mt76: use a separate CCMP PN receive counter for management frames

When received frame is decryped by hardware, CCMP PN is checked by
mt76.

When management frame protection (IEEE 802.11w) is used, we must use
a separate counter for tracking received CCMP packet number for the
management frames. The previously used counter was shared with data
frames and that can cause problems in detecting replays incorrectly
for robust management frames.

Add a new counter just for robust management frames to avoid this
issue.
Signed-off-by: Xing Song <xing.song@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mac80211.c

@@ -902,10 +902,17 @@ void mt76_wcid_key_setup(struct mt76_dev *dev, struct mt76_wcid *wcid,
 		return;
 
 	wcid->rx_check_pn = true;
+
+	/* data frame */
 	for (i = 0; i < IEEE80211_NUM_TIDS; i++) {
 		ieee80211_get_key_rx_seq(key, i, &seq);
 		memcpy(wcid->rx_key_pn[i], seq.ccmp.pn, sizeof(seq.ccmp.pn));
 	}
+
+	/* robust management frame */
+	ieee80211_get_key_rx_seq(key, -1, &seq);
+	memcpy(wcid->rx_key_pn[i], seq.ccmp.pn, sizeof(seq.ccmp.pn));
+
 }
 EXPORT_SYMBOL(mt76_wcid_key_setup);
 
@@ -958,7 +965,7 @@ mt76_check_ccmp_pn(struct sk_buff *skb)
 	struct mt76_rx_status *status = (struct mt76_rx_status *)skb->cb;
 	struct mt76_wcid *wcid = status->wcid;
 	struct ieee80211_hdr *hdr;
-	u8 tidno = status->qos_ctl & IEEE80211_QOS_CTL_TID_MASK;
+	int security_idx;
 	int ret;
 
 	if (!(status->flag & RX_FLAG_DECRYPTED))
@@ -967,24 +974,36 @@ mt76_check_ccmp_pn(struct sk_buff *skb)
 	if (!wcid || !wcid->rx_check_pn)
 		return 0;
 
+	hdr = mt76_skb_get_hdr(skb);
 	if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
 		/*
 		 * Validate the first fragment both here and in mac80211
 		 * All further fragments will be validated by mac80211 only.
 		 */
-		hdr = mt76_skb_get_hdr(skb);
 		if (ieee80211_is_frag(hdr) &&
 		    !ieee80211_is_first_frag(hdr->frame_control))
 			return 0;
 	}
 
+	/* IEEE 802.11-2020, 12.5.3.4.4 "PN and replay detection" c):
+	 *
+	 * the recipient shall maintain a single replay counter for received
+	 * individually addressed robust Management frames that are received
+	 * with the To DS subfield equal to 0, [...]
+	 */
+	if (ieee80211_is_mgmt(hdr->frame_control) &&
+	    !ieee80211_has_tods(hdr->frame_control))
+		security_idx = IEEE80211_NUM_TIDS;
+	else
+		security_idx = status->qos_ctl & IEEE80211_QOS_CTL_TID_MASK;
+
 	BUILD_BUG_ON(sizeof(status->iv) != sizeof(wcid->rx_key_pn[0]));
-	ret = memcmp(status->iv, wcid->rx_key_pn[tidno],
+	ret = memcmp(status->iv, wcid->rx_key_pn[security_idx],
 		     sizeof(status->iv));
 	if (ret <= 0)
 		return -EINVAL; /* replay */
 
-	memcpy(wcid->rx_key_pn[tidno], status->iv, sizeof(status->iv));
+	memcpy(wcid->rx_key_pn[security_idx], status->iv, sizeof(status->iv));
 
 	if (status->flag & RX_FLAG_IV_STRIPPED)
 		status->flag |= RX_FLAG_PN_VALIDATED;

drivers/net/wireless/mediatek/mt76/mt76.h

@@ -255,7 +255,7 @@ struct mt76_wcid {
 	u8 amsdu:1;
 
 	u8 rx_check_pn;
-	u8 rx_key_pn[IEEE80211_NUM_TIDS][6];
+	u8 rx_key_pn[IEEE80211_NUM_TIDS + 1][6];
 	u16 cipher;
 
 	u32 tx_info;