// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2015-2019 Jason A. Donenfeld <[email protected]>. All Rights Reserved.
*/
#include "queueing.h"
#include "device.h"
#include "peer.h"
#include "timers.h"
#include "messages.h"
#include "cookie.h"
#include "socket.h"
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/udp.h>
#include <net/ip_tunnels.h>
/* Must be called with bh disabled. */
static void update_rx_stats(struct wg_peer *peer, size_t len)
{
dev_sw_netstats_rx_add(peer->device->dev, len);
peer->rx_bytes += len;
}
#define SKB_TYPE_LE32(skb) (((struct message_header *)(skb)->data)->type)
static size_t validate_header_len(struct sk_buff *skb)
{
if (unlikely(skb->len < sizeof(struct message_header)))
return 0;
if (SKB_TYPE_LE32(skb) == cpu_to_le32(MESSAGE_DATA) &&
skb->len >= MESSAGE_MINIMUM_LENGTH)
return sizeof(struct message_data);
if (SKB_TYPE_LE32(skb) == cpu_to_le32(MESSAGE_HANDSHAKE_INITIATION) &&
skb->len == sizeof(struct message_handshake_initiation))
return sizeof(struct message_handshake_initiation);
if (SKB_TYPE_LE32(skb) == cpu_to_le32(MESSAGE_HANDSHAKE_RESPONSE) &&
skb->len == sizeof(struct message_handshake_response))
return sizeof(struct message_handshake_response);
if (SKB_TYPE_LE32(skb) == cpu_to_le32(MESSAGE_HANDSHAKE_COOKIE) &&
skb->len == sizeof(struct message_handshake_cookie))
return sizeof(struct message_handshake_cookie);
return 0;
}
static int prepare_skb_header(struct sk_buff *skb, struct wg_device *wg)
{
size_t data_offset, data_len, header_len;
struct udphdr *udp;
if (unlikely(!wg_check_packet_protocol(skb) ||
skb_transport_header(skb) < skb->head ||
(skb_transport_header(skb) + sizeof(struct udphdr)) >
skb_tail_pointer(skb)))
return -EINVAL; /* Bogus IP header */
udp = udp_hdr(skb);
data_offset = (u8 *)udp - skb->data;
if (unlikely(data_offset > U16_MAX ||
data_offset + sizeof(struct udphdr) > skb->len))
/* Packet has offset at impossible location or isn't big enough
* to have UDP fields.
*/
return -EINVAL;
data_len = ntohs(udp->len);
if (unlikely(data_len < sizeof(struct udphdr) ||
data_len > skb->len - data_offset))
/* UDP packet is reporting too small of a size or lying about
* its size.
*/
return -EINVAL;
data_len -= sizeof(struct udphdr);
data_offset = (u8 *)udp + sizeof(struct udphdr) - skb->data;
if (unlikely(!pskb_may_pull(skb,
data_offset + sizeof(struct message_header)) ||
pskb_trim(skb, data_len + data_offset) < 0))
return -EINVAL;
skb_pull(skb, data_offset);
if (unlikely(skb->len != data_len))
/* Final len does not agree with calculated len */
return -EINVAL;
header_len = validate_header_len(skb);
if (unlikely(!header_len))
return -EINVAL;
__skb_push(skb, data_offset);
if (unlikely(!pskb_may_pull(skb, data_offset + header_len)))
return -EINVAL;
__skb_pull(skb, data_offset);
return 0;
}
static void wg_receive_handshake_packet(struct wg_device *wg,
struct sk_buff *skb)
{
enum cookie_mac_state mac_state;
struct wg_peer *peer = NULL;
/* This is global, so that our load calculation applies to the whole
* system. We don't care about races with it at all.
