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mac80211: Beacon protection using the new BIGTK (STA) 

This adds support for mac80211 to verify that received Beacon frames
have a valid MME in station mode when a BIGTK is configured.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Link: https://lore.kernel.org/r/20200222132548.20835-6-jouni@codeaurora.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Jouni Malinen 2020-02-22 15:25:47 +02:00 committed by Johannes Berg
parent 0a3a84360b
commit af2d14b01c
1 changed files with 67 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

79
net/mac80211/rx.c
View File

@ -983,7 +983,8 @@ static int ieee80211_get_mmie_keyidx(struct sk_buff *skb)
if (skb->len < 24 + sizeof(*mmie) || !is_multicast_ether_addr(hdr->da))
return -1;
if (!ieee80211_is_robust_mgmt_frame(skb))
if (!ieee80211_is_robust_mgmt_frame(skb) &&
!ieee80211_is_beacon(hdr->frame_control))
return -1; /* not a robust management frame */
mmie = (struct ieee80211_mmie *)
@ -1868,6 +1869,41 @@ ieee80211_rx_h_sta_process(struct ieee80211_rx_data *rx)
return RX_CONTINUE;
} /* ieee80211_rx_h_sta_process */
static struct ieee80211_key *
ieee80211_rx_get_bigtk(struct ieee80211_rx_data *rx, int idx)
{
struct ieee80211_key *key = NULL;
struct ieee80211_sub_if_data *sdata = rx->sdata;
int idx2;
/* Make sure key gets set if either BIGTK key index is set so that
* ieee80211_drop_unencrypted_mgmt() can properly drop both unprotected
* Beacon frames and Beacon frames that claim to use another BIGTK key
* index (i.e., a key that we do not have).
*/
if (idx < 0) {
idx = NUM_DEFAULT_KEYS + NUM_DEFAULT_MGMT_KEYS;
idx2 = idx + 1;
} else {
if (idx == NUM_DEFAULT_KEYS + NUM_DEFAULT_MGMT_KEYS)
idx2 = idx + 1;
else
idx2 = idx - 1;
}
if (rx->sta)
key = rcu_dereference(rx->sta->gtk[idx]);
if (!key)
key = rcu_dereference(sdata->keys[idx]);
if (!key && rx->sta)
key = rcu_dereference(rx->sta->gtk[idx2]);
if (!key)
key = rcu_dereference(sdata->keys[idx2]);
return key;
}
static ieee80211_rx_result debug_noinline
ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
{
@ -1885,17 +1921,18 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
/*
* Key selection 101
*
* There are four types of keys:
* There are five types of keys:
* - GTK (group keys)
* - IGTK (group keys for management frames)
* - BIGTK (group keys for Beacon frames)
* - PTK (pairwise keys)
* - STK (station-to-station pairwise keys)
*
* When selecting a key, we have to distinguish between multicast
* (including broadcast) and unicast frames, the latter can only
* use PTKs and STKs while the former always use GTKs and IGTKs.
* Unless, of course, actual WEP keys ("pre-RSNA") are used, then
* unicast frames can also use key indices like GTKs. Hence, if we
* use PTKs and STKs while the former always use GTKs, IGTKs, and
* BIGTKs. Unless, of course, actual WEP keys ("pre-RSNA") are used,
* then unicast frames can also use key indices like GTKs. Hence, if we
* don't have a PTK/STK we check the key index for a WEP key.
*
* Note that in a regular BSS, multicast frames are sent by the
@ -1939,6 +1976,20 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
/* Skip decryption if the frame is not protected. */
if (!ieee80211_has_protected(fc))
return RX_CONTINUE;
} else if (mmie_keyidx >= 0 && ieee80211_is_beacon(fc)) {
/* Broadcast/multicast robust management frame / BIP */
if ((status->flag & RX_FLAG_DECRYPTED) &&
(status->flag & RX_FLAG_IV_STRIPPED))
return RX_CONTINUE;
if (mmie_keyidx < NUM_DEFAULT_KEYS + NUM_DEFAULT_MGMT_KEYS ||
mmie_keyidx >= NUM_DEFAULT_KEYS + NUM_DEFAULT_MGMT_KEYS +
NUM_DEFAULT_BEACON_KEYS)
return RX_DROP_MONITOR; /* unexpected BIP keyidx */
rx->key = ieee80211_rx_get_bigtk(rx, mmie_keyidx);
if (!rx->key)
return RX_CONTINUE; /* Beacon protection not in use */
} else if (mmie_keyidx >= 0) {
/* Broadcast/multicast robust management frame / BIP */
if ((status->flag & RX_FLAG_DECRYPTED) &&
@ -1968,11 +2019,12 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
struct ieee80211_sub_if_data *sdata = rx->sdata;
int i;
if (ieee80211_is_mgmt(fc) &&
is_multicast_ether_addr(hdr->addr1) &&
(key = rcu_dereference(rx->sdata->default_mgmt_key)))
rx->key = key;
else {
if (ieee80211_is_beacon(fc)) {
key = ieee80211_rx_get_bigtk(rx, -1);
} else if (ieee80211_is_mgmt(fc) &&
is_multicast_ether_addr(hdr->addr1)) {
key = rcu_dereference(rx->sdata->default_mgmt_key);
} else {
if (rx->sta) {
for (i = 0; i < NUM_DEFAULT_KEYS; i++) {
key = rcu_dereference(rx->sta->gtk[i]);
@ -1987,9 +2039,9 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
break;
}
}
if (key)
rx->key = key;
}
if (key)
rx->key = key;
return RX_CONTINUE;
} else {
/*
@ -2358,6 +2410,9 @@ static int ieee80211_drop_unencrypted_mgmt(struct ieee80211_rx_data *rx)
rx->skb->len);
return -EACCES;
}
if (unlikely(ieee80211_is_beacon(fc) && rx->key &&
ieee80211_get_mmie_keyidx(rx->skb) < 0))
return -EACCES;
/*
* When using MFP, Action frames are not allowed prior to
* having configured keys.