mac80211: 802.11w - Optional software CCMP for management frames

If driver/firmware/hardware does not support CCMP for management
frames, it can now request mac80211 to take care of encrypting and
decrypting management frames (when MFP is enabled) in software. The
will need to add this new IEEE80211_KEY_FLAG_SW_MGMT flag when a CCMP
key is being configured for TX side and return the undecrypted frames
on RX side without RX_FLAG_DECRYPTED flag to use software CCMP for
management frames (but hardware for data frames).
Signed-off-by: Jouni Malinen <jouni.malinen@atheros.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/net/mac80211.h

@@ -686,12 +686,16 @@ enum ieee80211_key_len {
  *	generation in software.
  * @IEEE80211_KEY_FLAG_PAIRWISE: Set by mac80211, this flag indicates
  *	that the key is pairwise rather then a shared key.
+ * @IEEE80211_KEY_FLAG_SW_MGMT: This flag should be set by the driver for a
+ *	CCMP key if it requires CCMP encryption of management frames (MFP) to
+ *	be done in software.
  */
 enum ieee80211_key_flags {
 	IEEE80211_KEY_FLAG_WMM_STA	= 1<<0,
 	IEEE80211_KEY_FLAG_GENERATE_IV	= 1<<1,
 	IEEE80211_KEY_FLAG_GENERATE_MMIC= 1<<2,
 	IEEE80211_KEY_FLAG_PAIRWISE	= 1<<3,
+	IEEE80211_KEY_FLAG_SW_MGMT	= 1<<4,
 };
 
 /**

net/mac80211/wpa.c

@@ -367,9 +367,14 @@ static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 	int hdrlen, len, tail;
 	u8 *pos, *pn;
 	int i;
+	bool skip_hw;
+
+	skip_hw = (tx->key->conf.flags & IEEE80211_KEY_FLAG_SW_MGMT) &&
+		ieee80211_is_mgmt(hdr->frame_control);
 
 	if ((tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) &&
-	    !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV)) {
+	    !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV) &&
+	    !skip_hw) {
 		/* hwaccel - with no need for preallocated room for CCMP
 		 * header or MIC fields */
 		info->control.hw_key = &tx->key->conf;
@@ -404,7 +409,7 @@ static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 
 	ccmp_pn2hdr(pos, pn, key->conf.keyidx);
 
-	if (key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) {
+	if ((key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) && !skip_hw) {
 		/* hwaccel - with preallocated room for CCMP header */
 		info->control.hw_key = &tx->key->conf;
 		return 0;