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wg_noise: ensure non-zero'd handshakes have a valid local index 

As reported by: https://marc.info/?l=openbsd-bugs&m=161618496905444&w=2

In particular, when consuming an initiation, we don't generate the
index until creating the response (which is incorrect). If we attempt
to create an initiation between these processes, we drop any
outstanding handshake which in this case has index 0 as set when
consuming the initiation.

The fix attached is to generate the index when consuming the initiation
so that any spurious initiation creation can drop a valid index. The
patch also consolidates setting fields on the handshake.

Signed-off-by: Matt Dunwoodie <ncon@noconroy.net>
This commit is contained in:
Matt Dunwoodie 2021-03-22 01:02:54 +11:00 committed by Jason A. Donenfeld
parent 895a85337e
commit fbf76929c0
1 changed files with 3 additions and 4 deletions
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7
src/wg_noise.c
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@ -284,9 +284,6 @@ noise_consume_initiation(struct noise_local *l, struct noise_remote **rp,
NOISE_TIMESTAMP_LEN + NOISE_AUTHTAG_LEN, key, hs.hs_hash) != 0)
goto error;
hs.hs_state = CONSUMED_INITIATION;
hs.hs_local_index = 0;
hs.hs_remote_index = s_idx;
memcpy(hs.hs_e, ue, NOISE_PUBLIC_KEY_LEN);
/* We have successfully computed the same results, now we ensure that
@ -306,6 +303,9 @@ noise_consume_initiation(struct noise_local *l, struct noise_remote **rp,
/* Ok, we're happy to accept this initiation now */
noise_remote_handshake_index_drop(r);
hs.hs_state = CONSUMED_INITIATION;
hs.hs_local_index = noise_remote_handshake_index_get(r);
hs.hs_remote_index = s_idx;
r->r_handshake = hs;
*rp = r;
ret = 0;
@ -354,7 +354,6 @@ noise_create_response(struct noise_remote *r, uint32_t *s_idx, uint32_t *r_idx,
noise_msg_encrypt(en, NULL, 0, key, hs->hs_hash);
hs->hs_state = CREATED_RESPONSE;
hs->hs_local_index = noise_remote_handshake_index_get(r);
*r_idx = hs->hs_remote_index;
*s_idx = hs->hs_local_index;
ret = 0;