From e7096c131e5161fa3b8e52a650d7719d2857adfd Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Mon, 9 Dec 2019 00:27:34 +0100 Subject: net: WireGuard secure network tunnel 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 Cc: David Miller Cc: Greg KH Cc: Linus Torvalds Cc: Herbert Xu Cc: linux-crypto@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: netdev@vger.kernel.org Signed-off-by: David S. Miller --- drivers/net/wireguard/send.c | 413 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 413 insertions(+) create mode 100644 drivers/net/wireguard/send.c (limited to 'drivers/net/wireguard/send.c') diff --git a/drivers/net/wireguard/send.c b/drivers/net/wireguard/send.c new file mode 100644 index 000000000000..c13260563446 --- /dev/null +++ b/drivers/net/wireguard/send.c @@ -0,0 +1,413 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2015-2019 Jason A. Donenfeld . All Rights Reserved. + */ + +#include "queueing.h" +#include "timers.h" +#include "device.h" +#include "peer.h" +#include "socket.h" +#include "messages.h" +#include "cookie.h" + +#include +#include +#include +#include +#include +#include + +static void wg_packet_send_handshake_initiation(struct wg_peer *peer) +{ + struct message_handshake_initiation packet; + + if (!wg_birthdate_has_expired(atomic64_read(&peer->last_sent_handshake), + REKEY_TIMEOUT)) + return; /* This function is rate limited. */ + + atomic64_set(&peer->last_sent_handshake, ktime_get_coarse_boottime_ns()); + net_dbg_ratelimited("%s: Sending handshake initiation to peer %llu (%pISpfsc)\n", + peer->device->dev->name, peer->internal_id, + &peer->endpoint.addr); + + if (wg_noise_handshake_create_initiation(&packet, &peer->handshake)) { + wg_cookie_add_mac_to_packet(&packet, sizeof(packet), peer); + wg_timers_any_authenticated_packet_traversal(peer); + wg_timers_any_authenticated_packet_sent(peer); + atomic64_set(&peer->last_sent_handshake, + ktime_get_coarse_boottime_ns()); + wg_socket_send_buffer_to_peer(peer, &packet, sizeof(packet), + HANDSHAKE_DSCP); + wg_timers_handshake_initiated(peer); + } +} + +void wg_packet_handshake_send_worker(struct work_struct *work) +{ + struct wg_peer *peer = container_of(work, struct wg_peer, + transmit_handshake_work); + + wg_packet_send_handshake_initiation(peer); + wg_peer_put(peer); +} + +void wg_packet_send_queued_handshake_initiation(struct wg_peer *peer, + bool is_retry) +{ + if (!is_retry) + peer->timer_handshake_attempts = 0; + + rcu_read_lock_bh(); + /* We check last_sent_handshake here in addition to the actual function + * we're queueing up, so that we don't queue things if not strictly + * necessary: + */ + if (!wg_birthdate_has_expired(atomic64_read(&peer->last_sent_handshake), + REKEY_TIMEOUT) || + unlikely(READ_ONCE(peer->is_dead))) + goto out; + + wg_peer_get(peer); + /* Queues up calling packet_send_queued_handshakes(peer), where we do a + * peer_put(peer) after: + */ + if (!queue_work(peer->device->handshake_send_wq, + &peer->transmit_handshake_work)) + /* If the work was already queued, we want to drop the + * extra reference: + */ + wg_peer_put(peer); +out: + rcu_read_unlock_bh(); +} + +void wg_packet_send_handshake_response(struct wg_peer *peer) +{ + struct message_handshake_response packet; + + atomic64_set(&peer->last_sent_handshake, ktime_get_coarse_boottime_ns()); + net_dbg_ratelimited("%s: Sending handshake response to