1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
|
/* SPDX-License-Identifier: GPL-2.0
*
* Copyright (C) 2015-2017 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*/
#include "cookie.h"
#include "peer.h"
#include "device.h"
#include "messages.h"
#include "ratelimiter.h"
#include "crypto/blake2s.h"
#include "crypto/chacha20poly1305.h"
#include <linux/jiffies.h>
#include <net/ipv6.h>
#include <crypto/algapi.h>
void cookie_checker_init(struct cookie_checker *checker, struct wireguard_device *wg)
{
init_rwsem(&checker->secret_lock);
checker->secret_birthdate = get_jiffies_64();
get_random_bytes(checker->secret, NOISE_HASH_LEN);
checker->device = wg;
}
enum { COOKIE_KEY_LABEL_LEN = 8 };
static const u8 mac1_key_label[COOKIE_KEY_LABEL_LEN] = "mac1----";
static const u8 cookie_key_label[COOKIE_KEY_LABEL_LEN] = "cookie--";
static void precompute_key(u8 key[NOISE_SYMMETRIC_KEY_LEN], const u8 pubkey[NOISE_PUBLIC_KEY_LEN], const u8 label[COOKIE_KEY_LABEL_LEN])
{
struct blake2s_state blake;
blake2s_init(&blake, NOISE_SYMMETRIC_KEY_LEN);
blake2s_update(&blake, label, COOKIE_KEY_LABEL_LEN);
blake2s_update(&blake, pubkey, NOISE_PUBLIC_KEY_LEN);
blake2s_final(&blake, key, NOISE_SYMMETRIC_KEY_LEN);
}
void cookie_checker_precompute_device_keys(struct cookie_checker *checker)
{
down_read(&checker->device->static_identity.lock);
if (likely(checker->device->static_identity.has_identity)) {
precompute_key(checker->cookie_encryption_key, checker->device->static_identity.static_public, cookie_key_label);
precompute_key(checker->message_mac1_key, checker->device->static_identity.static_public, mac1_key_label);
} else {
memset(checker->cookie_encryption_key, 0, NOISE_SYMMETRIC_KEY_LEN);
memset(checker->message_mac1_key, 0, NOISE_SYMMETRIC_KEY_LEN);
}
up_read(&checker->device->static_identity.lock);
}
void cookie_checker_precompute_peer_keys(struct wireguard_peer *peer)
{
precompute_key(peer->latest_cookie.cookie_decryption_key, peer->handshake.remote_static, cookie_key_label);
precompute_key(peer->latest_cookie.message_mac1_key, peer->handshake.remote_static, mac1_key_label);
}
void cookie_init(struct cookie *cookie)
{
memset(cookie, 0, sizeof(struct cookie));
init_rwsem(&cookie->lock);
}
static void compute_mac1(u8 mac1[COOKIE_LEN], const void *message, size_t len, const u8 key[NOISE_SYMMETRIC_KEY_LEN])
{
len = len - sizeof(struct message_macs) + offsetof(struct message_macs, mac1);
blake2s(mac1, message, key, COOKIE_LEN, len, NOISE_SYMMETRIC_KEY_LEN);
}
static void compute_mac2(u8 mac2[COOKIE_LEN], const void *message, size_t len, const u8 cookie[COOKIE_LEN])
{
len = len - sizeof(struct message_macs) + offsetof(struct message_macs, mac2);
blake2s(mac2, message, cookie, COOKIE_LEN, len, COOKIE_LEN);
}
static void make_cookie(u8 cookie[COOKIE_LEN], struct sk_buff *skb, struct cookie_checker *checker)
{
struct blake2s_state state;
if (!time_is_after_jiffies64(checker->secret_birthdate + COOKIE_SECRET_MAX_AGE)) {
down_write(&checker->secret_lock);
checker->secret_birthdate = get_jiffies_64();
get_random_bytes(checker->secret, NOISE_HASH_LEN);
up_write(&checker->secret_lock);
}
down_read(&checker->secret_lock);
blake2s_init_key(&state, COOKIE_LEN, checker->secret, NOISE_HASH_LEN);
if (skb->protocol == htons(ETH_P_IP))
blake2s_update(&state, (u8 *)&ip_hdr(skb)->saddr, sizeof(struct in_addr));
else if (skb->protocol == htons(ETH_P_IPV6))
blake2s_update(&state, (u8 *)&ipv6_hdr(skb)->saddr, sizeof(struct in6_addr));
blake2s_update(&state, (u8 *)&udp_hdr(skb)->source, sizeof(__be16));
