![Jason A. Donenfeld](/assets/img/avatar_default.png)
WireGuard is a layer 3 secure networking tunnel made specifically for the kernel, that aims to be much simpler and easier to audit than IPsec. Extensive documentation and description of the protocol and considerations, along with formal proofs of the cryptography, are available at: * https://www.wireguard.com/ * https://www.wireguard.com/papers/wireguard.pdf This commit implements WireGuard as a simple network device driver, accessible in the usual RTNL way used by virtual network drivers. It makes use of the udp_tunnel APIs, GRO, GSO, NAPI, and the usual set of networking subsystem APIs. It has a somewhat novel multicore queueing system designed for maximum throughput and minimal latency of encryption operations, but it is implemented modestly using workqueues and NAPI. Configuration is done via generic Netlink, and following a review from the Netlink maintainer a year ago, several high profile userspace tools have already implemented the API. This commit also comes with several different tests, both in-kernel tests and out-of-kernel tests based on network namespaces, taking profit of the fact that sockets used by WireGuard intentionally stay in the namespace the WireGuard interface was originally created, exactly like the semantics of userspace tun devices. See wireguard.com/netns/ for pictures and examples. The source code is fairly short, but rather than combining everything into a single file, WireGuard is developed as cleanly separable files, making auditing and comprehension easier. Things are laid out as follows: * noise.[ch], cookie.[ch], messages.h: These implement the bulk of the cryptographic aspects of the protocol, and are mostly data-only in nature, taking in buffers of bytes and spitting out buffers of bytes. They also handle reference counting for their various shared pieces of data, like keys and key lists. * ratelimiter.[ch]: Used as an integral part of cookie.[ch] for ratelimiting certain types of cryptographic operations in accordance with particular WireGuard semantics. * allowedips.[ch], peerlookup.[ch]: The main lookup structures of WireGuard, the former being trie-like with particular semantics, an integral part of the design of the protocol, and the latter just being nice helper functions around the various hashtables we use. * device.[ch]: Implementation of functions for the netdevice and for rtnl, responsible for maintaining the life of a given interface and wiring it up to the rest of WireGuard. * peer.[ch]: Each interface has a list of peers, with helper functions available here for creation, destruction, and reference counting. * socket.[ch]: Implementation of functions related to udp_socket and the general set of kernel socket APIs, for sending and receiving ciphertext UDP packets, and taking care of WireGuard-specific sticky socket routing semantics for the automatic roaming. * netlink.[ch]: Userspace API entry point for configuring WireGuard peers and devices. The API has been implemented by several userspace tools and network management utility, and the WireGuard project distributes the basic wg(8) tool. * queueing.[ch]: Shared function on the rx and tx path for handling the various queues used in the multicore algorithms. * send.c: Handles encrypting outgoing packets in parallel on multiple cores, before sending them in order on a single core, via workqueues and ring buffers. Also handles sending handshake and cookie messages as part of the protocol, in parallel. * receive.c: Handles decrypting incoming packets in parallel on multiple cores, before passing them off in order to be ingested via the rest of the networking subsystem with GRO via the typical NAPI poll function. Also handles receiving handshake and cookie messages as part of the protocol, in parallel. * timers.[ch]: Uses the timer wheel to implement protocol particular event timeouts, and gives a set of very simple event-driven entry point functions for callers. * main.c, version.h: Initialization and deinitialization of the module. * selftest/*.h: Runtime unit tests for some of the most security sensitive functions. * tools/testing/selftests/wireguard/netns.sh: Aforementioned testing script using network namespaces. This commit aims to be as self-contained as possible, implementing WireGuard as a standalone module not needing much special handling or coordination from the network subsystem. I expect for future optimizations to the network stack to positively improve WireGuard, and vice-versa, but for the time being, this exists as intentionally standalone. We introduce a menu option for CONFIG_WIREGUARD, as well as providing a verbose debug log and self-tests via CONFIG_WIREGUARD_DEBUG. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Cc: David Miller <davem@davemloft.net> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: linux-crypto@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: netdev@vger.kernel.org Signed-off-by: David S. Miller <davem@davemloft.net>
244 lines
8 KiB
C
244 lines
8 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 "timers.h"
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#include "device.h"
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#include "peer.h"
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#include "queueing.h"
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#include "socket.h"
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/*
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* - Timer for retransmitting the handshake if we don't hear back after
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* `REKEY_TIMEOUT + jitter` ms.
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*
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* - Timer for sending empty packet if we have received a packet but after have
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* not sent one for `KEEPALIVE_TIMEOUT` ms.
