// 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; int ret = -ENOMEM; lockdep_assert_held(&wg->device_update_lock); if (wg->num_peers >= MAX_PEERS_PER_DEVICE) return ERR_PTR(ret); peer = kzalloc(sizeof(*peer), GFP_KERNEL); if (unlikely(!peer)) return ERR_PTR(ret); if (dst_cache_init(&peer->endpoint_cache, GFP_KERNEL)) goto err; peer->device = wg; wg_noise_handshake_init(&peer->handshake, &wg->static_identity, public_key, preshared_key, peer); 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); INIT_WORK(&peer->transmit_packet_work, wg_packet_tx_worker); wg_prev_queue_init(&peer->tx_queue); wg_prev_queue_init(&peer->rx_queue); rwlock_init(&peer->endpoint_lock); kref_init(&peer->refcount); skb_queue_head_init(&peer->staged_packet_queue); wg_noise_reset_last_sent_handshake(&peer->last_sent_handshake); 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: kfree(peer); return ERR_PTR(ret); } 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 wg_peer *peer, *temp; LIST_HEAD(dead_peers); 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); WARN_ON(wg_prev_queue_peek(&peer->tx_queue) || wg_prev_queue_peek(&peer->rx_queue)); /* The final zeroing takes care of clearing any remaining handshake key * material and other potentially sensitive information. */ kfree_sensitive(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); }