![Jason A. Donenfeld](/assets/img/avatar_default.png)
We precompute the static-static ECDH during configuration time, in order to save an expensive computation later when receiving network packets. However, not all ECDH computations yield a contributory result. Prior, we were just not letting those peers be added to the interface. However, this creates a strange inconsistency, since it was still possible to add other weird points, like a valid public key plus a low-order point, and, like points that result in zeros, a handshake would not complete. In order to make the behavior more uniform and less surprising, simply allow all peers to be added. Then, we'll error out later when doing the crypto if there's an issue. This also adds more separation between the crypto layer and the configuration layer. Discussed-with: Mathias Hall-Andersen <mathias@hall-andersen.dk> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: David S. Miller <davem@davemloft.net>
238 lines
7.4 KiB
C
238 lines
7.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
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*/
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#include "peer.h"
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#include "device.h"
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#include "queueing.h"
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#include "timers.h"
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#include "peerlookup.h"
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#include "noise.h"
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#include <linux/kref.h>
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#include <linux/lockdep.h>
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#include <linux/rcupdate.h>
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#include <linux/list.h>
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static atomic64_t peer_counter = ATOMIC64_INIT(0);
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struct wg_peer *wg_peer_create(struct wg_device *wg,
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const u8 public_key[NOISE_PUBLIC_KEY_LEN],
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const u8 preshared_key[NOISE_SYMMETRIC_KEY_LEN])
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{
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struct wg_peer *peer;
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int ret = -ENOMEM;
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lockdep_assert_held(&wg->device_update_lock);
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if (wg->num_peers >= MAX_PEERS_PER_DEVICE)
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return ERR_PTR(ret);
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peer = kzalloc(sizeof(*peer), GFP_KERNEL);
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if (unlikely(!peer))
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return ERR_PTR(ret);
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peer->device = wg;
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wg_noise_handshake_init(&peer->handshake, &wg->static_identity,
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public_key, preshared_key, peer);
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if (dst_cache_init(&peer->endpoint_cache, GFP_KERNEL))
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goto err_1;
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if (wg_packet_queue_init(&peer->tx_queue, wg_packet_tx_worker, false,
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MAX_QUEUED_PACKETS))
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goto err_2;
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if (wg_packet_queue_init(&peer->rx_queue, NULL, false,
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MAX_QUEUED_PACKETS))
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goto err_3;
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peer->internal_id = atomic64_inc_return(&peer_counter);
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peer->serial_work_cpu = nr_cpumask_bits;
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wg_cookie_init(&peer->latest_cookie);
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wg_timers_init(peer);
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wg_cookie_checker_precompute_peer_keys(peer);
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spin_lock_init(&peer->keypairs.keypair_update_lock);
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INIT_WORK(&peer->transmit_handshake_work,
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wg_packet_handshake_send_worker);
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rwlock_init(&peer->endpoint_lock);
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kref_init(&peer->refcount);
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skb_queue_head_init(&peer->staged_packet_queue);
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wg_noise_reset_last_sent_handshake(&peer->last_sent_handshake);
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set_bit(NAPI_STATE_NO_BUSY_POLL, &peer->napi.state);
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netif_napi_add(wg->dev, &peer->napi, wg_packet_rx_poll,
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NAPI_POLL_WEIGHT);
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napi_enable(&peer->napi);
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list_add_tail(&peer->peer_list, &wg->peer_list);
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INIT_LIST_HEAD(&peer->allowedips_list);
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wg_pubkey_hashtable_add(wg->peer_hashtable, peer);
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++wg->num_peers;
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pr_debug("%s: Peer %llu created\n", wg->dev->name, peer->internal_id);
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return peer;
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err_3:
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wg_packet_queue_free(&peer->tx_queue, false);
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err_2:
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dst_cache_destroy(&peer->endpoint_cache);
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err_1:
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kfree(peer);
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return ERR_PTR(ret);
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}
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struct wg_peer *wg_peer_get_maybe_zero(struct wg_peer *peer)
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{
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RCU_LOCKDEP_WARN(!rcu_read_lock_bh_held(),
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"Taking peer reference without holding the RCU read lock");
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if (unlikely(!peer || !kref_get_unless_zero(&peer->refcount)))
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return NULL;
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return peer;
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}
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static void peer_make_dead(struct wg_peer *peer)
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{
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/* Remove from configuration-time lookup structures. */
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list_del_init(&peer->peer_list);
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wg_allowedips_remove_by_peer(&peer->device->peer_allowedips, peer,
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&peer->device->device_update_lock);
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wg_pubkey_hashtable_remove(peer->device->peer_hashtable, peer);
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/* Mark as dead, so that we don't allow jumping contexts after. */
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WRITE_ONCE(peer->is_dead, true);
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/* The caller must now synchronize_rcu() for this to take effect. */
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}
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static void peer_remove_after_dead(struct wg_peer *peer)
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{
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WARN_ON(!peer->is_dead);
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/* No more keypairs can be created for this peer, since is_dead protects
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* add_new_keypair, so we can now destroy existing ones.
