From: "Jason A. Donenfeld" Jason@zx2c4.com
[ Upstream commit bc67d371256f5c47d824e2eec51e46c8d62d022e ]
Prior we read the preshared key after dropping the handshake lock, which isn't an actual crypto issue if it races, but it's still not quite correct. So copy that part of the state into a temporary like we do with the rest of the handshake state variables. Then we can release the lock, operate on the temporary, and zero it out at the end of the function. In performance tests, the impact of this was entirely unnoticable, probably because those bytes are coming from the same cacheline as other things that are being copied out in the same manner.
Reported-by: Matt Dunwoodie ncon@noconroy.net Fixes: e7096c131e51 ("net: WireGuard secure network tunnel") Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/wireguard/noise.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/drivers/net/wireguard/noise.c +++ b/drivers/net/wireguard/noise.c @@ -715,6 +715,7 @@ wg_noise_handshake_consume_response(stru u8 e[NOISE_PUBLIC_KEY_LEN]; u8 ephemeral_private[NOISE_PUBLIC_KEY_LEN]; u8 static_private[NOISE_PUBLIC_KEY_LEN]; + u8 preshared_key[NOISE_SYMMETRIC_KEY_LEN];
down_read(&wg->static_identity.lock);
@@ -733,6 +734,8 @@ wg_noise_handshake_consume_response(stru memcpy(chaining_key, handshake->chaining_key, NOISE_HASH_LEN); memcpy(ephemeral_private, handshake->ephemeral_private, NOISE_PUBLIC_KEY_LEN); + memcpy(preshared_key, handshake->preshared_key, + NOISE_SYMMETRIC_KEY_LEN); up_read(&handshake->lock);
if (state != HANDSHAKE_CREATED_INITIATION) @@ -750,7 +753,7 @@ wg_noise_handshake_consume_response(stru goto fail;
/* psk */ - mix_psk(chaining_key, hash, key, handshake->preshared_key); + mix_psk(chaining_key, hash, key, preshared_key);
/* {} */ if (!message_decrypt(NULL, src->encrypted_nothing, @@ -783,6 +786,7 @@ out: memzero_explicit(chaining_key, NOISE_HASH_LEN); memzero_explicit(ephemeral_private, NOISE_PUBLIC_KEY_LEN); memzero_explicit(static_private, NOISE_PUBLIC_KEY_LEN); + memzero_explicit(preshared_key, NOISE_SYMMETRIC_KEY_LEN); up_read(&wg->static_identity.lock); return ret_peer; }