mt76: validate rx CCMP PN

Apparently hardware does not perform CCMP PN validation in hardware, so
we need to take care of this in the driver. This is important for
protecting against replay attacks.

Since validation of fragmented frames is more complex, the CCMP header
for those is preserved. To keep the counter in sync, the first fragment
is verified by both mt76 and mac80211, and all other fragments only by
mac80211.
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

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

@@ -384,6 +384,27 @@ int mt76_get_survey(struct ieee80211_hw *hw, int idx,
 }
 EXPORT_SYMBOL_GPL(mt76_get_survey);
 
+void mt76_wcid_key_setup(struct mt76_dev *dev, struct mt76_wcid *wcid,
+			 struct ieee80211_key_conf *key)
+{
+	struct ieee80211_key_seq seq;
+	int i;
+
+	wcid->rx_check_pn = false;
+
+	if (!key)
+		return;
+
+	if (key->cipher == WLAN_CIPHER_SUITE_CCMP)
+		wcid->rx_check_pn = true;
+
+	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));
+	}
+}
+EXPORT_SYMBOL(mt76_wcid_key_setup);
+
 static struct ieee80211_sta *mt76_rx_convert(struct sk_buff *skb)
 {
 	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
@@ -410,6 +431,45 @@ static struct ieee80211_sta *mt76_rx_convert(struct sk_buff *skb)
 	return wcid_to_sta(mstat.wcid);
 }
 
+static int
+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;
+	int ret;
+
+	if (!(status->flag & RX_FLAG_DECRYPTED))
+		return 0;
+
+	if (!wcid || !wcid->rx_check_pn)
+		return 0;
+
+	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 = (struct ieee80211_hdr *) skb->data;
+		if (ieee80211_is_frag(hdr) &&
+		    !ieee80211_is_first_frag(hdr->frame_control))
+			return 0;
+	}
+
+	BUILD_BUG_ON(sizeof(status->iv) != sizeof(wcid->rx_key_pn[0]));
+	ret = memcmp(status->iv, wcid->rx_key_pn[status->tid],
+		     sizeof(status->iv));
+	if (ret <= 0)
+		return -EINVAL; /* replay */
+
+	memcpy(wcid->rx_key_pn[status->tid], status->iv, sizeof(status->iv));
+
+	if (status->flag & RX_FLAG_IV_STRIPPED)
+		status->flag |= RX_FLAG_PN_VALIDATED;
+
+	return 0;
+}
+
 void mt76_rx_complete(struct mt76_dev *dev, struct sk_buff_head *frames,
 		      int queue)
 {
@@ -421,6 +481,11 @@ void mt76_rx_complete(struct mt76_dev *dev, struct sk_buff_head *frames,
 	    napi = &dev->napi[queue];
 
 	while ((skb = __skb_dequeue(frames)) != NULL) {
+		if (mt76_check_ccmp_pn(skb)) {
+			dev_kfree_skb(skb);
+			continue;
+		}
+
 		sta = mt76_rx_convert(skb);
 		ieee80211_rx_napi(dev->hw, sta, skb, napi);
 	}

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

@@ -131,6 +131,9 @@ struct mt76_wcid {
 
 	u8 sta:1;
 
+	u8 rx_check_pn;
+	u8 rx_key_pn[IEEE80211_NUM_TIDS][6];
+
 	__le16 tx_rate;
 	bool tx_rate_set;
 	u8 tx_rate_nss;
@@ -279,12 +282,14 @@ struct mt76_rx_status {
 
 	unsigned long reorder_time;
 
-	u8 aggr;
+	u8 iv[6];
+
+	u8 aggr:1;
 	u8 tid;
 	u16 seqno;
 
-	u32 flag;
 	u16 freq;
+	u32 flag;
 	u8 enc_flags;
 	u8 encoding:2, bw:3;
 	u8 rate_idx;
@@ -413,6 +418,9 @@ int mt76_rx_aggr_start(struct mt76_dev *dev, struct mt76_wcid *wcid, u8 tid,
 		       u16 ssn, u8 size);
 void mt76_rx_aggr_stop(struct mt76_dev *dev, struct mt76_wcid *wcid, u8 tid);
 
+void mt76_wcid_key_setup(struct mt76_dev *dev, struct mt76_wcid *wcid,
+			 struct ieee80211_key_conf *key);
+
 /* internal */
 void mt76_tx_free(struct mt76_dev *dev);
 void mt76_put_txwi(struct mt76_dev *dev, struct mt76_txwi_cache *t);

drivers/net/wireless/mediatek/mt76/mt76x2_init.c

@@ -131,7 +131,7 @@ mt76_write_mac_initvals(struct mt76x2_dev *dev)
 		{ MT_RX_FILTR_CFG,		0x00015f97 },
 		{ MT_LEGACY_BASIC_RATE,		0x0000017f },
 		{ MT_HT_BASIC_RATE,		0x00004003 },
-		{ MT_PN_PAD_MODE,		0x00000002 },
+		{ MT_PN_PAD_MODE,		0x00000003 },
 		{ MT_TXOP_HLDR_ET,		0x00000002 },
 		{ 0xa44,			0x00000000 },
 		{ MT_HEADER_TRANS_CTRL_REG,	0x00000000 },

drivers/net/wireless/mediatek/mt76/mt76x2_mac.c

@@ -257,12 +257,16 @@ void mt76x2_mac_write_txwi(struct mt76x2_dev *dev, struct mt76x2_txwi *txwi,
 	txwi->len_ctl = cpu_to_le16(skb->len);
 }
 
