diff options
Diffstat (limited to 'drivers/net/wireguard/cookie.c')
| -rw-r--r-- | drivers/net/wireguard/cookie.c | 236 |
1 files changed, 236 insertions, 0 deletions
diff --git a/drivers/net/wireguard/cookie.c b/drivers/net/wireguard/cookie.c new file mode 100644 index 0000000000..4956f0499c --- /dev/null +++ b/drivers/net/wireguard/cookie.c @@ -0,0 +1,236 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2015-2019 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 "timers.h" + +#include <crypto/blake2s.h> +#include <crypto/chacha20poly1305.h> + +#include <net/ipv6.h> +#include <crypto/algapi.h> + +void wg_cookie_checker_init(struct cookie_checker *checker, + struct wg_device *wg) +{ + init_rwsem(&checker->secret_lock); + checker->secret_birthdate = ktime_get_coarse_boottime_ns(); + 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); +} + +/* Must hold peer->handshake.static_identity->lock */ +void wg_cookie_checker_precompute_device_keys(struct cookie_checker *checker) +{ + 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); + } +} + +void wg_cookie_checker_precompute_peer_keys(struct wg_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 wg_cookie_init(struct cookie *cookie) +{ + memset(cookie, 0, sizeof(*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 (wg_birthdate_has_expired(checker->secret_birthdate, + COOKIE_SECRET_MAX_AGE)) { + down_write(&checker->secret_lock); + checker->secret_birthdate = ktime_get_coarse_boottime_ns(); + 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); + + up_read(&checker->secret_lock); +} + +enum cookie_mac_state wg_cookie_validate_packet(struct cookie_checker *checker, + struct sk_buff *skb, + bool check_cookie) +{ + struct message_macs *macs = (struct message_macs *) + (skb->data + skb->len - sizeof(*macs)); + enum cookie_mac_state ret; + u8 computed_mac[COOKIE_LEN]; + u8 cookie[COOKIE_LEN]; + + 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 (!wg_ratelimiter_allow(skb, dev_net(checker->device->dev))) + goto out; + + ret = VALID_MAC_WITH_COOKIE; + +out: + return ret; +} + +void wg_cookie_add_mac_to_packet(void *message, size_t len, + struct wg_peer *peer) +{ + struct message_macs *macs = (struct message_macs *) + ((u8 *)message + len - sizeof(*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 && + !wg_birthdate_has_expired(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 wg_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(*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 wg_cookie_message_consume(struct message_handshake_cookie *src, + struct wg_device *wg) +{ + struct wg_peer *peer = NULL; + u8 cookie[COOKIE_LEN]; + bool ret; + + if (unlikely(!wg_index_hashtable_lookup(wg->index_hashtable, + INDEX_HASHTABLE_HANDSHAKE | + INDEX_HASHTABLE_KEYPAIR, + src->receiver_index, &peer))) + return; + + down_read(&peer->latest_cookie.lock); + if (unlikely(!peer->latest_cookie.have_sent_mac1)) { + up_read(&peer->latest_cookie.lock); + goto out; + } + ret = xchacha20poly1305_decrypt( + cookie, src->encrypted_cookie, sizeof(src->encrypted_cookie), + peer->latest_cookie.last_mac1_sent, COOKIE_LEN, src->nonce, + peer->latest_cookie.cookie_decryption_key); + up_read(&peer->latest_cookie.lock); + + if (ret) { + down_write(&peer->latest_cookie.lock); + memcpy(peer->latest_cookie.cookie, cookie, COOKIE_LEN); + peer->latest_cookie.birthdate = ktime_get_coarse_boottime_ns(); + peer->latest_cookie.is_valid = true; + peer->latest_cookie.have_sent_mac1 = false; + up_write(&peer->latest_cookie.lock); + } else { + net_dbg_ratelimited("%s: Could not decrypt invalid cookie response\n", + wg->dev->name); + } + +out: + wg_peer_put(peer); +} |