*/
static u64 last_under_load;
bool packet_needs_cookie;
bool under_load;
if (SKB_TYPE_LE32(skb) == cpu_to_le32(MESSAGE_HANDSHAKE_COOKIE)) {
net_dbg_skb_ratelimited("%s: Receiving cookie response from %pISpfsc\n",
wg->dev->name, skb);
wg_cookie_message_consume(
(struct message_handshake_cookie *)skb->data, wg);
return;
}
under_load = atomic_read(&wg->handshake_queue_len) >=
MAX_QUEUED_INCOMING_HANDSHAKES / 8;
if (under_load) {
last_under_load = ktime_get_coarse_boottime_ns();
} else if (last_under_load) {
under_load = !wg_birthdate_has_expired(last_under_load, 1);
if (!under_load)
last_under_load = 0;
}
mac_state = wg_cookie_validate_packet(&wg->cookie_checker, skb,
under_load);
if ((under_load && mac_state == VALID_MAC_WITH_COOKIE) ||
(!under_load && mac_state == VALID_MAC_BUT_NO_COOKIE)) {
packet_needs_cookie = false;
} else if (under_load && mac_state == VALID_MAC_BUT_NO_COOKIE) {
packet_needs_cookie = true;
} else {
net_dbg_skb_ratelimited("%s: Invalid MAC of handshake, dropping packet from %pISpfsc\n",
wg->dev->name, skb);
return;
}
switch (SKB_TYPE_LE32(skb)) {
case cpu_to_le32(MESSAGE_HANDSHAKE_INITIATION): {
struct message_handshake_initiation *message =
(struct message_handshake_initiation *)skb->data;
if (packet_needs_cookie) {
wg_packet_send_handshake_cookie(wg, skb,
message->sender_index);
return;
}
peer = wg_noise_handshake_consume_initiation(message, wg);
if (unlikely(!peer)) {
net_dbg_skb_ratelimited("%s: Invalid handshake initiation from %pISpfsc\n",
wg->dev->name, skb);
return;
}
wg_socket_set_peer_endpoint_from_skb(peer, skb);
net_dbg_ratelimited("%s: Receiving handshake initiation from peer %llu (%pISpfsc)\n",
wg->dev->name, peer->internal_id,
&peer->endpoint.addr);
wg_packet_send_handshake_response(peer);
break;
}
case cpu_to_le32(MESSAGE_HANDSHAKE_RESPONSE): {
struct message_handshake_response *message =
(struct message_handshake_response *)skb->data;
if (packet_needs_cookie) {
wg_packet_send_handshake_cookie(wg, skb,
message->sender_index);
return;
}
peer = wg_noise_handshake_consume_response(message, wg);
if (unlikely(!peer)) {
net_dbg_skb_ratelimited("%s: Invalid handshake response from %pISpfsc\n",
wg->dev->name, skb);
return;
}
wg_socket_set_peer_endpoint_from_skb(peer, skb);
net_dbg_ratelimited("%s: Receiving handshake response from peer %llu (%pISpfsc)\n",
wg->dev->name, peer->internal_id,
&peer->endpoint.addr);
if (wg_noise_handshake_begin_session(&peer->handshake,
&peer->keypairs)) {
wg_timers_session_derived(peer);
wg_timers_handshake_complete(peer);
/* Calling this function will either send any existing
* packets in the queue and not send a keepalive, which
* is the best case, Or, if there's nothing in the
* queue, it will send a keepalive, in order to give
* immediate confirmation of the session.
*/
wg_packet_send_keepalive(peer);
}
break;
}
}
if (unlikely(!peer)) {
WARN(1, "Somehow a wrong type of packet wound up in the handshake queue!\n");
return;
}
local_bh_disable();
update_rx_stats(peer, skb->len);
local_bh_enable();
wg_timers_any_authenticated_packet_received(peer);
wg_timers_any_authenticated_packet_traversal(peer);
wg_peer_put(peer);
}
void wg_packet_handshake_receive_worker(struct work_struct *work)
{
struct crypt_queue *queue = container_of(work, struct multicore_worker, work)->ptr;
struct wg_device *wg = container_of(queue, struct wg_device, handshake_queue);
struct sk_buff *skb;
while ((skb = ptr_ring_consume_bh(&queue->ring)) != NULL) {
wg_receive_handshake_packet(wg, skb);
dev_kfree_skb(skb);
atomic_dec(&wg->handshake_queue_len);
cond_resched();
}
}
static void keep_key_fresh(struct wg_peer *peer)
{
struct noise_keypair *keypair;
bool send;
if (peer->sent_lastminute_handshake)
return;
rcu_read_lock_bh();
keypair = rcu_dereference_bh(peer->keypairs.current_keypair);
send = keypair && READ_ONCE(keypair->sending.is_valid) &&
keypair->i_am_the_initiator &&
wg_birthdate_has_expired(keypair->sending.birthdate,
REJECT_AFTER_TIME - KEEPALIVE_TIMEOUT - REKEY_TIMEOUT);
rcu_read_unlock_bh();
if (unlikely(send)) {
peer->sent_lastminute_handshake = true;
wg_packet_send_queued_handshake_initiation(peer, false);
}
}
static bool decrypt_packet(struct sk_buff *skb, struct noise_keypair *keypair)
{
struct scatterlist sg[MAX_SKB_FRAGS + 8];
struct sk_buff *trailer;
unsigned int offset;
int num_frags;
if (unlikely(!keypair))
return false;
if (unlikely(!READ_ONCE(keypair->receiving.is_valid) ||
wg_birthdate_has_expired(keypair->receiving.birthdate, REJECT_AFTER_TIME) ||
READ_ONCE(keypair->receiving_counter.counter) >= REJECT_AFTER_MESSAGES)) {
WRITE_ONCE(keypair->receiving.is_valid, false);
return false;
}
PACKET_CB(skb)->nonce =
le64_to_cpu(((struct message_data *)skb->data)->counter);
/* We ensure that the network header is part of the packet before we
* call skb_cow_data, so that there's no chance that data is removed
* from the skb, so that later we can extract the original endpoint.
