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mesh: Fix mesh SAE auth on low spec devices

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The mesh SAE auth often fails with master branch. By bisect I found
commit eb5fee0bf5 ('SAE: Add side-channel
protection to PWE derivation with ECC') causes this issue. This does not
mean the commit has a bug. This is just a CPU resource issue.

After the commit, sae_derive_pwe_ecc() spends 101(msec) on my PC (Intel
Atom N270 1.6GHz). But dot11RSNASAERetransPeriod is 40(msec). So
auth_sae_retransmit_timer() is always called and it can causes
continuous frame exchanges. Before the commit, it was 23(msec).

On the IEEE 802.11 spec, the default value of dot11RSNASAERetransPeriod
is defined as 40(msec). But it looks short because generally mesh
functionality will be used on low spec devices. Indeed Raspberry Pi B+
(ARM ARM1176JZF-S 700MHz) requires 287(msec) for new
sae_derive_pwe_ecc().

So this patch makes the default to 1000(msec) and makes it configurable.

This issue does not occur on infrastructure SAE because the
dot11RSNASAERetransPeriod is not used on it.

Signed-off-by: Masashi Honma <masashi.honma@gmail.com>
This commit is contained in:
Masashi Honma 2015-07-08 22:41:36 +09:00 • committed by Jouni Malinen
parent 3dfa519c32
commit ecd40fef74
7 changed files with 31 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

9
src/ap/ieee802_11.c
View file

@ -316,7 +316,6 @@ static void handle_auth_ft_finish(void *ctx, const u8 *dst, const u8 *bssid,
#ifdef CONFIG_SAE
#define dot11RSNASAERetransPeriod 40 /* msec */
#define dot11RSNASAESync 5 /* attempts */
@ -499,12 +498,14 @@ static void auth_sae_retransmit_timer(void *eloop_ctx, void *eloop_data)
switch (sta->sae->state) {
case SAE_COMMITTED:
ret = auth_sae_send_commit(hapd, sta, hapd->own_addr, 0);
eloop_register_timeout(0, dot11RSNASAERetransPeriod * 1000,
eloop_register_timeout(0,
hapd->dot11RSNASAERetransPeriod * 1000,
auth_sae_retransmit_timer, hapd, sta);
break;
case SAE_CONFIRMED:
ret = auth_sae_send_confirm(hapd, sta, hapd->own_addr);
eloop_register_timeout(0, dot11RSNASAERetransPeriod * 1000,
eloop_register_timeout(0,
hapd->dot11RSNASAERetransPeriod * 1000,
auth_sae_retransmit_timer, hapd, sta);
break;
default:
@ -530,7 +531,7 @@ static void sae_set_retransmit_timer(struct hostapd_data *hapd,
return;
eloop_cancel_timeout(auth_sae_retransmit_timer, hapd, sta);
eloop_register_timeout(0, dot11RSNASAERetransPeriod * 1000,
eloop_register_timeout(0, hapd->dot11RSNASAERetransPeriod * 1000,
auth_sae_retransmit_timer, hapd, sta);
}