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wireguard: noise: error out precomputed DH during handshake rather th…
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…an config

We precompute the static-static ECDH during configuration time, in order
to save an expensive computation later when receiving network packets.
However, not all ECDH computations yield a contributory result. Prior,
we were just not letting those peers be added to the interface. However,
this creates a strange inconsistency, since it was still possible to add
other weird points, like a valid public key plus a low-order point, and,
like points that result in zeros, a handshake would not complete. In
order to make the behavior more uniform and less surprising, simply
allow all peers to be added. Then, we'll error out later when doing the
crypto if there's an issue. This also adds more separation between the
crypto layer and the configuration layer.

Discussed-with: Mathias Hall-Andersen <[email protected]>
Signed-off-by: Jason A. Donenfeld <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
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@zx2c4 @davem330
zx2c4 authored and davem330 committed Mar 19, 2020
1 parent 2b8765c commit 11a7686
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Showing 5 changed files with 49 additions and 48 deletions.
8 changes: 2 additions & 6 deletions drivers/net/wireguard/netlink.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -411,11 +411,7 @@ static int set_peer(struct wg_device *wg, struct nlattr **attrs)

peer = wg_peer_create(wg, public_key, preshared_key);
if (IS_ERR(peer)) {
/* Similar to the above, if the key is invalid, we skip
* it without fanfare, so that services don't need to
* worry about doing key validation themselves.
*/
ret = PTR_ERR(peer) == -EKEYREJECTED ? 0 : PTR_ERR(peer);
ret = PTR_ERR(peer);
peer = NULL;
goto out;
}
Expand Down Expand Up @@ -569,7 +565,7 @@ static int wg_set_device(struct sk_buff *skb, struct genl_info *info)
private_key);
list_for_each_entry_safe(peer, temp, &wg->peer_list,
peer_list) {
BUG_ON(!wg_noise_precompute_static_static(peer));
wg_noise_precompute_static_static(peer);
wg_noise_expire_current_peer_keypairs(peer);
}
wg_cookie_checker_precompute_device_keys(&wg->cookie_checker);
Expand Down
55 changes: 29 additions & 26 deletions drivers/net/wireguard/noise.c
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Original file line number Diff line number Diff line change
Expand Up @@ -44,32 +44,23 @@ void __init wg_noise_init(void)
}

/* Must hold peer->handshake.static_identity->lock */
bool wg_noise_precompute_static_static(struct wg_peer *peer)
void wg_noise_precompute_static_static(struct wg_peer *peer)
{
bool ret;

down_write(&peer->handshake.lock);
if (peer->handshake.static_identity->has_identity) {
ret = curve25519(
peer->handshake.precomputed_static_static,
if (!peer->handshake.static_identity->has_identity ||
!curve25519(peer->handshake.precomputed_static_static,
peer->handshake.static_identity->static_private,
peer->handshake.remote_static);
} else {
u8 empty[NOISE_PUBLIC_KEY_LEN] = { 0 };

ret = curve25519(empty, empty, peer->handshake.remote_static);
peer->handshake.remote_static))
memset(peer->handshake.precomputed_static_static, 0,
NOISE_PUBLIC_KEY_LEN);
}
up_write(&peer->handshake.lock);
return ret;
}

bool wg_noise_handshake_init(struct noise_handshake *handshake,
struct noise_static_identity *static_identity,
const u8 peer_public_key[NOISE_PUBLIC_KEY_LEN],
const u8 peer_preshared_key[NOISE_SYMMETRIC_KEY_LEN],
struct wg_peer *peer)
void wg_noise_handshake_init(struct noise_handshake *handshake,
struct noise_static_identity *static_identity,
const u8 peer_public_key[NOISE_PUBLIC_KEY_LEN],
const u8 peer_preshared_key[NOISE_SYMMETRIC_KEY_LEN],
struct wg_peer *peer)
{
memset(handshake, 0, sizeof(*handshake));
init_rwsem(&handshake->lock);
Expand All @@ -81,7 +72,7 @@ bool wg_noise_handshake_init(struct noise_handshake *handshake,
NOISE_SYMMETRIC_KEY_LEN);
handshake->static_identity = static_identity;
handshake->state = HANDSHAKE_ZEROED;
return wg_noise_precompute_static_static(peer);
wg_noise_precompute_static_static(peer);
}

static void handshake_zero(struct noise_handshake *handshake)
Expand Down Expand Up @@ -403,6 +394,19 @@ static bool __must_check mix_dh(u8 chaining_key[NOISE_HASH_LEN],
return true;
}

static bool __must_check mix_precomputed_dh(u8 chaining_key[NOISE_HASH_LEN],
u8 key[NOISE_SYMMETRIC_KEY_LEN],
const u8 precomputed[NOISE_PUBLIC_KEY_LEN])
{
static u8 zero_point[NOISE_PUBLIC_KEY_LEN];
if (unlikely(!crypto_memneq(precomputed, zero_point, NOISE_PUBLIC_KEY_LEN)))
return false;
kdf(chaining_key, key, NULL, precomputed, NOISE_HASH_LEN,
NOISE_SYMMETRIC_KEY_LEN, 0, NOISE_PUBLIC_KEY_LEN,
chaining_key);
return true;
}

static void mix_hash(u8 hash[NOISE_HASH_LEN], const u8 *src, size_t src_len)
{
struct blake2s_state blake;
Expand Down Expand Up @@ -531,10 +535,9 @@ wg_noise_handshake_create_initiation(struct message_handshake_initiation *dst,
NOISE_PUBLIC_KEY_LEN, key, handshake->hash);