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*/
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wg_noise_keypairs_clear(&peer->keypairs);
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/* Destroy all ongoing timers that were in-flight at the beginning of
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* this function.
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*/
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wg_timers_stop(peer);
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/* The transition between packet encryption/decryption queues isn't
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* guarded by is_dead, but each reference's life is strictly bounded by
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* two generations: once for parallel crypto and once for serial
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* ingestion, so we can simply flush twice, and be sure that we no
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* longer have references inside these queues.
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*/
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/* a) For encrypt/decrypt. */
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flush_workqueue(peer->device->packet_crypt_wq);
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/* b.1) For send (but not receive, since that's napi). */
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flush_workqueue(peer->device->packet_crypt_wq);
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/* b.2.1) For receive (but not send, since that's wq). */
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napi_disable(&peer->napi);
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/* b.2.1) It's now safe to remove the napi struct, which must be done
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* here from process context.
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*/
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netif_napi_del(&peer->napi);
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/* Ensure any workstructs we own (like transmit_handshake_work or
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* clear_peer_work) no longer are in use.
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*/
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flush_workqueue(peer->device->handshake_send_wq);
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/* After the above flushes, a peer might still be active in a few
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* different contexts: 1) from xmit(), before hitting is_dead and
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* returning, 2) from wg_packet_consume_data(), before hitting is_dead
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* and returning, 3) from wg_receive_handshake_packet() after a point
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* where it has processed an incoming handshake packet, but where
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* all calls to pass it off to timers fails because of is_dead. We won't
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* have new references in (1) eventually, because we're removed from
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* allowedips; we won't have new references in (2) eventually, because
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* wg_index_hashtable_lookup will always return NULL, since we removed
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* all existing keypairs and no more can be created; we won't have new
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* references in (3) eventually, because we're removed from the pubkey
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* hash table, which allows for a maximum of one handshake response,
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* via the still-uncleared index hashtable entry, but not more than one,
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* and in wg_cookie_message_consume, the lookup eventually gets a peer
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* with a refcount of zero, so no new reference is taken.
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*/
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--peer->device->num_peers;
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wg_peer_put(peer);
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}
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/* We have a separate "remove" function make sure that all active places where
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* a peer is currently operating will eventually come to an end and not pass
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* their reference onto another context.
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*/
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void wg_peer_remove(struct wg_peer *peer)
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{
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if (unlikely(!peer))
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return;
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lockdep_assert_held(&peer->device->device_update_lock);
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peer_make_dead(peer);
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synchronize_rcu();
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peer_remove_after_dead(peer);
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}
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void wg_peer_remove_all(struct wg_device *wg)
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{
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struct wg_peer *peer, *temp;
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LIST_HEAD(dead_peers);
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lockdep_assert_held(&wg->device_update_lock);
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/* Avoid having to traverse individually for each one. */
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wg_allowedips_free(&wg->peer_allowedips, &wg->device_update_lock);
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list_for_each_entry_safe(peer, temp, &wg->peer_list, peer_list) {
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peer_make_dead(peer);
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list_add_tail(&peer->peer_list, &dead_peers);
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}
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synchronize_rcu();
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list_for_each_entry_safe(peer, temp, &dead_peers, peer_list)
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peer_remove_after_dead(peer);
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}
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static void rcu_release(struct rcu_head *rcu)
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{
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struct wg_peer *peer = container_of(rcu, struct wg_peer, rcu);
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dst_cache_destroy(&peer->endpoint_cache);
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wg_packet_queue_free(&peer->rx_queue, false);
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wg_packet_queue_free(&peer->tx_queue, false);
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/* The final zeroing takes care of clearing any remaining handshake key
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* material and other potentially sensitive information.
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*/
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kzfree(peer);
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}
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static void kref_release(struct kref *refcount)
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{
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struct wg_peer *peer = container_of(refcount, struct wg_peer, refcount);
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pr_debug("%s: Peer %llu (%pISpfsc) destroyed\n",
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peer->device->dev->name, peer->internal_id,
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&peer->endpoint.addr);
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/* Remove ourself from dynamic runtime lookup structures, now that the
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* last reference is gone.
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*/
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wg_index_hashtable_remove(peer->device->index_hashtable,
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&peer->handshake.entry);
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/* Remove any lingering packets that didn't have a chance to be
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* transmitted.
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*/
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wg_packet_purge_staged_packets(peer);
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/* Free the memory used. */
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call_rcu(&peer->rcu, rcu_release);
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}
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void wg_peer_put(struct wg_peer *peer)
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{
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if (unlikely(!peer))
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return;
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kref_put(&peer->refcount, kref_release);
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}
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