drivers/net/wireguard/peer.c

   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
  18 static atomic64_t peer_counter = ATOMIC64_INIT(0);
  19
  20 struct wg_peer *wg_peer_create(struct wg_device *wg,
  21                                const u8 public_key[NOISE_PUBLIC_KEY_LEN],
  22                                const u8 preshared_key[NOISE_SYMMETRIC_KEY_LEN])
  23 {
  24         struct wg_peer *peer;
  25         int ret = -ENOMEM;
  26
  27         lockdep_assert_held(&wg->device_update_lock);
  28
  29         if (wg->num_peers >= MAX_PEERS_PER_DEVICE)
  30                 return ERR_PTR(ret);
  31
  32         peer = kzalloc(sizeof(*peer), GFP_KERNEL);
  33         if (unlikely(!peer))
  34                 return ERR_PTR(ret);
  35         peer->device = wg;
  36
  37         wg_noise_handshake_init(&peer->handshake, &wg->static_identity,
  38                                 public_key, preshared_key, peer);
  39         if (dst_cache_init(&peer->endpoint_cache, GFP_KERNEL))
  40                 goto err_1;
  41         if (wg_packet_queue_init(&peer->tx_queue, wg_packet_tx_worker, false,
  42                                  MAX_QUEUED_PACKETS))
  43                 goto err_2;
  44         if (wg_packet_queue_init(&peer->rx_queue, NULL, false,
  45                                  MAX_QUEUED_PACKETS))
  46                 goto err_3;
  47
  48         peer->internal_id = atomic64_inc_return(&peer_counter);
  49         peer->serial_work_cpu = nr_cpumask_bits;
  50         wg_cookie_init(&peer->latest_cookie);
  51         wg_timers_init(peer);
  52         wg_cookie_checker_precompute_peer_keys(peer);
  53         spin_lock_init(&peer->keypairs.keypair_update_lock);
  54         INIT_WORK(&peer->transmit_handshake_work,
  55                   wg_packet_handshake_send_worker);
  56         rwlock_init(&peer->endpoint_lock);
  57         kref_init(&peer->refcount);
  58         skb_queue_head_init(&peer->staged_packet_queue);
  59         wg_noise_reset_last_sent_handshake(&peer->last_sent_handshake);
  60         set_bit(NAPI_STATE_NO_BUSY_POLL, &peer->napi.state);
  61         netif_napi_add(wg->dev, &peer->napi, wg_packet_rx_poll,
  62                        NAPI_POLL_WEIGHT);
  63         napi_enable(&peer->napi);
  64         list_add_tail(&peer->peer_list, &wg->peer_list);
  65         INIT_LIST_HEAD(&peer->allowedips_list);
  66         wg_pubkey_hashtable_add(wg->peer_hashtable, peer);
  67         ++wg->num_peers;
  68         pr_debug("%s: Peer %llu created\n", wg->dev->name, peer->internal_id);
  69         return peer;
  70
  71 err_3:
  72         wg_packet_queue_free(&peer->tx_queue, false);
  73 err_2:
  74         dst_cache_destroy(&peer->endpoint_cache);
  75 err_1:
  76         kfree(peer);
  77         return ERR_PTR(ret);
  78 }
  79
  80 struct wg_peer *wg_peer_get_maybe_zero(struct wg_peer *peer)
  81 {
  82         RCU_LOCKDEP_WARN(!rcu_read_lock_bh_held(),
  83                          "Taking peer reference without holding the RCU read lock");
  84         if (unlikely(!peer || !kref_get_unless_zero(&peer->refcount)))
  85                 return NULL;
  86         return peer;
  87 }
  88
  89 static void peer_make_dead(struct wg_peer *peer)
  90 {
  91         /* Remove from configuration-time lookup structures. */
  92         list_del_init(&peer->peer_list);
  93         wg_allowedips_remove_by_peer(&peer->device->peer_allowedips, peer,
  94                                      &peer->device->device_update_lock);
  95         wg_pubkey_hashtable_remove(peer->device->peer_hashtable, peer);
  96
  97         /* Mark as dead, so that we don't allow jumping contexts after. */
  98         WRITE_ONCE(peer->is_dead, true);
  99
 100         /* The caller must now synchronize_rcu() for this to take effect. */
 101 }
 102
 103 static void peer_remove_after_dead(struct wg_peer *peer)
 104 {
 105         WARN_ON(!peer->is_dead);
 106
 107         /* No more keypairs can be created for this peer, since is_dead protects
 108          * add_new_keypair, so we can now destroy existing ones.
 109          */
 110         wg_noise_keypairs_clear(&peer->keypairs);
 111
 112         /* Destroy all ongoing timers that were in-flight at the beginning of
 113          * this function.
 114          */
 115         wg_timers_stop(peer);
 116
 117         /* The transition between packet encryption/decryption queues isn't
 118          * guarded by is_dead, but each reference's life is strictly bounded by
 119          * two generations: once for parallel crypto and once for serial
 120          * ingestion, so we can simply flush twice, and be sure that we no
 121          * longer have references inside these queues.
