237 lines
7.0 KiB
C
237 lines
7.0 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 "cookie.h"
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#include "peer.h"
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#include "device.h"
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#include "messages.h"
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#include "ratelimiter.h"
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#include "timers.h"
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#include <crypto/blake2s.h>
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#include <crypto/chacha20poly1305.h>
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#include <net/ipv6.h>
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#include <crypto/algapi.h>
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void wg_cookie_checker_init(struct cookie_checker *checker,
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struct wg_device *wg)
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{
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init_rwsem(&checker->secret_lock);
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checker->secret_birthdate = ktime_get_coarse_boottime_ns();
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get_random_bytes(checker->secret, NOISE_HASH_LEN);
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checker->device = wg;
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}
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enum { COOKIE_KEY_LABEL_LEN = 8 };
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static const u8 mac1_key_label[COOKIE_KEY_LABEL_LEN] = "mac1----";
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static const u8 cookie_key_label[COOKIE_KEY_LABEL_LEN] = "cookie--";
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static void precompute_key(u8 key[NOISE_SYMMETRIC_KEY_LEN],
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const u8 pubkey[NOISE_PUBLIC_KEY_LEN],
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const u8 label[COOKIE_KEY_LABEL_LEN])
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{
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struct blake2s_state blake;
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blake2s_init(&blake, NOISE_SYMMETRIC_KEY_LEN);
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blake2s_update(&blake, label, COOKIE_KEY_LABEL_LEN);
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blake2s_update(&blake, pubkey, NOISE_PUBLIC_KEY_LEN);
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blake2s_final(&blake, key);
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}
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/* Must hold peer->handshake.static_identity->lock */
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void wg_cookie_checker_precompute_device_keys(struct cookie_checker *checker)
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{
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if (likely(checker->device->static_identity.has_identity)) {
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precompute_key(checker->cookie_encryption_key,
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checker->device->static_identity.static_public,
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cookie_key_label);
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precompute_key(checker->message_mac1_key,
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checker->device->static_identity.static_public,
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mac1_key_label);
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} else {
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memset(checker->cookie_encryption_key, 0,
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NOISE_SYMMETRIC_KEY_LEN);
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memset(checker->message_mac1_key, 0, NOISE_SYMMETRIC_KEY_LEN);
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}
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}
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void wg_cookie_checker_precompute_peer_keys(struct wg_peer *peer)
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{
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precompute_key(peer->latest_cookie.cookie_decryption_key,
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peer->handshake.remote_static, cookie_key_label);
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precompute_key(peer->latest_cookie.message_mac1_key,
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peer->handshake.remote_static, mac1_key_label);
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}
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void wg_cookie_init(struct cookie *cookie)
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{
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memset(cookie, 0, sizeof(*cookie));
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init_rwsem(&cookie->lock);
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}
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static void compute_mac1(u8 mac1[COOKIE_LEN], const void *message, size_t len,
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const u8 key[NOISE_SYMMETRIC_KEY_LEN])
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{
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len = len - sizeof(struct message_macs) +
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offsetof(struct message_macs, mac1);
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blake2s(mac1, message, key, COOKIE_LEN, len, NOISE_SYMMETRIC_KEY_LEN);
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}
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static void compute_mac2(u8 mac2[COOKIE_LEN], const void *message, size_t len,
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const u8 cookie[COOKIE_LEN])
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{
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len = len - sizeof(struct message_macs) +
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offsetof(struct message_macs, mac2);
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blake2s(mac2, message, cookie, COOKIE_LEN, len, COOKIE_LEN);
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}
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static void make_cookie(u8 cookie[COOKIE_LEN], struct sk_buff *skb,
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struct cookie_checker *checker)
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{
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struct blake2s_state state;
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if (wg_birthdate_has_expired(checker->secret_birthdate,
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COOKIE_SECRET_MAX_AGE)) {
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down_write(&checker->secret_lock);
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checker->secret_birthdate = ktime_get_coarse_boottime_ns();
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get_random_bytes(checker->secret, NOISE_HASH_LEN);
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up_write(&checker->secret_lock);
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}
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down_read(&checker->secret_lock);
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blake2s_init_key(&state, COOKIE_LEN, checker->secret, NOISE_HASH_LEN);
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if (skb->protocol == htons(ETH_P_IP))
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blake2s_update(&state, (u8 *)&ip_hdr(skb)->saddr,
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sizeof(struct in_addr));
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else if (skb->protocol == htons(ETH_P_IPV6))
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blake2s_update(&state, (u8 *)&ipv6_hdr(skb)->saddr,
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sizeof(struct in6_addr));
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blake2s_update(&state, (u8 *)&udp_hdr(skb)->source, sizeof(__be16));
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blake2s_final(&state, cookie);
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up_read(&checker->secret_lock);
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}
