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Work around SNonce updates on EAPOL-Key 1/4 retransmission

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Some deployed supplicants update their SNonce for every receive
EAPOL-Key message 1/4 even when these messages happen during the
same 4-way handshake. Furthermore, some of these supplicants fail
to use the first SNonce that they sent and derive an incorrect PTK
using another SNonce that does not match with what the authenticator
is using from the first received message 2/4. This results in
failed 4-way handshake whenever the EAPOL-Key 1/4 retransmission
timeout is reached. The timeout for the first retry is fixed to
100 ms in the IEEE 802.11 standard and that seems to be short
enough to make it difficult for some stations to get the response
out before retransmission.

Work around this issue by increasing the initial EAPOL-Key 1/4
timeout by 1000 ms (i.e., total timeout of 1100 ms) if the station
acknowledges reception of the EAPOL-Key frame. If the driver does
not indicate TX status for EAPOL frames, use longer initial
timeout (1000 ms) unconditionally.
This commit is contained in:
Jouni Malinen 2011-03-29 17:39:12 +03:00 • committed by Jouni Malinen
parent 2fee890af7
commit e4bf4db907
5 changed files with 56 additions and 1 deletions
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10
src/ap/ieee802_1x.c
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@ -1770,6 +1770,16 @@ int ieee802_1x_tx_status(struct hostapd_data *hapd, struct sta_info *sta,
MAC2STR(sta->addr), xhdr->version, xhdr->type,
be_to_host16(xhdr->length), ack);
if (xhdr->type == IEEE802_1X_TYPE_EAPOL_KEY &&
pos + sizeof(struct wpa_eapol_key) <= buf + len) {
const struct wpa_eapol_key *wpa;
wpa = (const struct wpa_eapol_key *) pos;
if (wpa->type == EAPOL_KEY_TYPE_RSN ||
wpa->type == EAPOL_KEY_TYPE_WPA)
wpa_auth_eapol_key_tx_status(hapd->wpa_auth,
sta->wpa_sm, ack);
}
/* EAPOL EAP-Packet packets are eventually re-sent by either Supplicant
* or Authenticator state machines, but EAPOL-Key packets are not
* retransmitted in case of failure. Try to re-sent failed EAPOL-Key