 122          */
 123
 124         /* a) For encrypt/decrypt. */
 125         flush_workqueue(peer->device->packet_crypt_wq);
 126         /* b.1) For send (but not receive, since that's napi). */
 127         flush_workqueue(peer->device->packet_crypt_wq);
 128         /* b.2.1) For receive (but not send, since that's wq). */
 129         napi_disable(&peer->napi);
 130         /* b.2.1) It's now safe to remove the napi struct, which must be done
 131          * here from process context.
 132          */
 133         netif_napi_del(&peer->napi);
 134
 135         /* Ensure any workstructs we own (like transmit_handshake_work or
 136          * clear_peer_work) no longer are in use.
 137          */
 138         flush_workqueue(peer->device->handshake_send_wq);
 139
 140         /* After the above flushes, a peer might still be active in a few
 141          * different contexts: 1) from xmit(), before hitting is_dead and
 142          * returning, 2) from wg_packet_consume_data(), before hitting is_dead
 143          * and returning, 3) from wg_receive_handshake_packet() after a point
 144          * where it has processed an incoming handshake packet, but where
 145          * all calls to pass it off to timers fails because of is_dead. We won't
 146          * have new references in (1) eventually, because we're removed from
 147          * allowedips; we won't have new references in (2) eventually, because
 148          * wg_index_hashtable_lookup will always return NULL, since we removed
 149          * all existing keypairs and no more can be created; we won't have new
 150          * references in (3) eventually, because we're removed from the pubkey
 151          * hash table, which allows for a maximum of one handshake response,
 152          * via the still-uncleared index hashtable entry, but not more than one,
 153          * and in wg_cookie_message_consume, the lookup eventually gets a peer
 154          * with a refcount of zero, so no new reference is taken.
 155          */
 156
 157         --peer->device->num_peers;
 158         wg_peer_put(peer);
 159 }
 160
 161 /* We have a separate "remove" function make sure that all active places where
 162  * a peer is currently operating will eventually come to an end and not pass
 163  * their reference onto another context.
 164  */
 165 void wg_peer_remove(struct wg_peer *peer)
 166 {
 167         if (unlikely(!peer))
 168                 return;
 169         lockdep_assert_held(&peer->device->device_update_lock);
 170
 171         peer_make_dead(peer);
 172         synchronize_rcu();
 173         peer_remove_after_dead(peer);
 174 }
 175
 176 void wg_peer_remove_all(struct wg_device *wg)
 177 {
 178         struct wg_peer *peer, *temp;
 179         LIST_HEAD(dead_peers);
 180
 181         lockdep_assert_held(&wg->device_update_lock);
 182
 183         /* Avoid having to traverse individually for each one. */
 184         wg_allowedips_free(&wg->peer_allowedips, &wg->device_update_lock);
 185
 186         list_for_each_entry_safe(peer, temp, &wg->peer_list, peer_list) {
 187                 peer_make_dead(peer);
 188                 list_add_tail(&peer->peer_list, &dead_peers);
 189         }
 190         synchronize_rcu();
 191         list_for_each_entry_safe(peer, temp, &dead_peers, peer_list)
 192                 peer_remove_after_dead(peer);
 193 }
 194
 195 static void rcu_release(struct rcu_head *rcu)
 196 {
 197         struct wg_peer *peer = container_of(rcu, struct wg_peer, rcu);
 198
 199         dst_cache_destroy(&peer->endpoint_cache);
 200         wg_packet_queue_free(&peer->rx_queue, false);
 201         wg_packet_queue_free(&peer->tx_queue, false);
 202
 203         /* The final zeroing takes care of clearing any remaining handshake key
 204          * material and other potentially sensitive information.
 205          */
 206         kfree_sensitive(peer);
 207 }
 208
 209 static void kref_release(struct kref *refcount)
 210 {
 211         struct wg_peer *peer = container_of(refcount, struct wg_peer, refcount);
 212
 213         pr_debug("%s: Peer %llu (%pISpfsc) destroyed\n",
 214                  peer->device->dev->name, peer->internal_id,
 215                  &peer->endpoint.addr);
 216
 217         /* Remove ourself from dynamic runtime lookup structures, now that the
 218          * last reference is gone.
 219          */
 220         wg_index_hashtable_remove(peer->device->index_hashtable,
 221                                   &peer->handshake.entry);
 222
 223         /* Remove any lingering packets that didn't have a chance to be
 224          * transmitted.
 225          */
 226         wg_packet_purge_staged_packets(peer);
 227
 228         /* Free the memory used. */
 229         call_rcu(&peer->rcu, rcu_release);
 230 }
 231
 232 void wg_peer_put(struct wg_peer *peer)
 233 {
 234         if (unlikely(!peer))
 235                 return;
 236         kref_put(&peer->refcount, kref_release);
 237 }