Commit 11a7686a authored by Jason A. Donenfeld's avatar Jason A. Donenfeld Committed by David S. Miller
Browse files

wireguard: noise: error out precomputed DH during handshake rather than 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 <mathias@hall-andersen.dk>
Signed-off-by: default avatarJason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 2b8765c5

drivers/net/wireguard/netlink.c

+2 −6
Original line number Diff line number Diff line
@@ -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;

		}
@@ -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);

drivers/net/wireguard/noise.c

+29 −26
Original line number Diff line number Diff line
@@ -44,28 +44,19 @@ 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,

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],
@@ -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)
@@ -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;
@@ -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);
@@ -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,

drivers/net/wireguard/noise.h

+6 −6
Original line number Diff line number Diff line
@@ -94,7 +94,7 @@ struct noise_handshake { 
struct wg_device;



void wg_noise_init(void);

bool wg_noise_handshake_init(struct noise_handshake *handshake,

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],
@@ -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,

drivers/net/wireguard/peer.c

+2 −5
Original line number Diff line number Diff line
@@ -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,

tools/testing/selftests/wireguard/netns.sh

+10 −5
Original line number Diff line number Diff line
@@ -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

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