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enum cookie_mac_state wg_cookie_validate_packet(struct cookie_checker *checker,
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struct sk_buff *skb,
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bool check_cookie)
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{
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struct message_macs *macs = (struct message_macs *)
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(skb->data + skb->len - sizeof(*macs));
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enum cookie_mac_state ret;
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u8 computed_mac[COOKIE_LEN];
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u8 cookie[COOKIE_LEN];
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ret = INVALID_MAC;
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compute_mac1(computed_mac, skb->data, skb->len,
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checker->message_mac1_key);
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if (crypto_memneq(computed_mac, macs->mac1, COOKIE_LEN))
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goto out;
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ret = VALID_MAC_BUT_NO_COOKIE;
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if (!check_cookie)
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goto out;
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make_cookie(cookie, skb, checker);
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compute_mac2(computed_mac, skb->data, skb->len, cookie);
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if (crypto_memneq(computed_mac, macs->mac2, COOKIE_LEN))
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goto out;
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ret = VALID_MAC_WITH_COOKIE_BUT_RATELIMITED;
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if (!wg_ratelimiter_allow(skb, dev_net(checker->device->dev)))
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goto out;
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ret = VALID_MAC_WITH_COOKIE;
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out:
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return ret;
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}
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void wg_cookie_add_mac_to_packet(void *message, size_t len,
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struct wg_peer *peer)
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{
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struct message_macs *macs = (struct message_macs *)
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((u8 *)message + len - sizeof(*macs));
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down_write(&peer->latest_cookie.lock);
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compute_mac1(macs->mac1, message, len,
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peer->latest_cookie.message_mac1_key);
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memcpy(peer->latest_cookie.last_mac1_sent, macs->mac1, COOKIE_LEN);
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peer->latest_cookie.have_sent_mac1 = true;
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up_write(&peer->latest_cookie.lock);
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down_read(&peer->latest_cookie.lock);
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if (peer->latest_cookie.is_valid &&
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!wg_birthdate_has_expired(peer->latest_cookie.birthdate,
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COOKIE_SECRET_MAX_AGE - COOKIE_SECRET_LATENCY))
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compute_mac2(macs->mac2, message, len,
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peer->latest_cookie.cookie);
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else
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memset(macs->mac2, 0, COOKIE_LEN);
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up_read(&peer->latest_cookie.lock);
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}
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void wg_cookie_message_create(struct message_handshake_cookie *dst,
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struct sk_buff *skb, __le32 index,
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struct cookie_checker *checker)
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{
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struct message_macs *macs = (struct message_macs *)
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((u8 *)skb->data + skb->len - sizeof(*macs));
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u8 cookie[COOKIE_LEN];
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dst->header.type = cpu_to_le32(MESSAGE_HANDSHAKE_COOKIE);
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dst->receiver_index = index;
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get_random_bytes_wait(dst->nonce, COOKIE_NONCE_LEN);
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make_cookie(cookie, skb, checker);
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xchacha20poly1305_encrypt(dst->encrypted_cookie, cookie, COOKIE_LEN,
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macs->mac1, COOKIE_LEN, dst->nonce,
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checker->cookie_encryption_key);
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}
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void wg_cookie_message_consume(struct message_handshake_cookie *src,
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struct wg_device *wg)
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{
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struct wg_peer *peer = NULL;
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u8 cookie[COOKIE_LEN];
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bool ret;
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if (unlikely(!wg_index_hashtable_lookup(wg->index_hashtable,
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INDEX_HASHTABLE_HANDSHAKE |
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INDEX_HASHTABLE_KEYPAIR,
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src->receiver_index, &peer)))
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return;
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down_read(&peer->latest_cookie.lock);
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if (unlikely(!peer->latest_cookie.have_sent_mac1)) {
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up_read(&peer->latest_cookie.lock);
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goto out;
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}
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ret = xchacha20poly1305_decrypt(
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cookie, src->encrypted_cookie, sizeof(src->encrypted_cookie),
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peer->latest_cookie.last_mac1_sent, COOKIE_LEN, src->nonce,
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peer->latest_cookie.cookie_decryption_key);
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up_read(&peer->latest_cookie.lock);
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if (ret) {
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down_write(&peer->latest_cookie.lock);
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memcpy(peer->latest_cookie.cookie, cookie, COOKIE_LEN);
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peer->latest_cookie.birthdate = ktime_get_coarse_boottime_ns();
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peer->latest_cookie.is_valid = true;
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peer->latest_cookie.have_sent_mac1 = false;
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up_write(&peer->latest_cookie.lock);
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} else {
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net_dbg_ratelimited("%s: Could not decrypt invalid cookie response\n",
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wg->dev->name);
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}
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out:
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wg_peer_put(peer);
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}
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