peer %llu (%pISpfsc)\n", + peer->device->dev->name, peer->internal_id, + &peer->endpoint.addr); + + if (wg_noise_handshake_create_response(&packet, &peer->handshake)) { + wg_cookie_add_mac_to_packet(&packet, sizeof(packet), peer); + if (wg_noise_handshake_begin_session(&peer->handshake, + &peer->keypairs)) { + wg_timers_session_derived(peer); + wg_timers_any_authenticated_packet_traversal(peer); + wg_timers_any_authenticated_packet_sent(peer); + atomic64_set(&peer->last_sent_handshake, + ktime_get_coarse_boottime_ns()); + wg_socket_send_buffer_to_peer(peer, &packet, + sizeof(packet), + HANDSHAKE_DSCP); + } + } +} + +void wg_packet_send_handshake_cookie(struct wg_device *wg, + struct sk_buff *initiating_skb, + __le32 sender_index) +{ + struct message_handshake_cookie packet; + + net_dbg_skb_ratelimited("%s: Sending cookie response for denied handshake message for %pISpfsc\n", + wg->dev->name, initiating_skb); + wg_cookie_message_create(&packet, initiating_skb, sender_index, + &wg->cookie_checker); + wg_socket_send_buffer_as_reply_to_skb(wg, initiating_skb, &packet, + sizeof(packet)); +} + +static void keep_key_fresh(struct wg_peer *peer) +{ + struct noise_keypair *keypair; + bool send = false; + + rcu_read_lock_bh(); + keypair = rcu_dereference_bh(peer->keypairs.current_keypair); + if (likely(keypair && READ_ONCE(keypair->sending.is_valid)) && + (unlikely(atomic64_read(&keypair->sending.counter.counter) > + REKEY_AFTER_MESSAGES) || + (keypair->i_am_the_initiator && + unlikely(wg_birthdate_has_expired(keypair->sending.birthdate, + REKEY_AFTER_TIME))))) + send = true; + rcu_read_unlock_bh(); + + if (send) + wg_packet_send_queued_handshake_initiation(peer, false); +} + +static unsigned int calculate_skb_padding(struct sk_buff *skb) +{ + /* We do this modulo business with the MTU, just in case the networking + * layer gives us a packet that's bigger than the MTU. In that case, we + * wouldn't want the final subtraction to overflow in the case of the + * padded_size being clamped. + */ + unsigned int last_unit = skb->len % PACKET_CB(skb)->mtu; + unsigned int padded_size = ALIGN(last_unit, MESSAGE_PADDING_MULTIPLE); + + if (padded_size > PACKET_CB(skb)->mtu) + padded_size = PACKET_CB(skb)->mtu; + return padded_size - last_unit; +} + +static bool encrypt_packet(struct sk_buff *skb, struct noise_keypair *keypair) +{ + unsigned int padding_len, plaintext_len, trailer_len; + struct scatterlist sg[MAX_SKB_FRAGS + 8]; + struct message_data *header; + struct sk_buff *trailer; + int num_frags; + + /* Calculate lengths. */ + padding_len = calculate_skb_padding(skb); + trailer_len = padding_len + noise_encrypted_len(0); + plaintext_len = skb->len + padding_len; + + /* Expand data section to have room for padding and auth tag. */ + num_frags = skb_cow_data(skb, trailer_len, &trailer); + if (unlikely(num_frags < 0 || num_frags > ARRAY_SIZE(sg))) + return false; + + /* Set the padding to zeros, and make sure it and the auth tag are part + * of the skb. + */ + memset(skb_tail_pointer(trailer), 0, padding_len); + + /* Expand head section to have room for our header and the network + * stack's headers. + */ + if (unlikely(skb_cow_head(skb, DATA_PACKET_HEAD_ROOM) < 0)) + return false; + + /* Finalize checksum calculation for the inner packet, if required. */ + if (unlikely(skb->ip_summed == CHECKSUM_PARTIAL && + skb_checksum_help(skb))) + return