blake2s_final(&state, cookie, COOKIE_LEN);
up_read(&checker->secret_lock);
}
enum cookie_mac_state cookie_validate_packet(struct cookie_checker *checker, struct sk_buff *skb, bool check_cookie)
{
u8 computed_mac[COOKIE_LEN];
u8 cookie[COOKIE_LEN];
enum cookie_mac_state ret;
struct message_macs *macs = (struct message_macs *)(skb->data + skb->len - sizeof(struct message_macs));
ret = INVALID_MAC;
compute_mac1(computed_mac, skb->data, skb->len, checker->message_mac1_key);
if (crypto_memneq(computed_mac, macs->mac1, COOKIE_LEN))
goto out;
ret = VALID_MAC_BUT_NO_COOKIE;
if (!check_cookie)
goto out;
make_cookie(cookie, skb, checker);
compute_mac2(computed_mac, skb->data, skb->len, cookie);
if (crypto_memneq(computed_mac, macs->mac2, COOKIE_LEN))
goto out;
ret = VALID_MAC_WITH_COOKIE_BUT_RATELIMITED;
if (!ratelimiter_allow(skb, dev_net(checker->device->dev)))
goto out;
ret = VALID_MAC_WITH_COOKIE;
out:
return ret;
}
void cookie_add_mac_to_packet(void *message, size_t len, struct wireguard_peer *peer)
{
struct message_macs *macs = (struct message_macs *)((u8 *)message + len - sizeof(struct message_macs));
down_write(&peer->latest_cookie.lock);
compute_mac1(macs->mac1, message, len, peer->latest_cookie.message_mac1_key);
memcpy(peer->latest_cookie.last_mac1_sent, macs->mac1, COOKIE_LEN);
peer->latest_cookie.have_sent_mac1 = true;
up_write(&peer->latest_cookie.lock);
down_read(&peer->latest_cookie.lock);
if (peer->latest_cookie.is_valid && time_is_after_jiffies64(peer->latest_cookie.birthdate + COOKIE_SECRET_MAX_AGE - COOKIE_SECRET_LATENCY))
compute_mac2(macs->mac2, message, len, peer->latest_cookie.cookie);
else
memset(macs->mac2, 0, COOKIE_LEN);
up_read(&peer->latest_cookie.lock);
}
void cookie_message_create(struct message_handshake_cookie *dst, struct sk_buff *skb, __le32 index, struct cookie_checker *checker)
{
struct message_macs *macs = (struct message_macs *)((u8 *)skb->data + skb->len - sizeof(struct message_macs));
u8 cookie[COOKIE_LEN];
dst->header.type = cpu_to_le32(MESSAGE_HANDSHAKE_COOKIE);
dst->receiver_index = index;
get_random_bytes_wait(dst->nonce, COOKIE_NONCE_LEN);
make_cookie(cookie, skb, checker);
xchacha20poly1305_encrypt(dst->encrypted_cookie, cookie, COOKIE_LEN, macs->mac1, COOKIE_LEN, dst->nonce, checker->cookie_encryption_key);
}
void cookie_message_consume(struct message_handshake_cookie *src, struct wireguard_device *wg)
{
u8 cookie[COOKIE_LEN];
struct index_hashtable_entry *entry;
bool ret;
entry = index_hashtable_lookup(&wg->index_hashtable, INDEX_HASHTABLE_HANDSHAKE | INDEX_HASHTABLE_KEYPAIR, src->receiver_index);
if (unlikely(!entry))
return;
down_read(&entry->peer->latest_cookie.lock);
if (unlikely(!entry->peer->latest_cookie.have_sent_mac1)) {
up_read(&entry->peer->latest_cookie.lock);
goto out;
}
ret = xchacha20poly1305_decrypt(cookie, src->encrypted_cookie, sizeof(src->encrypted_cookie), entry->peer->latest_cookie.last_mac1_sent, COOKIE_LEN, src->nonce, entry->peer->latest_cookie.cookie_decryption_key);
up_read(&entry->peer->latest_cookie.lock);
if (ret) {
down_write(&entry->peer->latest_cookie.lock);
memcpy(entry->peer->latest_cookie.cookie, cookie, COOKIE_LEN);
entry->peer->latest_cookie.birthdate = get_jiffies_64();
entry->peer->latest_cookie.is_valid = true;
entry->peer->latest_cookie.have_sent_mac1 = false;
up_write(&entry->peer->latest_cookie.lock);
} else
net_dbg_ratelimited("%s: Could not decrypt invalid cookie response\n", wg->dev->name);
out:
peer_put(entry->peer);
}
|