*/
offset = -skb_network_offset(skb);
skb_push(skb, offset);
num_frags = skb_cow_data(skb, 0, &trailer);
offset += sizeof(struct message_data);
skb_pull(skb, offset);
if (unlikely(num_frags < 0 || num_frags > ARRAY_SIZE(sg)))
return false;
sg_init_table(sg, num_frags);
if (skb_to_sgvec(skb, sg, 0, skb->len) <= 0)
return false;
if (!chacha20poly1305_decrypt_sg_inplace(sg, skb->len, NULL, 0,
PACKET_CB(skb)->nonce,
keypair->receiving.key))
return false;
/* Another ugly situation of pushing and pulling the header so as to
* keep endpoint information intact.
*/
skb_push(skb, offset);
if (pskb_trim(skb, skb->len - noise_encrypted_len(0)))
return false;
skb_pull(skb, offset);
return true;
}
/* This is RFC6479, a replay detection bitmap algorithm that avoids bitshifts */
static bool counter_validate(struct noise_replay_counter *counter, u64 their_counter)
{
unsigned long index, index_current, top, i;
bool ret = false;
spin_lock_bh(&counter->lock);
if (unlikely(counter->counter >= REJECT_AFTER_MESSAGES + 1 ||
their_counter >= REJECT_AFTER_MESSAGES))
goto out;
++their_counter;
if (unlikely((COUNTER_WINDOW_SIZE + their_counter) <
counter->counter))
goto out;
index = their_counter >> ilog2(BITS_PER_LONG);
if (likely(their_counter > counter->counter)) {
index_current = counter->counter >> ilog2(BITS_PER_LONG);
top = min_t(unsigned long, index - index_current,
COUNTER_BITS_TOTAL / BITS_PER_LONG);
for (i = 1; i <= top; ++i)
counter->backtrack[(i + index_current) &
((COUNTER_BITS_TOTAL / BITS_PER_LONG) - 1)] = 0;
WRITE_ONCE(counter->counter, their_counter);
}
index &= (COUNTER_BITS_TOTAL / BITS_PER_LONG) - 1;
ret = !test_and_set_bit(their_counter & (BITS_PER_LONG - 1),
&counter->backtrack[index]);
out:
spin_unlock_bh(&counter->lock);
return ret;
}
#include "selftest/counter.c"
static void wg_packet_consume_data_done(struct wg_peer *peer,
struct sk_buff *skb,
struct endpoint *endpoint)
{
struct net_device *dev = peer->device->dev;
unsigned int len, len_before_trim;
struct wg_peer *routed_peer;
wg_socket_set_peer_endpoint(peer, endpoint);
if (unlikely(wg_noise_received_with_keypair(&peer->keypairs,
PACKET_CB(skb)->keypair))) {
wg_timers_handshake_complete(peer);
wg_packet_send_staged_packets(peer);
}
keep_key_fresh(peer);
wg_timers_any_authenticated_packet_received(peer);
wg_timers_any_authenticated_packet_traversal(peer);
/* A packet with length 0 is a keepalive packet */
if (unlikely(!skb->len)) {
update_rx_stats(peer, message_data_len(0));
net_dbg_ratelimited("%s: Receiving keepalive packet from peer %llu (%pISpfsc)\n",
dev->name, peer->internal_id,
&peer->endpoint.addr);
goto packet_processed;
}
wg_timers_data_received(peer);
if (unlikely(skb_network_header(skb) < skb->head))
goto dishonest_packet_size;
if (unlikely(!(pskb_network_may_pull(skb, sizeof(struct iphdr)) &&
(ip_hdr(skb)->version == 4 ||
(ip_hdr(skb)->version == 6 &&
pskb_network_may_pull(skb, sizeof(struct ipv6hdr)))))))
goto dishonest_packet_type;
skb->dev = dev;
/* We've already verified the Poly1305 auth tag, which means this packet
* was not modified in transit. We can therefore tell the networking
* stack that all checksums of every layer of encapsulation have already
* been checked "by the hardware" and therefore is unnecessary to check
* again in software.