false; + + /* Only after checksumming can we safely add on the padding at the end + * and the header. + */ + skb_set_inner_network_header(skb, 0); + header = (struct message_data *)skb_push(skb, sizeof(*header)); + header->header.type = cpu_to_le32(MESSAGE_DATA); + header->key_idx = keypair->remote_index; + header->counter = cpu_to_le64(PACKET_CB(skb)->nonce); + pskb_put(skb, trailer, trailer_len); + + /* Now we can encrypt the scattergather segments */ + sg_init_table(sg, num_frags); + if (skb_to_sgvec(skb, sg, sizeof(struct message_data), + noise_encrypted_len(plaintext_len)) <= 0) + return false; + return chacha20poly1305_encrypt_sg_inplace(sg, plaintext_len, NULL, 0, + PACKET_CB(skb)->nonce, + keypair->sending.key); +} + +void wg_packet_send_keepalive(struct wg_peer *peer) +{ + struct sk_buff *skb; + + if (skb_queue_empty(&peer->staged_packet_queue)) { + skb = alloc_skb(DATA_PACKET_HEAD_ROOM + MESSAGE_MINIMUM_LENGTH, + GFP_ATOMIC); + if (unlikely(!skb)) + return; + skb_reserve(skb, DATA_PACKET_HEAD_ROOM); + skb->dev = peer->device->dev; + PACKET_CB(skb)->mtu = skb->dev->mtu; + skb_queue_tail(&peer->staged_packet_queue, skb); + net_dbg_ratelimited("%s: Sending keepalive packet to peer %llu (%pISpfsc)\n", + peer->device->dev->name, peer->internal_id, + &peer->endpoint.addr); + } + + wg_packet_send_staged_packets(peer); +} + +static void wg_packet_create_data_done(struct sk_buff *first, + struct wg_peer *peer) +{ + struct sk_buff *skb, *next; + bool is_keepalive, data_sent = false; + + wg_timers_any_authenticated_packet_traversal(peer); + wg_timers_any_authenticated_packet_sent(peer); + skb_list_walk_safe(first, skb, next) { + is_keepalive = skb->len == message_data_len(0); + if (likely(!wg_socket_send_skb_to_peer(peer, skb, + PACKET_CB(skb)->ds) && !is_keepalive)) + data_sent = true; + } + + if (likely(data_sent)) + wg_timers_data_sent(peer); + + keep_key_fresh(peer); +} + +void wg_packet_tx_worker(struct work_struct *work) +{ + struct crypt_queue *queue = container_of(work, struct crypt_queue, + work); + struct noise_keypair *keypair; + enum packet_state state; + struct sk_buff *first; + struct wg_peer *peer; + + while ((first = __ptr_ring_peek(&queue->ring)) != NULL && + (state = atomic_read_acquire(&PACKET_CB(first)->state)) != + PACKET_STATE_UNCRYPTED) { + __ptr_ring_discard_one(&queue->ring); + peer = PACKET_PEER(first); + keypair = PACKET_CB(first)->keypair; + + if (likely(state == PACKET_STATE_CRYPTED)) + wg_packet_create_data_done(first, peer); + else + kfree_skb_list(first); + + wg_noise_keypair_put(keypair, false); + wg_peer_put(peer); + } +} + +void wg_packet_encrypt_worker(struct work_struct *work) +{ + struct crypt_queue *queue = container_of(work, struct multicore_worker, + work)->ptr; + struct sk_buff *first, *skb, *next; + + while ((first = ptr_ring_consume_bh(&queue->ring)) != NULL) { + enum packet_state state = PACKET_STATE_CRYPTED; + + skb_list_walk_safe(first, skb, next) { + if (likely(encrypt_packet(skb, + PACKET_CB(first)->keypair))) { + wg_reset_packet(skb); + } else { + state = PACKET_STATE_DEAD; + break; + } + } + wg_queue_enqueue_per_peer(&PACKET_PEER(first)->tx_queue, first, + state); + + } +} + +static void wg_packet_create_data(struct sk_buff *first) +{ + struct wg_peer *peer = PACKET_PEER(first); + struct wg_device *wg = peer->device; + int ret = -EINVAL; + + rcu_read_lock_bh(); + if (unlikely(READ_ONCE(peer->is_dead))) + goto err; + + ret = wg_queue_enqueue_per_device_and_peer(&wg->encrypt_queue, + &peer->tx_queue, first, + wg->packet_crypt_wq, + &wg->encrypt_queue.last_cpu); + if (unlikely(ret == -EPIPE)) + wg_queue_enqueue_per_peer(&peer->tx_queue, first, + PACKET_STATE_DEAD); +err: + rcu_read_unlock_bh(); + if (likely(!ret || ret == -EPIPE)) + return; + wg_noise_keypair_put(PACKET_CB(first)->keypair, false); + wg_peer_put(peer); + kfree_skb_list(first); +} + +void wg_packet_purge_staged_packets(struct wg_peer *peer) +{ + spin_lock_bh(&peer->staged_packet_queue.lock); + peer->device->dev->stats.tx_dropped += peer->staged_packet_queue.qlen; + __skb_queue_purge(&peer->staged_packet_queue); + spin_unlock_bh(&peer->staged_packet_queue.lock); +} + +void wg_packet_send_staged_packets(struct wg_peer *peer) +{ + struct noise_symmetric_key *key; + struct noise_keypair *keypair; + struct sk_buff_head packets; + struct sk_buff *skb; + + /* Steal the current queue into our local one. */ + __skb_queue_head_init(&packets); + spin_lock_bh(&peer->staged_packet_queue.lock); + skb_queue_splice_init(&peer->staged_packet_queue, &packets); + spin_unlock_bh(&peer->staged_packet_queue.lock); + if (unlikely(skb_queue_empty(&packets))) + return; + + /* First we make sure we have a valid reference to a valid key. */ + rcu_read_lock_bh(); + keypair = wg_noise_keypair_get( + rcu_dereference_bh(peer->keypairs.current_keypair)); + rcu_read_unlock_bh(); + if (unlikely(!keypair)) + goto out_nokey; + key = &keypair->sending; + if (unlikely(!READ_ONCE(key->is_valid))) + goto out_nokey; + if (unlikely(wg_birthdate_has_expired(key->birthdate, + REJECT_AFTER_TIME))) + goto out_invalid; + + /* After we know we have a somewhat valid key, we now try to assign + * nonces to all of the packets in the queue. If we can't assign nonces + * for all of them, we just consider it a failure and wait for the next + * handshake. + */ + skb_queue_walk(&packets, skb) { + /* 0 for no outer TOS: no leak. TODO: at some later point, we + * might consider using flowi->tos as outer instead. + */ + PACKET_CB(skb)->ds = ip_tunnel_ecn_encap(0, ip_hdr(skb), skb); + PACKET_CB(skb)->nonce = + atomic64_inc_return(&key->counter.counter) - 1; + if (unlikely(PACKET_CB(skb)->nonce >= REJECT_AFTER_MESSAGES)) + goto out_invalid; + } + + packets.prev->next = NULL; + wg_peer_get(keypair->entry.peer); + PACKET_CB(packets.next)->keypair = keypair; + wg_packet_create_data(packets.next); + return; + +out_invalid: + WRITE_ONCE(key->is_valid, false); +out_nokey: + wg_noise_keypair_put(keypair, false); + + /* We orphan the packets if we're waiting on a handshake, so that they + * don't block a socket's pool. + */ + skb_queue_walk(&packets, skb) + skb_orphan(skb); + /* Then we put them back on the top of the queue. We're not too + * concerned about accidentally getting things a little out of order if + * packets are being added really fast, because this queue is for before + * packets can even be sent and it's small anyway. + */ + spin_lock_bh(&peer->staged_packet_queue.lock); + skb_queue_splice(&packets, &peer->staged_packet_queue); + spin_unlock_bh(&peer->staged_packet_queue.lock); + + /* If we're exiting because there's something wrong with the key, it + * means we should initiate a new handshake. + */ + wg_packet_send_queued_handshake_initiation(peer, false); +} -- cgit v1.2.3