->napi, wg_packet_rx_poll,
 58		       NAPI_POLL_WEIGHT);
 59	napi_enable(&peer->napi);
 60	list_add_tail(&peer->peer_list, &wg->peer_list);
 61	INIT_LIST_HEAD(&peer->allowedips_list);
 62	wg_pubkey_hashtable_add(wg->peer_hashtable, peer);
 63	++wg->num_peers;
 64	pr_debug("%s: Peer %llu created\n", wg->dev->name, peer->internal_id);
 65	return peer;
 66
 67err:
 68	kmem_cache_free(peer_cache, peer);
 69	return ERR_PTR(ret);
 70}
 71
 72struct wg_peer *wg_peer_get_maybe_zero(struct wg_peer *peer)
 73{
 74	RCU_LOCKDEP_WARN(!rcu_read_lock_bh_held(),
 75			 "Taking peer reference without holding the RCU read lock");
 76	if (unlikely(!peer || !kref_get_unless_zero(&peer->refcount)))
 77		return NULL;
 78	return peer;
 79}
 80
 81static void peer_make_dead(struct wg_peer *peer)
 82{
 83	/* Remove from configuration-time lookup structures. */
 84	list_del_init(&peer->peer_list);
 85	wg_allowedips_remove_by_peer(&peer->device->peer_allowedips, peer,
 86				     &peer->device->device_update_lock);
 87	wg_pubkey_hashtable_remove(peer->device->peer_hashtable, peer);
 88
 89	/* Mark as dead, so that we don't allow jumping contexts after. */
 90	WRITE_ONCE(peer->is_dead, true);
 91
 92	/* The caller must now synchronize_net() for this to take effect. */
 93}
 94
 95static void peer_remove_after_dead(struct wg_peer *peer)
 96{
 97	WARN_ON(!peer->is_dead);
 98
 99	/* No more keypairs can be created for this peer, since is_dead protects
100	 * add_new_keypair, so we can now destroy existing ones.
101	 */
102	wg_noise_keypairs_clear(&peer->keypairs);
103
104	/* Destroy all ongoing timers that were in-flight at the beginning of
105	 * this function.
106	 */
107	wg_timers_stop(peer);
108
109	/* The transition between packet encryption/decryption queues isn't
110	 * guarded by is_dead, but each reference's life is strictly bounded by
111	 * two generations: once for parallel crypto and once for serial
112	 * ingestion, so we can simply flush twice, and be sure that we no
113	 * longer have references inside these queues.
114	 */
115
116	/* a) For encrypt/decrypt. */
117	flush_workqueue(peer->device->packet_crypt_wq);
118	/* b.1) For send (but not receive, since that's napi). */
119	flush_workqueue(peer->device->packet_crypt_wq);
120	/* b.2.1) For receive (but not send, since that's wq). */
121	napi_disable(&peer->napi);
122	/* b.2.1) It's now safe to remove the napi struct, which must be done
123	 * here from process context.
124	 */
125	netif_napi_del(&peer->napi);
126
127	/* Ensure any workstructs we own (like transmit_handshake_work or
128	 * clear_peer_work) no longer are in use.
129	 */
130	flush_workqueue(peer->device->handshake_send_wq);
131
132	/* After the above flushes, a peer might still be active in a few
133	 * different contexts: 1) from xmit(), before hitting is_dead and
134	 * returning, 2) from wg_packet_consume_data(), before hitting is_dead
135	 * and returning, 3) from wg_receive_handshake_packet() after a point
136	 * where it has processed an incoming handshake packet, but where
137	 * all calls to pass it off to timers fails because of is_dead. We won't
138	 * have new references in (1) eventually, because we're removed from
139	 * allowedips; we won't have new references in (2) eventually, because
140	 * wg_index_hashtable_lookup will always return NULL, since we removed
141	 * all existing keypairs and no more can be created; we won't have new
142	 * references in (3) eventually, because we're removed from the pubkey
143	 * hash table, which allows for a maximum of one handshake response,
144	 * via the still-uncleared index hashtable entry, but not more than one,
145	 * and in wg_cookie_message_consume, the lookup eventually gets a peer
146	 * with a refcount of zero, so no new reference is taken.
147	 */
148
149	--peer->device->num_peers;
150	wg_peer_put(peer);
151}
152
153/* We have a separate "remove" function make sure that all active places where
154 * a peer is currently operating will eventually come to an end and not pass
155 * their reference onto another context.
156 */
157void wg_peer_remove(struct wg_peer *peer)
158{
159	if (unlikely(!peer))
160		return;
161	lockdep_assert_held(&peer->device->device_update_lock);
162
163	peer_make_dead(peer);
164	synchronize_net();
165	peer_remove_after_dead(peer);
166}
167
168void wg_peer_remove_all(struct wg_device *wg)
169{
170	struct wg_peer *peer, *temp;
171	LIST_HEAD(dead_peers);
172
173	lockdep_assert_held(&wg->device_update_lock);
174
175	/* Avoid having to traverse individually for each one. */
176	wg_allowedips_free(&wg->peer_allowedips, &wg->device_update_lock);
177
178	list_for_each_entry_safe(peer, temp, &wg->peer_list, peer_list) {
179		peer_make_dead(peer);
180		list_add_tail(&peer->peer_list, &dead_peers);
181	}
182	synchronize_net();
183	list_for_each_entry_safe(peer, temp, &dead_peers, peer_list)
184		peer_remove_after_dead(peer);
185}
186
187static void rcu_release(struct rcu_head *rcu)
188{
189	struct wg_peer *peer = container_of(rcu, struct wg_peer, rcu);
190
191	dst_cache_destroy(&peer->endpoint_cache);
192	WARN_ON(wg_prev_queue_peek(&peer->tx_queue) || wg_prev_queue_peek(&peer->rx_queue));
193
194	/* The final zeroing takes care of clearing any remaining handshake key
195	 * material and other potentially sensitive information.
196	 */
197	memzero_explicit(peer, sizeof(*peer));
198	kmem_cache_free(peer_cache, peer);
199}
200
201static void kref_release(struct kref *refcount)
202{
203	struct wg_peer *peer = container_of(refcount, struct wg_peer, refcount);
204
205	pr_debug("%s: Peer %llu (%pISpfsc) destroyed\n",
206		 peer->device->dev->name, peer->internal_id,
207		 &peer->endpoint.addr);
208
209	/* Remove ourself from dynamic runtime lookup structures, now that the
210	 * last reference is gone.
211	 */
212	wg_index_hashtable_remove(peer->device->index_hashtable,
213				  &peer->handshake.entry);
214
215	/* Remove any lingering packets that didn't have a chance to be
216	 * transmitted.
217	 */
218	wg_packet_purge_staged_packets(peer);
219
220	/* Free the memory used. */
221	call_rcu(&peer->rcu, rcu_release);
222}
223
224void wg_peer_put(struct wg_peer *peer)
225{
226	if (unlikely(!peer))
227		return;
228	kref_put(&peer->refcount, kref_release);
229}
230
231int __init wg_peer_init(void)
232{
233	peer_cache = KMEM_CACHE(wg_peer, 0);
234	return peer_cache ? 0 : -ENOMEM;
235}
236
237void wg_peer_uninit(void)
238{
239	kmem_cache_destroy(peer_cache);
240}