*/
skb->ip_summed = CHECKSUM_UNNECESSARY;
skb->csum_level = ~0; /* All levels */
skb->protocol = ip_tunnel_parse_protocol(skb);
if (skb->protocol == htons(ETH_P_IP)) {
len = ntohs(ip_hdr(skb)->tot_len);
if (unlikely(len < sizeof(struct iphdr)))
goto dishonest_packet_size;
INET_ECN_decapsulate(skb, PACKET_CB(skb)->ds, ip_hdr(skb)->tos);
} else if (skb->protocol == htons(ETH_P_IPV6)) {
len = ntohs(ipv6_hdr(skb)->payload_len) +
sizeof(struct ipv6hdr);
INET_ECN_decapsulate(skb, PACKET_CB(skb)->ds, ipv6_get_dsfield(ipv6_hdr(skb)));
} else {
goto dishonest_packet_type;
}
if (unlikely(len > skb->len))
goto dishonest_packet_size;
len_before_trim = skb->len;
if (unlikely(pskb_trim(skb, len)))
goto packet_processed;
routed_peer = wg_allowedips_lookup_src(&peer->device->peer_allowedips,
skb);
wg_peer_put(routed_peer); /* We don't need the extra reference. */
if (unlikely(routed_peer != peer))
goto dishonest_packet_peer;
napi_gro_receive(&peer->napi, skb);
update_rx_stats(peer, message_data_len(len_before_trim));
return;
dishonest_packet_peer:
net_dbg_skb_ratelimited("%s: Packet has unallowed src IP (%pISc) from peer %llu (%pISpfsc)\n",
dev->name, skb, peer->internal_id,
&peer->endpoint.addr);
DEV_STATS_INC(dev, rx_errors);
DEV_STATS_INC(dev, rx_frame_errors);
goto packet_processed;
dishonest_packet_type:
net_dbg_ratelimited("%s: Packet is neither ipv4 nor ipv6 from peer %llu (%pISpfsc)\n",
dev->name, peer->internal_id, &peer->endpoint.addr);
DEV_STATS_INC(dev, rx_errors);
DEV_STATS_INC(dev, rx_frame_errors);
goto packet_processed;
dishonest_packet_size:
net_dbg_ratelimited("%s: Packet has incorrect size from peer %llu (%pISpfsc)\n",
dev->name, peer->internal_id, &peer->endpoint.addr);
DEV_STATS_INC(dev, rx_errors);
DEV_STATS_INC(dev, rx_length_errors);
goto packet_processed;
packet_processed:
dev_kfree_skb(skb);
}
int wg_packet_rx_poll(struct napi_struct *napi, int budget)
{
struct wg_peer *peer = container_of(napi, struct wg_peer, napi);
struct noise_keypair *keypair;
struct endpoint endpoint;
enum packet_state state;
struct sk_buff *skb;
int work_done = 0;
bool free;
if (unlikely(budget <= 0))
return 0;
while ((skb = wg_prev_queue_peek(&peer->rx_queue)) != NULL &&
(state = atomic_read_acquire(&PACKET_CB(skb)->state)) !=
PACKET_STATE_UNCRYPTED) {
wg_prev_queue_drop_peeked(&peer->rx_queue);
keypair = PACKET_CB(skb)->keypair;
free = true;
if (unlikely(state != PACKET_STATE_CRYPTED))
goto next;
if (unlikely(!counter_validate(&keypair->receiving_counter,
PACKET_CB(skb)->nonce))) {
net_dbg_ratelimited("%s: Packet has invalid nonce %llu (max %llu)\n",
peer->device->dev->name,
PACKET_CB(skb)->nonce,
READ_ONCE(keypair->receiving_counter.counter));
goto next;
}
if (unlikely(wg_socket_endpoint_from_skb(&endpoint, skb)))
goto next;
wg_reset_packet(skb, false);
wg_packet_consume_data_done(peer, skb, &endpoint);
free = false;
next:
wg_noise_keypair_put(keypair, false);
wg_peer_put(peer);
if (unlikely(free))
dev_kfree_skb(skb);
if (++work_done >= budget)
break;
}
if (work_done < budget)
napi_complete_done(napi, work_done);
return work_done;
}
void wg_packet_decrypt_worker(struct work_struct *work)
{
struct crypt_queue *queue = container_of(work, struct multicore_worker,
work)->ptr;
struct sk_buff *skb;
while ((skb = ptr_ring_consume_bh(&queue->ring)) != NULL) {
enum packet_state state =
likely(decrypt_packet(skb, PACKET_CB(skb)->keypair)) ?
