From 93de2a6a4b91b72607136dd656edf03fb399d27f Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 23 Sep 2026 09:37:21 -0700 Subject: KVM: SEV: Do cache maintenance on the source VM during intra-host migration Manually perform cache maintenance on the source VM during intra-host migration to ensure no stale data is left in CPU caches after the VM is destroyed. Because the source VM is "converted" to a non-SEV VM, KVM's memory reclaim flows won't trigger cache maintenance, e.g. when all guest memory is reclaimed in response to detaching from the mmu_notifier. Note, relying on the destination VM to do cache maintenance isn't an option as KVM doesn't require identical guest memory configurations, i.e. the source VM may have access to memory that the destination VM does not. Enforcing equivalent memory configurations is infeasible, as it would require a *deep* comparison of memslots, e.g. to verify that not only are the memslot identical, but what the memslots point at is also identical. Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration") Cc: stable@vger.kernel.org Reported-by: Stefan Teodorescu Signed-off-by: Sean Christopherson Message-ID: <20260923163721.1584779-3-seanjc@google.com> Signed-off-by: Paolo Bonzini --- drivers/net/wireguard/cookie.c | 236 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 236 insertions(+) create mode 100644 drivers/net/wireguard/cookie.c (limited to 'drivers/net/wireguard/cookie.c') diff --git a/drivers/net/wireguard/cookie.c b/drivers/net/wireguard/cookie.c new file mode 100644 index 000000000..08731b3fa --- /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 . All Rights Reserved. + */ + +#include "cookie.h" +#include "peer.h" +#include "device.h" +#include "messages.h" +#include "ratelimiter.h" +#include "timers.h" + +#include +#include +#include + +#include + +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] __nonstring = "mac1----"; +static const u8 cookie_key_label[COOKIE_KEY_LABEL_LEN] __nonstring = "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_ctx 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(key, NOISE_SYMMETRIC_KEY_LEN, message, len, mac1, COOKIE_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(cookie, COOKIE_LEN, message, len, mac2, COOKIE_LEN); +} + +static void make_cookie(u8 cookie[COOKIE_LEN], struct sk_buff *skb, + struct cookie_checker *checker) +{ + struct blake2s_ctx blake; + + 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(&blake, COOKIE_LEN, checker->secret, NOISE_HASH_LEN); + if (skb->protocol == htons(ETH_P_IP)) + blake2s_update(&blake, (u8 *)&ip_hdr(skb)->saddr, + sizeof(struct in_addr)); + else if (skb->protocol == htons(ETH_P_IPV6)) + blake2s_update(&blake, (u8 *)&ipv6_hdr(skb)->saddr, + sizeof(struct in6_addr)); + blake2s_update(&blake, (u8 *)&udp_hdr(skb)->source, sizeof(__be16)); + blake2s_final(&blake, 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); +} -- cgit v1.3.1