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Enforce that IEEE 802.1X EAPOL-Key Replay Counter increases

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While this should not happen in practical use cases,
wpa_get_ntp_timestamp() could return the same value when called twice in
a row quickly. Work around that case by enforcing a new Replay Counter
value based on stored last value.

Signed-off-by: Jouni Malinen <j@w1.fi>
This commit is contained in:
Jouni Malinen 2019-05-04 19:17:45 +03:00
parent 1cefd89b37
commit de94be0acd
2 changed files with 17 additions and 0 deletions
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2
src/ap/hostapd.h
View file

@ -384,6 +384,8 @@ struct hostapd_data {
unsigned int num_backlogged_sta;
unsigned int airtime_weight;
#endif /* CONFIG_AIRTIME_POLICY */
u8 last_1x_eapol_key_replay_counter[8];
};

15
src/ap/ieee802_1x.c
View file

@ -157,6 +157,21 @@ static void ieee802_1x_tx_key_one(struct hostapd_data *hapd,
key->type = EAPOL_KEY_TYPE_RC4;
WPA_PUT_BE16(key->key_length, key_len);
wpa_get_ntp_timestamp(key->replay_counter);
if (os_memcmp(key->replay_counter,
hapd->last_1x_eapol_key_replay_counter,
IEEE8021X_REPLAY_COUNTER_LEN) <= 0) {
/* NTP timestamp did not increment from last EAPOL-Key frame;
* use previously used value + 1 instead. */
inc_byte_array(hapd->last_1x_eapol_key_replay_counter,
IEEE8021X_REPLAY_COUNTER_LEN);
os_memcpy(key->replay_counter,
hapd->last_1x_eapol_key_replay_counter,
IEEE8021X_REPLAY_COUNTER_LEN);
} else {
os_memcpy(hapd->last_1x_eapol_key_replay_counter,
key->replay_counter,
IEEE8021X_REPLAY_COUNTER_LEN);
}
if (random_get_bytes(key->key_iv, sizeof(key->key_iv))) {
wpa_printf(MSG_ERROR, "Could not get random numbers");