PACKET_STATE_CRYPTED : PACKET_STATE_DEAD;
wg_queue_enqueue_per_peer_rx(skb, state);
if (need_resched())
cond_resched();
}
}
static void wg_packet_consume_data(struct wg_device *wg, struct sk_buff *skb)
{
__le32 idx = ((struct message_data *)skb->data)->key_idx;
struct wg_peer *peer = NULL;
int ret;
rcu_read_lock_bh();
PACKET_CB(skb)->keypair =
(struct noise_keypair *)wg_index_hashtable_lookup(
wg->index_hashtable, INDEX_HASHTABLE_KEYPAIR, idx,
&peer);
if (unlikely(!wg_noise_keypair_get(PACKET_CB(skb)->keypair)))
goto err_keypair;
if (unlikely(READ_ONCE(peer->is_dead)))
goto err;
ret = wg_queue_enqueue_per_device_and_peer(&wg->decrypt_queue, &peer->rx_queue, skb,
wg->packet_crypt_wq);
if (unlikely(ret == -EPIPE))
wg_queue_enqueue_per_peer_rx(skb, PACKET_STATE_DEAD);
if (likely(!ret || ret == -EPIPE)) {
rcu_read_unlock_bh();
return;
}
err:
wg_noise_keypair_put(PACKET_CB(skb)->keypair, false);
err_keypair:
rcu_read_unlock_bh();
wg_peer_put(peer);
dev_kfree_skb(skb);
}
void wg_packet_receive(struct wg_device *wg, struct sk_buff *skb)
{
if (unlikely(prepare_skb_header(skb, wg) < 0))
goto err;
switch (SKB_TYPE_LE32(skb)) {
case cpu_to_le32(MESSAGE_HANDSHAKE_INITIATION):
case cpu_to_le32(MESSAGE_HANDSHAKE_RESPONSE):
case cpu_to_le32(MESSAGE_HANDSHAKE_COOKIE): {
int cpu, ret = -EBUSY;
if (unlikely(!rng_is_initialized()))
goto drop;
if (atomic_read(&wg->handshake_queue_len) > MAX_QUEUED_INCOMING_HANDSHAKES / 2) {
if (spin_trylock_bh(&wg->handshake_queue.ring.producer_lock)) {
ret = __ptr_ring_produce(&wg->handshake_queue.ring, skb);
spin_unlock_bh(&wg->handshake_queue.ring.producer_lock);
}
} else
ret = ptr_ring_produce_bh(&wg->handshake_queue.ring, skb);
if (ret) {
drop:
net_dbg_skb_ratelimited("%s: Dropping handshake packet from %pISpfsc\n",
wg->dev->name, skb);
goto err;
}
atomic_inc(&wg->handshake_queue_len);
cpu = wg_cpumask_next_online(&wg->handshake_queue.last_cpu);
/* Queues up a call to packet_process_queued_handshake_packets(skb): */
queue_work_on(cpu, wg->handshake_receive_wq,
&per_cpu_ptr(wg->handshake_queue.worker, cpu)->work);
break;
}
case cpu_to_le32(MESSAGE_DATA):
PACKET_CB(skb)->ds = ip_tunnel_get_dsfield(ip_hdr(skb), skb);
wg_packet_consume_data(wg, skb);
break;
default:
WARN(1, "Non-exhaustive parsing of packet header lead to unknown packet type!\n");
goto err;
}
return;
err:
dev_kfree_skb(skb);
}
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