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*
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* - Timer for initiating new handshake if we have sent a packet but after have
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* not received one (even empty) for `(KEEPALIVE_TIMEOUT + REKEY_TIMEOUT) +
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* jitter` ms.
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*
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* - Timer for zeroing out all ephemeral keys after `(REJECT_AFTER_TIME * 3)` ms
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* if no new keys have been received.
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*
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* - Timer for, if enabled, sending an empty authenticated packet every user-
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* specified seconds.
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*/
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static inline void mod_peer_timer(struct wg_peer *peer,
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struct timer_list *timer,
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unsigned long expires)
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{
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rcu_read_lock_bh();
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if (likely(netif_running(peer->device->dev) &&
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!READ_ONCE(peer->is_dead)))
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mod_timer(timer, expires);
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rcu_read_unlock_bh();
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}
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static void wg_expired_retransmit_handshake(struct timer_list *timer)
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{
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struct wg_peer *peer = from_timer(peer, timer,
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timer_retransmit_handshake);
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if (peer->timer_handshake_attempts > MAX_TIMER_HANDSHAKES) {
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pr_debug("%s: Handshake for peer %llu (%pISpfsc) did not complete after %d attempts, giving up\n",
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peer->device->dev->name, peer->internal_id,
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&peer->endpoint.addr, MAX_TIMER_HANDSHAKES + 2);
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del_timer(&peer->timer_send_keepalive);
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/* We drop all packets without a keypair and don't try again,
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* if we try unsuccessfully for too long to make a handshake.
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*/
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wg_packet_purge_staged_packets(peer);
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/* We set a timer for destroying any residue that might be left
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* of a partial exchange.
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*/
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if (!timer_pending(&peer->timer_zero_key_material))
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mod_peer_timer(peer, &peer->timer_zero_key_material,
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jiffies + REJECT_AFTER_TIME * 3 * HZ);
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} else {
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++peer->timer_handshake_attempts;
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pr_debug("%s: Handshake for peer %llu (%pISpfsc) did not complete after %d seconds, retrying (try %d)\n",
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peer->device->dev->name, peer->internal_id,
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&peer->endpoint.addr, REKEY_TIMEOUT,
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peer->timer_handshake_attempts + 1);
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/* We clear the endpoint address src address, in case this is
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* the cause of trouble.
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*/
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wg_socket_clear_peer_endpoint_src(peer);
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wg_packet_send_queued_handshake_initiation(peer, true);
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}
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}
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static void wg_expired_send_keepalive(struct timer_list *timer)
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{
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struct wg_peer *peer = from_timer(peer, timer, timer_send_keepalive);
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wg_packet_send_keepalive(peer);
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if (peer->timer_need_another_keepalive) {
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peer->timer_need_another_keepalive = false;
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mod_peer_timer(peer, &peer->timer_send_keepalive,
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jiffies + KEEPALIVE_TIMEOUT * HZ);
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}
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}
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static void wg_expired_new_handshake(struct timer_list *timer)
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{
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struct wg_peer *peer = from_timer(peer, timer, timer_new_handshake);
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pr_debug("%s: Retrying handshake with peer %llu (%pISpfsc) because we stopped hearing back after %d seconds\n",
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peer->device->dev->name, peer->internal_id,
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&peer->endpoint.addr, KEEPALIVE_TIMEOUT + REKEY_TIMEOUT);
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/* We clear the endpoint address src address, in case this is the cause
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* of trouble.
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*/
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wg_socket_clear_peer_endpoint_src(peer);
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wg_packet_send_queued_handshake_initiation(peer, false);
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}
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static void wg_expired_zero_key_material(struct timer_list *timer)
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{
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struct wg_peer *peer = from_timer(peer, timer, timer_zero_key_material);
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rcu_read_lock_bh();
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if (!READ_ONCE(peer->is_dead)) {
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wg_peer_get(peer);
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if (!queue_work(peer->device->handshake_send_wq,
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&peer->clear_peer_work))
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/* If the work was already on the queue, we want to drop
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* the extra reference.
