mac80211: allow same PN for AMSDU sub-frames

BugLink: http://bugs.launchpad.net/bugs/1774173

commit f631a77b upstream.

Some hardware (iwlwifi an example) de-aggregate AMSDUs and copy the IV
as is to the generated MPDUs, so the same PN appears in multiple
packets without being a replay attack.  Allow driver to explicitly
indicate that a frame is allowed to have the same PN as the previous
frame.
Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Cc: Sriram R <srirrama@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

include/net/mac80211.h

@@ -1031,6 +1031,9 @@ ieee80211_tx_info_clear_status(struct ieee80211_tx_info *info)
  * @RX_FLAG_RADIOTAP_VENDOR_DATA: This frame contains vendor-specific
  *	radiotap data in the skb->data (before the frame) as described by
  *	the &struct ieee80211_vendor_radiotap.
+ * @RX_FLAG_ALLOW_SAME_PN: Allow the same PN as same packet before.
+ *	This is used for AMSDU subframes which can have the same PN as
+ *	the first subframe.
  */
 enum mac80211_rx_flags {
 	RX_FLAG_MMIC_ERROR		= BIT(0),
@@ -1061,7 +1064,8 @@ enum mac80211_rx_flags {
 	RX_FLAG_5MHZ			= BIT(29),
 	RX_FLAG_AMSDU_MORE		= BIT(30),
 	RX_FLAG_RADIOTAP_VENDOR_DATA	= BIT(31),
-	RX_FLAG_MIC_STRIPPED            = BIT_ULL(32),
+	RX_FLAG_MIC_STRIPPED		= BIT_ULL(32),
+	RX_FLAG_ALLOW_SAME_PN		= BIT_ULL(33),
 };
 
 #define RX_FLAG_STBC_SHIFT		26

net/mac80211/wpa.c

@@ -523,12 +523,16 @@ ieee80211_crypto_ccmp_decrypt(struct ieee80211_rx_data *rx,
 		return RX_DROP_UNUSABLE;
 
 	if (!(status->flag & RX_FLAG_PN_VALIDATED)) {
+		int res;
+
 		ccmp_hdr2pn(pn, skb->data + hdrlen);
 
 		queue = rx->security_idx;
 
-		if (memcmp(pn, key->u.ccmp.rx_pn[queue],
-			   IEEE80211_CCMP_PN_LEN) <= 0) {
+		res = memcmp(pn, key->u.ccmp.rx_pn[queue],
+			     IEEE80211_CCMP_PN_LEN);
+		if (res < 0 ||
+		    (!res && !(status->flag & RX_FLAG_ALLOW_SAME_PN))) {
 			key->u.ccmp.replays++;
 			return RX_DROP_UNUSABLE;
 		}
@@ -749,12 +753,16 @@ ieee80211_crypto_gcmp_decrypt(struct ieee80211_rx_data *rx)
 		return RX_DROP_UNUSABLE;
 
 	if (!(status->flag & RX_FLAG_PN_VALIDATED)) {
+		int res;
+
 		gcmp_hdr2pn(pn, skb->data + hdrlen);
 
 		queue = rx->security_idx;
 
-		if (memcmp(pn, key->u.gcmp.rx_pn[queue],
-			   IEEE80211_GCMP_PN_LEN) <= 0) {
+		res = memcmp(pn, key->u.gcmp.rx_pn[queue],
+			     IEEE80211_GCMP_PN_LEN);
+		if (res < 0 ||
+		    (!res && !(status->flag & RX_FLAG_ALLOW_SAME_PN))) {
 			key->u.gcmp.replays++;
 			return RX_DROP_UNUSABLE;
 		}