-static void mt76x2_remove_hdr_pad(struct sk_buff *skb)
+static void mt76x2_remove_hdr_pad(struct sk_buff *skb, int len)
 {
-	int len = ieee80211_get_hdrlen_from_skb(skb);
+	int hdrlen;
 
-	memmove(skb->data + 2, skb->data, len);
-	skb_pull(skb, 2);
+	if (!len)
+		return;
+
+	hdrlen = ieee80211_get_hdrlen_from_skb(skb);
+	memmove(skb->data + len, skb->data, hdrlen);
+	skb_pull(skb, len);
 }
 
 static struct mt76_wcid *
@@ -287,28 +291,59 @@ int mt76x2_mac_process_rx(struct mt76x2_dev *dev, struct sk_buff *skb,
 {
 	struct mt76_rx_status *status = (struct mt76_rx_status *) skb->cb;
 	struct mt76x2_rxwi *rxwi = rxi;
+	u32 rxinfo = le32_to_cpu(rxwi->rxinfo);
 	u32 ctl = le32_to_cpu(rxwi->ctl);
 	u16 rate = le16_to_cpu(rxwi->rate);
 	u16 tid_sn = le16_to_cpu(rxwi->tid_sn);
 	bool unicast = rxwi->rxinfo & cpu_to_le32(MT_RXINFO_UNICAST);
+	int pad_len = 0;
+	u8 pn_len;
 	u8 wcid;
 	int len;
 
+	if (rxinfo & MT_RXINFO_L2PAD)
+		pad_len += 2;
+
+	if (rxinfo & MT_RXINFO_DECRYPT) {
+		status->flag |= RX_FLAG_DECRYPTED;
+		status->flag |= RX_FLAG_MMIC_STRIPPED;
+		status->flag |= RX_FLAG_MIC_STRIPPED;
+		status->flag |= RX_FLAG_IV_STRIPPED;
+	}
+
 	wcid = FIELD_GET(MT_RXWI_CTL_WCID, ctl);
 	status->wcid = mt76x2_rx_get_sta_wcid(dev, wcid, unicast);
 
-	if (rxwi->rxinfo & cpu_to_le32(MT_RXINFO_L2PAD))
-		mt76x2_remove_hdr_pad(skb);
+	len = FIELD_GET(MT_RXWI_CTL_MPDU_LEN, ctl);
+	pn_len = FIELD_GET(MT_RXINFO_PN_LEN, rxinfo);
+	if (pn_len) {
+		int offset = ieee80211_get_hdrlen_from_skb(skb) + pad_len;
+		u8 *data = skb->data + offset;
+
+		status->iv[0] = data[7];
+		status->iv[1] = data[6];
+		status->iv[2] = data[5];
+		status->iv[3] = data[4];
+		status->iv[4] = data[1];
+		status->iv[5] = data[0];
+
+		/*
+		 * Driver CCMP validation can't deal with fragments.
+		 * Let mac80211 take care of it.
+		 */
+		if (rxinfo & MT_RXINFO_FRAG) {
+			status->flag &= ~RX_FLAG_IV_STRIPPED;
+		} else {
+			pad_len += pn_len << 2;
+			len -= pn_len << 2;
+		}
+	}
+
+	mt76x2_remove_hdr_pad(skb, pad_len);
 
-	if (rxwi->rxinfo & cpu_to_le32(MT_RXINFO_BA))
+	if (rxinfo & MT_RXINFO_BA)
 		status->aggr = true;
 
-	if (rxwi->rxinfo & cpu_to_le32(MT_RXINFO_DECRYPT)) {
-		status->flag |= RX_FLAG_DECRYPTED;
-		status->flag |= RX_FLAG_IV_STRIPPED | RX_FLAG_MMIC_STRIPPED;
-	}
-
-	len = FIELD_GET(MT_RXWI_CTL_MPDU_LEN, ctl);
 	if (WARN_ON_ONCE(len > skb->len))
 		return -EINVAL;
 

drivers/net/wireless/mediatek/mt76/mt76x2_main.c

@@ -371,6 +371,7 @@ mt76x2_set_key(struct ieee80211_hw *hw, enum set_key_cmd cmd,
 
 		key = NULL;
 	}
+	mt76_wcid_key_setup(&dev->mt76, wcid, key);
 
 	if (!msta) {
 		if (key || wcid->hw_key_idx == idx) {