/* ss */
kdf(handshake->chaining_key, key, NULL,
handshake->precomputed_static_static, NOISE_HASH_LEN,
NOISE_SYMMETRIC_KEY_LEN, 0, NOISE_PUBLIC_KEY_LEN,
handshake->chaining_key);
if (!mix_precomputed_dh(handshake->chaining_key, key,
handshake->precomputed_static_static))
goto out;

/* {t} */
tai64n_now(timestamp);
Expand Down Expand Up @@ -595,9 +598,9 @@ wg_noise_handshake_consume_initiation(struct message_handshake_initiation *src,
handshake = &peer->handshake;

/* ss */
kdf(chaining_key, key, NULL, handshake->precomputed_static_static,
NOISE_HASH_LEN, NOISE_SYMMETRIC_KEY_LEN, 0, NOISE_PUBLIC_KEY_LEN,
chaining_key);
if (!mix_precomputed_dh(chaining_key, key,
handshake->precomputed_static_static))
goto out;

/* {t} */
if (!message_decrypt(t, src->encrypted_timestamp,
Expand Down
12 changes: 6 additions & 6 deletions drivers/net/wireguard/noise.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -94,11 +94,11 @@ struct noise_handshake {
struct wg_device;

void wg_noise_init(void);
bool wg_noise_handshake_init(struct noise_handshake *handshake,
struct noise_static_identity *static_identity,
const u8 peer_public_key[NOISE_PUBLIC_KEY_LEN],
const u8 peer_preshared_key[NOISE_SYMMETRIC_KEY_LEN],
struct wg_peer *peer);
void wg_noise_handshake_init(struct noise_handshake *handshake,
struct noise_static_identity *static_identity,
const u8 peer_public_key[NOISE_PUBLIC_KEY_LEN],
const u8 peer_preshared_key[NOISE_SYMMETRIC_KEY_LEN],
struct wg_peer *peer);
void wg_noise_handshake_clear(struct noise_handshake *handshake);
static inline void wg_noise_reset_last_sent_handshake(atomic64_t *handshake_ns)
{
Expand All @@ -116,7 +116,7 @@ void wg_noise_expire_current_peer_keypairs(struct wg_peer *peer);
void wg_noise_set_static_identity_private_key(
struct noise_static_identity *static_identity,
const u8 private_key[NOISE_PUBLIC_KEY_LEN]);
bool wg_noise_precompute_static_static(struct wg_peer *peer);
void wg_noise_precompute_static_static(struct wg_peer *peer);

bool
wg_noise_handshake_create_initiation(struct message_handshake_initiation *dst,
Expand Down
7 changes: 2 additions & 5 deletions drivers/net/wireguard/peer.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,11 +34,8 @@ struct wg_peer *wg_peer_create(struct wg_device *wg,
return ERR_PTR(ret);
peer->device = wg;

if (!wg_noise_handshake_init(&peer->handshake, &wg->static_identity,
public_key, preshared_key, peer)) {
ret = -EKEYREJECTED;
goto err_1;
}
wg_noise_handshake_init(&peer->handshake, &wg->static_identity,
public_key, preshared_key, peer);
if (dst_cache_init(&peer->endpoint_cache, GFP_KERNEL))
goto err_1;
if (wg_packet_queue_init(&peer->tx_queue, wg_packet_tx_worker, false,
Expand Down
15 changes: 10 additions & 5 deletions tools/testing/selftests/wireguard/netns.sh
View file
Original file line number Diff line number Diff line change
Expand Up @@ -527,11 +527,16 @@ n0 wg set wg0 peer "$pub2" allowed-ips 0.0.0.0/0
n0 wg set wg0 peer "$pub2" allowed-ips ::/0,1700::/111,5000::/4,e000::/37,9000::/75
n0 wg set wg0 peer "$pub2" allowed-ips ::/0
n0 wg set wg0 peer "$pub2" remove
low_order_points=( AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA= AQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA= 4Ot6fDtBuK4WVuP68Z/EatoJjeucMrH9hmIFFl9JuAA= X5yVvKNQjCSx0LFVnIPvWwREXMRYHI6G2CJO3dCfEVc= 7P///////////////////////////////////////38= 7f///////////////////////////////////////38= 7v///////////////////////////////////////38= )
n0 wg set wg0 private-key /dev/null ${low_order_points[@]/#/peer }
[[ -z $(n0 wg show wg0 peers) ]]
n0 wg set wg0 private-key <(echo "$key1") ${low_order_points[@]/#/peer }
[[ -z $(n0 wg show wg0 peers) ]]
for low_order_point in AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA= AQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA= 4Ot6fDtBuK4WVuP68Z/EatoJjeucMrH9hmIFFl9JuAA= X5yVvKNQjCSx0LFVnIPvWwREXMRYHI6G2CJO3dCfEVc= 7P///////////////////////////////////////38= 7f///////////////////////////////////////38= 7v///////////////////////////////////////38=; do
n0 wg set wg0 peer "$low_order_point" persistent-keepalive 1 endpoint 127.0.0.1:1111
done
[[ -n $(n0 wg show wg0 peers) ]]
exec 4< <(n0 ncat -l -u -p 1111)
ncat_pid=$!
waitncatudp $netns0 $ncat_pid
ip0 link set wg0 up
! read -r -n 1 -t 2 <&4 || false
kill $ncat_pid
ip0 link del wg0

declare -A objects
Expand Down

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