target/linux/generic/backport-5.4/080-wireguard-0103-wireguard-noise-read-preshared-key-while-taking-lock.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: "Jason A. Donenfeld" <Jason@zx2c4.com>
   3 Date: Tue, 19 May 2020 22:49:28 -0600
   4 Subject: [PATCH] wireguard: noise: read preshared key while taking lock
   5
   6 commit bc67d371256f5c47d824e2eec51e46c8d62d022e upstream.
   7
   8 Prior we read the preshared key after dropping the handshake lock, which
   9 isn't an actual crypto issue if it races, but it's still not quite
  10 correct. So copy that part of the state into a temporary like we do with
  11 the rest of the handshake state variables. Then we can release the lock,
  12 operate on the temporary, and zero it out at the end of the function. In
  13 performance tests, the impact of this was entirely unnoticable, probably
  14 because those bytes are coming from the same cacheline as other things
  15 that are being copied out in the same manner.
  16
  17 Reported-by: Matt Dunwoodie <ncon@noconroy.net>
  18 Fixes: e7096c131e51 ("net: WireGuard secure network tunnel")
  19 Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
  20 Signed-off-by: David S. Miller <davem@davemloft.net>
  21 Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
  22 ---
  23  drivers/net/wireguard/noise.c | 6 +++++-
  24  1 file changed, 5 insertions(+), 1 deletion(-)
  25
  26 --- a/drivers/net/wireguard/noise.c
  27 +++ b/drivers/net/wireguard/noise.c
  28 @@ -715,6 +715,7 @@ wg_noise_handshake_consume_response(stru
  29         u8 e[NOISE_PUBLIC_KEY_LEN];
  30         u8 ephemeral_private[NOISE_PUBLIC_KEY_LEN];
  31         u8 static_private[NOISE_PUBLIC_KEY_LEN];
  32 +       u8 preshared_key[NOISE_SYMMETRIC_KEY_LEN];
  33
  34         down_read(&wg->static_identity.lock);
  35
  36 @@ -733,6 +734,8 @@ wg_noise_handshake_consume_response(stru
  37         memcpy(chaining_key, handshake->chaining_key, NOISE_HASH_LEN);
  38         memcpy(ephemeral_private, handshake->ephemeral_private,
  39                NOISE_PUBLIC_KEY_LEN);
  40 +       memcpy(preshared_key, handshake->preshared_key,
  41 +              NOISE_SYMMETRIC_KEY_LEN);
  42         up_read(&handshake->lock);
  43
  44         if (state != HANDSHAKE_CREATED_INITIATION)
  45 @@ -750,7 +753,7 @@ wg_noise_handshake_consume_response(stru
  46                 goto fail;
  47
  48         /* psk */
  49 -       mix_psk(chaining_key, hash, key, handshake->preshared_key);
  50 +       mix_psk(chaining_key, hash, key, preshared_key);
  51
  52         /* {} */
  53         if (!message_decrypt(NULL, src->encrypted_nothing,
  54 @@ -783,6 +786,7 @@ out:
  55         memzero_explicit(chaining_key, NOISE_HASH_LEN);
  56         memzero_explicit(ephemeral_private, NOISE_PUBLIC_KEY_LEN);
  57         memzero_explicit(static_private, NOISE_PUBLIC_KEY_LEN);
  58 +       memzero_explicit(preshared_key, NOISE_SYMMETRIC_KEY_LEN);
  59         up_read(&wg->static_identity.lock);
  60         return ret_peer;
  61  }