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*/
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wg_peer_put(peer);
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}
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rcu_read_unlock_bh();
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}
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static void wg_queued_expired_zero_key_material(struct work_struct *work)
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{
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struct wg_peer *peer = container_of(work, struct wg_peer,
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clear_peer_work);
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pr_debug("%s: Zeroing out all keys for peer %llu (%pISpfsc), since we haven't received a new one in %d seconds\n",
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peer->device->dev->name, peer->internal_id,
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&peer->endpoint.addr, REJECT_AFTER_TIME * 3);
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wg_noise_handshake_clear(&peer->handshake);
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wg_noise_keypairs_clear(&peer->keypairs);
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wg_peer_put(peer);
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}
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static void wg_expired_send_persistent_keepalive(struct timer_list *timer)
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{
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struct wg_peer *peer = from_timer(peer, timer,
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timer_persistent_keepalive);
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if (likely(peer->persistent_keepalive_interval))
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wg_packet_send_keepalive(peer);
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}
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/* Should be called after an authenticated data packet is sent. */
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void wg_timers_data_sent(struct wg_peer *peer)
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{
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if (!timer_pending(&peer->timer_new_handshake))
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mod_peer_timer(peer, &peer->timer_new_handshake,
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jiffies + (KEEPALIVE_TIMEOUT + REKEY_TIMEOUT) * HZ +
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prandom_u32_max(REKEY_TIMEOUT_JITTER_MAX_JIFFIES));
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}
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/* Should be called after an authenticated data packet is received. */
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void wg_timers_data_received(struct wg_peer *peer)
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{
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if (likely(netif_running(peer->device->dev))) {
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if (!timer_pending(&peer->timer_send_keepalive))
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mod_peer_timer(peer, &peer->timer_send_keepalive,
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jiffies + KEEPALIVE_TIMEOUT * HZ);
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else
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peer->timer_need_another_keepalive = true;
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}
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}
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/* Should be called after any type of authenticated packet is sent, whether
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* keepalive, data, or handshake.
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*/
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void wg_timers_any_authenticated_packet_sent(struct wg_peer *peer)
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{
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del_timer(&peer->timer_send_keepalive);
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}
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/* Should be called after any type of authenticated packet is received, whether
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* keepalive, data, or handshake.
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*/
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void wg_timers_any_authenticated_packet_received(struct wg_peer *peer)
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{
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del_timer(&peer->timer_new_handshake);
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}
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/* Should be called after a handshake initiation message is sent. */
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void wg_timers_handshake_initiated(struct wg_peer *peer)
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{
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mod_peer_timer(peer, &peer->timer_retransmit_handshake,
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jiffies + REKEY_TIMEOUT * HZ +
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prandom_u32_max(REKEY_TIMEOUT_JITTER_MAX_JIFFIES));
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}
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/* Should be called after a handshake response message is received and processed
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* or when getting key confirmation via the first data message.
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*/
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void wg_timers_handshake_complete(struct wg_peer *peer)
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{
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del_timer(&peer->timer_retransmit_handshake);
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peer->timer_handshake_attempts = 0;
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peer->sent_lastminute_handshake = false;
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ktime_get_real_ts64(&peer->walltime_last_handshake);
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}
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/* Should be called after an ephemeral key is created, which is before sending a
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* handshake response or after receiving a handshake response.
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*/
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void wg_timers_session_derived(struct wg_peer *peer)
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{
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mod_peer_timer(peer, &peer->timer_zero_key_material,
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jiffies + REJECT_AFTER_TIME * 3 * HZ);
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}
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/* Should be called before a packet with authentication, whether
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* keepalive, data, or handshakem is sent, or after one is received.
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*/
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void wg_timers_any_authenticated_packet_traversal(struct wg_peer *peer)
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{
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if (peer->persistent_keepalive_interval)
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mod_peer_timer(peer, &peer->timer_persistent_keepalive,
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jiffies + peer->persistent_keepalive_interval * HZ);
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}
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void wg_timers_init(struct wg_peer *peer)
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{
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timer_setup(&peer->timer_retransmit_handshake,
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wg_expired_retransmit_handshake, 0);
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timer_setup(&peer->timer_send_keepalive, wg_expired_send_keepalive, 0);
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timer_setup(&peer->timer_new_handshake, wg_expired_new_handshake, 0);
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timer_setup(&peer->timer_zero_key_material,
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wg_expired_zero_key_material, 0);
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timer_setup(&peer->timer_persistent_keepalive,
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wg_expired_send_persistent_keepalive, 0);
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INIT_WORK(&peer->clear_peer_work, wg_queued_expired_zero_key_material);
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peer->timer_handshake_attempts = 0;
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peer->sent_lastminute_handshake = false;
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peer->timer_need_another_keepalive = false;
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}
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void wg_timers_stop(struct wg_peer *peer)
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{
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del_timer_sync(&peer->timer_retransmit_handshake);
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del_timer_sync(&peer->timer_send_keepalive);
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del_timer_sync(&peer->timer_new_handshake);
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del_timer_sync(&peer->timer_zero_key_material);
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del_timer_sync(&peer->timer_persistent_keepalive);
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flush_work(&peer->clear_peer_work);
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}
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